Clinical application of arterial spin-labeling MR imaging in patients with carotid stenosis: quantitative comparative study with single-photon emission CT.

PubMed

Uchihashi, Y; Hosoda, K; Zimine, I; Fujita, A; Fujii, M; Sugimura, K; Kohmura, E

2011-09-01

Arterial spin-labeling is an emerging technique for noninvasive measurement of cerebral perfusion, but concerns remain regarding the reliability of CBF quantification and clinical applications. Recently, an ASL implementation called QUASAR was proposed, and it was shown to have good reproducibility of CBF assessment in healthy volunteers. This study aimed to determine the utility of QUASAR for CBF assessment in patients with cerebrovascular diseases. Twenty patients with carotid stenosis underwent CBF quantification by ASL (QUASAR) within 3 days of performance of (123)I-iodoamphetamine-SPECT. CVR to acetazolamide also was assessed by ASL and SPECT. In surgically treated patients, the respective scans before and after the procedures were compared. Regional CBF and CVR values measured by ASL were significantly correlated and agreed with those measured by SPECT (r(s) = 0.92 and 0.88, respectively). A Bland-Altman plot demonstrated good agreement between 2 methods in terms of CBF quantification. Furthermore, ASL could detect pathologic states such as hypoperfusion, impaired vasoreactivity, and postoperative hyperperfusion, equivalent to SPECT. However, ASL tended to overestimate CBF values especially in high-perfusion regions. ASL perfusion MR imaging is clinically applicable and can be an alternative method for CBF assessment in patients with cerebrovascular diseases.

Positron emission tomography/magnetic resonance hybrid scanner imaging of cerebral blood flow using 15O-water positron emission tomography and arterial spin labeling magnetic resonance imaging in newborn piglets

PubMed Central

Andersen, Julie B; Henning, William S; Lindberg, Ulrich; Ladefoged, Claes N; Højgaard, Liselotte; Greisen, Gorm; Law, Ian

2015-01-01

Abnormality in cerebral blood flow (CBF) distribution can lead to hypoxic–ischemic cerebral damage in newborn infants. The aim of the study was to investigate minimally invasive approaches to measure CBF by comparing simultaneous 15O-water positron emission tomography (PET) and single TI pulsed arterial spin labeling (ASL) magnetic resonance imaging (MR) on a hybrid PET/MR in seven newborn piglets. Positron emission tomography was performed with IV injections of 20 MBq and 100 MBq 15O-water to confirm CBF reliability at low activity. Cerebral blood flow was quantified using a one-tissue-compartment-model using two input functions: an arterial input function (AIF) or an image-derived input function (IDIF). The mean global CBF (95% CI) PET-AIF, PET-IDIF, and ASL at baseline were 27 (23; 32), 34 (31; 37), and 27 (22; 32) mL/100 g per minute, respectively. At acetazolamide stimulus, PET-AIF, PET-IDIF, and ASL were 64 (55; 74), 76 (70; 83) and 79 (67; 92) mL/100 g per minute, respectively. At baseline, differences between PET-AIF, PET-IDIF, and ASL were 22% (P<0.0001) and −0.7% (P=0.9). At acetazolamide, differences between PET-AIF, PET-IDIF, and ASL were 19% (P=0.001) and 24% (P=0.0003). In conclusion, PET-IDIF overestimated CBF. Injected activity of 20 MBq 15O-water had acceptable concordance with 100 MBq, without compromising image quality. Single TI ASL was questionable for regional CBF measurements. Global ASL CBF and PET CBF were congruent during baseline but not during hyperperfusion. PMID:26058699

Adjustable shunt valve-induced magnetic resonance imaging artifact: a comparative study.

PubMed

Toma, Ahmed K; Tarnaris, Andrew; Grieve, Joan P; Watkins, Laurence D; Kitchen, Neil D

2010-07-01

In this paper, the authors' goal was to compare the artifact induced by implanted (in vivo) adjustable shunt valves in spin echo, diffusion weighted (DW), and gradient echo MR imaging pulse sequences. The MR images obtained in 8 patients with proGAV and 6 patients with Strata II adjustable shunt valves were assessed for artifact areas in different planes as well as the total volume for different pulse sequences. Artifacts induced by the Strata II valve were significantly larger than those induced by proGAV valve in spin echo MR imaging pulse sequence (29,761 vs 2450 mm(3) on T2-weighted fast spin echo, p = 0.003) and DW images (100,138 vs 38,955 mm(3), p = 0.025). Artifacts were more marked on DW MR images than on spin echo pulse sequence for both valve types. Adjustable valve-induced artifacts can conceal brain pathology on MR images. This should influence the choice of valve implantation site and the type of valve used. The effect of artifacts on DW images should be highlighted pending the development of less MR imaging artifact-inducing adjustable shunt valves.

Vertigo-related cerebral blood flow changes on magnetic resonance imaging.

PubMed

Chang, Feiyan; Li, Zhongshi; Xie, Sheng; Liu, Hui; Wang, Wu

2014-11-01

A prospective study using magnetic resonance imaging on a consecutive cohort of patients with cervical vertigo. To quantitatively investigate the cerebral blood flow (CBF) changes associated with cervical vertigo by using 3-dimensional pseudocontinuous arterial spin labeling. Previous studies reported blood flow velocity reduction in posterior circulation during vertigo. However, the detailed information of CBF related to cervical vertigo has not been provided. A total of 33 patients with cervical vertigo and 14 healthy volunteers were recruited in this study. Three-dimensional pseudocontinuous arterial spin labeling was performed on each subject to evaluate the CBF before and after the cervical hyperextension-hyperflexion movement tests, which was used to induce cervical vertigo. Repeated-measures analysis of variance was conducted to assess the effect of subjects and tests. There were time effects of CBF in the territory of bilateral superior cerebellar artery, bilateral posterior cerebral artery, bilateral middle cerebral artery, and right anterior cerebral artery, but no group effect was observed. The analysis of CBF revealed a significant main effect of tests (P=0.024) and participants (P=0.038) in the dorsal pons. Cervical vertigo onset may be related to CBF reduction in the dorsal pons, which sequentially evokes the vestibular nuclei. 2.

Associations of resting-state fMRI functional connectivity with flow-BOLD coupling and regional vasculature.

PubMed

Tak, Sungho; Polimeni, Jonathan R; Wang, Danny J J; Yan, Lirong; Chen, J Jean

2015-04-01

There has been tremendous interest in applying functional magnetic resonance imaging-based resting-state functional connectivity (rs-fcMRI) measurements to the study of brain function. However, a lack of understanding of the physiological mechanisms of rs-fcMRI limits their ability to interpret rs-fcMRI findings. In this work, the authors examine the regional associations between rs-fcMRI estimates and dynamic coupling between the blood oxygenation level-dependent (BOLD) and cerebral blood flow (CBF), as well as resting macrovascular volume. Resting-state BOLD and CBF data were simultaneously acquired using a dual-echo pseudocontinuous arterial spin labeling (pCASL) technique, whereas macrovascular volume fraction was estimated using time-of-flight MR angiography. Functional connectivity within well-known functional networks—including the default mode, frontoparietal, and primary sensory-motor networks—was calculated using a conventional seed-based correlation approach. They found the functional connectivity strength to be significantly correlated with the regional increase in CBF-BOLD coupling strength and inversely proportional to macrovascular volume fraction. These relationships were consistently observed within all functional networks considered. Their findings suggest that highly connected networks observed using rs-fcMRI are not likely to be mediated by common vascular drainage linking distal cortical areas. Instead, high BOLD functional connectivity is more likely to reflect tighter neurovascular connections, attributable to neuronal pathways.

Rapid Gradient-Echo Imaging

PubMed Central

Hargreaves, Brian

2012-01-01

Gradient echo sequences are widely used in magnetic resonance imaging (MRI) for numerous applications ranging from angiography to perfusion to functional MRI. Compared with spin-echo techniques, the very short repetition times of gradient-echo methods enable very rapid 2D and 3D imaging, but also lead to complicated “steady states.” Signal and contrast behavior can be described graphically and mathematically, and depends strongly on the type of spoiling: fully balanced (no spoiling), gradient spoiling, or RF-spoiling. These spoiling options trade off between high signal and pure T1 contrast while the flip angle also affects image contrast in all cases, both of which can be demonstrated theoretically and in image examples. As with spin-echo sequences, magnetization preparation can be added to gradient-echo sequences to alter image contrast. Gradient echo sequences are widely used for numerous applications such as 3D perfusion imaging, functional MRI, cardiac imaging and MR angiography. PMID:23097185

Isotropic 3-D T2-weighted spin-echo for abdominal and pelvic MRI in children.

PubMed

Dias, Sílvia Costa; Ølsen, Oystein E

2012-11-01

MRI has a fundamental role in paediatric imaging. The T2-weighted fast/turbo spin-echo sequence is important because it has high signal-to-noise ratio compared to gradient-echo sequences. It is usually acquired as 2-D sections in one or more planes. Volumetric spin-echo has until recently only been possible with very long echo times due to blurring of the soft-tissue contrast with long echo trains. A new 3-D spin-echo sequence uses variable flip angles to overcome this problem. It may reproduce useful soft-tissue contrast, with improved spatial resolution. Its isotropic capability allows subsequent reconstruction in standard, curved or arbitrary planes. It may be particularly useful for visualisation of small lesions, or if large lesions distort the usual anatomical relations. We present clinical examples, describe the technical parameters and discuss some potential artefacts and optimisation of image quality.

Value of a single-shot turbo spin-echo pulse sequence for assessing the architecture of the subarachnoid space and the constitutive nature of cerebrospinal fluid.

PubMed

Pease, Anthony; Sullivan, Stacey; Olby, Natasha; Galano, Heather; Cerda-Gonzalez, Sophia; Robertson, Ian D; Gavin, Patrick; Thrall, Donald

2006-01-01

Three case history reports are presented to illustrate the value of the single-shot turbo spin-echo pulse sequence for assessment of the subarachnoid space. The use of the single-shot turbo spin-echo pulse sequence, which is a heavily T2-weighted sequence, allows for a rapid, noninvasive evaluation of the subarachnoid space by using the high signal from cerebrospinal fluid. This sequence can be completed in seconds rather than the several minutes required for a T2-fast spin-echo sequence. Unlike the standard T2-fast spin-echo sequence, a single-shot turbo spin-echo pulse sequence also provides qualitative information about the protein and the cellular content of the cerebrospinal fluid, such as in patients with inflammatory debris or hemorrhage in the cerebrospinal fluid. Although the resolution of the single-shot turbo spin-echo pulse sequence images is relatively poor compared with more conventional sequences, the qualitative information about the subarachnoid space and cerebrospinal fluid and the rapid acquisition time, make it a useful sequence to include in standard protocols of spinal magnetic resonance imaging.

3D GRASE PROPELLER: improved image acquisition technique for arterial spin labeling perfusion imaging.

PubMed

Tan, Huan; Hoge, W Scott; Hamilton, Craig A; Günther, Matthias; Kraft, Robert A

2011-07-01

Arterial spin labeling is a noninvasive technique that can quantitatively measure cerebral blood flow. While traditionally arterial spin labeling employs 2D echo planar imaging or spiral acquisition trajectories, single-shot 3D gradient echo and spin echo (GRASE) is gaining popularity in arterial spin labeling due to inherent signal-to-noise ratio advantage and spatial coverage. However, a major limitation of 3D GRASE is through-plane blurring caused by T(2) decay. A novel technique combining 3D GRASE and a periodically rotated overlapping parallel lines with enhanced reconstruction trajectory (PROPELLER) is presented to minimize through-plane blurring without sacrificing perfusion sensitivity or increasing total scan time. Full brain perfusion images were acquired at a 3 × 3 × 5 mm(3) nominal voxel size with pulsed arterial spin labeling preparation sequence. Data from five healthy subjects was acquired on a GE 1.5T scanner in less than 4 minutes per subject. While showing good agreement in cerebral blood flow quantification with 3D gradient echo and spin echo, 3D GRASE PROPELLER demonstrated reduced through-plane blurring, improved anatomical details, high repeatability and robustness against motion, making it suitable for routine clinical use. Copyright © 2011 Wiley-Liss, Inc.

Turboprop: improved PROPELLER imaging.

PubMed

Pipe, James G; Zwart, Nicholas

2006-02-01

A variant of periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) MRI, called turboprop, is introduced. This method employs an oscillating readout gradient during each spin echo of the echo train to collect more lines of data per echo train, which reduces the minimum scan time, motion-related artifact, and specific absorption rate (SAR) while increasing sampling efficiency. It can be applied to conventional fast spin-echo (FSE) imaging; however, this article emphasizes its application in diffusion-weighted imaging (DWI). The method is described and compared with conventional PROPELLER imaging, and clinical images collected with this PROPELLER variant are shown. Copyright 2006 Wiley-Liss, Inc.

Singleshot T1 Mapping using Simultaneous Acquisitions of Spin- and STimulated-Echo Planar Imaging (2D ss-SESTEPI)

PubMed Central

Shi, Xianfeng; Kim, Seong-Eun; Jeong, Eun-Kee

2011-01-01

The conventional stimulated-echo NMR sequence only measures the longitudinal component, while discarding the transverse component, after tipping up the prepared magnetization. This transverse magnetization can be used to measure a spin-echo, in addition to the stimulated-echo. 2D ss-SESTEPI is an EPI-based singleshot imaging technique that simultaneously acquires a spin-echo-planar image (SEPI) and a stimulated-echo-planar image (STEPI) after a single RF excitation. The magnitudes of SEPI and STEPI differ by T1 decay and diffusion weighting for perfect 90° RF, and thus can be used to rapidly measure T1. However, the spatial variation of B1 amplitude induces un-even splitting of the transverse magnetization for SEPI and STEPI within the imaging FOV. Correction for B1 inhomogeneity is therefore critical for 2D ss-SESTEPI to be used for T1 measurement. We developed a method for B1 inhomogeneity correction by acquiring an additional STEPI with minimal mixing time, calculating the difference between the spin-echo and the stimulated-echo and multiplying the STEPI by the inverse functional map. Diffusion-induced decay is corrected by measuring the average diffusivity during the prescanning. Rapid singleshot T1 mapping may be useful for various applications, such as dynamic T1 mapping for real-time estimation of the concentration of contrast agent in DCE-MRI. PMID:20564579

Characterizing Resting-State Brain Function Using Arterial Spin Labeling

PubMed Central

Jann, Kay; Wang, Danny J.J.

2015-01-01

Abstract Arterial spin labeling (ASL) is an increasingly established magnetic resonance imaging (MRI) technique that is finding broader applications in studying the healthy and diseased brain. This review addresses the use of ASL to assess brain function in the resting state. Following a brief technical description, we discuss the use of ASL in the following main categories: (1) resting-state functional connectivity (FC) measurement: the use of ASL-based cerebral blood flow (CBF) measurements as an alternative to the blood oxygen level-dependent (BOLD) technique to assess resting-state FC; (2) the link between network CBF and FC measurements: the use of network CBF as a surrogate of the metabolic activity within corresponding networks; and (3) the study of resting-state dynamic CBF-BOLD coupling and cerebral metabolism: the use of dynamic CBF information obtained using ASL to assess dynamic CBF-BOLD coupling and oxidative metabolism in the resting state. In addition, we summarize some future challenges and interesting research directions for ASL, including slice-accelerated (multiband) imaging as well as the effects of motion and other physiological confounds on perfusion-based FC measurement. In summary, this work reviews the state-of-the-art of ASL and establishes it as an increasingly viable MRI technique with high translational value in studying resting-state brain function. PMID:26106930

Effect of low refocusing angle in T1-weighted spin echo and fast spin echo MRI on low-contrast detectability: a comparative phantom study at 1.5 and 3 Tesla.

PubMed

Sarkar, Subhendra N; Mangosing, Jason L; Sarkar, Pooja R

2013-01-01

MRI tissue contrast is not well preserved at high field. In this work, we used a phantom with known, intrinsic contrast (3.6%) for model tissue pairs to test the effects of low angle refocusing pulses and magnetization transfer from adjacent slices on intrinsic contrast at 1.5 and 3 Tesla. Only T1-weighted spin echo sequences were tested since for such sequences the contrast loss, tissue heating, and image quality degradation at high fields seem to present significant diagnostic and quality issues. We hypothesized that the sources of contrast loss could be attributed to low refocusing angles that do not fulfill the Hahn spin echo conditions or to magnetization transfer effects from adjacent slices in multislice imaging. At 1.5 T the measured contrast was 3.6% for 180° refocusing pulses and 2% for 120° pulses, while at 3 T, it was 4% for 180° and only 1% for 120° refocusing pulses. There was no significant difference between single slice and multislice imaging suggesting little or no role played by magnetization transfer in the phantom chosen. Hence, one may conclude that low angle refocusing pulses not fulfilling the Hahn spin echo conditions are primarily responsible for significant deterioration of T1-weighted spin echo image contrast in high-field MRI.

Assessment of Alzheimer's disease risk with functional magnetic resonance imaging: an arterial spin labeling study.

PubMed

Bangen, Katherine J; Restom, Khaled; Liu, Thomas T; Wierenga, Christina E; Jak, Amy J; Salmon, David P; Bondi, Mark W

2012-01-01

Functional magnetic resonance imaging (fMRI) of older adults at risk for Alzheimer's disease (AD) by virtue of their cognitive (i.e., mild cognitive impairment [MCI]) and/or genetic (i.e., apolipoprotein E [APOE] ε4 allele) status demonstrate divergent brain response patterns during memory encoding across studies. Using arterial spin labeling MRI, we examined the influence of AD risk on resting cerebral blood flow (CBF) as well as the CBF and blood oxygenation level dependent (BOLD) signal response to memory encoding in the medial temporal lobes (MTL) in 45 older adults (29 cognitively normal [14 APOE ε4 carriers and 15 noncarriers]; 16 MCI [8 APOE ε4 carriers, 8 noncarriers]). Risk groups were comparable in terms of mean age, years of education, gender distribution, and vascular risk burden. Individuals at genetic risk for AD by virtue of the APOE ε4 allele demonstrated increased MTL resting state CBF relative to ε4 noncarriers, whereas individuals characterized as MCI showed decreased MTL resting state CBF relative to their cognitively normal peers. For percent change CBF, there was a trend toward a cognitive status by genotype interaction. In the cognitively normal group, there was no difference in percent change CBF based on APOE genotype. In contrast, in the MCI group, APOE ε4 carriers demonstrated significantly greater percent change in CBF relative to ε4 noncarriers. No group differences were found for BOLD response. Findings suggest that abnormal resting state CBF and CBF response to memory encoding may be early indicators of brain dysfunction in individuals at risk for developing AD.

Quantification of Load Dependent Brain Activity in Parametric N-Back Working Memory Tasks using Pseudo-continuous Arterial Spin Labeling (pCASL) Perfusion Imaging.

PubMed

Zou, Qihong; Gu, Hong; Wang, Danny J J; Gao, Jia-Hong; Yang, Yihong

2011-04-01

Brain activation and deactivation induced by N-back working memory tasks and their load effects have been extensively investigated using positron emission tomography (PET) and blood-oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI). However, the underlying mechanisms of BOLD fMRI are still not completely understood and PET imaging requires injection of radioactive tracers. In this study, a pseudo-continuous arterial spin labeling (pCASL) perfusion imaging technique was used to quantify cerebral blood flow (CBF), a well understood physiological index reflective of cerebral metabolism, in N-back working memory tasks. Using pCASL, we systematically investigated brain activation and deactivation induced by the N-back working memory tasks and further studied the load effects on brain activity based on quantitative CBF. Our data show increased CBF in the fronto-parietal cortices, thalamus, caudate, and cerebellar regions, and decreased CBF in the posterior cingulate cortex and medial prefrontal cortex, during the working memory tasks. Most of the activated/deactivated brain regions show an approximately linear relationship between CBF and task loads (0, 1, 2 and 3 back), although several regions show non-linear relationships (quadratic and cubic). The CBF-based spatial patterns of brain activation/deactivation and load effects from this study agree well with those obtained from BOLD fMRI and PET techniques. These results demonstrate the feasibility of ASL techniques to quantify human brain activity during high cognitive tasks, suggesting its potential application to assessing the mechanisms of cognitive deficits in neuropsychiatric and neurological disorders.

Contrast-enhanced T1-weighted fluid-attenuated inversion-recovery BLADE magnetic resonance imaging of the brain: an alternative to spin-echo technique for detection of brain lesions in the unsedated pediatric patient?

PubMed

Alibek, Sedat; Adamietz, Boris; Cavallaro, Alexander; Stemmer, Alto; Anders, Katharina; Kramer, Manuel; Bautz, Werner; Staatz, Gundula

2008-08-01

We compared contrast-enhanced T1-weighted magnetic resonance (MR) imaging of the brain using different types of data acquisition techniques: periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER, BLADE) imaging versus standard k-space sampling (conventional spin-echo pulse sequence) in the unsedated pediatric patient with focus on artifact reduction, overall image quality, and lesion detectability. Forty-eight pediatric patients (aged 3 months to 18 years) were scanned with a clinical 1.5-T whole body MR scanner. Cross-sectional contrast-enhanced T1-weighted spin-echo sequence was compared to a T1-weighted dark-fluid fluid-attenuated inversion-recovery (FLAIR) BLADE sequence for qualitative and quantitative criteria (image artifacts, image quality, lesion detectability) by two experienced radiologists. Imaging protocols were matched for imaging parameters. Reader agreement was assessed using the exact Bowker test. BLADE images showed significantly less pulsation and motion artifacts than the standard T1-weighted spin-echo sequence scan. BLADE images showed statistically significant lower signal-to-noise ratio but higher contrast-to-noise ratios with superior gray-white matter contrast. All lesions were demonstrated on FLAIR BLADE imaging, and one false-positive lesion was visible in spin-echo sequence images. BLADE MR imaging at 1.5 T is applicable for central nervous system imaging of the unsedated pediatric patient, reduces motion and pulsation artifacts, and minimizes the need for sedation or general anesthesia without loss of relevant diagnostic information.

Fluid-attenuated inversion recovery vascular hyperintensities in predicting cerebral hyperperfusion after intracranial arterial stenting.

PubMed

Wan, Chih-Cheng; Chen, David Yen-Ting; Tseng, Ying-Chi; Yan, Feng-Xian; Lee, Kun-Yu; Chiang, Chen-Hua; Chen, Chi-Jen

2017-08-01

No reliable imaging sign predicting cerebral hyperperfusion after intracranial arterial stenting (IAS) had been described in the literature. This study evaluated the effect of fluid-attenuated inversion recovery vascular hyperintensities (FVHs), also called hyperintense vessel sign on T2-weighted fluid-attenuated inversion recovery (T2-FLAIR) MR images, in predicting significant increase in cerebral blood flow (CBF) defined by arterial spin labeling (ASL) after IAS. We reviewed ASL CBF images and T2-FLAIR MR images before (D0), 1 day after (D1), and 3 days after (D3) IAS of 16 patients. T1-weighted MR images were used as cerebral maps for calculating CBF. The changes in CBF values after IAS were calculated in and compared among stenting and nonstenting vascular territories. An increase more than 50% of CBF was considered as hyperperfusion. The effect of FVHs in predicting hyperperfusion was calculated. The D1 CBF value was significantly higher than the D0 CBF value in stenting vascular, contralateral anterior cerebral artery, contralateral middle cerebral artery, and contralateral posterior cerebral artery (PCA) territories (all P < .05). The D1 and D3 CBF values were significantly higher than the D0 CBF value in overall vascular (P < .001), overall nonstenting vascular (P < .001), and ipsilateral PCA (P < .05) territories. The rate of more than 50% increases in CBF was significantly higher in patients who exhibited asymmetric FVHs than in those who did not exhibit these findings. FVHs could be a critical predictor of a significant increase in CBF after IAS.

Optimal MR Plaque Imaging for Cervical Carotid Artery Stenosis in Predicting the Development of Microembolic Signals during Exposure of Carotid Arteries in Endarterectomy: Comparison of 4 T1-Weighted Imaging Techniques.

PubMed

Sato, Y; Ogasawara, K; Narumi, S; Sasaki, M; Saito, A; Tsushima, E; Namba, T; Kobayashi, M; Yoshida, K; Terayama, Y; Ogawa, A

2016-06-01

Preoperative identification of plaque vulnerability may allow improved risk stratification for patients considered for carotid endarterectomy. The present study aimed to determine which plaque imaging technique, cardiac-gated black-blood fast spin-echo, magnetization-prepared rapid acquisition of gradient echo, source image of 3D time-of-flight MR angiography, or noncardiac-gated spin-echo, most accurately predicts development of microembolic signals during exposure of carotid arteries in carotid endarterectomy. Eighty patients with ICA stenosis (≥70%) underwent the 4 sequences of preoperative MR plaque imaging of the affected carotid bifurcation and then carotid endarterectomy under transcranial Doppler monitoring of microembolic signals in the ipsilateral middle cerebral artery. The contrast ratio of the carotid plaque was calculated by dividing plaque signal intensity by sternocleidomastoid muscle signal intensity. Microembolic signals during exposure of carotid arteries were detected in 23 patients (29%), 3 of whom developed new neurologic deficits postoperatively. Those deficits remained at 24 hours after surgery in only 1 patient. The area under the receiver operating characteristic curve to discriminate between the presence and absence of microembolic signals during exposure of the carotid arteries was significantly greater with nongated spin-echo than with black-blood fast spin-echo (difference between areas, 0.258; P < .0001), MPRAGE (difference between areas, 0.106; P = .0023), or source image of 3D time-of-flight MR angiography (difference between areas, 0.128; P = .0010). Negative binomial regression showed that in the 23 patients with microembolic signals, the contrast ratio was associated with the number of microembolic signals only in nongated spin-echo (risk ratio, 1.36; 95% confidence interval, 1.01-1.97; P < .001). Nongated spin-echo may predict the development of microembolic signals during exposure of the carotid arteries in carotid endarterectomy more accurately than other MR plaque imaging techniques. © 2016 by American Journal of Neuroradiology.

Quantification of regional cerebral blood flow and volume with dynamic susceptibility contrast-enhanced MR imaging.

PubMed

Rempp, K A; Brix, G; Wenz, F; Becker, C R; Gückel, F; Lorenz, W J

1994-12-01

Quantification of regional cerebral blood flow (rCBF) and volume (rCBV) with dynamic magnetic resonance (MR) imaging. After bolus administration of a paramagnetic contrast medium, rapid T2*-weighted gradient-echo images of two sections were acquired for the simultaneous creation of concentration-time curves in the brain-feeding arteries and in brain tissue. Absolute rCBF and rCBV values were determined for gray and white brain matter in 12 subjects with use of principles of the indicator dilution theory. The mean rCBF value in gray matter was 69.7 mL/min +/- 29.7 per 100 g tissue and in white matter, 33.6 mL/min +/- 11.5 per 100 g tissue; the average rCBV was 8.0 mL +/- 3.1 per 100 g tissue and 4.2 mL +/- 1.0 per 100 g tissue, respectively. An age-related decrease in rCBF and rCBV for gray and white matter was observed. Preliminary data demonstrate that the proposed technique allows the quantification of rCBF and rCBV. Although the results are in good agreement with data from positron emission tomography studies, further evaluation is needed to establish the validity of method.

Cerebral blood flow measured by arterial spin labeling MRI at resting state in normal aging and Alzheimer's disease.

PubMed

Zhang, Nan; Gordon, Marc L; Goldberg, Terry E

2017-01-01

Arterial spin labeling (ASL) magnetic resonance imaging uses arterial blood water as an endogenous tracer to measure cerebral blood flow (CBF). In this review, based on ASL studies in the resting state, we discuss state-of-the-art technical and data processing improvements in ASL, and ASL CBF changes in normal aging, mild cognitive impairment (MCI), Alzheimer's disease (AD), and other types of dementia. We propose that vascular and AD risk factors should be considered when evaluating CBF changes in aging, and that other validated biomarkers should be used as inclusion criteria or covariates when evaluating CBF changes in MCI and AD. With improvements in hardware and experimental design, ASL is proving to be an increasingly promising tool for exploring pathogenetic mechanisms, early detection, monitoring disease progression and pharmacological response, and differential diagnosis of AD. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Neurovascular unit impairment in early Alzheimer's disease measured with magnetic resonance imaging.

PubMed

van de Haar, Harm J; Jansen, Jacobus F A; van Osch, Matthias J P; van Buchem, Mark A; Muller, Majon; Wong, Sau May; Hofman, Paul A M; Burgmans, Saartje; Verhey, Frans R J; Backes, Walter H

2016-09-01

The neurovascular unit, which protects neuronal cells and supplies them with essential molecules, plays an important role in the pathophysiology of Alzheimer's Disease (AD). The aim of this study was to noninvasively investigate 2 linked functional elements of the neurovascular unit, blood-brain barrier (BBB) permeability and cerebral blood flow (CBF), in patients with early AD and healthy controls. Therefore, both dynamic contrast-enhanced magnetic resonance imaging and arterial spin labeling magnetic resonance imaging were applied to measure BBB permeability and CBF, respectively. The patients with early AD showed significantly lower CBF and local blood volume in the gray matter, compared with controls. In the patients, we also found that a reduction in CBF is correlated with an increase in leakage rate. This finding supports the hypothesis that neurovascular damage, and in particular impairment of the neurovascular unit constitutes the pathophysiological link between CBF reduction and BBB impairment in AD. Copyright © 2016 Elsevier Inc. All rights reserved.

Multi-vendor reliability of arterial spin labeling perfusion MRI using a near-identical sequence: implications for multi-center studies.

PubMed

Mutsaerts, Henri J M M; van Osch, Matthias J P; Zelaya, Fernando O; Wang, Danny J J; Nordhøy, Wibeke; Wang, Yi; Wastling, Stephen; Fernandez-Seara, Maria A; Petersen, E T; Pizzini, Francesca B; Fallatah, Sameeha; Hendrikse, Jeroen; Geier, Oliver; Günther, Matthias; Golay, Xavier; Nederveen, Aart J; Bjørnerud, Atle; Groote, Inge R

2015-06-01

A main obstacle that impedes standardized clinical and research applications of arterial spin labeling (ASL), is the substantial differences between the commercial implementations of ASL from major MRI vendors. In this study, we compare a single identical 2D gradient-echo EPI pseudo-continuous ASL (PCASL) sequence implemented on 3T scanners from three vendors (General Electric Healthcare, Philips Healthcare and Siemens Healthcare) within the same center and with the same subjects. Fourteen healthy volunteers (50% male, age 26.4±4.7years) were scanned twice on each scanner in an interleaved manner within 3h. Because of differences in gradient and coil specifications, two separate studies were performed with slightly different sequence parameters, with one scanner used across both studies for comparison. Reproducibility was evaluated by means of quantitative cerebral blood flow (CBF) agreement and inter-session variation, both on a region-of-interest (ROI) and voxel level. In addition, a qualitative similarity comparison of the CBF maps was performed by three experienced neuro-radiologists. There were no CBF differences between vendors in study 1 (p>0.1), but there were CBF differences of 2-19% between vendors in study 2 (p<0.001 in most gray matter ROIs) and 10-22% difference in CBF values obtained with the same vendor between studies (p<0.001 in most gray matter ROIs). The inter-vendor inter-session variation was not significantly larger than the intra-vendor variation in all (p>0.1) but one of the ROIs (p<0.001). This study demonstrates the possibility to acquire comparable cerebral CBF maps on scanners of different vendors. Small differences in sequence parameters can have a larger effect on the reproducibility of ASL than hardware or software differences between vendors. These results suggest that researchers should strive to employ identical labeling and readout strategies in multi-center ASL studies. Copyright © 2015 Elsevier Inc. All rights reserved.

On the analysis of time-of-flight spin-echo modulated dark-field imaging data

NASA Astrophysics Data System (ADS)

Sales, Morten; Plomp, Jeroen; Bouwman, Wim G.; Tremsin, Anton S.; Habicht, Klaus; Strobl, Markus

2017-06-01

Spin-Echo Modulated Small Angle Neutron Scattering with spatial resolution, i.e. quantitative Spin-Echo Dark Field Imaging, is an emerging technique coupling neutron imaging with spatially resolved quantitative small angle scattering information. However, the currently achieved relatively large modulation periods of the order of millimeters are superimposed to the images of the samples. So far this required an independent reduction and analyses of the image and scattering information encoded in the measured data and is involving extensive curve fitting routines. Apart from requiring a priori decisions potentially limiting the information content that is extractable also a straightforward judgment of the data quality and information content is hindered. In contrast we propose a significantly simplified routine directly applied to the measured data, which does not only allow an immediate first assessment of data quality and delaying decisions on potentially information content limiting further reduction steps to a later and better informed state, but also, as results suggest, generally better analyses. In addition the method enables to drop the spatial resolution detector requirement for non-spatially resolved Spin-Echo Modulated Small Angle Neutron Scattering.

Enhancement of automated blood flow estimates (ENABLE) from arterial spin-labeled MRI.

PubMed

Shirzadi, Zahra; Stefanovic, Bojana; Chappell, Michael A; Ramirez, Joel; Schwindt, Graeme; Masellis, Mario; Black, Sandra E; MacIntosh, Bradley J

2018-03-01

To validate a multiparametric automated algorithm-ENhancement of Automated Blood fLow Estimates (ENABLE)-that identifies useful and poor arterial spin-labeled (ASL) difference images in multiple postlabeling delay (PLD) acquisitions and thereby improve clinical ASL. ENABLE is a sort/check algorithm that uses a linear combination of ASL quality features. ENABLE uses simulations to determine quality weighting factors based on an unconstrained nonlinear optimization. We acquired a set of 6-PLD ASL images with 1.5T or 3.0T systems among 98 healthy elderly and adults with mild cognitive impairment or dementia. We contrasted signal-to-noise ratio (SNR) of cerebral blood flow (CBF) images obtained with ENABLE vs. conventional ASL analysis. In a subgroup, we validated our CBF estimates with single-photon emission computed tomography (SPECT) CBF images. ENABLE produced significantly increased SNR compared to a conventional ASL analysis (Wilcoxon signed-rank test, P < 0.0001). We also found the similarity between ASL and SPECT was greater when using ENABLE vs. conventional ASL analysis (n = 51, Wilcoxon signed-rank test, P < 0.0001) and this similarity was strongly related to ASL SNR (t = 24, P < 0.0001). These findings suggest that ENABLE improves CBF image quality from multiple PLD ASL in dementia cohorts at either 1.5T or 3.0T, achieved by multiparametric quality features that guided postprocessing of dementia ASL. 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:647-655. © 2017 International Society for Magnetic Resonance in Medicine.

The role of magnetic resonance diffusion-weighted imaging and three-dimensional arterial spin labelling perfusion imaging in the differentiation of parasellar meningioma and cavernous haemangioma.

PubMed

Xiao, Hua-Feng; Lou, Xin; Liu, Meng-Yu; Wang, Yu-Lin; Wang, Yan; Chen, Zhi-Ye; Shi, Kai-Ning; Ma, Lin

2014-08-01

To evaluate the diagnostic value of magnetic resonance diffusion-weighted imaging (DWI) and three-dimensional arterial spin labelling perfusion imaging (3D-ASL) in distinguishing cavernous haemangioma from parasellar meningioma, using histological data as a reference standard. Patients with parasellar meningioma or parasellar cavernous haemangioma underwent conventional T1- and T2-weighted magnetic resonance imaging (MRI) followed by DWI and 3D-ASL using a 3.0 Tesla MRI. The minimum apparent diffusion coefficient (minADC) from DWI and the maximal normalized cerebral blood flow (nCBF) from 3D-ASL were measured in each tumour. Diagnosis was confirmed by histology. MinADC was significantly lower and nCBF significantly higher in meningioma (n = 19) than cavernous haemangioma (n = 15). There was a significant negative correlation between minADC and nCBF (r = -0.605). DWI and 3D-ASL are useful in differentiating cavernous haemangiomas from parasellar meningiomas, particularly in situations when the appearance on conventional MRI sequences is otherwise ambiguous. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Detection of malignant hepatic tumors with ferumoxides-enhanced MRI: comparison of five gradient-recalled echo sequences with different TEs.

PubMed

Matsuo, Masayuki; Kanematsu, Masayuki; Itoh, Kyo; Murakami, Takamichi; Maetani, Yoji; Kondo, Hiroshi; Goshima, Satoshi; Kako, Nobuo; Hoshi, Hiroaki; Konishi, Junji; Moriyama, Noriyuki; Nakamura, Hironobu

2004-01-01

The purpose of our study was to compare the detectability of malignant hepatic tumors on ferumoxides-enhanced MRI using five gradient-recalled echo sequences at different TEs. Ferumoxides-enhanced MRIs obtained in 31 patients with 50 malignant hepatic tumors (33 hepatocellular carcinomas, 17 metastases) were reviewed retrospectively by three independent offsite radiologists. T1-weighted gradient-recalled echo images with TEs of 1.4 and 4.2 msec; T2*-weighted gradient-recalled echo images with TEs of 6, 8, and 10 msec; and T2-weighted fast spin-echo images of livers were randomly reviewed on a segment-by-segment basis. Observer performance was tested using the McNemar test and receiver operating characteristic analysis for the clustered data. Lesion-to-liver contrast-to-noise ratio was also assessed. Mean lesion-to-liver contrast-to-noise ratios were negative and lower with gradient-recalled echo at 1.4 msec than with the other sequences. Sensitivity was higher (p < 0.05) with gradient-recalled echo at 6, 8, and 10 msec and fast spin-echo sequences (75-83%) than with gradient-recalled echo sequences at 1.4 and 4.2 msec (46-48%), and was higher (p < 0.05) with gradient-recalled echo sequence at 8 msec (83%) than with gradient-recalled echo at 6 msec and fast spin-echo sequences (75-78%). Specificity was comparably high with all sequences (95-98%). The area under the receiver operating characteristic curve (A(z)) was greater (p < 0.05) with gradient-recalled echo at 6, 8, and 10 msec and fast spin-echo sequences (A(z) = 0.91-0.93) than with gradient-recalled echo sequences at 1.4 and 4.2 msec (A(z) = 0.82-0.85). In the detection of malignant hepatic tumors, gradient-recalled echo sequences at 8 msec showed the highest sensitivity and had an A(z) value and lesion-to-liver contrast-to-noise ratio comparable with values from gradient-recalled echo sequences at 6 and 10 msec and fast spin-echo sequences.

SNR-optimized phase-sensitive dual-acquisition turbo spin echo imaging: a fast alternative to FLAIR.

PubMed

Lee, Hyunyeol; Park, Jaeseok

2013-07-01

Phase-sensitive dual-acquisition single-slab three-dimensional turbo spin echo imaging was recently introduced, producing high-resolution isotropic cerebrospinal fluid attenuated brain images without long inversion recovery preparation. Despite the advantages, the weighted-averaging-based technique suffers from noise amplification resulting from different levels of cerebrospinal fluid signal modulations over the two acquisitions. The purpose of this work is to develop a signal-to-noise ratio-optimized version of the phase-sensitive dual-acquisition single-slab three-dimensional turbo spin echo. Variable refocusing flip angles in the first acquisition are calculated using a three-step prescribed signal evolution while those in the second acquisition are calculated using a two-step pseudo-steady state signal transition with a high flip-angle pseudo-steady state at a later portion of the echo train, balancing the levels of cerebrospinal fluid signals in both the acquisitions. Low spatial frequency signals are sampled during the high flip-angle pseudo-steady state to further suppress noise. Numerical simulations of the Bloch equations were performed to evaluate signal evolutions of brain tissues along the echo train and optimize imaging parameters. In vivo studies demonstrate that compared with conventional phase-sensitive dual-acquisition single-slab three-dimensional turbo spin echo, the proposed optimization yields 74% increase in apparent signal-to-noise ratio for gray matter and 32% decrease in imaging time. The proposed method can be a potential alternative to conventional fluid-attenuated imaging. Copyright © 2012 Wiley Periodicals, Inc.

MRI of gallstones with different compositions.

PubMed

Tsai, Hong-Ming; Lin, Xi-Zhang; Chen, Chiung-Yu; Lin, Pin-Wen; Lin, Jui-Che

2004-06-01

Gallstones are usually recognized on MRI as filling defects of hypointensity. However, they sometimes may appear as hyperintensities on T1-weighted imaging. This study investigated how gallstones appear on MRI and how their appearance influences the detection of gallstones. Gallstones from 24 patients who had MRI performed before the removal of the gallstones were collected for study. The gallstones were classified either as cholesterol gallstone (n = 4) or as pigment gallstone (n = 20) according to their gross appearance and based on analysis by Fourier transform infrared spectroscopy. MRI included three sequences: single-shot fast spin-echo T2-weighted imaging, 3D fast spoiled gradient-echo T1-weighted imaging, and in-phase fast spoiled gradient-echo T1-weighted imaging. The signal intensity and the detection rate of gallstones on MRI were further correlated with the character of the gallstones. On T1-weighted 3D fast spoiled gradient-echo images, most of the pigment gallstones (18/20) were hyperintense and all the cholesterol gallstones (4/4) were hypointense. The mean ratio of the signal intensity of gallstone to bile was (+/- standard deviation) 3.36 +/- 1.88 for pigment gallstone and 0.24 +/- 0.10 for cholesterol gallstone on the 3D fast spoiled gradient-echo sequence (p < 0.001). Combining the 3D fast spoiled gradient-echo and single-shot fast spin-echo sequences achieved the highest gallstone detection rate (96.4%). Based on the differences of signal intensity of gallstones, the 3D fast spoiled gradient-echo T1-weighted imaging was able to diagnose the composition of gallstones. Adding the 3D fast spoiled gradient-echo imaging to the single-shot fast spin-echo T2-weighted sequence can further improve the detection rate of gallstones.

Comparison of arterial spin labeling registration strategies in the multi-center GENetic frontotemporal dementia initiative (GENFI).

PubMed

Mutsaerts, Henri J M M; Petr, Jan; Thomas, David L; De Vita, Enrico; Cash, David M; van Osch, Matthias J P; Golay, Xavier; Groot, Paul F C; Ourselin, Sebastien; van Swieten, John; Laforce, Robert; Tagliavini, Fabrizio; Borroni, Barbara; Galimberti, Daniela; Rowe, James B; Graff, Caroline; Pizzini, Francesca B; Finger, Elizabeth; Sorbi, Sandro; Castelo Branco, Miguel; Rohrer, Jonathan D; Masellis, Mario; MacIntosh, Bradley J

2018-01-01

To compare registration strategies to align arterial spin labeling (ASL) with 3D T1-weighted (T1w) images, with the goal of reducing the between-subject variability of cerebral blood flow (CBF) images. Multi-center 3T ASL data were collected at eight sites with four different sequences in the multi-center GENetic Frontotemporal dementia Initiative (GENFI) study. In a total of 48 healthy controls, we compared the following image registration options: (I) which images to use for registration (perfusion-weighted images [PWI] to the segmented gray matter (GM) probability map (pGM) (CBF-pGM) or M0 to T1w (M0-T1w); (II) which transformation to use (rigid-body or non-rigid); and (III) whether to mask or not (no masking, M0-based FMRIB software library Brain Extraction Tool [BET] masking). In addition to visual comparison, we quantified image similarity using the Pearson correlation coefficient (CC), and used the Mann-Whitney U rank sum test. CBF-pGM outperformed M0-T1w (CC improvement 47.2% ± 22.0%; P < 0.001), and the non-rigid transformation outperformed rigid-body (20.6% ± 5.3%; P < 0.001). Masking only improved the M0-T1w rigid-body registration (14.5% ± 15.5%; P = 0.007). The choice of image registration strategy impacts ASL group analyses. The non-rigid transformation is promising but requires validation. CBF-pGM rigid-body registration without masking can be used as a default strategy. In patients with expansive perfusion deficits, M0-T1w may outperform CBF-pGM in sequences with high effective spatial resolution. BET-masking only improves M0-T1w registration when the M0 image has sufficient contrast. 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:131-140. © 2017 International Society for Magnetic Resonance in Medicine.

Basal Ganglia Perfusion in Fibromyalgia is Related to Pain Disability and Disease Impact: An Arterial Spin Labeling Study.

PubMed

Shokouhi, Mahsa; Davis, Karen D; Moulin, Dwight E; Morley-Forster, Pat; Nielson, Warren R; Bureau, Yves; St Lawrence, Keith

2016-06-01

Pain disability is a major impediment to fibromyalgia (FM) patients' quality of life. Neuroimaging studies have demonstrated abnormal pain processing in FM. However, it is not known whether there are brain abnormalities linked to pain disability. Understanding neural correlates of pain disability in FM, independent from pain intensity, could provide a framework to guide future more efficient therapy strategies to improve patients' functional ability. We used arterial spin labeling to image cerebral blood flow (CBF) in 23 FM patients and 16 controls. Functional connectivity was also estimated using blood oxygenation level-dependent imaging to further investigate the possible underpinnings of the observed CBF changes. Among patients, CBF in the basal ganglia correlated negatively with pain disability index and positively with the overall impact of FM (Fibromyalgia Impact Questionnaire) but did not correlate with pain intensity. Whole-brain analysis revealed no CBF differences between the 2 groups; however, post hoc analysis in the basal ganglia showed CBF reductions mainly in the right putamen and right lateral globus pallidus in patients, likely reflecting the negative correlation with the pain disability index. However, the connectivity of the corresponding corticobasal ganglia-thalamus loop, that is, motor network (the connection between supplementary motor area, putamen, and thalamus) remained intact. Basal ganglia perfusion reflects long-term symptoms, including somatic and psychological components of FM rather than pain intensity. These CBF findings may reflect differences in behavioral and psychological responses between patients.

The severity of anaemia depletes cerebrovascular dilatory reserve in children with sickle cell disease: a quantitative magnetic resonance imaging study.

PubMed

Kosinski, Przemyslaw D; Croal, Paula L; Leung, Jackie; Williams, Suzan; Odame, Isaac; Hare, Gregory M T; Shroff, Manohar; Kassner, Andrea

2017-01-01

Overt ischaemic stroke is one of the most devastating complications in children with sickle cell disease (SCD). The compensatory response to anaemia in SCD includes an increase in cerebral blood flow (CBF) by accessing cerebrovascular dilatory reserve. Exhaustion of dilatory reserve secondary to anaemic stress may lead to cerebral ischaemia. The purpose of this study was to investigate CBF and cerebrovascular reactivity (CVR) using magnetic resonance imaging (MRI) in children with SCD and to correlate these with haematological markers of anaemia. Baseline CBF was measured using arterial spin labelling. Blood-oxygen level-dependent MRI in response to a CO 2 stimulus was used to acquire CVR. In total, 28 children with SCD (23 not on any disease-modifying treatment, 5 on chronic transfusion) and 22 healthy controls were imaged using MRI. Transfusion patients were imaged at two time points to assess the effect of changes in haematocrit after a transfusion cycle. In children with SCD, CBF was significantly elevated compared to healthy controls, while CVR was significantly reduced. Both measures were significantly correlated with haematocrit. For transfusion patients, CBF decreased and CVR increased following a transfusion cycle. Lastly, a significant correlation was observed between CBF and CVR in both children with SCD and healthy controls. © 2016 John Wiley & Sons Ltd.

Cerebral Perfusion Is Perturbed by Preterm Birth and Brain Injury.

PubMed

Mahdi, E S; Bouyssi-Kobar, M; Jacobs, M B; Murnick, J; Chang, T; Limperopoulos, C

2018-05-10

Early disturbances in systemic and cerebral hemodynamics are thought to mediate prematurity-related brain injury. However, the extent to which CBF is perturbed by preterm birth is unknown. Our aim was to compare global and regional CBF in preterm infants with and without brain injury on conventional MR imaging using arterial spin-labeling during the third trimester of ex utero life and to examine the relationship between clinical risk factors and CBF. We prospectively enrolled preterm infants younger than 32 weeks' gestational age and <1500 g and performed arterial spin-labeling MR imaging studies. Global and regional CBF in the cerebral cortex, thalami, pons, and cerebellum was quantified. Preterm infants were stratified into those with and without structural brain injury. We further categorized preterm infants by brain injury severity: moderate-severe and mild. We studied 78 preterm infants: 31 without brain injury and 47 with brain injury (29 with mild and 18 with moderate-severe injury). Global CBF showed a borderline significant increase with increasing gestational age at birth ( P = .05) and trended lower in preterm infants with brain injury ( P = .07). Similarly, regional CBF was significantly lower in the right thalamus and midpons ( P < .05) and trended lower in the midtemporal, left thalamus, and anterior vermis regions ( P < .1) in preterm infants with brain injury. Regional CBF in preterm infants with moderate-severe brain injury trended lower in the midpons, right cerebellar hemisphere, and dentate nuclei compared with mild brain injury ( P < .1). In addition, a significant, lower regional CBF was associated with ventilation, sepsis, and cesarean delivery ( P < .05). We report early disturbances in global and regional CBF in preterm infants following brain injury. Regional cerebral perfusion alterations were evident in the thalamus and pons, suggesting regional vulnerability of the developing cerebro-cerebellar circuitry. © 2018 by American Journal of Neuroradiology.

Dedicated phantom to study susceptibility artifacts caused by depth electrode in magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Garcia, J.; Hidalgo, S. S.; Solis, S. E.; Vazquez, D.; Nuñez, J.; Rodriguez, A. O.

2012-10-01

The susceptibility artifacts can degrade of magnetic resonance image quality. Electrodes are an important source of artifacts when performing brain imaging. A dedicated phantom was built using a depth electrode to study the susceptibility effects under different pulse sequences. T2-weighted images were acquired with both gradient-and spin-echo sequences. The spin-echo sequences can significantly attenuate the susceptibility artifacts allowing a straightforward visualization of the regions surrounding the electrode.

Using arterial spin labeling to examine mood states in youth.

PubMed

Mikita, Nina; Mehta, Mitul A; Zelaya, Fernando O; Stringaris, Argyris

2015-06-01

Little is known about the neural correlates of mood states and the specific physiological changes associated with their valence and duration, especially in young people. Arterial spin labeling (ASL) imaging is particularly well-suited to study sustained cerebral states in young people, due to its robustness to low-frequency drift, excellent interscan reliability, and noninvasiveness. Yet, it has so far been underutilized for understanding the neural mechanisms underlying mood states in youth. In this exploratory study, 21 healthy adolescents aged 16 to 18 took part in a mood induction experiment. Neutral, sad, and happy mood states were induced using film clips and explicit instructions. An ASL scan was obtained following presentation of each film clip. Mood induction led to robust changes in self-reported mood ratings. Compared to neutral, sad mood was associated with increased regional cerebral blood flow (rCBF) in the left middle frontal gyrus and anterior prefrontal cortex, and decreased rCBF in the right middle frontal gyrus and the inferior parietal lobule. A decrease in self-reported mood from neutral to sad condition was associated with increased rCBF in the precuneus. Happy mood was associated with increased rCBF in medial frontal and cingulate gyri, the subgenual anterior cingulate cortex, and ventral striatum, and decreased rCBF in the inferior parietal lobule. The level of current self-reported depressive symptoms was negatively associated with rCBF change in the cerebellum and lingual gyrus following both sad and happy mood inductions. Arterial spin labeling is sensitive to experimentally induced mood changes in healthy young people. The effects of happy mood on rCBF patterns were generally stronger than the effects of sad mood.

Prediction of Blood-Brain Barrier Disruption and Intracerebral Hemorrhagic Infarction Using Arterial Spin-Labeling Magnetic Resonance Imaging.

PubMed

Niibo, Takeya; Ohta, Hajime; Miyata, Shirou; Ikushima, Ichiro; Yonenaga, Kazuchika; Takeshima, Hideo

2017-01-01

Arterial spin-labeling magnetic resonance imaging is sensitive for detecting hyperemic lesions (HLs) in patients with acute ischemic stroke. We evaluated whether HLs could predict blood-brain barrier (BBB) disruption and hemorrhagic transformation (HT) in acute ischemic stroke patients. In a retrospective study, arterial spin-labeling was performed within 6 hours of symptom onset before revascularization treatment in 25 patients with anterior circulation large vessel occlusion on baseline magnetic resonance angiography. All patients underwent angiographic procedures intended for endovascular therapy and a noncontrast computed tomography scan immediately after treatment. BBB disruption was defined as a hyperdense lesion present on the posttreatment computed tomography scan. A subacute magnetic resonance imaging or computed tomography scan was performed during the subacute phase to assess HTs. The relationship between HLs and BBB disruption and HT was examined using the Alberta Stroke Program Early Computed Tomography Score locations in the symptomatic hemispheres. A HL was defined as a region where CBF relative ≥1.4 (CBF relative =CBF HL /CBF contralateral ). HLs, BBB disruption, and HT were found in 9, 15, and 15 patients, respectively. Compared with the patients without HLs, the patients with HLs had a higher incidence of both BBB disruption (100% versus 37.5%; P=0.003) and HT (100% versus 37.5%; P=0.003). Based on the Alberta Stroke Program Early Computed Tomography Score locations, 21 regions of interests displayed HLs. Compared with the regions of interests without HLs, the regions of interests with HLs had a higher incidence of both BBB disruption (42.8% versus 3.9%; P<0.001) and HT (85.7% versus 7.8%; P<0.001). HLs detected on pretreatment arterial spin-labeling maps may enable the prediction and localization of subsequent BBB disruption and HT. © 2016 American Heart Association, Inc.

Therapy-related longitudinal brain perfusion changes in patients with chronic pelvic pain syndrome.

PubMed

Weisstanner, Christian; Mordasini, Livio; Thalmann, George N; Verma, Rajeev K; Rummel, Christian; Federspiel, Andrea; Kessler, Thomas M; Wiest, Roland

2017-08-03

The imaging method most frequently employed to identify brain areas involved in neuronal processing of nociception and brain pain perception is blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI). Arterial spin labelling (ASL), in contrast, offers advantages when slow varying changes in brain function are investigated. Chronic pelvic pain syndrome (CPPS) is a disorder of, mostly, young males that leads to altered pain perceptions in structures related to the pelvis. We aimed to investigate the potential of ASL to monitor longitudinal cranial blood flow (CBF) changes in patients with CPPS. In a randomised, placebo-controlled, double-blind single centre trial, we investigated treatment effects in CPPS after 12 weeks in patients that underwent sono-electro-magnetic therapy vs placebo. We investigated changes of CBF related to treatment outcome using pseudo-continuous arterial spin labelling (pCASL)-MRI. We observed CBF downregulation in the prefrontal cortex and anterior cingulate cortex and upregulation in the dorsolateral prefrontal cortex in responders. Nonresponders presented with CBF upregulation in the hippocampus. In patients with a history of CPPS of less than 12 months, there were significant correlations between longitudinal CBF changes and the Chronic Prostatitis Symptom Index pain subscore within the joint clusters anterior cingulate cortex and left anterior prefrontal cortex in responders, and the right hippocampus in nonresponders. We demonstrated therapy-related and stimulus-free longitudinal CBF changes in core areas of the pain matrix using ASL. ASL may act as a complementary noninvasive method to functional MRI and single-photon emission computed tomography / positron emission tomography, especially in the longitudinal assessment of pain response in clinical trials.

The effect of black tea and caffeine on regional cerebral blood flow measured with arterial spin labeling

PubMed Central

Vidyasagar, Rishma; Greyling, Arno; Draijer, Richard; Corfield, Douglas R; Parkes, Laura M

2013-01-01

Black tea consumption has been shown to improve peripheral vascular function. Its effect on brain vasculature is unknown, though tea contains small amounts of caffeine, a psychoactive substance known to influence cerebral blood flow (CBF). We investigated the effects on CBF due to the intake of tea components in 20 healthy men in a double-blinded, randomized, placebo-controlled study. On separate days, subjects received a single dose of 184 mg caffeine (equivalent to one strong espresso coffee), 2,820 mg black tea solids containing 184 mg caffeine (equivalent to 6 cups of tea), 2,820 mg decaffeinated black tea solids, or placebo. The CBF and cerebrovascular reactivity (CVR) to hypercapnia were measured with arterial spin labeled magnetic resonance imaging (MRI) before and 2 hours after administration. We found a significant global reduction with caffeine (20%) and tea (21%) in gray matter CBF, with no effect of decaffeinated tea, suggesting that only caffeine influences CBF acutely. Voxelwise analysis revealed the effect of caffeine to be regionally specific. None of the interventions had an effect on CVR. Additional research is required to conclude on the physiologic relevance of these findings and the chronic effects of caffeine and tea intake on CBF. PMID:23486295

Computer-aided classification of patients with dementia of Alzheimer's type based on cerebral blood flow determined with arterial spin labeling technique

NASA Astrophysics Data System (ADS)

Yamashita, Yasuo; Arimura, Hidetaka; Yoshiura, Takashi; Tokunaga, Chiaki; Magome, Taiki; Monji, Akira; Noguchi, Tomoyuki; Toyofuku, Fukai; Oki, Masafumi; Nakamura, Yasuhiko; Honda, Hiroshi

2010-03-01

Arterial spin labeling (ASL) is one of promising non-invasive magnetic resonance (MR) imaging techniques for diagnosis of Alzheimer's disease (AD) by measuring cerebral blood flow (CBF). The aim of this study was to develop a computer-aided classification system for AD patients based on CBFs measured by the ASL technique. The average CBFs in cortical regions were determined as functional image features based on the CBF map image, which was non-linearly transformed to a Talairach brain atlas by using a free-form deformation. An artificial neural network (ANN) was trained with the CBF functional features in 10 cortical regions, and was employed for distinguishing patients with AD from control subjects. For evaluation of the method, we applied the proposed method to 20 cases including ten AD patients and ten control subjects, who were scanned a 3.0-Tesla MR unit. As a result, the area under the receiver operating characteristic curve obtained by the proposed method was 0.893 based on a leave-one-out-by-case test in identification of AD cases among 20 cases. The proposed method would be feasible for classification of patients with AD.

Accelerated Slice Encoding for Metal Artifact Correction

PubMed Central

Hargreaves, Brian A.; Chen, Weitian; Lu, Wenmiao; Alley, Marcus T.; Gold, Garry E.; Brau, Anja C. S.; Pauly, John M.; Pauly, Kim Butts

2010-01-01

Purpose To demonstrate accelerated imaging with artifact reduction near metallic implants and different contrast mechanisms. Materials and Methods Slice-encoding for metal artifact correction (SEMAC) is a modified spin echo sequence that uses view-angle tilting and slice-direction phase encoding to correct both in-plane and through-plane artifacts. Standard spin echo trains and short-TI inversion recovery (STIR) allow efficient PD-weighted imaging with optional fat suppression. A completely linear reconstruction allows incorporation of parallel imaging and partial Fourier imaging. The SNR effects of all reconstructions were quantified in one subject. 10 subjects with different metallic implants were scanned using SEMAC protocols, all with scan times below 11 minutes, as well as with standard spin echo methods. Results The SNR using standard acceleration techniques is unaffected by the linear SEMAC reconstruction. In all cases with implants, accelerated SEMAC significantly reduced artifacts compared with standard imaging techniques, with no additional artifacts from acceleration techniques. The use of different contrast mechanisms allowed differentiation of fluid from other structures in several subjects. Conclusion SEMAC imaging can be combined with standard echo-train imaging, parallel imaging, partial-Fourier imaging and inversion recovery techniques to offer flexible image contrast with a dramatic reduction of metal-induced artifacts in scan times under 11 minutes. PMID:20373445

Accelerated slice encoding for metal artifact correction.

PubMed

Hargreaves, Brian A; Chen, Weitian; Lu, Wenmiao; Alley, Marcus T; Gold, Garry E; Brau, Anja C S; Pauly, John M; Pauly, Kim Butts

2010-04-01

To demonstrate accelerated imaging with both artifact reduction and different contrast mechanisms near metallic implants. Slice-encoding for metal artifact correction (SEMAC) is a modified spin echo sequence that uses view-angle tilting and slice-direction phase encoding to correct both in-plane and through-plane artifacts. Standard spin echo trains and short-TI inversion recovery (STIR) allow efficient PD-weighted imaging with optional fat suppression. A completely linear reconstruction allows incorporation of parallel imaging and partial Fourier imaging. The signal-to-noise ratio (SNR) effects of all reconstructions were quantified in one subject. Ten subjects with different metallic implants were scanned using SEMAC protocols, all with scan times below 11 minutes, as well as with standard spin echo methods. The SNR using standard acceleration techniques is unaffected by the linear SEMAC reconstruction. In all cases with implants, accelerated SEMAC significantly reduced artifacts compared with standard imaging techniques, with no additional artifacts from acceleration techniques. The use of different contrast mechanisms allowed differentiation of fluid from other structures in several subjects. SEMAC imaging can be combined with standard echo-train imaging, parallel imaging, partial-Fourier imaging, and inversion recovery techniques to offer flexible image contrast with a dramatic reduction of metal-induced artifacts in scan times under 11 minutes. (c) 2010 Wiley-Liss, Inc.

Spatial Nonuniformity of the Resting CBF and BOLD Responses to Sevoflurane: In Vivo Study of Normal Human Subjects With Magnetic Resonance Imaging

PubMed Central

Qiu, Maolin; Ramani, Ramachandran; Swetye, Michael; Constable, Robert Todd

2009-01-01

Pulsed arterial spin labeling magnetic resonance imaging (MRI) was performed to investigate the local coupling between resting regional cerebral blood flow (rCBF) and BOLD (blood oxygen level dependent) signal changes in 22 normal human subjects during the administration of 0.25 MAC (minimum alveolar concentration) sevoflurane. Two states were compared with subjects at rest: anesthesia and no-anesthesia. Regions of both significantly increased and decreased resting-state rCBF were observed. Increases were limited primarily to subcortical structures and insula, whereas, decreases were observed primarily in neocortical regions. No significant change was found in global CBF (gCBF). By simultaneously measuring rCBF and BOLD, region-specific anesthetic effects on the coupling between rCBF and BOLD were identified. Multiple comparisons of the agent-induced rCBF and BOLD changes demonstrated significant (P < 0.05) spatial variability in rCBF–BOLD coupling. The slope of the linear regression line for AC, where rCBF was increased by sevoflurane, was markedly smaller than the slope for those ROIs where rCBF was decreased by sevoflurane, indicating a bigger change in BOLD per unit change in rCBF in regions where rCBF was increased by sevoflurane. These results suggest that it would be inaccurate to use a global quantitative model to describe coupling across all brain regions and in all anesthesia conditions. The observed spatial nonuniformity of rCBF and BOLD signal changes suggests that any interpretation of BOLD fMRI data in the presence of an anesthetic requires consideration of these insights. PMID:17948882

A feasibility study on estimation of tissue mixture contributions in 3D arterial spin labeling sequence

NASA Astrophysics Data System (ADS)

Liu, Yang; Pu, Huangsheng; Zhang, Xi; Li, Baojuan; Liang, Zhengrong; Lu, Hongbing

2017-03-01

Arterial spin labeling (ASL) provides a noninvasive measurement of cerebral blood flow (CBF). Due to relatively low spatial resolution, the accuracy of CBF measurement is affected by the partial volume (PV) effect. To obtain accurate CBF estimation, the contribution of each tissue type in the mixture is desirable. In general, this can be obtained according to the registration of ASL and structural image in current ASL studies. This approach can obtain probability of each tissue type inside each voxel, but it also introduces error, which include error of registration algorithm and imaging itself error in scanning of ASL and structural image. Therefore, estimation of mixture percentage directly from ASL data is greatly needed. Under the assumption that ASL signal followed the Gaussian distribution and each tissue type is independent, a maximum a posteriori expectation-maximization (MAP-EM) approach was formulated to estimate the contribution of each tissue type to the observed perfusion signal at each voxel. Considering the sensitivity of MAP-EM to the initialization, an approximately accurate initialization was obtain using 3D Fuzzy c-means method. Our preliminary results demonstrated that the GM and WM pattern across the perfusion image can be sufficiently visualized by the voxel-wise tissue mixtures, which may be promising for the diagnosis of various brain diseases.

High Efficiency, Low Distortion 3D Diffusion Tensor Imaging with Variable Density Spiral Fast Spin Echoes (3D DW VDS RARE)

PubMed Central

Frank, Lawrence R.; Jung, Youngkyoo; Inati, Souheil; Tyszka, J. Michael; Wong, Eric C.

2009-01-01

We present an acquisition and reconstruction method designed to acquire high resolution 3D fast spin echo diffusion tensor images while mitigating the major sources of artifacts in DTI - field distortions, eddy currents and motion. The resulting images, being 3D, are of high SNR, and being fast spin echoes, exhibit greatly reduced field distortions. This sequence utilizes variable density spiral acquisition gradients, which allow for the implementation of a self-navigation scheme by which both eddy current and motion artifacts are removed. The result is that high resolution 3D DTI images are produced without the need for eddy current compensating gradients or B0 field correction. In addition, a novel method for fast and accurate reconstruction of the non-Cartesian data is employed. Results are demonstrated in the brains of normal human volunteers. PMID:19778618

Comparison of axial T1 spin-echo and T1 fat-saturation magnetic resonance imaging techniques in the diagnosis of chondromalacia patellae.

PubMed

Vanarthos, W J; Pope, T L; Monu, J U

1994-12-01

To test the diagnostic value of T1 spin-echo and T1 fat-saturated magnetic resonance images (MRIs), we reviewed axial T1-weighted images with and without fat saturation in 20 patients with clinically suspected chondromalacia of the patella. All scans were obtained on 1.5-MR units. The scans were randomly ordered and reviewed independently at different times by two radiologists without knowledge of the arthroscopy results. The sensitivity of the individual techniques for detecting grade 3 or 4 chondromalacia patellae was 92% for fat-saturated axial T1-weighted images alone, and 67% for axial T1-weighted images without fat saturation. The sensitivity of the combined techniques was 100% for grades 3 and 4 and 90% for all grades (0 to 4). Chondromalacia patellae is diagnosed more accurately by using T1 fat saturation than by using T1 spin-echo images. With a combination of the two techniques, accuracy is 90% to 100%.

Arterial Spin Labeling (ASL) fMRI: advantages, theoretical constrains, and experimental challenges in neurosciences.

PubMed

Borogovac, Ajna; Asllani, Iris

2012-01-01

Cerebral blood flow (CBF) is a well-established correlate of brain function and therefore an essential parameter for studying the brain at both normal and diseased states. Arterial spin labeling (ASL) is a noninvasive fMRI technique that uses arterial water as an endogenous tracer to measure CBF. ASL provides reliable absolute quantification of CBF with higher spatial and temporal resolution than other techniques. And yet, the routine application of ASL has been somewhat limited. In this review, we start by highlighting theoretical complexities and technical challenges of ASL fMRI for basic and clinical research. While underscoring the main advantages of ASL versus other techniques such as BOLD, we also expound on inherent challenges and confounds in ASL perfusion imaging. In closing, we expound on several exciting developments in the field that we believe will make ASL reach its full potential in neuroscience research.

Spatial nonuniformity of the resting CBF and BOLD responses to sevoflurane: in vivo study of normal human subjects with magnetic resonance imaging.

PubMed

Qiu, Maolin; Ramani, Ramachandran; Swetye, Michael; Constable, Robert Todd

2008-12-01

Pulsed arterial spin labeling magnetic resonance imaging (MRI) was performed to investigate the local coupling between resting regional cerebral blood flow (rCBF) and BOLD (blood oxygen level dependent) signal changes in 22 normal human subjects during the administration of 0.25 MAC (minimum alveolar concentration) sevoflurane. Two states were compared with subjects at rest: anesthesia and no-anesthesia. Regions of both significantly increased and decreased resting-state rCBF were observed. Increases were limited primarily to subcortical structures and insula, whereas, decreases were observed primarily in neocortical regions. No significant change was found in global CBF (gCBF). By simultaneously measuring rCBF and BOLD, region-specific anesthetic effects on the coupling between rCBF and BOLD were identified. Multiple comparisons of the agent-induced rCBF and BOLD changes demonstrated significant (P < 0.05) spatial variability in rCBF-BOLD coupling. The slope of the linear regression line for AC, where rCBF was increased by sevoflurane, was markedly smaller than the slope for those ROIs where rCBF was decreased by sevoflurane, indicating a bigger change in BOLD per unit change in rCBF in regions where rCBF was increased by sevoflurane. These results suggest that it would be inaccurate to use a global quantitative model to describe coupling across all brain regions and in all anesthesia conditions. The observed spatial nonuniformity of rCBF and BOLD signal changes suggests that any interpretation of BOLD fMRI data in the presence of an anesthetic requires consideration of these insights. Copyright 2007 Wiley-Liss, Inc.

Arterial spin labelling reveals prolonged arterial arrival time in idiopathic Parkinson's disease.

PubMed

Al-Bachari, Sarah; Parkes, Laura M; Vidyasagar, Rishma; Hanby, Martha F; Tharaken, Vivek; Leroi, Iracema; Emsley, Hedley C A

2014-01-01

Idiopathic Parkinson's disease (IPD) is the second most common neurodegenerative disease, yet effective disease modifying treatments are still lacking. Neurodegeneration involves multiple interacting pathological pathways. The extent to which neurovascular mechanisms are involved is not well defined in IPD. We aimed to determine whether novel magnetic resonance imaging (MRI) techniques, including arterial spin labelling (ASL) quantification of cerebral perfusion, can reveal altered neurovascular status (NVS) in IPD. Fourteen participants with IPD (mean ± SD age 65.1 ± 5.9 years) and 14 age and cardiovascular risk factor matched control participants (mean ± SD age 64.6 ± 4.2 years) underwent a 3T MRI scan protocol. ASL images were collected before, during and after a 6 minute hypercapnic challenge. FLAIR images were used to determine white matter lesion score. Quantitative images of cerebral blood flow (CBF) and arterial arrival time (AAT) were calculated from the ASL data both at rest and during hypercapnia. Cerebrovascular reactivity (CVR) images were calculated, depicting the change in CBF and AAT relative to the change in end-tidal CO2. A significant (p = 0.005) increase in whole brain averaged baseline AAT was observed in IPD participants (mean ± SD age 1532 ± 138 ms) compared to controls (mean ± SD age 1335 ± 165 ms). Voxel-wise analysis revealed this to be widespread across the brain. However, there were no statistically significant differences in white matter lesion score, CBF, or CVR between patients and controls. Regional CBF, but not AAT, in the IPD group was found to correlate positively with Montreal cognitive assessment (MoCA) scores. These findings provide further evidence of alterations in NVS in IPD.

High-Resolution Magnetic Resonance Imaging Enhanced With Superparamagnetic Nanoparticles Measures Macrophage Burden in Atherosclerosis

PubMed Central

Morishige, Kunio; Kacher, Daniel F.; Libby, Peter; Josephson, Lee; Ganz, Peter; Weissleder, Ralph; Aikawa, Masanori

2010-01-01

Background Macrophages contribute to the progression and acute complications of atherosclerosis. Macrophage imaging may serve as a biomarker to identify subclinical inflamed lesions, to predict future risk, and to aid in the assessment of novel therapies. Methods and Results To test the hypothesis that nanoparticle-enhanced, high-resolution magnetic resonance imaging (MRI) can measure plaque macrophage accumulation, we used 3-T MRI with a macrophage-targeted superparamagnetic nanoparticle preparation (monocrystalline iron oxide nanoparticles-47 [MION-47]) in cholesterol-fed New Zealand White rabbits 6 months after balloon injury. In vivo MRI visualized thickened abdominal aortas on both T1- and T2-weighted spin-echo images (T1 spin echo, 20 axial slices per animal; T2 spin echo, 28 slices per animal). Seventy-two hours after MION-47 injection, aortas exhibited lower T2 signal intensity compared with before contrast imaging (signal intensity ratio, aortic wall/muscle: before, 1.44±0.26 versus after, 0.95±0.22; 164 slices; P<0.01), whereas T1 spin echo images showed no significant change. MRI on ex vivo specimens provided similar results. Histological studies colocalized iron accumulation with immunoreactive macrophages in atheromata. The magnitude of signal intensity reduction on T2 spin echo in vivo images further correlated with macrophage areas in situ (150 slices; r=0.73). Treatment with rosuvastatin for 3 months yielded diminished macrophage content (P<0.05) and reversed T2 signal intensity changes (P<0.005). Signal changes in rosuvastatin-treated rabbits correlated with reduced macrophage burden (r=0.73). In vitro validation studies showed concentration-dependent MION-47 uptake by human primary macrophages. Conclusion The magnitude of T2 signal intensity reduction in high-resolution MRI after administration of superparamagnetic phagocytosable nanoparticles can assess macrophage burden in atheromata, providing a clinically translatable tool to identify inflamed plaques and to monitor therapy-mediated changes in plaque inflammation. PMID:20937980

Diffusion-prepared stimulated-echo turbo spin echo (DPsti-TSE): An eddy current-insensitive sequence for three-dimensional high-resolution and undistorted diffusion-weighted imaging.

PubMed

Zhang, Qinwei; Coolen, Bram F; Versluis, Maarten J; Strijkers, Gustav J; Nederveen, Aart J

2017-07-01

In this study, we present a new three-dimensional (3D), diffusion-prepared turbo spin echo sequence based on a stimulated-echo read-out (DPsti-TSE) enabling high-resolution and undistorted diffusion-weighted imaging (DWI). A dephasing gradient in the diffusion preparation module and rephasing gradients in the turbo spin echo module create stimulated echoes, which prevent signal loss caused by eddy currents. Near to perfect agreement of apparent diffusion coefficient (ADC) values between DPsti-TSE and diffusion-weighted echo planar imaging (DW-EPI) was demonstrated in both phantom transient signal experiments and phantom imaging experiments. High-resolution and undistorted DPsti-TSE was demonstrated in vivo in prostate and carotid vessel wall. 3D whole-prostate DWI was achieved with four b values in only 6 min. Undistorted ADC maps of the prostate peripheral zone were obtained at low and high imaging resolutions with no change in mean ADC values [(1.60 ± 0.10) × 10 -3 versus (1.60 ± 0.02) × 10 -3  mm 2 /s]. High-resolution 3D DWI of the carotid vessel wall was achieved in 12 min, with consistent ADC values [(1.40 ± 0.23) × 10 -3  mm 2 /s] across different subjects, as well as slice locations through the imaging volume. This study shows that DPsti-TSE can serve as a robust 3D diffusion-weighted sequence and is an attractive alternative to the traditional two-dimensional DW-EPI approaches. Copyright © 2017 John Wiley & Sons, Ltd.

Accuracy and precision of pseudo-continuous arterial spin labeling perfusion during baseline and hypercapnia: a head-to-head comparison with ¹⁵O H₂O positron emission tomography.

PubMed

Heijtel, D F R; Mutsaerts, H J M M; Bakker, E; Schober, P; Stevens, M F; Petersen, E T; van Berckel, B N M; Majoie, C B L M; Booij, J; van Osch, M J P; Vanbavel, E; Boellaard, R; Lammertsma, A A; Nederveen, A J

2014-05-15

Measurements of the cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) provide useful information about cerebrovascular condition and regional metabolism. Pseudo-continuous arterial spin labeling (pCASL) is a promising non-invasive MRI technique to quantitatively measure the CBF, whereas additional hypercapnic pCASL measurements are currently showing great promise to quantitatively assess the CVR. However, the introduction of pCASL at a larger scale awaits further evaluation of the exact accuracy and precision compared to the gold standard. (15)O H₂O positron emission tomography (PET) is currently regarded as the most accurate and precise method to quantitatively measure both CBF and CVR, though it is one of the more invasive methods as well. In this study we therefore assessed the accuracy and precision of quantitative pCASL-based CBF and CVR measurements by performing a head-to-head comparison with (15)O H₂O PET, based on quantitative CBF measurements during baseline and hypercapnia. We demonstrate that pCASL CBF imaging is accurate during both baseline and hypercapnia with respect to (15)O H₂O PET with a comparable precision. These results pave the way for quantitative usage of pCASL MRI in both clinical and research settings. Copyright © 2014 Elsevier Inc. All rights reserved.

Removal of intensity bias in magnitude spin-echo MRI images by nonlinear diffusion filtering

NASA Astrophysics Data System (ADS)

Samsonov, Alexei A.; Johnson, Chris R.

2004-05-01

MRI data analysis is routinely done on the magnitude part of complex images. While both real and imaginary image channels contain Gaussian noise, magnitude MRI data are characterized by Rice distribution. However, conventional filtering methods often assume image noise to be zero mean and Gaussian distributed. Estimation of an underlying image using magnitude data produces biased result. The bias may lead to significant image errors, especially in areas of low signal-to-noise ratio (SNR). The incorporation of the Rice PDF into a noise filtering procedure can significantly complicate the method both algorithmically and computationally. In this paper, we demonstrate that inherent image phase smoothness of spin-echo MRI images could be utilized for separate filtering of real and imaginary complex image channels to achieve unbiased image denoising. The concept is demonstrated with a novel nonlinear diffusion filtering scheme developed for complex image filtering. In our proposed method, the separate diffusion processes are coupled through combined diffusion coefficients determined from the image magnitude. The new method has been validated with simulated and real MRI data. The new method has provided efficient denoising and bias removal in conventional and black-blood angiography MRI images obtained using fast spin echo acquisition protocols.

Inner-volume echo volumar imaging (IVEVI) for robust fetal brain imaging.

PubMed

Nunes, Rita G; Ferrazzi, Giulio; Price, Anthony N; Hutter, Jana; Gaspar, Andreia S; Rutherford, Mary A; Hajnal, Joseph V

2018-07-01

Fetal functional MRI studies using conventional 2-dimensional single-shot echo-planar imaging sequences may require discarding a large data fraction as a result of fetal and maternal motion. Increasing the temporal resolution using echo volumar imaging (EVI) could provide an effective alternative strategy. Echo volumar imaging was combined with inner volume (IV) imaging (IVEVI) to locally excite the fetal brain and acquire full 3-dimensional images, fast enough to freeze most fetal head motion. IVEVI was implemented by modifying a standard multi-echo echo-planar imaging sequence. A spin echo with orthogonal excitation and refocusing ensured localized excitation. To introduce T2* weighting and to save time, the k-space center was shifted relative to the spin echo. Both single and multi-shot variants were tested. Acoustic noise was controlled by adjusting the amplitude and switching frequency of the readout gradient. Image-based shimming was used to minimize B 0 inhomogeneities within the fetal brain. The sequence was first validated in an adult. Eight fetuses were scanned using single-shot IVEVI at a 3.5 × 3.5 × 5.0 mm 3 resolution with a readout duration of 383 ms. Multishot IVEVI showed reduced geometric distortions along the second phase-encode direction. Fetal EVI remains challenging. Although effective echo times comparable to the T2* values of fetal cortical gray matter at 3 T could be achieved, controlling acoustic noise required longer readouts, leading to substantial distortions in single-shot images. Although multishot variants enabled us to reduce susceptibility-induced geometric distortions, sensitivity to motion was increased. Future studies should therefore focus on improvements to multishot variants. Magn Reson Med 80:279-285, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

MR-monitored LITT as a palliative concept in patients with high grade gliomas: preliminary clinical experience.

PubMed

Reimer, P; Bremer, C; Horch, C; Morgenroth, C; Allkemper, T; Schuierer, G

1998-01-01

The purpose of this study was to evaluate the clinical utility of laser-induced thermotherapy (LITT) as a palliative treatment for patients with high-grade gliomas. Four consenting patients with recurrent high grade III/IV gliomas near the primary language or motor areas were palliatively treated with LITT (2-5 W, 3-13 minutes; Neodym YAG Laser, Dornier, Friedrichshafen, Germany). Temperature monitoring was performed by T1-weighted turbo-fast low-angle shot (FLASH) imaging at 1.5 T (Siemens Magnetom SP 4000, Siemens, Erlangen, Germany). MRI studies before LITT included contrast-enhanced conventional scans and functional activation studies to localize the primary motor cortex or language areas using an echo-planar imaging (EPI) spin-echo (SE) sequence. Follow-up studies consisted of contrast-enhanced conventional scans as well as diffusion studies (contrast-enhanced Fourier-acquired steady-state technique and EPI-SE) and perfusion studies (EPI-SE with .2 mmol of gadolinium (Gd)/kg body weight) to differentiate post-therapeutic effects from residual or recurrent tumor growth. Local tumor control was achieved in areas with laser energy deposition with clinically stable conditions > or = 6 months. Conventional contrast-enhanced scans demonstrated strong enhancement surrounding ablated tumor components, which showed a reduction in CBV/CBF. Perfusion studies were useful to discriminate granulomatous tissue enhancement from residual or recurrent tumor growth. Careful application of LITT may evolve as an alternative palliative concept for patients with end-stage high-grade cerebral gliomas reducing clinical symptoms from circumscribed areas of pathology.

Accelerated Fast Spin-Echo Magnetic Resonance Imaging of the Heart Using a Self-Calibrated Split-Echo Approach

PubMed Central

Klix, Sabrina; Hezel, Fabian; Fuchs, Katharina; Ruff, Jan; Dieringer, Matthias A.; Niendorf, Thoralf

2014-01-01

Purpose Design, validation and application of an accelerated fast spin-echo (FSE) variant that uses a split-echo approach for self-calibrated parallel imaging. Methods For self-calibrated, split-echo FSE (SCSE-FSE), extra displacement gradients were incorporated into FSE to decompose odd and even echo groups which were independently phase encoded to derive coil sensitivity maps, and to generate undersampled data (reduction factor up to R = 3). Reference and undersampled data were acquired simultaneously. SENSE reconstruction was employed. Results The feasibility of SCSE-FSE was demonstrated in phantom studies. Point spread function performance of SCSE-FSE was found to be competitive with traditional FSE variants. The immunity of SCSE-FSE for motion induced mis-registration between reference and undersampled data was shown using a dynamic left ventricular model and cardiac imaging. The applicability of black blood prepared SCSE-FSE for cardiac imaging was demonstrated in healthy volunteers including accelerated multi-slice per breath-hold imaging and accelerated high spatial resolution imaging. Conclusion SCSE-FSE obviates the need of external reference scans for SENSE reconstructed parallel imaging with FSE. SCSE-FSE reduces the risk for mis-registration between reference scans and accelerated acquisitions. SCSE-FSE is feasible for imaging of the heart and of large cardiac vessels but also meets the needs of brain, abdominal and liver imaging. PMID:24728341

Modeling magnetization transfer effects of Q2TIPS bolus saturation in multi-TI pulsed arterial spin labeling.

PubMed

Petr, Jan; Schramm, Georg; Hofheinz, Frank; Langner, Jens; van den Hoff, Jörg

2014-10-01

To estimate the relaxation time changes during Q2TIPS bolus saturation caused by magnetization transfer effects and to propose and evaluate an extended model for perfusion quantification which takes this into account. Three multi inversion-time pulsed arterial spin labeling sequences with different bolus saturation duration were acquired for five healthy volunteers. Magnetization transfer exchange rates in tissue and blood were obtained from control image saturation recovery. Cerebral blood flow (CBF) obtained using the extended model and the standard model was compared. A decrease of obtained CBF of 6% (10%) was observed in grey matter when the duration of bolus saturation increased from 600 to 900 ms (1200 ms). This decrease was reduced to 1.6% (2.8%) when the extended quantification model was used. Compared with the extended model, the standard model underestimated CBF in grey matter by 9.7, 15.0, and 18.7% for saturation durations 600, 900, and 1200 ms, respectively. Results for simulated single inversion-time data showed 5-16% CBF underestimation depending on blood arrival time and bolus saturation duration. Magnetization transfer effects caused by bolus saturation pulses should not be ignored when performing quantification as they can cause appreciable underestimation of the CBF. Copyright © 2013 Wiley Periodicals, Inc.

Voxel-level comparison of arterial spin-labeled perfusion magnetic resonance imaging in adolescents with internet gaming addiction

PubMed Central

2013-01-01

Background Although recent studies have clearly demonstrated functional and structural abnormalities in adolescents with internet gaming addiction (IGA), less is known about how IGA affects perfusion in the human brain. We used pseudocontinuous arterial spin-labeling (ASL) perfusion functional magnetic resonance imaging (fMRI) to measure the effects of IGA on resting brain functions by comparing resting cerebral blood flow in adolescents with IGA and normal subjects. Methods Fifteen adolescents with IGA and 18 matched normal adolescents underwent structural and perfusion fMRI in the resting state. Direct subtraction, voxel-wise general linear modeling was performed to compare resting cerebral blood flow (CBF) between the 2 groups. Correlations were calculated between the mean CBF value in all clusters that survived AlphaSim correction and the Chen Internet Addiction Scale (CIAS) scores, Barratt Impulsiveness Scale-11 (BIS-11) scores, or hours of Internet use per week (hours) in the 15 subjects with IGA. Results Compared with control subjects, adolescents with IGA showed significantly higher global CBF in the left inferior temporal lobe/fusiform gyrus, left parahippocampal gyrus/amygdala, right medial frontal lobe/anterior cingulate cortex, left insula, right insula, right middle temporal gyrus, right precentral gyrus, left supplementary motor area, left cingulate gyrus, and right inferior parietal lobe. Lower CBF was found in the left middle temporal gyrus, left middle occipital gyrus, and right cingulate gyrus. There were no significant correlations between mean CBF values in all clusters that survived AlphaSim correction and CIAS or BIS-11 scores or hours of Internet use per week. Conclusions In this study, we used ASL perfusion fMRI and noninvasively quantified resting CBF to demonstrate that IGA alters the CBF distribution in the adolescent brain. The results support the hypothesis that IGA is a behavioral addiction that may share similar neurobiological abnormalities with other addictive disorders. PMID:23937918

Liver imaging at 3.0 T: diffusion-induced black-blood echo-planar imaging with large anatomic volumetric coverage as an alternative for specific absorption rate-intensive echo-train spin-echo sequences: feasibility study.

PubMed

van den Bos, Indra C; Hussain, Shahid M; Krestin, Gabriel P; Wielopolski, Piotr A

2008-07-01

Institutional Review Board approval and signed informed consent were obtained by all participants for an ongoing sequence optimization project at 3.0 T. The purpose of this study was to evaluate breath-hold diffusion-induced black-blood echo-planar imaging (BBEPI) as a potential alternative for specific absorption rate (SAR)-intensive spin-echo sequences, in particular, the fast spin-echo (FSE) sequences, at 3.0 T. Fourteen healthy volunteers (seven men, seven women; mean age +/- standard deviation, 32.7 years +/- 6.8) were imaged for this purpose. Liver coverage (20 cm, z-axis) was always performed in one 25-second breath hold. Imaging parameters were varied interactively with regard to echo time, diffusion b value, and voxel size. Images were evaluated and compared with fat-suppressed T2-weighted FSE images for image quality, liver delineation, geometric distortions, fat suppression, suppression of the blood signal, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR). An optimized short- (25 msec) and long-echo (80 msec) BBEPI provided full anatomic, single breath-hold liver coverage (100 and 50 sections, respectively), with resulting voxel sizes of 3.3 x 2.7 x 2.0 mm and 3.3 x 2.7 x 4.0 mm, respectively. Repetition time was 6300 msec, matrix size was 160 x 192, and an acceleration factor of 2.00 was used. b Values of more than 20 sec/mm(2) showed better suppression of the blood signal but b values of 10 sec/mm(2) provided improved volume coverage and signal consistency. Compared with fat-suppressed T2-weighted FSE, the optimized BBEPI sequence provided (a) comparable image quality and liver delineation, (b) acceptable geometric distortions, (c) improved suppression of fat and blood signals, and (d) high CNR and SNR. BBEPI is feasible for fast, low-SAR, thin-section morphologic imaging of the entire liver in a single breath hold at 3.0 T. (c) RSNA, 2008.

Arterial Spin Labeling Perfusion Magnetic Resonance Image with Dual Postlabeling Delay: A Correlative Study with Acetazolamide Loading (123)I-Iodoamphetamine Single-Photon Emission Computed Tomography.

PubMed

Haga, Sei; Morioka, Takato; Shimogawa, Takafumi; Akiyama, Tomoaki; Murao, Kei; Kanazawa, Yuka; Sayama, Tetsuro; Arakawa, Shuji

2016-01-01

Perfusion magnetic resonance image with arterial spin labeling (ASL) provides a completely noninvasive measurement of cerebral blood flow (CBF). However, arterial transient times can have a marked effect on the ASL signal. For example, a single postlabeling delay (PLD) of 1.5 seconds underestimates the slowly streaming collateral pathways that maintain the cerebrovascular reserve (CVR). To overcome this limitation, we developed a dual PLD method. A dual PLD method of 1.5  and 2.5 seconds was compared with (123)I-iodoamphetamine single-photon emission computed tomography with acetazolamide loading to assess CVR in 10 patients with steno-occlusive cerebrovascular disease. In 5 cases (Group A), dual PLD-ASL demonstrated low CBF with 1.5-second PLD in the target area, whereas CBF was improved with 2.5-second PLD. In the other 5 cases (Group B), dual PLD-ASL depicted low CBF with 1.5-second PLD, and no improvement in CBF with 2.5-second PLD in the target area was observed. On single-photon emission computed tomography, CVR was maintained in Group A but decreased in Group B. Although dual PLD methods may not be a completely alternative test for (123)I-iodoamphetamine single-photon emission computed tomography with acetazolamide loading, it is a feasible, simple, noninvasive, and repeatable technique for assessing CVR, even when employed in a routine clinical setting. Copyright © 2015 National Stroke Association. Published by Elsevier Inc. All rights reserved.

Cerebral blood flow changes in hemodialysis and peritoneal dialysis patients: an arterial-spin labeling MR imaging.

PubMed

Jiang, Xiao Lu; Wen, Ji Qiu; Zhang, Long Jiang; Zheng, Gang; Li, Xue; Zhang, Zhe; Liu, Ya; Zheng, Li Juan; Wu, Long; Chen, Hui Juan; Kong, Xiang; Luo, Song; Lu, Guang Ming; Ji, Xue Man; Zhang, Zong Jun

2016-08-01

We used arterial-spin labeling (ASL) MR imaging, a non-invasive technique to evaluate cerebral blood flow (CBF) changes in patients with end-stage renal disease (ESRD) undergoing peritoneal dialysis (PD) and hemodialysis (HD), and nondialysis ESRD patients compared with healthy cohort. Ninety seven ESRD patients including 32 PD patients (20 male, 12 female; mean age 33 ± 8 years), 33 HD patients (22 male, 11 female; mean age 33 ± 8 years) and 32 nondialysis patients (20 male, 12 female; mean age 35 ± 7 years) and 31 age- and gender-matched healthy controls (20 male, 11 female; mean age 32 ± 8 years) were included in this study. All subjects underwent ASL MR imaging, neuropsychologic tests, and ESRD patients underwent laboratory testing. CBF values were compared among PD, HD, nondialysis patients and control groups. Correlation analysis and multiple regression analysis were performed to investigate the association between CBF values and hemoglobin, neuropsychologic test results, serum creatinine, urea levels, disease duration, and dialysis duration. Elevated CBFs of whole brain region, gray matter, and white matter were found in all ESRD patient groups compared with healthy controls (all P < 0.001). However, compared with non-dialysis ESRD patients, both PD and HD patients had widespread regional CBF decline mainly in bilateral frontal and anterior cingulate cortices. There were no differences for CBF between PD and HD patient groups. Negative correlations were observed between mean CBFs of whole brain region, gray matter, and white matter and the hemoglobin level in all ESRD patients. Multiple linear regression showed elevated CBF of multiple brain areas correlated with some neuropsychological tests in ESRD patients (all P < 0.001, AlphaSim corrected), but the association was not present or shrank after adjusting hemoglobin level. This study found that mean CBF was predominantly increased in patients with ESRD, which correlated with their hemoglobin level and neurocognitive disorders. There were no differences of CBF change and cognitive function between PD and HD ESRD patients with long-term treatment. The degree of anemia may be a predominant risk factor for cognitive impairment in these ESRD patients.

Differentiation of Glioblastoma from Brain Metastasis: Qualitative and Quantitative Analysis Using Arterial Spin Labeling MR Imaging.

PubMed

Sunwoo, Leonard; Yun, Tae Jin; You, Sung-Hye; Yoo, Roh-Eul; Kang, Koung Mi; Choi, Seung Hong; Kim, Ji-Hoon; Sohn, Chul-Ho; Park, Sun-Won; Jung, Cheolkyu; Park, Chul-Kee

2016-01-01

To evaluate the diagnostic performance of cerebral blood flow (CBF) by using arterial spin labeling (ASL) perfusion magnetic resonance (MR) imaging to differentiate glioblastoma (GBM) from brain metastasis. The institutional review board of our hospital approved this retrospective study. The study population consisted of 128 consecutive patients who underwent surgical resection and were diagnosed as either GBM (n = 89) or brain metastasis (n = 39). All participants underwent preoperative MR imaging including ASL. For qualitative analysis, the tumors were visually graded into five categories based on ASL-CBF maps by two blinded reviewers. For quantitative analysis, the reviewers drew regions of interest (ROIs) on ASL-CBF maps upon the most hyperperfused portion within the tumor and upon peritumoral T2 hyperintensity area. Signal intensities of intratumoral and peritumoral ROIs for each subject were normalized by dividing the values by those of contralateral normal gray matter (nCBFintratumoral and nCBFperitumoral, respectively). Visual grading scales and quantitative parameters between GBM and brain metastasis were compared. In addition, the area under the receiver-operating characteristic curve was used to evaluate the diagnostic performance of ASL-driven CBF to differentiate GBM from brain metastasis. For qualitative analysis, GBM group showed significantly higher grade compared to metastasis group (p = 0.001). For quantitative analysis, both nCBFintratumoral and nCBFperitumoral in GBM were significantly higher than those in metastasis (both p < 0.001). The areas under the curve were 0.677, 0.714, and 0.835 for visual grading, nCBFintratumoral, and nCBFperitumoral, respectively (all p < 0.001). ASL perfusion MR imaging can aid in the differentiation of GBM from brain metastasis.

Model-free arterial spin labelling for cerebral blood flow quantification: introduction of regional arterial input functions identified by factor analysis.

PubMed

Knutsson, Linda; Bloch, Karin Markenroth; Holtås, Stig; Wirestam, Ronnie; Ståhlberg, Freddy

2008-05-01

To identify regional arterial input functions (AIFs) using factor analysis of dynamic studies (FADS) when quantification of perfusion is performed using model-free arterial spin labelling. Five healthy volunteers and one patient were examined on a 3-T Philips unit using quantitative STAR labelling of arterial regions (QUASAR). Two sets of images were retrieved, one where the arterial signal had been crushed and another where it was retained. FADS was applied to the arterial signal curves to acquire the AIFs. Perfusion maps were obtained using block-circulant SVD deconvolution and regional AIFs obtained by FADS. In the volunteers, the ASL experiment was repeated within 24 h. The patient was also examined using dynamic susceptibility contrast MRI. In the healthy volunteers, CBF was 64+/-10 ml/[min 100 g] (mean+/-S.D.) in GM and 24+/-4 ml/[min 100 g] in WM, while the mean aBV was 0.94% in GM and 0.25% in WM. Good CBF image quality and reasonable quantitative CBF values were obtained using the combined QUASAR/FADS technique. We conclude that FADS may be a useful supplement in the evaluation of ASL data using QUASAR.

Evaluation of the Chondromalacia Patella Using a Microscopy Coil: Comparison of the Two-Dimensional Fast Spin Echo Techniques and the Three-Dimensional Fast Field Echo Techniques

PubMed Central

Kim, Hyun-joo; Kang, Chang Ho; Ryu, Jeong Ah; Shin, Myung Jin; Cho, Kyung-Ja; Cho, Woo Shin

2011-01-01

Objective We wanted to compare the two-dimensional (2D) fast spin echo (FSE) techniques and the three-dimensional (3D) fast field echo techniques for the evaluation of the chondromalacia patella using a microscopy coil. Materials and Methods Twenty five patients who underwent total knee arthroplasty were included in this study. Preoperative MRI evaluation of the patella was performed using a microscopy coil (47 mm). The proton density-weighted fast spin echo images (PD), the fat-suppressed PD images (FS-PD), the intermediate weighted-fat suppressed fast spin echo images (iw-FS-FSE), the 3D balanced-fast field echo images (B-FFE), the 3D water selective cartilage scan (WATS-c) and the 3D water selective fluid scan (WATS-f) were obtained on a 1.5T MRI scanner. The patellar cartilage was evaluated in nine areas: the superior, middle and the inferior portions that were subdivided into the medial, central and lateral facets in a total of 215 areas. Employing the Noyes grading system, the MRI grade 0-I, II and III lesions were compared using the gross and microscopic findings. The sensitivity, specificity and accuracy were evaluated for each sequence. The significance of the differences for the individual sequences was calculated using the McNemar test. Results The gross and microscopic findings demonstrated 167 grade 0-I lesions, 40 grade II lesions and eight grade III lesions. Iw-FS-FSE had the highest accuracy (sensitivity/specificity/accuracy = 88%/98%/96%), followed by FS-PD (78%/98%/93%, respectively), PD (76%/98%/93%, respectively), B-FFE (71%/100%/93%, respectively), WATS-c (67%/100%/92%, respectively) and WATS-f (58%/99%/89%, respectively). There were statistically significant differences for the iw-FS-FSE and WATS-f and for the PD-FS and WATS-f (p < 0.01). Conclusion The iw-FS-FSE images obtained with a microscopy coil show best diagnostic performance among the 2D and 3D GRE images for evaluating the chondromalacia patella. PMID:21228943

Evaluation of the chondromalacia patella using a microscopy coil: comparison of the two-dimensional fast spin echo techniques and the three-dimensional fast field echo techniques.

