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

Fast T2*-weighted MRI of the prostate at 3 Tesla.

PubMed

Hardman, Rulon L; El-Merhi, Fadi; Jung, Adam J; Ware, Steve; Thompson, Ian M; Friel, Harry T; Peng, Qi

2011-04-01

To describe a rapid T2*-weighted (T2*W), three-dimensional (3D) echo planar imaging (EPI) sequence and its application in mapping local magnetic susceptibility variations in 3 Tesla (T) prostate MRI. To compare the sensitivity of T2*W EPI with routinely used T1-weighted turbo-spin echo sequence (T1W TSE) in detecting hemorrhage and the implications on sequences sensitive to field inhomogeneities such as MR spectroscopy (MRS). B(0) susceptibility weighted mapping was performed using a 3D EPI sequence featuring a 2D spatial excitation pulse with gradients of spiral k-space trajectory. A series of 11 subjects were imaged using 3T MRI and combination endorectal (ER) and six-channel phased array cardiac coils. T1W TSE and T2*W EPI sequences were analyzed quantitatively for hemorrhage contrast. Point resolved spectroscopy (PRESS MRS) was performed and data quality was analyzed. Two types of susceptibility variation were identified: hemorrhagic and nonhemorrhagic T2*W-positive areas. Post-biopsy hemorrhage lesions showed on average five times greater contrast on the T2*W images than T1W TSE images. Six nonhemorrhage regions of severe susceptibility artifact were apparent on the T2*W images that were not seen on standard T1W or T2W images. All nonhemorrhagic susceptibility artifact regions demonstrated compromised spectral quality on 3D MRS. The fast T2*W EPI sequence identifies hemorrhagic and nonhemorrhagic areas of susceptibility variation that may be helpful in prostate MRI planning at 3.0T. Copyright © 2011 Wiley-Liss, Inc.

[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.

Weak beacon detection for air-to-ground optical wireless link establishment.

PubMed

Han, Yaoqiang; Dang, Anhong; Tang, Junxiong; Guo, Hong

2010-02-01

In an air-to-ground free-space optical communication system, strong background interference seriously affects the beacon detection, which makes it difficult to establish the optical link. In this paper, we propose a correlation beacon detection scheme under strong background interference conditions. As opposed to traditional beacon detection schemes, the beacon is modulated by an m-sequence at the transmitting terminal with a digital differential matched filter (DDMF) array introduced at the receiving end to detect the modulated beacon. This scheme is capable of suppressing both strong interference and noise by correlation reception of the received image sequence. In addition, the DDMF array enables each pixel of the image sensor to have its own DDMF of the same structure to process its received image sequence in parallel, thus it makes fast beacon detection possible. Theoretical analysis and an outdoor experiment have been demonstrated and show that the proposed scheme can realize fast and effective beacon detection under strong background interference conditions. Consequently, the required beacon transmission power can also be reduced dramatically.

Fast CSF MRI for brain segmentation; Cross-validation by comparison with 3D T1-based brain segmentation methods

PubMed Central

de Bresser, Jeroen; Hendrikse, Jeroen; Siero, Jeroen C. W.; Petersen, Esben T.; De Vis, Jill B.

2018-01-01

Objective In previous work we have developed a fast sequence that focusses on cerebrospinal fluid (CSF) based on the long T2 of CSF. By processing the data obtained with this CSF MRI sequence, brain parenchymal volume (BPV) and intracranial volume (ICV) can be automatically obtained. The aim of this study was to assess the precision of the BPV and ICV measurements of the CSF MRI sequence and to validate the CSF MRI sequence by comparison with 3D T1-based brain segmentation methods. Materials and methods Ten healthy volunteers (2 females; median age 28 years) were scanned (3T MRI) twice with repositioning in between. The scan protocol consisted of a low resolution (LR) CSF sequence (0:57min), a high resolution (HR) CSF sequence (3:21min) and a 3D T1-weighted sequence (6:47min). Data of the HR 3D-T1-weighted images were downsampled to obtain LR T1-weighted images (reconstructed imaging time: 1:59 min). Data of the CSF MRI sequences was automatically segmented using in-house software. The 3D T1-weighted images were segmented using FSL (5.0), SPM12 and FreeSurfer (5.3.0). Results The mean absolute differences for BPV and ICV between the first and second scan for CSF LR (BPV/ICV: 12±9/7±4cc) and CSF HR (5±5/4±2cc) were comparable to FSL HR (9±11/19±23cc), FSL LR (7±4, 6±5cc), FreeSurfer HR (5±3/14±8cc), FreeSurfer LR (9±8, 12±10cc), and SPM HR (5±3/4±7cc), and SPM LR (5±4, 5±3cc). The correlation between the measured volumes of the CSF sequences and that measured by FSL, FreeSurfer and SPM HR and LR was very good (all Pearson’s correlation coefficients >0.83, R2 .67–.97). The results from the downsampled data and the high-resolution data were similar. Conclusion Both CSF MRI sequences have a precision comparable to, and a very good correlation with established 3D T1-based automated segmentations methods for the segmentation of BPV and ICV. However, the short imaging time of the fast CSF MRI sequence is superior to the 3D T1 sequence on which segmentation with established methods is performed. PMID:29672584

Fast CSF MRI for brain segmentation; Cross-validation by comparison with 3D T1-based brain segmentation methods.

PubMed

van der Kleij, Lisa A; de Bresser, Jeroen; Hendrikse, Jeroen; Siero, Jeroen C W; Petersen, Esben T; De Vis, Jill B

2018-01-01

In previous work we have developed a fast sequence that focusses on cerebrospinal fluid (CSF) based on the long T2 of CSF. By processing the data obtained with this CSF MRI sequence, brain parenchymal volume (BPV) and intracranial volume (ICV) can be automatically obtained. The aim of this study was to assess the precision of the BPV and ICV measurements of the CSF MRI sequence and to validate the CSF MRI sequence by comparison with 3D T1-based brain segmentation methods. Ten healthy volunteers (2 females; median age 28 years) were scanned (3T MRI) twice with repositioning in between. The scan protocol consisted of a low resolution (LR) CSF sequence (0:57min), a high resolution (HR) CSF sequence (3:21min) and a 3D T1-weighted sequence (6:47min). Data of the HR 3D-T1-weighted images were downsampled to obtain LR T1-weighted images (reconstructed imaging time: 1:59 min). Data of the CSF MRI sequences was automatically segmented using in-house software. The 3D T1-weighted images were segmented using FSL (5.0), SPM12 and FreeSurfer (5.3.0). The mean absolute differences for BPV and ICV between the first and second scan for CSF LR (BPV/ICV: 12±9/7±4cc) and CSF HR (5±5/4±2cc) were comparable to FSL HR (9±11/19±23cc), FSL LR (7±4, 6±5cc), FreeSurfer HR (5±3/14±8cc), FreeSurfer LR (9±8, 12±10cc), and SPM HR (5±3/4±7cc), and SPM LR (5±4, 5±3cc). The correlation between the measured volumes of the CSF sequences and that measured by FSL, FreeSurfer and SPM HR and LR was very good (all Pearson's correlation coefficients >0.83, R2 .67-.97). The results from the downsampled data and the high-resolution data were similar. Both CSF MRI sequences have a precision comparable to, and a very good correlation with established 3D T1-based automated segmentations methods for the segmentation of BPV and ICV. However, the short imaging time of the fast CSF MRI sequence is superior to the 3D T1 sequence on which segmentation with established methods is performed.

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

Assessment of geometrical accuracy of magnetic resonance images for radiation therapy of lung cancers

PubMed Central

Liu, H. H.; Olsson, L. E.; Jackson, E. F.

2003-01-01

The purpose of this research was to investigate the geometrical accuracy of magnetic resonance (MR) images used in the radiation therapy treatment planning for lung cancer. In this study, the capability of MR imaging to acquire dynamic two‐dimensional images was explored to access the motion of lung tumors. Due to a number of factors, including the use of a large field‐of‐view for the thorax, MR images are particularly subject to geometrical distortions caused by the inhomogeneity and gradient nonlinearity of the magnetic field. To quantify such distortions, we constructed a phantom, which approximated the dimensions of the upper thorax and included two air cavities. Evenly spaced vials containing contrast agent could be held in three directions with their cross‐sections in the coronal, sagittal, and axial planes, respectively, within the air cavities. MR images of the phantom were acquired using fast spin echo (FSE) and fast gradient echo (fGRE) sequences. The positions of the vials according to their centers of mass were measured from the MR images and registered to the corresponding computed tomography images for comparison. Results showed the fGRE sequence exhibited no errors >2.0 mm in the sagittal and coronal planes, whereas the FSE sequence produced images with errors between 2.0 and 4.0 mm along the phantom's perimeter in the axial plane. On the basis of these results, the fGRE sequence was considered to be clinically acceptable in acquiring images in all sagittal and coronal planes tested. However, the spatial accuracy in periphery of the axial FSE images exceeded the acceptable criteria for the acquisition parameters used in this study. PACS number(s): 87.57.–s, 87.61.–c PMID:14604425

[Laparoscopic and general surgery guided by open interventional magnetic resonance].