PubMed

Kim, Hyun-joo; Lee, Sang Hoon; Kang, Chang Ho; Ryu, Jeong Ah; Shin, Myung Jin; Cho, Kyung-Ja; Cho, Woo Shin

2011-01-01

We wanted to compare the two-dimensional (2D) fast spin echo (FSE) techniques and the three-dimensional (3D) fast field echo techniques for the evaluation of the chondromalacia patella using a microscopy coil. Twenty five patients who underwent total knee arthroplasty were included in this study. Preoperative MRI evaluation of the patella was performed using a microscopy coil (47 mm). The proton density-weighted fast spin echo images (PD), the fat-suppressed PD images (FS-PD), the intermediate weighted-fat suppressed fast spin echo images (iw-FS-FSE), the 3D balanced-fast field echo images (B-FFE), the 3D water selective cartilage scan (WATS-c) and the 3D water selective fluid scan (WATS-f) were obtained on a 1.5T MRI scanner. The patellar cartilage was evaluated in nine areas: the superior, middle and the inferior portions that were subdivided into the medial, central and lateral facets in a total of 215 areas. Employing the Noyes grading system, the MRI grade 0-I, II and III lesions were compared using the gross and microscopic findings. The sensitivity, specificity and accuracy were evaluated for each sequence. The significance of the differences for the individual sequences was calculated using the McNemar test. The gross and microscopic findings demonstrated 167 grade 0-I lesions, 40 grade II lesions and eight grade III lesions. Iw-FS-FSE had the highest accuracy (sensitivity/specificity/accuracy = 88%/98%/96%), followed by FS-PD (78%/98%/93%, respectively), PD (76%/98%/93%, respectively), B-FFE (71%/100%/93%, respectively), WATS-c (67%/100%/92%, respectively) and WATS-f (58%/99%/89%, respectively). There were statistically significant differences for the iw-FS-FSE and WATS-f and for the PD-FS and WATS-f (p < 0.01). The iw-FS-FSE images obtained with a microscopy coil show best diagnostic performance among the 2D and 3D GRE images for evaluating the chondromalacia patella.

A model-based reconstruction for undersampled radial spin echo DTI with variational penalties on the diffusion tensor

PubMed Central

Knoll, Florian; Raya, José G; Halloran, Rafael O; Baete, Steven; Sigmund, Eric; Bammer, Roland; Block, Tobias; Otazo, Ricardo; Sodickson, Daniel K

2015-01-01

Radial spin echo diffusion imaging allows motion-robust imaging of tissues with very low T2 values like articular cartilage with high spatial resolution and signal-to-noise ratio (SNR). However, in vivo measurements are challenging due to the significantly slower data acquisition speed of spin-echo sequences and the less efficient k-space coverage of radial sampling, which raises the demand for accelerated protocols by means of undersampling. This work introduces a new reconstruction approach for undersampled DTI. A model-based reconstruction implicitly exploits redundancies in the diffusion weighted images by reducing the number of unknowns in the optimization problem and compressed sensing is performed directly in the target quantitative domain by imposing a Total Variation (TV) constraint on the elements of the diffusion tensor. Experiments were performed for an anisotropic phantom and the knee and brain of healthy volunteers (3 and 2 volunteers, respectively). Evaluation of the new approach was conducted by comparing the results to reconstructions performed with gridding, combined parallel imaging and compressed sensing, and a recently proposed model-based approach. The experiments demonstrated improvement in terms of reduction of noise and streaking artifacts in the quantitative parameter maps as well as a reduction of angular dispersion of the primary eigenvector when using the proposed method, without introducing systematic errors into the maps. This may enable an essential reduction of the acquisition time in radial spin echo diffusion tensor imaging without degrading parameter quantification and/or SNR. PMID:25594167

Spin echo SPI methods for quantitative analysis of fluids in porous media.

PubMed

Li, Linqing; Han, Hui; Balcom, Bruce J

2009-06-01

Fluid density imaging is highly desirable in a wide variety of porous media measurements. The SPRITE class of MRI methods has proven to be robust and general in their ability to generate density images in porous media, however the short encoding times required, with correspondingly high magnetic field gradient strengths and filter widths, and low flip angle RF pulses, yield sub-optimal S/N images, especially at low static field strength. This paper explores two implementations of pure phase encode spin echo 1D imaging, with application to a proposed new petroleum reservoir core analysis measurement. In the first implementation of the pulse sequence, we modify the spin echo single point imaging (SE-SPI) technique to acquire the k-space origin data point, with a near zero evolution time, from the free induction decay (FID) following a 90 degrees excitation pulse. Subsequent k-space data points are acquired by separately phase encoding individual echoes in a multi-echo acquisition. T(2) attenuation of the echo train yields an image convolution which causes blurring. The T(2) blur effect is moderate for porous media with T(2) lifetime distributions longer than 5 ms. As a robust, high S/N, and fast 1D imaging method, this method will be highly complementary to SPRITE techniques for the quantitative analysis of fluid content in porous media. In the second implementation of the SE-SPI pulse sequence, modification of the basic measurement permits fast determination of spatially resolved T(2) distributions in porous media through separately phase encoding each echo in a multi-echo CPMG pulse train. An individual T(2) weighted image may be acquired from each echo. The echo time (TE) of each T(2) weighted image may be reduced to 500 micros or less. These profiles can be fit to extract a T(2) distribution from each pixel employing a variety of standard inverse Laplace transform methods. Fluid content 1D images are produced as an essential by product of determining the spatially resolved T(2) distribution. These 1D images do not suffer from a T(2) related blurring. The above SE-SPI measurements are combined to generate 1D images of the local saturation and T(2) distribution as a function of saturation, upon centrifugation of petroleum reservoir core samples. The logarithm mean T(2) is observed to shift linearly with water saturation. This new reservoir core analysis measurement may provide a valuable calibration of the Coates equation for irreducible water saturation, which has been widely implemented in NMR well logging measurements.

Simultaneous dual contrast weighting using double echo rapid acquisition with relaxation enhancement (RARE) imaging.

PubMed

Fuchs, Katharina; Hezel, Fabian; Klix, Sabrina; Mekle, Ralf; Wuerfel, Jens; Niendorf, Thoralf

2014-12-01

This work proposes a dual contrast rapid acquisition with relaxation enhancement (RARE) variant (2in1-RARE), which provides simultaneous proton density (PD) and T2 * contrast in a single acquisition. The underlying concept of 2in1-RARE is the strict separation of spin echoes and stimulated echoes. This approach offers independent weighting of spin echoes and stimulated echoes. 2in1-RARE was evaluated in phantoms including signal-to-noise ratio (SNR) and point spread function assessment. 2in1-RARE was benchmarked versus coherent RARE and a split-echo RARE variant. The applicability of 2in1-RARE for brain imaging was demonstrated in a small cohort of healthy subjects (n = 10) and, exemplary, a multiple sclerosis patient at 3 Tesla as a precursor to a broader clinical study. 2in1-RARE enables the simultaneous acquisition of dual contrast weighted images without any significant image degradation and without sacrificing SNR versus split-echo RARE. This translates into a factor of two speed gain over multi-contrast, sequential split-echo RARE. A 15% broadening of the point spread function was observed in 2in1-RARE. T1 relaxation effects during the mixing time can be neglected for brain tissue. 2in1-RARE offers simultaneous acquisition of images of anatomical (PD) and functional (T2 *) contrast. It presents an alternative to address scan time constraints frequently encountered during sequential acquisition of T2 * or PD-weighted RARE. © 2013 Wiley Periodicals, Inc.

Noncontrast Peripheral MRA with Spiral Echo Train Imaging

PubMed Central

Fielden, Samuel W.; Mugler, John P.; Hagspiel, Klaus D.; Norton, Patrick T.; Kramer, Christopher M.; Meyer, Craig H.

2015-01-01

Purpose To develop a spin echo train sequence with spiral readout gradients with improved artery–vein contrast for noncontrast angiography. Theory Venous T2 becomes shorter as the echo spacing is increased in echo train sequences, improving contrast. Spiral acquisitions, due to their data collection efficiency, facilitate long echo spacings without increasing scan times. Methods Bloch equation simulations were performed to determine optimal sequence parameters, and the sequence was applied in five volunteers. In two volunteers, the sequence was performed with a range of echo times and echo spacings to compare with the theoretical contrast behavior. A Cartesian version of the sequence was used to compare contrast appearance with the spiral sequence. Additionally, spiral parallel imaging was optionally used to improve image resolution. Results In vivo, artery–vein contrast properties followed the general shape predicted by simulations, and good results were obtained in all stations. Compared with a Cartesian implementation, the spiral sequence had superior artery–vein contrast, better spatial resolution (1.2 mm2 versus 1.5 mm2), and was acquired in less time (1.4 min versus 7.5 min). Conclusion The spiral spin echo train sequence can be used for flow-independent angiography to generate threedimensional angiograms of the periphery quickly and without the use of contrast agents. PMID:24753164

Noncontrast peripheral MRA with spiral echo train imaging.

PubMed

Fielden, Samuel W; Mugler, John P; Hagspiel, Klaus D; Norton, Patrick T; Kramer, Christopher M; Meyer, Craig H

2015-03-01

To develop a spin echo train sequence with spiral readout gradients with improved artery-vein contrast for noncontrast angiography. Venous T2 becomes shorter as the echo spacing is increased in echo train sequences, improving contrast. Spiral acquisitions, due to their data collection efficiency, facilitate long echo spacings without increasing scan times. Bloch equation simulations were performed to determine optimal sequence parameters, and the sequence was applied in five volunteers. In two volunteers, the sequence was performed with a range of echo times and echo spacings to compare with the theoretical contrast behavior. A Cartesian version of the sequence was used to compare contrast appearance with the spiral sequence. Additionally, spiral parallel imaging was optionally used to improve image resolution. In vivo, artery-vein contrast properties followed the general shape predicted by simulations, and good results were obtained in all stations. Compared with a Cartesian implementation, the spiral sequence had superior artery-vein contrast, better spatial resolution (1.2 mm(2) versus 1.5 mm(2) ), and was acquired in less time (1.4 min versus 7.5 min). The spiral spin echo train sequence can be used for flow-independent angiography to generate three-dimensional angiograms of the periphery quickly and without the use of contrast agents. © 2014 Wiley Periodicals, Inc.

Brainstem Cavernous Angioma

MedlinePlus

... echo” (as opposed to spin-echo or proton beam) imaging. Gradient-echo MRI is most efficient at ... radiosurgery for cavernous malformations: Kjellberg's experience with proton beam therapy in 98 cases at the Harvard Cyclotron. ...

Application of Double Spin-Echo Spiral Chemical Shift Imaging to Rapid Metabolic Mapping of Hyperpolarized [1-13C]-Pyruvate

PubMed Central

Josan, Sonal; Yen, Yi-Fen; Hurd, Ralph; Pfefferbaum, Adolf; Spielman, Daniel; Mayer, Dirk

2011-01-01

Undersampled spiral CSI (spCSI) using a free induction decay (FID) acquisition allows sub-second metabolic imaging of hyperpolarized 13C. Phase correction of the FID acquisition can be difficult, especially with contributions from aliased out-of-phase peaks. This work extends the spCSI sequence by incorporating double spin-echo radiofrequency (RF) pulses to eliminate the need for phase correction and obtain high quality spectra in magnitude mode. The sequence also provides an added benefit of attenuating signal from flowing spins, which can otherwise contaminate signal in the organ of interest. The refocusing pulses can potentially lead to a loss of hyperpolarized magnetization in dynamic imaging due to flow of spins through the fringe field of the RF coil, where the refocusing pulses fail to provide complete refocusing. Care must be taken for dynamic imaging to ensure that the spins remain within the B1-homogeneous sensitive volume of the RF coil. PMID:21316280

Chondromalacia patellae: an in vitro study. Comparison of MR criteria with histologic and macroscopic findings.

PubMed

van Leersum, M; Schweitzer, M E; Gannon, F; Finkel, G; Vinitski, S; Mitchell, D G

1996-11-01

To develop MR criteria for grades of chondromalacia patellae and to assess the accuracy of these grades. Fat-suppressed T2-weighted double-echo, fat-suppressed T2-weighted fast spin echo, fat-suppressed T1-weighted, and gradient echo sequences were performed at 1.5 T for the evaluation of chondromalacia. A total of 1000 MR, 200 histologic, and 200 surface locations were graded for chondromalacia and statistically compared. Compared with gross inspection as well as with histology the most accurate sequences were fat-suppressed T2-weighted conventional spin echo and fat suppressed T2-weighted fast spin echo, although the T1-weighted and proton density images also correlated well. The most accurate MR criteria applied to the severe grades of chondromalacia, with less accurate results for lesser grades. This study demonstrates that fat-suppressed routine T2-weighted and fast spin echo T2-weighted sequences seem to be more accurate than proton density, T1-weighted, and gradient echo sequences in grading chondromalacia. Good histologic and macroscopic correlation was seen in more severe grades of chondromalacia, but problems remain for the early grades in all sequences studied.

Reduced Dynamic Coupling Between Spontaneous BOLD-CBF Fluctuations in Older Adults: A Dual-Echo pCASL Study.

PubMed

Chiacchiaretta, Piero; Cerritelli, Francesco; Bubbico, Giovanna; Perrucci, Mauro Gianni; Ferretti, Antonio

2018-01-01

Measurement of the dynamic coupling between spontaneous Blood Oxygenation Level Dependent (BOLD) and cerebral blood flow (CBF) fluctuations has been recently proposed as a method to probe resting-state brain physiology. Here we investigated how the dynamic BOLD-CBF coupling during resting-state is affected by aging. Fifteen young subjects and 17 healthy elderlies were studied using a dual-echo pCASL sequence. We found that the dynamic BOLD-CBF coupling was markedly reduced in elderlies, in particular in the left supramarginal gyrus, an area known to be involved in verbal working memory and episodic memory. Moreover, correcting for temporal shift between BOLD and CBF timecourses resulted in an increased correlation of the two signals for both groups, but with a larger increase for elderlies. However, even after temporal shift correction, a significantly decreased correlation was still observed for elderlies in the left supramarginal gyrus, indicating that the age-related dynamic BOLD-CBF uncoupling in this region is more pronounced and can be only partially explained with a simple time-shift between the two signals. Interestingly, these results were observed in a group of elderlies with normal cognitive functions, suggesting that the study of dynamic BOLD-CBF coupling during resting-state is a promising technique, potentially able to provide early biomarkers of functional changes in the aging brain.

The value of non-echo planar HASTE diffusion-weighted MR imaging in the detection, localisation and prediction of extent of postoperative cholesteatoma.

PubMed

Khemani, S; Lingam, R K; Kalan, A; Singh, A

2011-08-01

To evaluate the diagnostic performance of half-Fourier-acquisition single-shot turbo-spin-echo (HASTE) diffusion-weighted magnetic resonance imaging in the detection, localisation and prediction of extent of cholesteatoma following canal wall up mastoid surgery. Prospective blinded observational study. University affiliated teaching hospital. Forty-eight patients undergoing second-look surgery after previous canal wall up mastoid surgery for primary acquired cholesteatoma. All patients underwent non-echo planar HASTE diffusion-weighted imaging prior to being offered 'second-look' surgery. Radiological findings were correlated with second-look intra-operative findings in 38 cases with regard to presence, location and maximum dimensions of cholesteatoma. Half-Fourier-acquisition single-shot turbo-spin-echo diffusion-weighted imaging accurately predicted the presence of cholesteatoma in 23 of 28 cases, and it correctly excluded in nine of 10 cases. Five false negatives were caused by keratin pearls of <2 mm and in one case 5 mm. Overall sensitivity and specificity for detection of cholesteatoma were 82% (95% confidence interval [CI] 62-94%) and 90% (CI 55-100%), respectively. Positive predictive value and negative predictive value were 96% (CI 79-100%) and 64% (CI 35-87%), respectively. Overall accuracy for detection of cholesteatoma was 84% (CI 69-94%). Half-Fourier-acquisition single-shot turbo-spin-echo diffusion-weighted imaging has good performance in localising cholesteatoma to a number of anatomical sub-sites within the middle ear and mastoid (sensitivity ranging from 75% to 88% and specificity ranging from 94% to 100%). There was no statistically significant difference in the size of cholesteatoma detected radiologically and that found during surgery (paired t-test, P = 0.16). However, analysis of size agreement suggests possible radiological underestimation of size when using HASTE diffusion-weighted imaging (mean difference -0.6 mm, CI -5.3 to 4.6 mm). Half-Fourier-acquisition single-shot turbo-spin-echo diffusion-weighted imaging performs reasonably well in predicting the presence and location of postoperative cholesteatoma but may miss small foci of disease and may underestimate the true size of cholesteatoma. © 2011 Blackwell Publishing Ltd.

Can a single-shot black-blood T2-weighted spin-echo echo-planar imaging sequence with sensitivity encoding replace the respiratory-triggered turbo spin-echo sequence for the liver? An optimization and feasibility study.

PubMed

Hussain, Shahid M; De Becker, Jan; Hop, Wim C J; Dwarkasing, Soendersing; Wielopolski, Piotr A

2005-03-01

To optimize and assess the feasibility of a single-shot black-blood T2-weighted spin-echo echo-planar imaging (SSBB-EPI) sequence for MRI of the liver using sensitivity encoding (SENSE), and compare the results with those obtained with a T2-weighted turbo spin-echo (TSE) sequence. Six volunteers and 16 patients were scanned at 1.5T (Philips Intera). In the volunteer study, we optimized the SSBB-EPI sequence by interactively changing the parameters (i.e., the resolution, echo time (TE), diffusion weighting with low b-values, and polarity of the phase-encoding gradient) with regard to distortion, suppression of the blood signal, and sensitivity to motion. The influence of each change was assessed. The optimized SSBB-EPI sequence was applied in patients (N = 16). A number of items, including the overall image quality (on a scale of 1-5), were used for graded evaluation. In addition, the signal-to-noise ratio (SNR) of the liver was calculated. Statistical analysis was carried out with the use of Wilcoxon's signed rank test for comparison of the SSBB-EPI and TSE sequences, with P = 0.05 considered the limit for significance. The SSBB-EPI sequence was improved by the following steps: 1) less frequency points than phase-encoding steps, 2) a b-factor of 20, and 3) a reversed polarity of the phase-encoding gradient. In patients, the mean overall image quality score for the optimized SSBB-EPI (3.5 (range: 1-4)) and TSE (3.6 (range: 3-4)), and the SNR of the liver on SSBB-EPI (mean +/- SD = 7.6 +/- 4.0) and TSE (8.9 +/- 4.6) were not significantly different (P > .05). Optimized SSBB-EPI with SENSE proved to be feasible in patients, and the overall image quality and SNR of the liver were comparable to those achieved with the standard respiratory-triggered T2-weighted TSE sequence. (c) 2005 Wiley-Liss, Inc.

High-speed multislice T1 mapping using inversion-recovery echo-planar imaging.

PubMed

Ordidge, R J; Gibbs, P; Chapman, B; Stehling, M K; Mansfield, P

1990-11-01

Tissue contrast in MR images is a strong function of spin-lattice (T1) and spin-spin (T2) relaxation times. However, the T1 relaxation time is rarely quantified because of the long scan time required to produce an accurate T1 map of the subject. In a standard 2D FT technique, this procedure may take up to 30 min. Modifications of the echo-planar imaging (EPI) technique which incorporate the principle of inversion recovery (IR) enable multislice T1 maps to be produced in total scan times varying from a few seconds up to a minute. Using IR-EPI, rapid quantification of T1 values may thus lead to better discrimination between tissue types in an acceptable scan time.

Contrast-enhanced Magnetic Resonance Imaging of Pelvic Bone Metastases at 3.0 T: Comparison Between 3-dimensional T1-weighted CAIPIRINHA-VIBE Sequence and 2-dimensional T1-weighted Turbo Spin-Echo Sequence.

PubMed

Yoon, Min A; Hong, Suk-Joo; Lee, Kyu-Chong; Lee, Chang Hee

2018-06-12

This study aimed to compare 3-dimensional T1-weighted gradient-echo sequence (CAIPIRINHA-volumetric interpolated breath-hold examination [VIBE]) with 2-dimensional T1-weighted turbo spin-echo sequence for contrast-enhanced magnetic resonance imaging (MRI) of pelvic bone metastases at 3.0 T. Thirty-one contrast-enhanced MRIs of pelvic bone metastases were included. Two contrast-enhanced sequences were evaluated for the following parameters: overall image quality, sharpness of pelvic bone, iliac vessel clarity, artifact severity, and conspicuity and edge sharpness of the smallest metastases. Quantitative analysis was performed by calculating signal-to-noise ratio and contrast-to-noise ratio of the smallest metastases. Significant differences between the 2 sequences were assessed. CAIPIRINHA-VIBE had higher scores for overall image quality, pelvic bone sharpness, iliac vessel clarity, and edge sharpness of the metastatic lesions, and had less artifacts (all P < 0.05). There was no significant difference in conspicuity, signal-to-noise ratio, or contrast-to-noise ratio of the smallest metastases (P > 0.05). Our results suggest that CAIPIRINHA-VIBE may be superior to turbo spin-echo for contrast-enhanced MRI of pelvic bone metastases at 3.0 T.

Comparative study of pulsed-continuous arterial spin labeling and dynamic susceptibility contrast imaging by histogram analysis in evaluation of glial tumors.

PubMed

Arisawa, Atsuko; Watanabe, Yoshiyuki; Tanaka, Hisashi; Takahashi, Hiroto; Matsuo, Chisato; Fujiwara, Takuya; Fujiwara, Masahiro; Fujimoto, Yasunori; Tomiyama, Noriyuki

2018-06-01

Arterial spin labeling (ASL) is a non-invasive perfusion technique that may be an alternative to dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) for assessment of brain tumors. To our knowledge, there have been no reports on histogram analysis of ASL. The purpose of this study was to determine whether ASL is comparable with DSC-MRI in terms of differentiating high-grade and low-grade gliomas by evaluating the histogram analysis of cerebral blood flow (CBF) in the entire tumor. Thirty-four patients with pathologically proven glioma underwent ASL and DSC-MRI. High-signal areas on contrast-enhanced T 1 -weighted images or high-intensity areas on fluid-attenuated inversion recovery images were designated as the volumes of interest (VOIs). ASL-CBF, DSC-CBF, and DSC-cerebral blood volume maps were constructed and co-registered to the VOI. Perfusion histogram analyses of the whole VOI and statistical analyses were performed to compare the ASL and DSC images. There was no significant difference in the mean values for any of the histogram metrics in both of the low-grade gliomas (n = 15) and the high-grade gliomas (n = 19). Strong correlations were seen in the 75th percentile, mean, median, and standard deviation values between the ASL and DSC images. The area under the curve values tended to be greater for the DSC images than for the ASL images. DSC-MRI is superior to ASL for distinguishing high-grade from low-grade glioma. ASL could be an alternative evaluation method when DSC-MRI cannot be used, e.g., in patients with renal failure, those in whom repeated examination is required, and in children.

Frequency bandwidth extension by use of multiple Zeeman field offsets for electron spin-echo EPR oxygen imaging of large objects

PubMed Central

Seifi, Payam; Epel, Boris; Sundramoorthy, Subramanian V.; Mailer, Colin; Halpern, Howard J.

2011-01-01

Purpose: Electron spin-echo (ESE) oxygen imaging is a new and evolving electron paramagnetic resonance (EPR) imaging (EPRI) modality that is useful for physiological in vivo applications, such as EPR oxygen imaging (EPROI), with potential application to imaging of multicentimeter objects as large as human tumors. A present limitation on the size of the object to be imaged at a given resolution is the frequency bandwidth of the system, since the location is encoded as a frequency offset in ESE imaging. The authors’ aim in this study was to demonstrate the object size advantage of the multioffset bandwidth extension technique.Methods: The multiple-stepped Zeeman field offset (or simply multi-B) technique was used for imaging of an 8.5-cm-long phantom containing a narrow single line triaryl methyl compound (trityl) solution at the 250 MHz imaging frequency. The image is compared to a standard single-field ESE image of the same phantom.Results: For the phantom used in this study, transverse relaxation (T2e) electron spin-echo (ESE) images from multi-B acquisition are more uniform, contain less prominent artifacts, and have a better signal to noise ratio (SNR) compared to single-field T2e images.Conclusions: The multi-B method is suitable for imaging of samples whose physical size restricts the applicability of the conventional single-field ESE imaging technique. PMID:21815379

Improved imaging of cochlear nerve hypoplasia using a 3-Tesla variable flip-angle turbo spin-echo sequence and a 7-cm surface coil.

PubMed

Giesemann, Anja M; Raab, Peter; Lyutenski, Stefan; Dettmer, Sabine; Bültmann, Eva; Frömke, Cornelia; Lenarz, Thomas; Lanfermann, Heinrich; Goetz, Friedrich

2014-03-01

Magnetic resonance imaging of the temporal bone has an important role in decision making with regard to cochlea implantation, especially in children with cochlear nerve deficiency. The purpose of this study was to evaluate the usefulness of the combination of an advanced high-resolution T2-weighted sequence with a surface coil in a 3-Tesla magnetic resonance imaging scanner in cases of suspected cochlear nerve aplasia. Prospective study. Seven patients with cochlear nerve hypoplasia or aplasia were prospectively examined using a high-resolution three-dimensional variable flip-angle turbo spin-echo sequence using a surface coil, and the images were compared with the same sequence in standard resolution using a standard head coil. Three neuroradiologists evaluated the magnetic resonance images independently, rating the visibility of the nerves in diagnosing hypoplasia or aplasia. Eight ears in seven patients with hypoplasia or aplasia of the cochlear nerve were examined. The average age was 2.7 years (range, 9 months-5 years). Seven ears had accompanying malformations. The inter-rater reliability in diagnosing hypoplasia or aplasia was greater using the high-resolution three-dimensional variable flip-angle turbo spin-echo sequence (fixed-marginal kappa: 0.64) than with the same sequence in lower resolution (fixed-marginal kappa: 0.06). Examining cases of suspected cochlear nerve aplasia using the high-resolution three-dimensional variable flip-angle turbo spin-echo sequence in combination with a surface coil shows significant improvement over standard methods. © 2013 The American Laryngological, Rhinological and Otological Society, Inc.

T2 shuffling: Sharp, multicontrast, volumetric fast spin-echo imaging.

PubMed

Tamir, Jonathan I; Uecker, Martin; Chen, Weitian; Lai, Peng; Alley, Marcus T; Vasanawala, Shreyas S; Lustig, Michael

2017-01-01

A new acquisition and reconstruction method called T 2 Shuffling is presented for volumetric fast spin-echo (three-dimensional [3D] FSE) imaging. T 2 Shuffling reduces blurring and recovers many images at multiple T 2 contrasts from a single acquisition at clinically feasible scan times (6-7 min). The parallel imaging forward model is modified to account for temporal signal relaxation during the echo train. Scan efficiency is improved by acquiring data during the transient signal decay and by increasing echo train lengths without loss in signal-to-noise ratio (SNR). By (1) randomly shuffling the phase encode view ordering, (2) constraining the temporal signal evolution to a low-dimensional subspace, and (3) promoting spatio-temporal correlations through locally low rank regularization, a time series of virtual echo time images is recovered from a single scan. A convex formulation is presented that is robust to partial voluming and radiofrequency field inhomogeneity. Retrospective undersampling and in vivo scans confirm the increase in sharpness afforded by T 2 Shuffling. Multiple image contrasts are recovered and used to highlight pathology in pediatric patients. A proof-of-principle method is integrated into a clinical musculoskeletal imaging workflow. The proposed T 2 Shuffling method improves the diagnostic utility of 3D FSE by reducing blurring and producing multiple image contrasts from a single scan. Magn Reson Med 77:180-195, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Measurement of OEF and absolute CMRO2: MRI-based methods using interleaved and combined hypercapnia and hyperoxia

PubMed Central

Wise, Richard G.; Harris, Ashley D.; Stone, Alan; Murphy, Kevin

2014-01-01

Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (FMRI) is most commonly used in a semi-quantitative manner to infer changes in brain activity. Despite the basis of the image contrast lying in the cerebral venous blood oxygenation level, quantification of absolute cerebral metabolic rate of oxygen consumption (CMRO2) has only recently been demonstrated. Here we examine two approaches to the calibration of FMRI signal to measure absolute CMRO2 using hypercapnic and hyperoxic respiratory challenges. The first approach is to apply hypercapnia and hyperoxia separately but interleaved in time and the second is a combined approach in which we apply hyperoxic challenges simultaneously with different levels of hypercapnia. Eleven healthy volunteers were studied at 3T using a dual gradient-echo spiral readout pulsed arterial spin labelling (ASL) imaging sequence. Respiratory challenges were conducted using an automated system of dynamic end-tidal forcing. A generalised BOLD signal model was applied, within a Bayesian estimation framework, that aims to explain the effects of modulation of CBF and arterial oxygen content to estimate venous deoxyhaemoglobin concentration ([dHb]0). Using CBF measurements combined with the estimated oxygen extraction fraction (OEF), absolute CMRO2 was calculated. The interleaved approach to hypercapnia and hyperoxia, as well as yielding estimates of CMRO2 and OEF demonstrated a significant increase in regional CBF, venous oxygen saturation (SvO2) (a decrease in OEF) and absolute CMRO2 in visual cortex in response to a continuous (20 minute) visual task, demonstrating the potential for the method in measuring long term changes in CMRO2. The combined approach to oxygen and carbon dioxide modulation, as well as taking less time to acquire data, yielded whole brain grey matter estimates of CMRO2 and OEF of 184±45 μmol/100g/min and 0.42±0.12 respectively, along with additional estimates of the vascular parameters α = 0.33±0.06, the exponent relating relative increases in CBF to CBV, and β = 1.35±0.13, the exponent relating deoxyhaemoglobin concentration to the relaxation rate R2*. Maps of cerebrovascular and cerebral metabolic parameters were also calculated. We show that combined modulation of oxygen and carbon dioxide can offer an experimentally more efficient approach to estimating OEF and absolute CMRO2 along with the additional vascular parameters that form an important part of the commonly used calibrated FMRI signal model. PMID:23769703

Altered Coupling Between Resting-State Cerebral Blood Flow and Functional Connectivity in Schizophrenia.

PubMed

Zhu, Jiajia; Zhuo, Chuanjun; Xu, Lixue; Liu, Feng; Qin, Wen; Yu, Chunshui

2017-10-21

Respective changes in resting-state cerebral blood flow (CBF) and functional connectivity in schizophrenia have been reported. However, their coupling alterations in schizophrenia remain largely unknown. 89 schizophrenia patients and 90 sex- and age-matched healthy controls underwent resting-state functional MRI to calculate functional connectivity strength (FCS) and arterial spin labeling imaging to compute CBF. The CBF-FCS coupling of the whole gray matter and the CBF/FCS ratio (the amount of blood supply per unit of connectivity strength) of each voxel were compared between the 2 groups. Whole gray matter CBF-FCS coupling was decreased in schizophrenia patients relative to healthy controls. In schizophrenia patients, the decreased CBF/FCS ratio was predominantly located in cognitive- and emotional-related brain regions, including the dorsolateral prefrontal cortex, insula, hippocampus and thalamus, whereas an increased CBF/FCS ratio was mainly identified in the sensorimotor regions, including the putamen, and sensorimotor, mid-cingulate and visual cortices. These findings suggest that the neurovascular decoupling in the brain may be a possible neuropathological mechanism of schizophrenia. © The Author 2017. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved. For permissions, please email: journals.permissions@oup.com

Regional cerebral blood flow and cerebrovascular reactivity in Alzheimer's disease and vascular dementia assessed by arterial spinlabeling magnetic resonance imaging.

PubMed

Gao, Yong-Zhe; Zhang, Jun-Jian; Liu, Hui; Wu, Guang-Yao; Xiong, Li; Shu, Min

2013-02-01

Hemodynamic disturbance in cerebral blood flow (CBF) is common in both Alzheimer's disease (AD) and vascular dementia (VaD).The aim of this study is to investigate the different patterns of regional cerebral blood flow (rCBF) change and cerebrovascular reactivity (CVR) in these two types of dementia. Mean flow velocity (MFV) of middle cerebral artery and rCBF were measured by Transcranial Doppler ultrasound (TCD) and arterial spin-labeling (ASL) magnetic resonance, separately. CVR was evaluated by MFV or rCBF change in response to 5% CO2 inhalation. The ASL results showed that, rCBF was significantly lower in both the bilateral frontal and temporal lobes in AD group and lower in left frontal and temporal white matter in patients with VaD. CVR calculated by rCBF was impaired more severely in bilateral frontal cortices in AD. Conversely, TCD tests failed to demonstrate significant difference in MFV and CVR between the two groups. It is concluded that the different patterns detected by ASL in resting rCBF change and cerebrovascular reactivity in response to carbogen inhalation may serve as a potential marker to distinguish AD and VaD.

Quantifying the test-retest reliability of cerebral blood flow measurements in a clinical model of on-going post-surgical pain: A study using pseudo-continuous arterial spin labelling.

PubMed

Hodkinson, Duncan J; Krause, Kristina; Khawaja, Nadine; Renton, Tara F; Huggins, John P; Vennart, William; Thacker, Michael A; Mehta, Mitul A; Zelaya, Fernando O; Williams, Steven C R; Howard, Matthew A

2013-01-01

Arterial spin labelling (ASL) is increasingly being applied to study the cerebral response to pain in both experimental human models and patients with persistent pain. Despite its advantages, scanning time and reliability remain important issues in the clinical applicability of ASL. Here we present the test-retest analysis of concurrent pseudo-continuous ASL (pCASL) and visual analogue scale (VAS), in a clinical model of on-going pain following third molar extraction (TME). Using ICC performance measures, we were able to quantify the reliability of the post-surgical pain state and ΔCBF (change in CBF), both at the group and individual case level. Within-subject, the inter- and intra-session reliability of the post-surgical pain state was ranked good-to-excellent (ICC > 0.6) across both pCASL and VAS modalities. The parameter ΔCBF (change in CBF between pre- and post-surgical states) performed reliably (ICC > 0.4), provided that a single baseline condition (or the mean of more than one baseline) was used for subtraction. Between-subjects, the pCASL measurements in the post-surgical pain state and ΔCBF were both characterised as reliable (ICC > 0.4). However, the subjective VAS pain ratings demonstrated a significant contribution of pain state variability, which suggests diminished utility for interindividual comparisons. These analyses indicate that the pCASL imaging technique has considerable potential for the comparison of within- and between-subjects differences associated with pain-induced state changes and baseline differences in regional CBF. They also suggest that differences in baseline perfusion and functional lateralisation characteristics may play an important role in the overall reliability of the estimated changes in CBF. Repeated measures designs have the important advantage that they provide good reliability for comparing condition effects because all sources of variability between subjects are excluded from the experimental error. The ability to elicit reliable neural correlates of on-going pain using quantitative perfusion imaging may help support the conclusions derived from subjective self-report.

3D GRASE PROPELLER: Improved Image Acquisition Technique for Arterial Spin Labeling Perfusion Imaging

PubMed Central

Tan, Huan; Hoge, W. Scott; Hamilton, Craig A.; Günther, Matthias; Kraft, Robert A.

2014-01-01

Arterial spin labeling (ASL) is a non-invasive technique that can quantitatively measure cerebral blood flow (CBF). While traditionally ASL employs 2D EPI or spiral acquisition trajectories, single-shot 3D GRASE is gaining popularity in ASL due to inherent SNR advantage and spatial coverage. However, a major limitation of 3D GRASE is through-plane blurring caused by T2 decay. A novel technique combining 3D GRASE and a PROPELLER trajectory (3DGP) is presented to minimize through-plane blurring without sacrificing perfusion sensitivity or increasing total scan time. Full brain perfusion images were acquired at a 3×3×5mm3 nominal voxel size with Q2TIPS-FAIR as the ASL preparation sequence. Data from 5 healthy subjects was acquired on a GE 1.5T scanner in less than 4 minutes per subject. While showing good agreement in CBF quantification with 3D GRASE, 3DGP demonstrated reduced through-plane blurring, improved anatomical details, high repeatability and robustness against motion, making it suitable for routine clinical use. PMID:21254211

Cerebral white matter blood flow and energy metabolism in multiple sclerosis.

PubMed

Steen, Christel; D'haeseleer, Miguel; Hoogduin, Johannes M; Fierens, Yves; Cambron, Melissa; Mostert, Jop P; Heersema, Dorothea J; Koch, Marcus W; De Keyser, Jacques

2013-09-01

Cerebral blood flow (CBF) is reduced in normal-appearing white matter (NAWM) of subjects with multiple sclerosis (MS), but the underlying mechanism is unknown. The objective of this article is to assess the relationship between reduced NAWM CBF and both axonal mitochondrial metabolism and astrocytic phosphocreatine (PCr) metabolism. Ten healthy controls and 25 MS subjects were studied with 3 Tesla magnetic resonance imaging. CBF was measured using pseudo-continuous arterial spin labeling. N-acetylaspartate/creatine (NAA/Cr) ratios (axonal mitochondrial metabolism) were obtained using (1)H-MR spectroscopy and PCr/β-ATP ratios using (31)P-MR spectroscopy. In centrum semiovale NAWM, we assessed correlations between CBF and both NAA/Cr and PCr/β-ATP ratios. Subjects with MS had a widespread reduction in CBF of NAWM (centrum semiovale, periventricular, frontal and occipital), and gray matter (frontoparietal cortex and thalamus). Compared to controls, NAA/Cr in NAWM of the centrum semiovale of MS subjects was decreased, whereas PCr/β-ATP was increased. We found no correlations between CBF and PCr/β-ATP. CBF and NAA/Cr correlated in controls (p = 0.02), but not in MS subjects (p = 0.68). Our results suggest that in MS patients there is no relationship between reduced CBF in NAWM and impaired axonal mitochondrial metabolism or astrocytic PCr metabolism.

Fully refocused multi-shot spatiotemporally encoded MRI: robust imaging in the presence of metallic implants.

PubMed

Ben-Eliezer, Noam; Solomon, Eddy; Harel, Elad; Nevo, Nava; Frydman, Lucio

2012-12-01

An approach has been recently introduced for acquiring arbitrary 2D NMR spectra or images in a single scan, based on the use of frequency-swept RF pulses for the sequential excitation and acquisition of the spins response. This spatiotemporal-encoding (SPEN) approach enables a unique, voxel-by-voxel refocusing of all frequency shifts in the sample, for all instants throughout the data acquisition. The present study investigates the use of this full-refocusing aspect of SPEN-based imaging in the multi-shot MRI of objects, subject to sizable field inhomogeneities that complicate conventional imaging approaches. 2D MRI experiments were performed at 7 T on phantoms and on mice in vivo, focusing on imaging in proximity to metallic objects. Fully refocused SPEN-based spin echo imaging sequences were implemented, using both Cartesian and back-projection trajectories, and compared with k-space encoded spin echo imaging schemes collected on identical samples under equal bandwidths and acquisition timing conditions. In all cases assayed, the fully refocused spatiotemporally encoded experiments evidenced a ca. 50 % reduction in signal dephasing in the proximity of the metal, as compared to analogous results stemming from the k-space encoded spin echo counterparts. The results in this study suggest that SPEN-based acquisition schemes carry the potential to overcome strong field inhomogeneities, of the kind that currently preclude high-field, high-resolution tissue characterizations in the neighborhood of metallic implants.

Single-shot turbo spin echo acquisition for in vivo cardiac diffusion MRI.

PubMed

Edalati, Masoud; Lee, Gregory R; Hui Wang; Taylor, Michael D; Li, Yu Y

2016-08-01

Diffusion MRI offers the ability to noninvasively characterize the microstructure of myocardium tissue and detect disease related pathology in cardiovascular examination. This study investigates the feasibility of in vivo cardiac diffusion MRI under free-breathing condition. A high-speed imaging technique, correlation imaging, is used to enable single-shot turbo spin echo for free-breathing cardiac data acquisition. The obtained in vivo cardiac diffusion-weighted images illustrate robust image quality and minor geometry distortions. The resultant diffusion scalar maps show reliable quantitative values consistent with those previously published in the literature. It is demonstrated that this technique has the potential for in vivo free-breathing cardiac diffusion MRI.

Parallel MR imaging: a user's guide.

PubMed

Glockner, James F; Hu, Houchun H; Stanley, David W; Angelos, Lisa; King, Kevin

2005-01-01

Parallel imaging is a recently developed family of techniques that take advantage of the spatial information inherent in phased-array radiofrequency coils to reduce acquisition times in magnetic resonance imaging. In parallel imaging, the number of sampled k-space lines is reduced, often by a factor of two or greater, thereby significantly shortening the acquisition time. Parallel imaging techniques have only recently become commercially available, and the wide range of clinical applications is just beginning to be explored. The potential clinical applications primarily involve reduction in acquisition time, improved spatial resolution, or a combination of the two. Improvements in image quality can be achieved by reducing the echo train lengths of fast spin-echo and single-shot fast spin-echo sequences. Parallel imaging is particularly attractive for cardiac and vascular applications and will likely prove valuable as 3-T body and cardiovascular imaging becomes part of standard clinical practice. Limitations of parallel imaging include reduced signal-to-noise ratio and reconstruction artifacts. It is important to consider these limitations when deciding when to use these techniques. (c) RSNA, 2005.

Discriminative Power of Arterial Spin Labeling Magnetic Resonance Imaging and 18F-Fluorodeoxyglucose Positron Emission Tomography Changes for Amyloid-β-Positive Subjects in the Alzheimer's Disease Continuum.

PubMed

Tosun, Duygu; Schuff, Norbert; Jagust, William; Weiner, Michael W

2016-01-01

Recent studies have demonstrated that arterial spin labeling magnetic resonance imaging (ASL-MRI) and fluorodeoxyglucose positron emission tomography (FDG-PET) identify similar regional abnormalities and have comparable diagnostic accuracy in Alzheimer's disease (AD). The agreement between these modalities in the AD continuum, which is an important concept for early detection and disease monitoring, is yet unclear. We aimed to assess the ability of the cerebral blood flow (CBF) measures from ASL-MRI and cerebral metabolic rate for glucose (CMRgl) measures from FDG-PET to distinguish amyloid-β-positive (Aβ+) subjects in the AD continuum from healthy controls. The study included asymptomatic, cognitively normal (CN) controls and patients with early mild cognitive impairment (MCI), late MCI, and AD, all with significant levels of cortical Aβ based on their florbetapir PET scans to restrict the study to patients truly in the AD continuum. The discrimination power of each modality was based on the whole-brain patterns of CBF and CMRgl changes identified by partial least squares logistic regression, a multivariate analysis technique. While CBF changes in the posterior inferior aspects of the brain and a pattern of CMRgl changes in the superior aspects of the brain including frontal and parietal regions best discriminated the Aβ+ subjects in the early disease stages from the Aβ- CN subjects, there was a greater agreement in the whole-brain patterns of CBF and CMRgl changes that best discriminated the Aβ+ subjects from the Aβ- CN subjects in the later disease stages. Despite the differences in the whole-brain patterns of CBF and CMRgl changes, the discriminative powers of both modalities were similar with statistically nonsignificant performance differences in sensitivity and specificity. The results comparing measurements of CBF to CMRgl add to previous reports that MRI-measured CBF has a similar diagnostic ability to detect AD as has FDG-PET. Our findings that CBF and CMRgl changes occur in different brain regions in Aβ+ subjects across the AD continuum compared with Aβ- CN subjects may be the result of methodological differences. Alternatively, these findings may signal alterations in neurovascular coupling which alter relationships between brain perfusion and glucose metabolism in the AD continuum. © 2015 S. Karger AG, Basel.

Optimization image of magnetic resonance imaging (MRI) T2 fast spin echo (FSE) with variation echo train length (ETL) on the rupture tendon achilles case

NASA Astrophysics Data System (ADS)

Muzamil, Akhmad; Haries Firmansyah, Achmad

2017-05-01

The research was done the optimization image of Magnetic Resonance Imaging (MRI) T2 Fast Spin Echo (FSE) with variation Echo Train Length (ETL) on the Rupture Tendon Achilles case. This study aims to find the variations Echo Train Length (ETL) from the results of ankle’s MRI image and find out how the value of Echo Train Length (ETL) works on the MRI ankle to produce optimal image. In this research, the used ETL variations were 12 and 20 with the interval 2 on weighting T2 FSE sagittal. The study obtained the influence of Echo Train Length (ETL) on the quality of ankle MRI image sagittal using T2 FSE weighting and analyzed in 25 images of five patients. The data analysis has done quantitatively with the Region of Interest (ROI) directly on computer MRI image planes which conducted statistical tests Signal to Noise Ratio (SNR) and Contras to Noise Ratio (CNR). The Signal to Noise Ratio (SNR) was the highest finding on fat tissue, while the Contras to Noise Ratio (CNR) on the Tendon-Fat tissue with ETL 12 found in two patients. The statistics test showed the significant SNR value of the 0.007 (p<0.05) of Tendon tissue, 0.364 (p>0.05) of the Fat, 0.912 (p>0.05) of the Fibula, and 0.436 (p>0.05) of the Heel Bone. For the contrast to noise ratio (CNR) of the Tendon-FAT tissue was about 0.041 (p>0.05). The results of the study showed that ETL variation with T2 FSE sagittal weighting had difference at Tendon tissue and Tendon-Fat tissue for MRI imaging quality. SNR and CNR were an important aspect on imaging optimization process to give the diagnose information.

MRI image plane nonuniformity in evaluation of ferrous sulphate dosimeter gel (FeGel) by means of T1-relaxation time.

PubMed

Magnusson, P; Bäck, S A; Olsson, L E

1999-11-01

MR image nonuniformity can vary significantly with the spin-echo pulse sequence repetition time. When MR images with different nonuniformity shapes are used in a T1-calculation the resulting T1-image becomes nonuniform. As shown in this work the uniformity TR-dependence of the spin-echo pulse sequence is a critical property for T1 measurements in general and for ferrous sulfate dosimeter gel (FeGel) applications in particular. The purpose was to study the characteristics of the MR image plane nonuniformity in FeGel evaluation. This included studies of the possibility of decreasing nonuniformities by selecting uniformity optimized repetition times, studies of the transmitted and received RF-fields and studies of the effectiveness of the correction methods background subtraction and quotient correction. A pronounced MR image nonuniformity variation with repetition and T1 relaxation time was observed, and was found to originate from nonuniform RF-transmission in combination with the inherent differences in T1 relaxation for different repetition times. The T1 calculation itself, the uniformity optimized repetition times, nor none of the correction methods studied could sufficiently correct the nonuniformities observed in the T1 images. The nonuniformities were found to vary considerably less with inversion time for the inversion-recovery pulse sequence, than with repetition time for the spin-echo pulse sequence, resulting in considerably lower T1 image nonuniformity levels.

Environmental heat stress enhances mental fatigue during sustained attention task performing: evidence from an ASL perfusion study.

PubMed

Qian, Shaowen; Li, Min; Li, Guoying; Liu, Kai; Li, Bo; Jiang, Qingjun; Li, Li; Yang, Zhen; Sun, Gang

2015-03-01

This study was to investigate the potential enhancing effect of heat stress on mental fatigue progression during sustained attention task using arterial spin labeling (ASL) imaging. Twenty participants underwent two thermal exposures in an environmental chamber: normothermic (NT) condition (25°C, 1h) and hyperthermic (HT) condition (50°C, 1h). After thermal exposure, they performed a twenty-minute psychomotor vigilance test (PVT) in the scanner. Behavioral analysis revealed progressively increasing subjective fatigue ratings and reaction time as PVT progressed. Moreover, heat stress caused worse performance. Perfusion imaging analyses showed significant resting-state cerebral blood flow (CBF) alterations after heat exposure. Specifically, increased CBF mainly gathered in thalamic-brainstem area while decreased CBF predominantly located in fronto-parietal areas, anterior cingulate cortex, posterior cingulate cortex, and medial frontal cortex. More importantly, diverse CBF distributions and trend of changes between both conditions were observed as the fatigue level progressed during subsequent PVT task. Specifically, higher CBF and enhanced rising trend were presented in superior parietal lobe, precuneus, posterior cingulate cortex and anterior cingulate cortex, while lower CBF or inhibited rising trend was found in dorsolateral frontal cortex, medial frontal cortex, inferior parietal lobe and thalamic-brainstem areas. Furthermore, the decrease of post-heat resting-state CBF in fronto-parietal cortex was correlated with subsequent slower reaction time, suggesting prior disturbed resting-state CBF might be indicator of performance potential and fatigue level in following task. These findings may provide proof for such a view: heat stress has a potential fatigue-enhancing effect when individual is performing highly cognition-demanding attention task. Copyright © 2014 Elsevier B.V. All rights reserved.

Cerebral Perfusion Changes in Post-Concussion Syndrome: A Prospective Controlled Cohort Study

PubMed Central

Marcil, Lorenzo D.; Dewey, Deborah; Carlson, Helen L.; MacMaster, Frank P.; Brooks, Brian L.; Lebel, R. Marc

2017-01-01

Abstract The biology of post-concussive symptoms is unclear. Symptoms are often increased during activities, and have been linked to decreased cerebrovascular reactivity and perfusion. The aim of this study was to examine cerebral blood flow (CBF) in children with different clinical recovery patterns following mild traumatic brain injury (mTBI). This was a prospective controlled cohort study of children with mTBI (ages 8 to 18 years) who were symptomatic with post-concussive symptoms at one month post-injury (symptomatic, n = 27) and children who had recovered quickly (asymptomatic, n = 24). Pseudo continuous arterial spin labeling magnetic resonance imaging (MRI) was used to quantify CBF. The mTBI groups were imaged at 40 days post-injury. Global and regional CBF were compared with healthy controls of similar age and sex but without a history of mTBI (n = 21). Seventy-two participants (mean age: 14.1 years) underwent neuroimaging. Significant differences in CBF were found: global CBF was higher in the symptomatic group and lower in the asymptomatic group compared with controls, (F(2,69) 9.734; p < 0.001). Post-injury symptom score could be predicted by pre-injury symptoms and CBF in presence of mTBI (adjusted R2 = 0.424; p < 0.001). Altered patterns of cerebral perfusion are seen following mTBI and are associated with the recovery trajectory. Symptomatic children have higher CBF. Children who “recovered” quickly, have decreased CBF suggesting that clinical recovery precedes the cerebral recovery. Further longitudinal studies are required to determine if these perfusion patterns continue to change over time. PMID:27554429

WE-DE-206-04: MRI Pulse Sequences - Spin Echo, Gradient Echo, EPI, Non-Cartesia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pooley, R.

Magnetic resonance imaging (MRI) has become an essential part of clinical imaging due to its ability to render high soft tissue contrast. Instead of ionizing radiation, MRI use strong magnetic field, radio frequency waves and field gradients to create diagnostic useful images. It can be used to image the anatomy and also functional and physiological activities within the human body. Knowledge of the basic physical principles underlying MRI acquisition is vitally important to successful image production and proper image interpretation. This lecture will give an overview of the spin physics, imaging principle of MRI, the hardware of the MRI scanner,more » and various pulse sequences and their applications. It aims to provide a conceptual foundation to understand the image formation process of a clinical MRI scanner. Learning Objectives: Understand the origin of the MR signal and contrast from the spin physics level. Understand the main hardware components of a MRI scanner and their purposes Understand steps for MR image formation including spatial encoding and image reconstruction Understand the main kinds of MR pulse sequences and their characteristics.« less

Measuring restriction sizes using diffusion weighted magnetic resonance imaging: a review.

PubMed

Martin, Melanie

2013-01-01

This article reviews a new concept in magnetic resonance as applied to cellular and biological systems. Diffusion weighted magnetic resonance imaging can be used to infer information about restriction sizes of samples being measured. The measurements rely on the apparent diffusion coefficient changing with diffusion times as measurements move from restricted to free diffusion regimes. Pulsed gradient spin echo (PGSE) measurements are limited in the ability to shorten diffusion times and thus are limited in restriction sizes which can be probed. Oscillating gradient spin echo (OGSE) measurements could provide shorter diffusion times so smaller restriction sizes could be probed.

gr-MRI: A software package for magnetic resonance imaging using software defined radios

NASA Astrophysics Data System (ADS)

Hasselwander, Christopher J.; Cao, Zhipeng; Grissom, William A.

2016-09-01

The goal of this work is to develop software that enables the rapid implementation of custom MRI spectrometers using commercially-available software defined radios (SDRs). The developed gr-MRI software package comprises a set of Python scripts, flowgraphs, and signal generation and recording blocks for GNU Radio, an open-source SDR software package that is widely used in communications research. gr-MRI implements basic event sequencing functionality, and tools for system calibrations, multi-radio synchronization, and MR signal processing and image reconstruction. It includes four pulse sequences: a single-pulse sequence to record free induction signals, a gradient-recalled echo imaging sequence, a spin echo imaging sequence, and an inversion recovery spin echo imaging sequence. The sequences were used to perform phantom imaging scans with a 0.5 Tesla tabletop MRI scanner and two commercially-available SDRs. One SDR was used for RF excitation and reception, and the other for gradient pulse generation. The total SDR hardware cost was approximately 2000. The frequency of radio desynchronization events and the frequency with which the software recovered from those events was also measured, and the SDR's ability to generate frequency-swept RF waveforms was validated and compared to the scanner's commercial spectrometer. The spin echo images geometrically matched those acquired using the commercial spectrometer, with no unexpected distortions. Desynchronization events were more likely to occur at the very beginning of an imaging scan, but were nearly eliminated if the user invoked the sequence for a short period before beginning data recording. The SDR produced a 500 kHz bandwidth frequency-swept pulse with high fidelity, while the commercial spectrometer produced a waveform with large frequency spike errors. In conclusion, the developed gr-MRI software can be used to develop high-fidelity, low-cost custom MRI spectrometers using commercially-available SDRs.

In vivo Proton Electron Double Resonance Imaging of Mice with Fast Spin Echo Pulse Sequence

PubMed Central

Sun, Ziqi; Li, Haihong; Petryakov, Sergey; Samouilov, Alex; Zweier, Jay L.

2011-01-01

Purpose To develop and evaluate a 2D fast spin echo (FSE) pulse sequence for enhancing temporal resolution and reducing tissue heating for in vivo proton electron double resonance imaging (PEDRI) of mice. Materials and Methods A four-compartment phantom containing 2 mM TEMPONE was imaged at 20.1 mT using 2D FSE-PEDRI and regular gradient echo (GRE)-PEDRI pulse sequences. Control mice were infused with TEMPONE over ∼1 min followed by time-course imaging using the 2D FSE-PEDRI sequence at intervals of 10 – 30 s between image acquisitions. The average signal intensity from the time-course images was analyzed using a first-order kinetics model. Results Phantom experiments demonstrated that EPR power deposition can be greatly reduced using the FSE-PEDRI pulse sequence compared to the conventional gradient echo pulse sequence. High temporal resolution was achieved at ∼4 s per image acquisition using the FSE-PEDRI sequence with a good image SNR in the range of 233-266 in the phantom study. The TEMPONE half-life measured in vivo was ∼72 s. Conclusion Thus, the FSE-PEDRI pulse sequence enables fast in vivo functional imaging of free radical probes in small animals greatly reducing EPR irradiation time with decreased power deposition and provides increased temporal resolution. PMID:22147559

New Imaging Strategies Using a Motion-Resistant Liver Sequence in Uncooperative Patients

PubMed Central

Kim, Bong Soo; Lee, Kyung Ryeol; Goh, Myeng Ju

2014-01-01

MR imaging has unique benefits for evaluating the liver because of its high-resolution capability and ability to permit detailed assessment of anatomic lesions. In uncooperative patients, motion artifacts can impair the image quality and lead to the loss of diagnostic information. In this setting, the recent advances in motion-resistant liver MR techniques, including faster imaging protocols (e.g., dual-echo magnetization-prepared rapid-acquisition gradient echo (MP-RAGE), view-sharing technique), the data under-sampling (e.g., gradient recalled echo (GRE) with controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA), single-shot echo-train spin-echo (SS-ETSE)), and motion-artifact minimization method (e.g., radial GRE with/without k-space-weighted image contrast (KWIC)), can provide consistent, artifact-free images with adequate image quality and can lead to promising diagnostic performance. Understanding of the different motion-resistant options allows radiologists to adopt the most appropriate technique for their clinical practice and thereby significantly improve patient care. PMID:25243115

Quantifying cerebellum grey matter and white matter perfusion using pulsed arterial spin labeling.

PubMed

Li, Xiufeng; Sarkar, Subhendra N; Purdy, David E; Briggs, Richard W

2014-01-01

To facilitate quantification of cerebellum cerebral blood flow (CBF), studies were performed to systematically optimize arterial spin labeling (ASL) parameters for measuring cerebellum perfusion, segment cerebellum to obtain separate CBF values for grey matter (GM) and white matter (WM), and compare FAIR ASST to PICORE. Cerebellum GM and WM CBF were measured with optimized ASL parameters using FAIR ASST and PICORE in five subjects. Influence of volume averaging in voxels on cerebellar grey and white matter boundaries was minimized by high-probability threshold masks. Cerebellar CBF values determined by FAIR ASST were 43.8 ± 5.1 mL/100 g/min for GM and 27.6 ± 4.5 mL/100 g/min for WM. Quantitative perfusion studies indicated that CBF in cerebellum GM is 1.6 times greater than that in cerebellum WM. Compared to PICORE, FAIR ASST produced similar CBF estimations but less subtraction error and lower temporal, spatial, and intersubject variability. These are important advantages for detecting group and/or condition differences in CBF values.

Hippocampal Dysfunction in Gulf War Veterans: Investigation with ASL Perfusion MR Imaging and Physostigmine Challenge

PubMed Central

Li, Xiufeng; Spence, Jeffrey S.; Buhner, David M.; Hart, John; Cullum, C. Munro; Biggs, Melanie M.; Hester, Andrea L.; Odegard, Timothy N.; Carmack, Patrick S.; Haley, Robert W.

2011-01-01

Purpose: To determine, with arterial spin labeling (ASL) perfusion magnetic resonance (MR) imaging and physostigmine challenge, if abnormal hippocampal blood flow in ill Gulf War veterans persists 11 years after initial testing with single photon emission computed tomography and nearly 20 years after the 1991 Gulf War. Materials and Methods: The local institutional review board approved this HIPAA-compliant study. Veterans were screened for contraindications and gave written informed consent before the study. In a semiblinded retrospective protocol, veterans in three Gulf War illness groups—syndrome 1 (impaired cognition), syndrome 2 (confusion-ataxia), and syndrome 3 (central neuropathic pain)—and a control group received intravenous infusions of saline in an initial session and physostigmine in a second session, 48 hours later. Each infusion was followed by measurement of hippocampal regional cerebral blood flow (rCBF) with pulsed ASL. A mixed-effects linear model adjusted for age was used to test for differences in rCBF after the cholinergic challenge across the four groups. Results: Physostigmine significantly decreased hippocampal rCBF in control subjects (P < .0005) and veterans with syndrome 1 (P < .05) but significantly increased hippocampal rCBF in veterans with syndrome 2 (P < .005) and veterans with syndrome 3 (P < .002). The abnormal increase in rCBF was found to have progressed to the left hippocampus of the veterans with syndrome 2 and to both hippocampi of the veterans with syndrome 3. Conclusion: Chronic hippocampal perfusion dysfunction persists or worsens in veterans with certain Gulf War syndromes. ASL MR imaging examination of hippocampal rCBF in a cholinergic challenge experiment may be useful as a diagnostic test for this condition. © RSNA, 2011 Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101715/-/DC1 PMID:21914840

Effects of global signal regression and subtraction methods on resting-state functional connectivity using arterial spin labeling data.

PubMed

Silva, João Paulo Santos; Mônaco, Luciana da Mata; Paschoal, André Monteiro; Oliveira, Ícaro Agenor Ferreira de; Leoni, Renata Ferranti

2018-05-16

Arterial spin labeling (ASL) is an established magnetic resonance imaging (MRI) technique that is finding broader applications in functional studies of the healthy and diseased brain. To promote improvement in cerebral blood flow (CBF) signal specificity, many algorithms and imaging procedures, such as subtraction methods, were proposed to eliminate or, at least, minimize noise sources. Therefore, this study addressed the main considerations of how CBF functional connectivity (FC) is changed, regarding resting brain network (RBN) identification and correlations between regions of interest (ROI), by different subtraction methods and removal of residual motion artifacts and global signal fluctuations (RMAGSF). Twenty young healthy participants (13 M/7F, mean age = 25 ± 3 years) underwent an MRI protocol with a pseudo-continuous ASL (pCASL) sequence. Perfusion-based images were obtained using simple, sinc and running subtraction. RMAGSF removal was applied to all CBF time series. Independent Component Analysis (ICA) was used for RBN identification, while Pearson' correlation was performed for ROI-based FC analysis. Temporal signal-to-noise ratio (tSNR) was higher in CBF maps obtained by sinc subtraction, although RMAGSF removal had a significant effect on maps obtained with simple and running subtractions. Neither the subtraction method nor the RMAGSF removal directly affected the identification of RBNs. However, the number of correlated and anti-correlated voxels varied for different subtraction and filtering methods. In an ROI-to-ROI level, changes were prominent in FC values and their statistical significance. Our study showed that both RMAGSF filtering and subtraction method might influence resting-state FC results, especially in an ROI level, consequently affecting FC analysis and its interpretation. Taking our results and the whole discussion together, we understand that for an exploratory assessment of the brain, one could avoid removing RMAGSF to not bias FC measures, but could use sinc subtraction to minimize low-frequency contamination. However, CBF signal specificity and frequency range for filtering purposes still need to be assessed in future studies. Copyright © 2018 Elsevier Inc. All rights reserved.

SU-D-18C-05: Variable Bolus Arterial Spin Labeling MRI for Accurate Cerebral Blood Flow and Arterial Transit Time Mapping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnston, M; Jung, Y

2014-06-01

Purpose: Arterial spin labeling (ASL) is an MRI perfusion imaging method from which quantitative cerebral blood flow (CBF) maps can be calculated. Acquisition with variable post-labeling delays (PLD) and variable TRs allows for arterial transit time (ATT) mapping and leads to more accurate CBF quantification with a scan time saving of 48%. In addition, T1 and M0 maps can be obtained without a separate scan. In order to accurately estimate ATT and T1 of brain tissue from the ASL data, variable labeling durations were invented, entitled variable-bolus ASL. Methods: All images were collected on a healthy subject with a 3Tmore » Siemens Skyra scanner. Variable-bolus Psuedo-continuous ASL (PCASL) images were collected with 7 TI times ranging 100-4300ms in increments of 700ms with TR ranging 1000-5200ms. All boluses were 1600ms when the TI allowed, otherwise the bolus duration was 100ms shorter than the TI. All TI times were interleaved to reduce sensitivity to motion. Voxel-wise T1 and M0 maps were estimated using a linear least squares fitting routine from the average singal from each TI time. Then pairwise subtraction of each label/control pair and averaging for each TI time was performed. CBF and ATT maps were created using the standard model by Buxton et al. with a nonlinear fitting routine using the T1 tissue map. Results: CBF maps insensitive to ATT were produced along with ATT maps. Both maps show patterns and averages consistent with literature. The T1 map also shows typical T1 contrast. Conclusion: It has been demonstrated that variablebolus ASL produces CBF maps free from the errors due to ATT and tissue T1 variations and provides M0, T1, and ATT maps which have potential utility. This is accomplished with a single scan in a feasible scan time (under 6 minutes) with low sensivity to motion.« less

Repeated measurements of cerebral blood flow in the left superior temporal gyrus reveal tonic hyperactivity in patients with auditory verbal hallucinations: a possible trait marker

PubMed Central

Homan, Philipp; Kindler, Jochen; Hauf, Martinus; Walther, Sebastian; Hubl, Daniela; Dierks, Thomas

2013-01-01

Background: The left superior temporal gyrus (STG) has been suggested to play a key role in auditory verbal hallucinations (AVH) in patients with schizophrenia. Methods: Eleven medicated subjects with schizophrenia and medication-resistant AVH and 19 healthy controls underwent perfusion magnetic resonance (MR) imaging with arterial spin labeling (ASL). Three additional repeated measurements were conducted in the patients. Patients underwent a treatment with transcranial magnetic stimulation (TMS) between the first 2 measurements. The main outcome measure was the pooled cerebral blood flow (CBF), which consisted of the regional CBF measurement in the left STG and the global CBF measurement in the whole brain. Results: Regional CBF in the left STG in patients was significantly higher compared to controls (p < 0.0001) and to the global CBF in patients (p < 0.004) at baseline. Regional CBF in the left STG remained significantly increased compared to the global CBF in patients across time (p < 0.0007), and it remained increased in patients after TMS compared to the baseline CBF in controls (p < 0.0001). After TMS, PANSS (p = 0.003) and PSYRATS (p = 0.01) scores decreased significantly in patients. Conclusions: This study demonstrated tonically increased regional CBF in the left STG in patients with schizophrenia and auditory hallucinations despite a decrease in symptoms after TMS. These findings were consistent with what has previously been termed a trait marker of AVH in schizophrenia. PMID:23805093

The effects of altered intrathoracic pressure on resting cerebral blood flow and its response to visual stimulation

PubMed Central

Hayen, Anja; Herigstad, Mari; Kelly, Michael; Okell, Thomas W.; Murphy, Kevin; Wise, Richard G.; Pattinson, Kyle T.S.

2013-01-01

Investigating how intrathoracic pressure changes affect cerebral blood flow (CBF) is important for a clear interpretation of neuroimaging data in patients with abnormal respiratory physiology, intensive care patients receiving mechanical ventilation and in research paradigms that manipulate intrathoracic pressure. Here, we investigated the effect of experimentally increased and decreased intrathoracic pressures upon CBF and the stimulus-evoked CBF response to visual stimulation. Twenty healthy volunteers received intermittent inspiratory and expiratory loads (plus or minus 9 cmH2O for 270 s) and viewed an intermittent 2 Hz flashing checkerboard, while maintaining stable end-tidal CO2. CBF was recorded with transcranial Doppler sonography (TCD) and whole-brain pseudo-continuous arterial spin labeling magnetic resonance imaging (PCASL MRI). Application of inspiratory loading (negative intrathoracic pressure) showed an increase in TCD-measured CBF of 4% and a PCASL-measured increase in grey matter CBF of 5%, but did not alter mean arterial pressure (MAP). Expiratory loading (positive intrathoracic pressure) did not alter CBF, while MAP increased by 3%. Neither loading condition altered the perfusion response to visual stimulation in the primary visual cortex. In both loading conditions localized CBF increases were observed in the somatosensory and motor cortices, and in the cerebellum. Altered intrathoracic pressures, whether induced experimentally, therapeutically or through a disease process, have possible significant effects on CBF and should be considered as a potential systematic confound in the interpretation of perfusion-based neuroimaging data. PMID:23108273

Rapid myelin water imaging in human cervical spinal cord.

PubMed

Ljungberg, Emil; Vavasour, Irene; Tam, Roger; Yoo, Youngjin; Rauscher, Alexander; Li, David K B; Traboulsee, Anthony; MacKay, Alex; Kolind, Shannon

2017-10-01

Myelin water imaging (MWI) using multi-echo T 2 relaxation is a quantitative MRI technique that can be used as an in vivo biomarker for myelin in the central nervous system. MWI using a multi-echo spin echo sequence currently takes more than 20 min to acquire eight axial slices (5 mm thickness) in the cervical spinal cord, making spinal cord MWI impractical for implementation in clinical studies. In this study, an accelerated gradient and spin echo sequence (GRASE), previously validated for brain MWI, was adapted for spinal cord MWI. Ten healthy volunteers were scanned with the GRASE sequence (acquisition time 8.5 min) and compared with the multi-echo spin echo sequence (acquisition time 23.5 min). Using region of interest analysis, myelin estimates obtained from the two sequences were found to be in good agreement (mean difference = -0.0092, 95% confidence interval =  - 0.0092 ± 0.061; regression slope = 1.01, ρ = 0.9). MWI using GRASE was shown to be highly reproducible with an average coefficient of variation of 6.1%. The results from this study show that MWI can be performed in the cervical spinal cord in less than 10 min, allowing for practical implementation in multimodal clinical studies. Magn Reson Med 78:1482-1487, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Cerebral blood flow laterality derived from arterial spin labeling as a biomarker for assessing the disease severity of parkinson's disease.

PubMed

Yamashita, Koji; Hiwatashi, Akio; Togao, Osamu; Kikuchi, Kazufumi; Yamaguchi, Hiroo; Suzuki, Yuriko; Kamei, Ryotaro; Yamasaki, Ryo; Kira, Jun-Ichi; Honda, Hiroshi

2017-06-01

To evaluate cerebral blood flow (CBF) laterality derived from arterial spin labeling (ASL) in early-stage Parkinson's disease (PD) patients compared with those with advanced stages. Thirty-eight patients with PD (21 patients in early stages, 17 patients in advanced stages) were retrospectively studied. The CBF maps derived from 3T ASL data were co-registered to the corresponding 3DT1WI using SPM 12 software. Caudate nucleus (CN), putamen (PT), globus pallidus (GP), and thalamus (TH) were manually traced on the representative axial slices of 3DT1WI. CBF of the CN, PT, GP, and TH was measured using corresponding pixels on the co-registered CBF maps. A laterality index (LI) was calculated as the ratio of the contralateral CBF to primary affected side CBF. Each LI was compared between early and advanced stages of PD using the Mann-Whitney U-test. The LIs were also compared between each stage of PD. In the CN, the LIs were significantly higher in early stages (mean LI ± SD, 95% confidence interval = 1.06 ± 0.14, 1.00-1.13) than in advanced stages (0.94 ± 0.14, 0.87-1.01; P < 0.05). We also observed a tendency toward decreased LIs with disease severity (1.10 ± 0.14, 0.99-1.21 for Hoehn and Yahr stage I; 1.04 ± 0.14, 0.92-1.12 for stage II; 0.96 ± 0.11, 0.89-1.10 for stage III; 0.93 ± 0.17, 0.81-1.05 for stage IV). The evaluation of CBF laterality pattern in the CN using ASL may be useful for assessing the disease severity of PD patients. 3 J. MAGN. RESON. IMAGING 2017;45:1821-1826. © 2016 International Society for Magnetic Resonance in Medicine.

A fast screening protocol for carotid plaques imaging using 3D multi-contrast MRI without contrast agent.

PubMed

Zhang, Na; Zhang, Lei; Yang, Qi; Pei, Anqi; Tong, Xiaoxin; Chung, Yiu-Cho; Liu, Xin

2017-06-01

To implement a fast (~15min) MRI protocol for carotid plaque screening using 3D multi-contrast MRI sequences without contrast agent on a 3Tesla MRI scanner. 7 healthy volunteers and 25 patients with clinically confirmed transient ischemic attack or suspected cerebrovascular ischemia were included in this study. The proposed protocol, including 3D T1-weighted and T2-weighted SPACE (variable-flip-angle 3D turbo spin echo), and T1-weighted magnetization prepared rapid acquisition gradient echo (MPRAGE) was performed first and was followed by 2D T1-weighted and T2-weighted turbo spin echo, and post-contrast T1-weighted SPACE sequences. Image quality, number of plaques, and vessel wall thicknesses measured at the intersection of the plaques were evaluated and compared between sequences. Average examination time of the proposed protocol was 14.6min. The average image quality scores of 3D T1-weighted, T2-weighted SPACE, and T1-weighted magnetization prepared rapid acquisition gradient echo were 3.69, 3.75, and 3.48, respectively. There was no significant difference in detecting the number of plaques and vulnerable plaques using pre-contrast 3D images with or without post-contrast T1-weighted SPACE. The 3D SPACE and 2D turbo spin echo sequences had excellent agreement (R=0.96 for T1-weighted and 0.98 for T2-weighted, p<0.001) regarding vessel wall thickness measurements. The proposed protocol demonstrated the feasibility of attaining carotid plaque screening within a 15-minute scan, which provided sufficient anatomical coverage and critical diagnostic information. This protocol offers the potential for rapid and reliable screening for carotid plaques without contrast agent. Copyright © 2016. Published by Elsevier Inc.

T1 weighted fat/water separated PROPELLER acquired with dual bandwidths.

PubMed

Rydén, Henric; Berglund, Johan; Norbeck, Ola; Avventi, Enrico; Skare, Stefan

2018-04-24

To describe a fat/water separated dual receiver bandwidth (rBW) spin echo PROPELLER sequence that eliminates the dead time associated with single rBW sequences. A nonuniform noise whitening by regularization of the fat/water inverse problem is proposed, to enable dual rBW reconstructions. Bipolar, flyback, and dual spin echo sequences were developed. All sequences acquire two echoes with different rBW without dead time. Chemical shift displacement was corrected by performing the fat/water separation in k-space, prior to gridding. The proposed sequences were compared to fat saturation, and single rBW sequences, in terms of SNR and CNR efficiency, using clinically relevant acquisition parameters. The impact of motion was investigated. Chemical shift correction greatly improved the image quality, especially at high resolution acquired with low rBW, and also improved motion estimates. SNR efficiency of the dual spin echo sequence was up to 20% higher than the single rBW acquisition, while CNR efficiency was 50% higher for the bipolar acquisition. Noise whitening was deemed necessary for all dual rBW acquisitions, rendering high image quality with strong and homogenous fat suppression. Dual rBW sequences eliminate the dead time present in single rBW sequences, which improves SNR efficiency. In combination with the proposed regularization, this enables highly efficient T1-weighted PROPELLER images without chemical shift displacement. © 2018 International Society for Magnetic Resonance in Medicine.

Magnetic resonance imaging of pulmonary infection in immunocompromised children: comparison with multidetector computed tomography.

PubMed

Ozcan, H Nursun; Gormez, Ayşegul; Ozsurekci, Yasemin; Karakaya, Jale; Oguz, Berna; Unal, Sule; Cetin, Mualla; Ceyhan, Mehmet; Haliloglu, Mithat

2017-02-01

Computed tomography (CT) is commonly used to detect pulmonary infection in immunocompromised children. To compare MRI and multidetector CT findings of pulmonary abnormalities in immunocompromised children. Seventeen neutropaenic children (6 girls; ages 2-18 years) were included. Non-contrast-enhanced CT was performed with a 64-detector CT scanner. Axial and coronal non-enhanced thoracic MRI was performed using a 1.5-T scanner within 24 h of the CT examination (true fast imaging with steady-state free precession, fat-saturated T2-weighted turbo spin echo with motion correction, T2-weighted half-Fourier single-shot turbo spin echo [HASTE], fat-saturated T1-weighted spoiled gradient echo). Pulmonary abnormalities (nodules, consolidations, ground glass opacities, atelectasis, pleural effusion and lymph nodes) were evaluated and compared among MRI sequences and between MRI and CT. The relationship between MRI sequences and nodule sizes was examined by chi- square test. Of 256 CT lesions, 207 (81%, 95% confidence interval [CI] 76-85%) were detected at MRI. Of 202 CT-detected nodules, 157 (78%, 95% CI 71-83%) were seen at motion-corrected MRI. Of the 1-5-mm nodules, 69% were detected by motion-corrected T2-weighted MRI and 38% by HASTE MRI. Sensitivity of MRI (both axial fat-saturated T2-weighted turbo spin echo with variable phase encoding directions (BLADE) images and HASTE sequences) to detect pulmonary abnormalities is promising.

[Imaging characteristics of PROPELLER T2-weighted imaging].

PubMed

Goto, Masami; Aoki, Shigeki; Hayashi, Naoto; Mori, Harushi; Watanabe, Yasushi; Ino, Kenji; Satake, Yoshirou; Nishida, Katuji; Sato, Haruo; Iida, Kyouhito; Mima, Kazuo; Ohtomo, Kuni

2004-11-01

As the PROPELLER sequence is a combination of the radial scan and fast-spin-echo (FSE) sequence, it can be considered an FSE sequence with a motion correlation. However, there are some differences between PROPELLER and FSE owing to differences in k-space trajectory. We clarified the imaging characteristics of PROPELLER T2-weighted imaging (T2WI) for different parameters in comparison with usual FSE T2WI. When the same parameters were used, PROPELLER T2WI showed a higher signal-to-noise ratio (SNR) and lower spatial resolution than usual FSE. Effective echo time (TE) changed with different echo train lengths (ETL) or different bandwidths on PROPELLER, and imaging contrast changed accordingly to be more effective.

Double-spin-echo diffusion weighting with a modified eddy current adjustment.

PubMed

Finsterbusch, Jürgen

2010-04-01

Magnetic field inhomogeneities like eddy current-related gradient fields cause geometric distortions in echo-planar imaging (EPI). This in particular affects diffusion-weighted imaging where these distortions vary with the direction of the diffusion weighting and hamper the accurate determination of diffusion parameters. The double-spin-echo preparation often used aims to reduce the cumulative eddy current effect by adjusting the diffusion-weighting gradient pulse durations to the time constant of the dominant eddy current contribution. However, eddy currents with a variety of time constants may be present and cause residual distortions. Here, a modification is proposed where the two bipolar gradient pairs of the preparation are adjusted independently to different time constants. At the expense of a slightly prolonged echo time, residual geometric distortions and correspondingly increased values of the diffusion anisotropy can be reduced as is demonstrated in phantoms and the human brain. Thus, it may help to improve the reliability of diffusion-weighted EPI. Copyright 2010 Elsevier Inc. All rights reserved.

Measuring the labeling efficiency of pseudocontinuous arterial spin labeling.

PubMed

Chen, Zhensen; Zhang, Xingxing; Yuan, Chun; Zhao, Xihai; van Osch, Matthias J P

2017-05-01

Optimization and validation of a sequence for measuring the labeling efficiency of pseudocontinuous arterial spin labeling (pCASL) perfusion MRI. The proposed sequence consists of a labeling module and a single slice Look-Locker echo planar imaging readout. A model-based algorithm was used to calculate labeling efficiency from the signal acquired from the main brain-feeding arteries. Stability of the labeling efficiency measurement was evaluated with regard to the use of cardiac triggering, flow compensation and vein signal suppression. Accuracy of the measurement was assessed by comparing the measured labeling efficiency to mean brain pCASL signal intensity over a wide range of flip angles as applied in the pCASL labeling. Simulations show that the proposed algorithm can effectively calculate labeling efficiency when correcting for T1 relaxation of the blood spins. Use of cardiac triggering and vein signal suppression improved stability of the labeling efficiency measurement, while flow compensation resulted in little improvement. The measured labeling efficiency was found to be linearly (R = 0.973; P < 0.001) related to brain pCASL signal intensity over a wide range of pCASL flip angles. The optimized labeling efficiency sequence provides robust artery-specific labeling efficiency measurement within a short acquisition time (∼30 s), thereby enabling improved accuracy of pCASL CBF quantification. Magn Reson Med 77:1841-1852, 2017. © 2016 International Society for Magnetic Resonance in Medicine Magn Reson Med 77:1841-1852, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Dynamic association between perfusion and white matter integrity across time since injury in Veterans with history of TBI.

PubMed

Clark, Alexandra L; Bangen, Katherine J; Sorg, Scott F; Schiehser, Dawn M; Evangelista, Nicole D; McKenna, Benjamin; Liu, Thomas T; Delano-Wood, Lisa

2017-01-01

Cerebral blood flow (CBF) plays a critical role in the maintenance of neuronal integrity, and CBF alterations have been linked to deleterious white matter changes. Although both CBF and white matter microstructural alterations have been observed within the context of traumatic brain injury (TBI), the degree to which these pathological changes relate to one another and whether this association is altered by time since injury have not been examined. The current study therefore sought to clarify associations between resting CBF and white matter microstructure post-TBI. 37 veterans with history of mild or moderate TBI (mmTBI) underwent neuroimaging and completed health and psychiatric symptom questionnaires. Resting CBF was measured with multiphase pseudocontinuous arterial spin labeling (MPPCASL), and white matter microstructural integrity was measured with diffusion tensor imaging (DTI). The cingulate cortex and cingulum bundle were selected as a priori regions of interest for the ASL and DTI data, respectively, given the known vulnerability of these regions to TBI. Regression analyses controlling for age, sex, and posttraumatic stress disorder (PTSD) symptoms revealed a significant time since injury × resting CBF interaction for the left cingulum ( p  < 0.005). Decreased CBF was significantly associated with reduced cingulum fractional anisotropy (FA) in the chronic phase; however, no such association was observed for participants with less remote TBI. Our results showed that reduced CBF was associated with poorer white matter integrity in those who were further removed from their brain injury. Findings provide preliminary evidence of a possible dynamic association between CBF and white matter microstructure that warrants additional consideration within the context of the negative long-term clinical outcomes frequently observed in those with history of TBI. Additional cross-disciplinary studies integrating multiple imaging modalities (e.g., DTI, ASL) and refined neuropsychiatric assessment are needed to better understand the nature, temporal course, and dynamic association between brain changes and clinical outcomes post-injury.

Application of Medical Magnetic Resonance Imaging for Particle Concentration Measurement

NASA Astrophysics Data System (ADS)

Borup, Daniel; Elkins, Christopher; Eaton, John

2014-11-01

Particle transport and deposition in internal flows is important in a range of applications such as dust aggregation in turbine engines and aerosolized medicine deposition in human airways. Unlike optical techniques, Magnetic Resonance Imaging (MRI) is well suited for complex applications in which optical access is not possible. Here we present efforts to measure 3D particle concentration distribution using MRI. Glass particles dispersed in water flow reduce MRI signal from a spin-echo or gradient-echo scanning sequence by decreasing spin density and dephasing the spins present in the fluid. A preliminary experiment was conducted with a particle streak injected at the centerline of a turbulent round pipe flow with a U bend. Measurements confirmed that signal strength was related to particle concentration and showed the effects of gravitational settling and turbulent dispersion. Next, measurements of samples in a mixing chamber were taken. Particle volume fraction was varied and sensitivity to particle/fluid velocity was investigated. These results give a relationship between MRI signal, particle volume fraction, MRI sequence echo time, and spin relaxation parameters that can be used to measure local particle volume fraction in other turbulent flows of interest.

19F Magnetic resonance imaging of perfluorooctanoic acid encapsulated in liposome for biodistribution measurement.

PubMed

Kimura, Atsuomi; Narazaki, Michiko; Kanazawa, Yoko; Fujiwara, Hideaki

2004-07-01

The tissue distribution of perfluorooctanoic acid (PFOA), which is known to show unique biological responses, has been visualized in female mice by (19)F magnetic resonance imaging (MRI) incorporated with the recent advances in microimaging technique. The chemical shift selected fast spin-echo method was applied to acquire in vivo (19)F MR images of PFOA. The in vivo T(1) and T(2) relaxation times of PFOA were proven to be extremely short, which were 140 (+/- 20) ms and 6.3 (+/- 2.2) ms, respectively. To acquire the in vivo (19)F MR images of PFOA, it was necessary to optimize the parameters of signal selection and echo train length. The chemical shift selection was effectively performed by using the (19)F NMR signal of CF(3) group of PFOA without the signal overlapping because the chemical shift difference between the CF(3) and neighbor signals reaches to 14 kHz. The most optimal echo train length to obtain (19)F images efficiently was determined so that the maximum echo time (TE) value in the fast spin-echo sequence was comparable to the in vivo T(2) value. By optimizing these parameters, the in vivo (19)F MR image of PFOA was enabled to obtain efficiently in 12 minutes. As a result, the time course of the accumulation of PFOA into the mouse liver was clearly pursued in the (19)F MR images. Thus, it was concluded that the (19)F MRI becomes the effective method toward the future pharmacological and toxicological studies of perfluorocarboxilic acids.

Cardiovascular magnetic resonance physics for clinicians: part I.

PubMed

Ridgway, John P

2010-11-30

There are many excellent specialised texts and articles that describe the physical principles of cardiovascular magnetic resonance (CMR) techniques. There are also many texts written with the clinician in mind that provide an understandable, more general introduction to the basic physical principles of magnetic resonance (MR) techniques and applications. There are however very few texts or articles that attempt to provide a basic MR physics introduction that is tailored for clinicians using CMR in their daily practice. This is the first of two reviews that are intended to cover the essential aspects of CMR physics in a way that is understandable and relevant to this group. It begins by explaining the basic physical principles of MR, including a description of the main components of an MR imaging system and the three types of magnetic field that they generate. The origin and method of production of the MR signal in biological systems are explained, focusing in particular on the two tissue magnetisation relaxation properties (T1 and T2) that give rise to signal differences from tissues, showing how they can be exploited to generate image contrast for tissue characterisation. The method most commonly used to localise and encode MR signal echoes to form a cross sectional image is described, introducing the concept of k-space and showing how the MR signal data stored within it relates to properties within the reconstructed image. Before describing the CMR acquisition methods in detail, the basic spin echo and gradient pulse sequences are introduced, identifying the key parameters that influence image contrast, including appearances in the presence of flowing blood, resolution and image acquisition time. The main derivatives of these two pulse sequences used for cardiac imaging are then described in more detail. Two of the key requirements for CMR are the need for data acquisition first to be to be synchronised with the subject's ECG and to be fast enough for the subject to be able to hold their breath. Methods of ECG synchronisation using both triggering and retrospective gating approaches, and accelerated data acquisition using turbo or fast spin echo and gradient echo pulse sequences are therefore outlined in some detail. It is shown how double inversion black blood preparation combined with turbo or fast spin echo pulse sequences acquisition is used to achieve high quality anatomical imaging. For functional cardiac imaging using cine gradient echo pulse sequences two derivatives of the gradient echo pulse sequence; spoiled gradient echo and balanced steady state free precession (bSSFP) are compared. In each case key relevant imaging parameters and vendor-specific terms are defined and explained.

Cardiovascular magnetic resonance physics for clinicians: part I

PubMed Central

2010-01-01

There are many excellent specialised texts and articles that describe the physical principles of cardiovascular magnetic resonance (CMR) techniques. There are also many texts written with the clinician in mind that provide an understandable, more general introduction to the basic physical principles of magnetic resonance (MR) techniques and applications. There are however very few texts or articles that attempt to provide a basic MR physics introduction that is tailored for clinicians using CMR in their daily practice. This is the first of two reviews that are intended to cover the essential aspects of CMR physics in a way that is understandable and relevant to this group. It begins by explaining the basic physical principles of MR, including a description of the main components of an MR imaging system and the three types of magnetic field that they generate. The origin and method of production of the MR signal in biological systems are explained, focusing in particular on the two tissue magnetisation relaxation properties (T1 and T2) that give rise to signal differences from tissues, showing how they can be exploited to generate image contrast for tissue characterisation. The method most commonly used to localise and encode MR signal echoes to form a cross sectional image is described, introducing the concept of k-space and showing how the MR signal data stored within it relates to properties within the reconstructed image. Before describing the CMR acquisition methods in detail, the basic spin echo and gradient pulse sequences are introduced, identifying the key parameters that influence image contrast, including appearances in the presence of flowing blood, resolution and image acquisition time. The main derivatives of these two pulse sequences used for cardiac imaging are then described in more detail. Two of the key requirements for CMR are the need for data acquisition first to be to be synchronised with the subject's ECG and to be fast enough for the subject to be able to hold their breath. Methods of ECG synchronisation using both triggering and retrospective gating approaches, and accelerated data acquisition using turbo or fast spin echo and gradient echo pulse sequences are therefore outlined in some detail. It is shown how double inversion black blood preparation combined with turbo or fast spin echo pulse sequences acquisition is used to achieve high quality anatomical imaging. For functional cardiac imaging using cine gradient echo pulse sequences two derivatives of the gradient echo pulse sequence; spoiled gradient echo and balanced steady state free precession (bSSFP) are compared. In each case key relevant imaging parameters and vendor-specific terms are defined and explained. PMID:21118531

A quantitative experimental phantom study on MRI image uniformity.

PubMed

Felemban, Doaa; Verdonschot, Rinus G; Iwamoto, Yuri; Uchiyama, Yuka; Kakimoto, Naoya; Kreiborg, Sven; Murakami, Shumei

2018-05-23

Our goal was to assess MR image uniformity by investigating aspects influencing said uniformity via a method laid out by the National Electrical Manufacturers Association (NEMA). Six metallic materials embedded in a glass phantom were scanned (i.e. Au, Ag, Al, Au-Ag-Pd alloy, Ti and Co-Cr alloy) as well as a reference image. Sequences included spin echo (SE) and gradient echo (GRE) scanned in three planes (i.e. axial, coronal, and sagittal). Moreover, three surface coil types (i.e. head and neck, Brain, and temporomandibular joint coils) and two image correction methods (i.e. surface coil intensity correction or SCIC, phased array uniformity enhancement or PURE) were employed to evaluate their effectiveness on image uniformity. Image uniformity was assessed using the National Electrical Manufacturers Association peak-deviation non-uniformity method. Results showed that temporomandibular joint coils elicited the least uniform image and brain coils outperformed head and neck coils when metallic materials were present. Additionally, when metallic materials were present, spin echo outperformed gradient echo especially for Co-Cr (particularly in the axial plane). Furthermore, both SCIC and PURE improved image uniformity compared to uncorrected images, and SCIC slightly surpassed PURE when metallic metals were present. Lastly, Co-Cr elicited the least uniform image while other metallic materials generally showed similar patterns (i.e. no significant deviation from images without metallic metals). Overall, a quantitative understanding of the factors influencing MR image uniformity (e.g. coil type, imaging method, metal susceptibility, and post-hoc correction method) is advantageous to optimize image quality, assists clinical interpretation, and may result in improved medical and dental care.

Quantifying Cerebellum Grey Matter and White Matter Perfusion Using Pulsed Arterial Spin Labeling

PubMed Central

Li, Xiufeng; Sarkar, Subhendra N.; Purdy, David E.; Briggs, Richard W.

2014-01-01

To facilitate quantification of cerebellum cerebral blood flow (CBF), studies were performed to systematically optimize arterial spin labeling (ASL) parameters for measuring cerebellum perfusion, segment cerebellum to obtain separate CBF values for grey matter (GM) and white matter (WM), and compare FAIR ASST to PICORE. Cerebellum GM and WM CBF were measured with optimized ASL parameters using FAIR ASST and PICORE in five subjects. Influence of volume averaging in voxels on cerebellar grey and white matter boundaries was minimized by high-probability threshold masks. Cerebellar CBF values determined by FAIR ASST were 43.8 ± 5.1 mL/100 g/min for GM and 27.6 ± 4.5 mL/100 g/min for WM. Quantitative perfusion studies indicated that CBF in cerebellum GM is 1.6 times greater than that in cerebellum WM. Compared to PICORE, FAIR ASST produced similar CBF estimations but less subtraction error and lower temporal, spatial, and intersubject variability. These are important advantages for detecting group and/or condition differences in CBF values. PMID:24949416

Application of phase consistency to improve time efficiency and image quality in dual echo black-blood carotid angiography.

PubMed

Kholmovski, Eugene G; Parker, Dennis L

2005-07-01

There is a considerable similarity between proton density-weighted (PDw) and T2-weighted (T2w) images acquired by dual echo fast spin-echo (FSE) sequences. The similarity manifests itself not only in image space as correspondence between intensities of PDw and T2w images, but also in phase space as consistency between phases of PDw and T2w images. Methods for improving the imaging efficiency and image quality of dual echo FSE sequences based on this feature have been developed. The total scan time of dual echo FSE acquisition may be reduced by as much as 25% by incorporating an estimate of the image phase from a fully sampled PDw image when reconstructing partially sampled T2w images. The quality of T2w images acquired using phased array coils may be significantly improved by using the developed noise reduction reconstruction scheme, which is based on the correspondence between the PDw and T2w image intensities and the consistency between the PDw and T2w image phases. Studies of phantom and human subject MRI data were performed to evaluate the effectiveness of the techniques.

[Contrastive analysis of artifacts produced by metal dental crowns in 3.0 T magnetic resonance imaging with six sequences].

PubMed

Lan, Gao; Yunmin, Lian; Pu, Wang; Haili, Huai

2016-06-01

This study aimed to observe and evaluate six 3.0 T sequences of metallic artifacts produced by metal dental crowns. Dental crowns fabricated with four different materials (Co-Gr, Ni-Gr, Ti alloy and pure Ti) were evaluated. A mature crossbreed dog was used as the experimental animal, and crowns were fabricated for its upper right second premolar. Each crown was examined through head MRI (3.0 T) with six sequences, namely, T₁ weighted-imaging of spin echo (T₁W/SE), T₂ weighted-imaging of inversion recovery (T₂W/IR), T₂ star gradient echo (T₂*/GRE), T2 weighted-imaging of fast spin echo (T₂W/FSE), T₁ weighted-imaging of fluid attenuate inversion recovery (T₂W/FLAIR), and T₂ weighted-imaging of propeller (T₂W/PROP). The largest area and layers of artifacts were assessed and compared. The artifact in the T₂*/GRE sequence was significantly wider than those in the other sequences (P < 0.01), whose artifact extent was not significantly different (P > 0.05). T₂*/GRE exhibit the strongest influence on the artifact, whereas the five other sequences contribute equally to artifact generation.

3D Ultrashort TE MRI for Evaluation of Cartilaginous Endplate of Cervical Disk In Vivo: Feasibility and Correlation With Disk Degeneration in T2-Weighted Spin-Echo Sequence.

PubMed

Kim, Yeo Ju; Cha, Jang Gyu; Shin, Yoon Sang; Chaudhari, Akshay S; Suh, Young Ju; Hwan Yoon, Seung; Gold, Garry E

2018-05-01

The purpose of this study was to evaluate the feasibility of 3D ultrashort TE (UTE) MRI in depicting the cartilaginous endplate (CEP) and its abnormalities and to investigate the association between CEP abnormalities and disk degeneration on T2-weighted spin-echo (SE) MR images in cervical disks in vivo. Eight healthy volunteers and 70 patients were examined using 3-T MRI with the 3D UTE cones trajectory technique (TR/TE, 16.1/0.032, 6.6). In the volunteer study, quantitative and qualitative assessments of CEP depiction were conducted for the 3D UTE and T2-weighted SE imaging. In the patient study, CEP abnormalities were analyzed. Intersequence agreement between the images obtained with the first-echo 3D UTE sequence and the images created by subtracting the second-echo from the first-echo 3D UTE sequence (subtracted 3D UTE) and the intraobserver and interobserver agreements for 3D UTE overall were also tested. The CEP abnormalities on the 3D UTE images correlated with the Miyazaki grading of the T2-weighted SE images. In the volunteer study, the CEP was well visualized on 3D UTE images but not on T2-weighted SE images (p < 0.001). In the patient study, for evaluation of CEP abnormalities, intersequence agreements were substantial to almost perfect, intraobserver agreements were substantial to almost perfect, and interobserver agreements were moderate to substantial (p < 0.001). All of the CEP abnormalities correlated with the Miyazaki grade with statistical significance (p < 0.001). Three-dimensional UTE MRI feasibly depicts the CEP and CEP abnormalities, which may be associated with the severity of disk degeneration on T2-weighted SE MRI.

7T MRI-Histologic Correlation Study of Low Specific Absorption Rate T2-Weighted GRASE Sequences in the Detection of White Matter Involvement in Multiple Sclerosis.

PubMed

Bagnato, Francesca; Hametner, Simon; Pennell, David; Dortch, Richard; Dula, Adrienne N; Pawate, Siddharama; Smith, Seth A; Lassmann, Hans; Gore, John C; Welch, Edward B

2015-01-01

The high value of the specific absorption rate (SAR) of radio-frequency (RF) energy arising from the series of RF refocusing pulses in T2-weighted (T2-w) turbo spin echo (TSE) MRI hampers its clinical application at 7.0 Tesla (7T). T2-w gradient and spin echo (GRASE) uses the speed from gradient refocusing in combination with the chemical-shift/static magnetic field (B0) inhomogeneity insensitivity from spin-echo refocusing to acquire T2-w images with a limited number of refocusing RF pulses, thus reducing SAR. To investigate whether low SAR T2-w GRASE could replace T2-w TSE in detecting white matter (WM) disease in MS patients imaged at 7T. The .7 mm3 isotropic T2-w TSE and T2-w GRASE images with variable echo times (TEs) and echo planar imaging (EPI) factors were obtained on a 7T scanner from postmortem samples of MS brains. These samples were derived from brains of 3 female MS patients. WM lesions (WM-Ls) and normal-appearing WM (NAWM) signal intensity, WM-Ls/NAWM contrast-to-noise ratio (CNR) and MRI/myelin staining sections comparisons were obtained. GRASE sequences with EPI factor/TE = 3/50 and 3/75 ms were comparable to the SE technique for measures of CNR in WM-Ls and NAWM and for detection of WM-Ls. In all sequences, however, identification of areas with remyelination, Wallerian degeneration, and gray matter demyelination, as depicted by myelin staining, was not possible. T2-w GRASE images may replace T2-w TSE for clinical use. However, even at 7T, both sequences fail in detecting and characterizing MS disease beyond visible WM-Ls. Copyright © 2015 by the American Society of Neuroimaging.