PubMed

Lauro, A; Gould, S W T; Cirocchi, R; Giustozzi, G; Darzi, A

2004-10-01

Interventional magnetic resonance (IMR) machines have produced unique opportunity for image-guided surgery. The open configuration design and fast pulse sequence allow virtual real time intraoperative scanning to monitor the progress of a procedure, with new images produced every 1.5 sec. This may give greater appreciation of anatomy, especially deep to the 2-dimensional laparoscopic image, and hence increase safety, reduce procedure magnitude and increase confidence in tumour resection surgery. The aim of this paper was to investigate the feasibility of performing IMR-image-guided general surgery, especially in neoplastic and laparoscopic field, reporting a single center -- St. Mary's Hospital (London, UK) -- experience. Procedures were carried out in a Signa 0.5 T General Elettric SP10 Interventional MR (General Electric Medical Systems, Milwaukee, WI, USA) with magnet-compatible instruments (titanium alloy instruments, plastic retractors and ultrasonic driven scalpel) and under general anesthesia. There were performed 10 excision biopsies of palpable benign breast tumors (on female patients), 3 excisions of skin sarcoma (dermatofibrosarcoma protuberans), 1 right hemicolectomy and 2 laparoscopic cholecystectomies. The breast lesions were localized with pre- and postcontrast (intravenous gadolinium DPTA) sagittal and axial fast multiplanar spoiled gradient recalled conventional Signa sequences; preoperative real time fast gradient recalled sequences were also obtained using the flashpoint tracking device. During right hemicolectomy intraoperative single shot fast spin echo (SSFSE) and fast spoiled gradient recalled (FSPGR) imaging of right colon were performed after installation of 150 cc of water or 1% gadolinium solution, respectively, through a Foley catheter; imaging was also obtained in an attempt to identify mesenteric lymph nodes intraoperatively. Concerning laparoscopic procedures, magnetic devices (insufflator, light source) were positioned outside scan room, the tubing and light head being passed through penetration panels. Intraoperative MR-cholangiography was performed using fast spin echo (SSFSE) techniques with minimal intensity projection 3-dimensional reconstruction. About skin sarcomas, 2 of them were skin recurrences of previously surgically treated sarcomas (all of them received preoperative biopsy) and the extent of the lesion was then determined using short tau inversion recovery (STIR) sequence. The skin was closed in each case without need for any plastic reconstruction. The breast lesions were visualized with both Signa and real-time imaging and all enhanced with contrast: 2 (20%) were visualized only after contrast enhancement; intraoperative real time imaging clearly demonstrated a resection margin in all cases. Maximum dimensions of breast specimens (range 8-50 mm, median 24.5 mm) were not significantly different from those measured by Signa (p>0.17, Student's paired t-test) or real time images (p>0.4): also there was no significant difference in lesion size between Signa and real time images (p>0.25). All postprocedure scans clearly demonstrated complete excision. The extent of the tumor at MR imaging was greater in each case than suggested by clinical examination. Adequate resection margins were planned using STIR sequences. Histological examination confirmed clear surgical margins of at least 1 cm in each case. During right hemicolectomy, both intraoperative SSFSE and FSPGR contrast imaging revealed the lesion and details of the colonic surface; imaging of the lymph node draining right colon was only partially successful, due to movement artifact. Concerning laparoscopic procedures, both FSE and SSFSE techniques produced reasonable images of the gallbladder and intrahepatic ducts, but the FSE imaging was of poor quality due to respiration artifact; however, SSFSE allowed visualization of the gallbladder and part of the common bile duct. About skin sarcomas, the extent of the tumor at MR imaging was greater in each case than suggested by clinical examination and in each case the complete tumor excision was confirmed. Histological examination confirmed clear surgical margins of at least 1 cm in each case. Intraoperative MR scanning reliably identifies palpable breast tumours and skin sarcomas and is sufficiently accurate to guide their surgical excision. Further work may be done to develop laparoscopic and open abdominal surgery as well.

Fetal intracranial hemorrhage. Imaging by ultrasound and magnetic resonance imaging.

PubMed

Kirkinen, P; Partanen, K; Ryynänen, M; Ordén, M R

1997-08-01

To describe the magnetic resonance imaging (MRI) findings associated with fetal intracranial hemorrhage and to compare them with ultrasound findings. In four pregnancies complicated by fetal intracranial hemorrhage, fetal imaging was carried out using T2-weighted fast spin echo sequences and T1-weighted fast low angle shot imaging sequences and by transabdominal ultrasonography. An antepartum diagnosis of hemorrhage was made by ultrasound in one case and by MRI in two. Retrospectively, the hemorrhagic area could be identified from the MRI images in an additional two cases and from the ultrasound images in one case. In the cases of intraventricular hemorrhage, the MRI signal intensity in the T1-weighted images was increased in the hemorrhagic area as compared to the contralateral ventricle and brain parenchyma. In a case with subdural hemorrhage, T2-weighted MRI signals from the hemorrhagic area changed from low-to high-intensity signals during four weeks of follow-up. Better imaging of the intracranial anatomy was possible by MRI than by transabdominal ultrasonography. MRI can be used for imaging and dating fetal intracranial hemorrhages. Variable ultrasound and MRI findings are associated with this complication, depending on the age and location of the hemorrhage.

1981 Image II Conference Proceedings.

DTIC Science & Technology

1981-11-01

rapid motion of terrain detail across the display requires fast display processors. Other difficulties are perceptual: the visual displays must convey...has been a continuing effort by Vought in the last decade. Early systems were restricted by the unavailability of video bulk storage with fast random...each photograph. The calculations aided in the proper sequencing of the scanned scenes on the tape recorder and eventually facilitated fast random

Prevalence of pathologic findings in asymptomatic knees of marathon runners before and after a competition in comparison with physically active subjects-a 3.0 T magnetic resonance imaging study.

PubMed

Stahl, Robert; Luke, Anthony; Ma, C Benjamin; Krug, Roland; Steinbach, Lynne; Majumdar, Sharmila; Link, Thomas M

2008-07-01

To determine the prevalence of pathologic findings in asymptomatic knees of marathon runners before and after a competition in comparison with physically active subjects. To compare the diagnostic performance of cartilage-dedicated magnetic resonance imaging (MRI) sequences at 3.0 T. Ten marathon runners underwent 3.0 T MRI 2-3 days before and after competition. Twelve physically active asymptomatic subjects not performing long-distance running were examined as controls. Pathologic condition was assessed with the whole-organ magnetic resonance imaging score (WORMS). Cartilage abnormalities and bone marrow edema pattern (BMEP) were quantified. Visualization of cartilage pathology was assessed with intermediate-weighted fast spin-echo (IM-w FSE), fast imaging employing steady-state acquisition (FIESTA) and T1-weighted three-dimensional (3D) high-spatial-resolution volumetric fat-suppressed spoiled gradient-echo (SPGR) MRI sequences. Eight of ten marathon runners and 7/12 controls showed knee abnormality. Slightly more and larger cartilage abnormalities, and BMEP, in marathon runners yielded higher but not significantly different WORMS (P > 0.05) than in controls. Running a single marathon did not alter MR findings substantially. Cartilage abnormalities were best visualized with IM-w FSE images (P < 0.05). A high prevalence of knee abnormalities was found in marathon runners and also in active subjects participating in other recreational sports. IM-w FSE sequences delineated more cartilage MR imaging abnormalities than did FIESTA and SPGR sequences.

A standardized evaluation of artefacts from metallic compounds during fast MR imaging

PubMed Central

Murakami, Shumei; Kataoka, Miyoshi; Kakimoto, Naoya; Shimamoto, Hiroaki; Kreiborg, Sven

2016-01-01

Objectives: Metallic compounds present in the oral and maxillofacial regions (OMRs) cause large artefacts during MR scanning. We quantitatively assessed these artefacts embedded within a phantom according to standards set by the American Society for Testing and Materials (ASTM). Methods: Seven metallic dental materials (each of which was a 10-mm3 cube embedded within a phantom) were scanned [i.e. aluminium (Al), silver alloy (Ag), type IV gold alloy (Au), gold–palladium–silver alloy (Au-Pd-Ag), titanium (Ti), nickel–chromium alloy (NC) and cobalt–chromium alloy (CC)] and compared with a reference image. Sequences included gradient echo (GRE), fast spin echo (FSE), gradient recalled acquisition in steady state (GRASS), a spoiled GRASS (SPGR), a fast SPGR (FSPGR), fast imaging employing steady state (FIESTA) and echo planar imaging (EPI; axial/sagittal planes). Artefact areas were determined according to the ASTM-F2119 standard, and artefact volumes were assessed using OsiriX MD software (Pixmeo, Geneva, Switzerland). Results: Tukey–Kramer post hoc tests were used for statistical comparisons. For most materials, scanning sequences eliciting artefact volumes in the following (ascending) order FSE-T1/FSE-T2 < FSPGR/SPGR < GRASS/GRE < FIESTA < EPI. For all scanning sequences, artefact volumes containing Au, Al, Ag and Au-Pd-Ag were significantly smaller than other materials (in which artefact volume size increased, respectively, from Ti < NC < CC). The artefact-specific shape (elicited by the cubic sample) depended on the scanning plane (i.e. a circular pattern for the axial plane and a “clover-like” pattern for the sagittal plane). Conclusions: The availability of standardized information on artefact size and configuration during MRI will enhance diagnosis when faced with metallic compounds in the OMR. PMID:27459058

Spatiotemporal attention operator using isotropic contrast and regional homogeneity

NASA Astrophysics Data System (ADS)

Palenichka, Roman; Lakhssassi, Ahmed; Zaremba, Marek

2011-04-01

A multiscale operator for spatiotemporal isotropic attention is proposed to reliably extract attention points during image sequence analysis. Its consecutive local maxima indicate attention points as the centers of image fragments of variable size with high intensity contrast, region homogeneity, regional shape saliency, and temporal change presence. The scale-adaptive estimation of temporal change (motion) and its aggregation with the regional shape saliency contribute to the accurate determination of attention points in image sequences. Multilocation descriptors of an image sequence are extracted at the attention points in the form of a set of multidimensional descriptor vectors. A fast recursive implementation is also proposed to make the operator's computational complexity independent from the spatial scale size, which is the window size in the spatial averaging filter. Experiments on the accuracy of attention-point detection have proved the operator consistency and its high potential for multiscale feature extraction from image sequences.

Design and development of the coaxial scanner as a compact high-performance thermal imager

NASA Astrophysics Data System (ADS)

Lettington, Alan H.

1994-09-01

This paper describes the original requirement of a light weight, high performance, low cost thermal imager which resulted in the design of the novel coaxial scanner. The early form of imager used a dedicated display to match the original cyclic scan sequence. With the advent of fast digital scan converters and the desire to use standard TV monitors the imager was redesigned and new TV compatible scan sequences devised. A version of this scanner is currently being manufactured by GEC Marconi Avionics, UK, and the paper concludes with examples of its application.

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.

Comparison of MR imaging sequences for liver and head and neck interventions: is there a single optimal sequence for all purposes?

PubMed

Boll, Daniel T; Lewin, Jonathan S; Duerk, Jeffrey L; Aschoff, Andrik J; Merkle, Elmar M

2004-05-01

To compare the appropriate pulse sequences for interventional device guidance during magnetic resonance (MR) imaging at 0.2 T and to evaluate the dependence of sequence selection on the anatomic region of the procedure. Using a C-arm 0.2 T system, four interventional MR sequences were applied in 23 liver cases and during MR-guided neck interventions in 13 patients. The imaging protocol consisted of: multislice turbo spin echo (TSE) T2w, sequential-slice fast imaging with steady precession (FISP), a time-reversed version of FISP (PSIF), and FISP with balanced gradients in all spatial directions (True-FISP) sequences. Vessel conspicuity was rated and contrast-to-noise ratio (CNR) was calculated for each sequence and a differential receiver operating characteristic was performed. Liver findings were detected in 96% using the TSE sequence. PSIF, FISP, and True-FISP imaging showed lesions in 91%, 61%, and 65%, respectively. The TSE sequence offered the best CNR, followed by PSIF imaging. Differential receiver operating characteristic analysis also rated TSE and PSIF to be the superior sequences. Lesions in the head and neck were detected in all cases by TSE and FISP, in 92% using True-FISP, and in 84% using PSIF. True-FISP offered the best CNR, followed by TSE imaging. Vessels appeared bright on FISP and True-FISP imaging and dark on the other sequences. In interventional MR imaging, no single sequence fits all purposes. Image guidance for interventional MR during liver procedures is best achieved by PSIF or TSE, whereas biopsies in the head and neck are best performed using FISP or True-FISP sequences.

Registration of retinal sequences from new video-ophthalmoscopic camera.

PubMed

Kolar, Radim; Tornow, Ralf P; Odstrcilik, Jan; Liberdova, Ivana

2016-05-20

Analysis of fast temporal changes on retinas has become an important part of diagnostic video-ophthalmology. It enables investigation of the hemodynamic processes in retinal tissue, e.g. blood-vessel diameter changes as a result of blood-pressure variation, spontaneous venous pulsation influenced by intracranial-intraocular pressure difference, blood-volume changes as a result of changes in light reflection from retinal tissue, and blood flow using laser speckle contrast imaging. For such applications, image registration of the recorded sequence must be performed. Here we use a new non-mydriatic video-ophthalmoscope for simple and fast acquisition of low SNR retinal sequences. We introduce a novel, two-step approach for fast image registration. The phase correlation in the first stage removes large eye movements. Lucas-Kanade tracking in the second stage removes small eye movements. We propose robust adaptive selection of the tracking points, which is the most important part of tracking-based approaches. We also describe a method for quantitative evaluation of the registration results, based on vascular tree intensity profiles. The achieved registration error evaluated on 23 sequences (5840 frames) is 0.78 ± 0.67 pixels inside the optic disc and 1.39 ± 0.63 pixels outside the optic disc. We compared the results with the commonly used approaches based on Lucas-Kanade tracking and scale-invariant feature transform, which achieved worse results. The proposed method can efficiently correct particular frames of retinal sequences for shift and rotation. The registration results for each frame (shift in X and Y direction and eye rotation) can also be used for eye-movement evaluation during single-spot fixation tasks.

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.

Recent developments in fast kurtosis imaging

NASA Astrophysics Data System (ADS)

Hansen, Brian; Jespersen, Sune N.

2017-09-01

Diffusion kurtosis imaging (DKI) is an extension of the popular diffusion tensor imaging (DTI) technique. DKI takes into account leading deviations from Gaussian diffusion stemming from a number of effects related to the microarchitecture and compartmentalization in biological tissues. DKI therefore offers increased sensitivity to subtle microstructural alterations over conventional diffusion imaging such as DTI, as has been demonstrated in numerous reports. For this reason, interest in routine clinical application of DKI is growing rapidly. In an effort to facilitate more widespread use of DKI, recent work by our group has focused on developing experimentally fast and robust estimates of DKI metrics. A significant increase in speed is made possible by a reduction in data demand achieved through rigorous analysis of the relation between the DKI signal and the kurtosis tensor based metrics. The fast DKI methods therefore need only 13 or 19 images for DKI parameter estimation compared to more than 60 for the most modest DKI protocols applied today. Closed form solutions also ensure rapid calculation of most DKI metrics. Some parameters can even be reconstructed in real time, which may be valuable in the clinic. The fast techniques are based on conventional diffusion sequences and are therefore easily implemented on almost any clinical system, in contrast to a range of other recently proposed advanced diffusion techniques. In addition to its general applicability, this also ensures that any acceleration achieved in conventional DKI through sequence or hardware optimization will also translate directly to fast DKI acquisitions. In this review, we recapitulate the theoretical basis for the fast kurtosis techniques and their relation to conventional DKI. We then discuss the currently available variants of the fast DKI methods, their strengths and weaknesses, as well as their respective realms of application. These range from whole body applications to methods mostly suited for spinal cord or peripheral nerve, and analysis specific to brain white matter. Having covered these technical aspects, we proceed to review the fast kurtosis literature including validation studies, organ specific optimization studies and results from clinical applications.

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.

A Patch-Based Method for Repetitive and Transient Event Detection in Fluorescence Imaging

PubMed Central

Boulanger, Jérôme; Gidon, Alexandre; Kervran, Charles; Salamero, Jean

2010-01-01

Automatic detection and characterization of molecular behavior in large data sets obtained by fast imaging in advanced light microscopy become key issues to decipher the dynamic architectures and their coordination in the living cell. Automatic quantification of the number of sudden and transient events observed in fluorescence microscopy is discussed in this paper. We propose a calibrated method based on the comparison of image patches expected to distinguish sudden appearing/vanishing fluorescent spots from other motion behaviors such as lateral movements. We analyze the performances of two statistical control procedures and compare the proposed approach to a frame difference approach using the same controls on a benchmark of synthetic image sequences. We have then selected a molecular model related to membrane trafficking and considered real image sequences obtained in cells stably expressing an endocytic-recycling trans-membrane protein, the Langerin-YFP, for validation. With this model, we targeted the efficient detection of fast and transient local fluorescence concentration arising in image sequences from a data base provided by two different microscopy modalities, wide field (WF) video microscopy using maximum intensity projection along the axial direction and total internal reflection fluorescence microscopy. Finally, the proposed detection method is briefly used to statistically explore the effect of several perturbations on the rate of transient events detected on the pilot biological model. PMID:20976222

Intensity inhomogeneity correction for magnetic resonance imaging of human brain at 7T.

PubMed

Uwano, Ikuko; Kudo, Kohsuke; Yamashita, Fumio; Goodwin, Jonathan; Higuchi, Satomi; Ito, Kenji; Harada, Taisuke; Ogawa, Akira; Sasaki, Makoto

2014-02-01

To evaluate the performance and efficacy for intensity inhomogeneity correction of various sequences of the human brain in 7T MRI using the extended version of the unified segmentation algorithm. Ten healthy volunteers were scanned with four different sequences (2D spin echo [SE], 3D fast SE, 2D fast spoiled gradient echo, and 3D time-of-flight) by using a 7T MRI system. Intensity inhomogeneity correction was performed using the "New Segment" module in SPM8 with four different values (120, 90, 60, and 30 mm) of full width at half maximum (FWHM) in Gaussian smoothness. The uniformity in signals in the entire white matter was evaluated using the coefficient of variation (CV); mean signal intensities between the subcortical and deep white matter were compared, and contrast between subcortical white matter and gray matter was measured. The length of the lenticulostriate (LSA) was measured on maximum intensity projection (MIP) images in the original and corrected images. In all sequences, the CV decreased as the FWHM value decreased. The differences of mean signal intensities between subcortical and deep white matter also decreased with smaller FWHM values. The contrast between white and gray matter was maintained at all FWHM values. LSA length was significantly greater in corrected MIP than in the original MIP images. Intensity inhomogeneity in 7T MRI can be successfully corrected using SPM8 for various scan sequences.