Resting state cerebral blood flow with arterial spin labeling MRI in developing human brains.

PubMed

Liu, Feng; Duan, Yunsuo; Peterson, Bradley S; Asllani, Iris; Zelaya, Fernando; Lythgoe, David; Kangarlu, Alayar

2018-07-01

The development of brain circuits is coupled with changes in neurovascular coupling, which refers to the close relationship between neural activity and cerebral blood flow (CBF). Studying the characteristics of CBF during resting state in developing brain can be a complementary way to understand the functional connectivity of the developing brain. Arterial spin labeling (ASL), as a noninvasive MR technique, is particularly attractive for studying cerebral perfusion in children and even newborns. We have collected pulsed ASL data in resting state for 47 healthy subjects from young children to adolescence (aged from 6 to 20 years old). In addition to studying the developmental change of static CBF maps during resting state, we also analyzed the CBF time series to reveal the dynamic characteristics of CBF in differing age groups. We used the seed-based correlation analysis to examine the temporal relationship of CBF time series between the selected ROIs and other brain regions. We have shown the developmental patterns in both static CBF maps and dynamic characteristics of CBF. While higher CBF of default mode network (DMN) in all age groups supports that DMN is the prominent active network during the resting state, the CBF connectivity patterns of some typical resting state networks show distinct patterns of metabolic activity during the resting state in the developing brains. Copyright © 2018 European Paediatric Neurology Society. All rights reserved.

Evaluation of Magnetic Resonance Imaging-Compatible Needles and Interactive Sequences for Musculoskeletal Interventions Using an Open High-Field Magnetic Resonance Imaging Scanner

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wonneberger, Uta, E-mail: uta.wonneberger@charite.d; Schnackenburg, Bernhard, E-mail: bernhard.schnackenburg@philips.co; Streitparth, Florian, E-mail: florian.streitparth@charite.de

2010-04-15

In this article, we study in vitro evaluation of needle artefacts and image quality for musculoskeletal laser-interventions in an open high-field magnetic resonance imaging (MRI) scanner at 1.0T with vertical field orientation. Five commercially available MRI-compatible puncture needles were assessed based on artefact characteristics in a CuSO4 phantom (0.1%) and in human cadaveric lumbar spines. First, six different interventional sequences were evaluated with varying needle orientation to the main magnetic field B0 (0{sup o} to 90{sup o}) in a sequence test. Artefact width, needle-tip error, and contrast-to-noise ratio (CNR) were calculated. Second, a gradient-echo sequence used for thermometric monitoring wasmore » assessed and in varying echo times, artefact width, tip error, and signal-to-noise ratio (SNR) were measured. Artefact width and needle-tip error correlated with needle material, instrument orientation to B0, and sequence type. Fast spin-echo sequences produced the smallest needle artefacts for all needles, except for the carbon fibre needle (width <3.5 mm, tip error <2 mm) at 45{sup o} to B0. Overall, the proton density-weighted spin-echo sequences had the best CNR (CNR{sub Muscle/Needle} >16.8). Concerning the thermometric gradient echo sequence, artefacts remained <5 mm, and the SNR reached its maximum at an echo time of 15 ms. If needle materials and sequences are accordingly combined, guidance and monitoring of musculoskeletal laser interventions may be feasible in a vertical magnetic field at 1.0T.« less

Investigating the physiology of brain activation with MRI

NASA Astrophysics Data System (ADS)

Buxton, Richard B.; Uludag, Kamil; Dubowitz, David J.

2004-04-01

Functional magnetic resonance imaging (fMRI) has become a powerful tool for investigating the working human brain based on the blood oxygenation level dependent (BOLD) effect on the MR signal. However, despite the widespread use of fMRI techniques for mapping brain activation, the basic physiological mechanisms underlying the observed signal changes are still poorly understood. Arterial spin labeling (ASL) techniques, which measure cerebral blood flow (CBF) and the BOLD effect simultaneously, provide a useful tool for investigating these physiological questions. In this paper, recent results of studies manipulating the baseline CBF both pharmacologically and physiologically will be discussed. These data are consistent with a feed-forward mechanism of neurovascular coupling, and suggest that the CBF change itself may be a more robust reflection of neural activity changes than the BOLD effect. Consistent with these data, a new thermodynamic hypothesis is proposed for the physiological function of CBF regulation: maintenance of the [O2]/[CO2] concentration ratio at the mitochondria in order to preserve the free energy available from oxidative metabolism. A kinetic model based on this hypothesis provides a reasonable quantitative description of the CBF changes associated with neural activity and altered blood gases (CO2 and O2).

Comparison of 250 MHz electron spin echo and continuous wave oxygen EPR imaging methods for in vivo applications

PubMed Central

Epel, Boris; Sundramoorthy, Subramanian V.; Barth, Eugene D.; Mailer, Colin; Halpern, Howard J.

2011-01-01

Purpose: The authors compare two electron paramagnetic resonance imaging modalities at 250 MHz to determine advantages and disadvantages of those modalities for in vivo oxygen imaging. Methods: Electron spin echo (ESE) and continuous wave (CW) methodologies were used to obtain three-dimensional images of a narrow linewidth, water soluble, nontoxic oxygen-sensitive trityl molecule OX063 in vitro and in vivo. The authors also examined sequential images obtained from the same animal injected intravenously with trityl spin probe to determine temporal stability of methodologies. Results: A study of phantoms with different oxygen concentrations revealed a threefold advantage of the ESE methodology in terms of reduced imaging time and more precise oxygen resolution for samples with less than 70 torr oxygen partial pressure. Above∼100 torr, CW performed better. The images produced by both methodologies showed pO2 distributions with similar mean values. However, ESE images demonstrated superior performance in low pO2 regions while missing voxels in high pO2 regions. Conclusions: ESE and CW have different areas of applicability. ESE is superior for hypoxia studies in tumors. PMID:21626937

Arterial spin labeled perfusion imaging using three-dimensional turbo spin echo with a distributed spiral-in/out trajectory.

PubMed

Li, Zhiqiang; Schär, Michael; Wang, Dinghui; Zwart, Nicholas R; Madhuranthakam, Ananth J; Karis, John P; Pipe, James G

2016-01-01

The three-dimensional (3D) spiral turbo spin echo (TSE) sequence is one of the preferred readout methods for arterial spin labeled (ASL) perfusion imaging. Conventional spiral TSE collects the data using a spiral-out readout on a stack of spirals trajectory. However, it may result in suboptimal image quality and is not flexible in protocol design. The goal of this study is to provide a more robust readout technique without such limitation. The proposed technique incorporates a spiral-in/out readout into 3D TSE, and collects the data on a distributed spirals trajectory. The data set is split into the spiral-in and -out subsets that are reconstructed separately and combined after image deblurring. The volunteer results acquired with the proposed technique show no geometric distortion or signal pileup, as is present with GRASE, and no signal loss, as is seen with conventional spiral TSE. Examples also demonstrate the flexibility in changing the imaging parameters to satisfy various criteria. The 3D TSE with a distributed spiral-in/out trajectory provides a robust readout technique and allows for easy protocol design, thus is a promising alternative to GRASE or conventional spiral TSE for ASL perfusion imaging. © 2015 Wiley Periodicals, Inc.

Simultaneous multislice refocusing via time optimal control.

PubMed

Rund, Armin; Aigner, Christoph Stefan; Kunisch, Karl; Stollberger, Rudolf

2018-02-09

Joint design of minimum duration RF pulses and slice-selective gradient shapes for MRI via time optimal control with strict physical constraints, and its application to simultaneous multislice imaging. The minimization of the pulse duration is cast as a time optimal control problem with inequality constraints describing the refocusing quality and physical constraints. It is solved with a bilevel method, where the pulse length is minimized in the upper level, and the constraints are satisfied in the lower level. To address the inherent nonconvexity of the optimization problem, the upper level is enhanced with new heuristics for finding a near global optimizer based on a second optimization problem. A large set of optimized examples shows an average temporal reduction of 87.1% for double diffusion and 74% for turbo spin echo pulses compared to power independent number of slices pulses. The optimized results are validated on a 3T scanner with phantom measurements. The presented design method computes minimum duration RF pulse and slice-selective gradient shapes subject to physical constraints. The shorter pulse duration can be used to decrease the effective echo time in existing echo-planar imaging or echo spacing in turbo spin echo sequences. © 2018 International Society for Magnetic Resonance in Medicine.

Developmental trajectories of cerebrovascular reactivity in healthy children and young adults assessed with magnetic resonance imaging.

PubMed

Leung, Jackie; Kosinski, Przemyslaw D; Croal, Paula L; Kassner, Andrea

2016-05-15

Cerebrovascular reactivity (CVR) reflects the vasodilatory reserve of cerebral resistance vessels. Normal development in children is associated with significant changes in blood pressure, cerebral blood flow (CBF) and cerebral oxygen metabolism. Therefore, it stands to reason that CVR will also undergo changes during this period. The study acquired magnetic resonance imaging measures of CVR and CBF in healthy children and young adults to trace their changes with age. We found that CVR changes in two phases, increasing with age until the mid-teens, followed by a decrease. Baseline CBF declined steadily with age. We conclude that CVR varies with age during childhood, which prompts future CVR studies involving children to take into account the effect of development. Cerebrovascular reactivity (CVR) reflects the vasculature's ability to accommodate changes in blood flow demand thereby serving as a critical imaging tool for mapping vascular reserve. Normal development is associated with extensive physiological changes in blood pressure, cerebral blood flow and cerebral metabolic rate of oxygen, all of which can affect CVR. Moreover, the evolution of these physiological parameters is most prominent during childhood. Therefore, the aim of this study was to use non-invasive magnetic resonance imaging (MRI) to characterize the developmental trajectories of CVR in healthy children and young adults, and relate them to changes in cerebral blood flow (CBF). Thirty-four healthy subjects (17 males, 17 females; age 9-30 years) underwent CVR assessment using blood oxygen level-dependent MRI in combination with a computer controlled CO2 stimulus. In addition, baseline CBF was measured with a pulsed arterial spin labelling sequence. CVR exhibited a gradual increase with age in both grey and white matter up to 14.7 years. After this break point, a negative correlation with age was detected. Baseline CBF maintained a consistent negative linear correlation across the entire age range. The significant age-dependent changes in CVR and CBF demonstrate the evolution of cerebral haemodynamics in children and should be taken into consideration. The shift in developmental trajectory of CVR from increasing to decreasing suggests that physiological factors beyond baseline CBF also influence CVR. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

Image domain propeller fast spin echo.

PubMed

Skare, Stefan; Holdsworth, Samantha J; Lilja, Anders; Bammer, Roland

2013-04-01

A new pulse sequence for high-resolution T2-weighted (T2-w) imaging is proposed - image domain propeller fast spin echo (iProp-FSE). Similar to the T2-w PROPELLER sequence, iProp-FSE acquires data in a segmented fashion, as blades that are acquired in multiple TRs. However, the iProp-FSE blades are formed in the image domain instead of in the k-space domain. Each iProp-FSE blade resembles a single-shot fast spin echo (SSFSE) sequence with a very narrow phase-encoding field of view (FOV), after which N rotated blade replicas yield the final full circular FOV. Our method of combining the image domain blade data to a full FOV image is detailed, and optimal choices of phase-encoding FOVs and receiver bandwidths were evaluated on phantom and volunteers. The results suggest that a phase FOV of 15-20%, a receiver bandwidth of ±32-63 kHz and a subsequent readout time of about 300 ms provide a good tradeoff between signal-to-noise ratio (SNR) efficiency and T2 blurring. Comparisons between iProp-FSE, Cartesian FSE and PROPELLER were made on single-slice axial brain data, showing similar T2-w tissue contrast and SNR with great anatomical conspicuity at similar scan times - without colored noise or streaks from motion. A new slice interleaving order is also proposed to improve the multislice capabilities of iProp-FSE. Copyright © 2013 Elsevier Inc. All rights reserved.

MRI Artifacts of a Metallic Stent Derived From a Human Aorta Specimen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soto, M. E.; Flores, P.; Marrufo, O.

Magnetic resonance imaging has proved to be a useful technique to get images of the whole body. However, the presence of ferromagnetic material can cause susceptibility artifacts, which result from microscopic gradients that occur near the boundaries between areas displaying different magnetic susceptibility. These gradients cause dephasing of spins and frequency shifts in the surrounding tissues. Intravoxel dephasing and spatial mis-registration can degrade image quality. An aorta with a metallic stent was preserved in formaldehyde at 10% inside acrylic cylinders and used to obtain MR images. We tested pulsed spin echo and gradient echo sequences to improve image quality. Allmore » experiments were performed on a 7T/21 cm Varian system (Varian, Inc, Palo Alto, CA) equipped with Direct Drive technology and a 16-rung birdcage coil transceiver. The presence of metallic stents produces a lack of signal that might give falsely reassuring appearances within the vessel lumen.« less

Altered cerebral perfusion in executive, affective, and motor networks during adolescent depression.

PubMed

Ho, Tiffany C; Wu, Jing; Shin, David D; Liu, Thomas T; Tapert, Susan F; Yang, Guang; Connolly, Colm G; Frank, Guido K W; Max, Jeffrey E; Wolkowitz, Owen; Eisendrath, Stuart; Hoeft, Fumiko; Banerjee, Dipavo; Hood, Korey; Hendren, Robert L; Paulus, Martin P; Simmons, Alan N; Yang, Tony T

2013-10-01

Although substantial literature has reported regional cerebral blood flow (rCBF) abnormalities in adults with depression, these studies commonly necessitated the injection of radioisotopes into subjects. The recent development of arterial spin labeling (ASL), however, allows noninvasive measurements of rCBF. Currently, no published ASL studies have examined cerebral perfusion in adolescents with depression. Thus, the aim of the present study was to examine baseline cerebral perfusion in adolescent depression using a newly developed ASL technique: pseudocontinuous arterial spin labeling (PCASL). A total of 25 medication-naive adolescents (13-17 years of age) diagnosed with major depressive disorder (MDD) and 26 well-matched control subjects underwent functional magnetic resonance imaging. Baseline rCBF was measured via a novel PCASL method that optimizes tagging efficiency. Voxel-based whole brain analyses revealed significant frontal, limbic, paralimbic, and cingulate hypoperfusion in the group with depression (p < .05, corrected). Hyperperfusion was also observed within the subcallosal cingulate, putamen, and fusiform gyrus (p < .05, corrected). Similarly, region-of-interest analyses revealed amygdalar and insular hypoperfusion in the group with depression, as well as hyperperfusion in the putamen and superior insula (p < .05, corrected). Adolescents with depression and healthy adolescents appear to differ on rCBF in executive, affective, and motor networks. Dysfunction in these regions may contribute to the cognitive, emotional, and psychomotor symptoms commonly present in adolescent depression. These findings point to possible biomarkers for adolescent depression that could inform early interventions and treatments, and establishes a methodology for using PCASL to noninvasively measure rCBF in clinical and healthy adolescent populations. Copyright © 2013 American Academy of Child and Adolescent Psychiatry. Published by Elsevier Inc. All rights reserved.

Impaired cerebral blood flow networks in temporal lobe epilepsy with hippocampal sclerosis: A graph theoretical approach.

PubMed

Sone, Daichi; Matsuda, Hiroshi; Ota, Miho; Maikusa, Norihide; Kimura, Yukio; Sumida, Kaoru; Yokoyama, Kota; Imabayashi, Etsuko; Watanabe, Masako; Watanabe, Yutaka; Okazaki, Mitsutoshi; Sato, Noriko

2016-09-01

Graph theory is an emerging method to investigate brain networks. Altered cerebral blood flow (CBF) has frequently been reported in temporal lobe epilepsy (TLE), but graph theoretical findings of CBF are poorly understood. Here, we explored graph theoretical networks of CBF in TLE using arterial spin labeling imaging. We recruited patients with TLE and unilateral hippocampal sclerosis (HS) (19 patients with left TLE, and 21 with right TLE) and 20 gender- and age-matched healthy control subjects. We obtained all participants' CBF maps using pseudo-continuous arterial spin labeling and analyzed them using the Graph Analysis Toolbox (GAT) software program. As a result, compared to the controls, the patients with left TLE showed a significantly low clustering coefficient (p=0.024), local efficiency (p=0.001), global efficiency (p=0.010), and high transitivity (p=0.015), whereas the patients with right TLE showed significantly high assortativity (p=0.046) and transitivity (p=0.011). The group with right TLE also had high characteristic path length values (p=0.085), low global efficiency (p=0.078), and low resilience to targeted attack (p=0.101) at a trend level. Lower normalized clustering coefficient (p=0.081) in the left TLE and higher normalized characteristic path length (p=0.089) in the right TLE were found also at a trend level. Both the patients with left and right TLE showed significantly decreased clustering in similar areas, i.e., the cingulate gyri, precuneus, and occipital lobe. Our findings revealed differing left-right network metrics in which an inefficient CBF network in left TLE and vulnerability to irritation in right TLE are suggested. The left-right common finding of regional decreased clustering might reflect impaired default-mode networks in TLE. Copyright © 2016 Elsevier Inc. All rights reserved.

Arterial spin labeling fMRI measurements of decreased blood flow in primary visual cortex correlates with decreased visual function in human glaucoma.

PubMed

Duncan, Robert O; Sample, Pamela A; Bowd, Christopher; Weinreb, Robert N; Zangwill, Linda M

2012-05-01

Altered metabolic activity has been identified as a potential contributing factor to the neurodegeneration associated with primary open angle glaucoma (POAG). Consequently, we sought to determine whether there is a relationship between the loss of visual function in human glaucoma and resting blood perfusion within primary visual cortex (V1). Arterial spin labeling (ASL) functional magnetic resonance imaging (fMRI) was conducted in 10 participants with POAG. Resting cerebral blood flow (CBF) was measured from dorsal and ventral V1. Behavioral measurements of visual function were obtained using standard automated perimetry (SAP), short-wavelength automated perimetry (SWAP), and frequency-doubling technology perimetry (FDT). Measurements of CBF were compared to differences in visual function for the superior and inferior hemifield. Differences in CBF between ventral and dorsal V1 were correlated with differences in visual function for the superior versus inferior visual field. A statistical bootstrapping analysis indicated that the observed correlations between fMRI responses and measurements of visual function for SAP (r=0.49), SWAP (r=0.63), and FDT (r=0.43) were statistically significant (all p<0.05). Resting blood perfusion in human V1 is correlated with the loss of visual function in POAG. Altered CBF may be a contributing factor to glaucomatous optic neuropathy, or it may be an indication of post-retinal glaucomatous neurodegeneration caused by damage to the retinal ganglion cells. Copyright © 2012 Elsevier Ltd. All rights reserved.

Gadolinium-DTPA enhanced magnetic resonance imaging of bone cysts in patients with rheumatoid arthritis.

PubMed Central

Gubler, F M; Algra, P R; Maas, M; Dijkstra, P F; Falke, T H

1993-01-01

OBJECTIVES--To examine the contents of intraosseous cysts in patients with rheumatoid arthritis (RA) through the signal intensity characteristics on gadolinium-DTPA (Gd-DTPA) enhanced magnetic resonance imaging. METHODS--The hand or foot joints of nine patients with the cystic form of RA (where the initial radiological abnormality consisted of intraosseous cysts without erosions) were imaged before and after intravenous administration of Gd-DTPA. A 0.6 unit, T1 weighted spin echo and T2* weighted gradient echo were used to obtain images in at least two perpendicular planes. RESULTS--Most cysts showed a low signal intensity on the non-enhanced T1 weighted (spin echo) images and a high signal intensity on the T2* weighted (gradient echo) images, consistent with a fluid content. No cyst showed an enhancement of signal intensity on the T1 weighted images after intravenous administration of Gd-DTPA, whereas synovium hyperplasia at the site of bony erosions did show an increased signal intensity after Gd-DTPA. Magnetic resonance imaging detected more cysts (as small as 2 mm) than plain films, and the cysts were located truly intraosseously. In six patients no other joint abnormalities were identified by magnetic resonance imaging; the three other patients also showed, after Gd-DTPA administration, an enhanced synovium at the site of bony erosions. CONCLUSIONS--It is suggested that intraosseous bone cysts in patients with RA do not contain hyperaemic synovial proliferation. The bone cysts in patients with the cystic form of RA may be the only joint abnormality. Images PMID:8257207

gr-MRI: A software package for magnetic resonance imaging using software defined radios.

PubMed

Hasselwander, Christopher J; Cao, Zhipeng; Grissom, William A

2016-09-01

The goal of this work is to develop software that enables the rapid implementation of custom MRI spectrometers using commercially-available software defined radios (SDRs). The developed gr-MRI software package comprises a set of Python scripts, flowgraphs, and signal generation and recording blocks for GNU Radio, an open-source SDR software package that is widely used in communications research. gr-MRI implements basic event sequencing functionality, and tools for system calibrations, multi-radio synchronization, and MR signal processing and image reconstruction. It includes four pulse sequences: a single-pulse sequence to record free induction signals, a gradient-recalled echo imaging sequence, a spin echo imaging sequence, and an inversion recovery spin echo imaging sequence. The sequences were used to perform phantom imaging scans with a 0.5Tesla tabletop MRI scanner and two commercially-available SDRs. One SDR was used for RF excitation and reception, and the other for gradient pulse generation. The total SDR hardware cost was approximately $2000. The frequency of radio desynchronization events and the frequency with which the software recovered from those events was also measured, and the SDR's ability to generate frequency-swept RF waveforms was validated and compared to the scanner's commercial spectrometer. The spin echo images geometrically matched those acquired using the commercial spectrometer, with no unexpected distortions. Desynchronization events were more likely to occur at the very beginning of an imaging scan, but were nearly eliminated if the user invoked the sequence for a short period before beginning data recording. The SDR produced a 500kHz bandwidth frequency-swept pulse with high fidelity, while the commercial spectrometer produced a waveform with large frequency spike errors. In conclusion, the developed gr-MRI software can be used to develop high-fidelity, low-cost custom MRI spectrometers using commercially-available SDRs. Copyright © 2016. Published by Elsevier Inc.

Longitudinal analysis of MR spin-spin relaxation times (T2) in medial femorotibial cartilage of adolescent vs mature athletes: dependence of deep and superficial zone properties on sex and age.

PubMed

Wirth, W; Eckstein, F; Boeth, H; Diederichs, G; Hudelmaier, M; Duda, G N

2014-10-01

Cartilage spin-spin magnetic resonance imaging (MRI) relaxation time (T2) represents a promising imaging biomarker of "early" osteoarthritis (OA) known to be associated with cartilage composition (collagen integrity, orientation, and hydration). However, no longitudinal imaging studies have been conducted to examine cartilage maturation in healthy subjects thus far. Therefore, we explore T2 change in the deep and superficial cartilage layers at the end of adolescence. Twenty adolescent and 20 mature volleyball athletes were studied (each 10 men and 10 women). Multi-echo spin-echo (MESE) images were acquired at baseline and 2-year follow-up. After segmentation, cartilage T2 was calculated in the deep and superficial cartilage layers of the medial tibial (MT) and the central, weight-bearing part of the medial femoral condyle (cMF), using five echoes (TE 19.4-58.2 ms). 16 adolescent (6 men, 10 women, baseline age 15.8 ± 0.5 years) and 17 mature (nine men, eight women, age 46.5 ± 5.2 years) athletes had complete baseline and follow-up images of sufficient quality to compute T2. In adolescents, a longitudinal decrease in T2 was observed in the deep layers of MT (-2.0 ms; 95% confidence interval (CI): [-3.4, -0.6] ms; P < 0.01) and cMF (-1.3 ms; [-2.4, -0.3] ms; P < 0.05), without obvious differences between males and females. No significant change was observed in the superficial layers, or in the deep or superficial layers of the mature athletes. In this first pilot study on quantitative imaging of cartilage maturation in healthy, athletic subjects, we find evidence of cartilage compositional change in deep cartilage layers of the medial femorotibial compartment in adolescents, most likely related to organizational changes in the collagen matrix. Copyright © 2014 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Short-scan-time multi-slice diffusion MRI of the mouse cervical spinal cord using echo planar imaging.

PubMed

Callot, Virginie; Duhamel, Guillaume; Cozzone, Patrick J; Kober, Frank

2008-10-01

Mouse spinal cord (SC) diffusion-weighted imaging (DWI) provides important information on tissue morphology and structural changes that may occur during pathologies such as multiple sclerosis or SC injury. The acquisition scheme of the commonly used DWI techniques is based on conventional spin-echo encoding, which is time-consuming. The purpose of this work was to investigate whether the use of echo planar imaging (EPI) would provide good-quality diffusion MR images of mouse SC, as well as accurate measurements of diffusion-derived metrics, and thus enable diffusion tensor imaging (DTI) and highly resolved DWI within reasonable scan times. A four-shot diffusion-weighted spin-echo EPI (SE-EPI) sequence was evaluated at 11.75 T on a group of healthy mice (n = 10). SE-EPI-derived apparent diffusion coefficients of gray and white matter were compared with those obtained using a conventional spin-echo sequence (c-SE) to validate the accuracy of the method. To take advantage of the reduction in acquisition time offered by the EPI sequence, multi-slice DTI acquisitions were performed covering the cervical segments (six slices, six diffusion-encoding directions, three b values) within 30 min (vs 2 h for c-SE). From these measurements, fractional anisotropy and mean diffusivities were calculated, and fiber tracking along the C1 to C6 cervical segments was performed. In addition, high-resolution images (74 x 94 microm(2)) were acquired within 5 min per direction. Clear delineation of gray and white matter and identical apparent diffusion coefficient values were obtained, with a threefold reduction in acquisition time compared with c-SE. While overcoming the difficulties associated with high spatially and temporally resolved DTI measurements, the present SE-EPI approach permitted identification of reliable quantitative parameters with a reproducibility compatible with the detection of pathologies. The SE-EPI method may be particularly valuable when multiple sets of images from the SC are needed, in cases of rapidly evolving conditions, to decrease the duration of anesthesia or to improve MR exploration by including additional MR measurements. Copyright (c) 2008 John Wiley & Sons, Ltd.

Magnetic resonance imaging metallic artifact of commonly encountered surgical implants and foreign material.

PubMed

Sutherland-Smith, James; Tilley, Brenda

2012-01-01

Magnetic resonance imaging (MRI) artifacts secondary to metallic implants and foreign bodies are well described. Herein, we provide quantitative data from veterinary implants including total hip arthroplasty implants, cranial cruciate repair implants, surgical screws, a skin staple, ligation clips, an identification microchip, ameroid constrictor, and potential foreign bodies including air gun and BB projectiles and a sewing needle. The objects were scanned in a gelatin phantom with plastic grid using standardized T2-weighted turbo-spin echo (TSE), T1-weighted spin echo, and T2*-weighted gradient recalled echo (GRE) image acquisitions at 1.5 T. Maximum linear dimensions and areas of signal voiding and grid distortion were calculated using a DICOM workstation for each sequence and object. Artifact severity was similar between the T2-weighted TSE and T1-weighted images, while the T2*-weighted images were most susceptible to artifact. Metal type influenced artifact size with the largest artifacts arising from steel objects followed by surgical stainless steel, titanium, and lead. For animals with metallic surgical implants or foreign bodies, the quantification of the artifact size will help guide clinicians on the viability of MRI. © 2012 Veterinary Radiology & Ultrasound.

Measurement of brain perfusion in newborns: Pulsed arterial spin labeling (PASL) versus pseudo-continuous arterial spin labeling (pCASL)

PubMed Central

Boudes, Elodie; Gilbert, Guillaume; Leppert, Ilana Ruth; Tan, Xianming; Pike, G. Bruce; Saint-Martin, Christine; Wintermark, Pia

2014-01-01

Background Arterial spin labeling (ASL) perfusion-weighted imaging (PWI) by magnetic resonance imaging (MRI) has been shown to be useful for identifying asphyxiated newborns at risk of developing brain injury, whether or not therapeutic hypothermia was administered. However, this technique has been only rarely used in newborns until now, because of the challenges to obtain sufficient signal-to-noise ratio (SNR) and spatial resolution in newborns. Objective To compare two methods of ASL-PWI (i.e., single inversion-time pulsed arterial spin labeling [single TI PASL], and pseudo-continuous arterial spin labeling [pCASL]) to assess brain perfusion in asphyxiated newborns treated with therapeutic hypothermia and in healthy newborns. Design/methods We conducted a prospective cohort study of term asphyxiated newborns meeting the criteria for therapeutic hypothermia; four additional healthy term newborns were also included as controls. Each of the enrolled newborns was scanned at least once during the first month of life. Each MRI scan included conventional anatomical imaging, as well as PASL and pCASL PWI-MRI. Control and labeled images were registered separately to reduce the effect of motion artifacts. For each scan, the axial slice at the level of the basal ganglia was used for comparisons. Each scan was scored for its image quality. Quantification of whole-slice cerebral blood flow (CBF) was done afterwards using previously described formulas. Results A total number of 61 concomitant PASL and pCASL scans were obtained in nineteen asphyxiated newborns treated with therapeutic hypothermia and four healthy newborns. After discarding the scans with very poor image quality, 75% (46/61) remained for comparison between the two ASL methods. pCASL images presented a significantly superior image quality score compared to PASL images (p < 0.0001). Strong correlation was found between the CBF measured by PASL and pCASL (r = 0.61, p < 0.0001). Conclusion This study demonstrates that both ASL methods are feasible to assess brain perfusion in healthy and sick newborns. However, pCASL might be a better choice over PASL in newborns, as pCASL perfusion maps had a superior image quality that allowed a more detailed identification of the different brain structures. PMID:25379424

The detectability of brain metastases using contrast-enhanced spin-echo or gradient-echo images: a systematic review and meta-analysis.

PubMed

Suh, Chong Hyun; Jung, Seung Chai; Kim, Kyung Won; Pyo, Junhee

2016-09-01

This study aimed to compare the detectability of brain metastases using contrast-enhanced spin-echo (SE) and gradient-echo (GRE) T1-weighted images. The Ovid-MEDLINE and EMBASE databases were searched for studies on the detectability of brain metastases using contrast-enhanced SE or GRE images. The pooled proportions for the detectability of brain metastases were assessed using random-effects modeling. Heterogeneity among studies was determined using χ (2) statistics for the pooled estimates and the inconsistency index, I (2) . To overcome heterogeneity, subgroup analyses according to slice thickness and lesion size were performed. A total of eight eligible studies, which included a sample size of 252 patients and 1413 brain metastases, were included. The detectability of brain metastases using SE images (89.2 %) was higher than using GRE images (81.6 %; adjusted 84.0 %), but this difference was not statistically significant (p = 0.2385). In subgroup analysis of studies with 1-mm-thick slices and small metastases (<5 mm in diameter), 3-dimensional (3D) SE images demonstrated a higher detectability in comparison to 3D GRE images (93.7 % vs 73.1 % in 1-mm-thick slices; 89.5 % vs 59.4 % for small metastases) (p < 0.0001). Although both SE or GRE images are acceptable for detecting brain metastases, contrast-enhanced 3D SE images using 1-mm-thick slices are preferred for detecting brain metastases, especially small lesions (<5 mm in diameter).

Magnetic resonance imaging in children presenting migraine with aura: Association of hypoperfusion detected by arterial spin labelling and vasospasm on MR angiography findings.

PubMed

Cadiot, Domitille; Longuet, Romain; Bruneau, Bertrand; Treguier, Catherine; Carsin-Vu, Aline; Corouge, Isabelle; Gomes, Constantin; Proisy, Maïa

2018-04-01

Objective A child presenting with a first attack of migraine with aura usually undergoes magnetic resonance imaging (MRI) to rule out stroke. The purpose of this study was to report vascular and brain perfusion findings in children suffering from migraine with aura on time-of-flight MR angiography (TOF-MRA) and MR perfusion imaging using arterial spin labelling (ASL). Methods We retrospectively included all children who had undergone an emergency MRI examination with ASL and TOF-MRA sequences for acute neurological deficit and were given a final diagnosis of migraine with aura. The ASL perfusion maps and TOF-MRA images were independently assessed by reviewers blinded to clinical data. A mean cerebral blood flow (CBF) value was obtained for each cerebral lobe after automatic data post-processing. Results Seventeen children were finally included. Hypoperfusion was identified in one or more cerebral lobes on ASL perfusion maps by visual assessment in 16/17 (94%) children. Vasospasm was noted within the intracranial vasculature on the TOF-MRA images in 12/17 (71%) children. All (100%) of the abnormal TOF-MRA images were associated with homolateral hypoperfusion. Mean CBF values were significantly lower ( P < 0.05) in visually hypoperfused lobes than in normally perfused lobes. Conclusion ASL and TOF-MRA are two totally non-invasive, easy-to-use MRI sequences for children in emergency settings. Hypoperfusion associated with homolateral vasospasm may suggest a diagnosis of migraine with aura.

Near-infrared spectroscopy versus magnetic resonance imaging to study brain perfusion in newborns with hypoxic-ischemic encephalopathy treated with hypothermia.

PubMed

Wintermark, P; Hansen, A; Warfield, S K; Dukhovny, D; Soul, J S

2014-01-15

The measurement of brain perfusion may provide valuable information for assessment and treatment of newborns with hypoxic-ischemic encephalopathy (HIE). While arterial spin labeled perfusion (ASL) magnetic resonance imaging (MRI) provides noninvasive and direct measurements of regional cerebral blood flow (CBF) values, it is logistically challenging to obtain. Near-infrared spectroscopy (NIRS) might be an alternative, as it permits noninvasive and continuous monitoring of cerebral hemodynamics and oxygenation at the bedside. The purpose of this study is to determine the correlation between measurements of brain perfusion by NIRS and by MRI in term newborns with HIE treated with hypothermia. In this prospective cohort study, ASL-MRI and NIRS performed during hypothermia were used to assess brain perfusion in these newborns. Regional cerebral blood flow (CBF) values, measured from 1-2 MRI scans for each patient, were compared to mixed venous saturation values (SctO2) recorded by NIRS just before and after each MRI. Analysis included groupings into moderate versus severe HIE based on their initial background pattern of amplitude-integrated electroencephalogram. Twelve concomitant recordings were obtained of seven neonates. Strong correlation was found between SctO2 and CBF in asphyxiated newborns with severe HIE (r=0.88; p value=0.0085). Moreover, newborns with severe HIE had lower CBF (likely lower oxygen supply) and extracted less oxygen (likely lower oxygen demand or utilization) when comparing SctO2 and CBF to those with moderate HIE. NIRS is an effective bedside tool to monitor and understand brain perfusion changes in term asphyxiated newborns, which in conjunction with precise measurements of CBF obtained by MRI at particular times, may help tailor neuroprotective strategies in term newborns with HIE. Copyright © 2013 Elsevier Inc. All rights reserved.

Near-Infrared Spectroscopy versus Magnetic Resonance Imaging To Study Brain Perfusion in Newborns with Hypoxic-Ischemic Encephalopathy Treated with Hypothermia

PubMed Central

Wintermark, P.; Hansen, A.; Warfield, SK.; Dukhovny, D.; Soul, JS.

2014-01-01

Background The measurement of brain perfusion may provide valuable information for assessment and treatment of newborns with hypoxic-ischemic encephalopathy (HIE). While arterial spin labeled perfusion (ASL) magnetic resonance imaging (MRI) provides noninvasive and direct measurements of regional cerebral blood flow (CBF) values, it is logistically challenging to obtain. Near-infrared spectroscopy (NIRS) might be an alternative, as it permits noninvasive and continuous monitoring of cerebral hemodynamics and oxygenation at the bedside. Objective The purpose of this study is to determine the correlation between measurements of brain perfusion by NIRS and by MRI in term newborns with HIE treated with hypothermia. Design/Methods In this prospective cohort study, ASL-MRI and NIRS performed during hypothermia were used to assess brain perfusion in these newborns. Regional cerebral blood flow values (CBF), measured from 1–2 MRI scans for each patient, were compared to mixed venous saturation values (SctO2) recorded by NIRS just before and after each MRI. Analysis included groupings into moderate versus severe HIE based on their initial background pattern of amplitude-integrated electroencephalogram. Results Twelve concomitant recordings were obtained of seven neonates. Strong correlation was found between SctO2 and CBF in asphyxiated newborns with severe HIE (r = 0.88; p value = 0.0085). Moreover, newborns with severe HIE had lower CBF (likely lower oxygen supply) and extracted less oxygen (likely lower oxygen demand or utilization) when comparing SctO2 and CBF to those with moderate HIE. Conclusions NIRS is an effective bedside tool to monitor and understand brain perfusion changes in term asphyxiated newborns, which in conjunction with precise measurements of CBF obtained by MRI at particular times, may help tailor neuroprotective strategies in term newborns with HIE. PMID:23631990

Dynamic half Fourier acquisition, single shot turbo spin-echo magnetic resonance imaging for evaluating the female pelvis.

PubMed

Gousse, A E; Barbaric, Z L; Safir, M H; Madjar, S; Marumoto, A K; Raz, S

2000-11-01

We assessed the merit of dynamic half Fourier acquisition, single shot turbo spin-echo sequence T2-weighted magnetic resonance imaging (MRI) for evaluating pelvic organ prolapse and all other female pelvic pathology by prospectively correlating clinical with imaging findings. From September 1997 to April 1998, 100 consecutive women 23 to 88 years old with (65) and without (35) pelvic organ prolapse underwent half Fourier acquisition, single shot turbo spin-echo sequence dynamic pelvic T2-weighted MRI at our institution using a 1.5 Tesla magnet with phased array coils. Mid sagittal and parasagittal views with the patient supine, relaxed and straining were obtained using no pre-examination preparation or instrumentation. We evaluated the anterior vaginal wall, bladder, urethra, posterior vaginal wall, rectum, pelvic floor musculature, perineum, uterus, vaginal cuff, ovaries, ureters and intraperitoneal organs for all pathological conditions, including pelvic prolapse. Patients underwent a prospective physical examination performed by a female urologist, and an experienced radiologist blinded to pre-imaging clinical findings interpreted all studies. Physical examination, MRI and intraoperative findings were statistically correlated. Total image acquisition time was 2.5 minutes, room time 10 minutes and cost American $540. Half Fourier acquisition, single shot turbo spin-echo T2-weighted MRI revealed pathological entities other than pelvic prolapse in 55 cases, including uterine fibroids in 11, ovarian cysts in 9, bilateral ureteronephrosis in 3, nabothian cyst in 7, Bartholin's gland cyst in 4, urethral diverticulum in 3, polytetrafluoroethylene graft abscess in 3, bladder diverticulum in 2, sacral spinal abnormalities in 2, bladder tumor in 1, sigmoid diverticulosis in 1 and other in 9. Intraoperative findings were considered the gold standard against which physical examination and MRI were compared. Using these criteria the sensitivity, specificity and positive predictive value of MRI were 100%, 83% and 97% for cystocele; 100%, 75% and 94% for urethrocele; 100%, 54% and 33% for vaginal vault prolapse; 83%, 100% and 100% for uterine prolapse; 87%, 80% and 91% for enterocele; and 76%, 50% and 96% for rectocele. Dynamic half Fourier acquisition, single shot turbo spin-echo MRI appears to be an important adjunct in the comprehensive evaluation of the female pelvis. Except for rectocele, pelvic floor prolapse is accurately staged and pelvic organ pathology reliably detected. The technique is rapid, noninvasive and cost-effective, and it allows the clinician to visualize the whole pelvis using a single dynamic study that provides superb anatomical detail.

Steer-PROP: a GRASE-PROPELLER sequence with interecho steering gradient pulses.

PubMed

Srinivasan, Girish; Rangwala, Novena; Zhou, Xiaohong Joe

2018-05-01

This study demonstrates a novel PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) pulse sequence, termed Steer-PROP, based on gradient and spin echo (GRASE), to reduce the imaging times and address phase errors inherent to GRASE. The study also illustrates the feasibility of using Steer-PROP as an alternative to single-shot echo planar imaging (SS-EPI) to produce distortion-free diffusion images in all imaging planes. Steer-PROP uses a series of blip gradient pulses to produce N (N = 3-5) adjacent k-space blades in each repetition time, where N is the number of gradient echoes in a GRASE sequence. This sampling strategy enables a phase correction algorithm to systematically address the GRASE phase errors as well as the motion-induced phase inconsistency. Steer-PROP was evaluated on phantoms and healthy human subjects at both 1.5T and 3.0T for T 2 - and diffusion-weighted imaging. Steer-PROP produced similar image quality as conventional PROPELLER based on fast spin echo (FSE), while taking only a fraction (e.g., 1/3) of the scan time. The robustness against motion in Steer-PROP was comparable to that of FSE-based PROPELLER. Using Steer-PROP, high quality and distortion-free diffusion images were obtained from human subjects in all imaging planes, demonstrating a considerable advantage over SS-EPI. The proposed Steer-PROP sequence can substantially reduce the scan times compared with FSE-based PROPELLER while achieving adequate image quality. The novel k-space sampling strategy in Steer-PROP not only enables an integrated phase correction method that addresses various sources of phase errors, but also minimizes the echo spacing compared with alternative sampling strategies. Steer-PROP can also be a viable alternative to SS-EPI to decrease image distortion in all imaging planes. Magn Reson Med 79:2533-2541, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Comparing cerebrovascular reactivity measured using BOLD and cerebral blood flow MRI: The effect of basal vascular tension on vasodilatory and vasoconstrictive reactivity

PubMed Central

Halani, Sheliza; Kwinta, Jonathan B.; Golestani, Ali M.; Khatamian, Yasha B.; Chen, J. Jean

2016-01-01

Cerebrovascular reactivity (CVR) is an important metric of cerebrovascular health. While the BOLD fMRI method in conjunction with carbon-dioxide (CO2) based vascular manipulation has been the most commonly used, the BOLD signal is not a direct measure of vascular changes, and the use of arterial-spin labeling (ASL) cerebral blood flow (CBF) imaging is increasingly advocated. Nonetheless, given the differing dependencies of BOLD and CBF on vascular baseline conditions and the diverse CO2 manipulation types currently used in the literature, knowledge of potential biases introduced by each technique is critical for the interpretation of CVR measurements. In this work, we use simultaneous BOLD-CBF acquisitions during both vasodilatory (hypercapnic) and vasoconstrictive (hypocapnic) stimuli to measure CVR. We further imposed different levels of baseline vascular tension by inducing hypercapnic and hypocapnic baselines, separately from normocapnia by 4 mm Hg. We saw significant and diverse dependencies on vascular stimulus and baseline condition in both BOLD and CBF CVR measurements: (i) BOLD-based CVR is more sensitive to basal vascular tension than CBF-based CVR; (ii) the use of a combination of vasodilatory and vasoconstrictive stimuli maximizes the sensitivity of CBF-based CVR to vascular tension changes; (iii) the BOLD and CBF vascular response delays are both significantly lengthened at predilated baseline. As vascular tension can often be altered by potential pathology, our findings are important considerations when interpreting CVR measurements in health and disease. PMID:25655446

Reduced Perfusion in Broca’s Area in Developmental Stuttering

PubMed Central

Desai, Jay; Huo, Yuankai; Wang, Zhishun; Bansal, Ravi; Williams, Steven C. R.; Lythgoe, David; Zelaya, Fernando O.; Peterson, Bradley S.

2016-01-01

Objective To study resting cerebral blood flow in children and adults with developmental stuttering. Methods We acquired pulsed arterial spin labeling magnetic resonance imaging data in 26 participants with stuttering and 36 healthy, fluent controls. While covarying for age, sex, and IQ, we compared perfusion values voxel-wise across diagnostic groups and assessed correlations of perfusion with stuttering severity within the stuttering group and with measures of motor speed in both groups. Results We detected lower regional Cerebral Blood Flow (rCBF) at rest in the stuttering group compared to healthy controls in Broca’s area bilaterally and the superior frontal gyrus. rCBF values in Broca’s area bilaterally correlated inversely with the severity of stuttering and extended posteriorly into other portions of the language loop. We also found increased rCBF in cerebellar nuclei and parietal cortex in the stuttering group compared to healthy controls. Findings were unchanged in child-only analyses and when excluding participants with comorbid illnesses or those taking medication. Conclusions rCBF is reduced in Broca’s region in persons who stutter. More severe stuttering is associated with even greater reductions in rCBF to Broca’s region, additive to the underlying putative trait reduction in rCBF relative to control values. Moreover, a greater abnormality in rCBF in the posterior language loop is associated with more severe symptoms, suggesting that a common pathophysiology throughout the language loop likely contributes to stuttering severity. PMID:28035724

Reduced perfusion in Broca's area in developmental stuttering.

PubMed

Desai, Jay; Huo, Yuankai; Wang, Zhishun; Bansal, Ravi; Williams, Steven C R; Lythgoe, David; Zelaya, Fernando O; Peterson, Bradley S

2017-04-01

To study resting cerebral blood flow in children and adults with developmental stuttering. We acquired pulsed arterial spin labeling magnetic resonance imaging data in 26 participants with stuttering and 36 healthy, fluent controls. While covarying for age, sex, and IQ, we compared perfusion values voxel-wise across diagnostic groups and assessed correlations of perfusion with stuttering severity within the stuttering group and with measures of motor speed in both groups. We detected lower regional Cerebral Blood Flow (rCBF) at rest in the stuttering group compared with healthy controls in Broca's area bilaterally and the superior frontal gyrus. rCBF values in Broca's area bilaterally correlated inversely with the severity of stuttering and extended posteriorly into other portions of the language loop. We also found increased rCBF in cerebellar nuclei and parietal cortex in the stuttering group compared with healthy controls. Findings were unchanged in child-only analyses and when excluding participants with comorbid illnesses or those taking medication. rCBF is reduced in Broca's region in persons who stutter. More severe stuttering is associated with even greater reductions in rCBF to Broca's region, additive to the underlying putative trait reduction in rCBF relative to control values. Moreover, a greater abnormality in rCBF in the posterior language loop is associated with more severe symptoms, suggesting that a common pathophysiology throughout the language loop likely contributes to stuttering severity. Hum Brain Mapp 38:1865-1874, 2017. © 2017 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Reduced perfusion in normal-appearing white matter in mild to moderate hypertension as revealed by 3D pseudocontinuous arterial spin labeling.

PubMed

Wang, Ting; Li, Yanhua; Guo, Xinhong; Huang, Diandian; Ma, Lin; Wang, Danny J J; Lou, Xin

2016-03-01

To investigate the hemodynamic changes of normal-appearing white matter (NAWM) in hypertension using the 3D pseudocontinuous arterial spin labeling (pCASL) technique. Seventy-three subjects, including a patient group (n = 41; 30 males; age = 47.7 ± 8.3 years; test-time blood pressure [BP] = 155 ± 23/98 ± 11 mmHg) and an age-matched control group (n = 32; 14 males; age = 46 ± 8.3 years; test-time BP = 117 ± 8/76 ± 10 mmHg), were recruited and scanned on a 3.0T magnetic resonance imaging (MRI) system using routine MRI sequences and 3D pCASL sequence. The routine MRI sequences were used to further define the NAWM. The cerebral blood flow (CBF) values in various regions of interest (ROIs) were extracted. One-way analysis of variance (ANOVA) and unpaired t-test were performed to evaluate the significance of the intergroup difference in CBF modifications. Compared to healthy volunteers, CBF values in global gray matter (GM) and various NAWM regions were found to be lower (P < 0.05) in hypertensive patients, except for genu of corpus callosum (CC), cingulate gyrus, amygdala, pallidum, putamen, and thalamus (P > 0.05). Furthermore, compared to the control group, mild hypertension showed significantly reduced CBF in various ROIs (P < 0.05), but no intergroup differences in GM, R anterior horn of periventricular WM, and genu of CC (P > 0.05), while moderate hypertension showed reduced CBF in all ROIs (P < 0.05). However, it was observed that, between mild and moderate hypertensive patients, there were no statistically significant difference in CBF values except for genu of CC (P < 0.05). 3D pCASL has the ability to detect subtle hemodynamic abnormalities in NAWM regions at relatively early stages of hypertension. The observed decreases in CBF in these regions may suggest an increased risk of cerebral small vessel diseases. © 2015 Wiley Periodicals, Inc.

3D polymer gel dosimetry using a 3D (DESS) and a 2D MultiEcho SE (MESE) sequence

NASA Astrophysics Data System (ADS)

Maris, Thomas G.; Pappas, Evangelos; Karolemeas, Kostantinos; Papadakis, Antonios E.; Zacharopoulou, Fotini; Papanikolaou, Nickolas; Gourtsoyiannis, Nicholas

2006-12-01

The utilization of 3D techniques in Magnetic Resonance Imaging data aquisition and post-processing analysis is a prerequisite especially when modern radiotherapy techniques (conformal RT, IMRT, Stereotactic RT) are to be used. The aim of this work is to compare a 3D Double Echo Steady State (DESS) and a 2D Multiple Echo Spin Echo (MESE) sequence in 3D MRI radiation dosimetry using two different MRI scanners and utilising N-VInylPyrrolidone (VIPAR) based polymer gels.

76 FR 67200 - Prospective Grant of Exclusive License: Electron Paramagnetic Resonance Devices and Systems for...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-31

... that is a unique combination of: (1) multi-gradient Single Point Imaging involving global phase...-encoding gradients. The combination approach of single point imaging with the spin-echo signal detection...

Skin age testing criteria: characterization of human skin structures by 500 MHz MRI multiple contrast and image processing.

PubMed

Sharma, Rakesh

2010-07-21

Ex vivo magnetic resonance microimaging (MRM) image characteristics are reported in human skin samples in different age groups. Human excised skin samples were imaged using a custom coil placed inside a 500 MHz NMR imager for high-resolution microimaging. Skin MRI images were processed for characterization of different skin structures. Contiguous cross-sectional T1-weighted 3D spin echo MRI, T2-weighted 3D spin echo MRI and proton density images were compared with skin histopathology and NMR peaks. In all skin specimens, epidermis and dermis thickening and hair follicle size were measured using MRM. Optimized parameters TE and TR and multicontrast enhancement generated better MRI visibility of different skin components. Within high MR signal regions near to the custom coil, MRI images with short echo time were comparable with digitized histological sections for skin structures of the epidermis, dermis and hair follicles in 6 (67%) of the nine specimens. Skin % tissue composition, measurement of the epidermis, dermis, sebaceous gland and hair follicle size, and skin NMR peaks were signatures of skin type. The image processing determined the dimensionality of skin tissue components and skin typing. The ex vivo MRI images and histopathology of the skin may be used to measure the skin structure and skin NMR peaks with image processing may be a tool for determining skin typing and skin composition.

Skin age testing criteria: characterization of human skin structures by 500 MHz MRI multiple contrast and image processing

NASA Astrophysics Data System (ADS)

Sharma, Rakesh

2010-07-01

Ex vivo magnetic resonance microimaging (MRM) image characteristics are reported in human skin samples in different age groups. Human excised skin samples were imaged using a custom coil placed inside a 500 MHz NMR imager for high-resolution microimaging. Skin MRI images were processed for characterization of different skin structures. Contiguous cross-sectional T1-weighted 3D spin echo MRI, T2-weighted 3D spin echo MRI and proton density images were compared with skin histopathology and NMR peaks. In all skin specimens, epidermis and dermis thickening and hair follicle size were measured using MRM. Optimized parameters TE and TR and multicontrast enhancement generated better MRI visibility of different skin components. Within high MR signal regions near to the custom coil, MRI images with short echo time were comparable with digitized histological sections for skin structures of the epidermis, dermis and hair follicles in 6 (67%) of the nine specimens. Skin % tissue composition, measurement of the epidermis, dermis, sebaceous gland and hair follicle size, and skin NMR peaks were signatures of skin type. The image processing determined the dimensionality of skin tissue components and skin typing. The ex vivo MRI images and histopathology of the skin may be used to measure the skin structure and skin NMR peaks with image processing may be a tool for determining skin typing and skin composition.

Altered cerebral blood flow and neurocognitive correlates in adolescent cannabis users

PubMed Central

Jacobus, Joanna; Goldenberg, Diane; Wierenga, Christina E.; Tolentino, Neil J.; Liu, Thomas T.

2012-01-01

Rationale The effects of adolescent marijuana use on the developing brain remain unclear, despite its prevalence. Arterial spin labeling (ASL) is a noninvasive imaging technique that characterizes neurovascular status and cerebral blood flow (CBF), potentially revealing contributors to neuropathological alterations. No studies to date have looked at CBF in adolescent marijuana users. Objectives This study examined CBF in adolescent marijuana users and matched healthy controls at baseline and after 4 weeks of monitored abstinence. Methods Heavy adolescent marijuana users (n=23, >200 lifetime marijuana use days) and demographically matched controls (n=23) with limited substance exposure underwent an ASL brain scan at an initial session and after 4 weeks of sequential urine toxicology to confirm abstinence. Results Marijuana users showed reduced CBF in four cortical regions including the left superior and middle temporal gyri, left insula, left and right medial frontal gyrus, and left supramarginal gyrus at baseline; users showed increased CBF in the right precuneus at baseline, as compared to controls (corrected p values<0.05). No between group differences were found at follow-up. Conclusions Marijuana use may influence CBF in otherwise healthy adolescents acutely; however, group differences were not observed after several weeks of abstinence. Neurovascular alterations may contribute to or underlie changes in brain activation, neuropsychological performance, and mood observed in young cannabis users with less than a month of abstinence. PMID:22395430

Contrast-Enhanced Magnetic Resonance Cholangiography: Practical Tips and Clinical Indications for Biliary Disease Management.

PubMed

Palmucci, Stefano; Roccasalva, Federica; Piccoli, Marina; Fuccio Sanzà, Giovanni; Foti, Pietro Valerio; Ragozzino, Alfonso; Milone, Pietro; Ettorre, Giovanni Carlo

2017-01-01

Since its introduction, MRCP has been improved over the years due to the introduction of several technical advances and innovations. It consists of a noninvasive method for biliary tree representation, based on heavily T2-weighted images. Conventionally, its protocol includes two-dimensional single-shot fast spin-echo images, acquired with thin sections or with multiple thick slabs. In recent years, three-dimensional T2-weighted fast-recovery fast spin-echo images have been added to the conventional protocol, increasing the possibility of biliary anatomy demonstration and leading to a significant benefit over conventional 2D imaging. A significant innovation has been reached with the introduction of hepatobiliary contrasts, represented by gadoxetic acid and gadobenate dimeglumine: they are excreted into the bile canaliculi, allowing the opacification of the biliary tree. Recently, 3D interpolated T1-weighted spoiled gradient echo images have been proposed for the evaluation of the biliary tree, obtaining images after hepatobiliary contrast agent administration. Thus, the acquisition of these excretory phases improves the diagnostic capability of conventional MRCP-based on T2 acquisitions. In this paper, technical features of contrast-enhanced magnetic resonance cholangiography are briefly discussed; main diagnostic tips of hepatobiliary phase are showed, emphasizing the benefit of enhanced cholangiography in comparison with conventional MRCP.

Quantification of normal cerebral oxygen extraction and oxygen metabolism by phase-based MRI susceptometry: evaluation of repeatability using two different imaging protocols.

PubMed

Kämpe, Robin; Lind, Emelie; Ståhlberg, Freddy; van Westen, Danielle; Knutsson, Linda; Wirestam, Ronnie

2017-03-01

Global oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO 2 ) were quantified in a test-retest study. Cerebral blood flow (CBF) data, required for CMRO 2 estimation, were obtained using dynamic susceptibility contrast MRI (DSC-MRI). OEF and CMRO 2 were quantified using two separate data sets, that is, conventional high-resolution (HR) gradient echo (GRE) phase maps as well as echo planar imaging (EPI) phase maps taken from the baseline (precontrast) part of the DSC-MRI time series. The EPI phase data were included to elucidate whether an extra HR-GRE scan is needed to obtain information about OEF and CMRO 2 , or if this information can be extracted from the DSC-MRI experiment only. Twenty healthy volunteers were scanned using 3 T MRI on two occasions. Oxygen saturation levels were obtained from phase data measured in the great cerebral vein of Galen, based on HR-GRE as well as EPI phase maps. In combination with DSC-MRI CBF, this allowed for calculation of OEF and CMRO 2 . High-resolution-gradient echo- and EPI-based phase images resulted in similar OEF spread and repeatability, with coefficients of variation/intraclass correlation coefficients of 0·26/0·95 and 0·23/0·81, respectively. Absolute OEF values (HR-GRE: 0·40 ± 0·11, EPI: 0·35 ± 0·08) were consistent with literature data. CMRO 2 showed similar repeatability, somewhat increased spread and reasonable absolute values (HR-GRE: 3·23 ± 1·26 ml O 2 /100 g min -1 , EPI: 2·79 ± 0·89 ml O 2 /100 g min -1 ). In general, the results obtained by HR-GRE and EPI showed comparable characteristics. The EPI methodology could potentially be improved using a slightly modified DSC-MRI protocol (e.g. with regard to spatial resolution and slice gap). © 2015 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

SU-E-I-65: Estimation of Tagging Efficiency in Pseudo-Continuous Arterial Spin Labeling (pCASL) MRI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jen, M; Yan, F; Tseng, Y

2015-06-15

Purpose: pCASL was recommended as a potent approach for absolute cerebral blood flow (CBF) quantification in clinical practice. However, uncertainties of tagging efficiency in pCASL remain an issue. This study aimed to estimate tagging efficiency by using short quantitative pulsed ASL scan (FAIR-QUIPSSII) and compare resultant CBF values with those calibrated by using 2D Phase Contrast (PC) MRI. Methods: Fourteen normal volunteers participated in this study. All images, including whole brain (WB) pCASL, WB FAIR-QUIPSSII and single-slice 2D PC, were collected on a 3T clinical MRI scanner with a 8-channel head coil. DeltaM map was calculated by averaging the subtractionmore » of tag/control pairs in pCASL and FAIR-QUIPSSII images and used for CBF calculation. Tagging efficiency was then calculated by the ratio of mean gray matter CBF obtained from pCASL and FAIR-QUIPSSII. For comparison, tagging efficiency was also estimated with 2D PC, a previously established method, by contrast WB CBF in pCASL and 2D PC. Feasibility of estimation from a short FAIR-QUIPSSII scan was evaluated by number of averages required for obtaining a stable deltaM value. Setting deltaM calculated by maximum number of averaging (50 pairs) as reference, stable results were defined within ±10% variation. Results: Tagging efficiencies obtained by 2D PC MRI (0.732±0.092) were significantly lower than which obtained by FAIRQUIPPSSII (0.846±0.097) (P<0.05). Feasibility results revealed that four pairs of images in FAIR-QUIPPSSII scan were sufficient to obtain a robust calibration of less than 10% differences from using 50 pairs. Conclusion: This study found that reliable estimation of tagging efficiency could be obtained by a few pairs of FAIR-QUIPSSII images, which suggested that calibration scan in a short duration (within 30s) was feasible. Considering recent reports concerning variability of PC MRI-based calibration, this study proposed an effective alternative for CBF quantification with pCASL.« less

Contrast-enhanced fluid-attenuated inversion recovery vs. contrast-enhanced spin echo T1-weighted brain imaging.

PubMed

Falzone, Cristian; Rossi, Federica; Calistri, Maurizio; Tranquillo, Massimo; Baroni, Massimo

2008-01-01

In humans, contrast-enhanced fluid-attenuated inversion recovery (FLAIR) imaging plays an important role in detecting brain disease. The aim of this study was to define the clinical utility of contrast-enhanced FLAIR imaging by comparing the results with those with contrast-enhanced spin echo T1-weighted images (SE T1WI) in animals with different brain disorders. Forty-one dogs and five cats with a clinical suspicion of brain disease and 30 normal animals (25 dogs and five cats) were evaluated using a 0.2 T permanent magnet. Before contrast medium injection, spin echo T1-weighted, SE T1WI, and FLAIR sequences were acquired in three planes. SE T1WI and FLAIR images were also acquired after gadolinium injection. Sensitivity in detecting the number, location, margin, and enhancement pattern and rate were evaluated. No lesions were found in a normal animal. In affected animals, 48 lesions in 34 patients were detected in contrast-enhanced SE T1WI whereas 81 lesions in 44 patients were detected in contrast-enhanced FLAIR images. There was no difference in the characteristics of the margins or enhancement pattern of the detected lesions. The objective enhancement rate, the mean value between lesion-to-white matter ratio and lesion-to-gray matter ratio, although representing an overlap of T1 and T2 effects and not pure contrast medium shortening of T1 relaxation, was better in contrast-enhanced FLAIR images. These results suggest a superiority of contrast-enhanced FLAIR images as compared with contrast-enhanced SE T1WI in detecting enhancing brain lesions.

T2-Weighted Dixon Turbo Spin Echo for Accelerated Simultaneous Grading of Whole-Body Skeletal Muscle Fat Infiltration and Edema in Patients With Neuromuscular Diseases.

PubMed

Schlaeger, Sarah; Klupp, Elisabeth; Weidlich, Dominik; Cervantes, Barbara; Foreman, Sarah C; Deschauer, Marcus; Schoser, Benedikt; Katemann, Christoph; Kooijman, Hendrik; Rummeny, Ernst J; Zimmer, Claus; Kirschke, Jan S; Karampinos, Dimitrios C

2018-04-02

The assessment of fatty infiltration and edema in the musculature of patients with neuromuscular diseases (NMDs) typically requires the separate performance of T1-weighted and fat-suppressed T2-weighted sequences. T2-weighted Dixon turbo spin echo (TSE) enables the generation of T2-weighted fat- and water-separated images, which can be used to assess both pathologies simultaneously. The present study examines the diagnostic performance of T2-weighted Dixon TSE compared with the standard sequences in 10 patients with NMDs and 10 healthy subjects. Whole-body magnetic resonance imaging was performed including T1-weighted Dixon fast field echo, T2-weighted short-tau inversion recovery, and T2-weighted Dixon TSE. Fatty infiltration and intramuscular edema were rated by 2 radiologists using visual semiquantitative rating scales. To assess intermethod and interrater agreement, weighted Cohen's κ coefficients were calculated. The ratings of fatty infiltration showed high intermethod and high interrater agreement (T1-weighted Dixon fast field echo vs T2-weighted Dixon TSE fat image). The evaluation of edematous changes showed high intermethod and good interrater agreement (T2-weighted short-tau inversion recovery vs T2-weighted Dixon TSE water image). T2-weighted Dixon TSE imaging is an alternative for accelerated simultaneous grading of whole-body skeletal muscle fat infiltration and edema in patients with NMDs.

Patient-Specific Detection of Cerebral Blood Flow Alterations as Assessed by Arterial Spin Labeling in Drug-Resistant Epileptic Patients

PubMed Central

Boscolo Galazzo, Ilaria; Storti, Silvia Francesca; Del Felice, Alessandra; Pizzini, Francesca Benedetta; Arcaro, Chiara; Formaggio, Emanuela; Mai, Roberto; Chappell, Michael; Beltramello, Alberto; Manganotti, Paolo

2015-01-01

Electrophysiological and hemodynamic data can be integrated to accurately and precisely identify the generators of abnormal electrical activity in drug-resistant focal epilepsy. Arterial Spin Labeling (ASL), a magnetic resonance imaging (MRI) technique for quantitative noninvasive measurement of cerebral blood flow (CBF), can provide a direct measure of variations in cerebral perfusion associated with the epileptic focus. In this study, we aimed to confirm the ASL diagnostic value in the identification of the epileptogenic zone, as compared to electrical source imaging (ESI) results, and to apply a template-based approach to depict statistically significant CBF alterations. Standard video-electroencephalography (EEG), high-density EEG, and ASL were performed to identify clinical seizure semiology and noninvasively localize the epileptic focus in 12 drug-resistant focal epilepsy patients. The same ASL protocol was applied to a control group of 17 healthy volunteers from which a normal perfusion template was constructed using a mixed-effect approach. CBF maps of each patient were then statistically compared to the reference template to identify perfusion alterations. Significant hypo- and hyperperfused areas were identified in all cases, showing good agreement between ASL and ESI results. Interictal hypoperfusion was observed at the site of the seizure in 10/12 patients and early postictal hyperperfusion in 2/12. The epileptic focus was correctly identified within the surgical resection margins in the 5 patients who underwent lobectomy, all of which had good postsurgical outcomes. The combined use of ESI and ASL can aid in the noninvasive evaluation of drug-resistant epileptic patients. PMID:25946055

WE-FG-206-05: New Arterial Spin Labeling Method for Simultaneous Estimation of Arterial Cerebral Blood Volume, Cerebral Blood Flow and Arterial Transit Time

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnston, M; Whitlow, C; Jung, Y

Purpose: To demonstrate the feasibility of a novel Arterial Spin Labeling (ASL) method for simultaneously measuring cerebral blood flow (CBF), arterial transit time (ATT), and arterial cerebral blood volume (aCBV) without the use of a contrast agent. Methods: A series of multi-TI ASL images were acquired from one healthy subject on a 3T Siemens Skyra, with the following parameters: PCASL labeling with variable TI [300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000] ms, labeling bolus 1400 ms when TI allows, otherwise 100 ms less than TI, TR was minimized for each TI, two sincmore » shaped pre-saturation pulses were applied in the imaging plane immediately before 2D EPI acquisition. 64×64×24 voxels, 5 mm slice thickness, 1 mm gap, full brain coverage, 6 averages per TI, no crusher gradients, 11 ms TE, scan time of 4:56. The perfusion weighted time-series was created for each voxel and fit to a novel model. The model has two components: 1) the traditional model developed by Buxton et al., accounting for CBF and ATT, and 2) a box car function characterizing the width of the labeling bolus, with variable timing and height in proportion to the aCBV. All three parameters were fit using a nonlinear fitting routine that constrained all parameters to be positive. The main purpose of the high-temporal resolution TI sampling for the first second of data acquisition was to precisely estimate the blood volume component for better detection of arrival time and magnitude of signal. Results: Whole brain maps of CBF, ATT, and aCBV were produced, and all three parameters maps are consistent with similar maps described in the literature. Conclusion: Simultaneous mapping of CBF, ATT, and aCBV is feasible with a clinically tractable scan time (under 5 minutes).« less

X-ray Echo Spectroscopy

NASA Astrophysics Data System (ADS)

Shvyd'ko, Yuri

2016-02-01

X-ray echo spectroscopy, a counterpart of neutron spin echo, is being introduced here to overcome limitations in spectral resolution and weak signals of the traditional inelastic x-ray scattering (IXS) probes. An image of a pointlike x-ray source is defocused by a dispersing system comprised of asymmetrically cut specially arranged Bragg diffracting crystals. The defocused image is refocused into a point (echo) in a time-reversal dispersing system. If the defocused beam is inelastically scattered from a sample, the echo signal acquires a spatial distribution, which is a map of the inelastic scattering spectrum. The spectral resolution of the echo spectroscopy does not rely on the monochromaticity of the x rays, ensuring strong signals along with a very high spectral resolution. Particular schemes of x-ray echo spectrometers for 0.1-0.02 meV ultrahigh-resolution IXS applications (resolving power >108 ) with broadband ≃5 - 13 meV dispersing systems are introduced featuring more than 103 signal enhancement. The technique is general, applicable in different photon frequency domains.

Optimization of diffusion-weighted single-refocused spin-echo EPI by reducing eddy-current artifacts and shortening the echo time.

PubMed

Shrestha, Manoj; Hok, Pavel; Nöth, Ulrike; Lienerth, Bianca; Deichmann, Ralf

2018-03-30

The purpose of this work was to optimize the acquisition of diffusion-weighted (DW) single-refocused spin-echo (srSE) data without intrinsic eddy-current compensation (ECC) for an improved performance of ECC postprocessing. The rationale is that srSE sequences without ECC may yield shorter echo times (TE) and thus higher signal-to-noise ratios (SNR) than srSE or twice-refocused spin-echo (trSE) schemes with intrinsic ECC. The proposed method employs dummy scans with DW gradients to drive eddy currents into a steady state before data acquisition. Parameters of the ECC postprocessing algorithm were also optimized. Simulations were performed to obtain minimum TE values for the proposed sequence and sequences with intrinsic ECC. Experimentally, the proposed method was compared with standard DW-trSE imaging, both in vitro and in vivo. Simulations showed substantially shorter TE for the proposed method than for methods with intrinsic ECC when using shortened echo readouts. Data of the proposed method showed a marked increase in SNR. A dummy scan duration of at least 1.5 s improved performance of the ECC postprocessing algorithm. Changes proposed for the DW-srSE sequence and for the parameter setting of the postprocessing ECC algorithm considerably reduced eddy-current artifacts and provided a higher SNR.

Noninvasive imaging of brain oxygen metabolism in children with primary nocturnal enuresis during natural sleep.

PubMed

Yu, Bing; Huang, Mingzhu; Zhang, Xu; Ma, Hongwei; Peng, Miao; Guo, Qiyong

2017-05-01

A series of studies have revealed that nocturnal enuresis is closely related to hypoxia in children with primary nocturnal enuresis (PNE). However, brain oxygen metabolism of PNE children has not been investigated before. The purpose of this study was to investigate changes in whole-brain cerebral metabolic rate of oxygen (CMRO 2 ), cerebral blood flow (CBF), and oxygen extraction fraction (OEF) in children suffering from PNE. We used the newly developed T2-relaxation-under-spin-tagging (TRUST) magnetic resonance imaging technique. Neurological evaluation, structural imaging, phase-contrast, and the TRUST imaging method were applied in children with PNE (n = 37) and healthy age- and sex-matched control volunteers (n = 39) during natural sleep to assess whole-brain CMRO 2 , CBF, OEF, and arousal from sleep scores. Results showed that whole-brain CMRO 2 and OEF values of PNE children were higher in controls, while there was no significant difference in CBF. Consequently, OEF levels of PNE children were increased to maintain oxygen supply. The elevation of OEF was positively correlated with the difficulty of arousal. Our results provide the first evidence that high oxygen consumption and high OEF values could make PNE children more susceptible to hypoxia, which may induce cumulative arousal deficits and make them more prone to nocturnal enuresis. Hum Brain Mapp 38:2532-2539, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

High Slew-Rate Head-Only Gradient for Improving Distortion in Echo Planar Imaging: Preliminary Experience

PubMed Central

Tan, Ek T.; Lee, Seung-Kyun; Weavers, Paul T.; Graziani, Dominic; Piel, Joseph E.; Shu, Yunhong; Huston, John; Bernstein, Matt A.; Foo, Thomas K.F.

2016-01-01

Purpose To investigate the effects on echo planar imaging (EPI) distortion of using high gradient slew rates (SR) of up to 700 T/m/s for in-vivo human brain imaging, with a dedicated, head-only gradient coil. Materials and Methods Simulation studies were first performed to determine the expected echo spacing and distortion reduction in EPI. A head gradient of 42-cm inner diameter and with asymmetric transverse coils was then installed in a whole-body, conventional 3T MRI system. Human subject imaging was performed on five subjects to determine the effects of EPI on echo spacing and signal dropout at various gradient slew rates. The feasibility of whole-brain imaging at 1.5 mm-isotropic spatial resolution was demonstrated with gradient-echo and spin-echo diffusion-weighted EPI. Results As compared to a whole-body gradient coil, the EPI echo spacing in the head-only gradient coil was reduced by 48%. Simulation and in vivo results, respectively, showed up to 25-26% and 19% improvement in signal dropout. Whole-brain imaging with EPI at 1.5 mm spatial resolution provided good whole-brain coverage, spatial linearity, and low spatial distortion effects. Conclusion Our results of human brain imaging with EPI using the compact head gradient coil at slew rates higher than in conventional whole-body MR systems demonstrate substantially improved image distortion, and point to a potential for benefits to non-EPI pulse sequences. PMID:26921117

3D hybrid profile order technique in a single breath-hold 3D T2-weighted fast spin-echo sequence: Usefulness in diagnosis of small liver lesions.

PubMed

Hirata, Kenichiro; Nakaura, Takeshi; Okuaki, Tomoyuki; Tsuda, Noriko; Taguchi, Narumi; Oda, Seitaro; Utsunomiya, Daisuke; Yamashita, Yasuyuki

2018-01-01

We compared the efficacy of three-dimensional (3D) isotropic T2-weighted fast spin-echo imaging using a 3D hybrid profile order technique with a single-breath-hold (3D-Hybrid BH) with a two-dimensional (2D) T2-weighted fast spin-echo conventional respiratory-gated (2D-Conventional RG) technique for visualising small liver lesions. This study was approved by our institutional review board. The requirement to obtain written informed consent was waived. Fifty patients with small (≤15mm) hepatocellular carcinomas (HCC) (n=26), or benign cysts (n=24), had undergone hepatic MRI including both 2D-Conventional RG and 3D-Hybrid BH. We calculated the signal-to-noise ratio (SNR) and tumour-to-liver contrast (TLC). The diagnostic performance of the two protocols was analysed. The image acquisition time was 89% shorter with the 3D-Hybrid BH than with 2D-Conventional RG. There was no significant difference in the SNR between the two protocols. The area under the curve (AUC) of the TLC was significantly higher on 3D-Hybrid BH than on 2D-Conventional RG. The 3D-Hybrid BH sequence significantly improved diagnostic performance for small liver lesions with a shorter image acquisition time without sacrificing accuracy. Copyright © 2017. Published by Elsevier B.V.

An MRI system for imaging neonates in the NICU: initial feasibility study.

PubMed

Tkach, Jean A; Hillman, Noah H; Jobe, Alan H; Loew, Wolfgang; Pratt, Ron G; Daniels, Barret R; Kallapur, Suhas G; Kline-Fath, Beth M; Merhar, Stephanie L; Giaquinto, Randy O; Winter, Patrick M; Li, Yu; Ikegami, Machiko; Whitsett, Jeffrey A; Dumoulin, Charles L

2012-11-01

Transporting premature infants from a neonatal intensive care unit (NICU) to a radiology department for MRI has medical risks and logistical challenges. To develop a small 1.5-T MRI system for neonatal imaging that can be easily installed in the NICU and to evaluate its performance using a sheep model of human prematurity. A 1.5-T MRI system designed for orthopedic use was adapted for neonatal imaging. The system was used for MRI examinations of the brain, chest and abdomen in 12 premature lambs during the first hours of life. Spin-echo, fast spin-echo and gradient-echo MR images were evaluated by two pediatric radiologists. All animals remained physiologically stable throughout the imaging sessions. Animals were imaged at two or three time points. Seven brain MRI examinations were performed in seven different animals, 23 chest examinations in 12 animals and 19 abdominal examinations in 11 animals. At each anatomical location, high-quality images demonstrating good spatial resolution, signal-to-noise ratio and tissue contrast were routinely obtained within 30 min using standard clinical protocols. Our preliminary experience demonstrates the feasibility and potential of the neonatal MRI system to provide state-of-the-art MRI capabilities within the NICU. Advantages include overall reduced cost and site demands, lower acoustic noise, improved ease of access and reduced medical risk to the neonate.

High slew-rate head-only gradient for improving distortion in echo planar imaging: Preliminary experience.

PubMed

Tan, Ek T; Lee, Seung-Kyun; Weavers, Paul T; Graziani, Dominic; Piel, Joseph E; Shu, Yunhong; Huston, John; Bernstein, Matt A; Foo, Thomas K F

2016-09-01

To investigate the effects on echo planar imaging (EPI) distortion of using high gradient slew rates (SR) of up to 700 T/m/s for in vivo human brain imaging, with a dedicated, head-only gradient coil. Simulation studies were first performed to determine the expected echo spacing and distortion reduction in EPI. A head gradient of 42-cm inner diameter and with asymmetric transverse coils was then installed in a whole-body, conventional 3T magnetic resonance imaging (MRI) system. Human subject imaging was performed on five subjects to determine the effects of EPI on echo spacing and signal dropout at various gradient slew rates. The feasibility of whole-brain imaging at 1.5 mm-isotropic spatial resolution was demonstrated with gradient-echo and spin-echo diffusion-weighted EPI. As compared to a whole-body gradient coil, the EPI echo spacing in the head-only gradient coil was reduced by 48%. Simulation and in vivo results, respectively, showed up to 25-26% and 19% improvement in signal dropout. Whole-brain imaging with EPI at 1.5 mm spatial resolution provided good whole-brain coverage, spatial linearity, and low spatial distortion effects. Our results of human brain imaging with EPI using the compact head gradient coil at slew rates higher than in conventional whole-body MR systems demonstrate substantially improved image distortion, and point to a potential for benefits to non-EPI pulse sequences. J. Magn. Reson. Imaging 2016;44:653-664. © 2016 International Society for Magnetic Resonance in Medicine.

Determination of the rCBF in the Amygdala and Rhinal Cortex Using a FAIR-TrueFISP Sequence

PubMed Central

Martirosian, Petros; Klose, Uwe; Nägele, Thomas; Schick, Fritz; Ernemann, Ulrike

2011-01-01

Objective Brain perfusion can be assessed non-invasively by modern arterial spin labeling MRI. The FAIR (flow-sensitive alternating inversion recovery)-TrueFISP (true fast imaging in steady precession) technique was applied for regional assessment of cerebral blood flow in brain areas close to the skull base, since this approach provides low sensitivity to magnetic susceptibility effects. The investigation of the rhinal cortex and the amygdala is a potentially important feature for the diagnosis and research on dementia in its early stages. Materials and Methods Twenty-three subjects with no structural or psychological impairment were investigated. FAIR-True-FISP quantitative perfusion data were evaluated in the amygdala on both sides and in the pons. A preparation of the radiofrequency FOCI (frequency offset corrected inversion) pulse was used for slice selective inversion. After a time delay of 1.2 sec, data acquisition began. Imaging slice thickness was 5 mm and inversion slab thickness for slice selective inversion was 12.5 mm. Image matrix size for perfusion images was 64 × 64 with a field of view of 256 × 256 mm, resulting in a spatial resolution of 4 × 4 × 5 mm. Repetition time was 4.8 ms; echo time was 2.4 ms. Acquisition time for the 50 sets of FAIR images was 6:56 min. Data were compared with perfusion data from the literature. Results Perfusion values in the right amygdala, left amygdala and pons were 65.2 (± 18.2) mL/100 g/minute, 64.6 (± 21.0) mL/100 g/minute, and 74.4 (± 19.3) mL/100 g/minute, respectively. These values were higher than formerly published data using continuous arterial spin labeling but similar to 15O-PET (oxygen-15 positron emission tomography) data. Conclusion The FAIR-TrueFISP approach is feasible for the quantitative assessment of perfusion in the amygdala. Data are comparable with formerly published data from the literature. The applied technique provided excellent image quality, even for brain regions located at the skull base in the vicinity of marked susceptibility steps. PMID:21927556

A spin echo sequence with a single-sided bipolar diffusion gradient pulse to obtain snapshot diffusion weighted images in moving media

NASA Astrophysics Data System (ADS)

Freidlin, R. Z.; Kakareka, J. W.; Pohida, T. J.; Komlosh, M. E.; Basser, P. J.

2012-08-01

In vivo MRI data can be corrupted by motion. Motion artifacts are particularly troublesome in Diffusion Weighted MRI (DWI), since the MR signal attenuation due to Brownian motion can be much less than the signal loss due to dephasing from other types of complex tissue motion, which can significantly degrade the estimation of self-diffusion coefficients, diffusion tensors, etc. This paper describes a snapshot DWI sequence, which utilizes a novel single-sided bipolar diffusion sensitizing gradient pulse within a spin echo sequence. The proposed method shortens the diffusion time by applying a single refocused bipolar diffusion gradient on one side of a refocusing RF pulse, instead of a set of diffusion sensitizing gradients, separated by a refocusing RF pulse, while reducing the impact of magnetic field inhomogeneity by using a spin echo sequence. A novel MRI phantom that can exhibit a range of complex motions was designed to demonstrate the robustness of the proposed DWI sequence.

Three- and four-dimensional reconstruction of intra-cardiac anatomy from two-dimensional magnetic resonance images.

PubMed

Miquel, M E; Hill, D L G; Baker, E J; Qureshi, S A; Simon, R D B; Keevil, S F; Razavi, R S

2003-06-01

The present study was designed to evaluate the feasibility and clinical usefulness of three-dimensional (3D) reconstruction of intra-cardiac anatomy from a series of two-dimensional (2D) MR images using commercially available software. Sixteen patients (eight with structurally normal hearts but due to have catheter radio-frequency ablation of atrial tachyarrhythmias and eight with atrial septal defects (ASD) due for trans-catheter closure) and two volunteers were imaged at 1T. For each patient, a series of ECG-triggered images (5 mm thick slices, 2-3 mm apart) were acquired during breath holding. Depending on image quality, T1- or T2-weighted spin-echo images or gradient-echo cine images were used. The 3D reconstruction was performed off-line: the blood pools within cardiac chambers and great vessels were semi-automatically segmented, their outer surface was extracted using a marching cube algorithm and rendered. Intra- and inter-observer variability, effect of breath-hold position and differences between pulse sequences were assessed by imaging a volunteer. The 3D reconstructions were assessed by three cardiologists and compared with the 2D MR images and with 2D and 3D trans-esophagal and intra-cardiac echocardiography obtained during interventions. In every case, an anatomically detailed 3D volume was obtained. In the two patients where a 3 mm interval between slices was used, the resolution was not as good but it was still possible to visualize all the major anatomical structures. Spin-echo images lead to reconstructions more detailed than those obtained from gradient-echo images. However, gradient-echo images are easier to segment due to their greater contrast. Furthermore, because images were acquired at least at ten points in the cardiac cycles for every slice it was possible to reconstruct a cine loop and, for example, to visualize the evolution of the size and margins of the ASD during the cardiac cycle. 3D reconstruction proved to be an effective way to assess the relationship between the different parts of the cardiac anatomy. The technique was useful in planning interventions in these patients.

Cavernous malformations of the brainstem: three-dimensional-constructive interference in steady-state magnetic resonance imaging for improvement of surgical approach and clinical results.

PubMed

Zausinger, Stefan; Yousry, Indra; Brueckmann, Hartmut; Schmid-Elsaesser, Robert; Tonn, Joerg-Christian

2006-02-01

The indications for resection of cavernous malformations (CMs) of the brainstem include neurological deficits, (recurrent) hemorrhage, and surgically accessible location. In particular, knowledge of the thickness of the parenchymal layer and of the CM's spatial relation to nuclei, tracts, cranial nerves, and vessels is critical for planning the surgical approach. We reviewed the operative treatment of 13 patients with 14 brainstem CMs, with special regard to refined three-dimensional (3D)-constructive interference in steady-state (CISS) magnetic resonance imaging (MRI). Patients were evaluated neurologically and by conventional spin-echo/fast spin-echo and 3D-CISS MRI. Surgery was performed with the use of microsurgical techniques and neurophysiological monitoring. Eleven CMs were located in the pons/pontomedullary region; 10 of the 11 were operated on via the lateral suboccipital approach. Three CMs were located near the floor of the fourth ventricle and operated on via the median suboccipital approach, with total removal of all CMs. Results were excellent or good in 10 patients; one patient transiently required tracheostomy, and two patients developed new hemipareses/ataxia with subsequent improvement. Not only did 3D-CISS sequences allow improved judgment of the thickness of the parenchymal layer over the lesion compared with spin-echo/fast spin-echo MRI, but 3D-CISS imaging also proved particularly superior in demonstrating the spatial relation of the lesion to fairly "safe" entry zones (e.g., between the trigeminal nerve and the VIIth and VIIIth nerve groups) by displaying the cranial nerves and vessels within the cerebellopontine cistern more precisely. Surgical treatment of brainstem CMs is recommended in symptomatic patients. Especially in patients with lesions situated ventrolaterally, the 3D-CISS sequence seems to be a valuable method for identifying the CM's relation to safe entry zones, thereby facilitating the surgical approach.

Fourier Analysis and Structure Determination. Part II: Pulse NMR and NMR Imaging.

ERIC Educational Resources Information Center

Chesick, John P.

1989-01-01

Uses simple pulse NMR experiments to discuss Fourier transforms. Studies the generation of spin echoes used in the imaging procedure. Shows that pulse NMR experiments give signals that are additions of sinusoids of differing amplitudes, frequencies, and phases. (MVL)

A brain stress test: Cerebral perfusion during memory encoding in mild cognitive impairment.

PubMed

Xie, Long; Dolui, Sudipto; Das, Sandhitsu R; Stockbower, Grace E; Daffner, Molly; Rao, Hengyi; Yushkevich, Paul A; Detre, John A; Wolk, David A

2016-01-01

Arterial spin labeled perfusion magnetic resonance imaging (ASL MRI) provides non-invasive quantification of cerebral blood flow, which can be used as a biomarker of brain function due to the tight coupling between cerebral blood flow (CBF) and brain metabolism. A growing body of literature suggests that regional CBF is altered in neurodegenerative diseases. Here we examined ASL MRI CBF in subjects with amnestic mild cognitive impairment (n = 65) and cognitively normal healthy controls (n = 62), both at rest and during performance of a memory-encoding task. As compared to rest, task-enhanced ASL MRI improved group discrimination, which supports the notion that physiologic measures during a cognitive challenge, or "stress test", may increase the ability to detect subtle functional changes in early disease stages. Further, logistic regression analysis demonstrated that ASL MRI and concomitantly acquired structural MRI provide complementary information of disease status. The current findings support the potential utility of task-enhanced ASL MRI as a biomarker in early Alzheimer's disease.

Low cerebral blood flow is associated with lower memory function in metabolic syndrome.

PubMed

Birdsill, Alex C; Carlsson, Cynthia M; Willette, Auriel A; Okonkwo, Ozioma C; Johnson, Sterling C; Xu, Guofan; Oh, Jennifer M; Gallagher, Catherine L; Koscik, Rebecca L; Jonaitis, Erin M; Hermann, Bruce P; LaRue, Asenath; Rowley, Howard A; Asthana, Sanjay; Sager, Mark A; Bendlin, Barbara B

2013-07-01

Metabolic syndrome (MetS)--a cluster of cardiovascular risk factors--is linked with cognitive decline and dementia. However, the brain changes underlying this link are presently unknown. In this study, we tested the relationship between MetS, cerebral blood flow (CBF), white matter hyperintensity burden, and gray matter (GM) volume in cognitively healthy late middle-aged adults. Additionally, the extent to which MetS was associated with cognitive performance was assessed. Late middle-aged adults from the Wisconsin Registry for Alzheimer's Prevention (N = 69, mean age = 60.4 years) underwent a fasting blood draw, arterial spin labeling perfusion MRI, T1-weighted MRI, T2FLAIR MRI, and neuropsychological testing. MetS was defined as abnormalities on three or more factors, including abdominal obesity, triglycerides, HDL-cholesterol, blood pressure, and fasting glucose. Mean GM CBF was 15% lower in MetS compared to controls. Voxel-wise image analysis indicated that the MetS group had lower CBF across a large portion of the cortical surface, with the exception of medial and inferior parts of the occipital and temporal lobes. The MetS group also had lower immediate memory function; a mediation analysis indicated this relationship was partially mediated by CBF. Among the MetS factors, abdominal obesity and elevated triglycerides were most strongly associated with lower CBF. The results underscore the importance of reducing the number of cardiovascular risk factors for maintaining CBF and cognition in an aging population. Copyright © 2012 The Obesity Society.

Absolute cerebral blood flow quantification with pulsed arterial spin labeling during hyperoxia corrected with the simultaneous measurement of the longitudinal relaxation time of arterial blood.

PubMed

Pilkinton, David T; Hiraki, Teruyuki; Detre, John A; Greenberg, Joel H; Reddy, Ravinder

2012-06-01

Quantitative arterial spin labeling (ASL) estimates of cerebral blood flow (CBF) during oxygen inhalation are important in several contexts, including functional experiments calibrated with hyperoxia and studies investigating the effect of hyperoxia on regional CBF. However, ASL measurements of CBF during hyperoxia are confounded by the reduction in the longitudinal relaxation time of arterial blood (T(1a) ) from paramagnetic molecular oxygen dissolved in blood plasma. The aim of this study is to accurately quantify the effect of arbitrary levels of hyperoxia on T(1a) and correct ASL measurements of CBF during hyperoxia on a per-subject basis. To mitigate artifacts, including the inflow of fresh spins, partial voluming, pulsatility, and motion, a pulsed ASL approach was implemented for in vivo measurements of T(1a) in the rat brain at 3 Tesla. After accounting for the effect of deoxyhemoglobin dilution, the relaxivity of oxygen on blood was found to closely match phantom measurements. The results of this study suggest that the measured ASL signal changes are dominated by reductions in T(1a) for brief hyperoxic inhalation epochs, while the physiologic effects of oxygen on the vasculature account for most of the measured reduction in CBF for longer hyperoxic exposures. Copyright © 2011 Wiley-Liss, Inc.

Accelerated Radiation-Damping for Increased Spin Equilibrium (ARISE)

PubMed Central

Huang, Susie Y.; Witzel, Thomas; Wald, Lawrence L.

2008-01-01

Control of the longitudinal magnetization in fast gradient echo sequences is an important factor enabling the high efficiency of balanced Steady State Free Precession (bSSFP) sequences. We introduce a new method for accelerating the return of the longitudinal magnetization to the +z-axis that is independent of externally applied RF pulses and shows improved off-resonance performance. The Accelerated Radiation damping for Increased Spin Equilibrium (ARISE) method uses an external feedback circuit to strengthen the Radiation Damping (RD) field. The enhanced RD field rotates the magnetization back to the +z-axis at a rate faster than T1 relaxation. The method is characterized in gradient echo phantom imaging at 3T as a function of feedback gain, phase, and duration and compared with results from numerical simulations of the Bloch equations incorporating RD. A short period of feedback (10ms) during a refocused interval of a crushed gradient echo sequence allowed greater than 99% recovery of the longitudinal magnetization when very little T2 relaxation has time to occur. Appropriate applications might include improving navigated sequences. Unlike conventional flip-back schemes, the ARISE “flip-back” is generated by the spins themselves, thereby offering a potentially useful building block for enhancing gradient echo sequences. PMID:18956463

3D isotropic T2-weighted fast spin echo (VISTA) versus 2D T2-weighted fast spin echo in evaluation of the calcaneofibular ligament in the oblique coronal plane.

PubMed

Park, H J; Lee, S Y; Choi, Y J; Hong, H P; Park, S J; Park, J H; Kim, E

2017-02-01

To investigate whether the image quality of three-dimensional (3D) volume isotropic fast spin echo acquisition (VISTA) magnetic resonance imaging (MRI) of the calcaneofibular ligament (CFL) view is comparable to that of 2D fast spin echo T2-weighted images (2D T2 FSE) for the evaluation of the CFL, and whether 3D VISTA can replace 2D T2 FSE for the evaluation of CFL injuries. This retrospective study included 76 patients who underwent ankle MRI with CFL views of both 2D T2 FSE MRI and 3D VISTA. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of both techniques were measured. The anatomical identification score and diagnostic performances were evaluated by two readers independently. The diagnostic performances of 3D VISTA and 2D T2 FSE were analysed by sensitivity, specificity, and accuracy for diagnosing CFL injury with reference standards of surgically or clinically confirmed diagnoses. Surgical correlation was performed in 29% of the patients, and clinical examination was used in those who did not have surgery (71%). The SNRs and CNRs of 3D VISTA were significantly higher than those of 2D T2 FSE. The anatomical identification scores on 3D VISTA were inferior to those on 2D T2 FSE, and the differences were statistically significant (p<0.05). There were no significant differences in diagnostic performance between the two sequences when diagnoses were classified as normal or abnormal. Although the image quality of 3D VISTA MRI of the CFL view is not equal to that of 2D T2 FSE for the anatomical evaluation of CFL, 3D VISTA has a diagnostic performance comparable to that of 2D T2 FSE for the diagnosis of CFL injuries. Copyright © 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

MR imaging of ore for heap bioleaching studies using pure phase encode acquisition methods

NASA Astrophysics Data System (ADS)

Fagan, Marijke A.; Sederman, Andrew J.; Johns, Michael L.

2012-03-01

Various MRI techniques were considered with respect to imaging of aqueous flow fields in low grade copper ore. Spin echo frequency encoded techniques were shown to produce unacceptable image distortions which led to pure phase encoded techniques being considered. Single point imaging multiple point acquisition (SPI-MPA) and spin echo single point imaging (SESPI) techniques were applied. By direct comparison with X-ray tomographic images, both techniques were found to be able to produce distortion-free images of the ore packings at 2 T. The signal to noise ratios (SNRs) of the SESPI images were found to be superior to SPI-MPA for equal total acquisition times; this was explained based on NMR relaxation measurements. SESPI was also found to produce suitable images for a range of particles sizes, whereas SPI-MPA SNR deteriorated markedly as particles size was reduced. Comparisons on a 4.7 T magnet showed significant signal loss from the SPI-MPA images, the effect of which was accentuated in the case of unsaturated flowing systems. Hence it was concluded that SESPI was the most robust imaging method for the study of copper ore heap leaching hydrology.

Comparison of Diffusion-Weighted Imaging in the Human Brain Using Readout-Segmented EPI and PROPELLER Turbo Spin Echo With Single-Shot EPI at 7 T MRI.

PubMed

Kida, Ikuhiro; Ueguchi, Takashi; Matsuoka, Yuichiro; Zhou, Kun; Stemmer, Alto; Porter, David

2016-07-01

The purpose of the present study was to compare periodically rotated overlapping parallel lines with enhanced reconstruction-type turbo spin echo diffusion-weighted imaging (pTSE-DWI) and readout-segmented echo planar imaging (rsEPI-DWI) with single-shot echo planar imaging (ssEPI-DWI) in a 7 T human MR system. We evaluated the signal-to-noise ratio (SNR), image distortion, and apparent diffusion coefficient values in the human brain. Six healthy volunteers were included in this study. The study protocol was approved by our institutional review board. All measurements were performed at 7 T using pTSE-DWI, rsEPI-DWI, and ssEPI-DWI sequences. The spatial resolution was 1.2 × 1.2 mm in-plane with a 3-mm slice thickness. Signal-to-noise ratio was measured using 2 scans. The ssEPI-DWI sequence showed significant image blurring, whereas pTSE-DWI and rsEPI-DWI sequences demonstrated high image quality with low geometrical distortion compared with reference T2-weighted, turbo spin echo images. Signal loss in ventral regions near the air-filled paranasal sinus/nasal cavity was found in ssEPI-DWI and rsEPI-DWI but not pTSE-DWI. The apparent diffusion coefficient values for ssEPI-DWI were 824 ± 17 × 10 and 749 ± 25 × 10 mm/s in the gray matter and white matter, respectively; the values obtained for pTSE-DWI were 798 ± 21 × 10 and 865 ± 40 × 10 mm/s; and the values obtained for rsEPI-DWI were 730 ± 12 × 10 and 722 ± 25 × 10 mm/s. The pTSE-DWI images showed no additional distortion comparison to the T2-weighted images, but had a lower SNR than ssEPI-DWI and rsEPI-DWI. The rsEPI-DWI sequence provided high-quality images with minor distortion and a similar SNR to ssEPI-DWI. Our results suggest that the benefits of the rsEPI-DWI and pTSE-DWI sequences, in terms of SNR, image quality, and image distortion, appear to outweigh those of ssEPI-DWI. Thus, pTSE-DWI and rsEPI-DWI at 7 T have great potential use for clinical diagnoses. However, it is noteworthy that both sequences are limited by the scan time required. In addition, pTSE-DWI has limitations on the number of slices due to specific absorption rate. Overall, rsEPI-DWI is a favorable imaging sequence, taking into account the SNR and image quality at 7 T.