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

[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.

A powerful graphical pulse sequence programming tool for magnetic resonance imaging.

PubMed

Jie, Shen; Ying, Liu; Jianqi, Li; Gengying, Li

2005-12-01

A powerful graphical pulse sequence programming tool has been designed for creating magnetic resonance imaging (MRI) applications. It allows rapid development of pulse sequences in graphical mode (allowing for the visualization of sequences), and consists of three modules which include a graphical sequence editor, a parameter management module and a sequence compiler. Its key features are ease to use, flexibility and hardware independence. When graphic elements are combined with a certain text expressions, the graphical pulse sequence programming is as flexible as text-based programming tool. In addition, a hardware-independent design is implemented by using the strategy of two step compilations. To demonstrate the flexibility and the capability of this graphical sequence programming tool, a multi-slice fast spin echo experiment is performed on our home-made 0.3 T permanent magnet MRI system.

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.

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

Fat suppression at three-dimensional T1-weighted MR imaging of the hands: Dixon method versus CHESS technique.

PubMed

Kirchgesner, T; Perlepe, V; Michoux, N; Larbi, A; Vande Berg, B

2018-01-01

To compare the effectiveness of fat suppression and the image quality of the Dixon method with those of the chemical shift-selective (CHESS) technique in hands of normal subjects at non-enhanced three-dimensional (3D) T1-weighted MR imaging. Both hands of 14 healthy volunteers were imaged with 3D fast spoiled gradient echo (FSPGR) T1-weighted Dixon, 3D FSPGR T1-weighted CHESS and 3D T1-weighted fast spin echo (FSE) CHESS sequences in a 1.5T MR scanner. Three radiologists scored the effectiveness of fat suppression in bone marrow (EFS BM ) and soft tissues (EFS ST ) in 20 joints per subject. One radiologist measured the signal-to-noise ratio (SNR) in 10 bones per subject. Statistical analysis used two-way ANOVA with random effects (P<0.0083), paired t-test (P<0.05) and observed agreement to assess differences in effectiveness of fat suppression, differences in SNR and interobserver agreement. EFS BM was statistically significantly higher for the 3D FSPGR T1-weighted Dixon than for the 3D FSPGR T1-weighted CHESS sequence and the 3D FSE T1-weighted CHESS sequence (P<0.0001). EFS ST was statistically significantly higher for the 3D FSPGR T1-weighted Dixon than for the 3D FSPGR T1-weighted CHESS sequence (P<0.0011) and for the 3D FSE T1-weighted CHESS sequence in the axial plane (P=0.0028). Mean SNR was statistically significantly higher for 3D FSPGR T1-weighted Dixon sequence than for 3D FSPGR T1-weighted CHESS and 3D FSE T1-weighted CHESS sequences (P<0.0001). The Dixon method yields more effective fat suppression and higher SNR than the CHESS technique at 3D T1-weighted MR imaging of the hands. Copyright © 2017 Éditions françaises de radiologie. Published by Elsevier Masson SAS. All rights reserved.

Designing the optimal shutter sequences for the flutter shutter imaging method

NASA Astrophysics Data System (ADS)

Jelinek, Jan

2010-04-01

Acquiring iris or face images of moving subjects at larger distances using a flash to prevent the motion blur quickly runs into eye safety concerns as the acquisition distance is increased. For that reason the flutter shutter method recently proposed by Raskar et al.has generated considerable interest in the biometrics community. The paper concerns the design of shutter sequences that produce the best images. The number of possible sequences grows exponentially in both the subject' s motion velocity and desired exposure value, with their majority being useless. Because the exact solution leads to an intractable mixed integer programming problem, we propose an approximate solution based on pre - screening the sequences according to the distribution of roots in their Fourier transform. A very fast algorithm utilizing the Jury' s criterion allows the testing to be done without explicitly computing the roots, making the approach practical for moderately long sequences.

MR fingerprinting using fast imaging with steady state precession (FISP) with spiral readout.

PubMed

Jiang, Yun; Ma, Dan; Seiberlich, Nicole; Gulani, Vikas; Griswold, Mark A

2015-12-01

This study explores the possibility of using gradient echo-based sequences other than balanced steady-state free precession (bSSFP) in the magnetic resonance fingerprinting (MRF) framework to quantify the relaxation parameters . An MRF method based on a fast imaging with steady-state precession (FISP) sequence structure is presented. A dictionary containing possible signal evolutions with physiological range of T1 and T2 was created using the extended phase graph formalism according to the acquisition parameters. The proposed method was evaluated in a phantom and a human brain. T1 , T2 , and proton density were quantified directly from the undersampled data by the pattern recognition algorithm. T1 and T2 values from the phantom demonstrate that the results of MRF FISP are in good agreement with the traditional gold-standard methods. T1 and T2 values in brain are within the range of previously reported values. MRF-FISP enables a fast and accurate quantification of the relaxation parameters. It is immune to the banding artifact of bSSFP due to B0 inhomogeneities, which could improve the ability to use MRF for applications beyond brain imaging. © 2014 Wiley Periodicals, Inc.

MR Fingerprinting Using Fast Imaging with Steady State Precession (FISP) with Spiral Readout

PubMed Central

Jiang, Yun; Ma, Dan; Seiberlich, Nicole; Gulani, Vikas; Griswold, Mark A.

2015-01-01

Purpose This study explores the possibility of using gradient echo based sequences other than bSSFP in the magnetic resonance fingerprinting (MRF) framework to quantify the relaxation parameters. Methods An MRF method based on a fast imaging with steady state precession (FISP) sequence structure is presented. A dictionary containing possible signal evolutions with physiological range of T1 and T2 was created using the extended phase graph (EPG) formalism according to the acquisition parameters. The proposed method was evaluated in a phantom and a human brain. T1, T2 and proton density were quantified directly from the undersampled data by the pattern recognition algorithm. Results T1 and T2 values from the phantom demonstrate that the results of MRF FISP are in good agreement with the traditional gold-standard methods. T1 and T2 values in brain are within the range of previously reported values. Conclusion MRF FISP enables a fast and accurate quantification of the relaxation parameters, while is immune to the banding artifact of bSSFP due to B0 inhomogeneities, which could improve the ability to use MRF for applications beyond brain imaging. PMID:25491018

High resolution T2(*)-weighted Magnetic Resonance Imaging at 3 Tesla using PROPELLER-EPI.

PubMed

Krämer, Martin; Reichenbach, Jürgen R

2014-05-01

We report the application of PROPELLER-EPI for high resolution T2(*)-weighted imaging with sub-millimeter in-plane resolution on a clinical 3 Tesla scanner. Periodically rotated blades of a long-axis PROPELLER-EPI sequence were acquired with fast gradient echo readout and acquisition matrix of 320 × 50 per blade. Images were reconstructed by using 2D-gridding, phase and geometric distortion correction and compensation of resonance frequency drifts that occurred during extended measurements. To characterize these resonance frequency offsets, short FID calibration measurements were added to the PROPELLER-EPI sequence. Functional PROPELLER-EPI was performed with volunteers using a simple block design of right handed finger tapping. Results indicate that PROPELLER-EPI can be employed for fast, high resolution T2(*)-weighted imaging provided geometric distortions and possible resonance frequency drifts are properly corrected. Even small resonance frequency drifts below 10 Hz as well as non-corrected geometric distortions degraded image quality substantially. In the initial fMRI experiment image quality and signal-to-noise ratio was sufficient for obtaining high resolution functional activation maps. Copyright © 2014. Published by Elsevier GmbH.

[The use of the T2-weighted turbo-spin-echo sequence in studying the neurocranium. A comparison with the conventional T2-weighted spin-echo sequence].

PubMed

Siewert, C; Hosten, N; Felix, R

1994-07-01

T2-weighted spin-echo imaging is the standard screening procedure in MR imaging of the neurocranium. We evaluated fast spin-echo T2-weighted imaging (TT2) of the neurocranium in comparison to conventional spin-echo T2-weighted imaging (T2). Signal-to-noise and contrast-to-noise ratio of normal brain tissues (basal ganglia, grey and white matter, CSF fluid) and different pathologies were calculated. Signal-to-noise ratio and contrast-to-noise ratio were significantly higher in TT2 than in T2 (with the exception of gray-to-white matter contrast). Tissues with increased content of water protons (mobile protons) showed the highest contrast to surrounding tissues. The increased signal intensity of fat must be given due attention in fatty lesions. Because the contrast-to-noise ratio between white matter and basal ganglia is less in TT2, Parkinson patients have to be examined by conventional T2. If these limitations are taken into account, fast spin-echo T2-weighted imaging is well appropriate for MR imaging of the neurocranium, resulting in heavy T2-weighting achieved in a short acquisition time.

SU-C-17A-02: Sirius MRI Markers for Prostate Post-Implant Assessment: MR Protocol Development

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

Lim, T; Wang, J; Kudchadker, R

Purpose: Currently, CT is used to visualize prostate brachytherapy sources, at the expense of accurate structure contouring. MRI is superior to CT for anatomical delineation, but the sources appear as voids on MRI images. Previously we have developed Sirius MRI markers (C4 Imaging) to replace spacers to assist source localization on MRI images. Here we develop an MRI pulse sequence protocol that enhances the signal of these markers to enable MRI-only post-implant prostate dosimetric analysis. Methods: To simulate a clinical scenario, a CIRS multi-modality prostate phantom was implanted with 66 markers and 86 sources. The implanted phantom was imaged onmore » both 1.5T and 3.0T GE scanners under various conditions, different pulse sequences (2D fast spin echo [FSE], 3D balanced steadystate free precession [bSSFP] and 3D fast spoiled gradient echo [FSPGR]), as well as varying amount of padding to simulate various patient sizes and associated signal fall-off from the surface coil elements. Standard FSE sequences from the current clinical protocols were also evaluated. Marker visibility, marker size, intra-marker distance, total scan time and artifacts were evaluated for various combinations of echo time, repetition time, flip angle, number of excitations, bandwidth, slice thickness and spacing, fieldof- view, frequency/phase encoding steps and frequency direction. Results: We have developed a 3D FSPGR pulse sequence that enhances marker signal and ensures the integrity of the marker shape while maintaining reasonable scan time. For patients contraindicated for 3.0T, we have also developed a similar sequence for 1.5T scanners. Signal fall-off with distance from prostate to coil can be compensated mainly by decreasing bandwidth. The markers are not visible using standard FSE sequences. FSPGR sequences are more robust for consistent marker visualization as compared to bSSFP sequences. Conclusion: The developed MRI pulse sequence protocol for Sirius MRI markers assists source localization to enable MRIonly post-implant prostate dosimetric analysis. S.J. Frank is a co-founder of C4 Imaging (manufactures the MRI markers)« less

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.

An interleaved sequence for simultaneous magnetic resonance angiography (MRA), susceptibility weighted imaging (SWI) and quantitative susceptibility mapping (QSM).

PubMed

Chen, Yongsheng; Liu, Saifeng; Buch, Sagar; Hu, Jiani; Kang, Yan; Haacke, E Mark

2018-04-01

To image the entire vasculature of the brain with complete suppression of signal from background tissue using a single 3D excitation interleaved rephased/dephased multi-echo gradient echo sequence. This ensures no loss of signal from fast flow and provides co-registered susceptibility weighted images (SWI) and quantitative susceptibility maps (QSM) from the same scan. The suppression of background tissue was accomplished by subtracting the flow-dephased images from the flow-rephased images with the same echo time of 12.5ms to generate a magnetic resonance angiogram and venogram (MRAV). Further, a 2.5ms flow-compensated echo was added in the rephased portion to provide sufficient signal for major arteries with fast flow. The QSM data from the rephased 12.5ms echo was used to suppress veins on the MRAV to generate an artery-only MRA. The proposed approach was tested on five healthy volunteers at 3T. This three-echo interleaved GRE sequence provided complete background suppression of stationary tissues, while the short echo data gave high signal in the internal carotid and middle cerebral arteries (MCA). The contrast-to-noise ratio (CNR) of the arteries was significantly improved in the M3 territory of the MCA compared to the non-linear subtraction MRA and TOF-MRA. Veins were suppressed successfully utilizing the QSM data. The background tissue can be properly suppressed using the proposed interleaved MRAV sequence. One can obtain whole brain MRAV, MRA, SWI, true-SWI (or tSWI) and QSM data simultaneously from a single scan. Published by Elsevier Inc.

Fast volumetric imaging of bound and pore water in cortical bone using three-dimensional ultrashort-TE (UTE) and inversion recovery UTE sequences.

PubMed

Chen, Jun; Carl, Michael; Ma, Yajun; Shao, Hongda; Lu, Xing; Chen, Bimin; Chang, Eric Y; Wu, Zhihong; Du, Jiang

2016-10-01

We report the three-dimensional ultrashort-TE (3D UTE) and adiabatic inversion recovery UTE (IR-UTE) sequences employing a radial trajectory with conical view ordering for bi-component T2 * analysis of bound water (T2 *(BW) ) and pore water (T2 *(PW) ) in cortical bone. An interleaved dual-echo 3D UTE acquisition scheme was developed for fast bi-component analysis of bound and pore water in cortical bone. A 3D IR-UTE acquisition scheme employing multiple spokes per IR was developed for bound water imaging. Two-dimensional UTE (2D UTE) and IR-UTE sequences were employed for comparison. The sequences were applied to bovine bone samples (n = 6) and volunteers (n = 6) using a 3-T scanner. Bi-component fitting of 3D UTE images of bovine samples showed a mean T2 *(BW) of 0.26 ± 0.04 ms and T2 *(PW) of 4.16 ± 0.35 ms, with fractions of 21.5 ± 3.6% and 78.5 ± 3.6%, respectively. The 3D IR-UTE signal showed a single-component decay with a mean T2 *(BW) of 0.29 ± 0.05 ms, suggesting selective imaging of bound water. Similar results were achieved with the 2D UTE and IR-UTE sequences. Bi-component fitting of 3D UTE images of the tibial midshafts of healthy volunteers showed a mean T2 *(BW) of 0.32 ± 0.08 ms and T2 *(PW) of 5.78 ± 1.24 ms, with fractions of 34.2 ± 7.4% and 65.8 ± 7.4%, respectively. Single-component fitting of 3D IR-UTE images showed a mean T2 *(BW) of 0.35 ± 0.09 ms. The 3D UTE and 3D IR-UTE techniques allow fast volumetric mapping of bound and pore water in cortical bone. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Robust temporal alignment of multimodal cardiac sequences

NASA Astrophysics Data System (ADS)

Perissinotto, Andrea; Queirós, Sandro; Morais, Pedro; Baptista, Maria J.; Monaghan, Mark; Rodrigues, Nuno F.; D'hooge, Jan; Vilaça, João. L.; Barbosa, Daniel

2015-03-01

Given the dynamic nature of cardiac function, correct temporal alignment of pre-operative models and intraoperative images is crucial for augmented reality in cardiac image-guided interventions. As such, the current study focuses on the development of an image-based strategy for temporal alignment of multimodal cardiac imaging sequences, such as cine Magnetic Resonance Imaging (MRI) or 3D Ultrasound (US). First, we derive a robust, modality-independent signal from the image sequences, estimated by computing the normalized cross-correlation between each frame in the temporal sequence and the end-diastolic frame. This signal is a resembler for the left-ventricle (LV) volume curve over time, whose variation indicates different temporal landmarks of the cardiac cycle. We then perform the temporal alignment of these surrogate signals derived from MRI and US sequences of the same patient through Dynamic Time Warping (DTW), allowing to synchronize both sequences. The proposed framework was evaluated in 98 patients, which have undergone both 3D+t MRI and US scans. The end-systolic frame could be accurately estimated as the minimum of the image-derived surrogate signal, presenting a relative error of 1.6 +/- 1.9% and 4.0 +/- 4.2% for the MRI and US sequences, respectively, thus supporting its association with key temporal instants of the cardiac cycle. The use of DTW reduces the desynchronization of the cardiac events in MRI and US sequences, allowing to temporally align multimodal cardiac imaging sequences. Overall, a generic, fast and accurate method for temporal synchronization of MRI and US sequences of the same patient was introduced. This approach could be straightforwardly used for the correct temporal alignment of pre-operative MRI information and intra-operative US images.

[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.

The fractional Fourier transform and applications

NASA Technical Reports Server (NTRS)

Bailey, David H.; Swarztrauber, Paul N.

1991-01-01

This paper describes the 'fractional Fourier transform', which admits computation by an algorithm that has complexity proportional to the fast Fourier transform algorithm. Whereas the discrete Fourier transform (DFT) is based on integral roots of unity e exp -2(pi)i/n, the fractional Fourier transform is based on fractional roots of unity e exp -2(pi)i(alpha), where alpha is arbitrary. The fractional Fourier transform and the corresponding fast algorithm are useful for such applications as computing DFTs of sequences with prime lengths, computing DFTs of sparse sequences, analyzing sequences with noninteger periodicities, performing high-resolution trigonometric interpolation, detecting lines in noisy images, and detecting signals with linearly drifting frequencies. In many cases, the resulting algorithms are faster by arbitrarily large factors than conventional techniques.

Steady-state MR imaging sequences: physics, classification, and clinical applications.

PubMed

Chavhan, Govind B; Babyn, Paul S; Jankharia, Bhavin G; Cheng, Hai-Ling M; Shroff, Manohar M

2008-01-01

Steady-state sequences are a class of rapid magnetic resonance (MR) imaging techniques based on fast gradient-echo acquisitions in which both longitudinal magnetization (LM) and transverse magnetization (TM) are kept constant. Both LM and TM reach a nonzero steady state through the use of a repetition time that is shorter than the T2 relaxation time of tissue. When TM is maintained as multiple radiofrequency excitation pulses are applied, two types of signal are formed once steady state is reached: preexcitation signal (S-) from echo reformation; and postexcitation signal (S+), which consists of free induction decay. Depending on the signal sampled and used to form an image, steady-state sequences can be classified as (a) postexcitation refocused (only S+ is sampled), (b) preexcitation refocused (only S- is sampled), and (c) fully refocused (both S+ and S- are sampled) sequences. All tissues with a reasonably long T2 relaxation time will show additional signals due to various refocused echo paths. Steady-state sequences have revolutionized cardiac imaging and have become the standard for anatomic functional cardiac imaging and for the assessment of myocardial viability because of their good signal-to-noise ratio and contrast-to-noise ratio and increased speed of acquisition. They are also useful in abdominal and fetal imaging and hold promise for interventional MR imaging. Because steady-state sequences are now commonly used in MR imaging, radiologists will benefit from understanding the underlying physics, classification, and clinical applications of these sequences.