Theory and optical design of x-ray echo spectrometers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shvyd'ko, Yuri

X-ray echo spectroscopy, a space-domain counterpart of neutron spin echo, is a recently proposed inelastic x-ray scattering (IXS) technique. X-ray echo spectroscopy relies on imaging IXS spectra and does not require x-ray monochromatization. Due to this, the echo-type IXS spectrometers are broadband, and thus have a potential to simultaneously provide dramatically increased signal strength, reduced measurement times, and higher resolution compared to the traditional narrow-band scanning-type IXS spectrometers. The theory of x-ray echo spectrometers presented earlier [Yu. Shvyd'ko, Phys. Rev. Lett. 116, 080801 (2016)] is developed here further with a focus on questions of practical importance, which could facilitate opticalmore » design and assessment of the feasibility and performance of the echo spectrometers. Among others, the following questions are addressed: spectral resolution, refocusing condition, echo spectrometer tolerances, refocusing condition adjustment, effective beam size on the sample, spectral window of imaging and scanning range, impact of the secondary source size on the spectral resolution, angular dispersive optics, focusing and collimating optics, and detector's spatial resolution. In conclusion, examples of optical designs and characteristics of echo spectrometers with 1-meV and 0.1-meV resolutions are presented.« less

Theory and optical design of x-ray echo spectrometers

DOE PAGES

Shvyd'ko, Yuri

2017-08-02

X-ray echo spectroscopy, a space-domain counterpart of neutron spin echo, is a recently proposed inelastic x-ray scattering (IXS) technique. X-ray echo spectroscopy relies on imaging IXS spectra and does not require x-ray monochromatization. Due to this, the echo-type IXS spectrometers are broadband, and thus have a potential to simultaneously provide dramatically increased signal strength, reduced measurement times, and higher resolution compared to the traditional narrow-band scanning-type IXS spectrometers. The theory of x-ray echo spectrometers presented earlier [Yu. Shvyd'ko, Phys. Rev. Lett. 116, 080801 (2016)] is developed here further with a focus on questions of practical importance, which could facilitate opticalmore » design and assessment of the feasibility and performance of the echo spectrometers. Among others, the following questions are addressed: spectral resolution, refocusing condition, echo spectrometer tolerances, refocusing condition adjustment, effective beam size on the sample, spectral window of imaging and scanning range, impact of the secondary source size on the spectral resolution, angular dispersive optics, focusing and collimating optics, and detector's spatial resolution. In conclusion, examples of optical designs and characteristics of echo spectrometers with 1-meV and 0.1-meV resolutions are presented.« less

Effects of finite spatial resolution on quantitative CBF images from dynamic PET

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phelps, M.E.; Huang, S.C.; Mahoney, D.K.

1985-05-01

The finite spatial resolution of PET causes the time-activity responses on pixels around the boundaries between gray and white matter regions to contain kinetic components from tissues of different CBF's. CBF values estimated from kinetics of such mixtures are underestimated because of the nonlinear relationship between the time-activity response and the estimated CBF. Computer simulation is used to investigate these effects on phantoms of circular structures and realistic brain slice in terms of object size and quantitative CBF values. The CBF image calculated is compared to the case of having resolution loss alone. Results show that the size of amore » high flow region in the CBF image is decreased while that of a low flow region is increased. For brain phantoms, the qualitative appearance of CBF images is not seriously affected, but the estimated CBF's are underestimated by 11 to 16 percent in local gray matter regions (of size 1 cm/sup 2/) with about 14 percent reduction in global CBF over the whole slice. It is concluded that the combined effect of finite spatial resolution and the nonlinearity in estimating CBF from dynamic PET is quite significant and must be considered in processing and interpreting quantitative CBF images.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brasch, R.C.; Wesbey, G.E.; Gooding, C.A.

Tissue deposits of hemosiderin, a paramagnetic iron-protein complex, resulted in marked abnormalities of magnetic resonance (MR) spin-echo signal intensity within the viscera of three children with transfusional hemosiderosis and thalassemia major. In all patients the liver and bone marrow demonstrated abnormally low spin-echo intensities and the kidneys and muscles had abnormally high intensities. These observations correlate with in vitro MR observation of ferric (Fe/sup +3/) solutions, in which concentrations of ferric salts greater than 20 mmol yielded higher intensities than did water alone. MR imaging is sensitive to the tissue deposition of hemosiderin, and MR intensity appears to provide amore » rough measure of the amount of iron deposited.« less

Polynitroxyl albumin and albumin therapy after pediatric asphyxial cardiac arrest: effects on cerebral blood flow and neurologic outcome

PubMed Central

Manole, Mioara D; Kochanek, Patrick M; Foley, Lesley M; Hitchens, T Kevin; Bayır, Hülya; Alexander, Henry; Garman, Robert; Ma, Li; Hsia, Carleton J C; Ho, Chien; Clark, Robert S B

2012-01-01

Postresuscitation cerebral blood flow (CBF) disturbances and generation of reactive oxygen species likely contribute to impaired neurologic outcome after pediatric cardiac arrest (CA). Hence, we determined the effects of the antioxidant colloid polynitroxyl albumin (PNA) versus albumin or normal saline (NS) on CBF and neurologic outcome after asphyxial CA in immature rats. We induced asphyxia for 9 minutes in male and female postnatal day 16 to 18 rats randomized to receive PNA, albumin, or NS at resuscitation from CA or sham surgery. Regional CBF was measured serially from 5 to 150 minutes after resuscitation by arterial spin-labeled magnetic resonance imaging. We assessed motor function (beam balance and inclined plane), spatial memory retention (water maze), and hippocampal neuronal survival. Polynitroxyl albumin reduced early hyperemia seen 5 minutes after CA. In contrast, albumin markedly increased and prolonged hyperemia. In the delayed period after resuscitation (90 to 150 minutes), CBF was comparable among groups. Both PNA- and albumin-treated rats performed better in the water maze versus NS after CA. This benefit was observed only in males. Hippocampal neuron survival was similar between injury groups. Treatment of immature rats with PNA or albumin resulted in divergent acute changes in CBF, but both improved spatial memory retention in males after asphyxial CA. PMID:22126915

X-ray echo spectroscopy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Shvyd'ko, Yuri V.

2016-09-01

X-ray echo spectroscopy, a counterpart of neutron spin-echo, was recently introduced [1] to overcome limitations in spectral resolution and weak signals of the traditional inelastic x-ray scattering (IXS) probes. An image of a point-like x-ray source is defocused by a dispersing system comprised of asymmetrically cut specially arranged Bragg diffracting crystals. The defocused image is refocused into a point (echo) in a time-reversal dispersing system. If the defocused beam is inelastically scattered from a sample, the echo signal acquires a spatial distribution, which is a map of the inelastic scattering spectrum. The spectral resolution of the echo spectroscopy does not rely on the monochromaticity of the x-rays, ensuring strong signals along with a very high spectral resolution. Particular schemes of x-ray echo spectrometers for 0.1-meV and 0.02-meV ultra-high-resolution IXS applications (resolving power > 10^8) with broadband 5-13 meV dispersing systems will be presented featuring more than 1000-fold signal enhancement. The technique is general, applicable in different photon frequency domains. [1.] Yu. Shvyd'ko, Phys. Rev. Lett. 116, accepted (2016), arXiv:1511.01526.

Arterial spin labelling shows functional depression of non-lesion tissue in chronic Wernicke's aphasia.

PubMed

Robson, Holly; Specht, Karsten; Beaumont, Helen; Parkes, Laura M; Sage, Karen; Lambon Ralph, Matthew A; Zahn, Roland

2017-07-01

Behavioural impairment post-stroke is a consequence of structural damage and altered functional network dynamics. Hypoperfusion of intact neural tissue is frequently observed in acute stroke, indicating reduced functional capacity of regions outside the lesion. However, cerebral blood flow (CBF) is rarely investigated in chronic stroke. This study investigated CBF in individuals with chronic Wernicke's aphasia (WA) and examined the relationship between lesion, CBF and neuropsychological impairment. Arterial spin labelling CBF imaging and structural MRIs were collected in 12 individuals with chronic WA and 13 age-matched control participants. Joint independent component analysis (jICA) investigated the relationship between structural lesion and hypoperfusion. Partial correlations explored the relationship between lesion, hypoperfusion and language measures. Joint ICA revealed significant differences between the control and WA groups reflecting a large area of structural lesion in the left posterior hemisphere and an associated area of hypoperfusion extending into grey matter surrounding the lesion. Small regions of remote cortical hypoperfusion were observed, ipsilateral and contralateral to the lesion. Significant correlations were observed between the neuropsychological measures (naming, repetition, reading and semantic association) and the jICA component of interest in the WA group. Additional ROI analyses found a relationship between perfusion surrounding the core lesion and the same neuropsychological measures. This study found that core language impairments in chronic WA are associated with a combination of structural lesion and abnormal perfusion in non-lesioned tissue. This indicates that post-stroke impairments are due to a wider disruption of neural function than observable on structural T1w MRI. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Targeted Single-Shot Methods for Diffusion-Weighted Imaging in the Kidneys

PubMed Central

Jin, Ning; Deng, Jie; Zhang, Longjiang; Zhang, Zhuoli; Lu, Guangming; Omary, Reed A.; Larson, Andrew C.

2011-01-01

Purpose To investigate the feasibility of combining the inner-volume-imaging (IVI) technique with single-shot diffusion-weighted (DW) spin-echo echo-planar imaging (SE-EPI) and DW-SPLICE (split acquisition of fast spin-echo) sequences for renal DW imaging. Materials and Methods Renal DW imaging was performed in 10 healthy volunteers using single-shot DW-SE-EPI, DW-SPLICE, targeted-DW-SE-EPI and targeted-DW-SPLICE. We compared the quantitative diffusion measurement accuracy and image quality of these targeted-DW-SE-EPI and targeted DW-SPLICE methods with conventional full FOV DW-SE-EPI and DW-SPLICE measurements in phantoms and normal volunteers. Results Compared with full FOV DW-SE-EPI and DW-SPLICE methods, targeted-DW-SE-EPI and targeted-DW-SPLICE approaches produced images of superior overall quality with fewer artifacts, less distortion and reduced spatial blurring in both phantom and volunteer studies. The ADC values measured with each of the four methods were similar and in agreement with previously published data. There were no statistically significant differences between the ADC values and intra-voxel incoherent motion (IVIM) measurements in the kidney cortex and medulla using single-shot DW-SE-EPI, targeted-DW-EPI and targeted-DW-SPLICE (p > 0.05). Conclusion Compared with full-FOV DW imaging methods, targeted-DW-SE-EPI and targeted-DW-SPLICE techniques reduced image distortion and artifacts observed in the single-shot DW-SE-EPI images, reduced blurring in DW-SPLICE images and produced comparable quantitative DW and IVIM measurements to those produced with conventional full-FOV approaches. PMID:21591023

Strong-coupling induced damping of spin-echo modulations in magic-angle-spinning NMR: Implications for J coupling measurements in disordered solids

NASA Astrophysics Data System (ADS)

Guerry, Paul; Brown, Steven P.; Smith, Mark E.

2017-10-01

In the context of improving J coupling measurements in disordered solids, strong coupling effects have been investigated in the spin-echo and refocused INADEQUATE spin-echo (REINE) modulations of three- and four-spin systems under magic-angle-spinning (MAS), using density matrix simulations and solid-state NMR experiments on a cadmium phosphate glass. Analytical models are developed for the different modulation regimes, which are shown to be distinguishable in practice using Akaike's information criterion. REINE modulations are shown to be free of the damping that occurs for spin-echo modulations when the observed spin has the same isotropic chemical shift as its neighbour. Damping also occurs when the observed spin is bonded to a strongly-coupled pair. For mid-chain units, the presence of both direct and relayed damping makes both REINE and spin-echo modulations impossible to interpret quantitatively. We nonetheless outline how a qualitative comparison of the modulation curves can provide valuable information on disordered networks, possibly also pertaining to dynamic effects therein.

MR imaging of the inner ear: comparison of a three-dimensional fast spin-echo sequence with use of a dedicated quadrature-surface coil with a gadolinium-enhanced spoiled gradient-recalled sequence.

PubMed

Naganawa, S; Ito, T; Fukatsu, H; Ishigaki, T; Nakashima, T; Ichinose, N; Kassai, Y; Miyazaki, M

1998-09-01

To prospectively evaluate the sensitivity and specificity of magnetic resonance (MR) imaging in the inner ear with a long echo train, three-dimensional (3D), asymmetric Fourier-transform, fast spin-echo (SE) sequence with use of a dedicated quadrature-surface phased-array coil to detect vestibular schwannoma in the cerebellopontine angle and the internal auditory canal. In 205 patients (410 ears) with ear symptoms, 1.5-T MR imaging was performed with unenhanced 3D asymmetric fast SE and gadolinium-enhanced 3D gradient-recalled (SPGR) sequences with use of a quadrature surface phased-array coil. The 3D asymmetric fast SE images were reviewed by two radiologists, with the gadolinium-enhanced 3D SPGR images used as the standard of reference. Nineteen lesions were detected in the 410 ears (diameter range, 2-30 mm; mean, 10.5 mm +/- 6.4 [standard deviation]; five lesions were smaller than 5 mm). With 3D asymmetric fast SE, sensitivity, specificity, and accuracy, respectively, were 100%, 99.5%, and 99.5% for observer 1 and 100%, 99.7%, and 99.8% for observer 2. The unenhanced 3D asymmetric fast SE sequence with a quadrature-surface phased-array coli allows the reliable detection of vestibular schwannoma in the cerebellopontine angle and internal auditory canal.

Evaluation of pleural and pericardial effusions by magnetic resonance imaging.

PubMed

Tscholakoff, D; Sechtem, U; de Geer, G; Schmidt, H; Higgins, C B

1987-08-01

MR examinations of 36 patients with pleural and/or pericardial effusions were retrospectively evaluated. The purpose of this study was to determine of MR imaging is capable of differentiating between pleural and pericardial effusions of different compositions using standard electrocardiogram (ECG)-gated and non-gated spin echo pulse sequences. Additional data was obtained from experimental pleural effusions in 10 dogs. The results of this study indicate that old hemorrhages into the pleural or pericardial space can be differentiated from other pleural or pericardial effusions. However, further differentiation between transudates, exudates and sanguinous effusions is not possible on MR images acquired with standard spin echo pulse sequences. Respiratory and cardiac motion are responsible for signal loss, particularly on first echo images. This was documented in experiments in dogs with induced effusions of known composition; "negative" T2 values consistent with fluid motion during imaging sequences were observed in 80% of cases. However, postmortem studies of the dogs with experimental effusions showed differences between effusions with low protein concentrations and higher protein concentrations. We conclude from our study that characterization of pleural and pericardial effusions on standard ECG-gated and non-gated MR examinations is limited to the positive identification of hemorrhage. Motion of the fluid due to cardiac and respiratory activity causes artifactual and unpredictable changes in intensity values negating the more subtle differences in intensity associated with increasing protein content.

B0 concomitant field compensation for MRI systems employing asymmetric transverse gradient coils.

PubMed

Weavers, Paul T; Tao, Shengzhen; Trzasko, Joshua D; Frigo, Louis M; Shu, Yunhong; Frick, Matthew A; Lee, Seung-Kyun; Foo, Thomas K-F; Bernstein, Matt A

2018-03-01

Imaging gradients result in the generation of concomitant fields, or Maxwell fields, which are of increasing importance at higher gradient amplitudes. These time-varying fields cause additional phase accumulation, which must be compensated for to avoid image artifacts. In the case of gradient systems employing symmetric design, the concomitant fields are well described with second-order spatial variation. Gradient systems employing asymmetric design additionally generate concomitant fields with global (zeroth-order or B 0 ) and linear (first-order) spatial dependence. This work demonstrates a general solution to eliminate the zeroth-order concomitant field by applying the correct B 0 frequency shift in real time to counteract the concomitant fields. Results are demonstrated for phase contrast, spiral, echo-planar imaging (EPI), and fast spin-echo imaging. A global phase offset is reduced in the phase-contrast exam, and blurring is virtually eliminated in spiral images. The bulk image shift in the phase-encode direction is compensated for in EPI, whereas signal loss, ghosting, and blurring are corrected in the fast-spin echo images. A user-transparent method to compensate the zeroth-order concomitant field term by center frequency shifting is proposed and implemented. This solution allows all the existing pulse sequences-both product and research-to be retained without any modifications. Magn Reson Med 79:1538-1544, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Carr-Purcell-Meiboom-Gill (CPMG) Imaging of Prostate Cancer: Quantitative T2 Values for Cancer Discrimination

PubMed Central

Roebuck, Joseph R.; Haker, Steven J.; Mitsouras, Dimitris; Rybicki, Frank J.; Tempany, Clare M.; Mulkern, Robert V.

2009-01-01

Quantitative, apparent T2 values of suspected prostate cancer and healthy peripheral zone tissue in men with prostate cancer were measured using a Carr-Purcell-Meiboom-Gill (CPMG) imaging sequence in order to assess the cancer discrimination potential of tissue T2 values. The CPMG imaging sequence was used to image the prostates of 18 men with biopsy proven prostate cancer. Whole gland coverage with nominal voxel volumes of 0.54 × 1.1 × 4 mm3 was obtained in 10.7 minutes, resulting in data sets suitable for generating high quality images with variable T2-weighting and for evaluating quantitative T2 values on a pixel-by-pixel basis. Region-of-interest analysis of suspected healthy peripheral zone tissue and suspected cancer, identified on the basis of both T1- and T2-weighted signal intensities and available histopathology reports, yielded significantly (p < 0.0001) longer apparent T2 values in suspected healthy tissue (193 ± 49 ms) vs. suspected cancer (100 ± 26 ms), suggesting potential utility of this method as a tissue specific discrimination index for prostate cancer. We conclude that CPMG imaging of the prostate can be performed in reasonable scan times and can provide advantages over T2-weighted fast spin echo imaging alone, including quantitative T2 values for cancer discrimination as well as proton density maps without the point spread function degradation associated with short effective echo time fast spin echo (FSE) sequences. PMID:18823731

Assessment of cerebral blood flow with magnetic resonance imaging in children with sickle cell disease: A quantitative comparison with transcranial Doppler ultrasonography.

PubMed

Croal, Paula L; Leung, Jackie; Kosinski, Przemyslaw; Shroff, Manohar; Odame, Isaac; Kassner, Andrea

2017-11-01

Transcranial Doppler ultrasonography (TCD) is a clinical tool for stratifying ischemic stroke risk by identifying abnormal elevations in blood flow velocity (BFV) in the middle cerebral artery (MCA). However, TCD is not effective at screening for subtle neurologic injury such as silent cerebral infarcts. To better understand this disparity, we compared TCD measures of BFV with tissue-level cerebral blood flow (CBF) using arterial spin-labeling MRI in children with and without sickle cell disease, and correlated these measurements against clinical hematologic measures of disease severity. TCD and MRI assessment were performed in 13 pediatric sickle cell disease patients and eight age-matched controls. Using MRI measures of MCA diameter and territory weight, TCD measures of BFV in the MCA [cm/s] were converted into units of CBF [ml min -1 100 g -1 ] for comparison. There was no significant association between TCD measures of BFV in the MCA and corresponding MRI measures of CBF in patients ( r  =   .28, p  =   .39) or controls ( r  =   .10, p  =   .81). After conversion from BFV into units of CBF, a strong association was observed between TCD and MRI measures ( r  =   .67, p  =   .017 in patients, r  =   .86, p  =   .006 in controls). While BFV in the MCA showed a lack of correlation with arterial oxygen content, an inverse association was observed for CBF measurements. This study demonstrates that BFV in the MCA cannot be used as a surrogate marker for tissue-level CBF in children with sickle cell disease. Therefore, TCD alone may not be sufficient for understanding and predicting subtle pathophysiology in this population, highlighting the potential clinical value of tissue-level CBF.

Chronic kidney disease, cerebral blood flow, and white matter volume in hypertensive adults.

PubMed

Tamura, Manjula Kurella; Pajewski, Nicholas M; Bryan, R Nick; Weiner, Daniel E; Diamond, Matthew; Van Buren, Peter; Taylor, Addison; Beddhu, Srinivasan; Rosendorff, Clive; Jahanian, Hesamoddin; Zaharchuk, Greg

2016-03-29

To determine the relation between markers of kidney disease-estimated glomerular filtration rate (eGFR) and urine albumin to creatinine ratio (UACR)-with cerebral blood flow (CBF) and white matter volume (WMV) in hypertensive adults. We used baseline data collected from 665 nondiabetic hypertensive adults aged ≥50 years participating in the Systolic Blood Pressure Intervention Trial (SPRINT). We used arterial spin labeling to measure CBF and structural 3T images to segment tissue into normal and abnormal WMV. We used quantile regression to estimate the association between eGFR and UACR with CBF and abnormal WMV, adjusting for sociodemographic and clinical characteristics. There were 218 participants (33%) with eGFR <60 mL/min/1.73 m(2) and 146 participants (22%) with UACR ≥30 mg/g. Reduced eGFR was independently associated with higher adjusted median CBF, but not with abnormal WMV. Conversely, in adjusted analyses, there was a linear independent association between UACR and larger abnormal WMV, but not with CBF. Compared to participants with neither marker of CKD (eGFR ≥60 mL/min/1.73 m(2) and UACR <30 mg/g), median CBF was 5.03 mL/100 g/min higher (95% confidence interval [CI] 0.78, 9.29) and abnormal WMV was 0.63 cm(3) larger (95% CI 0.08, 1.17) among participants with both markers of CKD (eGFR <60 mL/min/1.73 m(2) and UACR ≥30 mg/g). Among nondiabetic hypertensive adults, reduced eGFR was associated with higher CBF and higher UACR was associated with larger abnormal WMV. © 2016 American Academy of Neurology.

Aortic valve bypass surgery in severe aortic valve stenosis: Insights from cardiac and brain magnetic resonance imaging.

PubMed

Mantini, Cesare; Caulo, Massimo; Marinelli, Daniele; Chiacchiaretta, Piero; Tartaro, Armando; Cotroneo, Antonio Raffaele; Di Giammarco, Gabriele

2018-04-13

To investigate and describe the distribution of aortic and cerebral blood flow (CBF) in patients with severe valvular aortic stenosis (AS) before and after aortic valve bypass (AVB) surgery. We enrolled 10 consecutive patients who underwent AVB surgery for severe AS. Cardiovascular magnetic resonance imaging (CMR) and brain magnetic resonance imaging were performed as baseline before surgery and twice after surgery. Quantitative flow measurements were obtained using 1.5-T magnetic resonance imaging (MRI) scanner phase-contrast images of the ascending aorta, descending thoracic aorta (3 cm proximally and distally from the conduit-to-aorta anastomosis), and ventricular outflow portion of the conduit. The evaluation of CBF was performed using 3.0-T MRI scanner arterial spin labeling (ASL) through sequences acquired at the gray matter, dorsal default-mode network, and sensorimotor levels. Conduit flow, expressed as the percentage of total antegrade flow through the conduit, was 63.5 ± 8% and 67.8 ± 7% on early and mid-term postoperative CMR, respectively (P < .05). Retrograde perfusion from the level of the conduit insertion in the descending thoracic aorta toward the aortic arch accounted for 6.9% of total cardiac output and 11% of total conduit flow. We did not observe any significant reduction in left ventricular stroke volume at postoperative evaluation compared with preoperative evaluation (P = .435). No differences were observed between preoperative and postoperative CBF at the gray matter, dorsal default-mode network, and sensorimotor levels (P = .394). After AVB surgery in patients with severe AS, cardiac output is split between the native left ventricular outflow tract and the apico-aortic bypass, with two-thirds of the total antegrade flow passing through the latter and one-third passing through the former. In our experience, CBF assessment confirms that the flow redistribution does not jeopardize cerebral blood supply. Copyright © 2018 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

X-PROP: a fast and robust diffusion-weighted propeller technique.

PubMed

Li, Zhiqiang; Pipe, James G; Lee, Chu-Yu; Debbins, Josef P; Karis, John P; Huo, Donglai

2011-08-01

Diffusion-weighted imaging (DWI) has shown great benefits in clinical MR exams. However, current DWI techniques have shortcomings of sensitivity to distortion or long scan times or combinations of the two. Diffusion-weighted echo-planar imaging (EPI) is fast but suffers from severe geometric distortion. Periodically rotated overlapping parallel lines with enhanced reconstruction diffusion-weighted imaging (PROPELLER DWI) is free of geometric distortion, but the scan time is usually long and imposes high Specific Absorption Rate (SAR) especially at high fields. TurboPROP was proposed to accelerate the scan by combining signal from gradient echoes, but the off-resonance artifacts from gradient echoes can still degrade the image quality. In this study, a new method called X-PROP is presented. Similar to TurboPROP, it uses gradient echoes to reduce the scan time. By separating the gradient and spin echoes into individual blades and removing the off-resonance phase, the off-resonance artifacts in X-PROP are minimized. Special reconstruction processes are applied on these blades to correct for the motion artifacts. In vivo results show its advantages over EPI, PROPELLER DWI, and TurboPROP techniques. Copyright © 2011 Wiley-Liss, Inc.

Arterial spin labeling reveals relationships between resting cerebral perfusion and motor learning in Parkinson's disease.

PubMed

Barzgari, Amy; Sojkova, Jitka; Maritza Dowling, N; Pozorski, Vincent; Okonkwo, Ozioma C; Starks, Erika J; Oh, Jennifer; Thiesen, Frances; Wey, Alexandra; Nicholas, Christopher R; Johnson, Sterling; Gallagher, Catherine L

2018-05-09

Parkinson's disease (PD) is an age-related neurodegenerative disease that produces changes in movement, cognition, sleep, and autonomic function. Motor learning involves acquisition of new motor skills through practice, and is affected by PD. The purpose of the present study was to evaluate regional differences in resting cerebral blood flow (rCBF), measured using arterial spin labeling (ASL) MRI, during a finger-typing task of motor skill acquisition in PD patients compared to age- and gender-matched controls. Voxel-wise multiple linear regression models were used to examine the relationship between rCBF and several task variables, including initial speed, proficiency gain, and accuracy. In these models, a task-by-disease group interaction term was included to investigate where the relationship between rCBF and task performance was influenced by PD. At baseline, perfusion was lower in PD subjects than controls in the right occipital cortex. The task-by-disease group interaction for initial speed was significantly related to rCBF (p < 0.05, corrected) in several brain regions involved in motor learning, including the occipital, parietal, and temporal cortices, cerebellum, anterior cingulate, and the superior and middle frontal gyri. In these regions, PD patients showed higher rCBF, and controls lower rCBF, with improved performance. Within the control group, proficiency gain over 12 typing trials was related to greater rCBF in cerebellar, occipital, and temporal cortices. These results suggest that higher rCBF within networks involved in motor learning enable PD patients to compensate for disease-related deficits.

Correction for Delay and Dispersion Results in More Accurate Cerebral Blood Flow Ischemic Core Measurement in Acute Stroke.

PubMed

Lin, Longting; Bivard, Andrew; Kleinig, Timothy; Spratt, Neil J; Levi, Christopher R; Yang, Qing; Parsons, Mark W

2018-04-01

This study aimed to assess how the ischemic core measured by perfusion computed tomography (CTP) was affected by the delay and dispersion effect. Ischemic stroke patients having CTP performed within 6 hours of onset were included. The CTP data were processed twice, generating standard cerebral blood flow (sCBF) and delay- and dispersion-corrected CBF (ddCBF), respectively. Ischemic core measured by the sCBF and ddCBF was then compared at the relative threshold <30% of normal tissue. Two references for ischemic core were used: acute diffusion-weighted imaging or 24-hour diffusion-weighted imaging in patients with complete recanalization. Difference of core volume between CTP and diffusion-weighted imaging was estimated by Mann-Whitney U test and limits of agreement. Patients were also classified into favorable and unfavorable CTP patterns. The imaging pattern classification by sCBF and ddCBF was compared by the χ 2 test; their respective ability to predict good clinical outcome (3-month modified Rankin Scale score) was tested in logistic regression. Fifty-five patients were included in this study. Median sCBF ischemic core volume was 38.5 mL (12.4-61.9 mL), much larger than the median core volume of 17.2 mL measured by ddCBF (interquartile range, 5.5-38.8; P <0.001). Moreover, compared with sCBF <30%, ddCBF <30% measured the ischemic core much closer to diffusion-weighted imaging core references, with the mean volume difference of -0.1 mL (95% limits of agreement, -25.4 to 25.2; P =0.97) and 16.7 mL (95% limits of agreement, -21.7 to 55.2; P <0.001), respectively. Imaging patterns defined by sCBF showed a difference to that defined by ddCBF ( P <0.001), with 12 patients classified as favorable imaging patterns by ddCBF but as unfavorable by sCBF. The favorable imaging pattern classified by ddCBF, compared with sCBF classification, had higher predictive power for good clinical outcome (odds ratio, 7.8 [2-30.5] and 3.1 [0.9-11], respectively). Delay and dispersion correction increases the accuracy of ischemic core measurement on CTP. © 2018 American Heart Association, Inc.

7 Tesla compatible in-bore display for functional magnetic resonance imaging.

PubMed

Groebner, Jens; Berger, Moritz Cornelius; Umathum, Reiner; Bock, Michael; Rauschenberg, Jaane

2013-08-01

A liquid crystal display was modified for use inside a 7 T MR magnet. SNR measurements were performed using different imaging sequences with the monitor absent, present, or activated. fMRI with a volunteer was conducted using a visual stimulus. SNR was reduced by 3.7%/7.9% in echo planar/fast-spin echo images when the monitor was on which can be explained by the limited shielding of the coated front window (40 dB). In the fMRI experiments, activated regions in the visual cortex were clearly visible. The monitor provided excellent resolution at minor SNR reduction in EPI images, and is thus suitable for fMRI at ultra-high field.

Artificial neural network prediction of ischemic tissue fate in acute stroke imaging

PubMed Central

Huang, Shiliang; Shen, Qiang; Duong, Timothy Q

2010-01-01

Multimodal magnetic resonance imaging of acute stroke provides predictive value that can be used to guide stroke therapy. A flexible artificial neural network (ANN) algorithm was developed and applied to predict ischemic tissue fate on three stroke groups: 30-, 60-minute, and permanent middle cerebral artery occlusion in rats. Cerebral blood flow (CBF), apparent diffusion coefficient (ADC), and spin–spin relaxation time constant (T2) were acquired during the acute phase up to 3 hours and again at 24 hours followed by histology. Infarct was predicted on a pixel-by-pixel basis using only acute (30-minute) stroke data. In addition, neighboring pixel information and infarction incidence were also incorporated into the ANN model to improve prediction accuracy. Receiver-operating characteristic analysis was used to quantify prediction accuracy. The major findings were the following: (1) CBF alone poorly predicted the final infarct across three experimental groups; (2) ADC alone adequately predicted the infarct; (3) CBF+ADC improved the prediction accuracy; (4) inclusion of neighboring pixel information and infarction incidence further improved the prediction accuracy; and (5) prediction was more accurate for permanent occlusion, followed by 60- and 30-minute occlusion. The ANN predictive model could thus provide a flexible and objective framework for clinicians to evaluate stroke treatment options on an individual patient basis. PMID:20424631

White Matter Hyperintensity Associations with Cerebral Blood Flow in Elderly Subjects Stratified by Cerebrovascular Risk.

PubMed

Bahrani, Ahmed A; Powell, David K; Yu, Guoquiang; Johnson, Eleanor S; Jicha, Gregory A; Smith, Charles D

2017-04-01

This study aims to add clarity to the relationship between deep and periventricular brain white matter hyperintensities (WMHs), cerebral blood flow (CBF), and cerebrovascular risk in older persons. Deep white matter hyperintensity (dWMH) and periventricular white matter hyperintensity (pWMH) and regional gray matter (GM) and white matter (WM) blood flow from arterial spin labeling were quantified from magnetic resonance imaging scans of 26 cognitively normal elderly subjects stratified by cerebrovascular disease (CVD) risk. Fluid-attenuated inversion recovery images were acquired using a high-resolution 3-dimensional (3-D) sequence that reduced partial volume effects seen with slice-based techniques. dWMHs but not pWMHs were increased in patients at high risk of CVD; pWMHs but not dWMHs were associated with decreased regional cortical (GM) blood flow. We also found that blood flow in WM is decreased in regions of both pWMH and dWMH, with a greater degree of decrease in pWMH areas. WMHs are usefully divided into dWMH and pWMH regions because they demonstrate differential effects. 3-D regional WMH volume is a potentially valuable marker for CVD based on associations with cortical CBF and WM CBF. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Regional reliability of quantitative signal targeting with alternating radiofrequency (STAR) labeling of arterial regions (QUASAR).

PubMed

Tatewaki, Yasuko; Higano, Shuichi; Taki, Yasuyuki; Thyreau, Benjamin; Murata, Takaki; Mugikura, Shunji; Ito, Daisuke; Takase, Kei; Takahashi, Shoki

2014-01-01

Quantitative signal targeting with alternating radiofrequency labeling of arterial regions (QUASAR) is a recent spin labeling technique that could improve the reliability of brain perfusion measurements. Although it is considered reliable for measuring gray matter as a whole, it has never been evaluated regionally. Here we assessed this regional reliability. Using a 3-Tesla Philips Achieva whole-body system, we scanned four times 10 healthy volunteers, in two sessions 2 weeks apart, to obtain QUASAR images. We computed perfusion images and ran a voxel-based analysis within all brain structures. We also calculated mean regional cerebral blood flow (rCBF) within regions of interest configured for each arterial territory distribution. The mean CBF over whole gray matter was 37.74 with intraclass correlation coefficient (ICC) of .70. In white matter, it was 13.94 with an ICC of .30. Voxel-wise ICC and coefficient-of-variation maps showed relatively lower reliability in watershed areas and white matter especially in deeper white matter. The absolute mean rCBF values were consistent with the ones reported from PET, as was the relatively low variability in different feeding arteries. Thus, QUASAR reliability for regional perfusion is high within gray matter, but uncertain within white matter. © 2014 The Authors. Journal of Neuroimaging published by the American Society of Neuroimaging.

Regional Reliability of Quantitative Signal Targeting with Alternating Radiofrequency (STAR) Labeling of Arterial Regions (QUASAR)

PubMed Central

Tatewaki, Yasuko; Higano, Shuichi; Taki, Yasuyuki; Thyreau, Benjamin; Murata, Takaki; Mugikura, Shunji; Ito, Daisuke; Takase, Kei; Takahashi, Shoki

2014-01-01

BACKGROUND AND PURPOSE Quantitative signal targeting with alternating radiofrequency labeling of arterial regions (QUASAR) is a recent spin labeling technique that could improve the reliability of brain perfusion measurements. Although it is considered reliable for measuring gray matter as a whole, it has never been evaluated regionally. Here we assessed this regional reliability. METHODS Using a 3-Tesla Philips Achieva whole-body system, we scanned four times 10 healthy volunteers, in two sessions 2 weeks apart, to obtain QUASAR images. We computed perfusion images and ran a voxel-based analysis within all brain structures. We also calculated mean regional cerebral blood flow (rCBF) within regions of interest configured for each arterial territory distribution. RESULTS The mean CBF over whole gray matter was 37.74 with intraclass correlation coefficient (ICC) of .70. In white matter, it was 13.94 with an ICC of .30. Voxel-wise ICC and coefficient-of-variation maps showed relatively lower reliability in watershed areas and white matter especially in deeper white matter. The absolute mean rCBF values were consistent with the ones reported from PET, as was the relatively low variability in different feeding arteries. CONCLUSIONS Thus, QUASAR reliability for regional perfusion is high within gray matter, but uncertain within white matter. PMID:25370338

Assessment of cerebral blood perfusion reserve with acetazolamide using 3D spiral ASL MRI: Preliminary experience in pediatric patients.

PubMed

Hu, Houchun H; Li, Zhiqiang; Pokorney, Amber L; Chia, Jonathan M; Stefani, Niccolo; Pipe, James G; Miller, Jeffrey H

2017-01-01

To demonstrate the clinical feasibility of a new non-Cartesian cylindrically-distributed spiral 3D pseudo-continuous arterial spin labeling (pCASL) magnetic resonance imaging (MRI) pulse sequence in pediatric patients in quantifying cerebral blood flow (CBF) response to an acetazolamide (ACZ) vasodilator challenge. MRI exams were performed on two 3 Tesla Philips Ingenia systems using 32 channel head coil arrays. After local institutional review board approval, the 3D spiral-based pCASL technique was added to a standard brain MRI exam and evaluated in 13 pediatric patients (average age: 11.7±6.4years, range: 1.4-22.2years). All patients were administered ACZ for clinically indicated reasons. Quantitative whole-brain CBF measurements were computed pre- and post-ACZ to assess cerebrovascular reserve. 3D spiral pCASL data were successfully reconstructed in all 13 cases. In 11 patients, CBF increased 2.8% to 93.2% after administration of ACZ. In the two remaining patients, CBF decreased by 2.4 to 6.0% after ACZ. The group average change in CBF due to ACZ was approximately 25.0% and individual changes were statistically significant (p<0.01) in all patients using a paired t-test analysis. CBF perfusion data were diagnostically useful in supporting conventional MR angiography and clinical findings. 3D cylindrically-distributed spiral pCASL MRI provides a robust approach to assess cerebral blood flow and reserve in pediatric patients. Copyright © 2016 Elsevier Inc. All rights reserved.

Common and Dissociable Regional Cerebral Blood Flow Differences Associate with Dimensions of Psychopathology Across Categorical Diagnoses

PubMed Central

Kaczkurkin, Antonia N.; Moore, Tyler M.; Calkins, Monica E.; Ciric, Rastko; Detre, John A.; Elliott, Mark A.; Foa, Edna B.; de La Garza, Angel Garcia; Roalf, David R.; Rosen, Adon; Ruparel, Kosha; Shinohara, Russell T.; Xia, Cedric H.; Wolf, Daniel H.; Gur, Raquel E.; Gur, Ruben C.; Satterthwaite, Theodore D.

2017-01-01

The high comorbidity among neuropsychiatric disorders suggests a possible common neurobiological phenotype. Resting-state regional cerebral blood flow (CBF) can be measured noninvasively with MRI and abnormalities in regional CBF are present in many neuropsychiatric disorders. Regional CBF may also provide a useful biological marker across different types of psychopathology. To investigate CBF changes common across psychiatric disorders, we capitalized upon a sample of 1,042 youths (ages 11 to 23 years) who completed cross-sectional imaging as part of the Philadelphia Neurodevelopmental Cohort. CBF during a resting state was quantified on a voxelwise basis using arterial spin labeled perfusion MRI at 3T. A dimensional measure of psychopathology was constructed using a bifactor model of item-level data from a psychiatric screening interview, which delineated four factors (fear, anxious-misery, psychosis, and behavioral symptoms) plus a general factor: overall psychopathology. Overall psychopathology was associated with elevated perfusion in several regions including the right dorsal anterior cingulate cortex (ACC) and left rostral ACC. Furthermore, several clusters were associated with specific dimensions of psychopathology. Psychosis symptoms were related to reduced perfusion in the left frontal operculum and insula, whereas fear symptoms were associated with less perfusion in the right occipital/fusiform gyrus and left subgenual ACC. Follow-up functional connectivity analyses using resting-state fMRI collected in the same participants revealed that overall psychopathology was associated with decreased connectivity between the dorsal ACC and bilateral caudate. Together, the results of this study demonstrate common and dissociable CBF abnormalities across neuropsychiatric disorders in youth. PMID:28924181

Short-echo 3D H-1 Magnetic Resonance Spectroscopic Imaging of patients with glioma at 7T for characterization of differences in metabolite levels

PubMed Central

Li, Yan; Larson, Peder; Chen, Albert P.; Lupo, Janine M.; Ozhinsky, Eugene; Kelley, Douglas; Chang, Susan M.; Nelson, Sarah J.

2014-01-01

Purpose The purpose of this study was to evaluate the feasibility of using a short echo time, 3D H-1 magnetic resonance spectroscopic imaging (MRSI) sequence at 7T to assess the metabolic signature of lesions for patients with glioma. Materials and Methods 29 patients with glioma were studied. MRSI data were obtained using CHESS water suppression, spectrally-selective adiabatic inversion-recovery pulses and automatically prescribed outer-volume-suppression for lipid suppression, and spin echo slice selection (TE=30ms). An interleaved flyback echo-planar trajectory was applied to shorten the total acquisition time (~10min). Relative metabolite ratios were estimated in tumor and in normal-appearing white and gray matter (NAWM, GM). Results Levels of glutamine, myo-inositol, glycine and glutathione relative to total creatine (tCr) were significantly increased in the T2 lesions for all tumor grades compared to those in the NAWM (p < 0.05), while N-acetyl aspartate to tCr were significantly decreased (p < 0.05). In grade 2 gliomas, level of total choline-containing-compounds to tCr was significantly increased (p = 0.0137), while glutamate to tCr was significantly reduced (p = 0.0012). Conclusion The improved sensitivity of MRSI and the increased number of metabolites that can be evaluated using 7T MR scanners is of interest for evaluating patients with glioma. This study has successfully demonstrated the application of a short-echo spin-echo MRSI sequence to detect characteristic differences in regions of tumor versus normal appearing brain. PMID:24935758

Dual-pathway multi-echo sequence for simultaneous frequency and T2 mapping

NASA Astrophysics Data System (ADS)

Cheng, Cheng-Chieh; Mei, Chang-Sheng; Duryea, Jeffrey; Chung, Hsiao-Wen; Chao, Tzu-Cheng; Panych, Lawrence P.; Madore, Bruno

2016-04-01

Purpose: To present a dual-pathway multi-echo steady state sequence and reconstruction algorithm to capture T2, T2∗ and field map information. Methods: Typically, pulse sequences based on spin echoes are needed for T2 mapping while gradient echoes are needed for field mapping, making it difficult to jointly acquire both types of information. A dual-pathway multi-echo pulse sequence is employed here to generate T2 and field maps from the same acquired data. The approach might be used, for example, to obtain both thermometry and tissue damage information during thermal therapies, or susceptibility and T2 information from a same head scan, or to generate bonus T2 maps during a knee scan. Results: Quantitative T2, T2∗ and field maps were generated in gel phantoms, ex vivo bovine muscle, and twelve volunteers. T2 results were validated against a spin-echo reference standard: A linear regression based on ROI analysis in phantoms provided close agreement (slope/R2 = 0.99/0.998). A pixel-wise in vivo Bland-Altman analysis of R2 = 1/T2 showed a bias of 0.034 Hz (about 0.3%), as averaged over four volunteers. Ex vivo results, with and without motion, suggested that tissue damage detection based on T2 rather than temperature-dose measurements might prove more robust to motion. Conclusion: T2, T2∗ and field maps were obtained simultaneously, from the same datasets, in thermometry, susceptibility-weighted imaging and knee-imaging contexts.

An anisotropic diffusion method for denoising dynamic susceptibility contrast-enhanced magnetic resonance images

NASA Astrophysics Data System (ADS)

Murase, Kenya; Yamazaki, Youichi; Shinohara, Masaaki; Kawakami, Kazunori; Kikuchi, Keiichi; Miki, Hitoshi; Mochizuki, Teruhito; Ikezoe, Junpei

2001-10-01

The purpose of this study was to present an application of a novel denoising technique for improving the accuracy of cerebral blood flow (CBF) images generated from dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSC-MRI). The method presented in this study was based on anisotropic diffusion (AD). The usefulness of this method was firstly investigated using computer simulations. We applied this method to patient data acquired using a 1.5 T MR system. After a bolus injection of Gd-DTPA, we obtained 40-50 dynamic images with a 1.32-2.08 s time resolution in 4-6 slices. The dynamic images were processed using the AD method, and then the CBF images were generated using pixel-by-pixel deconvolution analysis. For comparison, the CBF images were also generated with or without processing the dynamic images using a median or Gaussian filter. In simulation studies, the standard deviation of the CBF values obtained after processing by the AD method was smaller than that of the CBF values obtained without any processing, while the mean value agreed well with the true CBF value. Although the median and Gaussian filters also reduced image noise, the mean CBF values were considerably underestimated compared with the true values. Clinical studies also suggested that the AD method was capable of reducing the image noise while preserving the quantitative accuracy of CBF images. In conclusion, the AD method appears useful for denoising DSC-MRI, which will make the CBF images generated from DSC-MRI more reliable.

Wavelength-independent constant period spin-echo modulated small angle neutron scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sales, Morten, E-mail: lsp260@alumni.ku.dk; Plomp, Jeroen; Bouwman, Wim

2016-06-15

Spin-Echo Modulated Small Angle Neutron Scattering (SEMSANS) in Time-of-Flight (ToF) mode has been shown to be a promising technique for measuring (very) small angle neutron scattering (SANS) signals and performing quantitative Dark-Field Imaging (DFI), i.e., SANS with 2D spatial resolution. However, the wavelength dependence of the modulation period in the ToF spin-echo mode has so far limited the useful modulation periods to those resolvable with the limited spatial resolution of the detectors available. Here we present our results of an approach to keep the period of the induced modulation constant for the wavelengths utilised in ToF. This is achieved bymore » ramping the magnetic fields in the coils responsible for creating the spatially modulated beam in synchronisation with the neutron pulse, thus keeping the modulation period constant for all wavelengths. Such a setup enables the decoupling of the spatial detector resolution from the resolution of the modulation period by the use of slits or gratings in analogy to the approach in grating-based neutron DFI.« less

Rabi oscillation and electron-spin-echo envelope modulation of the photoexcited triplet spin system in silicon

NASA Astrophysics Data System (ADS)

Akhtar, Waseem; Sekiguchi, Takeharu; Itahashi, Tatsumasa; Filidou, Vasileia; Morton, John J. L.; Vlasenko, Leonid; Itoh, Kohei M.

2012-09-01

We report on a pulsed electron paramagnetic resonance (EPR) study of the photoexcited triplet state (S=1) of oxygen-vacancy centers in silicon. Rabi oscillations between the triplet sublevels are observed using coherent manipulation with a resonant microwave pulse. The Hahn echo and stimulated echo decay profiles are superimposed with strong modulations known as electron-spin-echo envelope modulation (ESEEM). The ESEEM spectra reveal a weak but anisotropic hyperfine coupling between the triplet electron spin and a 29Si nuclear spin (I=1/2) residing at a nearby lattice site, that cannot be resolved in conventional field-swept EPR spectra.

Fundamental Study of Three-dimensional Fast Spin-echo Imaging with Spoiled Equilibrium Pulse.

PubMed

Ogawa, Masashi; Kaji, Naoto; Tsuchihashi, Toshio

2017-01-01

Three-dimensional fast spin-echo (3D FSE) imaging with variable refocusing flip angle has been recently applied to pre- or post-enhanced T 1 -weighted imaging. To reduce the acquisition time, this sequence requires higher echo train length (ETL), which potentially causes decreased T 1 contrast. Spoiled equilibrium (SpE) pulse consists of a resonant +90° radiofrequency (RF) pulse and is applied at the end of the echo train. This +90° RF pulse brings residual transverse magnetization to the negative longitudinal axis, which makes it possible to increase T 1 contrast. The purpose of our present study was to examine factors that influence the effect of spoiled equilibrium pulse and the relationship between T 1 contrast improvement and imaging parameters and to understand the characteristics of spoiled equilibrium pulse. Phantom studies were conducted using an magnetic resonance imaging (MRI) phantom made of polyvinyl alcohol gel. To evaluate the effect of spoiled equilibrium pulse with changes in repetition time (TR), ETL, and refocusing flip angle, we measured the signal-to-noise ratio and contrast-to-noise ratio (CNR). The effect of spoiled equilibrium pulse was evaluated by calculating the enhancement rate of CNR. The factors that influence the effect of spoiled equilibrium pulse are TR, ETL, and relaxation time of tissues. Spoiled equilibrium pulse is effective with increasing TR and decreasing ETL. The shorter the T 1 value, the better the spoiled equilibrium pulse functions. However, for tissues in which the T 1 value is long (>600 ms), at a TR of 600 ms, improvement in T 1 contrast by applying spoiled equilibrium pulse cannot be expected.

Self-diffusion imaging by spin echo in Earth's magnetic field.

PubMed

Mohoric, A; Stepisnik, J; Kos, M; Planinsi

1999-01-01

The NMR of the Earth's magnetic field is used for diffusion-weighted imaging of phantoms. Due to a weak Larmor field, care needs to be taken regarding the use of the usual high field assumption in calculating the effect of the applied inhomogeneous magnetic field. The usual definition of the magnetic field gradient must be replaced by a generalized formula valid when the strength of a nonuniform magnetic field and a Larmor field are comparable (J. Stepisnik, Z. Phys. Chem. 190, 51-62 (1995)). It turns out that the expression for spin echo attenuation is identical to the well-known Torrey formula only when the applied nonuniform field has a proper symmetry. This kind of problem may occur in a strong Larmor field as well as when the slow diffusion rate of particles needs an extremely strong gradient to be applied. The measurements of the geomagnetic field NMR demonstrate the usefulness of the method for diffusion and flow-weighted imaging. Copyright 1999 Academic Press.

Diffusion-weighted magnetic resonance imaging of uterine cervical cancer.

PubMed

Liu, Ying; Bai, Renju; Sun, Haoran; Liu, Haidong; Wang, Dehua

2009-01-01

To determine the feasibility of diffusion-weighted magnetic resonance (MR) imaging (DWI) of uterine cervical cancer and to investigate whether the apparent diffusion coefficient (ADC) values of cervical cancer differ from those of normal cervix and whether they could indicate the histologic type and the pathologic grade of tumor. Forty-two female patients with histopathologically proven uterine cervical cancer and 15 female patients with uterine leiomyomas underwent preoperative MR examinations using a 1.5-T clinical scanner (GE 1.5T Twin-Speed Infinity with Excite II scanner; GE Healthcare, Waukesha, Wis). Scanning sequences included T2-weighted fast spin-echo imaging, T2-weighted fast spin-echo with fat suppression imaging, T1-weighted spin-echo imaging, and DWI with diffusion factors of 0 and 1000 s/mm2. Parameters evaluated consisted of ADC values of uterine cervical cancer and normal cervix. Histologic specimens were stained with hematoxylin and eosin. The cellular densities of 32 uterine cervical cancers were calculated, which were regarded as the ratio of the total area of tumor cell nuclei divided by the area of sample image. Apparent diffusion coefficient value was statistically different (P = 0.000) between normal and cancerous tissue in the uterine cervix; the former one was (mean [SD], 1.50 [0.16]) x 10(-3) mm2/s, and the latter one was (0.88 [0.15]) x 10(-3) mm2/s. Apparent diffusion coefficient value of squamous carcinoma was statistically lower than that of adenocarcinoma (P = 0.040). The ADC value of uterine cervical cancer correlated negatively with cellular density (r = -0.711, P = 0.000) and the grading of tumor (r = -0.778, P = 0.000). Diffusion-weighted MR imaging has a potential ability to differentiate between normal and cancerous tissue in the uterine cervix, and it can indicate the histologic type of uterine cervical cancer as well. The ADC value of uterine cervical cancer represents tumor cellular density, thus providing a new method for evaluating the pathologic grading of tumor.

Increased resting cerebral blood flow in adult Fabry disease: MRI arterial spin labeling study.

PubMed

Phyu, Po; Merwick, Aine; Davagnanam, Indran; Bolsover, Fay; Jichi, Fatima; Wheeler-Kingshott, Claudia; Golay, Xavier; Hughes, Deralynn; Cipolotti, Lisa; Murphy, Elaine; Lachmann, Robin H; Werring, David John

2018-04-17

To assess resting cerebral blood flow (CBF) in the whole-brain and cerebral white matter (WM) and gray matter (GM) of adults with Fabry disease (FD), using arterial spin labeling (ASL) MRI, and to investigate CBF correlations with WM hyperintensity (WMH) volume and the circulating biomarker lyso-Gb3. This cross-sectional, case-control study included 25 patients with genetically confirmed FD and 18 age-matched healthy controls. We quantified resting CBF using Quantitative Signal Targeting With Alternating Radiofrequency Labeling of Arterial Regions (QUASAR) ASL MRI. We measured WMH volume using semiautomated software. We measured CBF in regions of interest in whole-brain, WM, and deep GM, and assessed correlations with WMH volume and plasma lyso-Gb3. The mean age (% male) for FD and healthy controls was 42.2 years (44%) and 37.1 years (50%). Mean whole-brain CBF was 27.56 mL/100 mL/min (95% confidence interval [CI] 23.78-31.34) for FD vs 22.39 mL/100 mL/min (95% CI 20.08-24.70) for healthy controls, p = 0.03. In WM, CBF was higher in FD (22.42 mL/100 mL/min [95% CI 17.72-27.12] vs 16.25 mL/100 mL/min [95% CI 14.03-18.48], p = 0.05). In deep GM, CBF was similar between groups (40.41 mL/100 mL/min [95% CI 36.85-43.97] for FD vs 37.46 mL/100 mL/min [95% CI 32.57-42.35], p = 0.38). In patients with FD with WMH (n = 20), whole-brain CBF correlated with WMH volume ( r = 0.59, p = 0.006), not with plasma lyso-Gb3. In FD, resting CBF is increased in WM but not deep GM. In FD, CBF correlates with WMH, suggesting that cerebral perfusion changes might contribute to, or result from, WM injury. © 2018 American Academy of Neurology.

[Study of 3D-pcASL in differentiation of acute cerebral infarction and acute encephalitis].

PubMed

Mao, Chuanwan; Fu, Yuchuan; Ye, Xinjian; Wu, Aiqin; Yan, Zhihan

2015-06-16

To investigate the value of three-dimentional pseudo-continuous arterial spin labeling (ASL) perfusion imaging in differentiating acute cerebral infarction from acute encephalitis. From September 2013 to September 2014, 42 patients with actue stroke onset and 20 healthy volunteers underwent conventional brain MRI DWI and 3D-ASL Perfusion Imaging in our hospital. Only 20 patients whose lesions located in the middle cerebral artery (MCA) territory were enrolled in this study. Of these cases, 12 cases were diagnosed with acute cerebral infarction, 8 were diagnosed with encephalitis. First, we analyzed the imaging features of the 20 patients and 20 volunteers. Then, CBF values of the lesions in the 20 patients and the gray matter of MCA territory in the 20 volunteers were measured on 3D-pcASL images. Third, the difference of mean CBF values between patients and volunteers were analyzed. Out of 20 study group, 19 patients whose lesions presented high signal intensity on DWI images, 12 cases were acute cerebral infarction and 8 were encephalitis. All the lesions of 20 cases showed abnormal perfusion on 3D-pcASL images. 3D-pcASL has good consistency with DWI in diagnostic capabilities (χ² = 0.565, P = 0.01). On 3D-pcASL, 11 acute cerebral infarction patients presented perfusion defects or low perfusion, 1 acute cerebral infarction patients showed high perfusion, 8 encephalitis patients showed inhomogeneous perfusion. The mean value of CBF was (17 ± 6) ml · min⁻¹ · 100 g⁻¹ in 12 acute cerebral infarction patients, (136 ± 69) ml · min⁻¹ · 100 g⁻¹ in 8 encephalitis patients and (68 ± 12) ml · min⁻¹ · 100 g⁻¹ three in 20 healthy volunteers. The difference in mean value of CBF among the three groups was statistically significant (P < 0.01). Acute cerebral infarction often shows low perfusion and acute encephalitis shows high perfusion on 3D-pcASL images, which has a higher application value in diagnosis and differentiation of acute cerebral infarction and encephalitis.

The Effect of Concomitant Fields in Fast Spin Echo Acquisition on Asymmetric MRI Gradient Systems

PubMed Central

Tao, Shengzhen; Weavers, Paul T.; Trzasko, Joshua D.; Huston, John; Shu, Yunhong; Gray, Erin M.; Foo, Thomas K.F.; Bernstein, Matt A.

2017-01-01

Purpose To investigate the effect of the asymmetric gradient concomitant fields (CF) with zeroth and first-order spatial dependence on fast/turbo spin-echo acquisitions, and to demonstrate the effectiveness of their real-time compensation. Methods After briefly reviewing the CF produced by asymmetric gradients, the effects of the additional zeroth and first-order CFs on these systems are investigated using extended-phase graph simulations. Phantom and in vivo experiments are performed to corroborate the simulation. Experiments are performed before and after the real-time compensations using frequency tracking and gradient pre-emphasis to demonstrate their effectiveness in correcting the additional CFs. The interaction between the CFs and prescan-based correction to compensate for eddy currents is also investigated. Results It is demonstrated that, unlike the second-order CFs on conventional gradients, the additional zeroth/first-order CFs on asymmetric gradients cause substantial signal loss and dark banding in fast spin-echo acquisitions within a typical brain-scan field of view. They can confound the prescan correction for eddy currents and degrade image quality. Performing real-time compensation successfully eliminates the artifacts. Conclusions We demonstrate that the zeroth/first-order CFs specific to asymmetric gradients can cause substantial artifacts, including signal loss and dark bands for brain imaging. These effects can be corrected using real-time compensation. PMID:28643408

Polarisation in spin-echo experiments: Multi-point and lock-in measurements

NASA Astrophysics Data System (ADS)

Tamtögl, Anton; Davey, Benjamin; Ward, David J.; Jardine, Andrew P.; Ellis, John; Allison, William

2018-02-01

Spin-echo instruments are typically used to measure diffusive processes and the dynamics and motion in samples on ps and ns time scales. A key aspect of the spin-echo technique is to determine the polarisation of a particle beam. We present two methods for measuring the spin polarisation in spin-echo experiments. The current method in use is based on taking a number of discrete readings. The implementation of a new method involves continuously rotating the spin and measuring its polarisation after being scattered from the sample. A control system running on a microcontroller is used to perform the spin rotation and to calculate the polarisation of the scattered beam based on a lock-in amplifier. First experimental tests of the method on a helium spin-echo spectrometer show that it is clearly working and that it has advantages over the discrete approach, i.e., it can track changes of the beam properties throughout the experiment. Moreover, we show that real-time numerical simulations can perfectly describe a complex experiment and can be easily used to develop improved experimental methods prior to a first hardware implementation.

Phase incremented echo train acquisition applied to magnetic resonance pore imaging

NASA Astrophysics Data System (ADS)

Hertel, S. A.; Galvosas, P.

2017-02-01

Efficient phase cycling schemes remain a challenge for NMR techniques if the pulse sequences involve a large number of rf-pulses. Especially complex is the Carr Purcell Meiboom Gill (CPMG) pulse sequence where the number of rf-pulses can range from hundreds to several thousands. Our recent implementation of Magnetic Resonance Pore Imaging (MRPI) is based on a CPMG rf-pulse sequence in order to refocus the effect of internal gradients inherent in porous media. While the spin dynamics for spin- 1 / 2 systems in CPMG like experiments are well understood it is still not straight forward to separate the desired pathway from the spectrum of unwanted coherence pathways. In this contribution we apply Phase Incremented Echo Train Acquisition (PIETA) to MRPI. We show how PIETA offers a convenient way to implement a working phase cycling scheme and how it allows one to gain deeper insights into the amplitudes of undesired pathways.

Preoperative detection of malignant liver tumors: Comparison of 3D-T2-weighted sequences with T2-weighted turbo spin-echo and single shot T2 at 1.5 T.

PubMed

Barat, Maxime; Soyer, Philippe; Dautry, Raphael; Pocard, Marc; Lo-Dico, Rea; Najah, Haythem; Eveno, Clarisse; Cassinotto, Christophe; Dohan, Anthony

2018-03-01

To assess the performances of three-dimensional (3D)-T2-weighted sequences compared to standard T2-weighted turbo spin echo (T2-TSE), T2-half-Fourier acquisition single-shot turbo spin-echo (T2-HASTE), diffusion weighted imaging (DWI) and 3D-T1-weighted VIBE sequences in the preoperative detection of malignant liver tumors. From 2012 to 2015, all patients of our institution undergoing magnetic resonance imaging (MRI) examination for suspected malignant liver tumors were prospectively included. Patients had contrast-enhanced 3D-T1-weighted, DWI, 3D-T2-SPACE, T2-HASTE and T2-TSE sequences. Imaging findings were compared with those obtained at follow-up, surgery and histopathological analysis. Sensitivities for the detection of malignant liver tumors were compared for each sequence using McNemar test. A subgroup analysis was conducted for HCCs. Image artifacts were analyzed and compared using Wilcoxon paired signed rank-test. Thirty-three patients were included: 13 patients had 40 hepatocellular carcinomas (HCC) and 20 had 54 liver metastases. 3D-T2-weighted sequences had a higher sensitivity than T2-weighted TSE sequences for the detection of malignant liver tumors (79.8% versus 68.1%; P < 0.001). The difference did not reach significance for HCC. T1-weighted VIBE and DWI had a higher sensitivity than T2-weighted sequences. 3D-T2-weighted-SPACE sequences showed significantly less artifacts than T2-weitghted TSE. 3D-T2-weighted sequences show very promising performances for the detection of liver malignant tumors compared to T2-weighted TSE sequences. Copyright © 2018 Elsevier B.V. All rights reserved.

MRI measurement of angiogenesis and the therapeutic effect of acute marrow stromal cell administration on traumatic brain injury.

PubMed

Li, Lian; Chopp, Michael; Ding, Guang Liang; Qu, Chang Sheng; Li, Qing Jiang; Lu, Mei; Wang, Shiyang; Nejad-Davarani, Siamak P; Mahmood, Asim; Jiang, Quan

2012-11-01

Using magnetic resonance imaging (MRI), the present study was undertaken to investigate the therapeutic effect of acute administration of human bone marrow stromal cells (hMSCs) on traumatic brain injury (TBI) and to measure the temporal profile of angiogenesis after the injury with or without cell intervention. Male Wistar rats (300 to 350 g, n=18) subjected to controlled cortical impact TBI were intravenously injected with 1 mL of saline (n=9) or hMSCs in suspension (n=9, 3 × 10(6) hMSCs) 6 hours after TBI. In-vivo MRI acquisitions of T2-weighted imaging, cerebral blood flow (CBF), three-dimensional (3D) gradient echo imaging, and blood-to-brain transfer constant (Ki) of contrast agent were performed on all animals 2 days after injury and weekly for 6 weeks. Sensorimotor function and spatial learning were evaluated. Volumetric changes in the trauma-induced brain lesion and the lateral ventricles were tracked and quantified using T2 maps, and hemodynamic alteration and blood-brain barrier permeability were monitored by CBF and Ki, respectively. Our data show that transplantation of hMSCs 6 hours after TBI leads to reduced cerebral atrophy, early and enhanced cerebral tissue perfusion and improved functional outcome compared with controls. The hMSC treatment increases angiogenesis in the injured brain, which may promote neurologic recovery after TBI.

Advanced cardiac chemical exchange saturation transfer (cardioCEST) MRI for in vivo cell tracking and metabolic imaging

PubMed Central

Pumphrey, Ashley; Yang, Zhengshi; Ye, Shaojing; Powell, David K.; Thalman, Scott; Watt, David S.; Abdel-Latif, Ahmed; Unrine, Jason; Thompson, Katherine; Fornwalt, Brandon; Ferrauto, Giuseppe; Vandsburger, Moriel

2016-01-01

An improved pre-clinical cardiac chemical exchange saturation transfer (CEST) pulse sequence (cardioCEST) was used to selectively visualize paramagnetic CEST (paraCEST)-labeled cells following intramyocardial implantation. In addition, cardioCEST was used to examine the effect of diet-induced obesity upon myocardial creatine CEST contrast. CEST pulse sequences were designed from standard turbo-spin-echo and gradient-echo sequences, and a cardiorespiratory-gated steady-state cine gradient-echo sequence. In vitro validation studies performed in phantoms composed of 20mM Eu-HPDO3A, 20mM Yb-HPDO3A, or saline demonstrated similar CEST contrast by spin-echo and gradient-echo pulse sequences. Skeletal myoblast cells (C2C12) were labeled with either Eu-HPDO3A or saline using a hypotonic swelling procedure and implanted into the myocardium of C57B6/J mice. Inductively coupled plasma mass spectrometry confirmed cellular levels of Eu of 2.1 × 10−3 ng/cell in Eu-HPDO3A-labeled cells and 2.3 × 10−5 ng/cell in saline-labeled cells. In vivo cardioCEST imaging of labeled cells at ±15ppm was performed 24 h after implantation and revealed significantly elevated asymmetric magnetization transfer ratio values in regions of Eu-HPDO3A-labeled cells when compared with surrounding myocardium or saline-labeled cells. We further utilized the cardioCEST pulse sequence to examine changes in myocardial creatine in response to diet-induced obesity by acquiring pairs of cardioCEST images at ±1.8 ppm. While ventricular geometry and function were unchanged between mice fed either a high-fat diet or a corresponding control low-fat diet for 14 weeks, myocardial creatine CEST contrast was significantly reduced in mice fed the high-fat diet. The selective visualization of paraCEST-labeled cells using cardioCEST imaging can enable investigation of cell fate processes in cardioregenerative medicine, or multiplex imaging of cell survival with imaging of cardiac structure and function and additional imaging of myocardial creatine. PMID:26684053

Task Related Cerebral Blood Flow Changes of Patients with Chronic Fatigue Syndrome: An Arterial Spin Labeling Study.

PubMed

Staud, Roland; Boissoneault, Jeff; Craggs, Jason G; Lai, Song; Robinson, Michael E

2018-01-01

One hallmark of chronic fatigue syndrome (ME/CFS) is task related worsening of fatigue. Global brain hypoperfusion, abnormal regional activation, and altered functional connectivity of brain areas associated with cognition and memory have been reported but remain controversial. We enrolled 17 female participants fulfilling the CDC Criteria for ME/CFS and 16 matched healthy controls (HC). Using a 3T-Phillips Achieva MRI-scanner, pseudo-continuous arterial spin-labeling (pCASL), was used to study the dynamics of regional cerebral blood flow (rCBF) and their relationship to mental fatigue in ME/CFS patients and HC during a demanding cognitive task, i.e. modified Paced-Auditory-Serial-Addition-Testing (PASAT). ME/CFS subjects reported more fatigue than HC at baseline (p < .01). Global brain perfusion of ME/CFS and HC subjects was similar at rest. The PASAT resulted in significantly increased fatigue in ME/CFS participants and HC. Although not different between groups, overall CBF significantly increased over the first 3 min of the PASAT and then decreased thereafter. Regional CBF (rCBF) changes were significantly different between groups during the post-task recovery period. Whereas improvement of fatigue of ME/CFS subjects was associated with decreased rCBF in both superior temporal gyri (STG), precuneus, and fusiform gyrus, it was associated with increased rCBF in the same areas in HC. Our results suggest that ME/CFS is associated with normal global CBF at rest and during a strenuous task (PASAT); however rCBF of several brain regions associated with memory, goal-oriented attention, and visual function was differentially associated with recovery from fatigue in ME/CFS patients and HC.

Task Related Cerebral Blood Flow Changes of Patients with Chronic Fatigue Syndrome: An Arterial Spin Labeling Study

PubMed Central

Staud, Roland; Boissoneault, Jeff; Craggs, Jason G.; Lai, Song; Robinson, Michael E.

2018-01-01

Purpose One hallmark of chronic fatigue syndrome (ME/CFS) is task related worsening of fatigue. Global brain hypoperfusion, abnormal regional activation, and altered functional connectivity of brain areas associated with cognition and memory have been reported but remain controversial. Methods We enrolled 17 female participants fulfilling the CDC Criteria for ME/CFS and 16 matched healthy controls (HC). Using a 3T-Phillips Achieva MRI-scanner, pseudo-continuous arterial spin-labeling (pCASL), was used to study the dynamics of regional cerebral blood flow (rCBF) and their relationship to mental fatigue in ME/CFS patients and HC during a demanding cognitive task, i.e. modified Paced-Auditory-Serial-Addition-Testing (PASAT). Results ME/CFS subjects reported more fatigue than HC at baseline (p < .01). Global brain perfusion of ME/CFS and HC subjects was similar at rest. The PASAT resulted in significantly increased fatigue in ME/CFS participants and HC. Although not different between groups, overall CBF significantly increased over the first 3 min of the PASAT and then decreased thereafter. Regional CBF (rCBF) changes were significantly different between groups during the post-task recovery period. Whereas improvement of fatigue of ME/CFS subjects was associated with decreased rCBF in both superior temporal gyri (STG), precuneus, and fusiform gyrus, it was associated with increased rCBF in the same areas in HC. Conclusions Our results suggest that ME/CFS is associated with normal global CBF at rest and during a strenuous task (PASAT); however rCBF of several brain regions associated with memory, goal-oriented attention, and visual function was differentially associated with recovery from fatigue in ME/CFS patients and HC. PMID:29707427

Neuroperformance Imaging

DTIC Science & Technology

2012-10-01

EMBC10.1722. 10. Mitra, P.P., Halperin, B.I.: Effects of finite gradient-pulse widths in pulsed- field - gradient diffusion measurements . Journal of Magnetic ...December 2011 ABSTRACT: The addition of a pair of magnetic field gradient pulses had initially enabled the measurement of spin motion to nuclear mag- netic...introduced a pair of (homogenous) magnetic field gradients into the spin echo experi- ment with the purpose of accurately measuring the scalar diffusion

Coagulative interstitial laser-induced thermotherapy of benign prostatic hyperplasia: online imaging with a T2-weighted fast spin-echo MR sequence--experience in six patients.

PubMed

Mueller-Lisse, U G; Thoma, M; Faber, S; Heuck, A F; Muschter, R; Schneede, P; Weninger, E; Hofstetter, A G; Reiser, M F

1999-02-01

To determine if hypointense lesions clearly outline on T2-weighted fast spin-echo (SE) magnetic resonance (MR) images obtained during coagulative interstitial laser-induced thermotherapy (LITT) of a prostate with benign hyperplasia. In six patients with benign prostatic hyperplasia (BPH), 12 LITT treatments were followed online with repetitive axial T2-weighted fast SE imaging (repetition time, 3,700 msec; echo time, 138 msec; acquisition time, 19 seconds). Development, time course, correlation with interstitial tissue temperature, and diameters of hypointense lesions around the laser diffusor tip were investigated. Lesion diameters on T2-weighted images acquired during LITT were compared with diameters of final lesions on T2-weighted images and unperfused lesions on enhanced T1-weighted SE images obtained at the end of therapy. Hypointense lesions developed within 20-40 seconds of LITT. Average correlation coefficients between interstitial temperature development and signal intensity development were 0.92 during LITT and 0.90 after LITT. Regression slopes were significantly steeper during LITT (0.67% signal intensity change per degree Celsius) than after LITT (0.47% per degree Celsius; P = .038). Lesions remained visible after LITT for all procedures. Average maximum diameters of lesions were 1-3 mm larger during LITT than after LITT (P = .0006-.019). Repetitive T2-weighted fast SE MR imaging during interstitial coagulative LITT of BPH demonstrates the development of permanent hypointense prostate lesions. However, posttherapeutic lesion diameters tend to be overestimated during LITT.

The relationship of resting cerebral blood flow and brain activation during a social cognition task in adolescents with chronic moderate to severe traumatic brain injury: a preliminary investigation.

PubMed

Newsome, Mary R; Scheibel, Randall S; Chu, Zili; Hunter, Jill V; Li, Xiaoqi; Wilde, Elisabeth A; Lu, Hanzhang; Wang, Zhiyue J; Lin, Xiaodi; Steinberg, Joel L; Vasquez, Ana C; Cook, Lori; Levin, Harvey S

2012-05-01

Alterations in cerebrovascular function are evident acutely in moderate to severe traumatic brain injury (TBI), although less is known about their chronic effects. Adolescent and adult patients with moderate to severe TBI have been reported to demonstrate diffuse activation throughout the brain during functional magnetic resonance imaging (fMRI). Because fMRI is a measure related to blood flow, it is possible that any deficits in blood flow may alter activation. An arterial spin labeling (ASL) perfusion sequence was performed on seven adolescents with chronic moderate to severe TBI and seven typically developing (TD) adolescents during the same session in which they had performed a social cognition task during fMRI. In the TD group, prefrontal CBF was positively related to prefrontal activation and negatively related to non-prefrontal, posterior, brain activation. This relationship was not seen in the TBI group, who demonstrated a greater positive relationship between prefrontal CBF and non-prefrontal activation than the TD group. An analysis of CBF data independent of fMRI showed reduced CBF in the right non-prefrontal region (p<.055) in the TBI group. To understand any role reduced CBF may play in diffuse extra-activation, we then related the right non-prefrontal CBF to activation. CBF in the right non-prefrontal region in the TD group was positively associated with prefrontal activation, suggesting an interactive role of non-prefrontal and prefrontal blood flow throughout the right hemisphere in healthy brains. However, the TBI group demonstrated a positive association with activation constrained to the right non-prefrontal region. These data suggest a relationship between impaired non-prefrontal CBF and the presence of non-prefrontal extra-activation, where the region with more limited blood flow is associated with activation limited to that region. In a secondary analysis, pathology associated with hyperintensities on T2-weighted FLAIR imaging over the whole brain was related to whole brain activation, revealing a negative relationship between lesion volume and frontal activation, and a positive relationship between lesion volume and posterior activation. These preliminary data, albeit collected with small sample sizes, suggest that reduced non-prefrontal CBF, and possibly pathological tissue associated with T2-hyperintensities, may provide contributions to the diffuse, primarily posterior extra-activation observed in adolescents following moderate to severe TBI. Published by Elsevier Ltd.

MRI T2 Mapping of the Knee Articular Cartilage Using Different Acquisition Sequences and Calculation Methods at 1.5 Tesla.

PubMed

Mars, Mokhtar; Bouaziz, Mouna; Tbini, Zeineb; Ladeb, Fethi; Gharbi, Souha

2018-06-12

This study aims to determine how Magnetic Resonance Imaging (MRI) acquisition techniques and calculation methods affect T2 values of knee cartilage at 1.5 Tesla and to identify sequences that can be used for high-resolution T2 mapping in short scanning times. This study was performed on phantom and twenty-nine patients who underwent MRI of the knee joint at 1.5 Tesla. The protocol includes T2 mapping sequences based on Single Echo Spin Echo (SESE), Multi-Echo Spin Echo (MESE), Fast Spin Echo (FSE) and Turbo Gradient Spin Echo (TGSE). The T2 relaxation times were quantified and evaluated using three calculation methods (MapIt, Syngo Offline and monoexponential fit). Signal to Noise Ratios (SNR) were measured in all sequences. All statistical analyses were performed using the t-test. The average T2 values in phantom were 41.7 ± 13.8 ms for SESE, 43.2 ± 14.4 ms for MESE, 42.4 ± 14.1 ms for FSE and 44 ± 14.5 ms for TGSE. In the patient study, the mean differences were 6.5 ± 8.2 ms, 7.8 ± 7.6 ms and 8.4 ± 14.2 ms for MESE, FSE and TGSE compared to SESE respectively; these statistical results were not significantly different (p > 0.05). The comparison between the three calculation methods showed no significant difference (p > 0.05). t-Test showed no significant difference between SNR values for all sequences. T2 values depend not only on the sequence type but also on the calculation method. None of the sequences revealed significant differences compared to the SESE reference sequence. TGSE with its short scanning time can be used for high-resolution T2 mapping. ©2018The Author(s). Published by S. Karger AG, Basel.

Evaluation of Chondrocalcinosis and Associated Knee Joint Degeneration Using MR Imaging: Data from the Osteoarthritis Initiative.

PubMed

Gersing, Alexandra S; Schwaiger, Benedikt J; Heilmeier, Ursula; Joseph, Gabby B; Facchetti, Luca; Kretzschmar, Martin; Lynch, John A; McCulloch, Charles E; Nevitt, Michael C; Steinbach, Lynne S; Link, Thomas M

2017-06-01

To evaluate the ability of different MRI sequences to detect chondrocalcinosis within knee cartilage and menisci, and to analyze the association with joint degeneration. Subjects with radiographic knee chondrocalcinosis (n = 90, age 67.7 ± 7.3 years, 50 women) were selected from the Osteoarthritis Initiative and matched to controls without radiographic chondrocalcinosis (n = 90). Visualization of calcium-containing crystals (CaC) was compared between 3D T1-weighted gradient-echo (T1GE), 3D dual echo steady-state (DESS), 2D intermediate-weighted (IW), and proton density (PD)-weighted fast spin-echo (FSE) sequences obtained with 3T MRI and correlated with a semiquantitative CaC score obtained from radiographs. Structural abnormalities were assessed using Whole-Organ MRI Score (WORMS) and logistic regression models were used to compare cartilage compartments with and without CaC. Correlations between CaC counts of MRI sequences and degree of radiographic calcifications were highest for GE (r T1GE  = 0.73, P < 0.001; r DESS  = 0.68, P < 0.001) compared to other sequences (P > 0.05). Meniscus WORMS was significantly higher in subjects with chondrocalcinosis compared to controls (P = 0.005). Cartilage defects were significantly more frequent in compartments with CaC than without (patella: P = 0.006; lateral tibia: P < 0.001; lateral femur condyle: P = 0.017). Gradient-echo sequences were most useful for the detection of chondrocalcinosis and presence of CaC was associated with higher prevalence of cartilage and meniscal damage. • Magnetic resonance imaging is useful for assessing burden of calcium-containing crystals (CaC). • Gradient-echo sequences are superior to fast spin echo sequences for CaC imaging. • Presence of CaC is associated with meniscus and cartilage degradation.

Quantitative analysis of the breath-holding half-Fourier acquisition single-shot turbo spin-echo technique in abdominal MRI

NASA Astrophysics Data System (ADS)

Dong, Kyung-Rae; Goo, Eun-Hoe; Lee, Jae-Seung; Chung, Woon-Kwan

2013-01-01

A consecutive series of 50 patients (28 males and 22 females) who underwent hepatic magnetic resonance imaging (MRI) from August to December 2011 were enrolled in this study. The appropriate parameters for abdominal MRI scans were determined by comparing the images (TE = 90 and 128 msec) produced using the half-Fourier acquisition single-shot turbo spin-echo (HASTE) technique at different signal acquisition times. The patients consisted of 15 normal patients, 25 patients with a hepatoma and 10 patients with a hemangioma. The TE in a single patient was set to either 90 msec or 128 msec. This was followed by measurements using the four normal rendering methods of the biliary tract system and the background signal intensity using the maximal signal intensity techniques in the liver, spleen, pancreas, gallbladder, fat, muscles and hemangioma. The signal-to-noise and the contrast-to-noise ratios were obtained. The image quality was assessed subjectively, and the results were compared. The signal-to-noise and the contrast-to-noise ratios were significantly higher at TE = 128 msec than at TE = 90 when diseases of the liver, spleen, pancreas, gallbladder, and fat and muscles, hepatocellular carcinomas and hemangiomas, and rendering the hepatobiliary tract system based on the maximum signal intensity technique were involved (p < 0.05). In addition, the presence of artifacts, the image clarity and the overall image quality were excellent at TE = 128 msec (p < 0.05). In abdominal MRI, the breath-hold half-Fourier acquisition single-shot turbo spin-echo (HASTE) was found to be effective in illustrating the abdominal organs for TE = 128 msec. Overall, the image quality at TE = 128 msec was better than that at TE = 90 msec due to the improved signal-to-noise (SNR) and contrast-to-noise (CNR) ratios. Overall, the HASTE technique for abdominal MRI based on a high-magnetic field (3.0 T) at a TE of 128 msec can provide useful data.

Electrical detection of nuclear spin-echo signals in an electron spin injection system

NASA Astrophysics Data System (ADS)

Lin, Zhichao; Rasly, Mahmoud; Uemura, Tetsuya

2017-06-01

We demonstrated spin echoes of nuclear spins in a spin injection device with a highly polarized spin source by nuclear magnetic resonance (NMR). Efficient spin injection into GaAs from a half-metallic spin source of Co2MnSi enabled efficient dynamic nuclear polarization (DNP) and sensitive detection of NMR signals even at a low magnetic field of ˜0.1 T and a relatively high temperature of 4.2 K. The intrinsic coherence time T2 of 69Ga nuclear spins was evaluated from the spin-echo signals. The relation between T2 and the decay time of the Rabi oscillation suggests that the inhomogeneous effects in our system are not obvious. This study provides an all-electrical NMR system for nuclear-spin-based qubits.

Brain Regional Blood Flow and Working Memory Performance Predict Change in Blood Pressure Over 2 Years.

PubMed

Jennings, J Richard; Heim, Alicia F; Sheu, Lei K; Muldoon, Matthew F; Ryan, Christopher; Gach, H Michael; Schirda, Claudiu; Gianaros, Peter J

2017-12-01

Hypertension is a presumptive risk factor for premature cognitive decline. However, lowering blood pressure (BP) does not uniformly reverse cognitive decline, suggesting that high BP per se may not cause cognitive decline. We hypothesized that essential hypertension has initial effects on the brain that, over time, manifest as cognitive dysfunction in conjunction with both brain vascular abnormalities and systemic BP elevation. Accordingly, we tested whether neuropsychological function and brain blood flow responses to cognitive challenges among prehypertensive individuals would predict subsequent progression of BP. Midlife adults (n=154; mean age, 49; 45% men) with prehypertensive BP underwent neuropsychological testing and assessment of regional cerebral blood flow (rCBF) response to cognitive challenges. Neuropsychological performance measures were derived for verbal and logical memory (memory), executive function, working memory, mental efficiency, and attention. A pseudo-continuous arterial spin labeling magnetic resonance imaging sequence compared rCBF responses with control and active phases of cognitive challenges. Brain areas previously associated with BP were grouped into composites for frontoparietal, frontostriatal, and insular-subcortical rCBF areas. Multiple regression models tested whether BP after 2 years was predicted by initial BP, initial neuropsychological scores, and initial rCBF responses to cognitive challenge. The neuropsychological composite of working memory (standardized beta, -0.276; se=0.116; P =0.02) and the frontostriatal rCBF response to cognitive challenge (standardized beta, 0.234; se=0.108; P =0.03) significantly predicted follow-up BP. Initial BP failed to significantly predict subsequent cognitive performance or rCBF. Changes in brain function may precede or co-occur with progression of BP toward hypertensive levels in midlife. © 2017 American Heart Association, Inc.

Image domain propeller fast spin echo☆

PubMed Central

Skare, Stefan; Holdsworth, Samantha J.; Lilja, Anders; Bammer, Roland

2013-01-01

A new pulse sequence for high-resolution T2-weighted (T2-w) imaging is proposed –image domain propeller fast spin echo (iProp-FSE). Similar to the T2-w PROPELLER sequence, iProp-FSE acquires data in a segmented fashion, as blades that are acquired in multiple TRs. However, the iProp-FSE blades are formed in the image domain instead of in the k-space domain. Each iProp-FSE blade resembles a single-shot fast spin echo (SSFSE) sequence with a very narrow phase-encoding field of view (FOV), after which N rotated blade replicas yield the final full circular FOV. Our method of combining the image domain blade data to a full FOV image is detailed, and optimal choices of phase-encoding FOVs and receiver bandwidths were evaluated on phantom and volunteers. The results suggest that a phase FOV of 15–20%, a receiver bandwidth of ±32–63 kHz and a subsequent readout time of about 300 ms provide a good tradeoff between signal-to-noise ratio (SNR) efficiency and T2 blurring. Comparisons between iProp-FSE, Cartesian FSE and PROPELLER were made on single-slice axial brain data, showing similar T2-w tissue contrast and SNR with great anatomical conspicuity at similar scan times –without colored noise or streaks from motion. A new slice interleaving order is also proposed to improve the multislice capabilities of iProp-FSE. PMID:23200683

MR Imaging with Metal-suppression Sequences for Evaluation of Total Joint Arthroplasty.

PubMed

Talbot, Brett S; Weinberg, Eric P

2016-01-01

Metallic artifact at orthopedic magnetic resonance (MR) imaging continues to be an important problem, particularly in the realm of total joint arthroplasty. Complications often follow total joint arthroplasty and can be expected for a small percentage of all implanted devices. Postoperative complications involve not only osseous structures but also adjacent soft tissues-a highly problematic area at MR imaging because of artifacts from metallic prostheses. Without special considerations, susceptibility artifacts from ferromagnetic implants can unacceptably degrade image quality. Common artifacts include in-plane distortions (signal loss and signal pileup), poor or absent fat suppression, geometric distortion, and through-section distortion. Basic methods to reduce metallic artifacts include use of spin-echo or fast spin-echo sequences with long echo train lengths, short inversion time inversion-recovery (STIR) sequences for fat suppression, a high bandwidth, thin section selection, and an increased matrix. With care and attention to the alloy type (eg, titanium, cobalt-chromium, stainless steel), orientation of the implant, and magnetic field strength, as well as use of proprietary and nonproprietary metal-suppression techniques, previously nondiagnostic studies can yield key diagnostic information. Specifically, sequences such as the metal artifact reduction sequence (MARS), WARP (Siemens Healthcare, Munich, Germany), slice encoding for metal artifact correction (SEMAC), and multiacquisition with variable-resonance image combination (MAVRIC) can be optimized to reveal pathologic conditions previously hidden by periprosthetic artifacts. Complications of total joint arthroplasty that can be evaluated by using MR imaging with metal-suppression sequences include pseudotumoral conditions such as metallosis and particle disease, infection, aseptic prosthesis loosening, tendon injury, and muscle injury. ©RSNA, 2015.

Evaluation of muscle injury using magnetic resonance imaging

NASA Technical Reports Server (NTRS)

LeBlanc, A. D.; Jaweed, M.; Evans, H.

1993-01-01

The objective of this study was to investigate spin echo T2 relaxation time changes in thigh muscles after intense eccentric exercise in healthy men. Spin echo and calculated T2 relaxation time images of the thighs were obtained on several occasions after exercise of one limb; the contralateral limb served as control. Muscle damage was verified by elevated levels of serum creatine kinase (CK). Thirty percent of the time no exercise effect was discernible on the magnetic resonance (MR) images. In all positive MR images (70%) the semitendinosus muscle was positive, while the biceps femoris, short head, and gracilis muscles were also positive in 50% and 25% of the total cases, respectively. The peak T2 relaxation time and serum CK were correlated (r = 0.94, p<0.01); temporal changes in muscle T2 relaxation time and serum CK were similar, although T2 relaxation time remained positive after serum CK returned to background levels. We conclude that magnetic resonance imaging can serve as a useful tool in the evaluation of eccentric exercise muscle damage by providing a quantitative indicator of damage and its resolution as well as the specific areas and muscles.

[Non-contrast time-resolved magnetic resonance angiography combining high resolution multiple phase echo planar imaging based signal targeting and alternating radiofrequency contrast inherent inflow enhanced multi phase angiography combining spatial resolution echo planar imaging based signal targeting and alternating radiofrequency in intracranial arteries].

PubMed

Nakamura, Masanobu; Yoneyama, Masami; Tabuchi, Takashi; Takemura, Atsushi; Obara, Makoto; Sawano, Seishi

2012-01-01

Detailed information on anatomy and hemodynamics in cerebrovascular disorders such as AVM and Moyamoya disease is mandatory for defined diagnosis and treatment planning. Arterial spin labeling technique has come to be applied to magnetic resonance angiography (MRA) and perfusion imaging in recent years. However, those non-contrast techniques are mostly limited to single frame images. Recently we have proposed a non-contrast time-resolved MRA technique termed contrast inherent inflow enhanced multi phase angiography combining spatial resolution echo planar imaging based signal targeting and alternating radiofrequency (CINEMA-STAR). CINEMA-STAR can extract the blood flow in the major intracranial arteries at an interval of 70 ms and thus permits us to observe vascular construction in full by preparing MIP images of axial acquisitions with high spatial resolution. This preliminary study demonstrates the usefulness of the CINEMA-STAR technique in evaluating the cerebral vasculature.

Age-related apparent diffusion coefficient changes in the normal brain.

PubMed

Watanabe, Memi; Sakai, Osamu; Ozonoff, Al; Kussman, Steven; Jara, Hernán

2013-02-01

To measure the mean diffusional age-related changes of the brain over the full human life span by using diffusion-weighted spin-echo single-shot echo-planar magnetic resonance (MR) imaging and sequential whole-brain apparent diffusion coefficient (ADC) histogram analysis and, secondarily, to build mathematical models of these normal age-related changes throughout human life. After obtaining institutional review board approval, a HIPAA-compliant retrospective search was conducted for brain MR imaging studies performed in 2007 for various clinical indications. Informed consent was waived. The brain data of 414 healthy subjects (189 males and 225 females; mean age, 33.7 years; age range, 2 days to 89.3 years) were obtained with diffusion-weighted spin-echo single-shot echo-planar MR imaging. ADC histograms of the whole brain were generated. ADC peak values, histogram widths, and intracranial volumes were plotted against age, and model parameters were estimated by using nonlinear regression. Four different stages were identified for aging changes in ADC peak values, as characterized by specific mathematical terms: There were age-associated exponential decays for the maturation period and the development period, a constant term for adulthood, and a linear increase for the senescence period. The age dependency of ADC peak value was simulated by using four-term six-coefficient function, including biexponential and linear terms. This model fit the data very closely (R(2) = 0.91). Brain diffusivity as a whole demonstrated age-related changes through four distinct periods of life. These results could contribute to establishing an ADC baseline of the normal brain, covering the full human life span.

BLIPPED (BLIpped Pure Phase EncoDing) high resolution MRI with low amplitude gradients

NASA Astrophysics Data System (ADS)

Xiao, Dan; Balcom, Bruce J.

2017-12-01

MRI image resolution is proportional to the maximum k-space value, i.e. the temporal integral of the magnetic field gradient. High resolution imaging usually requires high gradient amplitudes and/or long spatial encoding times. Special gradient hardware is often required for high amplitudes and fast switching. We propose a high resolution imaging sequence that employs low amplitude gradients. This method was inspired by the previously proposed PEPI (π Echo Planar Imaging) sequence, which replaced EPI gradient reversals with multiple RF refocusing pulses. It has been shown that when the refocusing RF pulse is of high quality, i.e. sufficiently close to 180°, the magnetization phase introduced by the spatial encoding magnetic field gradient can be preserved and transferred to the following echo signal without phase rewinding. This phase encoding scheme requires blipped gradients that are identical for each echo, with low and constant amplitude, providing opportunities for high resolution imaging. We now extend the sequence to 3D pure phase encoding with low amplitude gradients. The method is compared with the Hybrid-SESPI (Spin Echo Single Point Imaging) technique to demonstrate the advantages in terms of low gradient duty cycle, compensation of concomitant magnetic field effects and minimal echo spacing, which lead to superior image quality and high resolution. The 3D imaging method was then applied with a parallel plate resonator RF probe, achieving a nominal spatial resolution of 17 μm in one dimension in the 3D image, requiring a maximum gradient amplitude of only 5.8 Gauss/cm.

[Carotid plaque assessment using inversion recovery T1 weighted-3 dimensions variable refocus flip angle turbo spin echo sampling perfection with application optimized contrast using different angle evolutions black blood imaging].

PubMed

Inoue, Yuji; Yoneyama, Masami; Nakamura, Masanobu; Ozaki, Satoshi; Ito, Kenjiro; Hiura, Mikio

2012-01-01

Vulnerable plaque can be attributed to induction of ischemic symptoms and magnetic resonance imaging of carotid artery is valuable to detect the plaque. Magnetization prepared rapid acquisition with gradient echo (MPRAGE) method could detect hemorrhagic vulnerable plaque as high intensity signal; however, blood flow is not sufficiently masked by this method. The contrast for plaque in T1 weighted image (T1WI) could not be obtained sufficiently with black blood image (BBI) by sampling perfection with application optimized contrast using different angle evolutions (SPACE) method as turbo spin echo (TSE). In addition, an appearance of artifact by slow flow is a problem. Considering these controversial situations in plaque imaging, we examined the modified BBI inversion recovery (IR)-SPACE in which IR was added for SPACE method so that the contrast for plaque in T1WI was optimized. We investigated the application of this method in plaque imaging. As a result of phantom imaging, the contrast for plaque in T1WI was definitely obtained by choosing an appropriate inversion time (TI) for the corresponding repetition time. In clinical cases, blood flow was sufficiently masked by IR-SPACE method and the plaque imaging was clearly obtained in clinical cases to the same extent as MPRAGE method. Since BBI with IR-SPACE method was derived from both IR pulse and flow void effect, this method could obtain the blood flow masking effect definitely. The present study suggested that SPACE method might be applicable to estimate properties of carotid artery plaque.

TU-H-CAMPUS-IeP2-01: Quantitative Evaluation of PROPELLER DWI Using QIBA Diffusion Phantom

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yung, J; Ai, H; Liu, H

Purpose: The purpose of this study is to determine the quantitative variability of apparent diffusion coefficient (ADC) values when varying imaging parameters in a diffusion-weighted (DW) fast spin echo (FSE) sequence with Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction (PROPELLER) k-space trajectory. Methods: Using a 3T MRI scanner, a NIST traceable, quantitative magnetic resonance imaging (MRI) diffusion phantom (High Precision Devices, Inc, Boulder, Colorado) consisting of 13 vials filled with various concentrations of polymer polyvinylpyrrolidone (PVP) in aqueous solution was imaged with a standard Quantitative Imaging Biomarkers Alliance (QIBA) DWI spin echo, echo planar imaging (SE EPI) acquisition. Themore » same phantom was then imaged with a DWI PROPELLER sequence at varying echo train lengths (ETL) of 8, 20, and 32, as well as b-values of 400, 900, and 2000. QIBA DWI phantom analysis software was used to generate ADC maps and create region of interests (ROIs) for quantitative measurements of each vial. Mean and standard deviations of the ROIs were compared. Results: The SE EPI sequence generated ADC values that showed very good agreement with the known ADC values of the phantom (r2 = 0.9995, slope = 1.0061). The ADC values measured from the PROPELLER sequences were inflated, but were highly correlated with an r2 range from 0.8754 to 0.9880. The PROPELLER sequence with an ETL=20 and b-value of 0 and 2000 showed the closest agreement (r2 = 0.9034, slope = 0.9880). Conclusion: The DW PROPELLER sequence is promising for quantitative evaluation of ADC values. A drawback of the PROPELLER sequence is the longer acquisition time. The 180° refocusing pulses may also cause the observed increase in ADC values compared to the standard SE EPI DW sequence. However, the FSE sequence offers an advantage with in-plane motion and geometric distortion which will be investigated in future studies.« less

Imaging of pediatric great vessel stents: Computed tomography or magnetic resonance imaging?

PubMed Central

van Hamersvelt, R. W.; Budde, R. P. J.; de Jong, P. A.; Schilham, A. M. R.; Bos, C.; Breur, J. M. P. J.; Leiner, T.

2017-01-01

Background Complications might occur after great vessel stent implantation in children. Therefore follow-up using imaging is warranted. Purpose To determine the optimal imaging modality for the assessment of stents used to treat great vessel obstructions in children. Material and methods Five different large vessel stents were evaluated in an in-vitro setting. All stents were expanded to the maximal vendor recommended diameter (20mm; n = 4 or 10mm; n = 1), placed in an anthropomorphic chest phantom and imaged with a 256-slice CT-scanner. MRI images were acquired at 1.5T using a multi-slice T2-weighted turbo spin echo, an RF-spoiled three-dimensional T1-weighted Fast Field Echo and a balanced turbo field echo 3D sequence. Two blinded observers assessed stent lumen visibility (measured diameter/true diameter *100%) in the center and at the outlets of the stent. Reproducibility of diameter measurements was evaluated using the intraclass correlation coefficient for reliability and 95% limits of agreement for agreement analysis. Results Median stent lumen visibility was 88 (IQR 86–90)% with CT for all stents at both the center and outlets. With MRI, the T2-weighted turbo spin echo sequence was preferred which resulted in 82 (78–84%) stent lumen visibility. Interobserver reliability and agreement was good for both CT (ICC 0.997, mean difference -0.51 [-1.07–0.05] mm) and MRI measurements (ICC 0.951, mean difference -0.05 [-2.52 –-2.41] mm). Conclusion Good in-stent lumen visibility was achievable in this in-vitro study with both CT and MRI in different great vessel stents. Overall reliability was good with clinical acceptable limits of agreement for both CT and MRI. However, common conditions such as in-stent stenosis and associated aneurysms were not tested in this in-vitro study, limiting the value of the in-vitro study. PMID:28141852

Imaging of pediatric great vessel stents: Computed tomography or magnetic resonance imaging?

PubMed

den Harder, A M; Suchá, D; van Hamersvelt, R W; Budde, R P J; de Jong, P A; Schilham, A M R; Bos, C; Breur, J M P J; Leiner, T

2017-01-01

Complications might occur after great vessel stent implantation in children. Therefore follow-up using imaging is warranted. To determine the optimal imaging modality for the assessment of stents used to treat great vessel obstructions in children. Five different large vessel stents were evaluated in an in-vitro setting. All stents were expanded to the maximal vendor recommended diameter (20mm; n = 4 or 10mm; n = 1), placed in an anthropomorphic chest phantom and imaged with a 256-slice CT-scanner. MRI images were acquired at 1.5T using a multi-slice T2-weighted turbo spin echo, an RF-spoiled three-dimensional T1-weighted Fast Field Echo and a balanced turbo field echo 3D sequence. Two blinded observers assessed stent lumen visibility (measured diameter/true diameter *100%) in the center and at the outlets of the stent. Reproducibility of diameter measurements was evaluated using the intraclass correlation coefficient for reliability and 95% limits of agreement for agreement analysis. Median stent lumen visibility was 88 (IQR 86-90)% with CT for all stents at both the center and outlets. With MRI, the T2-weighted turbo spin echo sequence was preferred which resulted in 82 (78-84%) stent lumen visibility. Interobserver reliability and agreement was good for both CT (ICC 0.997, mean difference -0.51 [-1.07-0.05] mm) and MRI measurements (ICC 0.951, mean difference -0.05 [-2.52 --2.41] mm). Good in-stent lumen visibility was achievable in this in-vitro study with both CT and MRI in different great vessel stents. Overall reliability was good with clinical acceptable limits of agreement for both CT and MRI. However, common conditions such as in-stent stenosis and associated aneurysms were not tested in this in-vitro study, limiting the value of the in-vitro study.