Distal airways in humans: dynamic hyperpolarized 3He MR imaging--feasibility

NASA Technical Reports Server (NTRS)

Tooker, Angela C.; Hong, Kwan Soo; McKinstry, Erin L.; Costello, Philip; Jolesz, Ferenc A.; Albert, Mitchell S.

2003-01-01

Dynamic hyperpolarized helium 3 (3He) magnetic resonance (MR) imaging of the human airways is achieved by using a fast gradient-echo pulse sequence during inhalation. The resulting dynamic images show differential contrast enhancement of both distal airways and the lung periphery, unlike static hyperpolarized 3He MR images on which only the lung periphery is seen. With this technique, up to seventh-generation airway branching can be visualized. Copyright RSNA, 2003.

Fast periodic presentation of natural images reveals a robust face-selective electrophysiological response in the human brain.

PubMed

Rossion, Bruno; Torfs, Katrien; Jacques, Corentin; Liu-Shuang, Joan

2015-01-16

We designed a fast periodic visual stimulation approach to identify an objective signature of face categorization incorporating both visual discrimination (from nonface objects) and generalization (across widely variable face exemplars). Scalp electroencephalographic (EEG) data were recorded in 12 human observers viewing natural images of objects at a rapid frequency of 5.88 images/s for 60 s. Natural images of faces were interleaved every five stimuli, i.e., at 1.18 Hz (5.88/5). Face categorization was indexed by a high signal-to-noise ratio response, specifically at an oddball face stimulation frequency of 1.18 Hz and its harmonics. This face-selective periodic EEG response was highly significant for every participant, even for a single 60-s sequence, and was generally localized over the right occipitotemporal cortex. The periodicity constraint and the large selection of stimuli ensured that this selective response to natural face images was free of low-level visual confounds, as confirmed by the absence of any oddball response for phase-scrambled stimuli. Without any subtraction procedure, time-domain analysis revealed a sequence of differential face-selective EEG components between 120 and 400 ms after oddball face image onset, progressing from medial occipital (P1-faces) to occipitotemporal (N1-faces) and anterior temporal (P2-faces) regions. Overall, this fast periodic visual stimulation approach provides a direct signature of natural face categorization and opens an avenue for efficiently measuring categorization responses of complex visual stimuli in the human brain. © 2015 ARVO.

MR-Guided Freehand Biopsy of Liver Lesions With Fast Continuous Imaging Using a 1.0-T Open MRI Scanner: Experience in 50 Patients

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

Fischbach, Frank, E-mail: frank.fischbach@med.ovgu.de; Bunke, Juergen; Thormann, Markus

2011-02-15

The purpose of this study was to assess a new open system with a field-strength of 1.0 T for the feasibility of liver biopsy using the freehand technique with fast continuous imaging. Fifty patients with focal liver lesions measuring 5 to 30 mm in diameter were included in the study. Guidance and monitoring was performed using a 1.0-T open magnetic resonance (MR) scanner (Panorama HFO; Philips Healthcare, Best, The Netherlands). With fast continuous imaging using a T1-weighted (T1W) gradient echo (GRE) sequence after administration of gadolinium (Gd)-EOB-DTPA, the needle was placed into the lesion. An interface for interactive dynamic viewingmore » in two perpendicular planes prevented needle deviations T2-weighted turbo spin echo (TSE) fat-suppressed sequence was added to rule out postinterventional hematoma or biloma. All lesions were visible on the interventional images. Biopsy was technically successful, and solid specimens were obtained in all cases. Forty-six patients showed a histopathologic pattern other than native liver tissue, thus confirming correct position of the needle. Time between determination of the lesion and performance of the control scan was on average 18 min. No major complications were recorded. MR guidance with the new 1-T open system must be considered an attractive alternative for liver punction. An interface for dynamic imaging of needle guidance and T1W-GRE imaging with administration of Gd-EOB-DTPA for contrast enhancement allows the pinpoint puncture of liver lesions.« less

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.

Small-tip fast recovery imaging using non-slice-selective tailored tip-up pulses and RF-spoiling

PubMed Central

Nielsen, Jon-Fredrik; Yoon, Daehyun; Noll, Douglas C.

2012-01-01

Small-tip fast recovery (STFR) imaging is a new steady-state imaging sequence that is a potential alternative to balanced steady-state free precession (bSSFP). Under ideal imaging conditions, STFR may provide comparable signal-to-noise ratio (SNR) and image contrast as bSSFP, but without signal variations due to resonance offset. STFR relies on a tailored “tip-up”, or “fast recovery”, RF pulse to align the spins with the longitudinal axis after each data readout segment. The design of the tip-up pulse is based on the acquisition of a separate off-resonance (B0) map. Unfortunately, the design of fast (a few ms) slice- or slab-selective RF pulses that accurately tailor the excitation pattern to the local B0 inhomogeneity over the entire imaging volume remains a challenging and unsolved problem. We introduce a novel implementation of STFR imaging based on non-slice-selective tip-up pulses, which simplifies the RF design problem significantly. Out-of-slice magnetization pathways are suppressed using RF-spoiling. Brain images obtained with this technique show excellent gray/white matter contrast, and point to the possibility of rapid steady-state T2/T1-weighted imaging with intrinsic suppression of cerebrospinal fluid, through-plane vessel signal, and off-resonance artifacts. In the future we expect STFR imaging to benefit significantly from parallel excitation hardware and high-order gradient shim systems. PMID:22511367

Sequencing technologies - the next generation.

PubMed

Metzker, Michael L

2010-01-01

Demand has never been greater for revolutionary technologies that deliver fast, inexpensive and accurate genome information. This challenge has catalysed the development of next-generation sequencing (NGS) technologies. The inexpensive production of large volumes of sequence data is the primary advantage over conventional methods. Here, I present a technical review of template preparation, sequencing and imaging, genome alignment and assembly approaches, and recent advances in current and near-term commercially available NGS instruments. I also outline the broad range of applications for NGS technologies, in addition to providing guidelines for platform selection to address biological questions of interest.

Isolation and molecular cloning of a fast-growing strain of human hepatitis A virus from its double-stranded replicative form.

PubMed Central

Venuti, A; Di Russo, C; del Grosso, N; Patti, A M; Ruggeri, F; De Stasio, P R; Martiniello, M G; Pagnotti, P; Degener, A M; Midulla, M

1985-01-01

A fast-growing strain of human hepatitis A virus was selected and characterized. The virus has the unusual property of developing a strong cytopathic effect in tissue culture in 7 to 10 days. Sequences of the viral genome were cloned into recombinant plasmids with the double-stranded replicative form as a template for the reverse transcription of cDNA. Restriction analysis and direct sequencing indicate that this strain is different from that described by Ticehurst et al. (Proc. Natl. Acad. Sci. USA 80:5885-5889, 1983) in the region that presumptively codes for the major capsid protein VP1, but both isolates have conserved large areas of homology in the untranslated 5'-terminal sequences of the genome. Images PMID:2997478

Ultrahigh-speed X-ray imaging of hypervelocity projectiles

NASA Astrophysics Data System (ADS)

Miller, Stuart; Singh, Bipin; Cool, Steven; Entine, Gerald; Campbell, Larry; Bishel, Ron; Rushing, Rick; Nagarkar, Vivek V.

2011-08-01

High-speed X-ray imaging is an extremely important modality for healthcare, industrial, military and research applications such as medical computed tomography, non-destructive testing, imaging in-flight projectiles, characterizing exploding ordnance, and analyzing ballistic impacts. We report on the development of a modular, ultrahigh-speed, high-resolution digital X-ray imaging system with large active imaging area and microsecond time resolution, capable of acquiring at a rate of up to 150,000 frames per second. The system is based on a high-resolution, high-efficiency, and fast-decay scintillator screen optically coupled to an ultra-fast image-intensified CCD camera designed for ballistic impact studies and hypervelocity projectile imaging. A specially designed multi-anode, high-fluence X-ray source with 50 ns pulse duration provides a sequence of blur-free images of hypervelocity projectiles traveling at speeds exceeding 8 km/s (18,000 miles/h). This paper will discuss the design, performance, and high frame rate imaging capability of the system.

Single Echo MRI

PubMed Central

Galiana, Gigi; Constable, R. Todd

2014-01-01

Purpose Previous nonlinear gradient research has focused on trajectories that reconstruct images with a minimum number of echoes. Here we describe sequences where the nonlinear gradients vary in time to acquire the image in a single readout. The readout is designed to be very smooth so that it can be compressed to minimal time without violating peripheral nerve stimulation limits, yielding an image from a single 4 ms echo. Theory and Methods This sequence was inspired by considering the code of each voxel, i.e. the phase accumulation that a voxel follows through the readout, an approach connected to traditional encoding theory. We present simulations for the initial sequence, a low slew rate analog, and higher resolution reconstructions. Results Extremely fast acquisitions are achievable, though as one would expect, SNR is reduced relative to the slower Cartesian sampling schemes because of the high gradient strengths. Conclusions The prospect that nonlinear gradients can acquire images in a single <10 ms echo makes this a novel and interesting approach to image encoding. PMID:24465837

Three-dimensional brain MRI for DBS patients within ultra-low radiofrequency power limits.

PubMed

Sarkar, Subhendra N; Papavassiliou, Efstathios; Hackney, David B; Alsop, David C; Shih, Ludy C; Madhuranthakam, Ananth J; Busse, Reed F; La Ruche, Susan; Bhadelia, Rafeeque A

2014-04-01

For patients with deep brain stimulators (DBS), local absorbed radiofrequency (RF) power is unknown and is much higher than what the system estimates. We developed a comprehensive, high-quality brain magnetic resonance imaging (MRI) protocol for DBS patients utilizing three-dimensional (3D) magnetic resonance sequences at very low RF power. Six patients with DBS were imaged (10 sessions) using a transmit/receive head coil at 1.5 Tesla with modified 3D sequences within ultra-low specific absorption rate (SAR) limits (0.1 W/kg) using T2 , fast fluid-attenuated inversion recovery (FLAIR) and T1 -weighted image contrast. Tissue signal and tissue contrast from the low-SAR images were subjectively and objectively compared with routine clinical images of six age-matched controls. Low-SAR images of DBS patients demonstrated tissue contrast comparable to high-SAR images and were of diagnostic quality except for slightly reduced signal. Although preliminary, we demonstrated diagnostic quality brain MRI with optimized, volumetric sequences in DBS patients within very conservative RF safety guidelines offering a greater safety margin. © 2014 International Parkinson and Movement Disorder Society.

Use of an advanced 3-T MRI movie to investigate articulation.

PubMed

Nunthayanon, Kulthida; Honda, Ei-ichi; Shimazaki, Kazuo; Ohmori, Hiroko; Inoue-Arai, Maristela Sayuri; Kurabayashi, Tohru; Ono, Takashi

2015-06-01

To develop a magnetic resonance imaging (MRI) movie to reveal the dynamic movement of articulators and teeth. Five healthy females with normal occlusion participated in this study. Various concentrations of MRI contrast media (ferric ammonium citrate [FAC]) were tested for visualization of teeth, according to facial markers and with the use of a gel. Custom-made circuitry was connected to synchronize pronunciation of fricative sounds (/asa/) with scans. Three gradient echo sequences (True fast imaging with steady state precession [true FISP], FISP, and fast low angle shot [FLASH]) with a segmented cine were tested with the use of repetition times (TRs) of 9 ms and 31.5 ms. The MRI movie images were superimposed over the boundaries of teeth. The images produced during pronunciation, using the two different TRs (9 ms and 31 ms), were compared to assess the position of the lips and the tongue. Images obtained using the FLASH sequence, with a TR of 9 ms or 31.5 ms, can be used for diagnostic purposes. A TR of 9 ms, with 161 continuous images acquired, produced the highest-quality images of teeth, with few artifacts present. Pronunciation of the consonant "s" was clearly discernable. Our 3-T MRI movie system, with a temporal resolution less than 9 ms, can provide detailed information pertaining to variations in speech or oropharyngeal function. Copyright © 2015 Elsevier Inc. All rights reserved.

Noninvasive Localization of Prostate Cancer via Diffusion Sensitive MRI

DTIC Science & Technology

2008-03-01

sequence, Haker et al and Roebuck et al using a line-scan diffusion sequence, and Vigneron et al using a fast spin-echo diffusion sequence (33,35-37...Mulkern RV, Haker S, Zhang J, Zou KH, Maier SE, Tempany CM. Detection of prostate cancer by integration of line-scan diffusion, T2-mapping and T2-weighted...36. Haker SJ, Szot Barnes A, Maier SE, Tempany CM, Mulkern RV. Diffusion Tensor Imaging for Prostate Cancer Detection: Preliminary Results from a

Simulation of concomitant magnetic fields on fast switched gradient coils used in advanced application of MRI

NASA Astrophysics Data System (ADS)

Salinas-Muciño, G.; Torres-García, E.; Hidalgo-Tobon, S.

2012-10-01

The process to produce an MR image includes nuclear alignment, RF excitation, spatial encoding, and image formation. To form an image, it is necessary to perform spatial localization of the MR signals, which is achieved using gradient coils. MRI requires the use of gradient coils that generate magnetic fields, which vary linearly with position over the imaging volume. Safety issues have been a motivation to study deeply the relation between the interaction of gradient magnetic field and the peripheral nerve stimulation. In this work is presented a numerical modeling between the concomitant magnetic fields produced by the gradient coils and the electric field induced in a cube with σ conductivity by the gradient field switching in pulse sequences as Eco planar Imaging (EPI), due to this kind of sequence is the most used in advance applications of magnetic resonance imaging as functional MRI, cardiac imaging or diffusion.

Medical image diagnoses by artificial neural networks with image correlation, wavelet transform, simulated annealing

NASA Astrophysics Data System (ADS)

Szu, Harold H.

1993-09-01

Classical artificial neural networks (ANN) and neurocomputing are reviewed for implementing a real time medical image diagnosis. An algorithm known as the self-reference matched filter that emulates the spatio-temporal integration ability of the human visual system might be utilized for multi-frame processing of medical imaging data. A Cauchy machine, implementing a fast simulated annealing schedule, can determine the degree of abnormality by the degree of orthogonality between the patient imagery and the class of features of healthy persons. An automatic inspection process based on multiple modality image sequences is simulated by incorporating the following new developments: (1) 1-D space-filling Peano curves to preserve the 2-D neighborhood pixels' relationship; (2) fast simulated Cauchy annealing for the global optimization of self-feature extraction; and (3) a mini-max energy function for the intra-inter cluster-segregation respectively useful for top-down ANN designs.

Comprehensive MR imaging of acute gynecologic diseases.

PubMed

Dohke, M; Watanabe, Y; Okumura, A; Amoh, Y; Hayashi, T; Yoshizako, T; Yasui, M; Nakashita, S; Nakanishi, J; Dodo, Y

2000-01-01

Rapid advances in techniques of magnetic resonance (MR) imaging have enabled diagnosis of acute gynecologic conditions, which are characterized by sudden onset of lower abdominal pain, fever, genital bleeding, intraperitoneal bleeding, or symptoms of shock. The chemical-selective fat-suppression technique not only helps establish the characteristics of lesions that contain fat components but also increases the conspicuity of inflammatory lesions. When a T2-weighted image is obtained with a very long effective echo time (>250 msec), even a small amount of ascites can be easily identified and the contrast between urine and complex fluid becomes more conspicuous. T2*-weighted images are useful for identification of hemorrhagic lesions by demonstrating deoxyhemoglobin and hemosiderin. Contrast material-enhanced dynamic subtraction MR imaging performed with a three-dimensional fast field-echo sequence and a rapid bolus injection of gadopentetate dimeglumine allows evaluation of lesion vascularity and the anatomic relationship between pelvic vessels and a lesion and allows identification of the bleeding point by demonstrating extravasation of contrast material. To optimize the MR imaging examination, attention should be given to the parameters of each pulse sequence and proper combination of the sequences.

Concrete thawing studied by single-point ramped imaging.

PubMed

Prado, P J; Balcom, B J; Beyea, S D; Armstrong, R L; Bremner, T W

1997-12-01

A series of two-dimensional images of proton distribution in a hardened concrete sample has been obtained during the thawing process (from -50 degrees C up to 11 degrees C). The SPRITE sequence is optimal for this study given the characteristic short relaxation times of water in this porous media (T2* < 200 micros and T1 < 3.6 ms). The relaxation parameters of the sample were determined in order to optimize the time efficiency of the sequence, permitting a 4-scan 64 x 64 acquisition in under 3 min. The image acquisition is fast on the time scale of the temperature evolution of the specimen. The frozen water distribution is quantified through a position based study of the image contrast. A multiple point acquisition method is presented and the signal sensitivity improvement is discussed.

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.

Fast 3D 1H MRSI of the Corticospinal Tract in Pediatric Brain

PubMed Central

Kim, Dong-Hyun; Gu, Meng; Cunningham, Charles; Chen, Albert; Baumer, Fiona; Glenn, Orit A.; Vigneron, Daniel B.; Spielman, Daniel Mark; Barkovich, Anthony James

2010-01-01

Purpose: To develop a 1H magnetic resonance spectroscopic imaging (MRSI) sequence that can be used to image infants/children at 3T and by combining it with diffusion tensor imaging (DTI) tractography, extract relevant metabolic information corresponding to the corticospinal tract (CST). Materials and Methods: A fast 3D MRSI sequence was developed for pediatric neuroimaging at 3T using spiral k-space readout and dual band RF pulses (32 × 32 × 8 cm field of view [FOV], 1 cc iso-resolution, TR/TE = 1500/130, 6:24 minute scan). Using DTI tractography to identify the motor tracts, spectra were extracted from the CSTs and quantified. Initial data from infants/children with suspected motor delay (n = 5) and age-matched controls (n = 3) were collected and N-acetylaspartate (NAA) ratios were quantified. Results: The average signal-to-noise ratio of the NAA peak from the studies was ≈22. Metabolite profiles were successfully acquired from the CST by using DTI tractography. Decreased NAA ratios in those with motor delay compared to controls of ≈10% at the CST were observed. Conclusion: A fast and robust 3D MRSI technique targeted for pediatric neuroimaging has been developed. By combining with DTI tractography, metabolic information from the CSTs can be retrieved and estimated. By combining DTI and 3D MRSI, spectral information from various tracts can be obtained and processed. PMID:19097091

Fast simultaneous noncontrast angiography and intraplaque hemorrhage (fSNAP) sequence for carotid artery imaging.