Oscillating and pulsed gradient diffusion magnetic resonance microscopy over an extended b-value range: implications for the characterization of tissue microstructure.

PubMed

Portnoy, S; Flint, J J; Blackband, S J; Stanisz, G J

2013-04-01

Oscillating gradient spin-echo (OGSE) pulse sequences have been proposed for acquiring diffusion data with very short diffusion times, which probe tissue structure at the subcellular scale. OGSE sequences are an alternative to pulsed gradient spin echo measurements, which typically probe longer diffusion times due to gradient limitations. In this investigation, a high-strength (6600 G/cm) gradient designed for small-sample microscopy was used to acquire OGSE and pulsed gradient spin echo data in a rat hippocampal specimen at microscopic resolution. Measurements covered a broad range of diffusion times (TDeff = 1.2-15.0 ms), frequencies (ω = 67-1000 Hz), and b-values (b = 0-3.2 ms/μm2). Variations in apparent diffusion coefficient with frequency and diffusion time provided microstructural information at a scale much smaller than the imaging resolution. For a more direct comparison of the techniques, OGSE and pulsed gradient spin echo data were acquired with similar effective diffusion times. Measurements with similar TDeff were consistent at low b-value (b < 1 ms/μm(2) ), but diverged at higher b-values. Experimental observations suggest that the effective diffusion time can be helpful in the interpretation of low b-value OGSE data. However, caution is required at higher b, where enhanced sensitivity to restriction and exchange render the effective diffusion time an unsuitable representation. Oscillating and pulsed gradient diffusion techniques offer unique, complementary information. In combination, the two methods provide a powerful tool for characterizing complex diffusion within biological tissues. Copyright © 2012 Wiley Periodicals, Inc.

Measurement of the ferric diffusion coefficient in agarose and gelatine gels by utilization of the evolution of a radiation induced edge as reflected in relaxation rate images.

PubMed

Pedersen, T V; Olsen, D R; Skretting, A

1997-08-01

A method has been developed to determine the diffusion coefficients of ferric ions in ferrous sulphate doped gels. A radiation induced edge was created in the gel, and two spin-echo sequences were used to acquire a pair of images of the gel at different points of time. For each of these image pairs, a longitudinal relaxation rate image was derived. From profiles through these images, the standard deviations of the Gaussian functions that characterize diffusion were determined. These data provided the basis for the determination of the ferric diffusion coefficients by two different methods. Simulations indicate that the use of single spin-echo images in this procedure may in some cases lead to a significant underestimation of the diffusion coefficient. The technique was applied to different agarose and gelatine gels that were prepared, irradiated and imaged simultaneously. The results indicate that the diffusion coefficient is lower in a gelatine gel than in an agarose gel. Addition of xylenol orange to a gelatine gel lowers the diffusion coefficient from 1.45 to 0.81 mm2 h-1, at the cost of significantly lower Rl sensitivity. The addition of benzoic acid to the latter gel did not increase the Rl sensitivity.

Echo-Planar Imaging: Magnetic Resonance Imaging in a Fraction of a Second

NASA Astrophysics Data System (ADS)

Stehling, Michael K.; Turner, Robert; Mansfield, Peter

1991-10-01

Progress has recently been made in implementing magnetic resonance imaging (MRI) techniques that can be used to obtain images in a fraction of a second rather than in minutes. Echo-planar imaging (EPI) uses only one nuclear spin excitation per image and lends itself to a variety of critical medical and scientific applications. Among these are evaluation of cardiac function in real time, mapping of water diffusion and temperature in tissue, mapping of organ blood pool and perfusion, functional imaging of the central nervous system, depiction of blood and cerebrospinal fluid flow dynamics, and movie imaging of the mobile fetus in utero. Through shortened patient examination times, higher patient throughput, and lower cost per MRI examination, EPI may become a powerful tool for early diagnosis of some common and potentially treatable diseases such as ischemic heart disease, stroke, and cancer.

Articular cartilage grading of the knee: diagnostic performance of fat-suppressed 3D volume isotropic turbo spin-echo acquisition (VISTA) compared with 3D T1 high-resolution isovolumetric examination (THRIVE).

PubMed

Lee, Young Han; Hahn, Seok; Lim, Daekeon; Suh, Jin-Suck

2017-02-01

Background Conventionally, two-dimensional (2D) fast spin-echo (FSE) sequences have been widely used for clinical cartilage imaging as well as gradient (GRE) sequences. Recently, three-dimensional (3D) volumetric magnetic resonance imaging (MRI) has been introduced with one 3D volumetric scan, and this is replacing slice-by-slice 2D MR scans. Purpose To evaluate the image quality and diagnostic performance of two 3D sequences for abnormalities of knee cartilage: fat-suppressed (FS) FSE-based 3D volume isotropic turbo spin-echo acquisition (VISTA) and GRE-based 3D T1 high-resolution isovolumetric examination (THRIVE). Material and Methods The institutional review board approved the protocol of this retrospective review. This study enrolled 40 patients (41 knees) with arthroscopically confirmed abnormalities of cartilage. All patients underwent isovoxel 3D-VISTA and 3D-THRIVE MR sequences on 3T MRI. We assessed the cartilage grade on the two 3D sequences using arthroscopy as a gold standard. Inter-observer agreement for each technique was evaluated with the intraclass correlation coefficient (ICC). Differences in the area under the curve (AUC) were compared between the 3D-THRIVE and 3D-VISTA. Results Although inter-observer agreement for both sequences was excellent, the inter-observer agreement for 3D-VISTA was higher than for 3D-THRIVE for cartilage grading in all regions of the knee. There was no significant difference in the diagnostic performance ( P > 0.05) between the two sequences for detecting cartilage grade. Conclusion FSE-based 3D-VISTA images had good diagnostic performance that was comparable to GRE-based 3D-THRIVE images in the evaluation of knee cartilage, and can be used in routine knee MR protocols for the evaluation of cartilage.

Ultrafast MR imaging of the pelvic floor.

PubMed

Unterweger, M; Marincek, B; Gottstein-Aalame, N; Debatin, J F; Seifert, B; Ochsenbein-Imhof, N; Perucchini, D; Kubik-Huch, R A

2001-04-01

The aim of this study was to compare pelvic floor anatomy and laxity at rest and on straining (Valsalva's maneuver) using dynamic ultrafast MR imaging in women who were continent versus those with stress incontinence differing in obstetric history. Thirty continent women were divided into three equal groups (nulliparous, previous cesarean delivery, previous vaginal delivery) and compared with 10 women with stress-incontinence with a history of at least one vaginal delivery. MR imaging of the pelvic floor at rest and on maximal strain was performed, using axial T2-weighted fast spin-echo images followed by sagittal ultrafast T2-weighted single-shot fast spin-echo sequences. Mean population age (age range, 22-45 years; mean +/- SD, 36 +/- 5.4 years), was similar in the four groups, as was parity in the three parous groups. Mean distances between the bladder floor and pubococcygeal line at rest did not differ between the four groups. On straining, bladder floor descent was 1.1 +/- 0.9, 1.0 +/- 1.1, and 1.9 +/- 0.9 cm in continent nulliparous, cesarean delivery, and vaginal delivery women, respectively, versus 3.2 +/- 1.0 cm in incontinent women (p = 0.0005). Cervical descent was greater in incontinent versus nulliparous women (p = 0.0019). Bladder floor descent was greater in the continent vaginal delivery group than in continent cesarean delivery control patients (p = 0.04). In patients with stress incontinence, symptoms did not correlate with amplitude of descent. The right levator muscle was thinner overall than the left, regardless of frequency direction (p = 0.001). Ultrafast MR imaging using the T2-weighted single-shot fast spin-echo sequence allows dynamic evaluation of the pelvic compartments at maximal strain with no need for contrast medium. Pelvic floor laxity and supporting fascia abnormalities were most common in patients with stress incontinence followed by continent women with a history of vaginal delivery. The results are therefore compatible with the hypothesis of vaginal delivery as a contributory factor to stress incontinence in older parous women.

Evaluation of thermometric monitoring for intradiscal laser ablation in an open 1.0 T MR scanner.

PubMed

Wonneberger, Uta; Schnackenburg, Bernhard; Wlodarczyk, Waldemar; Rump, Jens; Walter, Thula; Streitparth, Florian; Teichgräber, Ulf Karl Mart

2010-01-01

The purpose of this study was to evaluate different methods of magnetic resonance thermometry (MRTh) for the monitoring of intradiscal laser ablation therapy in an open 1.0 Tesla magnetic resonance (MR) scanner. MRTh methods based on the two endogenous MR temperature indicators of spin-lattice relaxation time T1 and water proton resonance frequency (PRF) shift were optimised and compared in vitro. For the latter, we measured the effective spin-spin relaxation times T2* in intervertebral discs of volunteers. Then we compared four gradient echo-based imaging techniques to monitor laser ablations in human disc specimens. Criteria of assessment were outline of anatomic detail, immunity against needle artefacts, signal-to-noise ratio (SNR) and accuracy of the calculated temperature. T2* decreased in an inverse and almost linear manner with the patients' age (r = 0.9) from 70 to 30 ms (mean of 49 ms). The optimum image quality (anatomic details, needle artefacts, SNR) and temperature accuracy (+/-1.09 degrees C for T1-based and +/-1.11 degrees C for PRF-based MRTh) was achieved with a non-spoiled gradient-echo sequence with an echo time of TE = 10 ms. Combination of anatomic and thermometric non-invasive monitoring of laser ablations in the lumbar spine is feasible. The temperature accuracy of the investigated T1- and PRF-based MRTh methods in vitro is high enough and promises to be reliable in vivo as well.

Intraoperative cerebral blood flow imaging of rodents

NASA Astrophysics Data System (ADS)

Li, Hangdao; Li, Yao; Yuan, Lu; Wu, Caihong; Lu, Hongyang; Tong, Shanbao

2014-09-01

Intraoperative monitoring of cerebral blood flow (CBF) is of interest to neuroscience researchers, which offers the assessment of hemodynamic responses throughout the process of neurosurgery and provides an early biomarker for surgical guidance. However, intraoperative CBF imaging has been challenging due to animal's motion and position change during the surgery. In this paper, we presented a design of an operation bench integrated with laser speckle contrast imager which enables monitoring of the CBF intraoperatively. With a specially designed stereotaxic frame and imager, we were able to monitor the CBF changes in both hemispheres during the rodent surgery. The rotatable design of the operation plate and implementation of online image registration allow the technician to move the animal without disturbing the CBF imaging during surgery. The performance of the system was tested by middle cerebral artery occlusion model of rats.

Apparent CBF decrease with normal aging due to partial volume effects: MR-based partial volume correction on CBF SPECT.

PubMed

Inoue, Kentaro; Ito, Hiroshi; Goto, Ryoi; Nakagawa, Manabu; Kinomura, Shigeo; Sato, Tachio; Sato, Kazunori; Fukuda, Hiroshi

2005-06-01

Several studies using single photon emission tomography (SPECT) have shown changes in cerebral blood flow (CBF) with age, which were associated with partial volume effects by some authors. Some studies have also demonstrated gender-related differences in CBF. The present study aimed to examine age and gender effects on CBF SPECT images obtained using the 99mTc-ethyl cysteinate dimer and a SPECT scanner, before and after partial volume correction (PVC) using magnetic resonance (MR) imaging. Forty-four healthy subjects (29 males and 15 females; age range, 27-64 y; mean age, 50.0 +/- 9.8 y) participated. Each MR image was segmented to yield grey and white matter images and coregistered to a corresponding SPECT image, followed by convolution to approximate the SPECT spatial resolution. PVC-SPECT images were produced using the convoluted grey matter MR (GM-MR) and white matter MR images. The age and gender effects were assessed using SPM99. Decreases with age were detected in the anterolateral prefrontal cortex and in areas along the lateral sulcus and the lateral ventricle, bilaterally, in the GM-MR images and the SPECT images. In the PVC-SPECT images, decreases in CBF in the lateral prefrontal cortex lost their statistical significance. Decreases in CBF with age found along the lateral sulcus and the lateral ventricle, on the other hand, remained statistically significant, but observation of the spatially normalized MR images suggests that these findings are associated with the dilatation of the lateral sulcus and lateral ventricle, which was not completely compensated for by the spatial normalization procedure. Our present study demonstrated that age effects on CBF in healthy subjects could reflect morphological differences with age in grey matter.

GRE T2∗-Weighted MRI: Principles and Clinical Applications

PubMed Central

Tang, Meng Yue; Chen, Tian Wu; Zhang, Xiao Ming; Huang, Xiao Hua

2014-01-01

The sequence of a multiecho gradient recalled echo (GRE) T2*-weighted imaging (T2*WI) is a relatively new magnetic resonance imaging (MRI) technique. In contrast to T2 relaxation, which acquires a spin echo signal, T2* relaxation acquires a gradient echo signal. The sequence of a GRE T2*WI requires high uniformity of the magnetic field. GRE T2*WI can detect the smallest changes in uniformity in the magnetic field and can improve the rate of small lesion detection. In addition, the T2* value can indirectly reflect changes in tissue biochemical components. Moreover, it can be used for the early diagnosis and quantitative diagnosis of some diseases. This paper reviews the principles and clinical applications as well as the advantages and disadvantages of GRE T2*WI. PMID:24987676

Effects of resting state condition on reliability, trait specificity, and network connectivity of brain function measured with arterial spin labeled perfusion MRI.

PubMed

Li, Zhengjun; Vidorreta, Marta; Katchmar, Natalie; Alsop, David C; Wolf, Daniel H; Detre, John A

2018-06-01

Resting state fMRI (rs-fMRI) provides imaging biomarkers of task-independent brain function that can be associated with clinical variables or modulated by interventions such as behavioral training or pharmacological manipulations. These biomarkers include time-averaged regional brain function as manifested by regional cerebral blood flow (CBF) measured using arterial spin labeled (ASL) perfusion MRI and correlated temporal fluctuations of function across brain networks with either ASL or blood oxygenation level dependent (BOLD) fMRI. Resting-state studies are typically carried out using just one of several prescribed state conditions such as eyes closed (EC), eyes open (EO), or visual fixation on a cross-hair (FIX), which may affect the reliability and specificity of rs-fMRI. In this study, we collected test-retest ASL MRI data during 4 resting-state task conditions: EC, EO, FIX and PVT (low-frequency psychomotor vigilance task), and examined the effects of these task conditions on reliability and reproducibility as well as trait specificity of regional brain function. We also acquired resting-state BOLD fMRI under FIX and compared the network connectivity reliabilities between the four ASL conditions and the BOLD FIX condition. For resting-state ASL data, EC provided the highest CBF reliability, reproducibility, trait specificity, and network connectivity reliability, followed by EO, while FIX was lowest on all of these measures. PVT demonstrated lower CBF reliability, reproducibility and trait specificity than EO and EC. Overall network connectivity reliability was comparable between ASL and BOLD. Our findings confirm ASL CBF as a reliable, stable, and consistent measure of resting-state regional brain function and support the use of EC or EO over FIX and PVT as the resting-state condition. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Effect of disease progression on liver apparent diffusion coefficient and T2 values in a murine model of hepatic fibrosis at 11.7 Tesla MRI.

PubMed

Anderson, Stephan W; Jara, Hernan; Ozonoff, Al; O'Brien, Michael; Hamilton, James A; Soto, Jorge A

2012-01-01

To evaluate the effects of hepatic fibrosis on ADC and T(2) values of ex vivo murine liver specimens imaged using 11.7 Tesla (T) MRI. This animal study was IACUC approved. Seventeen male, C57BL/6 mice were divided into control (n = 2) and experimental groups (n = 15), the latter fed a 3, 5-dicarbethoxy-1, 4-dihydrocollidine (DDC) supplemented diet, inducing hepatic fibrosis. Ex vivo liver specimens were imaged using an 11.7T MRI scanner. Spin-echo pulsed field gradient and multi-echo spin-echo acquisitions were used to generate parametric ADC and T(2) maps, respectively. Degrees of fibrosis were determined by the evaluation of a pathologist as well as digital image analysis. Scatterplot graphs comparing ADC and T(2) to degrees of fibrosis were generated and correlation coefficients were calculated. Strong correlation was found between degrees of hepatic fibrosis and ADC with higher degrees of fibrosis associated with lower hepatic ADC values. Moderate correlation between hepatic fibrosis and T(2) values was seen with higher degrees of fibrosis associated with lower T(2) values. Inverse relationships between degrees of fibrosis and both ADC and T(2) are seen, highlighting the utility of these parameters in the ongoing development of an MRI methodology to quantify hepatic fibrosis. Copyright © 2011 Wiley Periodicals, Inc.

Volumetric Arterial Spin-labeled Perfusion Imaging of the Kidneys with a Three-dimensional Fast Spin Echo Acquisition.

PubMed

Robson, Philip M; Madhuranthakam, Ananth J; Smith, Martin P; Sun, Maryellen R M; Dai, Weiying; Rofsky, Neil M; Pedrosa, Ivan; Alsop, David C

2016-02-01

Renal perfusion measurements using noninvasive arterial spin-labeled (ASL) magnetic resonance imaging techniques are gaining interest. Currently, focus has been on perfusion in the context of renal transplant. Our objectives were to explore the use of ASL in patients with renal cancer, and to evaluate three-dimensional (3D) fast spin echo (FSE) acquisition, a robust volumetric imaging method for abdominal applications. We evaluate 3D ASL perfusion magnetic resonance imaging in the kidneys compared to two-dimensional (2D) ASL in patients and healthy subjects. Isotropic resolution (2.6 × 2.6 × 2.8 mm(3)) 3D ASL using segmented FSE was compared to 2D single-shot FSE. ASL used pseudo-continuous labeling, suppression of background signal, and synchronized breathing. Quantitative perfusion values and signal-to-noise ratio (SNR) were compared between 3D and 2D ASL in four healthy volunteers and semiquantitative assessments were made by four radiologists in four patients with known renal masses (primary renal cell carcinoma). Renal cortex perfusion in healthy subjects was 284 ± 21 mL/100 g/min, with test-retest repeatability of 8.8%. No significant differences were found between the quantitative perfusion value and SNR in volunteers between 3D ASL and 2D ASL, or in 3D ASL with synchronized or free breathing. In patients, semiquantitative assessment by radiologists showed no significant difference in image quality between 2D ASL and 3D ASL. In one case, 2D ASL missed a high perfusion focus in a mass that was seen by 3D ASL. 3D ASL renal perfusion imaging provides isotropic-resolution images, with comparable quantitative perfusion values and image SNR in similar imaging time to single-slice 2D ASL. Copyright © 2015 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.

Simultaneous pH-sensitive and oxygen-sensitive MRI of human gliomas at 3 T using multi-echo amine proton chemical exchange saturation transfer spin-and-gradient echo echo-planar imaging (CEST-SAGE-EPI).

PubMed

Harris, Robert J; Yao, Jingwen; Chakhoyan, Ararat; Raymond, Catalina; Leu, Kevin; Liau, Linda M; Nghiemphu, Phioanh L; Lai, Albert; Salamon, Noriko; Pope, Whitney B; Cloughesy, Timothy F; Ellingson, Benjamin M

2018-04-06

To introduce a new pH-sensitive and oxygen-sensitive MRI technique using amine proton CEST echo spin-and-gradient echo (SAGE) EPI (CEST-SAGE-EPI). pH-weighting was obtained using CEST estimations of magnetization transfer ratio asymmetry (MTR asym ) at 3 ppm, and oxygen-weighting was obtained using R2' measurements. Glutamine concentration, pH, and relaxation rates were varied in phantoms to validate simulations and estimate relaxation rates. The values of MTR asym and R2' in normal-appearing white matter, T 2 hyperintensity, contrast enhancement, and macroscopic necrosis were measured in 47 gliomas. Simulation and phantom results confirmed an increase in MTR asym with decreasing pH. The CEST-SAGE-EPI estimates of R 2 , R2*, and R2' varied linearly with gadolinium diethylenetriamine penta-acetic acid concentration (R 2  = 6.2 mM -1 ·sec -1 and R2* = 6.9 mM -1 ·sec -1 ). The CEST-SAGE-EPI and Carr-Purcell-Meiboom-Gill estimates of R 2 (R 2  = 0.9943) and multi-echo gradient-echo estimates of R2* (R 2  = 0.9727) were highly correlated. T 2 lesions had lower R2' and higher MTR asym compared with normal-appearing white matter, suggesting lower hypoxia and high acidity, whereas contrast-enhancement tumor regions had elevated R2' and MTR asym , indicating high hypoxia and acidity. The CEST-SAGE-EPI technique provides simultaneous pH-sensitive and oxygen-sensitive image contrasts for evaluation of the brain tumor microenvironment. Advantages include fast whole-brain acquisition, in-line B 0 correction, and simultaneous estimation of CEST effects, R 2 , R2*, and R2' at 3 T. © 2018 International Society for Magnetic Resonance in Medicine.

Effects of a brief cognitive behavioural therapy group intervention on baseline brain perfusion in adolescents with major depressive disorder.

PubMed

Sosic-Vasic, Zrinka; Abler, Birgit; Grön, Georg; Plener, Paul; Straub, Joana

2017-04-12

A number of neuroimaging studies have identified altered regional cerebral blood flow (rCBF) related to major depressive disorder (MDD) in adult samples, particularly in the lateral prefrontal, cingular and temporal regions. In contrast, neuroimaging investigations in adolescents with MDD are rare, although investigating young patients during a significant period of brain maturation might offer valuable insights into the neural mechanisms of MDD. We acquired perfusion images obtained with continuous arterial spin labelling in 21 medication-naive adolescents with MDD before and after a five-session cognitive behavioural group therapy (group CBT). A control group included medication-naive patients under treatment as usual while waiting for the psychotherapy. We found relatively increased rCBF in the right dorsolateral prefrontal cortex (DLPFC; BA 46), the right caudate nucleus and the left inferior parietal lobe (BA 40) after CBT compared with before CBT. Relatively increased rCBF in the right DLPFC postgroup CBT was confirmed by time (post vs. pre)×group (intervention/waiting list) interaction analyses. In the waiting group, relatively increased rCBF was found in the thalamus and the anterior cingulate cortex (BA 24). The relatively small number of patients included in this pilot study has to be considered. Our findings indicate that noninvasive resting perfusion scanning is suitable to identify CBT-related changes in adolescents with MDD. rCBF increase in the DLPFC following a significant reduction in MDD symptoms in adolescents might represent the core neural correlate of changes in 'top-down' cognitive processing, a possible correlate of improved self-regulation and cognitive control.

Neurocardiac protection with milrinone for restoring acute cerebral hypoperfusion and delayed ischemic injury after experimental subarachnoid hemorrhage.

PubMed

Mutoh, Tomoko; Mutoh, Tatsushi; Sasaki, Kazumasu; Nakamura, Kazuhiro; Tatewaki, Yasuko; Ishikawa, Tatsuya; Taki, Yasuyuki

2017-02-15

Acute cerebral hypoperfusion following subarachnoid hemorrhage (SAH) is highly related to the pathogenesis of delayed cerebral ischemia (DCI), but the therapeutic option is poorly available. This study aimed to clarify the effect of milrinone (MIL) on cerebral blood flow (CBF) and related outcomes after experimental SAH. Twenty-seven male C57BL/6 mice were assigned to either sham surgery (SAH-sham; n=6), SAH induced by endovascular perforation (control; n=10), or SAH followed by cardiac support with intravenous MIL (n=11) performed 1.5-h after SAH induction. CBF, neurobehavioral function, occurrence of DCI were assessed by MR-continuous arterial spin labeling, daily neurological score testing, and diffusion- and T2-weighted MR images on days 1 and 3, respectively. Initial global CBF depression was notable in mice of control and MIL groups as compared to the SAH-sham group (P<0.05). MIL raised CBF in a dose-dependent manner (P<0.001), resulted in lower incidence of DCI (P=0.008) and better recovery from neurobehavioral decline than control (P<0.001). The CBF values on day 1 predicted DCI with a cut-off of 42.5ml/100g/min (82% specificity and 83% sensitivity), which was greater in mice treated with MIL than those of control (51.7 versus 37.6ml/100g/min; P<0.001). MIL improves post-SAH acute hypoperfusion that can lead to the prevention of DCI and functional worsening, acting as a neurocardiac protective agent against EBI. Copyright © 2017 Elsevier B.V. All rights reserved.

Diffusion-weighted imaging of the spine with a non-carr-purcell-meiboom-gill single-shot fast spin-echo sequence: initial experience.

PubMed

Oner, A Y; Tali, T; Celikyay, F; Celik, A; Le Roux, P

2007-03-01

To prospectively evaluate the signal-to-noise ratio (SNR) improvement in diffusion-weighted imaging (DWI) of the spine with the use of a newly developed non-Carr-Purcell-Meiboom-Gill (non-CPMG) single-shot fast spin-echo (SS-FSE) sequence and its effect on apparent diffusion coefficient (ADC) measurements. Twenty-four patients were enrolled after written informed consent. DWI of the spine was obtained with an echo-planar imaging (EPI)-based sequence followed by a non-CPMG SS-FSE technique. SNR and ADC values were measured over a lesion-free vertebral corpus. A quality score was assigned for each set of images to assess the image quality. When a spinal lesion was present, contrast-to-noise ratio (CNR) and ADC were also measured. Student t tests were used for statistical analysis. Mean SNR values were 5.83 +/- 2.2 and 11.68 +/- 2.87 for EPI and non-CPMG SS-FSE DWI, respectively. SNR values measured in DWI using parallel imaging were found to be significantly higher (P < .01). Mean ADCs of the spine were 0.53 +/- 0.15 and 0.35 +/- 0.15 x 10(-3) mm(2)/s for EPI and non-CPMG SS-FSE DWI, respectively. Quality scores were found to be higher for the non-CPMG SS-FSE DWI technique (P < .05). Overall lesion CNR was found to be higher in DWI with non-CPMG SS-FSE. The non-CPMG SS-FSE technique provides a significant improvement to current EPI-based DWI of the spine. A study including a larger number of patients is required to determine the use of this DWI sequence as a supplementary tool to conventional MR imaging for increasing diagnostic confidence in spinal pathologic conditions.

Does non-echo-planar diffusion-weighted magnetic resonance imaging have a role in assisting the clinical diagnosis of cholesteatoma in selected cases?

PubMed

Nash, R; Lingam, R K; Chandrasekharan, D; Singh, A

2018-03-01

To determine the diagnostic performance of diffusion-weighted magnetic resonance imaging in the assessment of patients with suspected, but not clinically evident, cholesteatoma. A retrospective analysis of a prospectively collected database of non-echo-planar diffusion-weighted magnetic resonance imaging studies (using a half-Fourier single-shot turbo-spin echo sequence) was conducted. Clinical records were retrospectively reviewed to determine indications for imaging and operative findings. Seventy-eight investigations in 74 patients with suspected cholesteatoma aged 5.7-79.2 years (mean, 41.7 years) were identified. Operative confirmation was available in 44 ears. Diagnostic accuracy of the imaging technique was calculated using operative findings as a 'gold standard'. Sensitivity of the investigation was examined via comparison with clinically evident cholesteatoma. The accuracy of diffusion-weighted magnetic resonance imaging in assessment of suspected cholesteatoma was 63.6 per cent. The imaging technique was significantly less accurate in assessment of suspected cholesteatoma than clinically evident disease (p < 0.001). Computed tomography and diffusion-weighted magnetic resonance imaging may be complementary in assessment of suspected cholesteatoma, but should be used with caution, and clinical judgement is paramount.

Basal Hippocampal Activity and Its Functional Connectivity Predicts Cocaine Relapse

PubMed Central

Adinoff, Bryon; Gu, Hong; Merrick, Carmen; McHugh, Meredith; Jeon-Slaughter, Haekyung; Lu, Hanzhang; Yang, Yihong; Stein, Elliot A.

2017-01-01

BACKGROUND Cocaine-induced neuroplastic changes may result in a heightened propensity for relapse. Using regional cerebral blood flow (rCBF) as a marker of basal neuronal activity, this study assessed alterations in rCBF and related resting state functional connectivity (rsFC) to prospectively predict relapse in patients following treatment for cocaine use disorder (CUD). METHODS Pseudocontinuous arterial spin labeling functional magnetic resonance imaging and resting blood oxygen level-dependent functional magnetic resonance imaging data were acquired in the same scan session in abstinent participants with CUD before residential treatment discharge and in 20 healthy matched control subjects. Substance use was assessed twice weekly following discharge. Relapsed participants were defined as those who used stimulants within 30 days following treatment discharge (n = 22); early remission participants (n = 18) did not. RESULTS Voxel-wise, whole-brain analysis revealed enhanced rCBF only in the left posterior hippocampus (pHp) in the relapsed group compared with the early remission and control groups. Using this pHp as a seed, increased rsFC strength with the posterior cingulate cortex (PCC)/precuneus was seen in the relapsed versus early remission subgroups. Together, both increased pHp rCBF and strengthened pHp-PCC rsFC predicted relapse with 75% accuracy at 30, 60, and 90 days following treatment. CONCLUSIONS In CUD participants at risk of early relapse, increased pHp basal activity and pHp-PCC circuit strength may reflect the propensity for heightened reactivity to cocaine cues and persistent cocaine-related ruminations. Mechanisms to mute hyperactivated brain regions and delink dysregulated neural circuits may prove useful to prevent relapse in patients with CUD. PMID:25749098

Dynamic and Inherent B0 Correction for DTI Using Stimulated Echo Spiral Imaging

PubMed Central

Avram, Alexandru V.; Guidon, Arnaud; Truong, Trong-Kha; Liu, Chunlei; Song, Allen W.

2013-01-01

Purpose To present a novel technique for high-resolution stimulated echo (STE) diffusion tensor imaging (DTI) with self-navigated interleaved spirals (SNAILS) readout trajectories that can inherently and dynamically correct for image artifacts due to spatial and temporal variations in the static magnetic field (B0) resulting from eddy currents, tissue susceptibilities, subject/physiological motion, and hardware instabilities. Methods The Hahn spin echo formed by the first two 90° radio-frequency pulses is balanced to consecutively acquire two additional images with different echo times (TE) and generate an inherent field map, while the diffusion-prepared STE signal remains unaffected. For every diffusion-encoding direction, an intrinsically registered field map is estimated dynamically and used to effectively and inherently correct for off-resonance artifacts in the reconstruction of the corresponding diffusion-weighted image (DWI). Results After correction with the dynamically acquired field maps, local blurring artifacts are specifically removed from individual STE DWIs and the estimated diffusion tensors have significantly improved spatial accuracy and larger fractional anisotropy. Conclusion Combined with the SNAILS acquisition scheme, our new method provides an integrated high-resolution short-TE DTI solution with inherent and dynamic correction for both motion-induced phase errors and off-resonance effects. PMID:23630029

Laser Speckle Imaging of Cerebral Blood Flow

NASA Astrophysics Data System (ADS)

Luo, Qingming; Jiang, Chao; Li, Pengcheng; Cheng, Haiying; Wang, Zhen; Wang, Zheng; Tuchin, Valery V.

Monitoring the spatio-temporal characteristics of cerebral blood flow (CBF) is crucial for studying the normal and pathophysiologic conditions of brain metabolism. By illuminating the cortex with laser light and imaging the resulting speckle pattern, relative CBF images with tens of microns spatial and millisecond temporal resolution can be obtained. In this chapter, a laser speckle imaging (LSI) method for monitoring dynamic, high-resolution CBF is introduced. To improve the spatial resolution of current LSI, a modified LSI method is proposed. To accelerate the speed of data processing, three LSI data processing frameworks based on graphics processing unit (GPU), digital signal processor (DSP), and field-programmable gate array (FPGA) are also presented. Applications for detecting the changes in local CBF induced by sensory stimulation and thermal stimulation, the influence of a chemical agent on CBF, and the influence of acute hyperglycemia following cortical spreading depression on CBF are given.

Lung Parenchymal Signal Intensity in MRI: A Technical Review with Educational Aspirations Regarding Reversible Versus Irreversible Transverse Relaxation Effects in Common Pulse Sequences.

PubMed

Mulkern, Robert; Haker, Steven; Mamata, Hatsuho; Lee, Edward; Mitsouras, Dimitrios; Oshio, Koichi; Balasubramanian, Mukund; Hatabu, Hiroto

2014-03-01

Lung parenchyma is challenging to image with proton MRI. The large air space results in ~l/5th as many signal-generating protons compared to other organs. Air/tissue magnetic susceptibility differences lead to strong magnetic field gradients throughout the lungs and to broad frequency distributions, much broader than within other organs. Such distributions have been the subject of experimental and theoretical analyses which may reveal aspects of lung microarchitecture useful for diagnosis. Their most immediate relevance to current imaging practice is to cause rapid signal decays, commonly discussed in terms of short T 2 * values of 1 ms or lower at typical imaging field strengths. Herein we provide a brief review of previous studies describing and interpreting proton lung spectra. We then link these broad frequency distributions to rapid signal decays, though not necessarily the exponential decays generally used to define T 2 * values. We examine how these decays influence observed signal intensities and spatial mapping features associated with the most prominent torso imaging sequences, including spoiled gradient and spin echo sequences. Effects of imperfect refocusing pulses on the multiple echo signal decays in single shot fast spin echo (SSFSE) sequences and effects of broad frequency distributions on balanced steady state free precession (bSSFP) sequence signal intensities are also provided. The theoretical analyses are based on the concept of explicitly separating the effects of reversible and irreversible transverse relaxation processes, thus providing a somewhat novel and more general framework from which to estimate lung signal intensity behavior in modern imaging practice.

Lung Parenchymal Signal Intensity in MRI: A Technical Review with Educational Aspirations Regarding Reversible Versus Irreversible Transverse Relaxation Effects in Common Pulse Sequences

PubMed Central

MULKERN, ROBERT; HAKER, STEVEN; MAMATA, HATSUHO; LEE, EDWARD; MITSOURAS, DIMITRIOS; OSHIO, KOICHI; BALASUBRAMANIAN, MUKUND; HATABU, HIROTO

2014-01-01

Lung parenchyma is challenging to image with proton MRI. The large air space results in ~l/5th as many signal-generating protons compared to other organs. Air/tissue magnetic susceptibility differences lead to strong magnetic field gradients throughout the lungs and to broad frequency distributions, much broader than within other organs. Such distributions have been the subject of experimental and theoretical analyses which may reveal aspects of lung microarchitecture useful for diagnosis. Their most immediate relevance to current imaging practice is to cause rapid signal decays, commonly discussed in terms of short T2* values of 1 ms or lower at typical imaging field strengths. Herein we provide a brief review of previous studies describing and interpreting proton lung spectra. We then link these broad frequency distributions to rapid signal decays, though not necessarily the exponential decays generally used to define T2* values. We examine how these decays influence observed signal intensities and spatial mapping features associated with the most prominent torso imaging sequences, including spoiled gradient and spin echo sequences. Effects of imperfect refocusing pulses on the multiple echo signal decays in single shot fast spin echo (SSFSE) sequences and effects of broad frequency distributions on balanced steady state free precession (bSSFP) sequence signal intensities are also provided. The theoretical analyses are based on the concept of explicitly separating the effects of reversible and irreversible transverse relaxation processes, thus providing a somewhat novel and more general framework from which to estimate lung signal intensity behavior in modern imaging practice. PMID:25228852

Electromagnetic Interactions in a Shielded PET/MRI System for Simultaneous PET/MR Imaging in 9.4 T: Evaluation and Results

NASA Astrophysics Data System (ADS)

Maramraju, Sri Harsha; Smith, S. David; Rescia, Sergio; Stoll, Sean; Budassi, Michael; Vaska, Paul; Woody, Craig; Schlyer, David

2012-10-01

We previously integrated a magnetic resonance-(MR-) compatible small-animal positron emission tomograph (PET) in a Bruker 9.4 T microMRI system to obtain simultaneous PET/MR images of a rat's brain and of a gated mouse-heart. To minimize electromagnetic interactions in our MR-PET system, viz., the effect of radiofrequency (RF) pulses on the PET, we tested our modular front-end PET electronics with various shield configurations, including a solid aluminum shield and one of thin segmented layers of copper. We noted that the gradient-echo RF pulses did not affect PET data when the PET electronics were shielded with either the aluminum- or the segmented copper-shields. However, there were spurious counts in the PET data resulting from high-intensity fast spin-echo RF pulses. Compared to the unshielded condition, they were attenuated effectively by the aluminum shield ( 97%) and the segmented copper shield ( 90%). We noted a decline in the noise rates as a function of increasing PET energy-discriminator threshold. In addition, we observed a notable decrease in the signal-to-noise ratio in spin-echo MR images with the segmented copper shields in place; however, this did not substantially degrade the quality of the MR images we obtained. Our results demonstrate that by surrounding a compact PET scanner with thin layers of segmented copper shields and integrating it inside a 9.4 T MR system, we can mitigate the impact of the RF on PET, while acquiring good-quality MR images.

In vivo imaging of cortical pathology in multiple sclerosis using ultra-high field MRI

PubMed Central

Mainero, C; Benner, T; Radding, A; van der Kouwe, A; Jensen, R; Rosen, B R.; Kinkel, R P.

2009-01-01

Objective: We used ultra-high field MRI to visualize cortical lesion types described by neuropathology in 16 patients with multiple sclerosis (MS) compared with 8 age-matched controls; to characterize the contrast properties of cortical lesions including T2*, T2, T1, and phase images; and to investigate the relationship between cortical lesion types and clinical data. Methods: We collected, on a 7-T scanner, 2-dimensional fast low-angle shot (FLASH)-T2*-weighted spoiled gradient-echo, T2-weighted turbo spin-echo (TSE) images (0.33 × 033 × 1 mm3), and a 3-dimensional magnetization-prepared rapid gradient echo. Results: Overall, 199 cortical lesions were detected in patients on both FLASH-T2* and T2-TSE scans. Seven-tesla MRI allowed for characterization of cortical plaques into type I (leukocortical), type II (intracortical), and type III/IV (subpial extending partly or completely through the cortical width) lesions as described histopathologically. Types III and IV were the most frequent type of cortical plaques (50.2%), followed by type I (36.2%) and type II (13.6%) lesions. Each lesion type was more frequent in secondary progressive than in relapsing–remitting MS. This difference, however, was significant only for type III/IV lesions. T2*-weighted images showed the highest, while phase images showed the lowest, contrast-to-noise ratio for all cortical lesion types. In patients, the number of type III/IV lesions was associated with greater disability (p < 0.02 by Spearman test) and older age (p < 0.04 by Spearman test). Conclusions: Seven-tesla MRI detected different histologic cortical lesion types in our small multiple sclerosis (MS) sample, suggesting, if validated in a larger population, that it may prove a valuable tool to assess the contribution of cortical MS pathology to clinical disability. GLOSSARY ANOVA = analysis of variance; BN = background noise; CNR = contrast-to-noise ratio; DIR = double-inversion recovery; EDSS = Expanded Disability Status Scale; FLAIR = fluid-attenuated inversion recovery; FLASH = fast low-angle shot; GM = gray matter; MPRAGE = magnetization-prepared rapid gradient echo; MR = magnetic resonance; MS = multiple sclerosis; NACGM = normal-appearing cortical gray matter; RF = radiofrequency; ROI = region of interest; RRMS = relapsing–remitting multiple sclerosis; SNR = signal-to-noise ratio; SPMS = secondary progressive multiple sclerosis; TA = time of acquisition; TE = echo time; TR = repetition time; TSE = turbo spin-echo; WM = white matter. PMID:19641168

Rapid water and lipid imaging with T2 mapping using a radial IDEAL-GRASE technique.

PubMed

Li, Zhiqiang; Graff, Christian; Gmitro, Arthur F; Squire, Scott W; Bilgin, Ali; Outwater, Eric K; Altbach, Maria I

2009-06-01

Three-point Dixon methods have been investigated as a means to generate water and fat images without the effects of field inhomogeneities. Recently, an iterative algorithm (IDEAL, iterative decomposition of water and fat with echo asymmetry and least squares estimation) was combined with a gradient and spin-echo acquisition strategy (IDEAL-GRASE) to provide a time-efficient method for lipid-water imaging with correction for the effects of field inhomogeneities. The method presented in this work combines IDEAL-GRASE with radial data acquisition. Radial data sampling offers robustness to motion over Cartesian trajectories as well as the possibility of generating high-resolution T(2) maps in addition to the water and fat images. The radial IDEAL-GRASE technique is demonstrated in phantoms and in vivo for various applications including abdominal, pelvic, and cardiac imaging.

Modified echo peak correction for radial acquisition regime (RADAR).

PubMed

Takizawa, Masahiro; Ito, Taeko; Itagaki, Hiroyuki; Takahashi, Tetsuhiko; Shimizu, Kanichirou; Harada, Junta

2009-01-01

Because radial sampling imposes many limitations on magnetic resonance (MR) imaging hardware, such as on the accuracy of the gradient magnetic field or the homogeneity of B(0), some correction of the echo signal is usually needed before image reconstruction. In our previous study, we developed an echo-peak-shift correction (EPSC) algorithm not easily affected by hardware performance. However, some artifacts remained in lung imaging, where tissue is almost absent, or in cardiac imaging, which is affected by blood flow. In this study, we modified the EPSC algorithm to improve the image quality of the radial aquisition regime (RADAR) and expand its application sequences. We assumed the artifacts were mainly caused by errors in the phase map for EPSC and used a phantom on a 1.5-tesla (T) MR scanner to investigate whether to modify the EPSC algorithm. To evaluate the effectiveness of EPSC, we compared results from T(1)- and T(2)-weighted images of a volunteer's lung region using the current and modified EPSC. We then applied the modified EPSC to RADAR spin echo (SE) and RADAR balanced steady-state acquisition with rewound gradient echo (BASG) sequence. The modified EPSC reduced phase discontinuity in the reference data used for EPSC and improved visualization of blood vessels in the lungs. Motion and blood flow caused no visible artifacts in the resulting images in either RADAR SE or RADAR BASG sequence. Use of the modified EPSC eliminated artifacts caused by signal loss in the reference data for EPSC. In addition, the modified EPSC was applied to RADAR SE and RADAR BASG sequences.

[MRI of focal liver lesions using a 1.5 turbo-spin-echo technique compared with spin-echo technique].

PubMed

Steiner, S; Vogl, T J; Fischer, P; Steger, W; Neuhaus, P; Keck, H

1995-08-01

The aim of our study was to evaluate a T2-weighted turbo-spinecho sequence in comparison to a T2-weighted spinecho sequence in imaging focal liver lesions. In our study 35 patients with suspected focal liver lesions were examined. Standardised imaging protocol included a conventional T2-weighted SE sequence (TR/TE = 2000/90/45, acquisition time = 10.20) as well as a T2-weighted TSE sequence (TR/TE = 4700/90, acquisition time = 6.33). Calculation of S/N and C/N ratio as a basis of quantitative evaluation was done using standard methods. A diagnostic score was implemented to enable qualitative assessment. In 7% (n = 2) the TSE sequence enabled detection of further liver lesions showing a size of less than 1 cm in diameter. Comparing anatomical details the TSE sequence was superior. S/N and C/N ratio of anatomic and pathologic structures of the TSE sequence were higher compared to results of the SE sequence. Our results indicate that the T2-weighted turbo-spinecho sequence is well appropriate for imaging focal liver lesions, and leads to reduction of imaging time.

Magnetic resonance imaging investigation of the bone conduction implant – a pilot study at 1.5 Tesla

PubMed Central

Jansson, Karl-Johan Fredén; Håkansson, Bo; Reinfeldt, Sabine; Rigato, Cristina; Eeg-Olofsson, Måns

2015-01-01

Purpose The objective of this pilot study was to investigate if an active bone conduction implant (BCI) used in an ongoing clinical study withstands magnetic resonance imaging (MRI) of 1.5 Tesla. In particular, the MRI effects on maximum power output (MPO), total harmonic distortion (THD), and demagnetization were investigated. Implant activation and image artifacts were also evaluated. Methods and materials One implant was placed on the head of a test person at the position corresponding to the normal position of an implanted BCI and applied with a static pressure using a bandage and scanned in a 1.5 Tesla MRI camera. Scanning was performed both with and without the implant, in three orthogonal planes, and for one spin-echo and one gradient-echo pulse sequence. Implant functionality was verified in-between the scans using an audio processor programmed to generate a sequence of tones when attached to the implant. Objective verification was also carried out by measuring MPO and THD on a skull simulator as well as retention force, before and after MRI. Results It was found that the exposure of 1.5 Tesla MRI only had a minor effect on the MPO, ie, it decreased over all frequencies with an average of 1.1±2.1 dB. The THD remained unchanged above 300 Hz and was increased only at lower frequencies. The retention magnet was demagnetized by 5%. The maximum image artifacts reached a distance of 9 and 10 cm from the implant in the coronal plane for the spin-echo and the gradient-echo sequence, respectively. The test person reported no MRI induced sound from the implant. Conclusion This pilot study indicates that the present BCI may withstand 1.5 Tesla MRI with only minor effects on its performance. No MRI induced sound was reported, but the head image was highly distorted near the implant. PMID:26604836

Magnetic resonance imaging investigation of the bone conduction implant - a pilot study at 1.5 Tesla.

PubMed

Jansson, Karl-Johan Fredén; Håkansson, Bo; Reinfeldt, Sabine; Rigato, Cristina; Eeg-Olofsson, Måns

2015-01-01

The objective of this pilot study was to investigate if an active bone conduction implant (BCI) used in an ongoing clinical study withstands magnetic resonance imaging (MRI) of 1.5 Tesla. In particular, the MRI effects on maximum power output (MPO), total harmonic distortion (THD), and demagnetization were investigated. Implant activation and image artifacts were also evaluated. One implant was placed on the head of a test person at the position corresponding to the normal position of an implanted BCI and applied with a static pressure using a bandage and scanned in a 1.5 Tesla MRI camera. Scanning was performed both with and without the implant, in three orthogonal planes, and for one spin-echo and one gradient-echo pulse sequence. Implant functionality was verified in-between the scans using an audio processor programmed to generate a sequence of tones when attached to the implant. Objective verification was also carried out by measuring MPO and THD on a skull simulator as well as retention force, before and after MRI. It was found that the exposure of 1.5 Tesla MRI only had a minor effect on the MPO, ie, it decreased over all frequencies with an average of 1.1±2.1 dB. The THD remained unchanged above 300 Hz and was increased only at lower frequencies. The retention magnet was demagnetized by 5%. The maximum image artifacts reached a distance of 9 and 10 cm from the implant in the coronal plane for the spin-echo and the gradient-echo sequence, respectively. The test person reported no MRI induced sound from the implant. This pilot study indicates that the present BCI may withstand 1.5 Tesla MRI with only minor effects on its performance. No MRI induced sound was reported, but the head image was highly distorted near the implant.

Diagnosis of hepatic metastasis: comparison of respiration-triggered diffusion-weighted echo-planar MRI and five t2-weighted turbo spin-echo sequences.

PubMed

Bruegel, Melanie; Gaa, Jochen; Waldt, Simone; Woertler, Klaus; Holzapfel, Konstantin; Kiefer, Berthold; Rummeny, Ernst J

2008-11-01

The purpose of this study was to compare the value of respiration-triggered diffusion-weighted (DW) single-shot echo-planar MRI (EPI) and five variants of T2-weighted turbo spin-echo (TSE) sequences in the diagnosis of hepatic metastasis. Fifty-two patients with extrahepatic primary malignant tumors underwent 1.5-T MRI that included DW EPI and the following variants of T2-weighted TSE techniques: breath-hold fat-suppressed HASTE, breath-hold fat-supressed TSE, respiration-triggered fat-suppressed TSE, breath-hold STIR, and respiration-triggered STIR. Images were reviewed independently by two blinded observers who used a 5-point confidence scale to identify lesions. Results were correlated with surgical and histopathologic findings and follow-up imaging findings. The accuracy of each technique was measured with free-response receiver operating characteristic analysis. A total of 118 hepatic metastatic lesions (mean diameter, 12.8 mm; range, 3-84 mm) were evaluated. Accuracy values were higher (p < 0.001) with DW EPI (0.91-0.92) than with the T2-weighted TSE techniques (0.47-0.67). Imaging with the HASTE sequence (0.47-0.52) was less accurate (p < 0.05) than imaging with the breath-hold TSE, breath-hold STIR, respiration-triggered TSE, and respiration-triggered STIR sequences (0.59-0.67). Sensitivity was higher (p < 0.001) with DW EPI (0.88-0.91) than with T2-weighted TSE techniques (0.45-0.62). For small (< or = 10 mm) metastatic lesions only, the differences in sensitivity between DW EPI (0.85) and T2-weighted TSE techniques (0.26-0.44) were even more pronounced. DW EPI was more sensitive and more accurate than imaging with T2-weighted TSE techniques. Because of the black-blood effect on vessels and low susceptibility to motion artifacts, DW EPI was particularly useful for the detection of small (< or = 10 mm) metastatic lesions.

Basic physics of nuclear magnetic resonance.

PubMed

Patz, S

1986-01-01

This review of basic physics of nuclear magnetic resonance (NMR) discusses precession of magnetic nuclei in a static external field, introduces the concept of the rotating frame, and describes excitation of nuclei by an RF field. Treats subject of T1 and T2 relaxation from the dual viewpoints of (1) phenomena of relaxation times for both the longitudinal and transverse magnetization and (2) relaxation resulting from local field fluctuations. It describes practical ways in which T1 and T2 are measured (i.e., inversion recovery and spin-echo) and gives the value of the nuclear magnetization in thermodynamic equilibrium with a static external field. It discusses the reduction of NMR signal resulting from saturation. These concepts are related to clinical use with a set of four spin-echo images of a human head.

Rapid ex vivo imaging of PAIII prostate to bone tumor with SWIFT-MRI.

PubMed

Luhach, Ihor; Idiyatullin, Djaudat; Lynch, Conor C; Corum, Curt; Martinez, Gary V; Garwood, Michael; Gillies, Robert J

2014-09-01

The limiting factor for MRI of skeletal/mineralized tissue is fast transverse relaxation. A recent advancement in MRI technology, SWIFT (Sweep Imaging with Fourier Transform), is emerging as a new approach to overcome this difficulty. Among other techniques like UTE, ZTE, and WASPI, the application of SWIFT technology has the strong potential to impact preclinical and clinical imaging, particularly in the context of primary or metastatic bone cancers because it has the added advantage of imaging water in mineralized tissues of bone allowing MRI images to be obtained of tissues previously visible only with modalities such as computed tomography (CT). The goal of the current study is to examine the feasibility of SWIFT for the assessment of the prostate cancer induced changes in bone formation (osteogenesis) and destruction (osteolysis) in ex vivo specimens. A luciferase expressing prostate cancer cell line (PAIII) or saline control was inoculated directly into the tibia of 6-week-old immunocompromised male mice. Tumor growth was assessed weekly for 3 weeks before euthanasia and dissection of the tumor bearing and sham tibias. The ex vivo mouse tibia specimens were imaged with a 9.4 Tesla (T) and 7T MRI systems. SWIFT images are compared with traditional gradient-echo and spin-echo MRI images as well as CT and histological sections. SWIFT images with nominal resolution of 78 μm are obtained with the tumor and different bone structures identified. Prostate cancer induced changes in the bone microstructure are visible in SWIFT images, which is supported by spin-echo, high resolution CT and histological analysis. SWIFT MRI is capable of high-quality high-resolution ex vivo imaging of bone tumor and surrounding bone and soft tissues. Furthermore, SWIFT MRI shows promise for in vivo bone tumor imaging, with the added benefits of nonexposure to ionizing radiation, quietness, and speed. Copyright © 2013 Wiley Periodicals, Inc.

Multishot cartesian turbo spin-echo diffusion imaging using iterative POCSMUSE Reconstruction.

PubMed

Zhang, Zhe; Zhang, Bing; Li, Ming; Liang, Xue; Chen, Xiaodong; Liu, Renyuan; Zhang, Xin; Guo, Hua

2017-07-01

To report a diffusion imaging technique insensitive to off-resonance artifacts and motion-induced ghost artifacts using multishot Cartesian turbo spin-echo (TSE) acquisition and iterative POCS-based reconstruction of multiplexed sensitivity encoded magnetic resonance imaging (MRI) (POCSMUSE) for phase correction. Phase insensitive diffusion preparation was used to deal with the violation of the Carr-Purcell-Meiboom-Gill (CPMG) conditions of TSE diffusion-weighted imaging (DWI), followed by a multishot Cartesian TSE readout for data acquisition. An iterative diffusion phase correction method, iterative POCSMUSE, was developed and implemented to eliminate the ghost artifacts in multishot TSE DWI. The in vivo human brain diffusion images (from one healthy volunteer and 10 patients) using multishot Cartesian TSE were acquired at 3T and reconstructed using iterative POCSMUSE, and compared with single-shot and multishot echo-planar imaging (EPI) results. These images were evaluated by two radiologists using visual scores (considering both image quality and distortion levels) from 1 to 5. The proposed iterative POCSMUSE reconstruction was able to correct the ghost artifacts in multishot DWI. The ghost-to-signal ratio of TSE DWI using iterative POCSMUSE (0.0174 ± 0.0024) was significantly (P < 0.0005) smaller than using POCSMUSE (0.0253 ± 0.0040). The image scores of multishot TSE DWI were significantly higher than single-shot (P = 0.004 and 0.006 from two reviewers) and multishot (P = 0.008 and 0.004 from two reviewers) EPI-based methods. The proposed multishot Cartesian TSE DWI using iterative POCSMUSE reconstruction can provide high-quality diffusion images insensitive to motion-induced ghost artifacts and off-resonance related artifacts such as chemical shifts and susceptibility-induced image distortions. 1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:167-174. © 2016 International Society for Magnetic Resonance in Medicine.

Distortion-free diffusion tensor imaging for evaluation of lumbar nerve roots: Utility of direct coronal single-shot turbo spin-echo diffusion sequence.

PubMed

Sakai, Takayuki; Doi, Kunio; Yoneyama, Masami; Watanabe, Atsuya; Miyati, Tosiaki; Yanagawa, Noriyuki

2018-06-01

Diffusion tensor imaging (DTI) based on a single-shot echo planer imaging (EPI-DTI) is an established method that has been used for evaluation of lumbar nerve disorders in previous studies, but EPI-DTI has problems such as a long acquisition time, due to a lot of axial slices, and geometric distortion. To solve these problems, we attempted to apply DTI based on a single-shot turbo spin echo (TSE-DTI) with direct coronal acquisition. Our purpose in this study was to investigate whether TSE-DTI may be more useful for evaluation of lumbar nerve disorders than EPI-DTI. First, lumbar nerve roots of five healthy volunteers were evaluated for optimization of imaging parameters with TSE-DTI including b-values and the number of motion proving gradient (MPG) directions. Subsequently, optimized TSE-DTI was quantitatively compared with conventional EPI-DTI by using fractional anisotropy (FA) values and visual scores in subjective visual evaluation of tractography. Lumbar nerve roots of six patients, who had unilateral neurologic symptoms in one leg, were evaluated by the optimized TSE-DTI. TSE-DTI with b-value of 400 s/mm 2 and 32 diffusion-directions could reduce the image distortion compared with EPI-DTI, and showed that the average FA values on the symptomatic side for six patients were significantly lower than those on the non-symptomatic side (P < 0.05). Tractography with TSE-DTI might show damaged areas of lumbar nerve roots without severe image distortion. TSE-DTI might improve the reproducibility in measurements of FA values for quantification of a nerve disorder, and would become a useful tool for diagnosis of low back pain. Copyright © 2018 Elsevier Inc. All rights reserved.

Cardiac MOLLI T1 mapping at 3.0 T: comparison of patient-adaptive dual-source RF and conventional RF transmission.

PubMed

Rasper, Michael; Nadjiri, Jonathan; Sträter, Alexandra S; Settles, Marcus; Laugwitz, Karl-Ludwig; Rummeny, Ernst J; Huber, Armin M

2017-06-01

To prospectively compare image quality and myocardial T 1 relaxation times of modified Look-Locker inversion recovery (MOLLI) imaging at 3.0 T (T) acquired with patient-adaptive dual-source (DS) and conventional single-source (SS) radiofrequency (RF) transmission. Pre- and post-contrast MOLLI T 1 mapping using SS and DS was acquired in 27 patients. Patient wise and segment wise analysis of T 1 times was performed. The correlation of DS MOLLI measurements with a reference spin echo sequence was analysed in phantom experiments. DS MOLLI imaging reduced T 1 standard deviation in 14 out of 16 myocardial segments (87.5%). Significant reduction of T 1 variance could be obtained in 7 segments (43.8%). DS significantly reduced myocardial T 1 variance in 16 out of 25 patients (64.0%). With conventional RF transmission, dielectric shading artefacts occurred in six patients causing diagnostic uncertainty. No according artefacts were found on DS images. DS image findings were in accordance with conventional T 1 mapping and late gadolinium enhancement (LGE) imaging. Phantom experiments demonstrated good correlation of myocardial T 1 time between DS MOLLI and spin echo imaging. Dual-source RF transmission enhances myocardial T 1 homogeneity in MOLLI imaging at 3.0 T. The reduction of signal inhomogeneities and artefacts due to dielectric shading is likely to enhance diagnostic confidence.

Music-based magnetic resonance fingerprinting to improve patient comfort during MRI examinations.

PubMed

Ma, Dan; Pierre, Eric Y; Jiang, Yun; Schluchter, Mark D; Setsompop, Kawin; Gulani, Vikas; Griswold, Mark A

2016-06-01

Unpleasant acoustic noise is a drawback of almost every MRI scan. Instead of reducing acoustic noise to improve patient comfort, we propose a technique for mitigating the noise problem by producing musical sounds directly from the switching magnetic fields while simultaneously quantifying multiple important tissue properties. MP3 music files were converted to arbitrary encoding gradients, which were then used with varying flip angles and repetition times in a two- and three-dimensional magnetic resonance fingerprinting (MRF) examination. This new acquisition method, named MRF-Music, was used to quantify T1 , T2 , and proton density maps simultaneously while providing pleasing sounds to the patients. MRF-Music scans improved patient comfort significantly during MRI examinations. The T1 and T2 values measured from phantom are in good agreement with those from the standard spin echo measurements. T1 and T2 values from the brain scan are also close to previously reported values. MRF-Music sequence provides significant improvement in patient comfort compared with the MRF scan and other fast imaging techniques such as echo planar imaging and turbo spin echo scans. It is also a fast and accurate quantitative method that quantifies multiple relaxation parameters simultaneously. Magn Reson Med 75:2303-2314, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Colorectal carcinoma: Ex vivo evaluation using 3-T high-spatial-resolution quantitative T2 mapping and its correlation with histopathologic findings.

PubMed

Yamada, Ichiro; Yoshino, Norio; Hikishima, Keigo; Miyasaka, Naoyuki; Yamauchi, Shinichi; Uetake, Hiroyuki; Yasuno, Masamichi; Saida, Yukihisa; Tateishi, Ukihide; Kobayashi, Daisuke; Eishi, Yoshinobu

2017-05-01

In this study, we aimed to evaluate the feasibility of determining the mural invasion depths of colorectal carcinomas using high-spatial-resolution (HSR) quantitative T2 mapping on a 3-T magnetic resonance (MR) scanner. Twenty colorectal specimens containing adenocarcinomas were imaged on a 3-T MR system equipped with a 4-channel phased-array surface coil. HSR quantitative T2 maps were acquired using a spin-echo sequence with a repetition time/echo time of 7650/22.6-361.6ms (16 echoes), 87×43.5-mm field of view, 2-mm section thickness, 448×224 matrix, and average of 1. HSR fast-spin-echo T2-weighted images were also acquired. Differences between the T2 values (ms) of the tumor tissue, colorectal wall layers, and fibrosis were measured, and the MR images and histopathologic findings were compared. In all specimens (20/20, 100%), the HSR quantitative T2 maps clearly depicted an 8-layer normal colorectal wall in which the T2 values of each layer differed from those of the adjacent layer(s) (P<0.001). Using this technique, fibrosis (73.6±9.4ms) and tumor tissue (104.2±6.4ms) could also be clearly differentiated (P<0.001). In 19 samples (95%), the HSR quantitative T2 maps and histopathologic data yielded the same findings regarding the tumor invasion depth. Our results indicate that 3-T HSR quantitative T2 mapping is useful for distinguishing colorectal wall layers and differentiating tumor and fibrotic tissues. Accordingly, this technique could be used to determine mural invasion by colorectal carcinomas with a high level of accuracy. Copyright © 2017 Elsevier Inc. All rights reserved.

Volume interpolated 3D-spoiled gradient echo sequence is better than dynamic contrast spin echo sequence for MRI detection of corticotropin secreting pituitary microadenomas.

PubMed

Kasaliwal, Rajeev; Sankhe, Shilpa S; Lila, Anurag R; Budyal, Sweta R; Jagtap, Varsha S; Sarathi, Vijaya; Kakade, Harshal; Bandgar, Tushar; Menon, Padmavathy S; Shah, Nalini S

2013-06-01

Various techniques have been attempted to increase the yield of magnetic resonance imaging (MRI) for localization of pituitary microadenomas in corticotropin (ACTH)-dependent Cushing's syndrome (CS). To compare the performance of dynamic contrast spin echo (DC-SE) and volume interpolated 3D-spoiled gradient echo (VI-SGE) MR sequences in the diagnostic evaluation of ACTH-dependent CS. Data was analysed retrospectively from a series of ACTH-dependent CS patients treated over 2-year period at a tertiary care referral centre (2009-2011). Thirty-six patients (24 female and 12 male) were diagnosed to have ACTH-dependent CS during the study period. All patients underwent MRI by both sequences during a single examination. Cases with negative and equivocal pituitary MR imaging underwent corticotropin-releasing hormone (CRH) stimulated bilateral inferior petrosal sinus sampling (BIPSS) to confirm pituitary origin of ACTH excess state. Thirty patients were finally diagnosed to have Cushing's disease (CD) [based on histopathology proof of adenoma and/or remission (partial/complete) of hypercortisolism postsurgery]. Six patients were diagnosed to have histopathologically proven ectopic CS. Of 30 patients with CD, 24 patients had microadenomas and 6 patients had macroadenomas. DC-SE MRI sequence was able to identify microadenomas in 16 of 24 patients, whereas postcontrast VI-SGE sequence was able to identify microadenomas in 21 of 24 patients. All six patients of ectopic CS had negative pituitary MR imaging by both techniques (specificity: 100%). VI-SGE MR sequence was better for localization of pituitary microadenomas particularly when DC-SE MR sequence is negative or equivocal and should be used in addition to DC-SE MR sequence for the evaluation of ACTH-dependent CS. © 2012 John Wiley & Sons Ltd.

Symptom correlates of cerebral blood flow following acute concussion.

PubMed

Churchill, Nathan W; Hutchison, Michael G; Graham, Simon J; Schweizer, Tom A

2017-01-01

Concussion is associated with significant symptoms within hours to days post-injury, including disturbances in physical function, cognition, sleep and emotion. However, little is known about how subjective impairments correlate with objective measures of cerebrovascular function following brain injury. This study examined the relationship between symptoms and cerebral blood flow (CBF) in individuals following sport-related concussion. Seventy university level athletes had CBF measured using Arterial Spin Labelling (ASL), including 35 with acute concussion and 35 matched controls and their symptoms were assessed using the Sport Concussion Assessment Tool 3 (SCAT3). For concussed athletes, greater total symptom severity was associated with elevated posterior cortical CBF, although mean CBF was not significantly different from matched controls ( p  = 0.46). Examining symptom clusters, athletes reporting greater cognitive symptoms also had lower frontal and subcortical CBF, relative to athletes with greater somatic symptoms. The "cognitive" and "somatic" subgroups also exhibited significant differences in CBF relative to controls ( p  ≤ 0.026). This study demonstrates objective CBF correlates of symptoms in recently concussed athletes and shows that specific symptom clusters may have distinct patterns of altered CBF, significantly extending our understanding of the neurobiology of concussion and traumatic brain injury.

On the application of magic echo cycles for quadrupolar echo spectroscopy of spin-1 nuclei.

PubMed

Mananga, E S; Roopchand, R; Rumala, Y S; Boutis, G S

2007-03-01

Magic echo cycles are introduced for performing quadrupolar echo spectroscopy of spin-1 nuclei. An analysis is performed via average Hamiltonian theory showing that the evolution under chemical shift or static field inhomogeneity can be refocused simultaneously with the quadrupolar interaction using these cycles. Due to the higher convergence in the Magnus expansion, with sufficient RF power, magic echo based quadrupolar echo spectroscopy outperforms the conventional two pulse quadrupolar echo in signal to noise. Experiments highlighting a signal to noise enhancement over the entire bandwidth of the quadrupolar pattern of a powdered sample of deuterated polyethelene are shown.

An Automated Measurement of Ciliary Beating Frequency using a Combined Optical Flow and Peak Detection.

PubMed

Kim, Woojae; Han, Tae Hwa; Kim, Hyun Jun; Park, Man Young; Kim, Ku Sang; Park, Rae Woong

2011-06-01

The mucociliary transport system is a major defense mechanism of the respiratory tract. The performance of mucous transportation in the nasal cavity can be represented by a ciliary beating frequency (CBF). This study proposes a novel method to measure CBF by using optical flow. To obtain objective estimates of CBF from video images, an automated computer-based image processing technique is developed. This study proposes a new method based on optical flow for image processing and peak detection for signal processing. We compare the measuring accuracy of the method in various combinations of image processing (optical flow versus difference image) and signal processing (fast Fourier transform [FFT] vs. peak detection [PD]). The digital high-speed video method with a manual count of CBF in slow motion video play, is the gold-standard in CBF measurement. We obtained a total of fifty recorded ciliated sinonasal epithelium images to measure CBF from the Department of Otolaryngology. The ciliated sinonasal epithelium images were recorded at 50-100 frames per second using a charge coupled device camera with an inverted microscope at a magnification of ×1,000. The mean square errors and variance for each method were 1.24, 0.84 Hz; 11.8, 2.63 Hz; 3.22, 1.46 Hz; and 3.82, 1.53 Hz for optical flow (OF) + PD, OF + FFT, difference image [DI] + PD, and DI + FFT, respectively. Of the four methods, PD using optical flow showed the best performance for measuring the CBF of nasal mucosa. The proposed method was able to measure CBF more objectively and efficiently than what is currently possible.

Electrical detection of electron-spin-echo envelope modulations in thin-film silicon solar cells

NASA Astrophysics Data System (ADS)

Fehr, M.; Behrends, J.; Haas, S.; Rech, B.; Lips, K.; Schnegg, A.

2011-11-01

Electrically detected electron-spin-echo envelope modulations (ED-ESEEM) were employed to detect hyperfine interactions between nuclear spins and paramagnetic sites, determining spin-dependent transport processes in multilayer thin-film microcrystalline silicon solar cells. Electrical detection in combination with a modified Hahn-echo sequence was used to measure echo modulations induced by 29Si, 31P, and 1H nuclei weakly coupled to electron spins of paramagnetic sites in the amorphous and microcrystalline solar cell layers. In the case of CE centers in the μc-Si:H i-layer, the absence of 1H ESEEM modulations indicates that the adjacencies of CE centers are depleted from hydrogen atoms. On the basis of this result, we discuss several models for the microscopic origin of the CE center and conclusively assign those centers to coherent twin boundaries inside of crystalline grains in μc-Si:H.

Basic spin physics.

PubMed

Pipe, J G

1999-11-01

Magnetic resonance imaging is fundamentally a measurement of the magnetism inherent in some nuclear isotopes; of these the proton, or hydrogen atom, is of particular interest for clinical applications. The magnetism in each nucleus is often referred to as spin. A strong, static magnetic field B0 is used to align spins, forming a magnetic density within the patient. A second, rotating magnetic field B1 (RF pulse) is applied for a short duration, which rotates the spins away from B0 in a process called excitation. After the spins are rotated away from B0, the RF pulse is turned off, and the spins precess about B0. As long as the spins are all pointing in the same direction at any one time (have phase coherence), they act in concert to create rapidly oscillating magnetic fields. These fields in turn create a current in an appropriately placed receiver coil, in a manner similar to that of an electrical generator. The precessing magnetization decays rapidly in a duration roughly given by the T2 time constant. At the same time, but at a slower rate, magnetization forms again along the direction of B0; the duration of this process is roughly expressed by the T1 time constant. The precessional frequency of each spin is proportional to the magnetic field experienced at the nucleus. Small variations in this magnetic field can have dramatic effects on the MR image, caused in part by loss of phase coherence. These magnetic field variations can arise because of magnet design, the magnetic properties (susceptibility) of tissues and other materials, and the nuclear environment unique to various sites within any given molecule. The loss of phase coherence can be effectively eliminated by the use of RF refocusing pulses. Conventional MR imaging experiments can be characterized as either gradient echo or spin echo, the latter indicating the use of a RF refocusing pulse, and by the parameters TR, TE, and flip angle alpha. Tissues, in turn, are characterized by their individual spin density, M0, and by the T1, T2, and T2* time constants. Knowledge of these parameters allows one to calculate the resulting signal from a given tissue for a given MR imaging experiment.

Spectral editing of weakly coupled spins using variable flip angles in PRESS constant echo time difference spectroscopy: Application to GABA

NASA Astrophysics Data System (ADS)

Snyder, Jeff; Hanstock, Chris C.; Wilman, Alan H.

2009-10-01

A general in vivo magnetic resonance spectroscopy editing technique is presented to detect weakly coupled spin systems through subtraction, while preserving singlets through addition, and is applied to the specific brain metabolite γ-aminobutyric acid (GABA) at 4.7 T. The new method uses double spin echo localization (PRESS) and is based on a constant echo time difference spectroscopy approach employing subtraction of two asymmetric echo timings, which is normally only applicable to strongly coupled spin systems. By utilizing flip angle reduction of one of the two refocusing pulses in the PRESS sequence, we demonstrate that this difference method may be extended to weakly coupled systems, thereby providing a very simple yet effective editing process. The difference method is first illustrated analytically using a simple two spin weakly coupled spin system. The technique was then demonstrated for the 3.01 ppm resonance of GABA, which is obscured by the strong singlet peak of creatine in vivo. Full numerical simulations, as well as phantom and in vivo experiments were performed. The difference method used two asymmetric PRESS timings with a constant total echo time of 131 ms and a reduced 120° final pulse, providing 25% GABA yield upon subtraction compared to two short echo standard PRESS experiments. Phantom and in vivo results from human brain demonstrate efficacy of this method in agreement with numerical simulations.

Neutron resonance spin echo with longitudinal DC fields

NASA Astrophysics Data System (ADS)

Krautloher, Maximilian; Kindervater, Jonas; Keller, Thomas; Häußler, Wolfgang

2016-12-01

We report on the design, construction, and performance of a neutron resonance spin echo (NRSE) instrument employing radio frequency (RF) spin flippers combining RF fields with DC fields, the latter oriented parallel (longitudinal) to the neutron propagation direction (longitudinal NRSE (LNRSE)). The advantage of the longitudinal configuration is the inherent homogeneity of the effective magnetic path integrals. In the center of the RF coils, the sign of the spin precession phase is inverted by a π flip of the neutron spins, such that non-uniform spin precession at the boundaries of the RF flippers is canceled. The residual inhomogeneity can be reduced by Fresnel- or Pythagoras-coils as in the case of conventional spin echo instruments (neutron spin echo (NSE)). Due to the good intrinsic homogeneity of the B0 coils, the current densities required for the correction coils are at least a factor of three less than in conventional NSE. As the precision and the current density of the correction coils are the limiting factors for the resolution of both NSE and LNRSE, the latter has the intrinsic potential to surpass the energy resolution of present NSE instruments. Our prototype LNRSE spectrometer described here was implemented at the resonance spin echo for diverse applications (RESEDA) beamline at the MLZ in Garching, Germany. The DC fields are generated by B0 coils, based on resistive split-pair solenoids with an active shielding for low stray fields along the beam path. One pair of RF flippers at a distance of 2 m generates a field integral of ˜0.5 Tm. The LNRSE technique is a future alternative for high-resolution spectroscopy of quasi-elastic excitations. In addition, it also incorporates the MIEZE technique, which allows to achieve spin echo resolution for spin depolarizing samples and sample environments. Here we present the results of numerical optimization of the coil geometry and first data from the prototype instrument.

Optical resonance imaging: An optical analog to MRI with sub-diffraction-limited capabilities.

PubMed

Allodi, Marco A; Dahlberg, Peter D; Mazuski, Richard J; Davis, Hunter C; Otto, John P; Engel, Gregory S

2016-12-21

We propose here optical resonance imaging (ORI), a direct optical analog to magnetic resonance imaging (MRI). The proposed pulse sequence for ORI maps space to time and recovers an image from a heterodyne-detected third-order nonlinear photon echo measurement. As opposed to traditional photon echo measurements, the third pulse in the ORI pulse sequence has significant pulse-front tilt that acts as a temporal gradient. This gradient couples space to time by stimulating the emission of a photon echo signal from different lateral spatial locations of a sample at different times, providing a widefield ultrafast microscopy. We circumvent the diffraction limit of the optics by mapping the lateral spatial coordinate of the sample with the emission time of the signal, which can be measured to high precision using interferometric heterodyne detection. This technique is thus an optical analog of MRI, where magnetic-field gradients are used to localize the spin-echo emission to a point below the diffraction limit of the radio-frequency wave used. We calculate the expected ORI signal using 15 fs pulses and 87° of pulse-front tilt, collected using f /2 optics and find a two-point resolution 275 nm using 800 nm light that satisfies the Rayleigh criterion. We also derive a general equation for resolution in optical resonance imaging that indicates that there is a possibility of superresolution imaging using this technique. The photon echo sequence also enables spectroscopic determination of the input and output energy. The technique thus correlates the input energy with the final position and energy of the exciton.

Comparison of amyloid plaque contrast generated by T2-, T2*-, and susceptibility-weighted imaging methods in transgenic mouse models of Alzheimer’s disease

PubMed Central

Chamberlain, Ryan; Reyes, Denise; Curran, Geoffrey L.; Marjanska, Malgorzata; Wengenack, Thomas M.; Poduslo, Joseph F.; Garwood, Michael; Jack, Clifford R.

2009-01-01

One of the hallmark pathologies of Alzheimer’s disease (AD) is amyloid plaque deposition. Plaques appear hypointense on T2- and T2*-weighted MR images probably due to the presence of endogenous iron, but no quantitative comparison of various imaging techniques has been reported. We estimated the T1, T2, T2*, and proton density values of cortical plaques and normal cortical tissue and analyzed the plaque contrast generated by a collection of T2-, T2*-, and susceptibility-weighted imaging (SWI) methods in ex vivo transgenic mouse specimens. The proton density and T1 values were similar for both cortical plaques and normal cortical tissue. The T2 and T2* values were similar in cortical plaques, which indicates that the iron content of cortical plaques may not be as large as previously thought. Ex vivo plaque contrast was increased compared to a previously reported spin echo sequence by summing multiple echoes and by performing SWI; however, gradient echo and susceptibility weighted imaging was found to be impractical for in vivo imaging due to susceptibility interface-related signal loss in the cortex. PMID:19253386

Comparison of magnetic resonance imaging sequences for depicting the subthalamic nucleus for deep brain stimulation.

PubMed

Nagahama, Hiroshi; Suzuki, Kengo; Shonai, Takaharu; Aratani, Kazuki; Sakurai, Yuuki; Nakamura, Manami; Sakata, Motomichi

2015-01-01

Electrodes are surgically implanted into the subthalamic nucleus (STN) of Parkinson's disease patients to provide deep brain stimulation. For ensuring correct positioning, the anatomic location of the STN must be determined preoperatively. Magnetic resonance imaging has been used for pinpointing the location of the STN. To identify the optimal imaging sequence for identifying the STN, we compared images produced with T2 star-weighted angiography (SWAN), gradient echo T2*-weighted imaging, and fast spin echo T2-weighted imaging in 6 healthy volunteers. Our comparison involved measurement of the contrast-to-noise ratio (CNR) for the STN and substantia nigra and a radiologist's interpretations of the images. Of the sequences examined, the CNR and qualitative scores were significantly higher on SWAN images than on other images (p < 0.01) for STN visualization. Kappa value (0.74) on SWAN images was the highest in three sequences for visualizing the STN. SWAN is the sequence best suited for identifying the STN at the present time.

Free-breathing echo-planar imaging based diffusion-weighted magnetic resonance imaging of the liver with prospective acquisition correction.

PubMed

Asbach, Patrick; Hein, Patrick A; Stemmer, Alto; Wagner, Moritz; Huppertz, Alexander; Hamm, Bernd; Taupitz, Matthias; Klessen, Christian

2008-01-01

To evaluate soft tissue contrast and image quality of a respiratory-triggered echo-planar imaging based diffusion-weighted sequence (EPI-DWI) with different b values for magnetic resonance imaging (MRI) of the liver. Forty patients were examined. Quantitative and qualitative evaluation of contrast was performed. Severity of artifacts and overall image quality in comparison with a T2w turbo spin-echo (T2-TSE) sequence were scored. The liver-spleen contrast was significantly higher (P < 0.05) for the EPI-DWI compared with the T2-TSE sequence (0.47 +/- 0.11 (b50); 0.48 +/- 0.13 (b300); 0.47 +/- 0.13 (b600) vs 0.38 +/- 0.11). Liver-lesion contrast strongly depends on the b value of the DWI sequence and decreased with higher b values (b50, 0.47 +/- 0.19; b300, 0.40 +/- 0.20; b600, 0.28 +/- 0.23). Severity of artifacts and overall image quality were comparable to the T2-TSE sequence when using a low b value (P > 0.05), artifacts increased and image quality decreased with higher b values (P < 0.05). Respiratory-triggered EPI-DWI of the liver is feasible because good image quality and favorable soft tissue contrast can be achieved.

Fast detection of diffuse axonal damage in severe traumatic brain injury: comparison of gradient-recalled echo and turbo proton echo-planar spectroscopic imaging MRI sequences.

PubMed

Giugni, Elisabetta; Sabatini, Umberto; Hagberg, Gisela E; Formisano, Rita; Castriota-Scanderbeg, Alessandro

2005-05-01

Diffuse axonal injury (DAI) is a common type of primary neuronal injury in patients with severe traumatic brain injury (TBI), and is frequently accompanied by tissue tear hemorrhage. T2-weighted gradient-recalled echo (GRE) sequences are more sensitive than T2-weighted spin-echo images for detection of hemorrhage. The purpose of this study is to compare turbo Proton Echo Planar Spectroscopic Imaging (t-PEPSI), an extremely fast sequence, with GRE sequence in the detection of DAI. Twenty-one patients (mean age 26.8 years) with severe TBI occurred at least 3 months earlier, underwent a brain MR Imaging study on a 1.5-T scanner. A qualitative evaluation of the t-PEPSI sequences was performed by identifying the optimal echo time and in-plane resolution. The number and size of DAI lesions, as well as the signal intensity contrast ratio (SI CR), were computed for each set of GRE and t-PEPSI images, and divided according to their anatomic location as lobar and/or deep brain. There was no significant difference between GRE and t-PEPSI sequences in the detection of the total number of DAI lesions (291 vs. 230, respectively). GRE sequence delineated a higher number of DAI in the temporal lobe compared to the t-PEPSI sequence (74 vs. 37, P < .004), while no differences were found for the other regions. The SI CR was significantly lower with the t-PEPSI than the GRE sequence (P < .00001). Owing to its very short scan time and high sensitivity to the hemorrhage foci, the t-PEPSI sequence may be used as an alternative to the GRE to assess brain DAI in severe TBI patients, especially if uncooperative and medically unstable.

Polaron spin echo envelope modulations in an organic semiconducting polymer

DOE PAGES

Mkhitaryan, V. V.; Dobrovitski, V. V.

2017-06-01

Here, we present a theoretical analysis of the electron spin echo envelope modulation (ESEEM) spectra of polarons in semiconducting π -conjugated polymers. We show that the contact hyperfine coupling and the dipolar interaction between the polaron and the proton spins give rise to different features in the ESEEM spectra. Our theory enables direct selective probe of different groups of nuclear spins, which affect the polaron spin dynamics. Namely, we demonstrate how the signal from the distant protons (coupled to the polaron spin via dipolar interactions) can be distinguished from the signal coming from the protons residing on the polaron sitemore » (coupled to the polaron spin via contact hyperfine interaction). We propose a method for directly probing the contact hyperfine interaction, that would enable detailed study of the polaron orbital state and its immediate environment. Lastly, we also analyze the decay of the spin echo modulation, and its connection to the polaron transport.« less

Coherent Spin Control at the Quantum Level in an Ensemble-Based Optical Memory.

PubMed

Jobez, Pierre; Laplane, Cyril; Timoney, Nuala; Gisin, Nicolas; Ferrier, Alban; Goldner, Philippe; Afzelius, Mikael

2015-06-12

Long-lived quantum memories are essential components of a long-standing goal of remote distribution of entanglement in quantum networks. These can be realized by storing the quantum states of light as single-spin excitations in atomic ensembles. However, spin states are often subjected to different dephasing processes that limit the storage time, which in principle could be overcome using spin-echo techniques. Theoretical studies suggest this to be challenging due to unavoidable spontaneous emission noise in ensemble-based quantum memories. Here, we demonstrate spin-echo manipulation of a mean spin excitation of 1 in a large solid-state ensemble, generated through storage of a weak optical pulse. After a storage time of about 1 ms we optically read-out the spin excitation with a high signal-to-noise ratio. Our results pave the way for long-duration optical quantum storage using spin-echo techniques for any ensemble-based memory.

Cerebral hemodynamic changes of mild traumatic brain injury at the acute stage.

PubMed

Doshi, Hardik; Wiseman, Natalie; Liu, Jun; Wang, Wentao; Welch, Robert D; O'Neil, Brian J; Zuk, Conor; Wang, Xiao; Mika, Valerie; Szaflarski, Jerzy P; Haacke, E Mark; Kou, Zhifeng

2015-01-01

Mild traumatic brain injury (mTBI) is a significant public health care burden in the United States. However, we lack a detailed understanding of the pathophysiology following mTBI and its relation to symptoms and recovery. With advanced magnetic resonance imaging (MRI), we can investigate brain perfusion and oxygenation in regions known to be implicated in symptoms, including cortical gray matter and subcortical structures. In this study, we assessed 14 mTBI patients and 18 controls with susceptibility weighted imaging and mapping (SWIM) for blood oxygenation quantification. In addition to SWIM, 7 patients and 12 controls had cerebral perfusion measured with arterial spin labeling (ASL). We found increases in regional cerebral blood flow (CBF) in the left striatum, and in frontal and occipital lobes in patients as compared to controls (p = 0.01, 0.03, 0.03 respectively). We also found decreases in venous susceptibility, indicating increases in venous oxygenation, in the left thalamostriate vein and right basal vein of Rosenthal (p = 0.04 in both). mTBI patients had significantly lower delayed recall scores on the standardized assessment of concussion, but neither susceptibility nor CBF measures were found to correlate with symptoms as assessed by neuropsychological testing. The increased CBF combined with increased venous oxygenation suggests an increase in cerebral blood flow that exceeds the oxygen demand of the tissue, in contrast to the regional hypoxia seen in more severe TBI. This may represent a neuroprotective response following mTBI, which warrants further investigation.

Evaluation of chondromalacia of the patella with axial inversion recovery-fast spin-echo imaging.

PubMed

Lee, S H; Suh, J S; Cho, J; Kim, S J; Kim, S J

2001-03-01

The purpose of our study was to assess the accuracy of inversion recovery-fast spin-echo (IR-FSE) imaging for the evaluation of chondromalacia of the patella. Eighty-six patients were included, they underwent magnetic resonance (MR) examination and subsequent knee arthroscopy. Medial and lateral facets of the patella were evaluated separately. Axial images were obtained by using IR-FSE (TR/TE/TI = 3000/25/150 msec; echo train length, 8; 4-mm thickness; 12-cm field of view; 512 x 256 matrix; two, number of excitations) with a 1.5-T MR machine. MR interpretation of chondromalacia was made on the basis of the arthroscopic grading system. Of a total of 172 facets graded, arthroscopy revealed chondromalacia in 14 facets with various grades (G0, 158; G1, 1; G2, 3; G3, 6; G4, 4). Sensitivity, specificity, and accuracy in the chondromalacia grades were 57.1%, 93.0%, and 90.1%, respectively. There was one false-negative case (G4) and 11 false-positive cases (G1, eight; G2, two; G3, one). Sensitivity and specificity corrected by one grade difference were improved to 85.7% and 98.1%, respectively. When cartilage changes were grouped into early (corresponding to grade 1 and 2) and advanced (grade 3 and 4) diseases, sensitivity and specificity of the early and advanced diseases were 75% and 94% and 80% and 99%, respectively. IR-FSE imaging of the knee revealed high specificity but low sensitivity for the evaluation of chondromalacia of the patella.

Patterns of postictal cerebral perfusion in idiopathic generalized epilepsy: a multi-delay multi-parametric arterial spin labelling perfusion MRI study.

PubMed

Chen, Guangxiang; Lei, Du; Ren, Jiechuan; Zuo, Panli; Suo, Xueling; Wang, Danny J J; Wang, Meiyun; Zhou, Dong; Gong, Qiyong

2016-07-04

The cerebral haemodynamic status of idiopathic generalized epilepsy (IGE) is a very complicated process. Little attention has been paid to cerebral blood flow (CBF) alterations in IGE detected by arterial spin labelling (ASL) perfusion magnetic resonance imaging (MRI). However, the selection of an optimal delay time is difficult for single-delay ASL. Multi-delay multi-parametric ASL perfusion MRI overcomes the limitations of single-delay ASL. We applied multi-delay multi-parametric ASL perfusion MRI to investigate the patterns of postictal cerebral perfusion in IGE patients with absence seizures. A total of 21 IGE patients with absence seizures and 24 healthy control subjects were enrolled. IGE patients exhibited prolonged arterial transit time (ATT) in the left superior temporal gyrus. The mean CBF of IGE patients was significantly increased in the left middle temporal gyrus, left parahippocampal gyrus and left fusiform gyrus. Prolonged ATT in the left superior temporal gyrus was negatively correlated with the age at onset in IGE patients. This study demonstrated that cortical dysfunction in the temporal lobe and fusiform gyrus may be related to epileptic activity in IGE patients with absence seizures. This information can play an important role in elucidating the pathophysiological mechanism of IGE from a cerebral haemodynamic perspective.

Perfusion deficits and functional connectivity alterations in patients with post-traumatic stress disorder

NASA Astrophysics Data System (ADS)

Liu, Yang; Li, Baojuan; Zhang, Xi; Zhang, Linchuan; Li, Liang; Lu, Hongbing

2016-03-01

To explore the alteration in cerebral blood flow (CBF) and functional connectivity between survivors with recent onset post-traumatic stress disorder (PTSD) and without PTSD, survived from the same coal mine flood disaster. In this study, a processing pipeline using arterial spin labeling (ASL) sequence was proposed. Considering low spatial resolution of ASL sequence, a linear regression method was firstly used to correct the partial volume (PV) effect for better CBF estimation. Then the alterations of CBF between two groups were analyzed using both uncorrected and PV-corrected CBF maps. Based on altered CBF regions detected from the CBF analysis as seed regions, the functional connectivity abnormities in PTSD patients was investigated. The CBF analysis using PV-corrected maps indicates CBF deficits in the bilateral frontal lobe, right superior frontal gyrus and right corpus callosum of PTSD patients, while only right corpus callosum was identified in uncorrected CBF analysis. Furthermore, the regional CBF of the right superior frontal gyrus exhibits significantly negative correlation with the symptom severity in PTSD patients. The resting-state functional connectivity indicates increased connectivity between left frontal lobe and right parietal lobe. These results indicate that PV-corrected CBF exhibits more subtle perfusion changes and may benefit further perfusion and connectivity analysis. The symptom-specific perfusion deficits and aberrant connectivity in above memory-related regions may be putative biomarkers for recent onset PTSD induced by a single prolonged trauma exposure and help predict the severity of PTSD.

Brain Perfusion and Diffusion Abnormalities in Children Treated for Posterior Fossa Brain Tumors.

PubMed

Li, Matthew D; Forkert, Nils D; Kundu, Palak; Ambler, Cheryl; Lober, Robert M; Burns, Terry C; Barnes, Patrick D; Gibbs, Iris C; Grant, Gerald A; Fisher, Paul G; Cheshier, Samuel H; Campen, Cynthia J; Monje, Michelle; Yeom, Kristen W

2017-06-01

To compare cerebral perfusion and diffusion in survivors of childhood posterior fossa brain tumor with neurologically normal controls and correlate differences with cognitive dysfunction. We analyzed retrospectively arterial spin-labeled cerebral blood flow (CBF) and apparent diffusion coefficient (ADC) in 21 patients with medulloblastoma (MB), 18 patients with pilocytic astrocytoma (PA), and 64 neurologically normal children. We generated ANCOVA models to evaluate treatment effects on the cerebral cortex, thalamus, caudate, putamen, globus pallidus, hippocampus, amygdala, nucleus accumbens, and cerebral white matter at time points an average of 5.7 years after original diagnosis. A retrospective review of patient charts identified 12 patients with neurocognitive data and in whom the relationship between IQ and magnetic resonance imaging variables was assessed for each brain structure. Patients with MB (all treated with surgery, chemotherapy, and radiation) had significantly lower global CBF relative to controls (10%-23% lower, varying by anatomic region, all adjusted P?

Spin-echo Echo-planar Imaging MR Elastography versus Gradient-echo MR Elastography for Assessment of Liver Stiffness in Children and Young Adults Suspected of Having Liver Disease.

PubMed

Serai, Suraj D; Dillman, Jonathan R; Trout, Andrew T

2017-03-01

Purpose To compare two-dimensional (2D) gradient-recalled echo (GRE) and 2D spin-echo (SE) echo-planar imaging (EPI) magnetic resonance (MR) elastography for measurement of hepatic stiffness in pediatric and young adult patients suspected of having liver disease. Materials and Methods In this institutional review board-approved, HIPAA-compliant study, 58 patients underwent both 2D GRE and 2D SE-EPI MR elastography at 1.5 T during separate breath holds. Liver stiffness (mean of means; in kilopascals) was measured by five blinded reviewers. Pooled mean liver stiffness and region-of-interest (ROI) size were compared by using paired t tests. Intraclass correlation coefficients (ICCs) were used to assess agreement between techniques. Respiratory motion artifacts were compared across sequences by using the Fisher exact test. Results Mean patient age was 14.7 years ± 5.2 (standard deviation; age range, 0.7-20.5 years), and 55.2% (32 of 58) of patients were male. Mean liver stiffness was 2.92 kPa ± 1.29 measured at GRE MR elastography and 2.76 kPa ± 1.39 at SE-EPI MR elastography (n = 290; P = .15). Mean ROI sizes were 8495 mm 2 ± 4482 for 2D GRE MR elastography and 15 176 mm 2 ± 7609 for 2D SE-EPI MR elastography (n = 290; P < .001). Agreement was excellent for measured stiffness between five reviewers for both 2D GRE (ICC, 0.97; 95% confidence interval: 0.95, 0.98) and 2D SE-EPI (ICC, 0.98; 95% confidence interval: 0.96, 0.99). Mean ICC (n = 5) for agreement between 2D GRE and 2D SE-EPI MR elastography was 0.93 (range, 0.91-0.95). Moderate or severe breathing artifacts were observed on 27.5% (16 of 58) of 2D GRE images versus 0% 2D SE-EPI images (P < .001). Conclusion There is excellent agreement on measured hepatic stiffness between 2D GRE and 2D SE-EPI MR elastography across multiple reviewers. SE-EPI MR elastography allowed for stiffness measurement across larger areas of the liver and can be performed in a single breath hold. © RSNA, 2016.

Development of a Dedicated Radiotherapy Unit with Real-Time Image Guidance and Motion Management for Accelerated Partial Breast Irradiation

DTIC Science & Technology

2012-08-01

respiratory motions using 4D tagged magnetic resonance imaging ( MRI ) data and 4D high-resolution respiratory-gated CT data respectively. Both...dimensional segmented human anatomy. Medical Physics, 1994. 21(2): p. 299-302. 6. Zubal, I.G., et al. High resolution, MRI -based, segmented...the beam direction. T2-weighted images were acquired after 24 hours with a 3T- MRI scanner using a turbo spin-echo sequence. Imaging parameters were

Accelerated whole brain intracranial vessel wall imaging using black blood fast spin echo with compressed sensing (CS-SPACE).

PubMed

Zhu, Chengcheng; Tian, Bing; Chen, Luguang; Eisenmenger, Laura; Raithel, Esther; Forman, Christoph; Ahn, Sinyeob; Laub, Gerhard; Liu, Qi; Lu, Jianping; Liu, Jing; Hess, Christopher; Saloner, David

2018-06-01

Develop and optimize an accelerated, high-resolution (0.5 mm isotropic) 3D black blood MRI technique to reduce scan time for whole-brain intracranial vessel wall imaging. A 3D accelerated T 1 -weighted fast-spin-echo prototype sequence using compressed sensing (CS-SPACE) was developed at 3T. Both the acquisition [echo train length (ETL), under-sampling factor] and reconstruction parameters (regularization parameter, number of iterations) were first optimized in 5 healthy volunteers. Ten patients with a variety of intracranial vascular disease presentations (aneurysm, atherosclerosis, dissection, vasculitis) were imaged with SPACE and optimized CS-SPACE, pre and post Gd contrast. Lumen/wall area, wall-to-lumen contrast ratio (CR), enhancement ratio (ER), sharpness, and qualitative scores (1-4) by two radiologists were recorded. The optimized CS-SPACE protocol has ETL 60, 20% k-space under-sampling, 0.002 regularization factor with 20 iterations. In patient studies, CS-SPACE and conventional SPACE had comparable image scores both pre- (3.35 ± 0.85 vs. 3.54 ± 0.65, p = 0.13) and post-contrast (3.72 ± 0.58 vs. 3.53 ± 0.57, p = 0.15), but the CS-SPACE acquisition was 37% faster (6:48 vs. 10:50). CS-SPACE agreed with SPACE for lumen/wall area, ER measurements and sharpness, but marginally reduced the CR. In the evaluation of intracranial vascular disease, CS-SPACE provides a substantial reduction in scan time compared to conventional T 1 -weighted SPACE while maintaining good image quality.

Self-Calibrating Wave-Encoded Variable-Density Single-Shot Fast Spin Echo Imaging.

PubMed

Chen, Feiyu; Taviani, Valentina; Tamir, Jonathan I; Cheng, Joseph Y; Zhang, Tao; Song, Qiong; Hargreaves, Brian A; Pauly, John M; Vasanawala, Shreyas S

2018-04-01

It is highly desirable in clinical abdominal MR scans to accelerate single-shot fast spin echo (SSFSE) imaging and reduce blurring due to T 2 decay and partial-Fourier acquisition. To develop and investigate the clinical feasibility of wave-encoded variable-density SSFSE imaging for improved image quality and scan time reduction. Prospective controlled clinical trial. With Institutional Review Board approval and informed consent, the proposed method was assessed on 20 consecutive adult patients (10 male, 10 female, range, 24-84 years). A wave-encoded variable-density SSFSE sequence was developed for clinical 3.0T abdominal scans to enable high acceleration (3.5×) with full-Fourier acquisitions by: 1) introducing wave encoding with self-refocusing gradient waveforms to improve acquisition efficiency; 2) developing self-calibrated estimation of wave-encoding point-spread function and coil sensitivity to improve motion robustness; and 3) incorporating a parallel imaging and compressed sensing reconstruction to reconstruct highly accelerated datasets. Image quality was compared pairwise with standard Cartesian acquisition independently and blindly by two radiologists on a scale from -2 to 2 for noise, contrast, confidence, sharpness, and artifacts. The average ratio of scan time between these two approaches was also compared. A Wilcoxon signed-rank tests with a P value under 0.05 considered statistically significant. Wave-encoded variable-density SSFSE significantly reduced the perceived noise level and improved the sharpness of the abdominal wall and the kidneys compared with standard acquisition (mean scores 0.8, 1.2, and 0.8, respectively, P < 0.003). No significant difference was observed in relation to other features (P = 0.11). An average of 21% decrease in scan time was achieved using the proposed method. Wave-encoded variable-density sampling SSFSE achieves improved image quality with clinically relevant echo time and reduced scan time, thus providing a fast and robust approach for clinical SSFSE imaging. 1 Technical Efficacy: Stage 6 J. Magn. Reson. Imaging 2018;47:954-966. © 2017 International Society for Magnetic Resonance in Medicine.

SU-E-J-224: Using UTE and T1 Weighted Spin Echo Pulse Sequences for MR-Only Treatment Planning; Phantom Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, H; Fatemi, A; Sahgal, A

Purpose: Investigating a new approach in MRI based treatment planning using the combination of (Ultrashort Echo Time) UTE and T1 weighted spin echo pulse sequences to delineate air, bone and water (soft tissues) in generating pseudo CT images comparable with CT. Methods: A gel phantom containing chicken bones, ping pang balls filled with distilled water and air bubbles, was made. It scanned with MRI using UTE and 2D T1W SE pulse sequences with (in plane resolution= 0.53mm, slice thickness= 2 mm) and CT with (in plane resolution= 0.5 mm and slice thickness= 0.75mm) as a ground truth for geometrical accuracy.more » The UTE and T1W SE images were registered with CT using mutual information registration algorithm provided by Philips Pinnacle treatment planning system. The phantom boundaries were detected using Canny edge detection algorithm for CT, and MR images. The bone, air bubbles and water in ping pong balls were segmented from CT images using threshold 300HU, - 950HU and 0HU, respectively. These tissue inserts were automatically segmented from combined UTE and T1W SE images using edge detection and relative intensity histograms of the phantom. The obtained segmentations of air, bone and water inserts were evaluated with those obtained from CT. Results: Bone and air can be clearly differentiated in UTE images comparable to CT. Combining UTE and T1W SE images successfully segmented the air, bone and water. The maximum segmentation differences from combine MRI images (UTE and T1W SE) and CT are within 1.3 mm, 1.1mm for bone, air, respectively. The geometric distortion of UTE sequence is small less than 1 pixel (0.53 mm) of MR image resolution. Conclusion: Our approach indicates that MRI can be used solely for treatment planning and its quality is comparable with CT.« less

Access to long-term optical memories using photon echoes retrieved from electron spins in semiconductor quantum wells

NASA Astrophysics Data System (ADS)

Poltavtsev, S. V.; Langer, L.; Yugova, I. A.; Salewski, M.; Kapitonov, Y. V.; Yakovlev, D. R.; Karczewski, G.; Wojtowicz, T.; Akimov, I. A.; Bayer, M.

2016-10-01

We use spontaneous (two-pulse) and stimulated (three-pulse) photon echoes for studying the coherent evolution of optically excited ensemble of trions which are localized in semiconductor CdTe/CdMgTe quantum well. Application of transverse magnetic field leads to the Larmor precession of the resident electron spins, which shuffles optically induced polarization between optically accessible and inaccessible states. This results in several spectacular phenomena. First, magnetic field induces oscillations of spontaneous photon echo amplitude. Second, in three-pulse excitation scheme, the photon echo decay is extended by several orders of magnitude. In this study, short-lived optical excitation which is created by the first pulse is coherently transferred into a long-lived electron spin state using the second optical pulse. This coherent spin state of electron ensemble persists much longer than any optical excitation in the system, preserving information on initial optical field, which can be retrieved as a photon echo by means of third optical pulse.

Evaluation of intraaxial enhancing brain tumors on magnetic resonance imaging: intraindividual crossover comparison of gadobenate dimeglumine and gadopentetate dimeglumine for visualization and assessment, and implications for surgical intervention.

PubMed

Kuhn, Matthew J; Picozzi, Piero; Maldjian, Joseph A; Schmalfuss, Ilona M; Maravilla, Kenneth R; Bowen, Brian C; Wippold, Franz J; Runge, Val M; Knopp, Michael V; Wolansky, Leo J; Gustafsson, Lars; Essig, Marco; Anzalone, Nicoletta

2007-04-01

The goal in this article was to compare 0.1 mmol/kg doses of gadobenate dimeglumine (Gd-BOPTA) and gadopentetate dimeglumine, also known as gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA), for enhanced magnetic resonance (MR) imaging of intraaxial brain tumors. Eighty-four patients with either intraaxial glioma (47 patients) or metastasis (37 patients) underwent two MR imaging examinations at 1.5 tesla, one with Gd-BOPTA as the contrast agent and the other with Gd-DTPA. The interval between fully randomized contrast medium administrations was 2 to 7 days. The T1-weighted spin echo and T2-weighted fast spin echo images were acquired before administration of contrast agents and T1-weighted spin echo images were obtained after the agents were administered. Acquisition parameters and postinjection acquisition times were identical for the two examinations in each patient. Three experienced readers working in a fully blinded fashion independently evaluated all images for degree and quality of available information (lesion contrast enhancement, lesion border delineation, definition of disease extent, visualization of the lesion's internal structures, global diagnostic preference) and quantitative enhancement (that is, the extent of lesion enhancement after contrast agent administration compared with that seen before its administration [hereafter referred to as percent enhancement], lesion/brain ratio, and contrast/noise ratio). Differences were tested with the Wilcoxon signed-rank test. Reader agreement was assessed using kappa statistics. Significantly better diagnostic information/imaging performance (p < 0.0001, all readers) was obtained with Gd-BOPTA for all visualization end points. Global preference for images obtained with Gd-BOPTA was expressed for 42 (50%), 52 (61.9%), and 56 (66.7%) of 84 patients (readers 1, 2, and 3, respectively) compared with images obtained with Gd-DTPA contrast in four (4.8%), six (7.1%), and three (3.6%) of 84 patients. Similar differences were noted for all other visualization end points. Significantly greater quantitative contrast enhancement (p < 0.04) was noted after administration of Gd-BOPTA. Reader agreement was good (kappa > 0.4). Lesion visualization, delineation, definition, and contrast enhancement are significantly better after administration of 0.1 mmol/kg Gd-BOPTA, potentially allowing better surgical planning and follow up and improved disease management.

Absolute Cerebral Blood Flow Infarction Threshold for 3-Hour Ischemia Time Determined with CT Perfusion and 18F-FFMZ-PET Imaging in a Porcine Model of Cerebral Ischemia

PubMed Central

Cockburn, Neil; Kovacs, Michael

2016-01-01

CT Perfusion (CTP) derived cerebral blood flow (CBF) thresholds have been proposed as the optimal parameter for distinguishing the infarct core prior to reperfusion. Previous threshold-derivation studies have been limited by uncertainties introduced by infarct expansion between the acute phase of stroke and follow-up imaging, or DWI lesion reversibility. In this study a model is proposed for determining infarction CBF thresholds at 3hr ischemia time by comparing contemporaneously acquired CTP derived CBF maps to 18F-FFMZ-PET imaging, with the objective of deriving a CBF threshold for infarction after 3 hours of ischemia. Endothelin-1 (ET-1) was injected into the brain of Duroc-Cross pigs (n = 11) through a burr hole in the skull. CTP images were acquired 10 and 30 minutes post ET-1 injection and then every 30 minutes for 150 minutes. 370 MBq of 18F-FFMZ was injected ~120 minutes post ET-1 injection and PET images were acquired for 25 minutes starting ~155–180 minutes post ET-1 injection. CBF maps from each CTP acquisition were co-registered and converted into a median CBF map. The median CBF map was co-registered to blood volume maps for vessel exclusion, an average CT image for grey/white matter segmentation, and 18F-FFMZ-PET images for infarct delineation. Logistic regression and ROC analysis were performed on infarcted and non-infarcted pixel CBF values for each animal that developed infarct. Six of the eleven animals developed infarction. The mean CBF value corresponding to the optimal operating point of the ROC curves for the 6 animals was 12.6 ± 2.8 mL·min-1·100g-1 for infarction after 3 hours of ischemia. The porcine ET-1 model of cerebral ischemia is easier to implement then other large animal models of stroke, and performs similarly as long as CBF is monitored using CTP to prevent reperfusion. PMID:27347877

Diffusion weighted imaging: a comprehensive evaluation of a fast spin echo DWI sequence with BLADE (PROPELLER) k-space sampling at 3 T, using a 32-channel head coil in acute brain ischemia.

PubMed

Attenberger, Ulrike I; Runge, Val M; Stemmer, Alto; Williams, Kenneth D; Naul, L Gill; Michaely, Henrik J; Schoenberg, Stefan O; Reiser, Maximilian F; Wintersperger, Bernd J

2009-10-01

To evaluate the signal-to-noise ratio (SNR) and diagnostic quality of diffusion weighted imaging (DWI) using a fast spin echo (FSE) sequence with BLADE k-space trajectory at 3 T in combination with a 32-channel head coil. The scan was compared with a standard spin echo (SE) echo-planar imaging (EPI) DWI and a high resolution SE EPI DWI sequence. Fourteen patients with acute brain ischemia were included in this Institutional Review Board approved study. All patients were evaluated with 3 different image sequences, using a 3 T scanner and a 32-channel head coil: (a) a standard SE EPI DWI (matrix size 192 x 192), (b) a high resolution SE EPI DWI (matrix size of 256 x 256) and (c) a FSE DWI BLADE (matrix size 192 x 192). The SNR of the 3 scans was compared in 10 healthy volunteers by a paired student t test. Image quality was evaluated with 4 dedicated questions in a blinded read: (1) The scans were ranked in terms of bulk susceptibility artifact. (2) The scan preference for diagnosis of any diffusion abnormality that might occur and (3) the preference for visualization of the diffusion abnormality actually present was determined. (4) The influence of bulk susceptibility on image evaluation for the diffusion abnormality present was assessed. For visualization of the diffusion abnormality present, BLADE DWI was the scan sequence preferred most by both readers (reader 1: 41.7%, reader 2: 35.7%). For visualization of any diffusion abnormality present, BLADE DWI was the preferred scan in 13 of 14 cases for reader 1 (93%) and in 11 of 14 cases for reader 2 (78.6%). No high resolution SE EPI DWI scan was rated best by reader 1. Reader 2 rated the high resolution SE EPI DWI scan superior in only 1 of 56 judgments. The standard EPI DWI sequence (21.8 +/- 5.3) had in comparison to the high resolution EPI DWI (11.9 +/- 2.6) and the BLADE DWI scans (11.3 +/- 3.8) significantly higher SNR mean values. Our preliminary data demonstrates the feasibility of a FSE EPI DWI scan with radial-like k-space sampling, using a 32-channel coil at 3 T in acute brain ischemia. The BLADE DWI was the preferred scan for the detection of acute diffusion abnormalities because of the lack of bulk susceptibility artifacts.

Musculoskeletal MRI at 3.0 T and 7.0 T: a comparison of relaxation times and image contrast.

PubMed

Jordan, Caroline D; Saranathan, Manojkumar; Bangerter, Neal K; Hargreaves, Brian A; Gold, Garry E

2013-05-01

The purpose of this study was to measure and compare the relaxation times of musculoskeletal tissues at 3.0 T and 7.0 T, and to use these measurements to select appropriate parameters for musculoskeletal protocols at 7.0 T. We measured the T₁ and T₂ relaxation times of cartilage, muscle, synovial fluid, bone marrow and subcutaneous fat at both 3.0 T and 7.0 T in the knees of five healthy volunteers. The T₁ relaxation times were measured using a spin-echo inversion recovery sequence with six inversion times. The T₂ relaxation times were measured using a spin-echo sequence with seven echo times. The accuracy of both the T₁ and T₂ measurement techniques was verified in phantoms at both magnetic field strengths. We used the measured relaxation times to help design 7.0 T musculoskeletal protocols that preserve the favorable contrast characteristics of our 3.0 T protocols, while achieving significantly higher resolution at higher SNR efficiency. The T₁ relaxation times in all tissues at 7.0 T were consistently higher than those measured at 3.0 T, while the T₂ relaxation times at 7.0 T were consistently lower than those measured at 3.0 T. The measured relaxation times were used to help develop high resolution 7.0 T protocols that had similar fluid-to-cartilage contrast to that of the standard clinical 3.0 T protocols for the following sequences: proton-density-weighted fast spin-echo (FSE), T₂-weighted FSE, and 3D-FSE-Cube. The T₁ and T₂ changes were within the expected ranges. Parameters for musculoskeletal protocols at 7.0 T can be optimized based on these values, yielding improved resolution in musculoskeletal imaging with similar contrast to that of standard 3.0 T clinical protocols. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Brain magnetic resonance imaging CO2 stress testing in adolescent postconcussion syndrome.

PubMed

Mutch, W Alan C; Ellis, Michael J; Ryner, Lawrence N; Ruth Graham, M; Dufault, Brenden; Gregson, Brian; Hall, Thomas; Bunge, Martin; Essig, Marco; Fisher, Joseph A; Duffin, James; Mikulis, David J

2016-09-01

OBJECT A neuroimaging assessment tool to visualize global and regional impairments in cerebral blood flow (CBF) and cerebrovascular responsiveness in individual patients with concussion remains elusive. Here the authors summarize the safety, feasibility, and results of brain CO2 stress testing in adolescents with postconcussion syndrome (PCS) and healthy controls. METHODS This study was approved by the Biomedical Research Ethics Board at the University of Manitoba. Fifteen adolescents with PCS and 17 healthy control subjects underwent anatomical MRI, pseudo-continuous arterial spin labeling MRI, and brain stress testing using controlled CO2 challenge and blood oxygen level-dependent (BOLD) MRI. Post hoc processing was performed using statistical parametric mapping to determine voxel-by-voxel regional resting CBF and cerebrovascular responsiveness of the brain to the CO2 stimulus (increase in BOLD signal) or the inverse (decrease in BOLD signal). Receiver operating characteristic (ROC) curves were generated to compare voxel counts categorized by control (0) or PCS (1). RESULTS Studies were well tolerated without any serious adverse events. Anatomical MRI was normal in all study participants. No differences in CO2 stimuli were seen between the 2 participant groups. No group differences in global mean CBF were detected between PCS patients and healthy controls. Patient-specific differences in mean regional CBF and CO2 BOLD responsiveness were observed in all PCS patients. The ROC curve analysis for brain regions manifesting a voxel response greater than and less than the control atlas (that is, abnormal voxel counts) produced an area under the curve of 0.87 (p < 0.0001) and 0.80 (p = 0.0003), respectively, consistent with a clinically useful predictive model. CONCLUSIONS Adolescent PCS is associated with patient-specific abnormalities in regional mean CBF and BOLD cerebrovascular responsiveness that occur in the setting of normal global resting CBF. Future prospective studies are warranted to examine the utility of brain MRI CO2 stress testing in the longitudinal assessment of acute sports-related concussion and PCS.

Magnetic resonance imaging of the subthalamic nucleus for deep brain stimulation.

PubMed

Chandran, Arjun S; Bynevelt, Michael; Lind, Christopher R P

2016-01-01

The subthalamic nucleus (STN) is one of the most important stereotactic targets in neurosurgery, and its accurate imaging is crucial. With improving MRI sequences there is impetus for direct targeting of the STN. High-quality, distortion-free images are paramount. Image reconstruction techniques appear to show the greatest promise in balancing the issue of geometrical distortion and STN edge detection. Existing spin echo- and susceptibility-based MRI sequences are compared with new image reconstruction methods. Quantitative susceptibility mapping is the most promising technique for stereotactic imaging of the STN.

The Effects of Acutely Administered 3,4-Methylenedioxymethamphetamine on Spontaneous Brain Function in Healthy Volunteers Measured with Arterial Spin Labeling and Blood Oxygen Level–Dependent Resting State Functional Connectivity

PubMed Central

Carhart-Harris, Robin L.; Murphy, Kevin; Leech, Robert; Erritzoe, David; Wall, Matthew B.; Ferguson, Bart; Williams, Luke T.J.; Roseman, Leor; Brugger, Stefan; De Meer, Ineke; Tanner, Mark; Tyacke, Robin; Wolff, Kim; Sethi, Ajun; Bloomfield, Michael A.P.; Williams, Tim M.; Bolstridge, Mark; Stewart, Lorna; Morgan, Celia; Newbould, Rexford D.; Feilding, Amanda; Curran, H. Val; Nutt, David J.

2015-01-01

Background The compound 3,4-methylenedioxymethamphetamine (MDMA) is a potent monoamine releaser that produces an acute euphoria in most individuals. Methods In a double-blind, placebo-controlled, balanced-order study, MDMA was orally administered to 25 physically and mentally healthy individuals. Arterial spin labeling and seed-based resting state functional connectivity (RSFC) were used to produce spatial maps displaying changes in cerebral blood flow (CBF) and RSFC after MDMA administration. Participants underwent two arterial spin labeling and two blood oxygen level–dependent scans in a 90-minute scan session; MDMA and placebo study days were separated by 1 week. Results Marked increases in positive mood were produced by MDMA. Decreased CBF only was observed after MDMA, and this was localized to the right medial temporal lobe (MTL), thalamus, inferior visual cortex, and the somatosensory cortex. Decreased CBF in the right amygdala and hippocampus correlated with ratings of the intensity of global subjective effects of MDMA. The RSFC results complemented the CBF results, with decreases in RSFC between midline cortical regions, the medial prefrontal cortex, and MTL regions, and increases between the amygdala and hippocampus. There were trend-level correlations between these effects and ratings of intense and positive subjective effects. Conclusions The MTLs appear to be specifically implicated in the mechanism of action of MDMA, but further work is required to elucidate how the drug’s characteristic subjective effects arise from its modulation of spontaneous brain activity. PMID:24495461

Assessment of cerebral venous sinus thrombosis using T2*-weighted gradient echo magnetic resonance imaging sequences

PubMed Central

Bidar, Fatemeh; Faeghi, Fariborz; Ghorbani, Askar

2016-01-01

Background: The purpose of this study is to demonstrate the advantages of gradient echo (GRE) sequences in the detection and characterization of cerebral venous sinus thrombosis compared to conventional magnetic resonance sequences. Methods: A total of 17 patients with cerebral venous thrombosis (CVT) were evaluated using different magnetic resonance imaging (MRI) sequences. The MRI sequences included T1-weighted spin echo (SE) imaging, T*2-weighted turbo SE (TSE), fluid attenuated inversion recovery (FLAIR), T*2-weighted conventional GRE, and diffusion weighted imaging (DWI). MR venography (MRV) images were obtained as the golden standard. Results: Venous sinus thrombosis was best detectable in T*2-weighted conventional GRE sequences in all patients except in one case. Venous thrombosis was undetectable in DWI. T*2-weighted GRE sequences were superior to T*2-weighted TSE, T1-weighted SE, and FLAIR. Enhanced MRV was successful in displaying the location of thrombosis. Conclusion: T*2-weighted conventional GRE sequences are probably the best method for the assessment of cerebral venous sinus thrombosis. The mentioned method is non-invasive; therefore, it can be employed in the clinical evaluation of cerebral venous sinus thrombosis. PMID:27326365

Operating Spin Echo in the Quantum Regime for an Atomic-Ensemble Quantum Memory

NASA Astrophysics Data System (ADS)

Rui, Jun; Jiang, Yan; Yang, Sheng-Jun; Zhao, Bo; Bao, Xiao-Hui; Pan, Jian-Wei

2015-09-01

Spin echo is a powerful technique to extend atomic or nuclear coherence times by overcoming the dephasing due to inhomogeneous broadenings. However, there are disputes about the feasibility of applying this technique to an ensemble-based quantum memory at the single-quanta level. In this experimental study, we find that noise due to imperfections of the rephasing pulses has both intense superradiant and weak isotropic parts. By properly arranging the beam directions and optimizing the pulse fidelities, we successfully manage to operate the spin echo technique in the quantum regime by observing nonclassical photon-photon correlations as well as the quantum behavior of retrieved photons. Our work for the first time demonstrates the feasibility of harnessing the spin echo method to extend the lifetime of ensemble-based quantum memories at the single-quanta level.

Correlated displacement-T2 MRI by means of a Pulsed Field Gradient-Multi Spin Echo Method.

PubMed

Windt, Carel W; Vergeldt, Frank J; Van As, Henk

2007-04-01

A method for correlated displacement-T2 imaging is presented. A Pulsed Field Gradient-Multi Spin Echo (PFG-MSE) sequence is used to record T2 resolved propagators on a voxel-by-voxel basis, making it possible to perform single voxel correlated displacement-T2 analyses. In spatially heterogeneous media the method thus gives access to sub-voxel information about displacement and T2 relaxation. The sequence is demonstrated using a number of flow conducting model systems: a tube with flowing water of variable intrinsic T2's, mixing fluids of different T2's in an "X"-shaped connector, and an intact living plant. PFG-MSE can be applied to yield information about the relation between flow, pore size and exchange behavior, and can aid volume flow quantification by making it possible to correct for T2 relaxation during the displacement labeling period Delta in PFG displacement imaging methods. Correlated displacement-T2 imaging can be of special interest for a number of research subjects, such as the flow of liquids and mixtures of liquids or liquids and solids moving through microscopic conduits of different sizes (e.g., plants, porous media, bioreactors, biomats).

Non-destructive analysis of sensory traits of dry-cured loins by MRI-computer vision techniques and data mining.

PubMed

Caballero, Daniel; Antequera, Teresa; Caro, Andrés; Ávila, María Del Mar; G Rodríguez, Pablo; Perez-Palacios, Trinidad

2017-07-01

Magnetic resonance imaging (MRI) combined with computer vision techniques have been proposed as an alternative or complementary technique to determine the quality parameters of food in a non-destructive way. The aim of this work was to analyze the sensory attributes of dry-cured loins using this technique. For that, different MRI acquisition sequences (spin echo, gradient echo and turbo 3D), algorithms for MRI analysis (GLCM, NGLDM, GLRLM and GLCM-NGLDM-GLRLM) and predictive data mining techniques (multiple linear regression and isotonic regression) were tested. The correlation coefficient (R) and mean absolute error (MAE) were used to validate the prediction results. The combination of spin echo, GLCM and isotonic regression produced the most accurate results. In addition, the MRI data from dry-cured loins seems to be more suitable than the data from fresh loins. The application of predictive data mining techniques on computational texture features from the MRI data of loins enables the determination of the sensory traits of dry-cured loins in a non-destructive way. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Externally Calibrated Parallel Imaging for 3D Multispectral Imaging Near Metallic Implants Using Broadband Ultrashort Echo Time Imaging

PubMed Central

Wiens, Curtis N.; Artz, Nathan S.; Jang, Hyungseok; McMillan, Alan B.; Reeder, Scott B.

2017-01-01

Purpose To develop an externally calibrated parallel imaging technique for three-dimensional multispectral imaging (3D-MSI) in the presence of metallic implants. Theory and Methods A fast, ultrashort echo time (UTE) calibration acquisition is proposed to enable externally calibrated parallel imaging techniques near metallic implants. The proposed calibration acquisition uses a broadband radiofrequency (RF) pulse to excite the off-resonance induced by the metallic implant, fully phase-encoded imaging to prevent in-plane distortions, and UTE to capture rapidly decaying signal. The performance of the externally calibrated parallel imaging reconstructions was assessed using phantoms and in vivo examples. Results Phantom and in vivo comparisons to self-calibrated parallel imaging acquisitions show that significant reductions in acquisition times can be achieved using externally calibrated parallel imaging with comparable image quality. Acquisition time reductions are particularly large for fully phase-encoded methods such as spectrally resolved fully phase-encoded three-dimensional (3D) fast spin-echo (SR-FPE), in which scan time reductions of up to 8 min were obtained. Conclusion A fully phase-encoded acquisition with broadband excitation and UTE enabled externally calibrated parallel imaging for 3D-MSI, eliminating the need for repeated calibration regions at each frequency offset. Significant reductions in acquisition time can be achieved, particularly for fully phase-encoded methods like SR-FPE. PMID:27403613

Muscle fat fraction in neuromuscular disorders: dual-echo dual-flip-angle spoiled gradient-recalled MR imaging technique for quantification--a feasibility study.

PubMed

Gaeta, Michele; Scribano, Emanuele; Mileto, Achille; Mazziotti, Silvio; Rodolico, Carmelo; Toscano, Antonio; Settineri, Nicola; Ascenti, Giorgio; Blandino, Alfredo

2011-05-01

To prospectively evaluate the muscle fat fraction (MFF) measured with dual-echo dual-flip-angle spoiled gradient-recalled acquisition in the steady state (SPGR) magnetic resonance (MR) imaging technique by using muscle biopsy as the reference standard. After ethics approval, written informed consent from all patients was obtained. Twenty-seven consecutive patients, evaluated at the Neuromuscular Disorders Center with a possible diagnosis of neuromuscular disorder, were prospectively studied with MR imaging of the lower extremities to quantify muscle fatty infiltration by means of MFF calculation. Spin-density- and T1-weighted fast SPGR in-phase and opposed-phase dual-echo sequences were performed, respectively, with 20° and 80° flip angles. Round regions of interest were drawn by consensus on selected MR sections corresponding to anticipated biopsy sites. These were marked on the patient's skin with a pen by using the infrared spider light of the system, and subsequent muscle biopsy was performed. MR images with regions of interest were stored on a secondary console where the MFF calculation was performed by another radiologist blinded to the biopsy results. MFFs calculated with dual-echo dual-flip-angle SPGR MR imaging and biopsy were compared by using a paired t test, Pearson correlation coefficient, and Bland-Altman plots. P value of < .05 was considered to indicate a statistically significant difference. The mean MFFs obtained with dual-echo dual-flip-angle SPGR MR imaging and biopsy were 20.3% (range, 1.7%-45.1%) and 20.6% (range, 3%-46.1%), respectively. The mean difference, standard deviation of the difference, and t value were -0.3, 1.3, and -1.3 (P > .2), respectively. The Pearson correlation coefficient was 0.995; with the Bland-Altman method, all data points were within the ± 2 SDs limits of agreement. The results show that dual-echo dual-flip-angle SPGR MR imaging technique provides reliable calculation of MFF, consistent with biopsy measurements. RSNA, 2011

Altered Cerebral Blood Flow Covariance Network in Schizophrenia.

PubMed

Liu, Feng; Zhuo, Chuanjun; Yu, Chunshui

2016-01-01

Many studies have shown abnormal cerebral blood flow (CBF) in schizophrenia; however, it remains unclear how topological properties of CBF network are altered in this disorder. Here, arterial spin labeling (ASL) MRI was employed to measure resting-state CBF in 96 schizophrenia patients and 91 healthy controls. CBF covariance network of each group was constructed by calculating across-subject CBF covariance between 90 brain regions. Graph theory was used to compare intergroup differences in global and nodal topological measures of the network. Both schizophrenia patients and healthy controls had small-world topology in CBF covariance networks, implying an optimal balance between functional segregation and integration. Compared with healthy controls, schizophrenia patients showed reduced small-worldness, normalized clustering coefficient and local efficiency of the network, suggesting a shift toward randomized network topology in schizophrenia. Furthermore, schizophrenia patients exhibited altered nodal centrality in the perceptual-, affective-, language-, and spatial-related regions, indicating functional disturbance of these systems in schizophrenia. This study demonstrated for the first time that schizophrenia patients have disrupted topological properties in CBF covariance network, which provides a new perspective (efficiency of blood flow distribution between brain regions) for understanding neural mechanisms of schizophrenia.

Should the orthodontic brackets always be removed prior to magnetic resonance imaging (MRI)?

PubMed Central

Poorsattar-Bejeh Mir, Arash; Rahmati-Kamel, Manouchehr

2015-01-01

Request for temporary removal of orthodontic appliances due to medical conditions that require magnetic resonance (MR) imaging is not uncommon in daily practice in the field of orthodontics. This may be at the expense of time and cost. Metal Orthodontic appliances cause more signal loss and image distortion as compared to ceramic and titanium ones. Stainless steel and large brackets in addition to the oriented miniscrews in relation to the axis of magnetic field may cause severe signal loss and image distortion. Moreover, gradient echo and frequency-selective fat saturation MR protocols are more susceptible to metal artifacts. The spin echo and fat-suppression protocols, low magnetic field strength (e.g., 1.5 Tesla vs. 3 Tesla), small field of view, high-resolution matrix, thin slice, increased echo train length and increased receiver band width could be applied to lessen the metal artifacts in MR images. The larger the distance between an appliance and desired location to be imaged, the lower the distortion and signal loss. Decision to remove brackets should be made based on its composition and desired anatomic location. In this review, first the principles of MR imaging are introduced (Part-I) and then the interactions of orthodontic appliances and magnetic field are farther discussed (Part-II). PMID:27195213

Enduring disturbances in regional cerebral blood flow and brain oxygenation at 24 h after asphyxial cardiac arrest in developing rats.

PubMed

Foley, Lesley M; Clark, Robert S B; Vazquez, Alberto L; Hitchens, T Kevin; Alexander, Henry; Ho, Chien; Kochanek, Patrick M; Manole, Mioara D

2017-01-01

Disturbances in cerebral blood flow (CBF) and brain oxygenation (PbO 2 ) are present early after pediatric cardiac arrest (CA). CBF-targeted therapies improved neurological outcome in our CA model. To assess the therapeutic window for CBF- and PbO 2 -targeted therapies, we propose to determine if CBF and PbO 2 disturbances persist at 24 h after experimental pediatric CA. Regional CBF and PbO 2 were measured at 24 h after asphyxial CA in immature rats (n = 26, 6-8/group) using arterial spin label MRI and tissue electrodes, respectively. In all regions but the thalamus, CBF recovered to sham values by 24 h; thalamic CBF was >32% higher after CA vs. sham. PbO 2 values at 24 h after CA in the cortex and thalamus were similar to shams in rats who received supplemental oxygen, however, on room air, cortical PbO 2 was lower after CA vs. shams. CBF remains increased in the thalamus at 24 h after CA and PbO 2 is decreased to hypoxic levels in cortex at 24 h after CA in rats who do not receive supplemental oxygen. Given the enduring disturbances in this model and the lack of routine CBF or PbO 2 monitoring in patients, our data suggest the need for clinical correlation.

Comparison of two-dimensional fast spin echo T2 weighted sequences and three-dimensional volume isotropic T2 weighted fast spin echo (VISTA) MRI in the evaluation of triangular fibrocartilage of the wrist.

PubMed

Park, Hee Jin; Lee, So Yeon; Kang, Kyung A; Kim, Eun Young; Shin, Hun Kyu; Park, Se Jin; Park, Jai Hyung; Kim, Eugene

2018-04-01

To compare image quality of three-dimensional volume isotropic T 2 weighted fast spin echo (3D VISTA) and two-dimensional (2D) T 2 weighted images (T2WI) for evaluation of triangular fibrocartilage (TFC) and to investigate whether 3D VISTA can replace 2D T 2 WI in evaluating TFC injury. This retrospective study included 69 patients who received wrist MRIs using both 2D T 2 WI and 3D VISTA techniques for assessment of wrist pathology, including TFC injury. Two radiologists measured the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) of the two sequences. The anatomical identification score and diagnostic performance were independently assessed by two interpreters. The diagnostic abilities of 3D VISTA and 2D T 2 WI were analysed by sensitivity, specificity and accuracy for diagnosing TFC injury using surgically or clinically confirmed diagnostic reference standards. 17 cases (25%) were classified as having TFC injury. 2 cases (12%) were diagnosed surgically, and 15 cases (88%) were diagnosed by physical examination. 52 cases (75%) were diagnosed as having intact TFC. 8 of these cases (15%) were surgically confirmed, while the others were diagnosed by physical examination and clinical findings. The 3D VISTA images had significantly higher SNR and CNR values for the TFC than 2D T 2 WI images. The scores of 3D VISTA's total length, full width and sharpness were similar to those of 2D T 2 WI. We were unable to find a significant difference between 3D VISTA and 2D T 2 WI in the ability to diagnose TFC injury. 3D VISTA image quality is similar to that of 2D T 2 WI for TFC evaluation and is also excellent for tissue contrast. 3D VISTA can replace 2D images in TFC injury assessment. Advances in knowledge: 3D VISTA image quality is similar to that of 2D T 2 WI for TFC evaluation and is also excellent for tissue contrast. 3D VISTA can replace 2D images in TFC injury assessment.

Quantifying regional cerebral blood flow by N-isopropyl-P-[I-123]iodoamphetamine (IMP) using a ring type single-photon emission computed tomography system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takahashi, N.; Odano, I.; Ohkubo, M.

1994-05-01

We developed a more accurate quantitative measurement of regional cerebral blood flow (rCBF) with the microsphere model using N-isopropyl-p-[I-123] iodoamphetamine (IMP) and a ring type single photon emission computed tomography (SPECT) system. SPECT studies were performed in 17 patients with brain diseases. A dose of 222 MBq (6 mCi) of [I-123]IMP was injected i.v., at the same time a 5 min period of arterial blood withdrawal was begun. SPECT data were acquired from 25 min to 60 min after tracer injection. For obtaining the brain activity concentration at 5 min after IMP injection, total brain counts collections and one minutemore » period short time SPECT studies were performed at 5, 20, and 60 min. Measurement of the values of rCBF was calculated using short time SPECT images at 5 min (rCBF), static SPECT images corrected with total cerebral counts (rCBF{sub Ct}.) and those corrected with reconstructed counts on short time SPECT images (rCBF{sub Cb}). There was a good relationship (r=0.69) between rCBF and rCBF{sub Ct}, however, rCBF{sub Ct} tends to be underestimated in high flow areas and overestimated in low flow areas. There was better relationship between rCBF and rCBF{sub Cb}(r=0.92). The overestimation and underestimation shown in rCBF{sub Ct} was considered to be due to the correction of reconstructed counts using a total cerebral time activity curve, because of the kinetic behavior of [I-123]IMP was different in each region. We concluded that more accurate rCBF values could be obtained using the regional time activity curves.« less

Histological correlation of 7 T multi-parametric MRI performed in ex-vivo Achilles tendon.

PubMed

Juras, Vladimir; Apprich, Sebastian; Pressl, Christina; Zbyn, Stefan; Szomolanyi, Pavol; Domayer, Stephan; Hofstaetter, Jochen G; Trattnig, Siegfried

2013-05-01

The goal of this in vitro validation study was to investigate the feasibility of biochemical MRI techniques, such as sodium imaging, T₂ mapping, fast imaging with steady state precession (FISP), and reversed FISP (PSIF), as potential markers for collagen, glycosaminoglycan and water content in the Achilles tendon. Five fresh cadaver ankles acquired from a local anatomy department were used in the study. To acquire a sodium signal from the Achilles tendon, a 3D-gradient-echo sequence, optimized for sodium imaging, was used with TE=7.71 ms and TR=17 ms. The T₂ relaxation times were obtained using a multi-echo, spin-echo technique with a repetition time (TR) of 1200 ms and six echo times. A 3D, partially balanced, steady-state gradient echo pulse sequence was used to acquire FISP and PSIF images, with TR/TE=6.96/2.46 ms. MRI parameters were correlated with each other, as well as with histologically assessed glycosaminoglycan and water content in cadaver Achilles tendons. The highest relevant Pearson correlation coefficient was found between sodium SNR and glycosaminoglycan content (r=0.71, p=0.007). Relatively high correlation was found between the PSIF signal and T2 values (r=0.51, p=0.036), and between the FISP signal and T₂ values (r=0.56, p=0.047). Other correlations were found to be below the moderate level. This study demonstrated the feasibility of progressive biochemical MRI methods for the imaging of the AT. A GAG-specific, contrast-free method (sodium imaging), as well as collagen- and water-sensitive methods (T₂ mapping, FISP, PSIF), may be used in fast-relaxing tissues, such as tendons, in reasonable scan times. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Propagation of error from parameter constraints in quantitative MRI: Example application of multiple spin echo T2 mapping.

PubMed

Lankford, Christopher L; Does, Mark D

2018-02-01

Quantitative MRI may require correcting for nuisance parameters which can or must be constrained to independently measured or assumed values. The noise and/or bias in these constraints propagate to fitted parameters. For example, the case of refocusing pulse flip angle constraint in multiple spin echo T 2 mapping is explored. An analytical expression for the mean-squared error of a parameter of interest was derived as a function of the accuracy and precision of an independent estimate of a nuisance parameter. The expression was validated by simulations and then used to evaluate the effects of flip angle (θ) constraint on the accuracy and precision of T⁁2 for a variety of multi-echo T 2 mapping protocols. Constraining θ improved T⁁2 precision when the θ-map signal-to-noise ratio was greater than approximately one-half that of the first spin echo image. For many practical scenarios, constrained fitting was calculated to reduce not just the variance but the full mean-squared error of T⁁2, for bias in θ⁁≲6%. The analytical expression derived in this work can be applied to inform experimental design in quantitative MRI. The example application to T 2 mapping provided specific cases, depending on θ⁁ accuracy and precision, in which θ⁁ measurement and constraint would be beneficial to T⁁2 variance or mean-squared error. Magn Reson Med 79:673-682, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Correction of geometric distortion in Propeller echo planar imaging using a modified reversed gradient approach.

PubMed

Chang, Hing-Chiu; Chuang, Tzu-Chao; Lin, Yi-Ru; Wang, Fu-Nien; Huang, Teng-Yi; Chung, Hsiao-Wen

2013-04-01

This study investigates the application of a modified reversed gradient algorithm to the Propeller-EPI imaging method (periodically rotated overlapping parallel lines with enhanced reconstruction based on echo-planar imaging readout) for corrections of geometric distortions due to the EPI readout. Propeller-EPI acquisition was executed with 360-degree rotational coverage of the k-space, from which the image pairs with opposite phase-encoding gradient polarities were extracted for reversed gradient geometric and intensity corrections. The spatial displacements obtained on a pixel-by-pixel basis were fitted using a two-dimensional polynomial followed by low-pass filtering to assure correction reliability in low-signal regions. Single-shot EPI images were obtained on a phantom, whereas high spatial resolution T2-weighted and diffusion tensor Propeller-EPI data were acquired in vivo from healthy subjects at 3.0 Tesla, to demonstrate the effectiveness of the proposed algorithm. Phantom images show success of the smoothed displacement map concept in providing improvements of the geometric corrections at low-signal regions. Human brain images demonstrate prominently superior reconstruction quality of Propeller-EPI images with modified reversed gradient corrections as compared with those obtained without corrections, as evidenced from verification against the distortion-free fast spin-echo images at the same level. The modified reversed gradient method is an effective approach to obtain high-resolution Propeller-EPI images with substantially reduced artifacts.

Discrimination between patients with mild Alzheimer's disease and healthy subjects based on cerebral blood flow images of the lateral views in xenon-enhanced computed tomography.

PubMed

Sase, Shigeru; Yamamoto, Homaro; Kawashima, Ena; Tan, Xin; Sawa, Yutaka

2018-01-01

Quantitative cerebral blood flow (CBF) measurement is expected to help early detection of functional abnormalities caused by Alzheimer's disease (AD) and enable AD treatment to begin in its early stages. Recently, a technique of layer analysis was reported that allowed CBF to be analyzed from the outer to inner layers of the brain. The aim of this work was to develop methods for discriminating between patients with mild AD and healthy subjects based on CBF images of the lateral views created with the layer analysis technique in xenon-enhanced computed tomography. Xenon-enhanced computed tomography using a wide-volume CT was performed on 17 patients with mild AD aged 75 or older and on 15 healthy age-matched volunteers. For each subject, we created CBF images of the right and left lateral views with a depth of 10-15 mm from the surface of the brain. Ten circular regions of interest (ROI) were placed on each image, and CBF was calculated for each ROI. We determined discriminant ROI that had CBF that could be used to differentiate between the AD and volunteer groups. AD patients' CBF range (mean - SD to mean + SD) and healthy volunteers' CBF range (mean - SD to mean + SD) were obtained for each ROI. Receiver-operator curves were created to identify patients with AD for each of the discriminant ROI and for the AD patients' and healthy volunteers' CBF ranges. We selected an ROI on both the right and left temporal lobes as the discriminant ROI. Areas under the receiver-operator curve were 93.3% using the ROI on the right temporal lobe, 95.3% using the ROI on the left temporal lobe, and 92.4% using the AD patients' and healthy volunteers' CBF ranges. We could effectively discriminate between patients with mild AD and healthy subjects using ROI placed on CBF images of the lateral views in xenon-enhanced computed tomography. © 2017 Japanese Psychogeriatric Society.

Cerebral Blood Flow during Rest Associates with General Intelligence and Creativity

PubMed Central

Takeuchi, Hikaru; Taki, Yasuyuki; Hashizume, Hiroshi; Sassa, Yuko; Nagase, Tomomi; Nouchi, Rui; Kawashima, Ryuta

2011-01-01

Recently, much scientific attention has been focused on resting brain activity and its investigation through such methods as the analysis of functional connectivity during rest (the temporal correlation of brain activities in different regions). However, investigation of the magnitude of brain activity during rest has focused on the relative decrease of brain activity during a task, rather than on the absolute resting brain activity. It is thus necessary to investigate the association between cognitive factors and measures of absolute resting brain activity, such as cerebral blood flow (CBF), during rest (rest-CBF). In this study, we examined this association using multiple regression analyses. Rest-CBF was the dependent variable and the independent variables included two essential components of cognitive functions, psychometric general intelligence and creativity. CBF was measured using arterial spin labeling and there were three analyses for rest-CBF; namely mean gray matter rest-CBF, mean white matter rest-CBF, and regional rest-CBF. The results showed that mean gray and white matter rest-CBF were significantly and positively correlated with individual psychometric intelligence. Furthermore, mean white matter rest-CBF was significantly and positively correlated with creativity. After correcting the effect of mean gray matter rest-CBF the significant and positive correlation between regional rest-CBF in the perisylvian anatomical cluster that includes the left superior temporal gyrus and insula and individual psychometric intelligence was found. Also, regional rest-CBF in the precuneus was significantly and negatively correlated with individual creativity. Significance of these results of regional rest-CBF did not change when the effect of regional gray matter density was corrected. The findings showed mean and regional rest-CBF in healthy young subjects to be correlated with cognitive functions. The findings also suggest that, even in young cognitively intact subjects, resting brain activity (possibly underlain by default cognitive activity or metabolic demand from developed brain structures) is associated with cognitive functions. PMID:21980485

MRI of the lumbar spine: comparison of 3D isotropic turbo spin-echo SPACE sequence versus conventional 2D sequences at 3.0 T.

PubMed

Lee, Sungwon; Jee, Won-Hee; Jung, Joon-Yong; Lee, So-Yeon; Ryu, Kyeung-Sik; Ha, Kee-Yong

2015-02-01

Three-dimensional (3D) fast spin-echo sequence with variable flip-angle refocusing pulse allows retrospective alignments of magnetic resonance imaging (MRI) in any desired plane. To compare isotropic 3D T2-weighted (T2W) turbo spin-echo sequence (TSE-SPACE) with standard two-dimensional (2D) T2W TSE imaging for evaluating lumbar spine pathology at 3.0 T MRI. Forty-two patients who had spine surgery for disk herniation and had 3.0 T spine MRI were included in this study. In addition to standard 2D T2W TSE imaging, sagittal 3D T2W TSE-SPACE was obtained to produce multiplanar (MPR) images. Each set of MR images from 3D T2W TSE and 2D TSE-SPACE were independently scored for the degree of lumbar neural foraminal stenosis, central spinal stenosis, and nerve compression by two reviewers. These scores were compared with operative findings and the sensitivities were evaluated by McNemar test. Inter-observer agreements and the correlation with symptoms laterality were assessed with kappa statistics. The 3D T2W TSE and 2D TSE-SPACE had similar sensitivity in detecting foraminal stenosis (78.9% versus 78.9% in 32 foramen levels), spinal stenosis (100% versus 100% in 42 spinal levels), and nerve compression (92.9% versus 81.8% in 59 spinal nerves). The inter-observer agreements (κ = 0.849 vs. 0.451 for foraminal stenosis, κ = 0.809 vs. 0.503 for spinal stenosis, and κ = 0.681 vs. 0.429 for nerve compression) and symptoms correlation (κ = 0.449 vs. κ = 0.242) were better in 3D TSE-SPACE compared to 2D TSE. 3D TSE-SPACE with oblique coronal MPR images demonstrated better inter-observer agreements compared to 3D TSE-SPACE without oblique coronal MPR images (κ = 0.930 vs. κ = 0.681). Isotropic 3D T2W TSE-SPACE at 3.0 T was comparable to 2D T2W TSE for detecting foraminal stenosis, central spinal stenosis, and nerve compression with better inter-observer agreements and symptom correlation. © The Foundation Acta Radiologica 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

“Resting” CBF in the Epileptic Baboon: Correlation with Ketamine Dose and Interictal Epileptic Discharges

PubMed Central

Szabó, C. Ákos; Narayana, Shalini; Franklin, Crystal; Knape, Koyle D.; Davis, M. Duff; Fox, Peter T.; Leland, M. Michelle; Williams, Jeff T.

2011-01-01

Background Photosensitive epileptic (SZ) baboons demonstrate different cerebral blood flow (CBF) activation patterns from asymptomatic controls (CTL) during intermittent light stimulation (ILS). This study compares “resting” CBF between PS and CTL animals, and CBF correlations with ketamine dose and interictal epileptic discharges (IEDs) between PS and CTL animals. Methods Continuous intravenous ketamine was administered to eight PS and eight CTL baboons (matched for gender and weight), and maintained at subanesthetic doses (4.8–14.6 mg/kg/hr). Three resting H215O-PET studies were attempted in each animal (CTI/Siemens HR+ scanner). Images were acquired in 3D mode (63 contiguous slices, 2.4 mm thickness). PET images were co-registered with MRI images (3T Siemens Trio, T1-weighted 3D Turboflash sequence, TE/TR/TI = 3.04/2100/785 msec, flip angle=13 degrees). EEG was used to monitor depth of sedation and for quantification of IED rates. Regional CBF was compared between PS and CTL groups and correlations were analyzed for ketamine dose and IED rates. Results When subsets of animals of either group, receiving similar doses of ketamine were compared, PS animals demonstrated relative CBF increases in the occipital lobes and decreases in the frontal lobes. Correlation analyses with ketamine dose confirmed the frontal and occipital lobe changes in the PS animals. The negative correlations of CBF with ketamine dose and IED rate overlapped frontally. While frontal lobe CBF was also negatively correlated with IED rate, positive correlations were found in the parietal lobe. Conclusions “Resting” CBF differs between PS and CTL baboons. Correlation analyses of CBF and ketamine dose reveal that occipital lobe CBF increases and frontal lobe in PS animals are driven by ketamine. While frontal lobe CBF decreases may be related to ketamine’s propensity to activate IEDs, positive CBF correlations with IED rate suggest involvement of the parietal lobes in their generation. PMID:18801644

A 2D spiral turbo-spin-echo technique.

PubMed

Li, Zhiqiang; Karis, John P; Pipe, James G

2018-03-09

2D turbo-spin-echo (TSE) is widely used in the clinic for neuroimaging. However, the long refocusing radiofrequency pulse train leads to high specific absorption rate (SAR) and alters the contrast compared to conventional spin-echo. The purpose of this work is to develop a robust 2D spiral TSE technique for fast T 2 -weighted imaging with low SAR and improved contrast. A spiral-in/out readout is incorporated into 2D TSE to fully take advantage of the acquisition efficiency of spiral sampling while avoiding potential off-resonance-related artifacts compared to a typical spiral-out readout. A double encoding strategy and a signal demodulation method are proposed to mitigate the artifacts because of the T 2 -decay-induced signal variation. An adapted prescan phase correction as well as a concomitant phase compensation technique are implemented to minimize the phase errors. Phantom data demonstrate the efficacy of the proposed double encoding/signal demodulation, as well as the prescan phase correction and concomitant phase compensation. Volunteer data show that the proposed 2D spiral TSE achieves fast scan speed with high SNR, low SAR, and improved contrast compared to conventional Cartesian TSE. A robust 2D spiral TSE technique is feasible and provides a potential alternative to conventional 2D Cartesian TSE for T 2 -weighted neuroimaging. © 2018 International Society for Magnetic Resonance in Medicine.

Multimodal MRI-based imputation of the Aβ+ in early mild cognitive impairment

PubMed Central

Tosun, Duygu; Joshi, Sarang; Weiner, Michael W; for the Alzheimer's Disease Neuroimaging Initiative

2014-01-01

Objective The primary goal of this study was to identify brain atrophy from structural MRI (magnetic resonance imaging) and cerebral blood flow (CBF) patterns from arterial spin labeling perfusion MRI that are best predictors of the Aβ-burden, measured as composite 18F-AV45-PET (positron emission tomography) uptake, in individuals with early mild cognitive impairment (MCI). Furthermore, another objective was to assess the relative importance of imaging modalities in classification of Aβ+/Aβ− early MCI. Methods Sixty-seven Alzheimer's Disease Neuroimaging Initiative (ADNI)-GO/2 participants with early MCI were included. Voxel-wise anatomical shape variation measures were computed by estimating the initial diffeomorphic mapping momenta from an unbiased control template. CBF measures normalized to average motor cortex CBF were mapped onto the template space. Using partial least squares regression, we identified the structural and CBF signatures of Aβ after accounting for normal cofounding effects of age, gender, and education. Results 18F-AV45-positive early MCIs could be identified with 83% classification accuracy, 87% positive predictive value, and 84% negative predictive value by multidisciplinary classifiers combining demographics data, ApoE ε4-genotype, and a multimodal MRI-based Aβ score. Interpretation Multimodal MRI can be used to predict the amyloid status of early-MCI individuals. MRI is a very attractive candidate for the identification of inexpensive and noninvasive surrogate biomarkers of Aβ deposition. Our approach is expected to have value for the identification of individuals likely to be Aβ+ in circumstances where cost or logistical problems prevent Aβ detection using cerebrospinal fluid analysis or Aβ-PET. This can also be used in clinical settings and clinical trials, aiding subject recruitment and evaluation of treatment efficacy. Imputation of the Aβ-positivity status could also complement Aβ-PET by identifying individuals who would benefit the most from this assessment. PMID:24729983

Sudden transition and sudden change from open spin environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Zheng-Da; School of Science, Jiangnan University, Wuxi 214122; Xu, Jing-Bo, E-mail: xujb@zju.edu.cn

2014-11-15

We investigate the necessary conditions for the existence of sudden transition or sudden change phenomenon for appropriate initial states under dephasing. As illustrative examples, we study the behaviors of quantum correlation dynamics of two noninteracting qubits in independent and common open spin environments, respectively. For the independent environments case, we find that the quantum correlation dynamics is closely related to the Loschmidt echo and the dynamics exhibits a sudden transition from classical to quantum correlation decay. It is also shown that the sudden change phenomenon may occur for the common environment case and stationary quantum discord is found at themore » high temperature region of the environment. Finally, we investigate the quantum criticality of the open spin environment by exploring the probability distribution of the Loschmidt echo and the scaling transformation behavior of quantum discord, respectively. - Highlights: • Sudden transition or sudden change from open spin baths are studied. • Quantum discord is related to the Loschmidt echo in independent open spin baths. • Steady quantum discord is found in a common open spin bath. • The probability distribution of the Loschmidt echo is analyzed. • The scaling transformation behavior of quantum discord is displayed.« less

Improved Spin-Echo-Edited NMR Diffusion Measurements

NASA Astrophysics Data System (ADS)

Otto, William H.; Larive, Cynthia K.

2001-12-01

The need for simple and robust schemes for the analysis of ligand-protein binding has resulted in the development of diffusion-based NMR techniques that can be used to assay binding in protein solutions containing a mixture of several ligands. As a means of gaining spectral selectivity in NMR diffusion measurements, a simple experiment, the gradient modified spin-echo (GOSE), has been developed to reject the resonances of coupled spins and detect only the singlets in the 1H NMR spectrum. This is accomplished by first using a spin echo to null the resonances of the coupled spins. Following the spin echo, the singlet magnetization is flipped out of the transverse plane and a dephasing gradient is applied to reduce the spectral artifacts resulting from incomplete cancellation of the J-coupled resonances. The resulting modular sequence is combined here with the BPPSTE pulse sequence; however, it could be easily incorporated into any pulse sequence where additional spectral selectivity is desired. Results obtained with the GOSE-BPPSTE pulse sequence are compared with those obtained with the BPPSTE and CPMG-BPPSTE experiments for a mixture containing the ligands resorcinol and tryptophan in a solution of human serum albumin.

An approach to real-time magnetic resonance imaging for speech production

NASA Astrophysics Data System (ADS)

Narayanan, Shrikanth; Nayak, Krishna; Byrd, Dani; Lee, Sungbok

2003-04-01

Magnetic resonance imaging has served as a valuable tool for studying primarily static postures in speech production. Now, recent improvements in imaging techniques, particularly in temporal resolution, are making it possible to examine the dynamics of vocal tract shaping during speech. Examples include Mady et al. (2001, 2002) (8 images/second, T1 fast gradient echo) and Demolin et al. (2000) (4-5 images/second, ultra fast turbo spin echo sequence). The present study uses a non 2D-FFT acquisition strategy (spiral k-space trajectory) on a GE Signa 1.5T CV/i scanner with a low-flip angle spiral gradient echo originally developed for cardiac imaging [Kerr et al. (1997), Nayak et al. (2001)] with reconstruction rates of 8-10 images/second. The experimental stimuli included English sentences varying the syllable position of /n, r, l/ (spoken by 2 subjects) and Tamil sentences varying among five liquids (spoken by one subject). The imaging parameters were the following: 15 deg flip angle, 20-interleaves, 6.7 ms TR, 1.88 mm resolution over a 20 cm FOV, 5 mm slice thickness, and 2.4 ms spiral readouts. Data show clear real-time movements of the lips, tongue and velum. Sample movies and data analysis strategies will be presented. Segmental durations, positions, and inter-articulator timing can all be quantitatively evaluated. [Work supported by NIH.

Relationships between Cerebral Blood Flow and IQ in Typically Developing Children and Adolescents.

PubMed

Kilroy, Emily; Liu, Collin Y; Yan, Lirong; Kim, Yoon Chun; Dapretto, Mirella; Mendez, Mario F; Wang, Danny J J

2011-01-01

The objective of this study was to explore the relationships between IQ and cerebral blood flow (CBF) measured by arterial spin labeling (ASL) in children and adolescents. ASL was used to collect perfusion MRI data on 39 healthy participants aged 7 to 17. The Wechsler Abbreviated Intelligence Scale was administered to determine IQ scores. Multivariate regression was applied to reveal correlations between CBF and IQ scores, accounting for age, sex and global mean CBF. Voxel Based Morphometry (VBM) analysis, which measures regional cortical volume, was performed as a control. Regression analyses were further performed on CBF data with adjustment of regional gray matter density (GMD). A positive correlation between CBF and IQ scores was primarily seen in the subgenual/anterior cingulate, right orbitofrontal, superior temporal and right inferior parietal regions. An inverse relationship between CBF and IQ was mainly observed in bilateral posterior temporal regions. After adjusting for regional GMD, the correlations between CBF and IQ in the subgenual/anterior cingulate cortex, right orbitofrontal, superior temporal regions and left insula remained significant. These findings support the Parieto-Frontal Integration Theory of intelligence, especially the role of the subgenual/anterior cingulate cortex in the neural networks associated with intelligence. The present study also demonstrates the unique value of CBF in assessing brain-behavior relationships, in addition to structural morphometric measures.

Vessel-wall imaging and quantification of flow-mediated dilation using water-selective 3D SSFP-echo.

PubMed

Langham, Michael C; Li, Cheng; Englund, Erin K; Chirico, Erica N; Mohler, Emile R; Floyd, Thomas F; Wehrli, Felix W

2013-10-30

To introduce a new, efficient method for vessel-wall imaging of carotid and peripheral arteries by means of a flow-sensitive 3D water-selective SSFP-echo pulse sequence. Periodic applications of RF pulses will generate two transverse steady states, immediately after and before an RF pulse; the latter being referred to as the SSFP-echo. The SSFP-echo signal for water protons in blood is spoiled as a result of moving spins losing phase coherence in the presence of a gradient pulse along the flow direction. Bloch equation simulations were performed over a wide range of velocities to evaluate the flow sensitivity of the SSFP-echo signal. Vessel walls of carotid and femoral and popliteal arteries were imaged at 3 T. In two patients with peripheral artery disease the femoral arteries were imaged bilaterally to demonstrate method's potential to visualize atherosclerotic plaques. The method was also evaluated as a means to measure femoral artery flow-mediated dilation (FMD) in response to cuff-induced ischemia in four subjects. The SSFP-echo pulse sequence, which does not have a dedicated blood signal suppression preparation, achieved low blood signal permitting discrimination of the carotid and peripheral arterial walls with in-plane spatial resolution ranging from 0.5 to 0.69 mm and slice thickness of 2 to 3 mm, i.e. comparable to conventional 2D vessel-wall imaging techniques. The results of the simulations were in good agreement with analytical solution and observations for both vascular territories examined. Scan time ranged from 2.5 to 5 s per slice yielding a contrast-to-noise ratio between the vessel wall and lumen from 3.5 to 17. Mean femoral FMD in the four subjects was 9%, in good qualitative agreement with literature values. Water-selective 3D SSFP-echo pulse sequence is a potential alternative to 2D vessel-wall imaging. The proposed method is fast, robust, applicable to a wide range of flow velocities, and straightforward to implement.

Validation of a T1 and T2* leakage correction method based on multi-echo DSC-MRI using MION as a reference standard

PubMed Central

Stokes, Ashley M.; Semmineh, Natenael; Quarles, C. Chad

2015-01-01

Purpose A combined biophysical- and pharmacokinetic-based method is proposed to separate, quantify, and correct for both T1 and T2* leakage effects using dual-echo DSC acquisitions to provide more accurate hemodynamic measures, as validated by a reference intravascular contrast agent (CA). Methods Dual-echo DSC-MRI data were acquired in two rodent glioma models. The T1 leakage effects were removed and also quantified in order to subsequently correct for the remaining T2* leakage effects. Pharmacokinetic, biophysical, and combined biophysical and pharmacokinetic models were used to obtain corrected cerebral blood volume (CBV) and cerebral blood flow (CBF), and these were compared with CBV and CBF from an intravascular CA. Results T1-corrected CBV was significantly overestimated compared to MION CBV, while T1+T2*-correction yielded CBV values closer to the reference values. The pharmacokinetic and simplified biophysical methods showed similar results and underestimated CBV in tumors exhibiting strong T2* leakage effects. The combined method was effective for correcting T1 and T2* leakage effects across tumor types. Conclusions Correcting for both T1 and T2* leakage effects yielded more accurate measures of CBV. The combined correction method yields more reliable CBV measures than either correction method alone, but for certain brain tumor types (e.g., gliomas) the simplified biophysical method may provide a robust and computationally efficient alternative. PMID:26362714

The aluminum ordering in aluminosilicates: a dipolar 27Al NMR spectroscopy study.

PubMed

Gee, Becky A

2004-01-01

The spatial ordering of aluminum atoms in CsAl(SiO3)2 and 3Al2O3.2SiO2 was probed by 27Al dipolar solid-state NMR spectroscopy. The 27Al response to a Hahn spin-echo pulse sequence in a series of aluminum-containing model crystalline compounds demonstrates that quantitative 27Al homonuclear dipolar second moments can be obtained to within +/-20% of the theoretical values, if evaluation of the spin-echo response curve is limited to short evolution periods (2t1 < or = 0.10 ms). Additionally, selective excitation of the central transition m = 1/2 --> -1/2 is necessary in order to ensure quantitative results. Restriction of spin exchange affecting the dephasing of the magnetization may decelerate the spin-echo decay at longer evolution periods. Considering these restraints, the method was used to probe the spatial distribution of aluminum atoms among the tetrahedral sites in two aluminosilicate materials. Experimental 27Al spin-echo response data for the aluminosilicates CsAl(SiO3)2 (synthetic pollucite) and 3Al2O3.2SiO2 (mullite) are compared with theoretical data based on (I) various degrees of aluminum-oxygen-aluminum bond formation among tetrahedrally coordinated aluminum atoms (Al(T(d) )-O-Al(T(d) )) and (II) the maximum avoidance of Al(T(d) )-O-Al(T(d) ) bonding. Analysis of the second moment values and resulting echo decay responses suggests that partial suppression of spin exchange among aluminum atoms in crystallographically distinct sites may contribute to the 27Al spin echo decay in 3Al2O3.2SiO2, thus complicating quantitative analysis of the data. Silicon-29 and aluminum-27 magic angle spinning (MAS) NMR spectra of 3Al2O3.2SiO2 are consistent with those previously reported. The experimental 27Al spin-echo response behavior of CsAl(SiO3)2 differs from the theoretical response behavior based on the maximum avoidance of Al-O-Al bonding between tetrahedral aluminum sites in CsAl(SiO3)2. A single unresolved resonance is observed in both the silicon-29 and aluminum-27 MAS spectra of CsAl(SiO3)2. Copyright 2003 John Wiley & Sons, Ltd.

Externally calibrated parallel imaging for 3D multispectral imaging near metallic implants using broadband ultrashort echo time imaging.

PubMed

Wiens, Curtis N; Artz, Nathan S; Jang, Hyungseok; McMillan, Alan B; Reeder, Scott B

2017-06-01

To develop an externally calibrated parallel imaging technique for three-dimensional multispectral imaging (3D-MSI) in the presence of metallic implants. A fast, ultrashort echo time (UTE) calibration acquisition is proposed to enable externally calibrated parallel imaging techniques near metallic implants. The proposed calibration acquisition uses a broadband radiofrequency (RF) pulse to excite the off-resonance induced by the metallic implant, fully phase-encoded imaging to prevent in-plane distortions, and UTE to capture rapidly decaying signal. The performance of the externally calibrated parallel imaging reconstructions was assessed using phantoms and in vivo examples. Phantom and in vivo comparisons to self-calibrated parallel imaging acquisitions show that significant reductions in acquisition times can be achieved using externally calibrated parallel imaging with comparable image quality. Acquisition time reductions are particularly large for fully phase-encoded methods such as spectrally resolved fully phase-encoded three-dimensional (3D) fast spin-echo (SR-FPE), in which scan time reductions of up to 8 min were obtained. A fully phase-encoded acquisition with broadband excitation and UTE enabled externally calibrated parallel imaging for 3D-MSI, eliminating the need for repeated calibration regions at each frequency offset. Significant reductions in acquisition time can be achieved, particularly for fully phase-encoded methods like SR-FPE. Magn Reson Med 77:2303-2309, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Imaging Human Brain Perfusion with Inhaled Hyperpolarized 129Xe MR Imaging.

PubMed

Rao, Madhwesha R; Stewart, Neil J; Griffiths, Paul D; Norquay, Graham; Wild, Jim M

2018-02-01

Purpose To evaluate the feasibility of directly imaging perfusion of human brain tissue by using magnetic resonance (MR) imaging with inhaled hyperpolarized xenon 129 ( 129 Xe). Materials and Methods In vivo imaging with 129 Xe was performed in three healthy participants. The combination of a high-yield spin-exchange optical pumping 129 Xe polarizer, custom-built radiofrequency coils, and an optimized gradient-echo MR imaging protocol was used to achieve signal sensitivity sufficient to directly image hyperpolarized 129 Xe dissolved in the human brain. Conventional T1-weighted proton (hydrogen 1 [ 1 H]) images and perfusion images by using arterial spin labeling were obtained for comparison. Results Images of 129 Xe uptake were obtained with a signal-to-noise ratio of 31 ± 9 and demonstrated structural similarities to the gray matter distribution on conventional T1-weighted 1 H images and to perfusion images from arterial spin labeling. Conclusion Hyperpolarized 129 Xe MR imaging is an injection-free means of imaging the perfusion of cerebral tissue. The proposed method images the uptake of inhaled xenon gas to the extravascular brain tissue compartment across the intact blood-brain barrier. This level of sensitivity is not readily available with contemporary MR imaging methods. © RSNA, 2017.

Instant images of the human heart using a new, whole-body MR imaging system.

PubMed

Rzedzian, R R; Pykett, I L

1987-08-01

An extremely rapid MR imaging technique is described, and its use on a new 2.0-T high-speed MR system is demonstrated. This implementation permits complete filling of the two-dimensional spatial-frequency domain (k-space) within an acquisition window of 26 msec. With this acquisition window placed under the spin-echo signal envelope generated by a 90-180 degree pulse pair, the image contrast is the same as that of a conventional spin-echo pulse sequence. Resultant proton images have a motion-independent voxel resolution of 0.08 cm3 and a signal-to-noise ratio for cardiac muscle of approximately 30:1 (for TE = 30 msec) with no signal averaging. The pulse sequence yields images that are chemical shift-resolved. The total proton density distribution is optionally presented with lipid and water signals displayed in two different colors. Cardiac function is observed by displaying multiple images, acquired at different times in successive cardiac periods, in a cyclic movie format. Such motion pictures are obtained within a single period of suspended respiration, thereby assuring freedom from respiratory related motion artifacts. As preliminary examples, we present MR images of the normal adult human heart that have total acquisition times of only 40 msec/image and that show the major cardiac anatomy. Frames from movie loops show contraction of cardiac chambers and left ventricular wall thickening. The extremely rapid acquisition time of this technique suggests that it may hold promise for the routine and cost-effective evaluation of cardiac anatomy and function.

Water-fat separation with parallel imaging based on BLADE.

PubMed

Weng, Dehe; Pan, Yanli; Zhong, Xiaodong; Zhuo, Yan

2013-06-01

Uniform suppression of fat signal is desired in clinical applications. Based on phase differences introduced by different chemical shift frequencies, Dixon method and its variations are used as alternatives of fat saturation methods, which are sensitive to B0 inhomogeneities. Iterative Decomposition of water and fat with Echo Asymmetry and Least squares estimation (IDEAL) separates water and fat images with flexible echo shifting. Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction (PROPELLER, alternatively termed as BLADE), in conjunction with IDEAL, yields Turboprop IDEAL (TP-IDEAL) and allows for decomposition of water and fat signal with motion correction. However, the flexibility of its parameter setting is limited, and the related phase correction is complicated. To address these problems, a novel method, BLADE-Dixon, is proposed in this study. This method used the same polarity readout gradients (fly-back gradients) to acquire in-phase and opposed-phases images, which led to less complicated phase correction and more flexible parameter setting compared to TP-IDEAL. Parallel imaging and undersampling were integrated to reduce scan time. Phantom, orbit, neck and knee images were acquired with BLADE-Dixon. Water-fat separation results were compared to those measured with conventional turbo spin echo (TSE) Dixon and TSE with fat saturation, respectively, to demonstrate the performance of BLADE-Dixon. Copyright © 2013 Elsevier Inc. All rights reserved.

Rapid acquisition of magnetic resonance imaging of the shoulder using three-dimensional fast spin echo sequence with compressed sensing.

PubMed

Lee, Seung Hyun; Lee, Young Han; Song, Ho-Taek; Suh, Jin-Suck

2017-10-01

To evaluate the feasibility of 3D fast spin-echo (FSE) imaging with compressed sensing (CS) for the assessment of shoulder. Twenty-nine patients who underwent shoulder MRI including image sets of axial 3D-FSE sequence without CS and with CS, using an acceleration factor of 1.5, were included. Quantitative assessment was performed by calculating the root mean square error (RMSE) and structural similarity index (SSIM). Two musculoskeletal radiologists compared image quality of 3D-FSE sequences without CS and with CS, and scored the qualitative agreement between sequences, using a five-point scale. Diagnostic agreement for pathologic shoulder lesions between the two sequences was evaluated. The acquisition time of 3D-FSE MRI was reduced using CS (3min 23s vs. 2min 22s). Quantitative evaluations showed a significant correlation between the two sequences (r=0.872-0.993, p<0.05) and SSIM was in an acceptable range (0.940-0.993; mean±standard deviation, 0.968±0.018). Qualitative image quality showed good to excellent agreement between 3D-FSE images without CS and with CS. Diagnostic agreement for pathologic shoulder lesions between the two sequences was very good (κ=0.915-1). The 3D-FSE sequence with CS is feasible in evaluating the shoulder joint with reduced scan time compared to 3D-FSE without CS. Copyright © 2017 Elsevier Inc. All rights reserved.

MRI of the knees in asymptomatic adolescent soccer players: A case-control study.

PubMed

Matiotti, Simone B; Soder, Ricardo B; Becker, Rafaela G; Santos, Francisco S; Baldisserotto, Matteo

2017-01-01

To determine the range of asymptomatic abnormal findings in adolescent soccer players at 3.0T MRI of the knee. In all, 87 knees of asymptomatic 14-17-year-old male adolescents were evaluated at 3T, using a standardized examination protocol comprising four sequences: two fat-suppressed T 2 -weighted fast spin-echo sequences (T 2 FSE), in the sagittal (repetition time / echo time [TR/TE], 5.300/71, echo train length [ETL] 17) and coronal planes (TR/TE, 4234/70, ETL 17), one fat-suppressed proton density (PD) sequence in the axial plane (TR/TE, 2.467/40, ETL 9), and one T 1 -weighted spin-echo (T 1 SE) sequence in the sagittal plane (TR/TE, 684/12.5). Soccer players (46 knees) were paired with controls (41 knees) by age and weight. Bone marrow, articular cartilage, meniscus, tendons, ligaments, fat pad abnormalities, and joint fluid were assessed. One or more abnormalities were detected in 31 knees (67.4%) in the soccer player group, compared to 20 knees (48.8%) in the control group. The prevalence of bone marrow edema was higher in the soccer group (19 knees, 41.3%) than in the control group (3 knees, 7.3%), P = 0.001. Other abnormalities found in this sample (joint effusion, cartilage lesions, tendinopathy, ganglion cysts, and infrapatellar fat pat edema) were not significantly different between the two study groups. Asymptomatic adolescents had a high prevalence of abnormal findings on knee imaging, especially bone marrow edema. This prevalence was higher among soccer players. 4 J. Magn. Reson. Imaging 2017;45:59-65. © 2016 International Society for Magnetic Resonance in Medicine.

SU-F-I-16: Short Breast MRI with High-Resolution T2-Weighted and Dynamic Contrast Enhanced T1-Weighted Images

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, J; Son, J; Arun, B

Purpose: To develop and demonstrate a short breast (sb) MRI protocol that acquires both T2-weighted and dynamic contrast-enhanced T1-weighted images in approximately ten minutes. Methods: The sb-MRI protocol consists of two novel pulse sequences. The first is a flexible fast spin-echo triple-echo Dixon (FTED) sequence for high-resolution fat-suppressed T2-weighted imaging, and the second is a 3D fast dual-echo spoiled gradient sequence (FLEX) for volumetric fat-suppressed T1-weighted imaging before and post contrast agent injection. The flexible FTED sequence replaces each single readout during every echo-spacing period of FSE with three fast-switching bipolar readouts to produce three raw images in a singlemore » acquisition. These three raw images are then post-processed using a Dixon algorithm to generate separate water-only and fat-only images. The FLEX sequence acquires two echoes using dual-echo readout after each RF excitation and the corresponding images are post-processed using a similar Dixon algorithm to yield water-only and fat-only images. The sb-MRI protocol was implemented on a 3T MRI scanner and used for patients who had undergone concurrent clinical MRI for breast cancer screening. Results: With the same scan parameters (eg, spatial coverage, field of view, spatial and temporal resolution) as the clinical protocol, the total scan-time of the sb-MRI protocol (including the localizer, bilateral T2-weighted, and dynamic contrast-enhanced T1-weighted images) was 11 minutes. In comparison, the clinical breast MRI protocol took 43 minutes. Uniform fat suppression and high image quality were consistently achieved by sb-MRI. Conclusion: We demonstrated a sb-MRI protocol comprising both T2-weighted and dynamic contrast-enhanced T1-weighted images can be performed in approximately ten minutes. The spatial and temporal resolution of the images easily satisfies the current breast MRI accreditation guidelines by the American College of Radiology. The protocol has the potential of making breast MRI more widely accessible to and more tolerable by the patients. JMA is the inventor of United States patents that are owned by the University of Texas Board of Regents and currently licensed to GE Healthcare and Siemens Gmbh.« less

Application of Modified Spin-Echo–based Sequences for Hepatic MR Elastography: Evaluation, Comparison with the Conventional Gradient-Echo Sequence, and Preliminary Clinical Experience

PubMed Central

Mariappan, Yogesh K.; Dzyubak, Bogdan; Glaser, Kevin J.; Venkatesh, Sudhakar K.; Sirlin, Claude B.; Hooker, Jonathan; McGee, Kiaran P.

2017-01-01

Purpose To (a) evaluate modified spin-echo (SE) magnetic resonance (MR) elastographic sequences for acquiring MR images with improved signal-to-noise ratio (SNR) in patients in whom the standard gradient-echo (GRE) MR elastographic sequence yields low hepatic signal intensity and (b) compare the stiffness values obtained with these sequences with those obtained with the conventional GRE sequence. Materials and Methods This HIPAA-compliant retrospective study was approved by the institutional review board; the requirement to obtain informed consent was waived. Data obtained with modified SE and SE echo-planar imaging (EPI) MR elastographic pulse sequences with short echo times were compared with those obtained with the conventional GRE MR elastographic sequence in two patient cohorts, one that exhibited adequate liver signal intensity and one that exhibited low liver signal intensity. Shear stiffness values obtained with the three sequences in 130 patients with successful GRE-based examinations were retrospectively tested for statistical equivalence by using a 5% margin. In 47 patients in whom GRE examinations were considered to have failed because of low SNR, the SNR and confidence level with the SE-based sequences were compared with those with the GRE sequence. Results The results of this study helped confirm the equivalence of SE MR elastography and SE-EPI MR elastography to GRE MR elastography (P = .0212 and P = .0001, respectively). The SE and SE-EPI MR elastographic sequences provided substantially improved SNR and stiffness inversion confidence level in 47 patients in whom GRE MR elastography had failed. Conclusion Modified SE-based MR elastographic sequences provide higher SNR MR elastographic data and reliable stiffness measurements; thus, they enable quantification of stiffness in patients in whom the conventional GRE MR elastographic sequence failed owing to low signal intensity. The equivalence of the three sequences indicates that the current diagnostic thresholds are applicable to SE MR elastographic sequences for assessing liver fibrosis. © RSNA, 2016 PMID:27509543

MR Fingerprinting Using The Quick Echo Splitting NMR Imaging Technique

PubMed Central

Jiang, Yun; Ma, Dan; Jerecic, Renate; Duerk, Jeffrey; Seiberlich, Nicole; Gulani, Vikas; Griswold, Mark A.

2016-01-01

Purpose The purpose of the study is to develop a quantitative method for the relaxation properties with a reduced radio frequency (RF) power deposition by combining Magnetic Resonance Fingerprinting (MRF) technique with Quick Echo Splitting NMR Imaging Technique (QUEST). Methods A QUEST-based MRF sequence was implemented to acquire high order echoes by increasing the gaps between RF pulses. Bloch simulations were used to calculate a dictionary containing the range of physically plausible signal evolutions using a range of T1 and T2 values based on the pulse sequence. MRF-QUEST was evaluated by comparing to the results of spin-echo methods. The SAR of QUEST-MRF was compared to the clinically available methods. Results MRF-QUEST quantifies the relaxation properties with good accuracy at the estimated head Specific Absorption Rate (SAR) of 0.03 W/kg. T1 and T2 values estimated by MRF-QUEST are in good agreement with the traditional methods. Conclusion The combination of the MRF and the QUEST provides an accurate quantification of T1 and T2 simultaneously with reduced RF power deposition. The resulting lower SAR may provide a new acquisition strategy for MRF when RF energy deposition is problematic. PMID:26924639

Understanding Magnetic Resonance Imaging of Knee Cartilage Repair: A Focus on Clinical Relevance.

PubMed

Hayashi, Daichi; Li, Xinning; Murakami, Akira M; Roemer, Frank W; Trattnig, Siegfried; Guermazi, Ali

2017-06-01

The aims of this review article are (a) to describe the principles of morphologic and compositional magnetic resonance imaging (MRI) techniques relevant for the imaging of knee cartilage repair surgery and their application to longitudinal studies and (b) to illustrate the clinical relevance of pre- and postsurgical MRI with correlation to intraoperative images. First, MRI sequences that can be applied for imaging of cartilage repair tissue in the knee are described, focusing on comparison of 2D and 3D fast spin echo and gradient recalled echo sequences. Imaging features of cartilage repair tissue are then discussed, including conventional (morphologic) MRI and compositional MRI techniques. More specifically, imaging techniques for specific cartilage repair surgery techniques as described above, as well as MRI-based semiquantitative scoring systems for the knee cartilage repair tissue-MR Observation of Cartilage Repair Tissue and Cartilage Repair OA Knee Score-are explained. Then, currently available surgical techniques are reviewed, including marrow stimulation, osteochondral autograft, osteochondral allograft, particulate cartilage allograft, autologous chondrocyte implantation, and others. Finally, ongoing research efforts and future direction of cartilage repair tissue imaging are discussed.

Magnetic resonance imaging protocols for examination of the neurocranium at 3 T.

PubMed

Schwindt, W; Kugel, H; Bachmann, R; Kloska, S; Allkemper, T; Maintz, D; Pfleiderer, B; Tombach, B; Heindel, W

2003-09-01

The increasing availability of high-field (3 T) MR scanners requires adapting and optimizing clinical imaging protocols to exploit the theoretically higher signal-to-noise ratio (SNR) of the higher field strength. Our aim was to establish reliable and stable protocols meeting the clinical demands for imaging the neurocranium at 3 T. Two hundred patients with a broad range of indications received an examination of the neurocranium with an appropriate assortment of imaging techniques at 3 T. Several imaging parameters were optimized. Keeping scan times comparable to those at 1.5 T we increased spatial resolution. Contrast-enhanced and non-enhanced T1-weighted imaging was best applying gradient-echo and inversion recovery (rather than spin-echo) techniques, respectively. For fluid-attenuated inversion recovery (FLAIR) imaging a TE of 120 ms yielded optimum contrast-to-noise ratio (CNR). High-resolution isotropic 3D data sets were acquired within reasonable scan times. Some artifacts were pronounced, but generally imaging profited from the higher SNR. We present a set of optimized examination protocols for neuroimaging at 3 T, which proved to be reliable in a clinical routine setting.

A compact 3 T all HTS cryogen-free MRI system

NASA Astrophysics Data System (ADS)

Parkinson, B. J.; Bouloukakis, K.; Slade, R. A.

2017-12-01

We have designed and built a passively shielded, cryogen-free 3 T 160 mm bore bismuth strontium calcium copper oxide HTS magnet with shielded gradient coils suitable for use in small animal imaging applications. The magnet is cooled to approximately 16 K using a two-stage cryocooler and is operated at 200 A. The magnet has been passively shimmed so as to achieve ±10 parts per million (ppm) homogeneity over a 60 mm diameter imaging volume. We have demonstrated that B 0 temporal stability is fit-for-purpose despite the magnet operating in the driven mode. The system has produced good quality spin-echo and gradient echo images. This compact HTS-MRI system is emerging as a true alternative to conventional low temperature superconductor based cryogen-free MRI systems, with much more efficient cryogenics since it operates entirely from a single phase alternating current electrical supply.

Free-breathing black-blood CINE fast-spin echo imaging for measuring abdominal aortic wall distensibility: a feasibility study

NASA Astrophysics Data System (ADS)

Lin, Jyh-Miin; Patterson, Andrew J.; Chao, Tzu-Cheng; Zhu, Chengcheng; Chang, Hing-Chiu; Mendes, Jason; Chung, Hsiao-Wen; Gillard, Jonathan H.; Graves, Martin J.

2017-05-01

The paper reports a free-breathing black-blood CINE fast-spin echo (FSE) technique for measuring abdominal aortic wall motion. The free-breathing CINE FSE includes the following MR techniques: (1) variable-density sampling with fast iterative reconstruction; (2) inner-volume imaging; and (3) a blood-suppression preparation pulse. The proposed technique was evaluated in eight healthy subjects. The inner-volume imaging significantly reduced the intraluminal artifacts of respiratory motion (p  =  0.015). The quantitative measurements were a diameter of 16.3  ±  2.8 mm and wall distensibility of 2.0  ±  0.4 mm (12.5  ±  3.4%) and 0.7  ±  0.3 mm (4.1  ±  1.0%) for the anterior and posterior walls, respectively. The cyclic cross-sectional distensibility was 35  ±  15% greater in the systolic phase than in the diastolic phase. In conclusion, we developed a feasible CINE FSE method to measure the motion of the abdominal aortic wall, which will enable clinical scientists to study the elasticity of the abdominal aorta.

Spoiled gradient recalled acquisition in the steady state technique is superior to conventional postcontrast spin echo technique for magnetic resonance imaging detection of adrenocorticotropin-secreting pituitary tumors.

PubMed

Patronas, Nicholas; Bulakbasi, Nail; Stratakis, Constantine A; Lafferty, Antony; Oldfield, Edward H; Doppman, John; Nieman, Lynnette K

2003-04-01

Recent studies show that the standard T1-weighted spin echo (SE) technique for magnetic resonance imaging (MRI) fails to identify 40% of corticotrope adenomas. We hypothesized that the superior soft tissue contrast and thinner sections obtained with spoiled gradient recalled acquisition in the steady state (SPGR) would improve tumor detection. We compared the performance of SE and SPGR MRI in 50 patients (age, 7-67 yr) with surgically confirmed corticotrope adenoma. Coronal SE and SPGR MR images were obtained before and after administration of gadolinium contrast, using a 1.5 T scanner. SE scans were obtained over 5.1 min (12-cm field of view; interleaved sections, 3 mm). SPGR scans were obtained over 3.45 min (12- or 18-cm field of view, contiguous 1- or 2-mm slices). The MRI interpretations of two radiologists were compared with findings at surgical resection. Compared with SE for detection of tumor, SPGR had superior sensitivity (80%; confidence interval, 68-91; vs. 49%; confidence interval, 34-63%), but a higher false positive rate (2% vs. 4%). We recommend the addition of SPGR to SE sequences using pituitary-specific technical parameters to improve the MRI detection of ACTH-secreting pituitary tumors.

Simulation of High-Resolution Magnetic Resonance Images on the IBM Blue Gene/L Supercomputer Using SIMRI

DOE PAGES

Baum, K. G.; Menezes, G.; Helguera, M.

2011-01-01

Medical imaging system simulators are tools that provide a means to evaluate system architecture and create artificial image sets that are appropriate for specific applications. We have modified SIMRI, a Bloch equation-based magnetic resonance image simulator, in order to successfully generate high-resolution 3D MR images of the Montreal brain phantom using Blue Gene/L systems. Results show that redistribution of the workload allows an anatomically accurate 256 3 voxel spin-echo simulation in less than 5 hours when executed on an 8192-node partition of a Blue Gene/L system.

Simulation of High-Resolution Magnetic Resonance Images on the IBM Blue Gene/L Supercomputer Using SIMRI.

PubMed

Baum, K G; Menezes, G; Helguera, M

2011-01-01

Medical imaging system simulators are tools that provide a means to evaluate system architecture and create artificial image sets that are appropriate for specific applications. We have modified SIMRI, a Bloch equation-based magnetic resonance image simulator, in order to successfully generate high-resolution 3D MR images of the Montreal brain phantom using Blue Gene/L systems. Results show that redistribution of the workload allows an anatomically accurate 256(3) voxel spin-echo simulation in less than 5 hours when executed on an 8192-node partition of a Blue Gene/L system.

The Alzheimer's Disease Neuroimaging Initiative (ADNI): MRI Methods

PubMed Central

Jack, Clifford R.; Bernstein, Matt A.; Fox, Nick C.; Thompson, Paul; Alexander, Gene; Harvey, Danielle; Borowski, Bret; Britson, Paula J.; Whitwell, Jennifer L.; Ward, Chadwick; Dale, Anders M.; Felmlee, Joel P.; Gunter, Jeffrey L.; Hill, Derek L.G.; Killiany, Ron; Schuff, Norbert; Fox-Bosetti, Sabrina; Lin, Chen; Studholme, Colin; DeCarli, Charles S.; Krueger, Gunnar; Ward, Heidi A.; Metzger, Gregory J.; Scott, Katherine T.; Mallozzi, Richard; Blezek, Daniel; Levy, Joshua; Debbins, Josef P.; Fleisher, Adam S.; Albert, Marilyn; Green, Robert; Bartzokis, George; Glover, Gary; Mugler, John; Weiner, Michael W.

2008-01-01

The Alzheimer's Disease Neuroimaging Initiative (ADNI) is a longitudinal multisite observational study of healthy elders, mild cognitive impairment (MCI), and Alzheimer's disease. Magnetic resonance imaging (MRI), (18F)-fluorode-oxyglucose positron emission tomography (FDG PET), urine serum, and cerebrospinal fluid (CSF) biomarkers, as well as clinical/psychometric assessments are acquiredat multiple time points. All data will be cross-linked and made available to the general scientific community. The purpose of this report is to describe the MRI methods employed in ADNI. The ADNI MRI core established specifications thatguided protocol development. A major effort was devoted toevaluating 3D T1-weighted sequences for morphometric analyses. Several options for this sequence were optimized for the relevant manufacturer platforms and then compared in a reduced-scale clinical trial. The protocol selected for the ADNI study includes: back-to-back 3D magnetization prepared rapid gradient echo (MP-RAGE) scans; B1-calibration scans when applicable; and an axial proton density-T2 dual contrast (i.e., echo) fast spin echo/turbo spin echo (FSE/TSE) for pathology detection. ADNI MRI methods seek to maximize scientific utility while minimizing the burden placed on participants. The approach taken in ADNI to standardization across sites and platforms of the MRI protocol, postacquisition corrections, and phantom-based monitoring of all scanners could be used as a model for other multisite trials. PMID:18302232

In Vivo Visualization of Alzheimer’s Amyloid Plaques by MRI in Transgenic Mice Without a Contrast Agent

PubMed Central

Jack, Clifford R.; Garwood, Michael; Wengenack, Thomas M.; Borowski, Bret; Curran, Geoffrey L.; Lin, Joseph; Adriany, Gregor; Grohn, Olli H.J.; Grimm, Roger; Poduslo, Joseph F.

2009-01-01

One of the cardinal pathologic features of Alzheimer’s disease (AD) is formation of senile, or amyloid, plaques. Transgenic mice have been developed that express one or more of the genes responsible for familial AD in humans. Doubly transgenic mice develop “human-like” plaques, providing a mechanism to study amyloid plaque biology in a controlled manner. Imaging of labeled plaques has been accomplished with other modalities, but only MRI has sufficient spatial and contrast resolution to visualize individual plaques non-invasively. Methods to optimize visualization of plaques in vivo in transgenic mice at 9.4 T using a spin echo sequence based on adiabatic pulses are described. Preliminary results indicate that a spin echo acquisition more accurately reflects plaque size, while a T2* weighted gradient echo sequence reflects plaque iron content not plaque size. In vivo MRI – ex vivo MRI – in vitro histological correlations are provided. Histologically verified plaques as small as 50 μm in diameter were visualized in the living animal. To our knowledge this work represents the first demonstration of non-invasive in vivo visualization of individual AD plaques without the use of a contrast agent. PMID:15562496

Optimized, unequal pulse spacing in multiple echo sequences improves refocusing in magnetic resonance.

PubMed

Jenista, Elizabeth R; Stokes, Ashley M; Branca, Rosa Tamara; Warren, Warren S

2009-11-28

A recent quantum computing paper (G. S. Uhrig, Phys. Rev. Lett. 98, 100504 (2007)) analytically derived optimal pulse spacings for a multiple spin echo sequence designed to remove decoherence in a two-level system coupled to a bath. The spacings in what has been called a "Uhrig dynamic decoupling (UDD) sequence" differ dramatically from the conventional, equal pulse spacing of a Carr-Purcell-Meiboom-Gill (CPMG) multiple spin echo sequence. The UDD sequence was derived for a model that is unrelated to magnetic resonance, but was recently shown theoretically to be more general. Here we show that the UDD sequence has theoretical advantages for magnetic resonance imaging of structured materials such as tissue, where diffusion in compartmentalized and microstructured environments leads to fluctuating fields on a range of different time scales. We also show experimentally, both in excised tissue and in a live mouse tumor model, that optimal UDD sequences produce different T(2)-weighted contrast than do CPMG sequences with the same number of pulses and total delay, with substantial enhancements in most regions. This permits improved characterization of low-frequency spectral density functions in a wide range of applications.

Linearization correction of /sup 99m/Tc-labeled hexamethyl-propylene amine oxime (HM-PAO) image in terms of regional CBF distribution: comparison to C VO2 inhalation steady-state method measured by positron emission tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Inugami, A.; Kanno, I.; Uemura, K.

1988-12-01

The radioisotope distribution following intravenous injection of 99mTc-labeled hexamethylpropyleneamine oxime (HM-PAO) in the brain was measured by single photon emission computed tomography (SPECT) and corrected for the nonlinearity caused by differences in net extraction. The linearization correction was based on a three compartment model, and it required a region of reference to normalize the SPECT image in terms of regional cerebral blood flow distribution. Two different regions of reference, the cerebellum and the whole brain, were tested. The uncorrected and corrected HM-PAO images were compared with cerebral blood flow (CBF) image measured by the C VO2 inhalation steady state methodmore » and positron emission tomography (PET). The relationship between uncorrected HM-PAO and PET-CBF showed a correlation coefficient of 0.85 but tended to saturate at high CBF values, whereas it was improved to 0.93 after the linearization correction. The whole-brain normalization worked just as well as normalization using the cerebellum. This study constitutes a validation of the linearization correction and it suggests that after linearization the HM-PAO image may be scaled to absolute CBF by employing a global hemispheric CBF value as measured by the nontomographic TTXe clearance method.« less

Intraoperative laser speckle contrast imaging improves the stability of rodent middle cerebral artery occlusion model

NASA Astrophysics Data System (ADS)

Yuan, Lu; Li, Yao; Li, Hangdao; Lu, Hongyang; Tong, Shanbao

2015-09-01

Rodent middle cerebral artery occlusion (MCAO) model is commonly used in stroke research. Creating a stable infarct volume has always been challenging for technicians due to the variances of animal anatomy and surgical operations. The depth of filament suture advancement strongly influences the infarct volume as well. We investigated the cerebral blood flow (CBF) changes in the affected cortex using laser speckle contrast imaging when advancing suture during MCAO surgery. The relative CBF drop area (CBF50, i.e., the percentage area with CBF less than 50% of the baseline) showed an increase from 20.9% to 69.1% when the insertion depth increased from 1.6 to 1.8 cm. Using the real-time CBF50 marker to guide suture insertion during the surgery, our animal experiments showed that intraoperative CBF-guided surgery could significantly improve the stability of MCAO with a more consistent infarct volume and less mortality.

Feasibility of conductivity imaging using subject eddy currents induced by switching of MRI gradients.

PubMed

Oran, Omer Faruk; Ider, Yusuf Ziya

2017-05-01

To investigate the feasibility of low-frequency conductivity imaging based on measuring the magnetic field due to subject eddy currents induced by switching of MRI z-gradients. We developed a simulation model for calculating subject eddy currents and the magnetic fields they generate (subject eddy fields). The inverse problem of obtaining conductivity distribution from subject eddy fields was formulated as a convection-reaction partial differential equation. For measuring subject eddy fields, a modified spin-echo pulse sequence was used to determine the contribution of subject eddy fields to MR phase images. In the simulations, successful conductivity reconstructions were obtained by solving the derived convection-reaction equation, suggesting that the proposed reconstruction algorithm performs well under ideal conditions. However, the level of the calculated phase due to the subject eddy field in a representative object indicates that this phase is below the noise level and cannot be measured with an uncertainty sufficiently low for accurate conductivity reconstruction. Furthermore, some artifacts other than random noise were observed in the measured phases, which are discussed in relation to the effects of system imperfections during readout. Low-frequency conductivity imaging does not seem feasible using basic pulse sequences such as spin-echo on a clinical MRI scanner. Magn Reson Med 77:1926-1937, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Correction of geometric distortion in Propeller echo planar imaging using a modified reversed gradient approach

PubMed Central

Chang, Hing-Chiu; Chuang, Tzu-Chao; Wang, Fu-Nien; Huang, Teng-Yi; Chung, Hsiao-Wen

2013-01-01

Objective This study investigates the application of a modified reversed gradient algorithm to the Propeller-EPI imaging method (periodically rotated overlapping parallel lines with enhanced reconstruction based on echo-planar imaging readout) for corrections of geometric distortions due to the EPI readout. Materials and methods Propeller-EPI acquisition was executed with 360-degree rotational coverage of the k-space, from which the image pairs with opposite phase-encoding gradient polarities were extracted for reversed gradient geometric and intensity corrections. The spatial displacements obtained on a pixel-by-pixel basis were fitted using a two-dimensional polynomial followed by low-pass filtering to assure correction reliability in low-signal regions. Single-shot EPI images were obtained on a phantom, whereas high spatial resolution T2-weighted and diffusion tensor Propeller-EPI data were acquired in vivo from healthy subjects at 3.0 Tesla, to demonstrate the effectiveness of the proposed algorithm. Results Phantom images show success of the smoothed displacement map concept in providing improvements of the geometric corrections at low-signal regions. Human brain images demonstrate prominently superior reconstruction quality of Propeller-EPI images with modified reversed gradient corrections as compared with those obtained without corrections, as evidenced from verification against the distortion-free fast spin-echo images at the same level. Conclusions The modified reversed gradient method is an effective approach to obtain high-resolution Propeller-EPI images with substantially reduced artifacts. PMID:23630654

TU-EF-BRA-03: Free Induction Decay (without the Decay) and Spin-Echo Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Price, R.

NMR, and Proton Density MRI of the 1D Patient - Anthony Wolbarst Net Voxel Magnetization, m(x,t). T1-MRI; The MRI Device - Lisa Lemen ‘Classical’ NMR; FID Imaging in 1D via k-Space - Nathan Yanasak Spin-Echo; S-E/Spin Warp in a 2D Slice - Ronald Price Magnetic resonance imaging not only reveals the structural, anatomic details of the body, as does CT, but also it can provide information on the physiological status and pathologies of its tissues, like nuclear medicine. It can display high-quality slice and 3D images of organs and vessels viewed from any perspective, with resolution better than 1 mm.more » MRI is perhaps most extraordinary and notable for the plethora of ways in which it can create unique forms of image contrast, reflective of fundamentally different biophysical phenomena. As with ultrasound, there is no risk from ionizing radiation to the patient or staff, since no X-rays or radioactive nuclei are involved. Instead, MRI harnesses magnetic fields and radio waves to probe the stable nuclei of the ordinary hydrogen atoms (isolated protons) occurring in water and lipid molecules within and around cells. MRI consists, in essence, of creating spatial maps of the electromagnetic environments around these hydrogen nuclei. Spatial variations in the proton milieus can be related to clinical differences in the biochemical and physiological properties and conditions of the associated tissues. Imaging of proton density (PD), and of the tissue proton spin relaxation times known as T1 and T2, all can reveal important clinical information, but they do so with approaches so dissimilar from one another that each is chosen for only certain clinical situations. T1 and T2 in a voxel are determined by different aspects of the rotations and other motions of the water and lipid molecules involved, as constrained by the local biophysical surroundings within and between its cells – and they, in turn, depend on the type of tissue and its state of health. Three other common applications of MRI exploit its capability to detect and image distinct movements of fluids: MR angiography (MRA), which rivals CT angiography but often requires no contrast medium, monitors the bulk flow of blood; functional MRI ( f MRI), distinguishes the perfusion of oxygenated blood from that of de-oxygenated, and lights up parts of the brain that are activated by a stimulus, rather like PET; and diffusion tensor imaging (DTI) indicates the diffusion of free water along tracts of axons, thereby bringing nerve trunks into view. There are variants on all of these themes, and on others as well. Magnetic Resonance Spectroscopy (MRS), for example, can perform non-invasive ‘virtual biopsies’ that allow identification of certain cancers and other lesions. And an MRI-guided needle biopsy can sample brain tissue from a region only millimeters in dimensions. MRI, however, involves deeper and more complex aspects of physics, technology, and biology than do most other imaging modalities, and it is widely considered to be correspondingly more difficult to learn. We could probably cover all of this rather comprehensively if we had 50 hours available rather than 2 ̶ but, to paraphrase a former Secretary of Defense, you tell your story in the time you have allotted. The four presenters and another physicist, Kevin King from GE, have combined their efforts to co-author a single slide show that describes essentials of MRI as simply as possible. It is obviously far from thorough, but hopefully it will succeed in explaining some of the basics in a simplified but still valid fashion; in providing a taste of the numerous capabilities and complexities of the modality; and in whetting your appetite to learn more. Part I. NMR, and Proton Density MRI of the 1D Patient (Wolbarst), begins with an introductory case study that illustrates a half dozen ways in which MRI provides valuable clinical information. It then explores the nuclear magnetic resonance (NMR) phenomenon, which underlies MRI. NMR can be introduced with either of two approaches. In the first, one thinks (loosely) of the nuclei of hydrogen atoms as (rotating and charged and therefore) magnetic objects, whose spin-axes tend to align in a strong external magnetic field, much like a compass needle. As with the Bohr atom, this spin-up/spin-down picture is a highly abridged version of the full quantum mechanical treatment, but still it leads to some useful, legitimate pictures of the NMR process occurring within a voxel: When RF photons of the correct (Larmor) frequency elevate protons in a fixed magnetic field out of their lower-energy spin state into the upper, the NMR phenomenon is indicated by the detectable absorption of RF power. With the addition of a linear gradient field along a multi-voxel, one-dimensional patient/phantom, as well, we can determine the water content of each compartment – an example of a real MRI study, albeit in 1D. Part I concludes with a discussion of the net magnetization at position x, m0(x), under conditions of dynamic thermal equilibrium, which leads into: Part II. Net Voxel Magnetization, m(x,t); T1-MRI; The MRI Device (Lemen), investigates the biophysics of the form of proton spin relaxation process characterized by the time T1. It then moves on to the creation of an MR image that displays the spatial variation in the values of this clinically relevant parameter, again in 1D. Finally, the design and workings of a clinical MRI machine are sketched, in preparation for: Part III. ‘Classical’ NMR; FID Imaging in 1D via k-Space (Yanasak) presents the second standard approach to NMR and MRI, the classical model. It focuses on the time dependence of the net nuclear magnetization, m(x,t), the overall magnetic field generated by the cohort of protons in the voxel at position x. Quite remarkably, this nuclear net magnetization itself acts in a strong magnetic field like a gyroscope in a gravitational field. This tack is better for explaining Free Induction Decay (FID), which involves a brief introduction to the Fourier transform and k-space. This leads to conventional Spin-Echo (S-E) reconstruction techniques for creating clinical images from raw data, and sets the stage for: Part IV. Spin-Echo; S-E / Spin Warp in a 2D Slice (Price) discusses application of the S- E sequence of radiofrequency pulses and gradient magnetic fields to the 1D patient. T2 is introduced but not explained. This Part also considers how to manipulate the image acquisition parameters so as to generate clinical pictures with contrast dominated by spatial variations in PD, T1, or T2. We conclude by demonstrating the spin-warp approach to imaging in 2D with a simple 2×2, 4-voxel example. Much of this material is presented in more detail in the chapter “MRI of the One-dimensional Patient, Part I”, in Advances in Medical Physics, Vol 5 (2014). Copies are on display at the Medical Physics Publishing booth. Learning Objectives: The participant will learn about the processes of NMR and T1 spin relaxation in a tissue voxel in a uniform magnetic field. The participant will learn about combining spin-up/spin-down NMR and T1 processes with a linear gradient to effect frequency-encoding of voxel spatial position. This approach can be used to create proton density and T1 MRI maps, respectively, of the contents of multi-voxel 1D phantoms. The participant will learn about how the ‘classical’ model of NMR it can generate Free Induction Decay (FID) images of 1D phantoms, which involves the use of the Fourier transform in k-space. This can lead simply into standard Spin-Echo images. The participant will learn about extending Spin-Echo imaging into 2 and more dimensions.« less

Electrical detection of nuclear spins in organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Malissa, H.; Kavand, M.; Waters, D. P.; Lupton, J. M.; Vardeny, Z. V.; Saam, B.; Boehme, C.

2014-03-01

We present pulsed combined electrically detected electron paramagnetic and nuclear magnetic resonance experiments on MEH-PPV OLEDs. Spin dynamics in these structures are governed by hyperfine interactions between charge carriers and the surrounding hydrogen nuclei, which are abundant in these materials. Hyperfine coupling has been observed by monitoring the device current during coherent spin excitation. Electron spin echoes (ESEs) are detected by applying one additional readout pulse at the time of echo formation. This allows for the application of high-resolution spectroscopy based on ESE detection, such as electron spin echo envelope modulation (ESEEM) and electron nuclear double resonance (ENDOR) available for electrical detection schemes. We conduct electrically detected ESEEM and ENDOR experiments and show how hyperfine interactions in MEH-PPV with and without deuterated polymer side groups can be observed by device current measurements. We acknowledge support by the Department of Energy, Office of Basic Energy Sciences under Award #DE-SC0000909.

Cerebral perfusion characteristics show differences in younger versus older children with sickle cell anaemia: Results from a multiple-inflow-time arterial spin labelling study.

PubMed

Kawadler, Jamie M; Hales, Patrick W; Barker, Simon; Cox, Timothy C S; Kirkham, Fenella J; Clark, Chris A

2018-03-30

Sickle cell anaemia (SCA) is associated with chronic anaemia and oxygen desaturation, which elevate cerebral blood flow (CBF) and increase the risk of neurocognitive complications. Arterial spin labelling (ASL) provides a methodology for measuring CBF non-invasively; however, ASL techniques using only a single inflow time are not sufficient to fully characterize abnormal haemodynamic behaviour in SCA. This study investigated haemodynamic parameters from a multi-inflow-time ASL acquisition in younger (8-12 years) and older (13-18 years) children with SCA with and without silent cerebral infarction (SCI+/-) (n = 20 and 19 respectively, 6 and 4 SCI+ respectively) and healthy controls (n = 9 and 7 respectively). Compared with controls, CBF was elevated globally in both groups of patients. In the younger SCA patients, blood oxygen content was negatively correlated with CBF in the middle and posterior cerebral artery territories and significantly positively correlated with bolus arrival time (BAT) in the anterior and middle cerebral artery territories. In older children, SCA patients had significantly shorter BAT than healthy controls and there was a significant negative correlation between CBF and oxygen content only in the territory of the posterior cerebral artery, with a trend for a correlation in the anterior cerebral artery but no relationship for the middle cerebral artery territory. In the younger group, SCI+ patients had significantly higher CBF in the posterior cerebral artery territory (SCI+ mean = 92.78 ml/100 g/min; SCI- mean = 72.71 ml/100 g/min; F = 4.28, p = 0.04), but this no longer reached significance when two children with abnormal transcranial Doppler and one with haemoglobin SC disease were excluded, and there were no significant differences between patients with and without SCI in the older children. With age, there appears to be increasing disparity between patients and controls in terms of the relationship between CBF and oxygen content in the anterior circulation, potentially predicting the risk of acute and chronic compromise of brain tissue. Copyright © 2018 John Wiley & Sons, Ltd.

Diffusion-weighted MR imaging findings of kidneys in patients with early phase of obstruction.

PubMed

Bozgeyik, Zulkif; Kocakoc, Ercan; Sonmezgoz, Fitnet

2009-04-01

Diffusion-weighted (DW) magnetic resonance (MR) imaging is an MR technique used to show molecular diffusion. The apparent diffusion coefficient (ADC), as a quantitative parameter calculated from the DW MR images. The purpose of this study is to evaluate the ability of DW MR imaging in early phase of obstruction due to urolithiasis. Twenty-six patients with acute dilatation of the pelvicalyceal system detected by intravenous urography were included in this study. MR imaging was performed using a 1.5 T whole-body superconducting MR scanner. DW imaging can be performed using single-shot spin-echo, echo-planar imaging (EPI) sequences with the following diffusion gradient b values: 100, 600, 1000 s/mm(2). Circular region of interest (ROI) was placed in the renal parenchyma for the measurement of ADC values in the normal and obstructed kidney. For statistical analyses, Paired t test were used. In spite of obstructed kidneys had the lower ADC values compared to normal kidneys, these alterations were statistically insignificant. We did not observe significantly different ADC values of early phase of obstructed kidneys compared to normal kidneys.

Induction and imaging of photothrombotic stroke in conscious and freely moving rats

NASA Astrophysics Data System (ADS)

Lu, Hongyang; Li, Yao; Yuan, Lu; Li, Hangdao; Lu, Xiaodan; Tong, Shanbao

2014-09-01

In experimental stroke research, anesthesia is common and serves as a major reason for translational failure. Real-time cerebral blood flow (CBF) monitoring during stroke onset can provide important information for the prediction of brain injury; however, this is difficult to achieve in clinical practice due to various technical problems. We created a photothrombotic focal ischemic stroke model utilizing our self-developed miniature headstage in conscious and freely moving rats. In this model, a high spatiotemporal resolution imager using laser speckle contrast imaging technology was integrated to acquire real-time two-dimensional CBF information during thrombosis. The feasibility, stability, and reliability of the system were tested in terms of CBF, behavior, and T2-weighted magnetic resonance imaging (MRI) findings. After completion of occlusion, the CBF in the targeted cortex of the stroke group was reduced to 16±9% of the baseline value. The mean infarct volume measured by MRI 24 h postmodeling was 77±11 mm3 and correlated well with CBF (R2=0.74). This rodent model of focal cerebral ischemia and real-time blood flow imaging opens the possibility of performing various fundamental and translational studies on stroke without the influence of anesthetics.

Exchange-Mediated Contrast Agents for Spin-Lock Imaging

PubMed Central

Cobb, Jared G.; Xie, Jingping; Li, Ke; Gochberg, Daniel F.; Gore, John C.

2011-01-01

Measurements of relaxation rates in the rotating frame with spin-locking (SL) techniques are sensitive to substances with exchanging protons with appropriate chemical shifts. We develop a novel approach to exchange rate selective imaging based on measured T1ρ dispersion with applied locking field strength, and demonstrate the method on samples containing the X-ray contrast agent Iohexol (IO) with and without cross-linked bovine serum albumin (BSA). T1ρ dispersion of water in the phantoms was measured with a Varian 9.4T magnet by an on-resonance SL pulse with fast spin-echo readout, and the results used to estimate exchange rates. The IO phantom alone gave a fitted exchange rate of ~1 kHz, BSA alone was ~11 kHz, and in combination gave rates in between. By using these estimated rates, we demonstrate how a novel SL imaging method may be used to enhance contrast due to the presence of a contrast agent whose protons have specific exchange rates. PMID:21954094

A comparison of multi-echo spin-echo and triple-echo steady-state T2 mapping for in vivo evaluation of articular cartilage.

PubMed

Juras, Vladimir; Bohndorf, Klaus; Heule, Rahel; Kronnerwetter, Claudia; Szomolanyi, Pavol; Hager, Benedikt; Bieri, Oliver; Zbyn, Stefan; Trattnig, Siegfried

2016-06-01

To assess the clinical relevance of T2 relaxation times, measured by 3D triple-echo steady-state (3D-TESS), in knee articular cartilage compared to conventional multi-echo spin-echo T2-mapping. Thirteen volunteers and ten patients with focal cartilage lesions were included in this prospective study. All subjects underwent 3-Tesla MRI consisting of a multi-echo multi-slice spin-echo sequence (CPMG) as a reference method for T2 mapping, and 3D TESS with the same geometry settings, but variable acquisition times: standard (TESSs 4:35min) and quick (TESSq 2:05min). T2 values were compared in six different regions in the femoral and tibial cartilage using a Wilcoxon signed ranks test and the Pearson correlation coefficient (r). The local ethics committee approved this study, and all participants gave written informed consent. The mean quantitative T2 values measured by CPMG (mean: 46±9ms) in volunteers were significantly higher compared to those measured with TESS (mean: 31±5ms) in all regions. Both methods performed similarly in patients, but CPMG provided a slightly higher difference between lesions and native cartilage (CPMG: 90ms→61ms [31%],p=0.0125;TESS 32ms→24ms [24%],p=0.0839). 3D-TESS provides results similar to those of a conventional multi-echo spin-echo sequence with many benefits, such as shortening of total acquisition time and insensitivity to B1 and B0 changes. • 3D-TESS T 2 mapping provides clinically comparable results to CPMG in shorter scan-time. • Clinical and investigational studies may benefit from high temporal resolution of 3D-TESS. • 3D-TESS T 2 values are able to differentiate between healthy and damaged cartilage.

Anomalous Diffusion Measured by a Twice-Refocused Spin Echo Pulse Sequence: Analysis Using Fractional Order Calculus

PubMed Central

2011-01-01

Purpose To theoretically develop and experimentally validate a formulism based on a fractional order calculus (FC) diffusion model to characterize anomalous diffusion in brain tissues measured with a twice-refocused spin-echo (TRSE) pulse sequence. Materials and Methods The FC diffusion model is the fractional order generalization of the Bloch-Torrey equation. Using this model, an analytical expression was derived to describe the diffusion-induced signal attenuation in a TRSE pulse sequence. To experimentally validate this expression, a set of diffusion-weighted (DW) images was acquired at 3 Tesla from healthy human brains using a TRSE sequence with twelve b-values ranging from 0 to 2,600 s/mm2. For comparison, DW images were also acquired using a Stejskal-Tanner diffusion gradient in a single-shot spin-echo echo planar sequence. For both datasets, a Levenberg-Marquardt fitting algorithm was used to extract three parameters: diffusion coefficient D, fractional order derivative in space β, and a spatial parameter μ (in units of μm). Using adjusted R-squared values and standard deviations, D, β and μ values and the goodness-of-fit in three specific regions of interest (ROI) in white matter, gray matter, and cerebrospinal fluid were evaluated for each of the two datasets. In addition, spatially resolved parametric maps were assessed qualitatively. Results The analytical expression for the TRSE sequence, derived from the FC diffusion model, accurately characterized the diffusion-induced signal loss in brain tissues at high b-values. In the selected ROIs, the goodness-of-fit and standard deviations for the TRSE dataset were comparable with the results obtained from the Stejskal-Tanner dataset, demonstrating the robustness of the FC model across multiple data acquisition strategies. Qualitatively, the D, β, and μ maps from the TRSE dataset exhibited fewer artifacts, reflecting the improved immunity to eddy currents. Conclusion The diffusion-induced signal attenuation in a TRSE pulse sequence can be described by an FC diffusion model at high b-values. This model performs equally well for data acquired from the human brain tissues with a TRSE pulse sequence or a conventional Stejskal-Tanner sequence. PMID:21509877

Anomalous diffusion measured by a twice-refocused spin echo pulse sequence: analysis using fractional order calculus.

PubMed

Gao, Qing; Srinivasan, Girish; Magin, Richard L; Zhou, Xiaohong Joe

2011-05-01

To theoretically develop and experimentally validate a formulism based on a fractional order calculus (FC) diffusion model to characterize anomalous diffusion in brain tissues measured with a twice-refocused spin-echo (TRSE) pulse sequence. The FC diffusion model is the fractional order generalization of the Bloch-Torrey equation. Using this model, an analytical expression was derived to describe the diffusion-induced signal attenuation in a TRSE pulse sequence. To experimentally validate this expression, a set of diffusion-weighted (DW) images was acquired at 3 Tesla from healthy human brains using a TRSE sequence with twelve b-values ranging from 0 to 2600 s/mm(2). For comparison, DW images were also acquired using a Stejskal-Tanner diffusion gradient in a single-shot spin-echo echo planar sequence. For both datasets, a Levenberg-Marquardt fitting algorithm was used to extract three parameters: diffusion coefficient D, fractional order derivative in space β, and a spatial parameter μ (in units of μm). Using adjusted R-squared values and standard deviations, D, β, and μ values and the goodness-of-fit in three specific regions of interest (ROIs) in white matter, gray matter, and cerebrospinal fluid, respectively, were evaluated for each of the two datasets. In addition, spatially resolved parametric maps were assessed qualitatively. The analytical expression for the TRSE sequence, derived from the FC diffusion model, accurately characterized the diffusion-induced signal loss in brain tissues at high b-values. In the selected ROIs, the goodness-of-fit and standard deviations for the TRSE dataset were comparable with the results obtained from the Stejskal-Tanner dataset, demonstrating the robustness of the FC model across multiple data acquisition strategies. Qualitatively, the D, β, and μ maps from the TRSE dataset exhibited fewer artifacts, reflecting the improved immunity to eddy currents. The diffusion-induced signal attenuation in a TRSE pulse sequence can be described by an FC diffusion model at high b-values. This model performs equally well for data acquired from the human brain tissues with a TRSE pulse sequence or a conventional Stejskal-Tanner sequence. Copyright © 2011 Wiley-Liss, Inc.

[Comparison of susceptibility artifacts generated by microchips with different geometry at 1.5 Tesla magnet resonance imaging. A phantom pilot study referring to the ASTM standard test method F2119-07].

PubMed

Dengg, S; Kneissl, S

2013-01-01

Ferromagnetic material in microchips, used for animal identification, causes local signal increase, signal void or distortion (susceptibility artifact) on MR images. To measure the impact of microchip geometry on the artifact's size, an MRI phantom study was performed. Microchips of the labels Datamars®, Euro-I.D.® and Planet-ID® (n  =  15) were placed consecutively in a phantom and examined with respect to the ASTM Standard Test Method F2119-07 using spin echo (TR 500 ms, TE 20 ms), gradient echo (TR 300 ms, TE 15 ms, flip angel 30°) and otherwise constant imaging parameters (slice thickness 3 mm, field of view 250 x 250 mm, acquisition matrix 256 x 256 pixel, bandwidth 32 kHz) at 1.5 Tesla. Image acquisition was undertaken with a microchip positioned in the x- and z-direction and in each case with a phase-encoding direction in the y- and z-direction. The artifact size was determined with a) a measurement according to the test method F2119-07 using a homogeneous point operation, b) signal intensity measurement according to Matsuura et al. and c) pixel counts in the artifact according to Port and Pomper. There was a significant difference in artifact size between the three microchips tested (Wilcoxon p = 0.032). A two- to three-fold increase in microchip volume generated an up to 76% larger artifact, depending on the sequence type, phase-encoding direction and chip position to B0. The smaller the microchip geometry, the less is the susceptibility artifact. Spin echoes (SE) generated smaller artifacts than gradient echoes (GE). In relation to the spatial measurement of the artifact, the switch in phase-encoding direction had less influence on the artifact size in GE- than in SE-sequences. However, the artifact shape and direction of SE-sequences can be changed by altering the phase. The artifact size, caused by the microchip, plays a major clinical role in the evaluation of MRI from the head, shoulder and neck regions.

T2 relaxation time is related to liver fibrosis severity

PubMed Central

Siqueira, Luiz; Uppal, Ritika; Alford, Jamu; Fuchs, Bryan C.; Yamada, Suguru; Tanabe, Kenneth; Chung, Raymond T.; Lauwers, Gregory; Chew, Michael L.; Boland, Giles W.; Sahani, Duhyant V.; Vangel, Mark; Hahn, Peter F.; Caravan, Peter

2016-01-01

Background The grading of liver fibrosis relies on liver biopsy. Imaging techniques, including elastography and relaxometric, techniques have had varying success in diagnosing moderate fibrosis. The goal of this study was to determine if there is a relationship between the T2-relaxation time of hepatic parenchyma and the histologic grade of liver fibrosis in patients with hepatitis C undergoing both routine, liver MRI and liver biopsy, and to validate our methodology with phantoms and in a rat model of liver fibrosis. Methods This study is composed of three parts: (I) 123 patients who underwent both routine, clinical liver MRI and biopsy within a 6-month period, between July 1999 and January 2010 were enrolled in a retrospective study. MR imaging was performed at 1.5 T using dual-echo turbo-spin echo equivalent pulse sequence. T2 relaxation time of liver parenchyma in patients was calculated by mono-exponential fit of a region of interest (ROI) within the right lobe correlating to histopathologic grading (Ishak 0–6) and routine serum liver inflammation [aspartate aminotransferase (AST) and alanine aminotransferase (ALT)]. Statistical comparison was performed using ordinary logistic and ordinal logistic regression and ANOVA comparing T2 to Ishak fibrosis without and using AST and ALT as covariates; (II) a phantom was prepared using serial dilutions of dextran coated magnetic iron oxide nanoparticles. T2 weighed imaging was performed by comparing a dual echo fast spin echo sequence to a Carr-Purcell-Meigboom-Gill (CPMG) multi-echo sequence at 1.5 T. Statistical comparison was performed using a paired t-test; (III) male Wistar rats receiving weekly intraperitoneal injections of phosphate buffer solution (PBS) control (n=4 rats); diethylnitrosamine (DEN) for either 5 (n=5 rats) or 8 weeks (n=4 rats) were MR imaged on a Bruker Pharmascan 4.7 T magnet with a home-built bird-cage coil. T2 was quantified by using a mono-exponential fitting algorithm on multi-slice multi echo T2 weighted data. Statistical comparison was performed using ANOVA. Results (I) Histopathologic evaluation of both rat and human livers demonstrated no evidence of steatosis or hemochromatosis There was a monotonic increase in mean T2 value with increasing degree of fibrosis (control 65.4±2.9 ms, n=6 patients); mild (Ishak 1–2) 66.7±1.9 ms (n=30); moderate (Ishak 3–4) 71.6±1.7 ms (n=26); severe (Ishak 5–6) 72.4±1.4 ms (n=61); with relatively low standard error (~2.9 ms). There was a statistically significant difference between degrees of mild (Ishak <4) vs. moderate to severe fibrosis (Ishak >4) (P=0.03) based on logistic regression of T2 and Ishak, which became insignificant (P=0.07) when using inflammatory markers as covariates. Expanding on this model using ordinal logistic regression, there was significance amongst all 4 groups comparing T2 to Ishak (P=0.01), with significance using inflammation as a covariate (P=0.03) and approaching statistical significance amongst all groups by ANOVA (P=0.07); (II) there was a monotonic increase in T2 and statistical significance (ANOVA P<0.0001) between each rat subgroup [phosphate buffer solution (PBS) 25.2±0.8, DEN 5-week (31.1±1.5), and DEN 9-week (49.4±0.4) ms]; (III) the phantoms that had T2 values within the relevant range for the human liver (e.g., 20–100 ms), demonstrated no statistical difference between two point fits on turbo spin echo (TSE) data and multi-echo CPMG data (P=0.9). Conclusions The finding of increased T2 with liver fibrosis may relate to inflammation that may be an alternative or adjunct to other noninvasive MR imaging based approaches for assessing liver fibrosis. PMID:27190762

Aberrant Cerebral Blood Flow in Response to Hunger and Satiety in Women Remitted from Anorexia Nervosa

PubMed Central

Wierenga, Christina E.; Bischoff-Grethe, Amanda; Rasmusson, Grace; Bailer, Ursula F.; Berner, Laura A.; Liu, Thomas T.; Kaye, Walter H.

2017-01-01

The etiology of pathological eating in anorexia nervosa (AN) remains poorly understood. Cerebral blood flow (CBF) is an indirect marker of neuronal function. In healthy adults, fasting increases CBF, reflecting increased delivery of oxygen and glucose to support brain metabolism. This study investigated whether women remitted from restricting-type AN (RAN) have altered CBF in response to hunger that may indicate homeostatic dysregulation contributing to their ability to restrict food. We compared resting CBF measured with pulsed arterial spin labeling in 21 RAN and 16 healthy comparison women (CW) when hungry (after a 16-h fast) and after a meal. Only remitted subjects were examined to avoid the confounding effects of malnutrition on brain function. Compared to CW, RAN demonstrated a reduced difference in the Hungry − Fed CBF contrast in the right ventral striatum, right subgenual anterior cingulate cortex (pcorr < 0.05) and left posterior insula (punc < 0.05); RAN had decreased CBF when hungry versus fed, whereas CW had increased CBF when hungry versus fed. Moreover, decreased CBF when hungry in the left insula was associated with greater hunger ratings on the fasted day for RAN. This represents the first study to show that women remitted from AN have aberrant resting neurovascular function in homeostatic neural circuitry in response to hunger. Regions involved in homeostatic regulation showed group differences in the Hungry − Fed contrast, suggesting altered cellular energy metabolism in this circuitry that may reduce motivation to eat. PMID:28770207

Aberrant Cerebral Blood Flow in Response to Hunger and Satiety in Women Remitted from Anorexia Nervosa.

PubMed

Wierenga, Christina E; Bischoff-Grethe, Amanda; Rasmusson, Grace; Bailer, Ursula F; Berner, Laura A; Liu, Thomas T; Kaye, Walter H

2017-01-01

The etiology of pathological eating in anorexia nervosa (AN) remains poorly understood. Cerebral blood flow (CBF) is an indirect marker of neuronal function. In healthy adults, fasting increases CBF, reflecting increased delivery of oxygen and glucose to support brain metabolism. This study investigated whether women remitted from restricting-type AN (RAN) have altered CBF in response to hunger that may indicate homeostatic dysregulation contributing to their ability to restrict food. We compared resting CBF measured with pulsed arterial spin labeling in 21 RAN and 16 healthy comparison women (CW) when hungry (after a 16-h fast) and after a meal. Only remitted subjects were examined to avoid the confounding effects of malnutrition on brain function. Compared to CW, RAN demonstrated a reduced difference in the Hungry - Fed CBF contrast in the right ventral striatum, right subgenual anterior cingulate cortex ( p corr  < 0.05) and left posterior insula ( p unc  < 0.05); RAN had decreased CBF when hungry versus fed, whereas CW had increased CBF when hungry versus fed. Moreover, decreased CBF when hungry in the left insula was associated with greater hunger ratings on the fasted day for RAN. This represents the first study to show that women remitted from AN have aberrant resting neurovascular function in homeostatic neural circuitry in response to hunger. Regions involved in homeostatic regulation showed group differences in the Hungry - Fed contrast, suggesting altered cellular energy metabolism in this circuitry that may reduce motivation to eat.

Exercise intensity modulates the change in cerebral blood flow following aerobic exercise in chronic stroke.

PubMed

Robertson, Andrew D; Crane, David E; Rajab, A Saeed; Swardfager, Walter; Marzolini, Susan; Shirzadi, Zahra; Middleton, Laura E; MacIntosh, Bradley J

2015-08-01

The mechanisms supporting functional improvement by aerobic exercise following stroke remain incompletely understood. This study investigated how cycling intensity and aerobic fitness influence cerebral blood flow (CBF) following a single exercise session. Thirteen community-living stroke survivors performed 20 min of semi-recumbent cycling at low and moderate intensities (40-50 and 60-70 % of heart rate reserve, respectively) as determined from an exercise stress test. CBF was quantified by arterial spin labeling MRI at baseline, as well as 30 and 50 min post-exercise. An intensity-dependent effect was observed in the right post-central and supramarginal gyri up to 50 min after exercise (uncorrected p < 0.005, cluster size ≥10). Regional CBF was increased 18 ± 17 % and reduced 8 ± 12 % following moderate- and low-intensity cycling, respectively. In contrast, CBF changes were similar between sessions in the right lentiform nucleus and mid-frontal gyrus, as well as the left temporal and parietal gyri. Aerobic fitness was directly related to posterior cingulate and thalamic CBF, and inversely related to precuneal CBF at rest (R (2) ≥ 0.75); however, no relationship between fitness and the post-exercise change in CBF was observed. Divergent changes in regional CBF were observed in the right parietal cortex following low- and moderate-intensity exercise, which suggests that intensity of prescribed exercise may be useful in optimizing rehabilitation.

Fat suppression with short inversion time inversion-recovery and chemical-shift selective saturation: a dual STIR-CHESS combination prepulse for turbo spin echo pulse sequences.

PubMed

Tanabe, Koji; Nishikawa, Keiichi; Sano, Tsukasa; Sakai, Osamu; Jara, Hernán

2010-05-01

To test a newly developed fat suppression magnetic resonance imaging (MRI) prepulse that synergistically uses the principles of fat suppression via inversion recovery (STIR) and spectral fat saturation (CHESS), relative to pure CHESS and STIR. This new technique is termed dual fat suppression (Dual-FS). To determine if Dual-FS could be chemically specific for fat, the phantom consisted of the fat-mimicking NiCl(2) aqueous solution, porcine fat, porcine muscle, and water was imaged with the three fat-suppression techniques. For Dual-FS and STIR, several inversion times were used. Signal intensities of each image obtained with each technique were compared. To determine if Dual-FS could be robust to magnetic field inhomogeneities, the phantom consisting of different NiCl(2) aqueous solutions, porcine fat, porcine muscle, and water was imaged with Dual-FS and CHESS at the several off-resonance frequencies. To compare fat suppression efficiency in vivo, 10 volunteer subjects were also imaged with the three fat-suppression techniques. Dual-FS could suppress fat sufficiently within the inversion time of 110-140 msec, thus enabling differentiation between fat and fat-mimicking aqueous structures. Dual-FS was as robust to magnetic field inhomogeneities as STIR and less vulnerable than CHESS. The same results for fat suppression were obtained in volunteers. The Dual-FS-STIR-CHESS is an alternative and promising fat suppression technique for turbo spin echo MRI. Copyright 2010 Wiley-Liss, Inc.

Spectral narrowing and spin echo for localized carriers with heavy-tailed L evy distribution of hopping times

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yue, Z.; Mkhitaryan, Vagharsh; Raikh, M. E.

2016-02-02

We study analytically the free induction decay and the spin echo decay originating from the localized carriers moving between the sites which host random magnetic fields. Due to disorder in the site positions and energies, the on-site residence times, , are widely spread according to the L evy distribution. The power-law tail ∝ τ -1-∝ in the distribution of does not affect the conventional spectral narrowing for α > 2, but leads to a dramatic acceleration of the free induction decay in the domain 2 > α > 1. The next abrupt acceleration of the decay takes place as becomesmore » smaller than 1. In the latter domain the decay does not follow a simple-exponent law. To capture the behavior of the average spin in this domain, we solve the evolution equation for the average spin using the approach different from the conventional approach based on the Laplace transform. Unlike the free induction decay, the tail in the distribution of the residence times leads to the slow decay of the spin echo. The echo is dominated by realizations of the carrier motion for which the number of sites, visited by the carrier, is minimal.« less

Regional reduction in cortical blood flow among cognitively impaired adults with relapsing-remitting multiple sclerosis patients

PubMed Central

Hojjat, Seyed-Parsa; Cantrell, Charles Grady; Vitorino, Rita; Feinstein, Anthony; Shirzadi, Zahra; MacIntosh, Bradley J.; Crane, David E.; Zhang, Lying; Morrow, Sarah A; Lee, Liesly; O’Connor, Paul; Carroll, Timothy J.; Aviv, Richard I.

2015-01-01

Purpose Detection of cortical abnormalities in relapsing-remitting multiple sclerosis (RRMS) remains elusive. Structural MRI measures of cortical integrity are limited, although functional techniques such as pseudocontinuous Arterial Spin Labeling (pCASL) show promise as a surrogate marker of disease severity. We sought to determine the utility of pCASL to assess cortical cerebral blood flow (CBF) in RRMS patients with (RRMS-I) and without (RRMS-NI) cognitive impairment. Methods 19 age-matched healthy controls and 39 RRMS patients were prospectively recruited. Cognition was assessed using the MACFIMS battery. Cortical CBF was compared between groups using a mass univariate voxel-based morphometric analysis accounting for demographic and structural variable covariates. Results Cognitive impairment was present in 51.3% of patients. Significant CBF reduction was present in the RRMS-I compared to other groups in left frontal and right superior frontal cortex. Compared to healthy controls, RRMS-I displayed reduced CBF in the frontal, limbic, parietal and temporal cortex and putamen/thalamus. RRMS-I demonstrated reduced left superior frontal lobe cortical CBF compared to RRMS-NI. No significant cortical CBF differences were present between healthy controls and RRMS-NI. Conclusion Significant cortical CBF reduction occurs in RRMS-I compared to healthy controls and RRMS-NI in anatomically significant regions after controlling for structural and demographic differences. PMID:26754799

Imaging of cerebral blood flow in patients with severe traumatic brain injury in the neurointensive care.

PubMed

Rostami, Elham; Engquist, Henrik; Enblad, Per

2014-01-01

Ischemia is a common and deleterious secondary injury following traumatic brain injury (TBI). A great challenge for the treatment of TBI patients in the neurointensive care unit (NICU) is to detect early signs of ischemia in order to prevent further advancement and deterioration of the brain tissue. Today, several imaging techniques are available to monitor cerebral blood flow (CBF) in the injured brain such as positron emission tomography (PET), single-photon emission computed tomography, xenon computed tomography (Xenon-CT), perfusion-weighted magnetic resonance imaging (MRI), and CT perfusion scan. An ideal imaging technique would enable continuous non-invasive measurement of blood flow and metabolism across the whole brain. Unfortunately, no current imaging method meets all these criteria. These techniques offer snapshots of the CBF. MRI may also provide some information about the metabolic state of the brain. PET provides images with high resolution and quantitative measurements of CBF and metabolism; however, it is a complex and costly method limited to few TBI centers. All of these methods except mobile Xenon-CT require transfer of TBI patients to the radiological department. Mobile Xenon-CT emerges as a feasible technique to monitor CBF in the NICU, with lower risk of adverse effects. Promising results have been demonstrated with Xenon-CT in predicting outcome in TBI patients. This review covers available imaging methods used to monitor CBF in patients with severe TBI.

Imaging of Cerebral Blood Flow in Patients with Severe Traumatic Brain Injury in the Neurointensive Care

PubMed Central

Rostami, Elham; Engquist, Henrik; Enblad, Per

2014-01-01

Ischemia is a common and deleterious secondary injury following traumatic brain injury (TBI). A great challenge for the treatment of TBI patients in the neurointensive care unit (NICU) is to detect early signs of ischemia in order to prevent further advancement and deterioration of the brain tissue. Today, several imaging techniques are available to monitor cerebral blood flow (CBF) in the injured brain such as positron emission tomography (PET), single-photon emission computed tomography, xenon computed tomography (Xenon-CT), perfusion-weighted magnetic resonance imaging (MRI), and CT perfusion scan. An ideal imaging technique would enable continuous non-invasive measurement of blood flow and metabolism across the whole brain. Unfortunately, no current imaging method meets all these criteria. These techniques offer snapshots of the CBF. MRI may also provide some information about the metabolic state of the brain. PET provides images with high resolution and quantitative measurements of CBF and metabolism; however, it is a complex and costly method limited to few TBI centers. All of these methods except mobile Xenon-CT require transfer of TBI patients to the radiological department. Mobile Xenon-CT emerges as a feasible technique to monitor CBF in the NICU, with lower risk of adverse effects. Promising results have been demonstrated with Xenon-CT in predicting outcome in TBI patients. This review covers available imaging methods used to monitor CBF in patients with severe TBI. PMID:25071702

A multislice gradient echo pulse sequence for CEST imaging.

PubMed

Dixon, W Thomas; Hancu, Ileana; Ratnakar, S James; Sherry, A Dean; Lenkinski, Robert E; Alsop, David C

2010-01-01

Chemical exchange-dependent saturation transfer and paramagnetic chemical exchange-dependent saturation transfer are agent-mediated contrast mechanisms that depend on saturating spins at the resonant frequency of the exchangeable protons on the agent, thereby indirectly saturating the bulk water. In general, longer saturating pulses produce stronger chemical and paramagnetic exchange-dependent saturation transfer effects, with returns diminishing for pulses longer than T1. This could make imaging slow, so one approach to chemical exchange-dependent saturation transfer imaging has been to follow a long, frequency-selective saturation period by a fast imaging method. A new approach is to insert a short frequency-selective saturation pulse before each spatially selective observation pulse in a standard, two-dimensional, gradient-echo pulse sequence. Being much less than T1 apart, the saturation pulses have a cumulative effect. Interleaved, multislice imaging is straightforward. Observation pulses directed at one slice did not produce observable, unintended chemical exchange-dependent saturation transfer effects in another slice. Pulse repetition time and signal-to noise ratio increase in the normal way as more slices are imaged simultaneously. Copyright (c) 2009 Wiley-Liss, Inc.

A comparative analysis of the dependences of the hemodynamic parameters on changes in ROI's position in perfusion CT scans

NASA Astrophysics Data System (ADS)

Choi, Yong-Seok; Cho, Jae-Hwan; Namgung, Jang-Sun; Kim, Hyo-Jin; Yoon, Dae-Young; Lee, Han-Joo

2013-05-01

This study performed a comparative analysis of cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and mean time-to-peak (TTP) obtained by changing the region of interest's (ROI) anatomical positions, during CT brain perfusion. We acquired axial source images of perfusion CT from 20 patients undergoing CT perfusion exams due to brain trauma. Subsequently, the CBV, CBF, MTT, and TTP values were calculated through data-processing of the perfusion CT images. The color scales for the CBV, CBF, MTT, and TTP maps were obtained using the image data. Anterior cerebral artery (ACA) was taken as the standard ROI for the calculations of the perfusion values. Differences in the hemodynamic average values were compared in a quantitative analysis by placing ROI and the dividing axial images into proximal, middle, and distal segments anatomically. By performing the qualitative analysis using a blind test, we observed changes in the sensory characteristics by using the color scales of the CBV, CBF, and MTT maps in the proximal, middle, and distal segments. According to the qualitative analysis, no differences were found in CBV, CBF, MTT, and TTP values of the proximal, middle, and distal segments and no changes were detected in the color scales of the the CBV, CBF, MTT, and TTP maps in the proximal, middle, and distal segments. We anticipate that the results of the study will useful in assessing brain trauma patients using by perfusion imaging.

Application of calibrated fMRI in Alzheimer's disease.

PubMed

Lajoie, Isabelle; Nugent, Scott; Debacker, Clément; Dyson, Kenneth; Tancredi, Felipe B; Badhwar, AmanPreet; Belleville, Sylvie; Deschaintre, Yan; Bellec, Pierre; Doyon, Julien; Bocti, Christian; Gauthier, Serge; Arnold, Douglas; Kergoat, Marie-Jeanne; Chertkow, Howard; Monchi, Oury; Hoge, Richard D

2017-01-01

Calibrated fMRI based on arterial spin-labeling (ASL) and blood oxygen-dependent contrast (BOLD), combined with periods of hypercapnia and hyperoxia, can provide information on cerebrovascular reactivity (CVR), resting blood flow (CBF), oxygen extraction fraction (OEF), and resting oxidative metabolism (CMRO 2 ). Vascular and metabolic integrity are believed to be affected in Alzheimer's disease (AD), thus, the use of calibrated fMRI in AD may help understand the disease and monitor therapeutic responses in future clinical trials. In the present work, we applied a calibrated fMRI approach referred to as Quantitative O2 (QUO2) in a cohort of probable AD dementia and age-matched control participants. The resulting CBF, OEF and CMRO 2 values fell within the range from previous studies using positron emission tomography (PET) with 15 O labeling. Moreover, the typical parietotemporal pattern of hypoperfusion and hypometabolism in AD was observed, especially in the precuneus, a particularly vulnerable region. We detected no deficit in frontal CBF, nor in whole grey matter CVR, which supports the hypothesis that the effects observed were associated specifically with AD rather than generalized vascular disease. Some key pitfalls affecting both ASL and BOLD methods were encountered, such as prolonged arterial transit times (particularly in the occipital lobe), the presence of susceptibility artifacts obscuring medial temporal regions, and the challenges associated with the hypercapnic manipulation in AD patients and elderly participants. The present results are encouraging and demonstrate the promise of calibrated fMRI measurements as potential biomarkers in AD. Although CMRO 2 can be imaged with 15 O PET, the QUO2 method uses more widely available imaging infrastructure, avoids exposure to ionizing radiation, and integrates with other MRI-based measures of brain structure and function.

Quantification of indirect pathway inhibition by the adenosine A2a antagonist SYN115 in Parkinson disease.

PubMed

Black, Kevin J; Koller, Jonathan M; Campbell, Meghan C; Gusnard, Debra A; Bandak, Stephen I

2010-12-01

Adenosine A(2a) receptor antagonists reduce symptom severity in Parkinson disease (PD) and animal models. Rodent studies support the hypothesis that A(2a) antagonists produce this benefit by reducing the inhibitory output of the basal ganglia indirect pathway. One way to test this hypothesis in humans is to quantify regional pharmacodynamic responses with cerebral blood flow (CBF) imaging. That approach has also been proposed as a tool to accelerate pharmaceutical dose finding, but has not yet been applied in humans to drugs in development. We successfully addressed both these aims with a perfusion magnetic resonance imaging (MRI) study of the novel adenosine A(2a) antagonist SYN115. During a randomized, double-blind, placebo-controlled, crossover study in 21 PD patients on levodopa but no agonists, we acquired pulsed arterial spin labeling MRI at the end of each treatment period. SYN115 produced a highly significant decrease in thalamic CBF, consistent with reduced pallidothalamic inhibition via the indirect pathway. Similar decreases occurred in cortical regions whose activity decreases with increased alertness and externally focused attention, consistent with decreased self-reported sleepiness on SYN115. Remarkably, we also derived quantitative pharmacodynamic parameters from the CBF responses to SYN115. These results suggested that the doses tested were on the low end of the effective dose range, consistent with clinical data reported separately. We conclude that (1) SYN115 enters the brain and exerts dose-dependent regional effects, (2) the most prominent of these effects is consistent with deactivation of the indirect pathway as predicted by preclinical studies; and (3) perfusion MRI can provide rapid, quantitative, clinically relevant dose-finding information for pharmaceutical development.

Changes in regional cerebral blood flow in the right cortex homologous to left language areas are directly affected by left hemispheric damage in aphasic stroke patients: evaluation by Tc-ECD SPECT and novel analytic software.

PubMed

Uruma, G; Kakuda, W; Abo, M

2010-03-01

The objective of this study was to clarify the influence of regional cerebral blood flow (rCBF) changes in language-relevant areas of the dominant hemisphere on rCBF in each region in the non-dominant hemisphere in post-stroke aphasic patients. The study subjects were 27 aphasic patients who suffered their first symptomatic stroke in the left hemisphere. In each subject, we measured rCBF by means of 99mTc-ethylcysteinate dimmer single photon emission computed tomography (SPECT). The SPECT images were analyzed by the statistical imaging analysis programs easy Z-score Imaging System (eZIS) and voxel-based stereotactic extraction estimation (vbSEE). Segmented into Brodmann Area (BA) levels, Regions of Interest (ROIs) were set in language-relevant areas bilaterally, and changes in the relative rCBF as average negative and positive Z-values were computed fully automatically. To assess the relationship between rCBF changes of each ROIs in the left and right hemispheres, the Spearman ranked correlation analysis and stepwise multiple regression analysis were applied. Globally, a negative and asymmetric influence of rCBF changes in the language-relevant areas of the dominant hemisphere on the right hemisphere was found. The rCBF decrease in left BA22 significantly influenced the rCBF increase in right BA39, BA40, BA44 and BA45. The results suggested that the chronic increase in rCBF in the right language-relevant areas is due at least in part to reduction in the trancallosal inhibitory activity of the language-dominant left hemisphere caused by the stroke lesion itself and that these relationships are not always symmetric.

Turbo-Proton Echo Planar Spectroscopic Imaging (t-PEPSI) MR technique in the detection of diffuse axonal damage in brain injury. Comparison with Gradient-Recalled Echo (GRE) sequence.

PubMed

Giugni, E; Sabatini, U; Hagberg, G E; Formisano, R; Castriota-Scanderbeg, A

2005-01-01

Diffuse axonal injury (DAI) is a common type of primary neuronal injury in patients with severe traumatic brain injury, and is frequently accompanied by tissue tear haemorrhage. The T2*-weighted gradient-recalled echo (GRE) sequences are more sensitive than T2-weighted spin-echo images for detection of haemorrhage. This study was undertaken to determine whether turbo-PEPSI, an extremely fast multi-echo-planar-imaging sequence, can be used as an alternative to the GRE sequence for detection of DAI. Nineteen patients (mean age 24,5 year) with severe traumatic brain injury (TBI), occurred at least 3 months earlier, underwent a brain MRI study on a 1.5-Tesla scanner. A qualitative evaluation of the turbo-PEPSI sequences was performed by identifying the optimal echo time and in-plane resolution. The number and size of DAI lesions, as well as the signal intensity contrast ratio (SI CR), were computed for each set of GRE and turbo-PEPSI images, and divided according to their anatomic location into lobar and/or deep brain. There was no significant difference between GRE and turbo-PEPSI sequences in the total number of DAI lesions detected (283 vs 225 lesions, respectively). The GRE sequence identified a greater number of hypointense lesions in the temporal lobe compared to the t-PEPSI sequence (72 vs 35, p<0.003), while no significant differences were found for the other brain regions. The SI CR was significantly better (i.e. lower) for the turbo-PEPSI than for the GRE sequence (p<0.00001). Owing to its very short scan time and high sensitivity to the haemorrhage foci, the turbo-PEPSI sequence can be used as an alternative to the GRE to assess brain DAI in severe TBI patients, especially if uncooperative and medically unstable.

Development of PET/MRI with insertable PET for simultaneous PET and MR imaging of human brain.

PubMed

Jung, Jin Ho; Choi, Yong; Jung, Jiwoong; Kim, Sangsu; Lim, Hyun Keong; Im, Ki Chun; Oh, Chang Hyun; Park, Hyun-wook; Kim, Kyung Min; Kim, Jong Guk

2015-05-01

The purpose of this study was to develop a dual-modality positron emission tomography (PET)/magnetic resonance imaging (MRI) with insertable PET for simultaneous PET and MR imaging of the human brain. The PET detector block was composed of a 4 × 4 matrix of detector modules, each consisting of a 4 × 4 array LYSO coupled to a 4 × 4 Geiger-mode avalanche photodiode (GAPD) array. The PET insert consisted of 18 detector blocks, circularly mounted on a custom-made plastic base to form a ring with an inner diameter of 390 mm and axial length of 60 mm. The PET gantry was shielded with gold-plated conductive fabric tapes with a thickness of 0.1 mm. The charge signals of PET detector transferred via 4 m long flat cables were fed into the position decoder circuit. The flat cables were shielded with a mesh-type aluminum sheet with a thickness of 0.24 mm. The position decoder circuit and field programmable gate array-embedded DAQ modules were enclosed in an aluminum box with a thickness of 10 mm and located at the rear of the MR bore inside the MRI room. A 3-T human MRI system with a Larmor frequency of 123.7 MHz and inner bore diameter of 60 cm was used as the PET/MRI hybrid system. A custom-made radio frequency (RF) coil with an inner diameter of 25 cm was fabricated. The PET was positioned between gradient and the RF coils. PET performance was measured outside and inside the MRI scanner using echo planar imaging, spin echo, turbo spin echo, and gradient echo sequences. MRI performance was also evaluated with and without the PET insert. The stability of the newly developed PET insert was evaluated and simultaneous PET and MR images of a brain phantom were acquired. No significant degradation of the PET performance caused by MR was observed when the PET was operated using various MR imaging sequences. The signal-to-noise ratio of MR images was slightly degraded due to the PET insert installed inside the MR bore while the homogeneity was maintained. The change of gain of the 256 GAPD/scintillator elements of a detector block was <3% for 60 min, and simultaneous PET and MR images of a brain phantom were successfully acquired. Experimental results indicate that a compact and lightweight PET insert for hybrid PET/MRI can be developed using GAPD arrays and charge signal transmission method proposed in this study without significant interference.

Nicotine and non-nicotine smoking factors differentially modulate craving, withdrawal and cerebral blood flow as measured with arterial spin labeling.

PubMed

Addicott, Merideth A; Froeliger, Brett; Kozink, Rachel V; Van Wert, Dana M; Westman, Eric C; Rose, Jed E; McClernon, Francis J

2014-11-01

Smoking cessation results in withdrawal symptoms such as craving and negative mood that may contribute to lapse and relapse. Little is known regarding whether these symptoms are associated with the nicotine or non-nicotine components of cigarette smoke. Using arterial spin labeling, we measured resting-state cerebral blood flow (CBF) in 29 adult smokers across four conditions: (1) nicotine patch+denicotinized cigarette smoking, (2) nicotine patch+abstinence from smoking, (3) placebo patch+denicotinized cigarette smoking, and (4) placebo patch+abstinence from smoking. We found that changes in self-reported craving positively correlated with changes in CBF from the denicotinized cigarette smoking conditions to the abstinent conditions. These correlations were found in several regions throughout the brain. Self-reported craving also increased from the nicotine to the placebo conditions, but had a minimal relationship with changes in CBF. The results of this study suggest that the non-nicotine components of cigarette smoke significantly impact withdrawal symptoms and associated brain areas, independently of the effects of nicotine. As such, the effects of non-nicotine factors are important to consider in the design and development of smoking cessation interventions and tobacco regulation.

Nicotine and Non-Nicotine Smoking Factors Differentially Modulate Craving, Withdrawal and Cerebral Blood Flow as Measured with Arterial Spin Labeling

PubMed Central

Addicott, Merideth A; Froeliger, Brett; Kozink, Rachel V; Van Wert, Dana M; Westman, Eric C; Rose, Jed E; McClernon, Francis J

2014-01-01

Smoking cessation results in withdrawal symptoms such as craving and negative mood that may contribute to lapse and relapse. Little is known regarding whether these symptoms are associated with the nicotine or non-nicotine components of cigarette smoke. Using arterial spin labeling, we measured resting-state cerebral blood flow (CBF) in 29 adult smokers across four conditions: (1) nicotine patch+denicotinized cigarette smoking, (2) nicotine patch+abstinence from smoking, (3) placebo patch+denicotinized cigarette smoking, and (4) placebo patch+abstinence from smoking. We found that changes in self-reported craving positively correlated with changes in CBF from the denicotinized cigarette smoking conditions to the abstinent conditions. These correlations were found in several regions throughout the brain. Self-reported craving also increased from the nicotine to the placebo conditions, but had a minimal relationship with changes in CBF. The results of this study suggest that the non-nicotine components of cigarette smoke significantly impact withdrawal symptoms and associated brain areas, independently of the effects of nicotine. As such, the effects of non-nicotine factors are important to consider in the design and development of smoking cessation interventions and tobacco regulation. PMID:24820539

Detection of cerebrospinal fluid leakage: initial experience with three-dimensional fast spin-echo magnetic resonance myelography.

PubMed

Tomoda, Y; Korogi, Y; Aoki, T; Morioka, T; Takahashi, H; Ohno, M; Takeshita, I

2008-03-01

The pathogenesis of cerebrospinal fluid (CSF) hypovolemia is supposed to be caused by CSF leakage through small dural defects. To compare source three-dimensional (3D) fast spin-echo (FSE) images of magnetic resonance (MR) myelography with radionuclide cisternography findings, and to evaluate the feasibility of MR myelography in the detection of CSF leakage. A total of 67 patients who were clinically suspected of CSF hypovolemia underwent indium-111 radionuclide cisternography, and 27 of those who had direct findings of CSF leakage were selected for evaluation. MR myelography with 3D FSE sequences (TR/TE 6000/203 ms) was performed at the lumbar spine for all patients. We evaluated source images and maximum intensity projection (MIP) images of MR myelography, and the findings were correlated with radionuclide cisternography findings. MR myelography of five healthy volunteers was used as a reference. The MR visibility of the CSF leakage was graded as definite (leakage clearly visible), possible (leakage poorly seen), or absent (not shown). CSF leakage was identified with source 3D FSE images in 22 (81.5%) of 27 patients. Of the 22 patients, 16 were graded as definite and six were graded as possible. For the definite cases, 3D FSE images clearly showed the extent of the leaked CSF in the paraspinal structures. In the remaining five patients with absent findings, radionuclide cisternography showed only slight radionuclide activity out of the arachnoid space. Source 3D FSE images of MR myelography seem useful in the detection of CSF leakage. Invasive radionuclide cisternography may be reserved for equivocal cases only.

(Charge separation in photoredox reactions). Informal annual technical progress report, October 1, 1981-October 1, 1982. [N,N,N',N'tetramethylbenzidine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kevan, L.

1982-10-21

During this period work has focused on the structural aspects of photoinduced charge separation in micellar media with initial forays into vesicular media. The primary techniques utilized are electron spin resonance and electron spin echo spectrometry. The analysis of electron spin echo modulation gives a unique handle on very weak hyperfine interactions thus providing a new structural tool for this general problem. Electron spin resonance and electron spin echo studies of the photoionization of N,N,N',N'tetramethylbenzidine (TMB) to give the cation radical have been carried out in anionic, cationic and nonionic micellar solutions frozen to 77/sup 0/K. The photoionization efficiency ofmore » TMB has also been studied in micelles with varying alkyl chain lengths of the surfactant. Stearic acid nitroxide spin probes have also been used to determine some structural aspects of the location of the neutral TMB molecule in anionic micelles before photoionization. The nitroxide work in which the nitroxide is acting as an electron acceptor also shows that a suitable electron acceptor can be located within the micellar structure. The effect of inorganic solutes on the efficiency of the photoionization of TMB in frozen micelles has also been studied. A series of electron scavenger studies have been initiated to study the effect on TMB photoionization efficiency. Electron spin echo detection of laser photogenerated TMB cation in liquid sodium dodecyl sulfate solutions at room temperature has recently been observed.« less

Reduction of respiratory ghosting motion artifacts in conventional two-dimensional multi-slice Cartesian turbo spin-echo: which k-space filling order is the best?

PubMed

Inoue, Yuuji; Yoneyama, Masami; Nakamura, Masanobu; Takemura, Atsushi

2018-06-01

The two-dimensional Cartesian turbo spin-echo (TSE) sequence is widely used in routine clinical studies, but it is sensitive to respiratory motion. We investigated the k-space orders in Cartesian TSE that can effectively reduce motion artifacts. The purpose of this study was to demonstrate the relationship between k-space order and degree of motion artifacts using a moving phantom. We compared the degree of motion artifacts between linear and asymmetric k-space orders. The actual spacing of ghost artifacts in the asymmetric order was doubled compared with that in the linear order in the free-breathing situation. The asymmetric order clearly showed less sensitivity to incomplete breath-hold at the latter half of the imaging period. Because of the actual number of partitions of the k-space and the temporal filling order, the asymmetric k-space order of Cartesian TSE was superior to the linear k-space order for reduction of ghosting motion artifacts.

Spatial heterogeneity of the relation between resting-state connectivity and blood flow: an important consideration for pharmacological studies.

PubMed

Khalili-Mahani, Najmeh; van Osch, Matthias J; de Rooij, Mark; Beckmann, Christian F; van Buchem, Mark A; Dahan, Albert; van Gerven, Johannes M; Rombouts, Serge A R B

2014-03-01

Resting state fMRI (RSfMRI) and arterial spin labeling (ASL) provide the field of pharmacological Neuroimaging tool for investigating states of brain activity in terms of functional connectivity or cerebral blood flow (CBF). Functional connectivity reflects the degree of synchrony or correlation of spontaneous fluctuations--mostly in the blood oxygen level dependent (BOLD) signal--across brain networks; but CBF reflects mean delivery of arterial blood to the brain tissue over time. The BOLD and CBF signals are linked to common neurovascular and hemodynamic mechanisms that necessitate increased oxygen transportation to the site of neuronal activation; however, the scale and the sources of variation in static CBF and spatiotemporal BOLD correlations are likely different. We tested this hypothesis by examining the relation between CBF and resting-state-network consistency (RSNC)--representing average intranetwork connectivity, determined from dual regression analysis with eight standard networks of interest (NOIs)--in a crossover placebo-controlled study of morphine and alcohol. Overall, we observed spatially heterogeneous relations between RSNC and CBF, and between the experimental factors (drug-by-time, time, drug and physiological rates) and each of these metrics. The drug-by-time effects on CBF were significant in all networks, but significant RSNC changes were limited to the sensorimotor, the executive/salience and the working memory networks. The post-hoc voxel-wise statistics revealed similar dissociations, perhaps suggesting differential sensitivity of RSNC and CBF to neuronal and vascular endpoints of drug actions. The spatial heterogeneity of RSNC/CBF relations encourages further investigation into the role of neuroreceptor distribution and cerebrovascular anatomy in predicting spontaneous fluctuations under drugs. Copyright © 2012 Wiley Periodicals, Inc.

Ultrafast NMR diffusion measurements exploiting chirp spin echoes.

PubMed

Ahola, Susanna; Mankinen, Otto; Telkki, Ville-Veikko

2017-04-01

Standard diffusion NMR measurements require the repetition of the experiment multiple times with varying gradient strength or diffusion delay. This makes the experiment time-consuming and restricts the use of hyperpolarized substances to boost sensitivity. We propose a novel single-scan diffusion experiment, which is based on spatial encoding of two-dimensional data, employing the spin-echoes created by two successive adiabatic frequency-swept chirp π pulses. The experiment is called ultrafast pulsed-field-gradient spin-echo (UF-PGSE). We present a rigorous derivation of the echo amplitude in the UF-PGSE experiment, justifying the theoretical basis of the method. The theory reveals also that the standard analysis of experimental data leads to a diffusion coefficient value overestimated by a few per cent. Although the overestimation is of the order of experimental error and thus insignificant in many practical applications, we propose that it can be compensated by a bipolar gradient version of the experiment, UF-BP-PGSE, or by corresponding stimulated-echo experiment, UF-BP-pulsed-field-gradient stimulated-echo. The latter also removes the effect of uniform background gradients. The experiments offer significant prospects for monitoring fast processes in real time as well as for increasing the sensitivity of experiments by several orders of magnitude by nuclear spin hyperpolarization. Furthermore, they can be applied as basic blocks in various ultrafast multidimensional Laplace NMR experiments. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Optimized protocols for cardiac magnetic resonance imaging in patients with thoracic metallic implants.

PubMed

Olivieri, Laura J; Cross, Russell R; O'Brien, Kendall E; Ratnayaka, Kanishka; Hansen, Michael S

2015-09-01

Cardiac magnetic resonance (MR) imaging is a valuable tool in congenital heart disease; however patients frequently have metal devices in the chest from the treatment of their disease that complicate imaging. Methods are needed to improve imaging around metal implants near the heart. Basic sequence parameter manipulations have the potential to minimize artifact while limiting effects on image resolution and quality. Our objective was to design cine and static cardiac imaging sequences to minimize metal artifact while maintaining image quality. Using systematic variation of standard imaging parameters on a fluid-filled phantom containing commonly used metal cardiac devices, we developed optimized sequences for steady-state free precession (SSFP), gradient recalled echo (GRE) cine imaging, and turbo spin-echo (TSE) black-blood imaging. We imaged 17 consecutive patients undergoing routine cardiac MR with 25 metal implants of various origins using both standard and optimized imaging protocols for a given slice position. We rated images for quality and metal artifact size by measuring metal artifact in two orthogonal planes within the image. All metal artifacts were reduced with optimized imaging. The average metal artifact reduction for the optimized SSFP cine was 1.5+/-1.8 mm, and for the optimized GRE cine the reduction was 4.6+/-4.5 mm (P < 0.05). Quality ratings favored the optimized GRE cine. Similarly, the average metal artifact reduction for the optimized TSE images was 1.6+/-1.7 mm (P < 0.05), and quality ratings favored the optimized TSE imaging. Imaging sequences tailored to minimize metal artifact are easily created by modifying basic sequence parameters, and images are superior to standard imaging sequences in both quality and artifact size. Specifically, for optimized cine imaging a GRE sequence should be used with settings that favor short echo time, i.e. flow compensation off, weak asymmetrical echo and a relatively high receiver bandwidth. For static black-blood imaging, a TSE sequence should be used with fat saturation turned off and high receiver bandwidth.

7T MRI in focal epilepsy with unrevealing conventional field strength imaging.

PubMed

De Ciantis, Alessio; Barba, Carmen; Tassi, Laura; Cosottini, Mirco; Tosetti, Michela; Costagli, Mauro; Bramerio, Manuela; Bartolini, Emanuele; Biagi, Laura; Cossu, Massimo; Pelliccia, Veronica; Symms, Mark R; Guerrini, Renzo

2016-03-01

To assess the diagnostic yield of 7T magnetic resonance imaging (MRI) in detecting and characterizing structural lesions in patients with intractable focal epilepsy and unrevealing conventional (1.5 or 3T) MRI. We conducted an observational clinical imaging study on 21 patients (17 adults and 4 children) with intractable focal epilepsy, exhibiting clinical and electroencephalographic features consistent with a single seizure-onset zone (SOZ) and unrevealing conventional MRI. Patients were enrolled at two tertiary epilepsy surgery centers and imaged at 7T, including whole brain (three-dimensional [3D] T1 -weighted [T1W] fast-spoiled gradient echo (FSPGR), 3D susceptibility-weighted angiography [SWAN], 3D fluid-attenuated inversion recovery [FLAIR]) and targeted imaging (2D T2*-weighted dual-echo gradient-recalled echo [GRE] and 2D gray-white matter tissue border enhancement [TBE] fast spin echo inversion recovery [FSE-IR]). MRI studies at 1.5 or 3T deemed unrevealing at the referral center were reviewed by three experts in epilepsy imaging. Reviewers were provided information regarding the suspected localization of the SOZ. The same team subsequently reviewed 7T images. Agreement in imaging interpretation was reached through consensus-based discussions based on visual identification of structural abnormalities and their likely correlation with clinical and electrographic data. 7T MRI revealed structural lesions in 6 (29%) of 21 patients. The diagnostic gain in detection was obtained using GRE and FLAIR images. Four of the six patients with abnormal 7T underwent epilepsy surgery. Histopathology revealed focal cortical dysplasia (FCD) in all. In the remaining 15 patients (71%), 7T MRI remained unrevealing; 4 of the patients underwent epilepsy surgery and histopathologic evaluation revealed gliosis. 7T MRI improves detection of epileptogenic FCD that is not visible at conventional field strengths. A dedicated protocol including whole brain FLAIR and GRE images at 7T targeted at the suspected SOZ increases the diagnostic yield. Wiley Periodicals, Inc. © 2016 International League Against Epilepsy.

A comparative study of metal artifacts from common metal orthodontic brackets in magnetic resonance imaging.

PubMed

Dalili Kajan, Zahra; Khademi, Jalil; Alizadeh, Ahmad; Babaei Hemmaty, Yasamin; Atrkar Roushan, Zahra

2015-09-01

This study was performed to compare the metal artifacts from common metal orthodontic brackets in magnetic resonance imaging. A dry mandible with 12 intact premolars was prepared, and was scanned ten times with various types of brackets: American, 3M, Dentaurum, and Masel orthodontic brackets were used, together with either stainless steel (SS) or nickel titanium (NiTi) wires. Subsequently, three different sequences of coronal and axial images were obtained: spin-echo T1 -weighted images, fast spin-echo T2 -weighted images, and fluid-attenuated inversion recovery images. In each sequence, the two sequential axial and coronal images with the largest signal-void area were selected. The largest diameters of the signal voids in the direction of the X-, Y-, and Z-axes were then measured twice. Finally, the mean linear values associated with different orthodontic brackets were analyzed using one-way analysis of variation, and the results were compared using the independent t-test to assess whether the use of SS or NiTi wires had a significant effect on the images. Statistically significant differences were only observed along the Z-axis among the four different brands of orthodontic brackets with SS wires. A statistically significant difference was observed along all axes among the brackets with NiTi wires. A statistically significant difference was found only along the Z-axis between nickel-free and nickel-containing brackets. With respect to all axes, the 3M bracket was associated with smaller signal-void areas. Overall, the 3M and Dentaurum brackets with NiTi wires induced smaller artifacts along all axes than those with SS wires.

A comparative study of metal artifacts from common metal orthodontic brackets in magnetic resonance imaging

PubMed Central

Khademi, Jalil; Alizadeh, Ahmad; Babaei Hemmaty, Yasamin; Atrkar Roushan, Zahra

2015-01-01

Purpose This study was performed to compare the metal artifacts from common metal orthodontic brackets in magnetic resonance imaging. Materials and Methods A dry mandible with 12 intact premolars was prepared, and was scanned ten times with various types of brackets: American, 3M, Dentaurum, and Masel orthodontic brackets were used, together with either stainless steel (SS) or nickel titanium (NiTi) wires. Subsequently, three different sequences of coronal and axial images were obtained: spin-echo T1-weighted images, fast spin-echo T2-weighted images, and fluid-attenuated inversion recovery images. In each sequence, the two sequential axial and coronal images with the largest signal-void area were selected. The largest diameters of the signal voids in the direction of the X-, Y-, and Z-axes were then measured twice. Finally, the mean linear values associated with different orthodontic brackets were analyzed using one-way analysis of variation, and the results were compared using the independent t-test to assess whether the use of SS or NiTi wires had a significant effect on the images. Results Statistically significant differences were only observed along the Z-axis among the four different brands of orthodontic brackets with SS wires. A statistically significant difference was observed along all axes among the brackets with NiTi wires. A statistically significant difference was found only along the Z-axis between nickel-free and nickel-containing brackets. Conclusion With respect to all axes, the 3M bracket was associated with smaller signal-void areas. Overall, the 3M and Dentaurum brackets with NiTi wires induced smaller artifacts along all axes than those with SS wires. PMID:26389058

MR fingerprinting using the quick echo splitting NMR imaging technique.

PubMed

Jiang, Yun; Ma, Dan; Jerecic, Renate; Duerk, Jeffrey; Seiberlich, Nicole; Gulani, Vikas; Griswold, Mark A

2017-03-01

The purpose of the study is to develop a quantitative method for the relaxation properties with a reduced radio frequency (RF) power deposition by combining magnetic resonance fingerprinting (MRF) technique with quick echo splitting NMR imaging technique (QUEST). A QUEST-based MRF sequence was implemented to acquire high-order echoes by increasing the gaps between RF pulses. Bloch simulations were used to calculate a dictionary containing the range of physically plausible signal evolutions using a range of T 1 and T 2 values based on the pulse sequence. MRF-QUEST was evaluated by comparing to the results of spin-echo methods. The specific absorption rate (SAR) of MRF-QUEST was compared with the clinically available methods. MRF-QUEST quantifies the relaxation properties with good accuracy at the estimated head SAR of 0.03 W/kg. T 1 and T 2 values estimated by MRF-QUEST are in good agreement with the traditional methods. The combination of the MRF and the QUEST provides an accurate quantification of T 1 and T 2 simultaneously with reduced RF power deposition. The resulting lower SAR may provide a new acquisition strategy for MRF when RF energy deposition is problematic. Magn Reson Med 77:979-988, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Optimal Control-Enabled Imaging and Spectroscopy using a Nanowire Magnetic Resonance Force Microscope

NASA Astrophysics Data System (ADS)

Rose, William; Haas, Holger; Chen, Angela; Cory, David; Budakian, Raffi

Magnetic resonance imaging (MRI) is a powerful non-invasive technique that has transformed our ability to study the structure and function of biological systems. Key to its success has been the unique ability to combine imaging with magnetic resonance spectroscopy. Although it remains a significant challenge, there is considerable interest in extending MRI spectroscopy to the nanometer scale because it would provide a fundamentally new route for determining the structure and function of complex biomolecules. We present data taken with a nanowire magnetic resonance force microscopy (MRFM) setup. We show how the capabilities of this very sensitive spin-detection system can be extended to include spectroscopy and nanometer-scale imaging by combining optimal control theory (OCT) techniques with magic echo sequences. We apply OCT-based dynamical-decoupling pulses to nanoscale ensembles of proton spins in polystyrene, and demonstrate a 500-fold line-narrowing of the proton spin resonance, from 30 kHz to 60 Hz. We further demonstrate 1-D imaging over a 35-nm region with an average voxel size of 2.2 nm. Funding provided by the U.S. Army Research Office, Grant No. W911NF-12-1-0341.

Coherence rephasing combined with spin-wave storage using chirped control pulses

NASA Astrophysics Data System (ADS)

Demeter, Gabor

2014-06-01

Photon-echo based optical quantum memory schemes often employ intermediate steps to transform optical coherences to spin coherences for longer storage times. We analyze a scheme that uses three identical chirped control pulses for coherence rephasing in an inhomogeneously broadened ensemble of three-level Λ systems. The pulses induce a cyclic permutation of the atomic populations in the adiabatic regime. Optical coherences created by a signal pulse are stored as spin coherences at an intermediate time interval, and are rephased for echo emission when the ensemble is returned to the initial state. Echo emission during a possible partial rephasing when the medium is inverted can be suppressed with an appropriate choice of control pulse wave vectors. We demonstrate that the scheme works in an optically dense ensemble, despite control pulse distortions during propagation. It integrates conveniently the spin-wave storage step into memory schemes based on a second rephasing of the atomic coherences.

Brachial plexus assessment with three-dimensional isotropic resolution fast spin echo MRI: comparison with conventional MRI at 3.0 T

PubMed Central

Tagliafico, A; Succio, G; Neumaier, C E; Baio, G; Serafini, G; Ghidara, M; Calabrese, M; Martinoli, C

2012-01-01

Objective The purpose of our study was to determine whether a three-dimensional (3D) isotropic resolution fast spin echo sequence (FSE-cube) has similar image quality and diagnostic performance to a routine MRI protocol for brachial plexus evaluation in volunteers and symptomatic patients at 3.0 T. Institutional review board approval and written informed consent were guaranteed. Methods In this prospective study FSE-cube was added to the standard brachial plexus examination protocol in eight patients (mean age, 50.2 years) with brachial plexus pathologies and in six volunteers (mean age, 54 years). Nerve visibility, tissue contrast, edge sharpness, image blurring, motion artefact and acquisition time were calculated for FSE-cube sequences and for the standard protocol on a standardised five-point scale. The visibility of brachial plexus nerve and surrounding tissues at four levels (roots, interscalene area, costoclavicular space and axillary level) was assessed. Results Image quality and nerve visibility did not significantly differ between FSE-cube and the standard protocol (p>0.05). Acquisition time was statistically and clinically significantly shorter with FSE-cube (p<0.05). Pathological findings were seen equally well with FSE-cube and the standard protocol. Conclusion 3D FSE-cube provided similar image quality in a shorter acquisition time and enabled excellent visualisation of brachial plexus anatomy and pathology in any orientation, regardless of the original scanning plane. PMID:21343321

Magnetic flux density measurement with balanced steady state free precession pulse sequence for MREIT: a simulation study.

PubMed

Minhas, Atul S; Woo, Eung Je; Lee, Soo Yeol

2009-01-01

Magnetic Resonance Electrical Impedance Tomography (MREIT) utilizes the magnetic flux density B(z), generated due to current injection, to find conductivity distribution inside an object. This B(z) can be measured from MR phase images using spin echo pulse sequence. The SNR of B(z) and the sensitivity of phase produced by B(z) in MR phase image are critical in deciding the resolution of MREIT conductivity images. The conventional spin echo based data acquisition has poor phase sensitivity to current injection. Longer scan time is needed to acquire data with higher SNR. We propose a balanced steady state free precession (b-SSFP) based pulse sequence which is highly sensitive to small off-resonance phase changes. A procedure to reconstruct B(z) from MR signal obtained with b-SSFP sequence is described. Phases for b-SSFP signals for two conductivity phantoms of TX 151 and Gelatin are simulated from the mathematical models of b-SSFP signal. It was observed that the phase changes obtained from b-SSFP pulse sequence are highly sensitive to current injection and hence would produce higher magnetic flux density. However, the b-SSFP signal is dependent on magnetic field inhomogeneity and the signal deteriorated highly for small offset from resonance frequency. The simulation results show that the b-SSFP sequence can be utilized for conductivity imaging of a local region where magnetic field inhomogeneity is small. A proper shimming of magnet is recommended before using the b-SSFP sequence.

Acoustic noise reduction in T 1- and proton-density-weighted turbo spin-echo imaging.

PubMed

Ott, Martin; Blaimer, Martin; Breuer, Felix; Grodzki, David; Heismann, Björn; Jakob, Peter

2016-02-01

To reduce acoustic noise levels in T 1-weighted and proton-density-weighted turbo spin-echo (TSE) sequences, which typically reach acoustic noise levels up to 100 dB(A) in clinical practice. Five acoustic noise reduction strategies were combined: (1) gradient ramps and shapes were changed from trapezoidal to triangular, (2) variable-encoding-time imaging was implemented to relax the phase-encoding gradient timing, (3) RF pulses were adapted to avoid the need for reversing the polarity of the slice-rewinding gradient, (4) readout bandwidth was increased to provide more time for gradient activity on other axes, (5) the number of slices per TR was reduced to limit the total gradient activity per unit time. We evaluated the influence of each measure on the acoustic noise level, and conducted in vivo measurements on a healthy volunteer. Sound recordings were taken for comparison. An overall acoustic noise reduction of up to 16.8 dB(A) was obtained by the proposed strategies (1-4) and the acquisition of half the number of slices per TR only. Image quality in terms of SNR and CNR was found to be preserved. The proposed measures in this study allowed a threefold reduction in the acoustic perception of T 1-weighted and proton-density-weighted TSE sequences compared to a standard TSE-acquisition. This could be achieved without visible degradation of image quality, showing the potential to improve patient comfort and scan acceptability.

Amide proton transfer imaging of brain tumors using a self-corrected 3D fast spin-echo dixon method: Comparison With separate B0 correction.

PubMed

Togao, Osamu; Keupp, Jochen; Hiwatashi, Akio; Yamashita, Koji; Kikuchi, Kazufumi; Yoneyama, Masami; Honda, Hiroshi

2017-06-01

To assess the quantitative performance of three-dimensional (3D) fast spin-echo (FSE) Dixon amide proton transfer (APT) imaging of brain tumors compared with B 0 correction with separate mapping methods. Twenty-two patients with brain tumors (54.2 ± 18.7 years old, 12 males and 10 females) were scanned at 3 Tesla (T). Z-spectra were obtained at seven different frequency offsets at ±3.1 ppm, ± 3.5 ppm, ± 3.9 ppm, and -1560 ppm. The scan was repeated three times at +3.5 ppm with echo shifts for Dixon B 0 mapping. The APT image corrected by a three-point Dixon-type B 0 map from the same scan (3D-Dixon) or a separate B 0 map (2D-separate and 3D-separate), and an uncorrected APT image (3D-uncorrected) were generated. We compared the APT-weighted signals within a tumor obtained with each 3D method with those obtained with 2D-separate as a reference standard. Excellent agreements and correlations with the 2D-separate were obtained by the 3D-Dixon method for both mean (ICC = 0.964, r = 0.93, P < 0.0001) and 90th-percentile (ICC = 0.972, r = 0.95, P < 0.0001) APT-weighted signals. These agreements and correlations for 3D-Dixon were better than those obtained by the 3D-uncorrected and 3D-separate methods. The 3D FSE Dixon APT method with intrinsic B 0 correction offers a quantitative performance that is similar to that of established two-dimensional (2D) methods. Magn Reson Med 77:2272-2279, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Multiple Echo Diffusion Tensor Acquisition Technique (MEDITATE) on a 3T clinical scanner

PubMed Central

Baete, Steven H.; Cho, Gene; Sigmund, Eric E.

2013-01-01

This paper describes the concepts and implementation of an MRI method, Multiple Echo Diffusion Tensor Acquisition Technique (MEDITATE), which is capable of acquiring apparent diffusion tensor maps in two scans on a 3T clinical scanner. In each MEDITATE scan, a set of RF-pulses generates multiple echoes whose amplitudes are diffusion-weighted in both magnitude and direction by a pattern of diffusion gradients. As a result, two scans acquired with different diffusion weighting strengths suffice for accurate estimation of diffusion tensor imaging (DTI)-parameters. The MEDITATE variation presented here expands previous MEDITATE approaches to adapt to the clinical scanner platform, such as exploiting longitudinal magnetization storage to reduce T2-weighting. Fully segmented multi-shot Cartesian encoding is used for image encoding. MEDITATE was tested on isotropic (agar gel), anisotropic diffusion phantoms (asparagus), and in vivo skeletal muscle in healthy volunteers with cardiac-gating. Comparisons of accuracy were performed with standard twice-refocused spin echo (TRSE) DTI in each case and good quantitative agreement was found between diffusion eigenvalues, mean diffusivity, and fractional anisotropy derived from TRSE-DTI and from the MEDITATE sequence. Orientation patterns were correctly reproduced in both isotropic and anisotropic phantoms, and approximately so for in vivo imaging. This illustrates that the MEDITATE method of compressed diffusion encoding is feasible on the clinical scanner platform. With future development and employment of appropriate view-sharing image encoding this technique may be used in clinical applications requiring time-sensitive acquisition of DTI parameters such as dynamical DTI in muscle. PMID:23828606

Full analytical solution of the bloch equation when using a hyperbolic-secant driving function.

PubMed

Zhang, Jinjin; Garwood, Michael; Park, Jang-Yeon

2017-04-01

The frequency-swept pulse known as the hyperbolic-secant (HS) pulse is popular in NMR for achieving adiabatic spin inversion. The HS pulse has also shown utility for achieving excitation and refocusing in gradient-echo and spin-echo sequences, including new ultrashort echo-time imaging (e.g., Sweep Imaging with Fourier Transform, SWIFT) and B 1 mapping techniques. To facilitate the analysis of these techniques, the complete theoretical solution of the Bloch equation, as driven by the HS pulse, was derived for an arbitrary state of initial magnetization. The solution of the Bloch-Riccati equation for transverse and longitudinal magnetization for an arbitrary initial state was derived analytically in terms of HS pulse parameters. The analytical solution was compared with the solutions using both the Runge-Kutta method and the small-tip approximation. The analytical solution was demonstrated on different initial states at different frequency offsets with/without a combination of HS pulses. Evolution of the transverse magnetization was influenced significantly by the choice of HS pulse parameters. The deviation of the magnitude of the transverse magnetization, as obtained by comparing the small-tip approximation to the analytical solution, was < 5% for flip angles < 30 °, but > 10% for the flip angles > 40 °. The derived analytical solution provides insights into the influence of HS pulse parameters on the magnetization evolution. Magn Reson Med 77:1630-1638, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Signal-to-noise ratio, T2 , and T2* for hyperpolarized helium-3 MRI of the human lung at three magnetic field strengths.

PubMed

Komlosi, Peter; Altes, Talissa A; Qing, Kun; Mooney, Karen E; Miller, G Wilson; Mata, Jaime F; de Lange, Eduard E; Tobias, William A; Cates, Gordon D; Mugler, John P

2017-10-01

To evaluate T 2 , T2*, and signal-to-noise ratio (SNR) for hyperpolarized helium-3 ( 3 He) MRI of the human lung at three magnetic field strengths ranging from 0.43T to 1.5T. Sixteen healthy volunteers were imaged using a commercial whole body scanner at 0.43T, 0.79T, and 1.5T. Whole-lung T 2 values were calculated from a Carr-Purcell-Meiboom-Gill spin-echo-train acquisition. T2* maps and SNR were determined from dual-echo and single-echo gradient-echo images, respectively. Mean whole-lung SNR values were normalized by ventilated lung volume and administered 3 He dose. As expected, T 2 and T2* values demonstrated a significant inverse relationship to field strength. Hyperpolarized 3 He images acquired at all three field strengths had comparable SNR values and thus appeared visually very similar. Nonetheless, the relatively small SNR differences among field strengths were statistically significant. Hyperpolarized 3 He images of the human lung with similar image quality were obtained at three field strengths ranging from 0.43T and 1.5T. The decrease in susceptibility effects at lower fields that are reflected in longer T 2 and T2* values may be advantageous for optimizing pulse sequences inherently sensitive to such effects. The three-fold increase in T2* at lower field strength would allow lower receiver bandwidths, providing a concomitant decrease in noise and relative increase in SNR. Magn Reson Med 78:1458-1463, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Acute interstitial edematous pancreatitis: Findings on non-enhanced MR imaging

PubMed Central

Zhang, Xiao-Ming; Feng, Zhi-Song; Zhao, Qiong-Hui; Xiao, Chun-Ming; Mitchell, Donald G; Shu, Jian; Zeng, Nan-Lin; Xu, Xiao-Xue; Lei, Jun-Yang; Tian, Xiao-Bing

2006-01-01

AIM: To study the appearances of acute interstitial edematous pancreatitis (IEP) on non-enhanced MR imaging. METHODS: A total of 53 patients with IEP diagnosed by clinical features and laboratory findings were underwent MR imaging. MR imaging sequences included fast spoiled gradient echo (FSPGR) fat saturation axial T1-weighted imaging, gradient echo T1-weighted (in phase), single shot fast spin echo (SSFSE) T2-weighted, respiratory triggered (R-T) T2-weighted with fat saturation, and MR cholangiopancreatography. Using the MR severity score index, pancreatitis was graded as mild (0-2 points), moderate (3-6 points) and severe (7-10 points). RESULTS: Among the 53 patients, IEP was graded as mild in 37 patients and as moderate in 16 patients. Forty-seven of 53 (89%) patients had at least one abnormality on MR images. Pancreas was hypointense relative to liver on FSPGR T1-weighted images in 18.9% of patients, and hyperintense in 25% and 30% on SSFSE T2-weighted and R-T T2-weighted images, respectively. The prevalences of the findings of IEP on R-T T2-weighted images were, respectively, 85% for pancreatic fascial plane, 77% for left renal fascial plane, 55% for peripancreatic fat stranding, 42% for right renal fascial plane, 45% for perivascular fluid, 40% for thickened pancreatic lobular septum and 25% for peripancreatic fluid, which were markedly higher than those on in-phase or SSFSE T2-weighted images (P < 0.001). CONCLUSION: IEP primarily manifests on non-enhanced MR images as thickened pancreatic fascial plane, left renal fascial plane, peripancreatic fat stranding, and peripancreatic fluid. R-T T2-weighted imaging is more sensitive than in-phase and SSFSE T2-weighted imaging for depicting IEP. PMID:17007053

Acute interstitial edematous pancreatitis: Findings on non-enhanced MR imaging.

PubMed

Zhang, Xiao-Ming; Feng, Zhi-Song; Zhao, Qiong-Hui; Xiao, Chun-Ming; Mitchell, Donald-G; Shu, Jian; Zeng, Nan-Lin; Xu, Xiao-Xue; Lei, Jun-Yang; Tian, Xiao-Bing

2006-09-28

To study the appearances of acute interstitial edematous pancreatitis (IEP) on non-enhanced MR imaging. A total of 53 patients with IEP diagnosed by clinical features and laboratory findings were underwent MR imaging. MR imaging sequences included fast spoiled gradient echo (FSPGR) fat saturation axial T1-weighted imaging, gradient echo T1-weighted (in phase), single shot fast spin echo (SSFSE) T2-weighted, respiratory triggered (R-T) T2-weighted with fat saturation, and MR cholangiopancreatography. Using the MR severity score index, pancreatitis was graded as mild (0-2 points), moderate (3-6 points) and severe (7-10 points). Among the 53 patients, IEP was graded as mild in 37 patients and as moderate in 16 patients. Forty-seven of 53 (89%) patients had at least one abnormality on MR images. Pancreas was hypointense relative to liver on FSPGR T1-weighted images in 18.9% of patients, and hyperintense in 25% and 30% on SSFSE T2-weighted and R-T T2-weighted images, respectively. The prevalences of the findings of IEP on R-T T2-weighted images were, respectively, 85% for pancreatic fascial plane, 77% for left renal fascial plane, 55% for peripancreatic fat stranding, 42% for right renal fascial plane, 45% for perivascular fluid, 40% for thickened pancreatic lobular septum and 25% for peripancreatic fluid, which were markedly higher than those on in-phase or SSFSE T2-weighted images (P<0.001). IEP primarily manifests on non-enhanced MR images as thickened pancreatic fascial plane, left renal fascial plane, peripancreatic fat stranding, and peripancreatic fluid. R-T T2-weighted imaging is more sensitive than in-phase and SSFSE T2-weighted imaging for depicting IEP.

A study of the comparative anatomy of the brain of domestic ruminants using magnetic resonance imaging.

PubMed

Schmidt, M J; Langen, N; Klumpp, S; Nasirimanesh, F; Shirvanchi, P; Ondreka, N; Kramer, M

2012-01-01

Although magnetic resonance imaging has been used to examine the brain of domestic ruminants, detailed information relating the precise anatomical features in these species is lacking. In this study the brain structures of calves (Bos taurus domesticus), sheep (Ovis aries), goats (Capra hircus) and a mesaticephalic dog (Canis lupis familiaris) were examined using T2-weighed Turbo Spin Echo sequences; three-dimensional models based on high-resolution gradient echo scans were used to identify brain sulci and gyri in two-dimensional images. The ruminant brains examined were similar in structure and organisation to those of other mammals but particular features included the deep depression of the insula and the pronounced gyri of the cortices, the dominant position of the visual (optic nerve, optic chiasm and rostral colliculus) and olfactory (olfactory bulb, olfactory tracts and piriform lobe) systems, and the relatively large size of the diencephalon. Copyright © 2010 Elsevier Ltd. All rights reserved.

Isotropic resolution diffusion tensor imaging of lumbosacral and sciatic nerves using a phase‐corrected diffusion‐prepared 3D turbo spin echo

PubMed Central

Van, Anh T.; Weidlich, Dominik; Kooijman, Hendrick; Hock, Andreas; Rummeny, Ernst J.; Gersing, Alexandra; Kirschke, Jan S.; Karampinos, Dimitrios C.

2018-01-01

Purpose To perform in vivo isotropic‐resolution diffusion tensor imaging (DTI) of lumbosacral and sciatic nerves with a phase‐navigated diffusion‐prepared (DP) 3D turbo spin echo (TSE) acquisition and modified reconstruction incorporating intershot phase‐error correction and to investigate the improvement on image quality and diffusion quantification with the proposed phase correction. Methods Phase‐navigated DP 3D TSE included magnitude stabilizers to minimize motion and eddy‐current effects on the signal magnitude. Phase navigation of motion‐induced phase errors was introduced before readout in 3D TSE. DTI of lower back nerves was performed in vivo using 3D TSE and single‐shot echo planar imaging (ss‐EPI) in 13 subjects. Diffusion data were phase‐corrected per k z plane with respect to T2‐weighted data. The effects of motion‐induced phase errors on DTI quantification was assessed for 3D TSE and compared with ss‐EPI. Results Non–phase‐corrected 3D TSE resulted in artifacts in diffusion‐weighted images and overestimated DTI parameters in the sciatic nerve (mean diffusivity [MD] = 2.06 ± 0.45). Phase correction of 3D TSE DTI data resulted in reductions in all DTI parameters (MD = 1.73 ± 0.26) of statistical significance (P ≤ 0.001) and in closer agreement with ss‐EPI DTI parameters (MD = 1.62 ± 0.21). Conclusion DP 3D TSE with phase correction allows distortion‐free isotropic diffusion imaging of lower back nerves with robustness to motion‐induced artifacts and DTI quantification errors. Magn Reson Med 80:609–618, 2018. © 2018 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. PMID:29380414

Comparison of Silent and Conventional MR Imaging for the Evaluation of Myelination in Children

PubMed Central

Matsuo-Hagiyama, Chisato; Watanabe, Yoshiyuki; Tanaka, Hisashi; Takahashi, Hiroto; Arisawa, Atsuko; Yoshioka, Eri; Nabatame, Shin; Nakano, Sayaka; Tomiyama, Noriyuki

2017-01-01

Purpose: Silent magnetic resonance imaging (MRI) scans produce reduced acoustic noise and are considered more gentle for sedated children. The aim of this study was to compare the validity of T1- (T1W) and T2-weighted (T2W) silent sequences for myelination assessment in children with conventional spin-echo sequences. Materials and Methods: A total of 30 children (21 boys, 9 girls; age range: 1–83 months, mean age: 35.5 months, median age: 28.5 months) were examined using both silent and spin-echo sequences. Acoustic noise levels were analyzed and compared. The degree of myelination was qualitatively assessed via consensus, and T1W and T2W signal intensities were quantitatively measured by percent contrast. Results: Acoustic noise levels were significantly lower during silent sequences than during conventional sequences (P < 0.0001 for both T1W and T2W). Inter-method comparison indicated overall good to excellent agreement (T1W and T2W images, κ = 0.76 and 0.80, respectively); however, agreement was poor for cerebellar myelination on T1W images (κ = 0.14). The percent contrast of silent and conventional MRI sequences had a strong correlation (T1W, correlation coefficient [CC] = 0.76; T1W excluding the middle cerebellar peduncle, CC = 0.82; T2W, CC = 0.91). Conclusions: For brain MRI, silent sequences significantly reduced acoustic noise and provided diagnostic image quality for myelination evaluations; however, the two methods differed with respect to cerebellar delineation on T1W sequences. PMID:27795484

Clinical application of Half Fourier Acquisition Single Shot Turbo Spin Echo (HASTE) imaging accelerated by simultaneous multi-slice acquisition.

PubMed

Schulz, Jenni; P Marques, José; Ter Telgte, Annemieke; van Dorst, Anouk; de Leeuw, Frank-Erik; Meijer, Frederick J A; Norris, David G

2018-01-01

As a single-shot sequence with a long train of refocusing pulses, Half-Fourier Acquisition Single-Shot Turbo-Spin-Echo (HASTE) suffers from high power deposition limiting use at high resolutions and high field strengths, particularly if combined with acceleration techniques such as simultaneous multi-slice (SMS) imaging. Using a combination of multiband (MB)-excitation and PINS-refocusing pulses will effectively accelerate the acquisition time while staying within the SAR limitations. In particular, uncooperative and young patients will profit from the speed of the MB-PINS HASTE sequence, as clinical diagnosis can be possible without sedation. Materials and MethodsMB-excitation and PINS-refocusing pulses were incorporated into a HASTE-sequence with blipped CAIPIRINHA and TRAPS including an internal FLASH reference scan for online reconstruction. Whole brain MB-PINS HASTE data were acquired on a Siemens 3T-Prisma system from 10 individuals and compared to a clinical HASTE protocol. ResultsThe proposed MB-PINS HASTE protocol accelerates the acquisition by about a factor 2 compared to the clinical HASTE. The diagnostic image quality proved to be comparable for both sequences for the evaluation of the overall aspect of the brain, the detection of white matter changes and areas of tissue loss, and for the evaluation of the CSF spaces although artifacts were more frequently encountered with MB-PINS HASTE. ConclusionsMB-PINS HASTE enables acquisition of slice accelerated highly T2-weighted images and provides good diagnostic image quality while reducing acquisition time. Copyright © 2017 Elsevier B.V. All rights reserved.

Comparing an accelerated 3D fast spin-echo sequence (CS-SPACE) for knee 3-T magnetic resonance imaging with traditional 3D fast spin-echo (SPACE) and routine 2D sequences.

PubMed

Altahawi, Faysal F; Blount, Kevin J; Morley, Nicholas P; Raithel, Esther; Omar, Imran M

2017-01-01

To compare a faster, new, high-resolution accelerated 3D-fast-spin-echo (3D-FSE) acquisition sequence (CS-SPACE) to traditional 2D and high-resolution 3D sequences for knee 3-T magnetic resonance imaging (MRI). Twenty patients received knee MRIs that included routine 2D (T1, PD ± FS, T2-FS; 0.5 × 0.5 × 3 mm 3 ; ∼10 min), traditional 3D FSE (SPACE-PD-FS; 0.5 × 0.5 × 0.5 mm 3 ; ∼7.5 min), and accelerated 3D-FSE prototype (CS-SPACE-PD-FS; 0.5 × 0.5 × 0.5 mm 3 ; ∼5 min) acquisitions on a 3-T MRI system (Siemens MAGNETOM Skyra). Three musculoskeletal radiologists (MSKRs) prospectively and independently reviewed the studies with graded surveys comparing image and diagnostic quality. Tissue-specific signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were also compared. MSKR-perceived diagnostic quality of cartilage was significantly higher for CS-SPACE than for SPACE and 2D sequences (p < 0.001). Assessment of diagnostic quality of menisci and synovial fluid was higher for CS-SPACE than for SPACE (p < 0.001). CS-SPACE was not significantly different from SPACE but had lower assessments than 2D sequences for evaluation of bones, ligaments, muscles, and fat (p ≤ 0.004). 3D sequences had higher spatial resolution, but lower overall assessed contrast (p < 0.001). Overall image quality from CS-SPACE was assessed as higher than SPACE (p = 0.007), but lower than 2D sequences (p < 0.001). Compared to SPACE, CS-SPACE had higher fluid SNR and CNR against all other tissues (all p < 0.001). The CS-SPACE prototype allows for faster isotropic acquisitions of knee MRIs over currently used protocols. High fluid-to-cartilage CNR and higher spatial resolution over routine 2D sequences may present a valuable role for CS-SPACE in the evaluation of cartilage and menisci.

Renal damages after extracorporeal shock wave lithotripsy evaluated by Gd-DTPA-enhanced dynamic magnetic resonance imaging.

PubMed

Umekawa, T; Kohri, K; Yamate, T; Amasaki, N; Ishikawa, Y; Takada, M; Iguchi, M; Kurita, T

1992-01-01

Renal damages after extracorporeal shock wave lithotripsy (ESWL) were evaluated by magnetic resonance imaging (MRI) including Gd-DTPA-enhanced dynamic MRI in 37 patients with renal stone by spin echo methods (T1 and T2-weighted scan) and small tip angle gradient echo method (T2-weighted scan). Sixty-eight percent of the patients had changes in the MRI findings after ESWL. The frequently observed findings were perirenal fluid collection (38%), loss of corticomedullary junction (35%), and increased signal intensity of muscle and other adjacent tissue (34%). Preoperative Gd-DTPA-enhanced dynamic MRI showed low intensity band which suggests Gd-DTPA secretion from the glomerulus into the renal tubulus. In all cases the low intensity band became unclear after ESWL because of renal contusion due to ESWL. MRI, including Gd-DTPA-enhanced dynamic MRI, is considered to be a good procedure for evaluation of renal damages due to ESWL.

Quantum measurement and orientation tracking of fluorescent nanodiamonds inside living cells

NASA Astrophysics Data System (ADS)

McGuinness, L. P.; Yan, Y.; Stacey, A.; Simpson, D. A.; Hall, L. T.; MacLaurin, D.; Prawer, S.; Mulvaney, P.; Wrachtrup, J.; Caruso, F.; Scholten, R. E.; Hollenberg, L. C. L.

2011-06-01

Fluorescent particles are routinely used to probe biological processes. The quantum properties of single spins within fluorescent particles have been explored in the field of nanoscale magnetometry, but not yet in biological environments. Here, we demonstrate optically detected magnetic resonance of individual fluorescent nanodiamond nitrogen-vacancy centres inside living human HeLa cells, and measure their location, orientation, spin levels and spin coherence times with nanoscale precision. Quantum coherence was measured through Rabi and spin-echo sequences over long (>10 h) periods, and orientation was tracked with effective 1° angular precision over acquisition times of 89 ms. The quantum spin levels served as fingerprints, allowing individual centres with identical fluorescence to be identified and tracked simultaneously. Furthermore, monitoring decoherence rates in response to changes in the local environment may provide new information about intracellular processes. The experiments reported here demonstrate the viability of controlled single spin probes for nanomagnetometry in biological systems, opening up a host of new possibilities for quantum-based imaging in the life sciences.

Magnetic resonance imaging and relaxometry to study water transport mechanisms in a commercially available gastrointestinal therapeutic system (GITS) tablet.

PubMed

Broadbent, Amber L; Fell, Rob J; Codd, Sarah L; Lightley, Kim A; Konagurthu, Sanjay; Koehler-King, Dory G; Seymour, Joseph D

2010-09-15

The hydration of 4 mg Cardura XL (Pfizer), a commercially available gastrointestinal therapeutic system (GITS) tablet, was investigated using magnetic resonance imaging (MRI). A short echo time (T(e)=2.81 ms) technique for MRI of the hydration of a GITS tablet was implemented. From the MR images, signal intensity profiles were generated and interpreted in the context of diffusive and osmotic transport mechanisms. A distinct transition from diffusive to osmotic transport was measured at a timescale relevant to the measured drug release time. Diffusion and osmotic rate coefficients for water in the drug and polymer sweller layers of the tablet were quantified. Spin-lattice T(1) and spin-spin T(2) relaxation times of the water signal from within the tablet were measured as a function of hydration time in order to incorporate the effects of relaxation into interpretation of signal intensity and provide unique information on the distribution of water in different physical and chemical environments within the tablet. Copyright 2010 Elsevier B.V. All rights reserved.

Comparison of DWI Methods in the Pediatric Brain: PROPELLER Turbo Spin-Echo Imaging Versus Readout-Segmented Echo-Planar Imaging Versus Single-Shot Echo-Planar Imaging.

PubMed

Kim, Tae-Hyung; Baek, Moon-Young; Park, Ji Eun; Ryu, Young Jin; Cheon, Jung-Eun; Kim, In-One; Choi, Young Hun

2018-06-01

The purpose of this study is to compare DWI for pediatric brain evaluation using single-shot echo-planar imaging (EPI), periodically rotated overlapping parallel lines with enhanced reconstruction (Blade), and readout-segmented EPI (Resolve). Blade, Resolve, and single-shot EPI were performed for 27 pediatric patients (median age, 9 years), and three datasets were independently reviewed by two radiologists. Qualitative analyses were performed for perceptive coarseness, image distortion, susceptibility-related changes, motion artifacts, and lesion conspicuity using a 5-point Likert scale. Quantitative analyses were conducted for spatial distortion and signal uniformity of each sequence. Mean scores were 2.13, 3.17, and 3.76 for perceptive coarseness; 4.85, 3.96, and 2.19 for image distortion; 4.76, 3.96, and 2.30 for susceptibility-related change; 4.96, 3.83, and 4.69 for motion artifacts; and 2.71, 3.75, and 1.92 for lesion conspicuity, for Blade, Resolve, and single-shot EPI, respectively. Blade and Resolve showed better quality than did single-shot EPI for image distortion, susceptibility-related changes, and lesion conspicuity. Blade showed less image distortion, fewer susceptibility-related changes, and fewer motion artifacts than did Resolve, whereas lesion conspicuity was better with Resolve. Blade showed increased signal variation compared with Resolve and single-shot EPI (coefficients of variation were 0.10, 0.08, and 0.05 for lateral ventricle; 0.13, 0.09, and 0.05 for centrum semiovale; and 0.16, 0.09, and 0.06 for pons in Blade, Resolve, and single-shot EPI, respectively). DWI with Resolve or Blade yields better quality regarding distortion, susceptibility-related changes, and lesion conspicuity, compared with single-shot EPI. Blade is less susceptible to motion artifacts than is Resolve, whereas Resolve yields less noise and better lesion conspicuity than does Blade.

Imaging for understanding speech communication: Advances and challenges

NASA Astrophysics Data System (ADS)

Narayanan, Shrikanth

2005-04-01

Research in speech communication has relied on a variety of instrumentation methods to illuminate details of speech production and perception. One longstanding challenge has been the ability to examine real-time changes in the shaping of the vocal tract; a goal that has been furthered by imaging techniques such as ultrasound, movement tracking, and magnetic resonance imaging. The spatial and temporal resolution afforded by these techniques, however, has limited the scope of the investigations that could be carried out. In this talk, we focus on some recent advances in magnetic resonance imaging that allow us to perform near real-time investigations on the dynamics of vocal tract shaping during speech. Examples include Demolin et al. (2000) (4-5 images/second, ultra-fast turbo spin echo) and Mady et al. (2001,2002) (8 images/second, T1 fast gradient echo). A recent study by Narayanan et al. (2004) that used a spiral readout scheme to accelerate image acquisition has allowed for image reconstruction rates of 24 images/second. While these developments offer exciting prospects, a number of challenges lie ahead, including: (1) improving image acquisition protocols, hardware for enhancing signal-to-noise ratio, and optimizing spatial sampling; (2) acquiring quality synchronized audio; and (3) analyzing and modeling image data including cross-modality registration. [Work supported by NIH and NSF.

[The Role of Imaging in Central Nervous System Infections].

PubMed

Yokota, Hajime; Tazoe, Jun; Yamada, Kei

2015-07-01

Many infections invade the central nervous system. Magnetic resonance imaging (MRI) is the main tool that is used to evaluate infectious lesions of the central nervous system. The useful sequences on MRI are dependent on the locations, such as intra-axial, extra-axial, and spinal cord. For intra-axial lesions, besides the fundamental sequences, including T1-weighted images, T2-weighted images, and fluid-attenuated inversion recovery (FLAIR) images, advanced sequences, such as diffusion-weighted imaging, diffusion tensor imaging, susceptibility-weighted imaging, and MR spectroscopy, can be applied. They are occasionally used as determinants for quick and correct diagnosis. For extra-axial lesions, understanding the differences among 2D-conventional T1-weighted images, 2D-fat-saturated T1-weighted images, 3D-Spin echo sequences, and 3D-Gradient echo sequence after the administration of gadolinium is required to avoid wrong interpretations. FLAIR plus gadolinium is a useful tool for revealing abnormal enhancement on the brain surface. For the spinal cord, the sequences are limited. Evaluating the distribution and time course of the spinal cord are essential for correct diagnoses. We summarize the role of imaging in central nervous system infections and show the pitfalls, key points, and latest information in them on clinical practices.

Diffusion tensor imaging in children with tuberous sclerosis complex: tract-based spatial statistics assessment of brain microstructural changes.

PubMed

Zikou, Anastasia K; Xydis, Vasileios G; Astrakas, Loukas G; Nakou, Iliada; Tzarouchi, Loukia C; Tzoufi, Meropi; Argyropoulou, Maria I

2016-07-01

There is evidence of microstructural changes in normal-appearing white matter of patients with tuberous sclerosis complex. To evaluate major white matter tracts in children with tuberous sclerosis complex using tract-based spatial statistics diffusion tensor imaging (DTI) analysis. Eight children (mean age ± standard deviation: 8.5 ± 5.5 years) with an established diagnosis of tuberous sclerosis complex and 8 age-matched controls were studied. The imaging protocol consisted of T1-weighted high-resolution 3-D spoiled gradient-echo sequence and a spin-echo, echo-planar diffusion-weighted sequence. Differences in the diffusion indices were evaluated using tract-based spatial statistics. Tract-based spatial statistics showed increased axial diffusivity in the children with tuberous sclerosis complex in the superior and anterior corona radiata, the superior longitudinal fascicle, the inferior fronto-occipital fascicle, the uncinate fascicle and the anterior thalamic radiation. No significant differences were observed in fractional anisotropy, mean diffusivity and radial diffusivity between patients and control subjects. No difference was found in the diffusion indices between the baseline and follow-up examination in the patient group. Patients with tuberous sclerosis complex have increased axial diffusivity in major white matter tracts, probably related to reduced axonal integrity.

Magnetic Resonance Imaging Assessment of Intra-Articular Structures in the Canine Stifle Joint after Implantation of a Titanium Tibial Plateau Levelling Osteotomy Plate.

PubMed

Feichtenschlager, Christian; Gerwing, Martin; Failing, Klaus; Peppler, Christine; Kása, Andreas; Kramer, Martin; von Pückler, Kerstin H

2018-06-02

 To determine the effectiveness of magnetic resonance imaging (MRI) in the evaluation of anatomical stifle structures with respect to implant positioning after tibial plateau levelling osteotomy (TPLO) using a titanium plate.  Selected sagittal and dorsal sequences of pre- and postoperative MRI (1.0 T scanner) of 13 paired ( n  = 26) sound cadaveric stifle joints were evaluated. The effect of susceptibility artifact on adjacent anatomical stifle structures was graded from 0 to 5. The impact of implant positioning regarding assessment score was calculated using Spearman's rank correlation coefficient.  Sagittal turbo spin echo (TSE)-acquired images enabled interpretation of most soft tissue, osseous and cartilage structures without detrimental effect of susceptibility artifact distortions. In T2-weighted TSE images, the cranial cruciate ligament and caudal horn of the medial meniscus could be evaluated, independent of implant position, without any susceptibility artifact in all specimens. T2-weighted fast field echo, water selective, balanced fast field echo and short tau inversion recovery were most markedly affected by susceptibility artifact.  In selected TSE sequences, MRI allows evaluation of critical intra-articular structures after titanium TPLO plate implantation. Further investigations with confirmed stifle pathologies in dogs are required, to evaluate the accuracy of MRI after TPLO in clinical cases in this context. Schattauer GmbH Stuttgart.

MTR and In-vivo 1H-MRS studies on mouse brain with parkinson's disease

NASA Astrophysics Data System (ADS)

Yoon, Moon-Hyun; Kim, Hyeon-Jin; Chung, Jin-Yeung; Doo, Ah-Reum; Park, Hi-Joon; Kim, Seung-Nam; Choe, Bo-Young

2012-12-01

The aim of this study was to investigate whether the changes in the magnetization transfer ratio (MTR) histogram are related to specific characteristics of Parkinson's disease (PD) and to investigate whether the MTR histogram parameters are associated with neurochemical dysfunction by performing in vivo proton magnetic resonance spectroscopy (1H-MRS). MTR and in vivo 1H-MRS studies were performed on control mice (n = 10) and 1-methyl-1,2,3,6-tetrahydropyridine intoxicated mice (n = 10). All the MTR and in vivo 1H-MRS experiments were performed on a 9.4 T MRI/MRS system (Bruker Biospin, Germany) using a standard head coil. The protondensity fast spin echo (FSE) images and the T2-weighted spin echo (SE) images were acquired with no gap. Outer volume suppression (OVS), combined with the ultra-short echo-time stimulated echo acquisition mode (STEAM), was used for the localized in-vivo 1H-MRS. The quantitative analysis of metabolites was performed from the 1H spectra obtained in vivo on the striatum (ST) by using jMRUI (Lyon, France). The peak height of the MTR histograms in the PD model group was significantly lower than that in the control group (p < 0.05). The midbrain MTR values for volume were lower in the PD group than the control group(p < 0.05). The complex peak (Glx: glutamine+glutamate+ GABA)/creatine (Cr) ratio of the right ST in the PD group was significantly increased as compared to that of the control group. The present study revealed that the peak height of the MTR histogram was significantly decreased in the ST and substantia nigra, and a significant increase in the Gl x /Cr ratio was found in the ST of the PD group, as compared with that of the control group. These findings could reflect the early phase of neuronal dysfunction of neurotransmitters.

Simultaneous Measurement of T2 and Apparent Diffusion Coefficient (T2+ADC) in the Heart With Motion-Compensated Spin Echo Diffusion-Weighted Imaging

PubMed Central

Aliotta, Eric; Moulin, Kévin; Zhang, Zhaohuan; Ennis, Daniel B.

2018-01-01

Purpose To evaluate a technique for simultaneous quantitative T2 and apparent diffusion coefficient (ADC) mapping in the heart (T2+ADC) using spin echo (SE) diffusion-weighted imaging (DWI). Theory and Methods T2 maps from T2+ADC were compared with single-echo SE in phantoms and with T2-prepared (T2-prep) balanced steady-state free precession (bSSFP) in healthy volunteers. ADC maps from T2+ADC were compared with conventional DWI in phantoms and in vivo. T2+ADC was also demonstrated in a patient with acute myocardial infarction (MI). Results Phantom T2 values from T2+ADC were closer to a single-echo SE reference than T2-prep bSSFP (−2.3 ± 6.0% vs 22.2 ± 16.3%; P < 0.01), and ADC values were in excellent agreement with DWI (0.28 ± 0.4%). In volunteers, myocardial T2 values from T2+ADC were significantly shorter than T2-prep bSSFP (35.8 ± 3.1 vs 46.8 ± 3.8 ms; P < 0.01); myocardial ADC was not significantly (N.S.) different between T2+ADC and conventional motion-compensated DWI (1.39 ± 0.18 vs 1.38 ± 0.18 mm2/ms; P = N.S.). In the patient, T2 and ADC were both significantly elevated in the infarct compared with remote myocardium (T2: 40.4 ± 7.6 vs 56.8 ± 22.0; P < 0.01; ADC: 1.47 ± 0.59 vs 1.65 ± 0.65 mm2/ms; P < 0.01). Conclusion T2+ADC generated coregistered, free-breathing T2 and ADC maps in healthy volunteers and a patient with acute MI with no cost in accuracy, precision, or scan time compared with DWI. PMID:28516485

BOLD temporal dynamics of rat superior colliculus and lateral geniculate nucleus following short duration visual stimulation.

PubMed

Lau, Condon; Zhou, Iris Y; Cheung, Matthew M; Chan, Kevin C; Wu, Ed X

2011-04-29

The superior colliculus (SC) and lateral geniculate nucleus (LGN) are important subcortical structures for vision. Much of our understanding of vision was obtained using invasive and small field of view (FOV) techniques. In this study, we use non-invasive, large FOV blood oxygenation level-dependent (BOLD) fMRI to measure the SC and LGN's response temporal dynamics following short duration (1 s) visual stimulation. Experiments are performed at 7 tesla on Sprague Dawley rats stimulated in one eye with flashing light. Gradient-echo and spin-echo sequences are used to provide complementary information. An anatomical image is acquired from one rat after injection of monocrystalline iron oxide nanoparticles (MION), a blood vessel contrast agent. BOLD responses are concentrated in the contralateral SC and LGN. The SC BOLD signal measured with gradient-echo rises to 50% of maximum amplitude (PEAK) 0.2±0.2 s before the LGN signal (p<0.05). The LGN signal returns to 50% of PEAK 1.4±1.2 s before the SC signal (p<0.05). These results indicate the SC signal rises faster than the LGN signal but settles slower. Spin-echo results support these findings. The post-MION image shows the SC and LGN lie beneath large blood vessels. This subcortical vasculature is similar to that in the cortex, which also lies beneath large vessels. The LGN lies closer to the large vessels than much of the SC. The differences in response timing between SC and LGN are very similar to those between deep and shallow cortical layers following electrical stimulation, which are related to depth-dependent blood vessel dilation rates. This combined with the similarities in vasculature between subcortex and cortex suggest the SC and LGN timing differences are also related to depth-dependent dilation rates. This study shows for the first time that BOLD responses in the rat SC and LGN following short duration visual stimulation are temporally different.

Contrast-enhanced 3-dimensional SPACE versus MP-RAGE for the detection of brain metastases: considerations with a 32-channel head coil.

PubMed

Reichert, Miriam; Morelli, John N; Runge, Val M; Tao, Ai; von Ritschl, Ruediger; von Ritschl, Andreas; Padua, Abraham; Dix, James E; Marra, Michael J; Schoenberg, Stefan O; Attenberger, Ulrike I

2013-01-01

The aim of this study was to compare the detection of brain metastases at 3 T using a 32-channel head coil with 2 different 3-dimensional (3D) contrast-enhanced sequences, a T1-weighted fast spin-echo-based (SPACE; sampling perfection with application-optimized contrasts using different flip angle evolutions) sequence and a conventional magnetization-prepared rapid gradient-echo (MP-RAGE) sequence. Seventeen patients with 161 brain metastases were examined prospectively using both SPACE and MP-RAGE sequences on a 3-T magnetic resonance system. Eight healthy volunteers were similarly examined for determination of signal-to-noise ratio (SNR) values. Parameters were adjusted to equalize acquisition times between the sequences (3 minutes and 30 seconds). The order in which sequences were performed was randomized. Two blinded board-certified neuroradiologists evaluated the number of detectable metastatic lesions with each sequence relative to a criterion standard reading conducted at the Gamma Knife facility by a neuroradiologist with access to all clinical and imaging data. In the volunteer assessment with SPACE and MP-RAGE, SNR (10.3 ± 0.8 vs 7.7 ± 0.7) and contrast-to-noise ratio (0.8 ± 0.2 vs 0.5 ± 0.1) were statistically significantly greater with the SPACE sequence (P < 0.05). Overall, lesion detection was markedly improved with the SPACE sequence (99.1% of lesions for reader 1 and 96.3% of lesions for reader 2) compared with the MP-RAGE sequence (73.6% of lesions for reader 1 and 68.5% of lesions for reader 2; P < 0.01). A 3D T1-weighted fast spin echo sequence (SPACE) improves detection of metastatic lesions relative to 3D T1-weighted gradient-echo-based scan (MP-RAGE) imaging when implemented with a 32-channel head coil at identical scan acquisition times (3 minutes and 30 seconds).

The robustness of T2 value as a trabecular structural index at multiple spatial resolutions of 7 Tesla MRI.

PubMed

Lee, D K; Song, Y K; Park, B W; Cho, H P; Yeom, J S; Cho, G; Cho, H

2018-04-15

To evaluate the robustness of MR transverse relaxation times of trabecular bone from spin-echo and gradient-echo acquisitions at multiple spatial resolutions of 7 T. The effects of MRI resolutions to T 2 and T2* of trabecular bone were numerically evaluated by Monte Carlo simulations. T 2 , T2*, and trabecular structural indices from multislice multi-echo and UTE acquisitions were measured in defatted human distal femoral condyles on a 7 T scanner. Reference structural indices were extracted from high-resolution microcomputed tomography images. For bovine knee trabecular samples with intact bone marrow, T 2 and T2* were measured by degrading spatial resolutions on a 7 T system. In the defatted trabecular experiment, both T 2 and T2* values showed strong ( |r| > 0.80) correlations with trabecular spacing and number, at a high spatial resolution of 125 µm 3 . The correlations for MR image-segmentation-derived structural indices were significantly degraded ( |r| < 0.50) at spatial resolutions of 250 and 500 µm 3 . The correlations for T2* rapidly dropped ( |r| < 0.50) at a spatial resolution of 500 µm 3 , whereas those for T 2 remained consistently high ( |r| > 0.85). In the bovine trabecular experiments with intact marrow, low-resolution (approximately 1 mm 3 , 2 minutes) T 2 values did not shorten ( |r| > 0.95 with respect to approximately 0.4 mm 3 , 11 minutes) and maintained consistent correlations ( |r| > 0.70) with respect to trabecular spacing (turbo spin echo, 22.5 minutes). T 2 measurements of trabeculae at 7 T are robust with degrading spatial resolution and may be preferable in assessing trabecular spacing index with reduced scan time, when high-resolution 3D micro-MRI is difficult to obtain. © 2018 International Society for Magnetic Resonance in Medicine.

Diffusion weighted whole body imaging with background body signal suppression (DWIBS): technical improvement using free breathing, STIR and high resolution 3D display.

PubMed

Takahara, Taro; Imai, Yutaka; Yamashita, Tomohiro; Yasuda, Seiei; Nasu, Seiji; Van Cauteren, Marc

2004-01-01

To examine a new way of body diffusion weighted imaging (DWI) using the short TI inversion recovery-echo planar imaging (STIR-EPI) sequence and free breathing scanning (diffusion weighted whole body imaging with background body signal suppression; DWIBS) to obtain three-dimensional displays. 1) Apparent contrast-to-noise ratios (AppCNR) between lymph nodes and surrounding fat tissue were compared in three types of DWI with and without breath-holding, with variable lengths of scan time and slice thickness. 2) The STIR-EPI sequence and spin echo-echo planar imaging (SE-EPI) sequence with chemical shift selective (CHESS) pulse were compared in terms of their degree of fat suppression. 3) Eleven patients with neck, chest, and abdominal malignancy were scanned with DWIBS for evaluation of feasibility. Whole body imaging was done in a later stage of the study using the peripheral vascular coil. The AppCNR of 8 mm slice thickness images reconstructed from 4 mm slice thickness source images obtained in a free breathing scan of 430 sec were much better than 9 mm slice thickness breath-hold scans obtained in 25 sec. High resolution multi-planar reformat (MPR) and maximum intensity projection (MIP) images could be made from the data set of 4 mm slice thickness images. Fat suppression was much better in the STIR-EPI sequence than SE-EPI with CHESS pulse. The feasibility of DWIBS was showed in clinical scans of 11 patients. Whole body images were successfully obtained with adequate fat suppression. Three-dimensional DWIBS can be obtained with this technique, which may allow us to screen for malignancies in the whole body.

Defining intrahepatic biliary anatomy in living liver transplant donor candidates at mangafodipir trisodium-enhanced MR cholangiography versus conventional T2-weighted MR cholangiography.

PubMed

Lee, Vivian S; Krinsky, Glenn A; Nazzaro, Carol A; Chang, Jerry S; Babb, James S; Lin, Jennifer C; Morgan, Glyn R; Teperman, Lewis W

2004-12-01

To compare three-dimensional (3D) mangafodipir trisodium-enhanced T1-weighted magnetic resonance (MR) cholangiography with conventional T2-weighted MR cholangiography for depiction and definition of intrahepatic biliary anatomy in liver transplant donor candidates. One hundred eight healthy liver transplant donor candidates were examined with two MR cholangiographic methods. All candidates gave written informed consent, and the study was approved by the institutional review board. First, breath-hold transverse and coronal half-Fourier single-shot turbo spin-echo and breath-hold oblique coronal heavily T2-weighted turbo spin-echo sequences were performed. Second, mangafodipir trisodium-enhanced breath-hold fat-suppressed 3D gradient-echo sequences were performed through the ducts (oblique coronal plane) and through the entire liver (transverse plane). Interpretation of biliary anatomy findings, particularly variants affecting right liver lobe biliary drainage, and degree of interpretation confidence at both 3D mangafodipir trisodium-enhanced MR cholangiography and T2-weighted MR cholangiography were recorded and compared by using the Wilcoxon signed rank test. Then, consensus interpretations of both MR image sets together were performed. Intraoperative cholangiography was the reference-standard examination for 51 subjects who underwent right lobe hepatectomy. The McNemar test was used to compare the accuracies of the individual MR techniques with that of the consensus interpretation of both image sets together and to compare each technique with intraoperative cholangiography. Biliary anatomy was visualized with mangafodipir trisodium enhancement in all patients. Mangafodipir trisodium-enhanced image findings agreed with findings seen at combined interpretations significantly more often than did T2-weighted image findings (in 107 [99%] vs 88 [82%] of 108 donor candidates, P < .001). Confidence was significantly higher with the mangafodipir trisodium-enhanced images than with the T2-weighted images (mean confidence score, 4.5 vs 3.4; P < .001). In the 51 candidates who underwent intraoperative cholangiography, mangafodipir trisodium-enhanced imaging correctly depicted the biliary anatomy more often than did T2-weighted imaging (in 47 [92%] vs 43 [84%] donor candidates, P = .14), whereas the two MR imaging techniques combined correctly depicted the anatomy in 48 (94%) candidates. Mangafodipir trisodium-enhanced 3D MR cholangiography depicts intrahepatic biliary anatomy, especially right duct variants, more accurately than does conventional T2-weighted MR cholangiography. (c) RSNA, 2004.

Intracranial cerebrospinal fluid spaces imaging using a pulse-triggered three-dimensional turbo spin echo MR sequence with variable flip-angle distribution.

PubMed

Hodel, Jérôme; Silvera, Jonathan; Bekaert, Olivier; Rahmouni, Alain; Bastuji-Garin, Sylvie; Vignaud, Alexandre; Petit, Eric; Durning, Bruno; Decq, Philippe

2011-02-01

To assess the three-dimensional turbo spin echo with variable flip-angle distribution magnetic resonance sequence (SPACE: Sampling Perfection with Application optimised Contrast using different flip-angle Evolution) for the imaging of intracranial cerebrospinal fluid (CSF) spaces. We prospectively investigated 18 healthy volunteers and 25 patients, 20 with communicating hydrocephalus (CH), five with non-communicating hydrocephalus (NCH), using the SPACE sequence at 1.5T. Volume rendering views of both intracranial and ventricular CSF were obtained for all patients and volunteers. The subarachnoid CSF distribution was qualitatively evaluated on volume rendering views using a four-point scale. The CSF volumes within total, ventricular and subarachnoid spaces were calculated as well as the ratio between ventricular and subarachnoid CSF volumes. Three different patterns of subarachnoid CSF distribution were observed. In healthy volunteers we found narrowed CSF spaces within the occipital aera. A diffuse narrowing of the subarachnoid CSF spaces was observed in patients with NCH whereas patients with CH exhibited narrowed CSF spaces within the high midline convexity. The ratios between ventricular and subarachnoid CSF volumes were significantly different among the volunteers, patients with CH and patients with NCH. The assessment of CSF spaces volume and distribution may help to characterise hydrocephalus.

Reduction of Diffusion-Weighted Imaging Contrast of Acute Ischemic Stroke at Short Diffusion Times.

PubMed

Baron, Corey Allan; Kate, Mahesh; Gioia, Laura; Butcher, Kenneth; Emery, Derek; Budde, Matthew; Beaulieu, Christian

2015-08-01

Diffusion-weighted imaging (DWI) of tissue water is a sensitive and specific indicator of acute brain ischemia, where reductions of the diffusion of tissue water are observed acutely in the stroke lesion core. Although these diffusion changes have been long attributed to cell swelling, the precise nature of the biophysical mechanisms remains uncertain. The potential cause of diffusion reductions after stroke was investigated using an advanced DWI technique, oscillating gradient spin-echo DWI, that enables much shorter diffusion times and can improve specificity for alterations of structure at the micron level. Diffusion measurements in the white matter lesions of patients with acute ischemic stroke were reduced by only 8% using oscillating gradient spin-echo DWI, in contrast to a 37% decrease using standard DWI. Neurite beading has recently been proposed as a mechanism for the diffusion changes after ischemic stroke with some ex vivo evidence. To explore whether beading could cause such differential results, simulations of beaded cylinders and axonal swelling were performed, yielding good agreement with experiment. Short diffusion times result in dramatically reduced diffusion contrast of human stroke. Simulations implicate a combination of neuronal beading and axonal swelling as the key structural changes leading to the reduced apparent diffusion coefficient after stroke. © 2015 American Heart Association, Inc.

Cerebral hyperperfusion and decreased cerebrovascular reactivity correlate with neurologic disease severity in MELAS.

PubMed

Rodan, L H; Poublanc, J; Fisher, J A; Sobczyk, O; Wong, T; Hlasny, E; Mikulis, D; Tein, I

2015-05-01

To study the mechanisms underlying stroke-like episodes (SLEs) in MELAS syndrome. We performed a case control study in 3 siblings with MELAS syndrome (m.3243A>G tRNA(Leu(UUR))) with variable % mutant mtDNA in blood (35 to 59%) to evaluate regional cerebral blood flow (CBF) and arterial cerebrovascular reactivity (CVR) compared to age- and sex-matched healthy study controls and a healthy control population. Subjects were studied at 3T MRI using arterial spin labeling (ASL) to measure CBF; CVR was measured as a change in % Blood Oxygen Level Dependent signal (as a surrogate of CBF) to repeated 10 mmHg step increase in arterial partial pressure of CO2 (PaCO2). MELAS siblings had decreased CVR (p ≤ 0.002) and increased CBF (p < 0.0026) compared to controls; changes correlated with disease severity and % mutant mtDNA (inversely for CVR: r = -0.82 frontal, r = -0.91 occipital cortex; directly for CBF: r = +0.85 frontal, not for occipital infarct penumbra). Mean CVR was reduced more in frontal (p < 0.001) versus occipital cortex (p = 0.002); mean CBF was increased more in occipital (p = 0.001) than frontal (p = 0.0026) cortices compared to controls. CBF correlated inversely with CVR (r = -0.99 in frontal; not in occipital infarct penumbra) suggesting that increased frontal resting flows are at the expense of flow reserve. MELAS disease severity and mutation load were inversely correlated with Interictal CVR and directly correlated with frontal CBF. These metrics offer further insight into the cerebrovascular hemodynamics in MELAS syndrome and may serve as noninvasive prognostic markers to stratify risk for SLEs. Class III. Copyright © 2015 © Elsevier B.V. and Mitochondria Research Society. Published by Elsevier B.V. All rights reserved.

Detrimental effect of systemic vascular risk factors on brain hemodynamic function assessed with MRI.

PubMed

King, Kevin S; Sheng, Min; Liu, Peiying; Maroules, Christopher D; Rubin, Craig D; Peshock, Ron M; McColl, Roderick W; Lu, Hanzhang

2018-06-01

Background and purpose Vascular risk factors have been associated with decreased cerebral blood flow (CBF) but this is etiologically nonspecific and may result from vascular insufficiency or a response to decreased brain metabolic activity. We apply new MRI techniques to measure oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen consumption (CMRO 2 ), hypothesizing that decreased CBF related to these vascular risk factors will be associated with increased OEF, confirming a primary vascular insufficiency. Methods 3T MRI was obtained on 70 community-based participants in this IRB-approved study with informed consent, with previous assessment of systolic blood pressure, hypertension medication, elevated serum triglycerides, low serum HDL, and diabetes mellitus. CBF was measured using phase contrast adjusted for brain volume (ml/100 g/min), OEF (%) was obtained from T2-Relaxation-Under-Spin-Tagging (TRUST), and CMRO 2 (μmol/100 g/min) was derived using the Fick principle. Stepwise linear regression identified optimal predictors of CBF with age, sex, and hematocrit included for adjustment. This predictive model was then evaluated against OEF and CMRO 2 . Results Hypertriglyceridemia was associated with low CBF and high OEF. High systolic blood pressure was associated with high CBF and low OEF, which was primarily attributable to those with pressures above 160 mmHg. Neither risk factor was associated with significant differences in cerebral metabolic rate. Conclusion Low CBF related to hypertriglyceridemia was accompanied by high OEF with no significant difference in CMRO 2 , confirming subclinical vascular insufficiency. High CBF related to high systolic blood pressure likely reflected limitations of autoregulation at higher blood pressures.

Magnetic resonance imaging of the wrist: bone and cartilage injury.

PubMed

Hayter, Catherine L; Gold, Stephanie L; Potter, Hollis G

2013-05-01

Magnetic resonance imaging (MRI) is particularly useful for imaging the wrist due to its superior soft tissue contrast and ability to detect subtle bone marrow changes and occult fractures. A high field (1.5T or greater) strength, dedicated wrist coil, and high in-plane and through-plane resolution must be utilized to successfully visualize the relatively thin cartilage of the wrist. MRI can be used to detect occult carpal bone fractures, identify complications following scaphoid fractures, and assess for avascular necrosis in the setting in Kienböck's and Preiser's disease. MRI is useful to identify secondary soft tissue and chondral pathology in impaction/impingement syndromes. The use of an intermediate-echo time fast spin echo sequence allows for accurate assessment of articular cartilage, allowing evaluation of chondral wear in the setting of primary osteoarthritis and posttraumatic degenerative arthrosis. MRI is the most sensitive imaging modality for the detection of early inflammatory arthropathies and can detect synovitis, bone marrow edema, and early erosions in the setting of negative radiographs. Copyright © 2012 Wiley Periodicals, Inc.

What is the most suitable MR signal index for quantitative evaluation of placental function using Half-Fourier acquisition single-shot turbo spin-echo compared with T2-relaxation time?

PubMed

Kameyama, Kyoko Nakao; Kido, Aki; Himoto, Yuki; Moribata, Yusaku; Minamiguchi, Sachiko; Konishi, Ikuo; Togashi, Kaori

2018-06-01

Background Half-Fourier acquisition single-shot turbo spin-echo (HASTE) imaging is now widely used for placental and fetal imaging because of its rapidity and low sensitivity to fetal movement. If placental dysfunction is also predicted by quantitative value obtained from HASTE image, then it might be beneficial for evaluating placental wellbeing. Purpose To ascertain the most suitable magnetic resonance (MR) signal indexes reflecting placental function using HASTE imaging. Material and Methods This retrospective study included 37 consequent patients who had given informed consent to MR imaging (MRI) examinations. All had undergone MRI examinations between February 2014 and June 2015. First, the correlation between T2-relaxation time of normal placenta and gestational age (GA) was examined. Second, correlation between signal intensity ratios (SIRs) using HASTE imaging and placental T2-relaxation time were assessed. The SIRs were calculated using placental signal intensity (SI) relative to the SI of the amniotic fluid, fetal ocular globes, gastric fluid, bladder, maternal psoas major muscles, and abdominal subcutaneous adipose tissue. Results Among the 37 patients, the correlation between T2-relaxation time of the 25 normal placentas and GA showed a moderately strong correlation (Spearman rho = -0.447, P = 0.0250). The most significant correlation with placental T2-relaxation time was observed with the placental SIR relative to the maternal psoas major muscles (SIR pl./psoas muscle ) (Spearman rho = -0.531, P = 0.0007). Conclusion This study revealed that SIR pl./psoas muscle showed the best correlation to placental T2-relaxation time. Results show that SIR pl./psoas muscle might be optimal as a clinically available quantitative index of placental function.

Magnetic resonance imaging of the equine temporomandibular joint anatomy.

PubMed

Rodríguez, M J; Agut, A; Soler, M; López-Albors, O; Arredondo, J; Querol, M; Latorre, R

2010-04-01

In human medicine, magnetic resonance imaging (MRI) is considered the 'gold standard' imaging procedure to assess the temporomandibular joint (TMJ). However, there is no information regarding MRI evaluation of equine TMJ. To describe the normal sectional MRI anatomy of equine TMJ by using frozen and plastinated anatomical sections as reference; and determine the best imaging planes and sequences to visualise TMJ components. TMJs from 6 Spanish Purebred horse cadavers (4 immature and 2 mature) underwent MRI examination. Spin-echo T1-weighting (SE T1W), T2*W, fat-suppressed (FS) proton density-weighting (PDW) and fast spin-echo T2-weighting (FSE T2W) sequences were obtained in oblique sagittal, transverse and dorsal planes. Anatomical sections were procured on the same planes for a thorough interpretation. The oblique sagittal and transverse planes were the most informative anatomical planes. SE T1W images showed excellent spatial resolution and resulted in superior anatomic detail when comparing to other sequences. FSE T2W sequence provided an acceptable anatomical depiction but T2*W and fat-suppressed PDW demonstrated higher contrast in visualisation of the disc, synovial fluid, synovial pouches and articular cartilage. The SE T1W sequence in oblique sagittal and transverse plane should be the baseline to identify anatomy. The T2*W and fat-suppressed PDW sequences enhance the study of the articular cartilage and synovial pouches better than FSE T2W. The information provided in this paper should aid clinicians in the interpretation of MRI images of equine TMJ and assist in the early diagnosis of those problems that could not be diagnosed by other means.

The spatial effect of protein deuteration on nitroxide spin-label relaxation: Implications for EPR distance measurement

PubMed Central

El Mkami, Hassane; Ward, Richard; Bowman, Andrew; Owen-Hughes, Tom; Norman, David G.

2014-01-01

Pulsed electron–electron double resonance (PELDOR) coupled with site-directed spin labeling is a powerful technique for the elucidation of protein or nucleic acid, macromolecular structure and interactions. The intrinsic high sensitivity of electron paramagnetic resonance enables measurement on small quantities of bio-macromolecules, however short relaxation times impose a limit on the sensitivity and size of distances that can be measured using this technique. The persistence of the electron spin-echo, in the PELDOR experiment, is one of the most crucial limitations to distance measurement. At a temperature of around 50 K one of the predominant factors affecting persistence of an echo, and as such, the sensitivity and measurable distance between spin labels, is the electron spin echo dephasing time (Tm). It has become normal practice to use deuterated solvents to extend Tm and recently it has been demonstrated that deuteration of the underlying protein significantly extends Tm. Here we examine the spatial effect of segmental deuteration of the underlying protein, and also explore the concentration and temperature dependence of highly deuterated systems. PMID:25310878

Neutron resonance spin-echo upgrade at the three-axis spectrometer FLEXX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Groitl, F., E-mail: felix.groitl@psi.ch; Quintero-Castro, D. L.; Habicht, K.

2015-02-15

We describe the upgrade of the neutron resonance spin-echo setup at the cold neutron triple-axis spectrometer FLEXX at the BER II neutron source at the Helmholtz-Zentrum Berlin. The parameters of redesigned key components are discussed, including the radio frequency (RF) spin-flip coils, the magnetic shield, and the zero field coupling coils. The RF-flippers with larger beam windows allow for an improved neutron flux transfer from the source to the sample and further to the analyzer. The larger beam cross sections permit higher coil inclination angles and enable measurements on dispersive excitations with a larger slope of the dispersion. Due tomore » the compact design of the spin-echo units in combination with the increased coil tilt angles, the accessible momentum-range in the Larmor diffraction mode is substantially enlarged. In combination with the redesigned components of the FLEXX spectrometer, including the guide, the S-bender polarizer, the double focusing monochromator, and a Heusler crystal analyzer, the count rate increased by a factor of 15.5, and the neutron beam polarization is enhanced. The improved performance extends the range of feasible experiments, both for inelastic scattering on excitation lifetimes in single crystals, and for high-resolution Larmor diffraction. The experimental characterization of the instrument components demonstrates the reliable performance of the new neutron resonance spin-echo option, now available for the scientific community at FLEXX.« less

Quantitative assessment of cerebral hemodynamic parameters by QUASAR arterial spin labeling in Alzheimer's disease and cognitively normal Elderly adults at 3-tesla.

PubMed

Mak, Henry K F; Chan, Queenie; Zhang, Zhipeng; Petersen, Esben T; Qiu, Deqiang; Zhang, Linda; Yau, Kelvin K W; Chu, Leung-Wing; Golay, Xavier

2012-01-01

QUASAR arterial spin labeling (ASL) was used to investigate the role of vascular impairment in Alzheimer's disease (AD). We hypothesized that the hemodynamic parameters monitoring cerebrovascular integrity, i.e., cerebral blood flow (CBF), arterial blood volume (aBV), and arterial transit time (aTT), would be affected. 13 AD patients and 15 healthy control (HC) subjects underwent 3T MRI scanning. Two separate blood flow acquisitions were obtained with 1 slice overlap for whole brain coverage. CBF, aBV, and aTT maps were calculated using in-house software. Preprocessing and statistical analyses were performed on SPM5. Region-of-interest (ROI) studies of ten selected cerebral regions were also conducted. There were significant differences in mini mental status exam (MMSE) (AD: 16.3 ± 4.55, HC: 28.5 ± 2.00) and Alzheimer's disease assessment scale-cognitive subscale (ADAS-cog) scores (AD: 25.25 ± 9.64, HC: 5.51 ± 2.62) between the 2 groups (p < 0.001) but none in age (p = 0.068). CBF decreased significantly (p < 0.01) in AD compared to controls in the right middle cingulate, left cuneus, left inferior and middle frontal, right superior frontal, left inferior parietal, and right supramarginal gyri. ROI studies confirmed significant hemodynamic impairments in AD compared to HC (p < 0.05): CBF in middle and posterior cingulate, aBV in left superior temporal, right inferior parietal, and posterior cingulate, and aTT in left inferior frontal and middle cingulate gyri. CBF correlated positively while aTT correlated negatively to MMSE, and vice versa for ADAS-cog. Using QUASAR ASL, we found patterns of regional hemodynamic impairment typical of moderate AD, suggesting underlying vascular abnormality. As potential biomarkers, these hemodynamic parameters could differentiate patients from volunteers, and possibly indicate the conversion from healthy aging to mild cognitive impairment to AD.

Ultrashort echo time (UTE) MRI for the assessment of caries lesions

PubMed Central

Bracher, A-K; Hofmann, C; Bornstedt, A; Hell, E; Janke, F; Ulrici, J; Haller, B; Geibel, M-A; Rasche, V

2013-01-01

Objective: Direct in vivo MRI of dental hard tissues by applying ultrashort echo time (UTE) MRI techniques has recently been reported. The objective of the presented study is to clinically evaluate the applicability of UTE MRI for the identification of caries lesions. Methods: 40 randomly selected patients (mean age 41 ± 15 years) were enrolled in this study. 39 patients underwent a conventional clinical assessment, dental bitewing X-ray and a dental MRI investigation comprising a conventional turbo-spin echo (TSE) and a dedicated UTE scan. One patient had to be excluded owing to claustrophobia. In four patients, the clinical treatment of the lesions was documented by intraoral pictures, and the resulting volume of the cavity after excavation was documented by dental imprints and compared with the MRI findings. Results: In total, 161 lesions were identified. 157 (97%) were visible in the UTE images, 27 (17%) in the conventional TSE images and 137 (85%) in the X-ray images. In total, 14 teeth could not be analysed by MR owing to artefacts caused by dental fillings. All lesions appear significantly larger in the UTE images as compared with the X-ray and TSE images. In situ measurements confirm the accuracy of the lesion dimensions as observed in the UTE images. Conclusion: The presented data provide evidence that UTE MR imaging can be applied for the identification of caries lesions. Although the current data suggest an even higher sensitivity of UTE MRI, some limitations must be expected from dental fillings. PMID:23420857

Lower cerebral blood flow in subjects with Alzheimer's dementia, mild cognitive impairment, and subjective cognitive decline using two-dimensional phase-contrast magnetic resonance imaging.

PubMed

Leijenaar, Jolien F; van Maurik, Ingrid S; Kuijer, Joost P A; van der Flier, Wiesje M; Scheltens, Philip; Barkhof, Frederik; Prins, Niels D

2017-01-01

In this cross-sectional study, we aimed to detect differences in cerebral blood flow (CBF) between subjects with Alzheimer's disease (AD), mild cognitive impairment (MCI), and subjective cognitive decline (SCD), using two-dimensional phase-contrast magnetic resonance imaging. We included 74 AD patients (67 years, 51% female), 36 MCI patients (66 years, 33% female), and 62 patients with SCD (60 years, 32% female) from the Amsterdam Dementia Cohort. Patients with SCD are those who visited the memory clinic with subjective cognitive complaints without objective cognitive impairment. Whole-brain CBF (mL/100 g/min) was calculated using total volume flow measured with two-dimensional phase-contrast magnetic resonance imaging and normalized for brain volume. Mean CBF values (SD) were lower in AD compared to SCD (age and sex adjusted 70 ± 26 vs. 82 ± 24 mL/100 g/min, P  < .05). Mean CBF values of MCI were comparable to AD. Across clinical groups, lower CBF was associated with lower scores on the Mini-Mental State Examination (age and sex adjusted stβ = 0.19 per mL/100 g/min; P  = .02). Lower whole-brain CBF is seen in AD patients compared to SCD patients and is associated with worse cognitive function.

Dynamic change in cerebral microcirculation and focal cerebral metabolism in experimental subarachnoid hemorrhage in rabbits.

PubMed

Song, Jin-Ning; Chen, Hu; Zhang, Ming; Zhao, Yong-Lin; Ma, Xu-Dong

2013-03-01

Regional cerebral blood flow (rCBF) in the cerebral metabolism and energy metabolism measurements can be used to assess blood flow of brain cells and to detect cell activity. Changes of rCBF in the cerebral microcirculation and energy metabolism were determined in an experimental model of subarachnoid hemorrhage (SAH) model in 56 large-eared Japanese rabbits about 12 to 16-month old. Laser Doppler flowmetry was used to detect the blood supply to brain cells. Internal carotid artery and vein blood samples were used for duplicate blood gas analysis to assess the energy metabolism of brain cells. Cerebral blood flow (CBF) was detected by single photon emission computed tomography (SPECT) perfusion imaging using Tc-99m ethyl cysteinate dimer (Tc-99m ECD) as an imaging reagent. The percentage of injected dose per gram of brain tissue was calculated and analyzed. There were positive correlations between the percentage of radionuclide injected per gram of brain tissue and rCBF supply and cerebral metabolic rate for oxygen (P < 0.05). However, there was a negative correlation between radioactivity counts per unit volume detected on the SPECT rheoencephalogram and lactic acid concentration in the homolateral internal carotid artery and vein. In summary, this study found abnormal CBF in metabolism and utilization of brain cells after SAH, and also found that deterioration of energy metabolism of brain cells played a significant role in the development of SAH. There are matched reductions in CBF and metabolism. Thus, SPECT imaging could be used as a noninvasive method to detect CBF.

TU-EF-BRA-02: Longitudinal Proton Spin Relaxation and T1-Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemen, L.

NMR, and Proton Density MRI of the 1D Patient - Anthony Wolbarst Net Voxel Magnetization, m(x,t). T1-MRI; The MRI Device - Lisa Lemen ‘Classical’ NMR; FID Imaging in 1D via k-Space - Nathan Yanasak Spin-Echo; S-E/Spin Warp in a 2D Slice - Ronald Price Magnetic resonance imaging not only reveals the structural, anatomic details of the body, as does CT, but also it can provide information on the physiological status and pathologies of its tissues, like nuclear medicine. It can display high-quality slice and 3D images of organs and vessels viewed from any perspective, with resolution better than 1 mm.more » MRI is perhaps most extraordinary and notable for the plethora of ways in which it can create unique forms of image contrast, reflective of fundamentally different biophysical phenomena. As with ultrasound, there is no risk from ionizing radiation to the patient or staff, since no X-rays or radioactive nuclei are involved. Instead, MRI harnesses magnetic fields and radio waves to probe the stable nuclei of the ordinary hydrogen atoms (isolated protons) occurring in water and lipid molecules within and around cells. MRI consists, in essence, of creating spatial maps of the electromagnetic environments around these hydrogen nuclei. Spatial variations in the proton milieus can be related to clinical differences in the biochemical and physiological properties and conditions of the associated tissues. Imaging of proton density (PD), and of the tissue proton spin relaxation times known as T1 and T2, all can reveal important clinical information, but they do so with approaches so dissimilar from one another that each is chosen for only certain clinical situations. T1 and T2 in a voxel are determined by different aspects of the rotations and other motions of the water and lipid molecules involved, as constrained by the local biophysical surroundings within and between its cells – and they, in turn, depend on the type of tissue and its state of health. Three other common applications of MRI exploit its capability to detect and image distinct movements of fluids: MR angiography (MRA), which rivals CT angiography but often requires no contrast medium, monitors the bulk flow of blood; functional MRI ( f MRI), distinguishes the perfusion of oxygenated blood from that of de-oxygenated, and lights up parts of the brain that are activated by a stimulus, rather like PET; and diffusion tensor imaging (DTI) indicates the diffusion of free water along tracts of axons, thereby bringing nerve trunks into view. There are variants on all of these themes, and on others as well. Magnetic Resonance Spectroscopy (MRS), for example, can perform non-invasive ‘virtual biopsies’ that allow identification of certain cancers and other lesions. And an MRI-guided needle biopsy can sample brain tissue from a region only millimeters in dimensions. MRI, however, involves deeper and more complex aspects of physics, technology, and biology than do most other imaging modalities, and it is widely considered to be correspondingly more difficult to learn. We could probably cover all of this rather comprehensively if we had 50 hours available rather than 2 ̶ but, to paraphrase a former Secretary of Defense, you tell your story in the time you have allotted. The four presenters and another physicist, Kevin King from GE, have combined their efforts to co-author a single slide show that describes essentials of MRI as simply as possible. It is obviously far from thorough, but hopefully it will succeed in explaining some of the basics in a simplified but still valid fashion; in providing a taste of the numerous capabilities and complexities of the modality; and in whetting your appetite to learn more. Part I. NMR, and Proton Density MRI of the 1D Patient (Wolbarst), begins with an introductory case study that illustrates a half dozen ways in which MRI provides valuable clinical information. It then explores the nuclear magnetic resonance (NMR) phenomenon, which underlies MRI. NMR can be introduced with either of two approaches. In the first, one thinks (loosely) of the nuclei of hydrogen atoms as (rotating and charged and therefore) magnetic objects, whose spin-axes tend to align in a strong external magnetic field, much like a compass needle. As with the Bohr atom, this spin-up/spin-down picture is a highly abridged version of the full quantum mechanical treatment, but still it leads to some useful, legitimate pictures of the NMR process occurring within a voxel: When RF photons of the correct (Larmor) frequency elevate protons in a fixed magnetic field out of their lower-energy spin state into the upper, the NMR phenomenon is indicated by the detectable absorption of RF power. With the addition of a linear gradient field along a multi-voxel, one-dimensional patient/phantom, as well, we can determine the water content of each compartment – an example of a real MRI study, albeit in 1D. Part I concludes with a discussion of the net magnetization at position x, m0(x), under conditions of dynamic thermal equilibrium, which leads into: Part II. Net Voxel Magnetization, m(x,t); T1-MRI; The MRI Device (Lemen), investigates the biophysics of the form of proton spin relaxation process characterized by the time T1. It then moves on to the creation of an MR image that displays the spatial variation in the values of this clinically relevant parameter, again in 1D. Finally, the design and workings of a clinical MRI machine are sketched, in preparation for: Part III. ‘Classical’ NMR; FID Imaging in 1D via k-Space (Yanasak) presents the second standard approach to NMR and MRI, the classical model. It focuses on the time dependence of the net nuclear magnetization, m(x,t), the overall magnetic field generated by the cohort of protons in the voxel at position x. Quite remarkably, this nuclear net magnetization itself acts in a strong magnetic field like a gyroscope in a gravitational field. This tack is better for explaining Free Induction Decay (FID), which involves a brief introduction to the Fourier transform and k-space. This leads to conventional Spin-Echo (S-E) reconstruction techniques for creating clinical images from raw data, and sets the stage for: Part IV. Spin-Echo; S-E / Spin Warp in a 2D Slice (Price) discusses application of the S- E sequence of radiofrequency pulses and gradient magnetic fields to the 1D patient. T2 is introduced but not explained. This Part also considers how to manipulate the image acquisition parameters so as to generate clinical pictures with contrast dominated by spatial variations in PD, T1, or T2. We conclude by demonstrating the spin-warp approach to imaging in 2D with a simple 2×2, 4-voxel example. Much of this material is presented in more detail in the chapter “MRI of the One-dimensional Patient, Part I”, in Advances in Medical Physics, Vol 5 (2014). Copies are on display at the Medical Physics Publishing booth. Learning Objectives: The participant will learn about the processes of NMR and T1 spin relaxation in a tissue voxel in a uniform magnetic field. The participant will learn about combining spin-up/spin-down NMR and T1 processes with a linear gradient to effect frequency-encoding of voxel spatial position. This approach can be used to create proton density and T1 MRI maps, respectively, of the contents of multi-voxel 1D phantoms. The participant will learn about how the ‘classical’ model of NMR it can generate Free Induction Decay (FID) images of 1D phantoms, which involves the use of the Fourier transform in k-space. This can lead simply into standard Spin-Echo images. The participant will learn about extending Spin-Echo imaging into 2 and more dimensions.« less

Comparison of pulse sequences for R1-based electron paramagnetic resonance oxygen imaging.

PubMed

Epel, Boris; Halpern, Howard J

2015-05-01

Electron paramagnetic resonance (EPR) spin-lattice relaxation (SLR) oxygen imaging has proven to be an indispensable tool for assessing oxygen partial pressure in live animals. EPR oxygen images show remarkable oxygen accuracy when combined with high precision and spatial resolution. Developing more effective means for obtaining SLR rates is of great practical, biological and medical importance. In this work we compared different pulse EPR imaging protocols and pulse sequences to establish advantages and areas of applicability for each method. Tests were performed using phantoms containing spin probes with oxygen concentrations relevant to in vivo oxymetry. We have found that for small animal size objects the inversion recovery sequence combined with the filtered backprojection reconstruction method delivers the best accuracy and precision. For large animals, in which large radio frequency energy deposition might be critical, free induction decay and three pulse stimulated echo sequences might find better practical usage. Copyright © 2015 Elsevier Inc. All rights reserved.

All-optical control of long-lived nuclear spins in rare-earth doped nanoparticles.

PubMed

Serrano, D; Karlsson, J; Fossati, A; Ferrier, A; Goldner, P

2018-05-29

Nanoscale systems that coherently couple to light and possess spins offer key capabilities for quantum technologies. However, an outstanding challenge is to preserve properties, and especially optical and spin coherence lifetimes, at the nanoscale. Here, we report optically controlled nuclear spins with long coherence lifetimes (T 2 ) in rare-earth-doped nanoparticles. We detect spins echoes and measure a spin coherence lifetime of 2.9 ± 0.3 ms at 5 K under an external magnetic field of 9 mT, a T 2 value comparable to those obtained in bulk rare-earth crystals. Moreover, we achieve spin T 2 extension using all-optical spin dynamical decoupling and observe high fidelity between excitation and echo phases. Rare-earth-doped nanoparticles are thus the only nano-material in which optically controlled spins with millisecond coherence lifetimes have been reported. These results open the way to providing quantum light-atom-spin interfaces with long storage time within hybrid architectures.

Skew Projection of Echo-Detected EPR Spectra for Increased Sensitivity and Resolution

PubMed Central

Bowman, Michael K.; Krzyaniak, Matthew D.; Cruce, Alex A.; Weber, Ralph T.

2013-01-01

The measurement of EPR spectra during pulsed EPR experiments is commonly accomplished by recording the integral of the electron spin echo as the applied magnetic field is stepped through the spectrum. This approach to echo-detected EPR spectral measurement (ED-EPR) limits sensitivity and spectral resolution and can cause gross distortions in the resulting spectra because some of the information present in the electron spin echo is discarded in such measurements. However, Fourier Transformation of echo shapes measured at a series of magnetic field values followed by skew projection onto either a magnetic field or resonance frequency axis can increase both spectral resolution and sensitivity without the need to trade one against the other. Examples of skew-projected spectra with single crystals, glasses and powders show resolution improvements as large as a factor of seven with sensitivity increases of as much as a factor of five. PMID:23644351

Skew projection of echo-detected EPR spectra for increased sensitivity and resolution

NASA Astrophysics Data System (ADS)

Bowman, Michael K.; Krzyaniak, Matthew D.; Cruce, Alex A.; Weber, Ralph T.

2013-06-01

The measurement of EPR spectra during pulsed EPR experiments is commonly accomplished by recording the integral of the electron spin echo as the applied magnetic field is stepped through the spectrum. This approach to echo-detected EPR spectral measurement (ED-EPR) limits sensitivity and spectral resolution and can cause gross distortions in the resulting spectra because some of the information present in the electron spin echo is discarded in such measurements. However, Fourier transformation of echo shapes measured at a series of magnetic field values followed by skew projection onto either a magnetic field or resonance frequency axis can increase both spectral resolution and sensitivity without the need to trade one against the other. Examples of skew-projected spectra with single crystals, glasses and powders show resolution improvements as large as a factor of seven with sensitivity increases of as much as a factor of five.

Elevated global cerebral blood flow, oxygen extraction fraction and unchanged metabolic rate of oxygen in young adults with end-stage renal disease: an MRI study.

PubMed

Zheng, Gang; Wen, Jiqiu; Lu, Hanzhang; Lou, Yaxian; Pan, Zhiying; Liu, Wei; Liu, Hui; Li, Xue; Zhang, Zhe; Chen, Huijuan; Kong, Xiang; Luo, Song; Jiang, Xiaolu; Liu, Ya; Zhang, Zongjun; Zhang, Long Jiang; Lu, Guang Ming

2016-06-01

To noninvasively assess global cerebral blood flow (CBF), oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO2) in young adults with end-stage renal disease (ESRD). Thirty-six patients and 38 healthy volunteers were included and took part in MR examinations, blood and neuropsychological tests. CBF and OEF were measured by phase-contrast and T2-relaxation-under-spin-tagging MRI techniques, respectively. CMRO2 was computed from CBF, OEF and hematocrit according to Fick's principle. Correlations were performed between MR measurements, blood biochemistry measurements and neuropsychological test scores. Compared with controls, ESRD patients had elevated CBF (72.9 ± 12.5 vs. 63.8 ± 8.5 ml min(-1) 100 g(-1), P < 0.001), elevated OEF (47.2 ± 10.2 vs. 35.8 ± 5.4 %, P < 0.001), but unaffected CMRO2 (199.5 ± 36.4 vs. 193.8 ± 28.6 μmol O2 min(-1) 100 g(-1), P = 0.879). Hematocrit negatively correlated with CBF (r = -0.640, P < 0.001) and OEF (r = -0.701, P < 0.001), but not with CMRO2. Altered neuropsychological test scores of ESRD patients were associated with OEF and CBF, but not with CMRO2. There were weak relationships between eGFR and hematocrit (r = 0.308, P = 0.068) or CBF (r = 0.318, P = 0.059). Our findings suggested that anaemic young adults with ESRD may afford higher CBF and OEF to maintain a normal CMRO2. Despite this compensatory process, however, cognitive function was still impaired and its severity was correlated with their CBF and OEF abnormality. • Anaemic young adults with ESRD may afford higher CBF and OEF. • Anaemic young adults with ESRD maintain a normal CMRO 2 . • Cognitive function was still impaired in young ESRD adults. • The severity of cognitive dysfunction correlated with CBF and OEF changes.

High spatial resolution diffusion weighted imaging on clinical 3 T MRI scanners using multislab spiral acquisitions

PubMed Central

Holtrop, Joseph L.; Sutton, Bradley P.

2016-01-01

Abstract. A diffusion weighted imaging (DWI) approach that is signal-to-noise ratio (SNR) efficient and can be applied to achieve sub-mm resolutions on clinical 3 T systems was developed. The sequence combined a multislab, multishot pulsed gradient spin echo diffusion scheme with spiral readouts for imaging data and navigators. Long data readouts were used to keep the number of shots, and hence total imaging time, for the three-dimensional acquisition short. Image quality was maintained by incorporating a field-inhomogeneity-corrected image reconstruction to remove distortions associated with long data readouts. Additionally, multiple shots were required for the high-resolution images, necessitating motion induced phase correction through the use of efficiently integrated navigator data. The proposed approach is compared with two-dimensional (2-D) acquisitions that use either a spiral or a typical echo-planar imaging (EPI) acquisition to demonstrate the improved SNR efficiency. The proposed technique provided 71% higher SNR efficiency than the standard 2-D EPI approach. The adaptability of the technique to achieve high spatial resolutions is demonstrated by acquiring diffusion tensor imaging data sets with isotropic resolutions of 1.25 and 0.8 mm. The proposed approach allows for SNR-efficient sub-mm acquisitions of DWI data on clinical 3 T systems. PMID:27088107

Improved fat-suppression homogeneity with mDIXON turbo spin echo (TSE) in pediatric spine imaging at 3.0 T.

PubMed

Pokorney, Amber L; Chia, Jonathan M; Pfeifer, Cory M; Miller, Jeffrey H; Hu, Houchun H

2017-11-01

Background Robust fat suppression remains essential in clinical MRI to improve tissue signal contrast, minimize fat-related artifacts, and enhance image quality. Purpose To compare fat suppression between mDIXON turbo spin echo (TSE) and conventional frequency-selective and inversion-recovery methods in pediatric spine MRI. Material and Methods Images from T1-weighted (T1W) and T2-weighted (T2W) TSE sequences coupled with conventional methods and the mDIXON technique were compared in 36 patients (5.8 ± 5.4 years) at 3.0 T. Images from 42 pairs of T1W (n = 16) and T2W (n = 26) scans were acquired. Two radiologists reviewed the data and rated images using a three-point scale in two categories, including the uniformity of fat suppression and overall diagnostic image quality. The Wilcoxon rank-sum test was used to compare the scores. Results The Cohen's kappa coefficient for inter-rater agreement was 0.69 (95% confidence interval [CI], 0.56-0.83). Images from mDIXON TSE were considered superior in fat suppression ( P < 0.01) in 22 (rater 1) and 25 (rater 2) cases, respectively. In 13 (rater 1) and 11 (rater 2) cases, mDIXON TSE demonstrated improved diagnostic image quality ( P < 0.01). In three cases, fat suppression was superior using inversion-recovery and likewise in one case mDIXON had poorer image diagnostic quality. Lastly, mDIXON and conventional fat-suppression methods performed similarly in 17 (rater 1) and 14 (rater 2) cases, and yielded equal diagnostic image quality in 28 (rater 1) and 30 (rater 2) cases. Conclusion Robust fat suppression can be achieved with mDixon TSE pediatric spine imaging at 3.0 T and should be considered as a permanent replacement of traditional methods, in particular frequency-selective techniques.

Ultrahigh-resolution imaging of the human brain with phase-cycled balanced steady-state free precession at 7 T.

PubMed

Zeineh, Michael M; Parekh, Mansi B; Zaharchuk, Greg; Su, Jason H; Rosenberg, Jarrett; Fischbein, Nancy J; Rutt, Brian K

2014-05-01

The objectives of this study were to acquire ultra-high resolution images of the brain using balanced steady-state free precession (bSSFP) at 7 T and to identify the potential utility of this sequence. Eight volunteers participated in this study after providing informed consent. Each volunteer was scanned with 8 phase cycles of bSSFP at 0.4-mm isotropic resolution using 0.5 number of excitations and 2-dimensional parallel acceleration of 1.75 × 1.75. Each phase cycle required 5 minutes of scanning, with pauses between the phase cycles allowing short periods of rest. The individual phase cycles were aligned and then averaged. The same volunteers underwent scanning using 3-dimensional (3D) multiecho gradient recalled echo at 0.8-mm isotropic resolution, 3D Cube T2 at 0.7-mm isotropic resolution, and thin-section coronal oblique T2-weighted fast spin echo at 0.22 × 0.22 × 2.0-mm resolution for comparison. Two neuroradiologists assessed image quality and potential research and clinical utility. The volunteers generally tolerated the scan sessions well, and composite high-resolution bSSFP images were produced for each volunteer. Rater analysis demonstrated that bSSFP had a superior 3D visualization of the microarchitecture of the hippocampus, very good contrast to delineate the borders of the subthalamic nucleus, and relatively good B1 homogeneity throughout. In addition to an excellent visualization of the cerebellum, subtle details of the brain and skull base anatomy were also easier to identify on the bSSFP images, including the line of Gennari, membrane of Liliequist, and cranial nerves. Balanced steady-state free precession had a strong iron contrast similar to or better than the comparison sequences. However, cortical gray-white contrast was significantly better with Cube T2 and T2-weighted fast spin echo. Balanced steady-state free precession can facilitate ultrahigh-resolution imaging of the brain. Although total imaging times are long, the individually short phase cycles can be acquired separately, improving examination tolerability. These images may be beneficial for studies of the hippocampus, iron-containing structures such as the subthalamic nucleus and line of Gennari, and the basal cisterns and their contents.

In vitro determination of biomechanical properties of human articular cartilage in osteoarthritis using multi-parametric MRI

NASA Astrophysics Data System (ADS)

Juras, Vladimir; Bittsansky, Michal; Majdisova, Zuzana; Szomolanyi, Pavol; Sulzbacher, Irene; Gäbler, Stefan; Stampfl, Jürgen; Schüller, Georg; Trattnig, Siegfried

2009-03-01

The objective of this study was to evaluate the correlations between MR parameters and the biomechanical properties of naturally degenerated human articular cartilage. Human cartilage explants from the femoral condyles of patients who underwent total knee replacement were evaluated on a micro-imaging system at 3 T. To quantify glycosaminoglycan (GAG) content, delayed gadolinium-enhanced MRI of the cartilage (dGEMRIC) was used. T2 maps were created by using multi-echo, multi-slice spin echo sequences with six echoes: 15, 30, 45, 60, 75, and 90 ms. Data for apparent diffusion constant (ADC) maps were obtained from pulsed gradient spin echo (PGSE) sequences with five b-values: 10.472, 220.0, 627.0, 452.8, 724.5, and 957.7. MR parameters were correlated with mechanical parameters (instantaneous ( I) and equilibrium ( Eq) modulus and relaxation time ( τ)), and the OA stage of each cartilage specimen was determined by histological evaluation of hematoxylin-eosin stained slices. For some parameters, a high correlation was found: the correlation of T1Gd vs Eq ( r = 0.8095), T1Gd vs I/ Eq ( r = -0.8441) and T1Gd vs τ ( r = 0.8469). The correlation of T2 and ADC with selected biomechanical parameters was not statistically significant. In conclusion, GAG content measured by dGEMRIC is highly related to the selected biomechanical properties of naturally degenerated articular cartilage. In contrast, T2 and ADC were unable to estimate these properties. The results of the study imply that some MR parameters can non-invasively predict the biomechanical properties of degenerated articular cartilage.

Development of PET/MRI with insertable PET for simultaneous PET and MR imaging of human brain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, Jin Ho; Choi, Yong, E-mail: ychoi.image@gmail.com; Jung, Jiwoong

2015-05-15

Purpose: The purpose of this study was to develop a dual-modality positron emission tomography (PET)/magnetic resonance imaging (MRI) with insertable PET for simultaneous PET and MR imaging of the human brain. Methods: The PET detector block was composed of a 4 × 4 matrix of detector modules, each consisting of a 4 × 4 array LYSO coupled to a 4 × 4 Geiger-mode avalanche photodiode (GAPD) array. The PET insert consisted of 18 detector blocks, circularly mounted on a custom-made plastic base to form a ring with an inner diameter of 390 mm and axial length of 60 mm. Themore » PET gantry was shielded with gold-plated conductive fabric tapes with a thickness of 0.1 mm. The charge signals of PET detector transferred via 4 m long flat cables were fed into the position decoder circuit. The flat cables were shielded with a mesh-type aluminum sheet with a thickness of 0.24 mm. The position decoder circuit and field programmable gate array-embedded DAQ modules were enclosed in an aluminum box with a thickness of 10 mm and located at the rear of the MR bore inside the MRI room. A 3-T human MRI system with a Larmor frequency of 123.7 MHz and inner bore diameter of 60 cm was used as the PET/MRI hybrid system. A custom-made radio frequency (RF) coil with an inner diameter of 25 cm was fabricated. The PET was positioned between gradient and the RF coils. PET performance was measured outside and inside the MRI scanner using echo planar imaging, spin echo, turbo spin echo, and gradient echo sequences. MRI performance was also evaluated with and without the PET insert. The stability of the newly developed PET insert was evaluated and simultaneous PET and MR images of a brain phantom were acquired. Results: No significant degradation of the PET performance caused by MR was observed when the PET was operated using various MR imaging sequences. The signal-to-noise ratio of MR images was slightly degraded due to the PET insert installed inside the MR bore while the homogeneity was maintained. The change of gain of the 256 GAPD/scintillator elements of a detector block was <3% for 60 min, and simultaneous PET and MR images of a brain phantom were successfully acquired. Conclusions: Experimental results indicate that a compact and lightweight PET insert for hybrid PET/MRI can be developed using GAPD arrays and charge signal transmission method proposed in this study without significant interference.« less

Observation of Gravitationally Induced Vertical Striation of Polarized Ultracold Neutrons by Spin-Echo Spectroscopy

NASA Astrophysics Data System (ADS)

Afach, S.; Ayres, N. J.; Ban, G.; Bison, G.; Bodek, K.; Chowdhuri, Z.; Daum, M.; Fertl, M.; Franke, B.; Griffith, W. C.; Grujić, Z. D.; Harris, P. G.; Heil, W.; Hélaine, V.; Kasprzak, M.; Kermaidic, Y.; Kirch, K.; Knowles, P.; Koch, H.-C.; Komposch, S.; Kozela, A.; Krempel, J.; Lauss, B.; Lefort, T.; Lemière, Y.; Mtchedlishvili, A.; Musgrave, M.; Naviliat-Cuncic, O.; Pendlebury, J. M.; Piegsa, F. M.; Pignol, G.; Plonka-Spehr, C.; Prashanth, P. N.; Quéméner, G.; Rawlik, M.; Rebreyend, D.; Ries, D.; Roccia, S.; Rozpedzik, D.; Schmidt-Wellenburg, P.; Severijns, N.; Thorne, J. A.; Weis, A.; Wursten, E.; Wyszynski, G.; Zejma, J.; Zenner, J.; Zsigmond, G.

2015-10-01

We describe a spin-echo method for ultracold neutrons (UCNs) confined in a precession chamber and exposed to a |B0|=1 μ T magnetic field. We have demonstrated that the analysis of UCN spin-echo resonance signals in combination with knowledge of the ambient magnetic field provides an excellent method by which to reconstruct the energy spectrum of a confined ensemble of neutrons. The method takes advantage of the relative dephasing of spins arising from a gravitationally induced striation of stored UCNs of different energies, and also permits an improved determination of the vertical magnetic-field gradient with an exceptional accuracy of 1.1 pT /cm . This novel combination of a well-known nuclear resonance method and gravitationally induced vertical striation is unique in the realm of nuclear and particle physics and should prove to be invaluable for the assessment of systematic effects in precision experiments such as searches for an electric dipole moment of the neutron or the measurement of the neutron lifetime.

DOE Office of Scientific and Technical Information (OSTI.GOV)

van den Berg, R.; Brandino, G. P.; El Araby, O.

In this study, we introduce an integrability-based method enabling the study of semiconductor quantum dot models incorporating both the full hyperfine interaction as well as a mean-field treatment of dipole-dipole interactions in the nuclear spin bath. By performing free induction decay and spin echo simulations we characterize the combined effect of both types of interactions on the decoherence of the electron spin, for external fields ranging from low to high values. We show that for spin echo simulations the hyperfine interaction is the dominant source of decoherence at short times for low fields, and competes with the dipole-dipole interactions atmore » longer times. On the contrary, at high fields the main source of decay is due to the dipole-dipole interactions. In the latter regime an asymmetry in the echo is observed. Furthermore, the non-decaying fraction previously observed for zero field free induction decay simulations in quantum dots with only hyperfine interactions, is destroyed for longer times by the mean-field treatment of the dipolar interactions.« less

Competing interactions in semiconductor quantum dots

DOE PAGES

van den Berg, R.; Brandino, G. P.; El Araby, O.; ...

2014-10-14

In this study, we introduce an integrability-based method enabling the study of semiconductor quantum dot models incorporating both the full hyperfine interaction as well as a mean-field treatment of dipole-dipole interactions in the nuclear spin bath. By performing free induction decay and spin echo simulations we characterize the combined effect of both types of interactions on the decoherence of the electron spin, for external fields ranging from low to high values. We show that for spin echo simulations the hyperfine interaction is the dominant source of decoherence at short times for low fields, and competes with the dipole-dipole interactions atmore » longer times. On the contrary, at high fields the main source of decay is due to the dipole-dipole interactions. In the latter regime an asymmetry in the echo is observed. Furthermore, the non-decaying fraction previously observed for zero field free induction decay simulations in quantum dots with only hyperfine interactions, is destroyed for longer times by the mean-field treatment of the dipolar interactions.« less

MRI of the wrist at 7 tesla using an eight-channel array coil combined with parallel imaging: preliminary results.

PubMed

Chang, Gregory; Friedrich, Klaus M; Wang, Ligong; Vieira, Renata L R; Schweitzer, Mark E; Recht, Michael P; Wiggins, Graham C; Regatte, Ravinder R

2010-03-01

To determine the feasibility of performing MRI of the wrist at 7 Tesla (T) with parallel imaging and to evaluate how acceleration factors (AF) affect signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and image quality. This study had institutional review board approval. A four-transmit eight-receive channel array coil was constructed in-house. Nine healthy subjects were scanned on a 7T whole-body MR scanner. Coronal and axial images of cartilage and trabecular bone micro-architecture (3D-Fast Low Angle Shot (FLASH) with and without fat suppression, repetition time/echo time = 20 ms/4.5 ms, flip angle = 10 degrees , 0.169-0.195 x 0.169-0.195 mm, 0.5-1 mm slice thickness) were obtained with AF 1, 2, 3, 4. T1-weighted fast spin-echo (FSE), proton density-weighted FSE, and multiple-echo data image combination (MEDIC) sequences were also performed. SNR and CNR were measured. Three musculoskeletal radiologists rated image quality. Linear correlation analysis and paired t-tests were performed. At higher AF, SNR and CNR decreased linearly for cartilage, muscle, and trabecular bone (r < -0.98). At AF 4, reductions in SNR/CNR were:52%/60% (cartilage), 72%/63% (muscle), 45%/50% (trabecular bone). Radiologists scored images with AF 1 and 2 as near-excellent, AF 3 as good-to-excellent (P = 0.075), and AF 4 as average-to-good (P = 0.11). It is feasible to perform high resolution 7T MRI of the wrist with parallel imaging. SNR and CNR decrease with higher AF, but image quality remains above-average.

Simultaneous and Noninvasive Imaging of Cerebral Oxygen Metabolic Rate, Blood Flow and Oxygen Extraction Fraction in Stroke Mice

PubMed Central

Zhu, Xiao-Hong; Chen, James; Tu, Tsang-Wei; Chen, Wei; Song, Sheng-Kwei

2012-01-01

Many brain diseases have been linked to abnormal oxygen metabolism and blood perfusion; nevertheless, there is still a lack of robust diagnostic tools for directly imaging cerebral metabolic rate of oxygen (CMRO2) and cerebral blood flow (CBF), as well as the oxygen extraction fraction (OEF) that reflects the balance between CMRO2 and CBF. This study employed the recently developed in vivo 17O MR spectroscopic imaging to simultaneously assess CMRO2, CBF and OEF in the brain using a preclinical middle cerebral arterial occlusion mouse model with a brief inhalation of 17O-labeled oxygen gas. The results demonstrated high sensitivity and reliability of the noninvasive 17O-MR approach for rapidly imaging CMRO2, CBF and OEF abnormalities in the ischemic cortex of the MCAO mouse brain. It was found that in the ischemic brain regions both CMRO2 and CBF were substantially lower than that of intact brain regions, even for the mildly damaged brain regions that were unable to be clearly identified by the conventional MRI. In contrast, OEF was higher in the MCAO affected brain regions. This study demonstrates a promising 17O MRI technique for imaging abnormal oxygen metabolism and perfusion in the diseased brain regions. This 17O MRI technique is advantageous because of its robustness, simplicity, noninvasiveness and reliability: features that are essential to potentially translate it to human patients for early diagnosis and monitoring of treatment efficacy. PMID:23000789

Simultaneous and noninvasive imaging of cerebral oxygen metabolic rate, blood flow and oxygen extraction fraction in stroke mice.

PubMed

Zhu, Xiao-Hong; Chen, James M; Tu, Tsang-Wei; Chen, Wei; Song, Sheng-Kwei

2013-01-01

Many brain diseases have been linked to abnormal oxygen metabolism and blood perfusion; nevertheless, there is still a lack of robust diagnostic tools for directly imaging cerebral metabolic rate of oxygen (CMRO(2)) and cerebral blood flow (CBF), as well as the oxygen extraction fraction (OEF) that reflects the balance between CMRO(2) and CBF. This study employed the recently developed in vivo (17)O MR spectroscopic imaging to simultaneously assess CMRO(2), CBF and OEF in the brain using a preclinical middle cerebral arterial occlusion mouse model with a brief inhalation of (17)O-labeled oxygen gas. The results demonstrated high sensitivity and reliability of the noninvasive (17)O-MR approach for rapidly imaging CMRO(2), CBF and OEF abnormalities in the ischemic cortex of the MCAO mouse brain. It was found that in the ischemic brain regions both CMRO(2) and CBF were substantially lower than that of intact brain regions, even for the mildly damaged brain regions that were unable to be clearly identified by the conventional MRI. In contrast, OEF was higher in the MCAO affected brain regions. This study demonstrates a promising (17)O MRI technique for imaging abnormal oxygen metabolism and perfusion in the diseased brain regions. This (17)O MRI technique is advantageous because of its robustness, simplicity, noninvasiveness and reliability: features that are essential to potentially translate it to human patients for early diagnosis and monitoring of treatment efficacy. Copyright © 2012 Elsevier Inc. All rights reserved.

Half Fourier single-shot turbo spin-echo magnetic resonance urography for the evaluation of suspected renal colic in pregnancy.

PubMed

Mullins, Jeffrey K; Semins, Michelle J; Hyams, Elias S; Bohlman, Mark E; Matlaga, Brian R

2012-06-01

To report our experience with magnetic resonance urography (MRU) in pregnant women suspected of having obstructing upper tract calculi. The diagnosis of an upper tract calculus in the pregnant woman can be challenging. Recent evidence suggests that MRU can be used to effectively evaluate renal colic. From 2008-2011, 9 pregnant women were referred for evaluation of suspected renal colic caused by an obstructing upper tract stone. All patients underwent MRU with a half Fourier single-shot turbo spin-echo (HASTE) protocol. Medical records and imaging studies were reviewed for demographic and clinical data as well as outcome measures. The mean age of the subjects was 25 years (range 20-34); average gestational age of the fetus was 23 weeks (range 9-36). In all cases, a renal ultrasound was the initial imaging study obtained, with nondiagnostic findings. HASTE MRU detected 4 ureteral stones and 4 cases of physiological hydronephrosis of pregnancy. In one case, interpretation of the MRU was limited as a result of patient motion. Of the patients with obstructing stones, 1 required endourologic management during her pregnancy and 3 were followed conservatively. No adverse events related to MRU occurred. HASTE MRU is an informative imaging study for pregnant women with suspected upper tract stone disease. Information gathered from this study augments that gained from alternative modalities, and aids in medical decision-making. The lack of ionizing radiation exposure, coupled with the capture of detailed anatomic imaging, makes HASTE MRU a particularly useful study in this setting. Copyright © 2012 Elsevier Inc. All rights reserved.

Functional MR imaging of the cervical spinal cord by use of electrical stimulation at LI4 (Hegu).

PubMed

Wang, W D; Kong, K M; Xiao, Y Y; Wang, X J; Liang, B; Qi, W L; Wu, R H

2006-01-01

The purpose is to investigate the cervical spinal cord mapping on electrical stimulation at LI4 (Hegu) by using 'signal enhancement by extravascular water protons' (SEEP)-fMRI, and to establish the response of acupoint-stimulation in spinal cord. Three healthy volunteers were underwent low-frequency electrical stimulation at LI4. Meanwhile, a single-shot fast spin-echo (SSFSE) sequence was used to perform functional MR imaging on a 1.5 T GE Signa MR system. Cord activation was measured both in the sagittal and transverse imaging planes and then analyzed by AFNI (analysis of functional neuroimages) system. In the sagittal view, two subjects had an fMRI response in the cervical spinal cord upon electrical stimulation at LI4. The localizations of the segmental fMRI activation are both at C6 through T1 and C2/3 cervical spinal cord level. In the transverse imaging plane, significant fMRI responses could be measured in the last subjects locating at C6/7 segment, the cross-sectional localization of the activity measured in the spinal cord was most in terms of the ipsilateral posterior direction. It is concluded that the fMRI technique can be used for detecting with activity in the human cervical spinal cord by a single-shot fast spin-echo sequence on a 1.5 T GE clinical system. Investigating the acupoint-stimulation response in the spinal cord using the spinal fMRI will be helpful for the further discussion on the mechanisms of acupuncture to spinal cord diseases.

Improved black-blood imaging using DANTE-SPACE for simultaneous carotid and intracranial vessel wall evaluation.

PubMed

Xie, Yibin; Yang, Qi; Xie, Guoxi; Pang, Jianing; Fan, Zhaoyang; Li, Debiao

2016-06-01

The purpose of this study was to develop a three-dimensional black blood imaging method for simultaneously evaluating the carotid and intracranial arterial vessel walls with high spatial resolution and excellent blood suppression with and without contrast enhancement. The delay alternating with nutation for tailored excitation (DANTE) preparation module was incorporated into three-dimensional variable flip angle turbo spin echo (SPACE) sequence to improve blood signal suppression. Simulations and phantom studies were performed to quantify image contrast variations induced by DANTE. DANTE-SPACE, SPACE, and two-dimensional turbo spin echo were compared for apparent signal-to-noise ratio, contrast-to-noise ratio, and morphometric measurements in 14 healthy subjects. Preliminary clinical validation was performed in six symptomatic patients. Apparent residual luminal blood was observed in five (pre-contrast) and nine (post-contrast) subjects with SPACE and only two (post-contrast) subjects with DANTE-SPACE. DANTE-SPACE showed 31% (pre-contrast) and 100% (post-contrast) improvement in wall-to-blood contrast-to-noise ratio over SPACE. Vessel wall area measured from SPACE was significantly larger than that from DANTE-SPACE due to possible residual blood signal contamination. DANTE-SPACE showed the potential to detect vessel wall dissection and identify plaque components in patients. DANTE-SPACE significantly improved arterial and venous blood suppression compared with SPACE. Simultaneous high-resolution carotid and intracranial vessel wall imaging to potentially identify plaque components was feasible with a scan time under 6 min. Magn Reson Med 75:2286-2294, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Advances in arterial spin labelling MRI methods for measuring perfusion and collateral flow.

PubMed

van Osch, Matthias Jp; Teeuwisse, Wouter M; Chen, Zhensen; Suzuki, Yuriko; Helle, Michael; Schmid, Sophie

2017-01-01

With the publication in 2015 of the consensus statement by the perfusion study group of the International Society for Magnetic Resonance in Medicine (ISMRM) and the EU-COST action 'ASL in dementia' on the implementation of arterial spin labelling MRI (ASL) in a clinical setting, the development of ASL can be considered to have become mature and ready for clinical prime-time. In this review article new developments and remaining issues will be discussed, especially focusing on quantification of ASL as well as on new technological developments of ASL for perfusion imaging and flow territory mapping. Uncertainty of the achieved labelling efficiency in pseudo-continuous ASL (pCASL) as well as the presence of arterial transit time artefacts, can be considered the main remaining challenges for the use of quantitative cerebral blood flow (CBF) values. New developments in ASL centre around time-efficient acquisition of dynamic ASL-images by means of time-encoded pCASL and diversification of information content, for example by combined 4D-angiography with perfusion imaging. Current vessel-encoded and super-selective pCASL-methodology have developed into easily applied flow-territory mapping methods providing relevant clinical information with highly similar information content as digital subtraction angiography (DSA), the current clinical standard. Both approaches seem therefore to be ready for clinical use.

Quantitative 17O imaging towards oxygen consumption study in tumor bearing mice at 7 T.

PubMed

Narazaki, Michiko; Kanazawa, Yoko; Koike, Sachiko; Ando, Koichi; Ikehira, Hiroo

2013-06-01

(17)O magnetic resonance imaging (MRI) using a conventional pulse sequence was explored as a method of quantitative imaging towards regional oxygen consumption rate measurement for tumor evaluation in mice. At 7 T, fast imaging with steady state (FISP) was the best among gradient echo, fast spin echo and FISP for the purpose. The distribution of natural abundance H2(17)O in mice was visualized under spatial resolution of 2.5 × 2.5mm(2) by FISP in 10 min. The signal intensity by FISP showed a linear relationship with (17)O quantity both in phantom and mice. Following the injection of 5% (17)O enriched saline, (17)O re-distribution was monitored in temporal resolution down to 5 sec with an image quality sufficient to distinguish each organ. The image of labeled water produced from inhaled (17)O2 gas was also obtained. The present method provides quantitative (17)O images under sufficient temporal and spatial resolution for the evaluation of oxygen consumption rate in each organ. Experiments using various model compounds of R-OH type clarified that the signal contribution of body constituents other than water in the present in vivo(17)O FISP image was negligible. Copyright © 2013 Elsevier Inc. All rights reserved.

[Renal arterial spin labeling magnetic resonance imaging in normal adults: a study with a 3.0 T scanner].

PubMed

Zhang, Fan; Zhang, Xuelin; Yang, Li; Shen, Jie; Gao, Wei

2013-10-01

To analyze the renal relative blood flow value (rBFV) and image quality in normal adults using single-shot fast spin echo, flow sensitive invention recovery (SSFSE-FAIR) magnetic resonance (MR) sequence and echo planar imaging, and flow sensitive invention recovery (EPI-FAIR) MR sequence, and assess its value for clinical application in routine renal examination. Forty volunteers (25 male and 15 female adults, aged 30 to 62 years) with normal renal function were included in this prospective study. All the subjects underwent 3.0 Tesla MR scanning using 3 MR scan modes, namely breath-holding EPI-FAIR, breath-holding SSFSE-FAIR and free breathing SSFSE-FAIR. SSFSE-FAIR without breath-holding was capable of differentiating the renal cortex and medulla with the corresponding rBFVs of 111.48∓9.23 and 94.98∓3.38, respectively. Breath-holding SSFSE-FAIR and EPI-FAIR failed to distinguish the borders of the renal cortex and medulla. The EPI-FAIR rBFV of mixed cortex and medulla value was 178.50∓17.17 (95%CI: 167.59, 189.41). Breath-holding SSFSE-FAIR and EPI-FAIR can not distinguish the renal cortex and medulla due to a poor spatial resolution but can be used for rough evaluation of renal blood perfusion. Free breathing SSFSE-FAIR with an improved spatial resolution allows evaluation of the status of renal perfusion of the cortex and medulla.

RARE/Turbo Spin Echo Imaging with Simultaneous MultiSlice Wave-CAIPI

PubMed Central

Eichner, Cornelius; Bhat, Himanshu; Grant, P. Ellen; Wald, Lawrence L.; Setsompop, Kawin

2014-01-01

Purpose To enable highly accelerated RARE/Turbo Spin Echo (TSE) imaging using Simultaneous MultiSlice (SMS) Wave-CAIPI acquisition with reduced g-factor penalty. Methods SMS Wave-CAIPI incurs slice shifts across simultaneously excited slices while playing sinusoidal gradient waveforms during the readout of each encoding line. This results in an efficient k-space coverage that spreads aliasing in all three dimensions to fully harness the encoding power of coil sensitivities. The novel MultiPINS radiofrequency (RF) pulses dramatically reduce the power deposition of multiband (MB) refocusing pulse, thus allowing high MB factors within the Specific Absorption Rate (SAR) limit. Results Wave-CAIPI acquisition with MultiPINS permits whole brain coverage with 1 mm isotropic resolution in 70 seconds at effective MB factor 13, with maximum and average g-factor penalties of gmax=1.34 and gavg=1.12, and without √R penalty. With blipped-CAIPI, the g-factor performance was degraded to gmax=3.24 and gavg=1.42; a 2.4-fold increase in gmax relative to Wave-CAIPI. At this MB factor, the SAR of the MultiBand and PINS pulses are 4.2 and 1.9 times that of the MultiPINS pulse, while the peak RF power are 19.4 and 3.9 times higher. Conclusion Combination of the two technologies, Wave-CAIPI and MultiPINS pulse, enables highly accelerated RARE/TSE imaging with low SNR penalty at reduced SAR. PMID:25640187

[Single shot fast spin echo sequence MRI cholangiopancreatography].

PubMed

Lefèvre, F; Crouzet, P; Gaucher, H; Chapuis, F; Béot, S; Boccaccini, H; Bazin, C; Régent, D

1998-05-01

To assess the value of single shot fast spin echo MR sequence (SS-FSE) in the morphological analysis of the biliary tree and pancreatic ducts and to compare its accuracy with other imaging methods. 95 consecutive patients referred for clinical and/or biological suspicion of biliary obstruction were explored with MR cholangiopancreatography (MRCP). All patients were explored with a Signa 1.5 T GE MR unit, with High Gradient Field Strength and Torso Phased Array Coil. Biliary ducts were explored with SS-FSE sequence, coronal and oblique coronal 20 mm thick slices on a 256 x 256 matrix. Total acquisition time was 1 second. Native pictures were reviewed by two radiologists blinded to clinical information. In case of disagreement, a third radiologist's judgement was requested. In 88 cases, MRCP results were compared with direct biligraphy methods. In all cases, MRCP produced high quality images without MIP or other post-processing methods. For detection of biliary tree distensions, the concordance value of MRCP was over 91% (Kappa 0.82). For detection of biliary tree and/or pancreatic duct obstruction, MR sensitivity was 100% and specificity 91%. The overall diagnostic concordance value of MRCP was > or = 93%. Difficulties in MRCP were caused by functional diseases or benign stenosis. MRCP accurately diagnosed all lithiasic obstructions starting from a stone size of 3 mm. MRCP produces fastly high-quality images. As it is totally safe, it can be proposed as a first intention method in biliopancreatic duct explorations.

Use of pattern recognition for unaliasing simultaneously acquired slices in simultaneous multislice MR fingerprinting.

PubMed

Jiang, Yun; Ma, Dan; Bhat, Himanshu; Ye, Huihui; Cauley, Stephen F; Wald, Lawrence L; Setsompop, Kawin; Griswold, Mark A

2017-11-01

The purpose of this study is to accelerate an MR fingerprinting (MRF) acquisition by using a simultaneous multislice method. A multiband radiofrequency (RF) pulse was designed to excite two slices with different flip angles and phases. The signals of two slices were driven to be as orthogonal as possible. The mixed and undersampled MRF signal was matched to two dictionaries to retrieve T 1 and T 2 maps of each slice. Quantitative results from the proposed method were validated with the gold-standard spin echo methods in a phantom. T 1 and T 2 maps of in vivo human brain from two simultaneously acquired slices were also compared to the results of fast imaging with steady-state precession based MRF method (MRF-FISP) with a single-band RF excitation. The phantom results showed that the simultaneous multislice imaging MRF-FISP method quantified the relaxation properties accurately compared to the gold-standard spin echo methods. T 1 and T 2 values of in vivo brain from the proposed method also matched the results from the normal MRF-FISP acquisition. T 1 and T 2 values can be quantified at a multiband acceleration factor of two using our proposed acquisition even in a single-channel receive coil. Further acceleration could be achieved by combining this method with parallel imaging or iterative reconstruction. Magn Reson Med 78:1870-1876, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

In vivo imaging of cancer cell size and cellularity using temporal diffusion spectroscopy.

PubMed

Jiang, Xiaoyu; Li, Hua; Xie, Jingping; McKinley, Eliot T; Zhao, Ping; Gore, John C; Xu, Junzhong

2017-07-01

A temporal diffusion MRI spectroscopy based approach has been developed to quantify cancer cell size and density in vivo. A novel imaging microstructural parameters using limited spectrally edited diffusion (IMPULSED) method selects a specific limited diffusion spectral window for an accurate quantification of cell sizes ranging from 10 to 20 μm in common solid tumors. In practice, it is achieved by a combination of a single long diffusion time pulsed gradient spin echo (PGSE) and three low-frequency oscillating gradient spin echo (OGSE) acquisitions. To validate our approach, hematoxylin and eosin staining and immunostaining of cell membranes, in concert with whole slide imaging, were used to visualize nuclei and cell boundaries, and hence, enabled accurate estimates of cell size and cellularity. Based on a two compartment model (incorporating intra- and extracellular spaces), accurate estimates of cell sizes were obtained in vivo for three types of human colon cancers. The IMPULSED-derived apparent cellularities showed a stronger correlation (r = 0.81; P < 0.0001) with histology-derived cellularities than conventional ADCs (r = -0.69; P < 0.03). The IMPULSED approach samples a specific region of temporal diffusion spectra with enhanced sensitivity to length scales of 10-20 μm, and enables measurements of cell sizes and cellularities in solid tumors in vivo. Magn Reson Med 78:156-164, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Spectroscopic techniques (Mössbauer spectrometry, NMR, ESR,…) as tools to resolve doubtful NMR images: Study of the craniopharyngioma tumor

NASA Astrophysics Data System (ADS)

Rimbert, J. N.; Dumas, F.; Lafargue, C.; Kellershohn, C.; Brunelle, F.; Lallemand, D.

1990-07-01

Craniopharyngioma, an intracranial tumor, exhibits hyperintensity in the Spin-Echo-T2-NMR image and a hyposignal in the SE-T1-image. However, in some cases (15-20% cases), hypersignals are seen in both SE-T1 and T2-MRI. Using spectroscopic techniques, Mössbauer spectrometry in particular, we have demonstrated that the T1 hypersignal is due to ferritin, dissolved in the cystic liquid, after tumor cell lysis, in the course of time. Other possible reasons inducing a shortening of the T1 relaxation time (presence of lipids, intratumoral hemorrhage) have been rejected.

Bone marrow edema pattern in advanced hip osteoarthritis: quantitative assessment with magnetic resonance imaging and correlation with clinical examination, radiographic findings, and histopathology.

PubMed

Taljanovic, Mihra S; Graham, Anna R; Benjamin, James B; Gmitro, Arthur F; Krupinski, Elizabeth A; Schwartz, Stephanie A; Hunter, Tim B; Resnick, Donald L

2008-05-01

To correlate the amount of bone marrow edema (BME) calculated by magnetic resonance imaging(MRI) with clinical findings, histopathology, and radiographic findings, in patients with advanced hip osteoarthritis(OA). The study was approved by The Institutional Human Subject Protection Committee. Coronal MRI of hips was acquired in 19 patients who underwent hip replacement. A spin echo (SE) sequence with four echoes and separate fast spin echo (FSE) proton density (PD)-weighted SE sequences of fat (F) and water (W) were acquired with water and fat suppression, respectively. T2 and water:fat ratio calculations were made for the outlined regions of interest. The calculated MRI values were correlated with the clinical, radiographic, and histopathologic findings. Analyses of variance were done on the MRI data for W/(W + F) and for T2 values (total and focal values) for the symptomatic and contralateral hips. The values were significantly higher in the study group. Statistically significant correlations were found between pain and total W/(W + F), pain and focal T2 values, and the number of microfractures and calculated BME for the focal W/(W + F) in the proximal femora. Statistically significant correlations were found between the radiographic findings and MRI values for total W/(W + F), focal W/(W + F) and focal T2 and among the radiographic findings, pain, and hip movement. On histopathology, only a small amount of BME was seen in eight proximal femora. The amount of BME in the OA hip, as measured by MRI, correlates with the severity of pain, radiographic findings, and number of microfractures.

Concepts and Engineering Aspects of a Neutron Resonance Spin-Echo Spectrometer for the National Institute of Standards and Technology Center for Neutron Research

PubMed Central

Cook, Jeremy C.

2014-01-01

Following a brief introduction, the Neutron Resonance Spin-Echo (NRSE) principle is discussed classically in Sec. 2. In Sec. 3, two idealized 4-coil NRSE spectrometers are discussed (one using single π-flipper coil units and one using paired “bootstrap” coils); some idealized (exact π-flip) expressions are given for the spin-echo signal and some theoretical limitations are discussed. A more quantum mechanical discussion of NRSE is presented in Sec. 4 and additional theory related to the spin-echo signal, including wavelength-dependence, is given is Sec. 5. Factors affecting the instrumental resolution are discussed in Sec. 6. In Sec. 7, a variety of engineering issues are assessed in the context of challenging performance goals for a NIST Center for Neutron Research (NCNR) NRSE spectrometer. In Sec. 8, some Monte Carlo simulations are presented that examine the combined influences of spectrometer imperfections on the NRSE signal. These are compared with analytical predictions developed in previous sections. In Sec. 9, possible alternatives for a NCNR NRSE spectrometer configuration are discussed together with a preliminary assessment of the spectrometer neutron guide requirements. A summary of some of the useful formulas is given in Appendix A. PMID:26601027

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, B; Yu, H; Jara, H

Purpose: To compare enhanced Laws texture derived from parametric proton density (PD) maps to other MRI-based surrogate markers (T2, PD, ADC) in assessing degrees of liver fibrosis in a murine model of hepatic fibrosis using 11.7T scanner. Methods: This animal study was IACUC approved. Fourteen mice were divided into control (n=1) and experimental (n=13). The latter were fed a DDC-supplemented diet to induce hepatic fibrosis. Liver specimens were imaged using an 11.7T scanner; the parametric PD, T2, and ADC maps were generated from spin-echo pulsed field gradient and multi-echo spin-echo acquisitions. Enhanced Laws texture analysis was applied to the PDmore » maps: first, hepatic blood vessels and liver margins were segmented/removed using an automated dual-clustering algorithm; secondly, an optimal thresholding algorithm was applied to reduce the partial volume artifact; next, mean and stdev were corrected to minimize grayscale variation across images; finally, Laws texture was extracted. Degrees of fibrosis was assessed by an experienced pathologist and digital image analysis (%Area Fibrosis). Scatterplots comparing enhanced Laws texture, T2, PD, and ADC values to degrees of fibrosis were generated and correlation coefficients were calculated. Unenhanced Laws texture was also compared to assess the effectiveness of the proposed enhancements. Results: Hepatic fibrosis and the enhanced Laws texture were strongly correlated with higher %Area Fibrosis associated with higher Laws texture (r=0.89). Only a moderate correlation was detected between %Area Fibrosis and unenhanced Laws texture (r=0.70). Strong correlation also existed between ADC and %Area Fibrosis (r=0.86). Moderate correlations were seen between %Area Fibrosis and PD (r=0.65) and T2 (r=0.66). Conclusions: Higher degrees of hepatic fibrosis are associated with increased Laws texture. The proposed enhancements improve the accuracy of Laws texture. Enhanced Laws texture features are more accurate than PD and T2 in assessing fibrosis, and can potentially serve as an accurate surrogate marker for hepatic fibrosis.« less

Magnetic resonance imaging in cadaver dogs with metallic vertebral implants at 3 Tesla: evaluation of the WARP-turbo spin echo sequence.

PubMed

Griffin, John F; Archambault, Nicholas S; Mankin, Joseph M; Wall, Corey R; Thompson, James A; Padua, Abraham; Purdy, David; Kerwin, Sharon C

2013-11-15

Laboratory investigation, ex vivo. Postoperative complications are common after spinal implantation procedures, and magnetic resonance imaging (MRI) would be the ideal modality to image these patients. Unfortunately, the implants cause artifacts that can render MRI nondiagnostic. The WARP-turbo spin echo (TSE) sequence has been developed to mitigate artifacts caused by metal. The objective of this investigation was to evaluate the performance of the WARP-TSE sequence in canine cadaver specimens after implantation with metallic vertebral implants. Magnetic field strength, implant type, and MRI acquisition technique all play a role in the severity of susceptibility artifacts. The WARP-TSE sequence uses increased bandwidth, view angle tilting, and SEMAC (slice-encoding metal artifact correction) to correct for susceptibility artifact. The WARP-TSE technique has outperformed conventional techniques in patients, after total hip arthroplasty. However, published reports of its application in subjects with vertebral column implants are lacking. Ex vivo anterior stabilization of the atlantoaxial joint was performed on 6 adult small breed (<8 kg) cadaver dogs using stainless steel screws and polymethylmethacrylate. Axial and sagittal T2-weighted and short tau inversion recovery MRI was performed using conventional pulse sequences and WARP-TSE sequences at 3 T. Images were assessed qualitatively and quantitatively. Images made with the WARP-TSE sequence had smaller susceptibility artifacts and superior spinal cord margin depiction. WARP-TSE sequences reduced the length over which susceptibility artifacts caused spinal cord margin depiction interference by 24.9% to 71.5% with scan times of approximately 12 to 16 minutes. The WARP-TSE sequence is a viable option for evaluating the vertebral column after implantation with stainless steel implants. N/A.

Measurement of ciliary beat frequency using Doppler optical coherence tomography.

PubMed

Lemieux, Bryan T; Chen, Jason J; Jing, Joseph; Chen, Zhongping; Wong, Brian J F

2015-11-01

Measuring ciliary beat frequency (CBF) is a technical challenge and difficult to perform in vivo. Doppler optical coherence tomography (D-OCT) is a mesoscopic noncontact imaging modality that provides high-resolution tomographic images and detects micromotion simultaneously in living tissues. In this work we used D-OCT to measure CBF in ex vivo tissue as the first step toward translating this technology to clinical use. Fresh ex vivo samples of rabbit tracheal mucosa were imaged using both D-OCT and phase-contrast microscopy (n = 5). The D-OCT system was designed and built to specification in our lab (1310-nm swept source vertical-cavity surface-emitting laser [VCSEL], 6-μm axial resolution). The samples were placed in culture and incubated at 37°C. A fast Fourier transform was performed on the D-OCT signal recorded on the surface of the samples to gauge CBF. High-speed digital video of the epithelium recorded via phase-contrast microscopy was analyzed to confirm the CBF measurements. The D-OCT system detected Doppler signal at the epithelial layer of ex vivo rabbit tracheal samples suggestive of ciliary motion. CBF was measured at 9.36 ± 1.22 Hz using D-OCT and 9.08 ± 0.48 Hz using phase-contrast microscopy. No significant differences were found between the 2 methods (p > 0.05). D-OCT allows for the quantitative measurement of CBF without the need to resolve individual cilia. Furthermore, D-OCT technology can be incorporated into endoscopic platforms that allow clinicians to readily measure CBF in the office and provide a direct measurement of mucosal health. © 2015 ARS-AAOA, LLC.