PubMed

Chen, Shuo; Ning, Jia; Zhao, Xihai; Wang, Jinnan; Zhou, Zechen; Yuan, Chun; Chen, Huijun

2017-02-01

To propose a fast simultaneous noncontrast angiography and intraplaque hemorrhage (fSNAP) sequence for carotid artery imaging. The proposed fSNAP sequence uses a low-resolution reference acquisition for phase-sensitive reconstruction to speed up the scan, and an inversion recovery acquisition with arbitrary k-space filling order to generate similar contrast to conventional SNAP. Four healthy volunteers and eight patients were recruited to test the performance of fSNAP in vivo. The lumen area quantification, muscle-blood CNR, IPH-blood CNR, lumen SNR, and standard deviation and intraplaque hemorrhage (IPH) detection accuracy were compared between fSNAP and SNAP. By using a low-resolution reference acquisition with 1/4 matrix size of the full-resolution reference scan, the scan time of fSNAP was 37.5% less than that of SNAP. A high agreement of lumen area measurement (ICC = 0.97, 95% CI: 0.96-0.99) and IPH detection (Kappa = 1) were found between fSNAP and SNAP. Also, no significant difference was found for muscle-blood CNR (P = 0.25), IPH-blood CNR (P = 0.35), lumen SNR (P = 0.60), and standard deviation (P = 0.46) between the two techniques. The feasibility of fSNAP was validated. fSNAP can improve the imaging efficiency with similar performance to SNAP on carotid artery imaging. Magn Reson Med 77:753-758, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Fast carotid artery MR angiography with compressed sensing based three-dimensional time-of-flight sequence.

PubMed

Li, Bo; Li, Hao; Dong, Li; Huang, Guofu

2017-11-01

In this study, we sought to investigate the feasibility of fast carotid artery MR angiography (MRA) by combining three-dimensional time-of-flight (3D TOF) with compressed sensing method (CS-3D TOF). A pseudo-sequential phase encoding order was developed for CS-3D TOF to generate hyper-intense vessel and suppress background tissues in under-sampled 3D k-space. Seven healthy volunteers and one patient with carotid artery stenosis were recruited for this study. Five sequential CS-3D TOF scans were implemented at 1, 2, 3, 4 and 5-fold acceleration factors for carotid artery MRA. Blood signal-to-tissue ratio (BTR) values for fully-sampled and under-sampled acquisitions were calculated and compared in seven subjects. Blood area (BA) was measured and compared between fully sampled acquisition and each under-sampled one. There were no significant differences between the fully-sampled dataset and each under-sampled in BTR comparisons (P>0.05 for all comparisons). The carotid vessel BAs measured from the images of CS-3D TOF sequences with 2, 3, 4 and 5-fold acceleration scans were all highly correlated with that of the fully-sampled acquisition. The contrast between blood vessels and background tissues of the images at 2 to 5-fold acceleration is comparable to that of fully sampled images. The images at 2× to 5× exhibit the comparable lumen definition to the corresponding images at 1×. By combining the pseudo-sequential phase encoding order, CS reconstruction, and 3D TOF sequence, this technique provides excellent visualizations for carotid vessel and calcifications in a short scan time. It has the potential to be integrated into current multiple blood contrast imaging protocol. Copyright © 2017. Published by Elsevier Inc.

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.

Large area high-speed metrology SPM system.

PubMed

Klapetek, P; Valtr, M; Picco, L; Payton, O D; Martinek, J; Yacoot, A; Miles, M

2015-02-13

We present a large area high-speed measuring system capable of rapidly generating nanometre resolution scanning probe microscopy data over mm(2) regions. The system combines a slow moving but accurate large area XYZ scanner with a very fast but less accurate small area XY scanner. This arrangement enables very large areas to be scanned by stitching together the small, rapidly acquired, images from the fast XY scanner while simultaneously moving the slow XYZ scanner across the region of interest. In order to successfully merge the image sequences together two software approaches for calibrating the data from the fast scanner are described. The first utilizes the low uncertainty interferometric sensors of the XYZ scanner while the second implements a genetic algorithm with multiple parameter fitting during the data merging step of the image stitching process. The basic uncertainty components related to these high-speed measurements are also discussed. Both techniques are shown to successfully enable high-resolution, large area images to be generated at least an order of magnitude faster than with a conventional atomic force microscope.

Large area high-speed metrology SPM system

NASA Astrophysics Data System (ADS)

Klapetek, P.; Valtr, M.; Picco, L.; Payton, O. D.; Martinek, J.; Yacoot, A.; Miles, M.

2015-02-01

We present a large area high-speed measuring system capable of rapidly generating nanometre resolution scanning probe microscopy data over mm2 regions. The system combines a slow moving but accurate large area XYZ scanner with a very fast but less accurate small area XY scanner. This arrangement enables very large areas to be scanned by stitching together the small, rapidly acquired, images from the fast XY scanner while simultaneously moving the slow XYZ scanner across the region of interest. In order to successfully merge the image sequences together two software approaches for calibrating the data from the fast scanner are described. The first utilizes the low uncertainty interferometric sensors of the XYZ scanner while the second implements a genetic algorithm with multiple parameter fitting during the data merging step of the image stitching process. The basic uncertainty components related to these high-speed measurements are also discussed. Both techniques are shown to successfully enable high-resolution, large area images to be generated at least an order of magnitude faster than with a conventional atomic force microscope.

Integration of retinal image sequences

NASA Astrophysics Data System (ADS)

Ballerini, Lucia

1998-10-01

In this paper a method for noise reduction in ocular fundus image sequences is described. The eye is the only part of the human body where the capillary network can be observed along with the arterial and venous circulation using a non invasive technique. The study of the retinal vessels is very important both for the study of the local pathology (retinal disease) and for the large amount of information it offers on systematic haemodynamics, such as hypertension, arteriosclerosis, and diabetes. In this paper a method for image integration of ocular fundus image sequences is described. The procedure can be divided in two step: registration and fusion. First we describe an automatic alignment algorithm for registration of ocular fundus images. In order to enhance vessel structures, we used a spatially oriented bank of filters designed to match the properties of the objects of interest. To evaluate interframe misalignment we adopted a fast cross-correlation algorithm. The performances of the alignment method have been estimated by simulating shifts between image pairs and by using a cross-validation approach. Then we propose a temporal integration technique of image sequences so as to compute enhanced pictures of the overall capillary network. Image registration is combined with image enhancement by fusing subsequent frames of a same region. To evaluate the attainable results, the signal-to-noise ratio was estimated before and after integration. Experimental results on synthetic images of vessel-like structures with different kind of Gaussian additive noise as well as on real fundus images are reported.

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.

Fast Human Detection for Intelligent Monitoring Using Surveillance Visible Sensors

PubMed Central

Ko, Byoung Chul; Jeong, Mira; Nam, JaeYeal

2014-01-01

Human detection using visible surveillance sensors is an important and challenging work for intruder detection and safety management. The biggest barrier of real-time human detection is the computational time required for dense image scaling and scanning windows extracted from an entire image. This paper proposes fast human detection by selecting optimal levels of image scale using each level's adaptive region-of-interest (ROI). To estimate the image-scaling level, we generate a Hough windows map (HWM) and select a few optimal image scales based on the strength of the HWM and the divide-and-conquer algorithm. Furthermore, adaptive ROIs are arranged per image scale to provide a different search area. We employ a cascade random forests classifier to separate candidate windows into human and nonhuman classes. The proposed algorithm has been successfully applied to real-world surveillance video sequences, and its detection accuracy and computational speed show a better performance than those of other related methods. PMID:25393782

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.

Fast global image smoothing based on weighted least squares.

PubMed

Min, Dongbo; Choi, Sunghwan; Lu, Jiangbo; Ham, Bumsub; Sohn, Kwanghoon; Do, Minh N

2014-12-01

This paper presents an efficient technique for performing a spatially inhomogeneous edge-preserving image smoothing, called fast global smoother. Focusing on sparse Laplacian matrices consisting of a data term and a prior term (typically defined using four or eight neighbors for 2D image), our approach efficiently solves such global objective functions. In particular, we approximate the solution of the memory-and computation-intensive large linear system, defined over a d-dimensional spatial domain, by solving a sequence of 1D subsystems. Our separable implementation enables applying a linear-time tridiagonal matrix algorithm to solve d three-point Laplacian matrices iteratively. Our approach combines the best of two paradigms, i.e., efficient edge-preserving filters and optimization-based smoothing. Our method has a comparable runtime to the fast edge-preserving filters, but its global optimization formulation overcomes many limitations of the local filtering approaches. Our method also achieves high-quality results as the state-of-the-art optimization-based techniques, but runs ∼10-30 times faster. Besides, considering the flexibility in defining an objective function, we further propose generalized fast algorithms that perform Lγ norm smoothing (0 < γ < 2) and support an aggregated (robust) data term for handling imprecise data constraints. We demonstrate the effectiveness and efficiency of our techniques in a range of image processing and computer graphics applications.

PET Imaging Stability Measurements During Simultaneous Pulsing of Aggressive MR Sequences on the SIGNA PET/MR System.

PubMed

Deller, Timothy W; Khalighi, Mohammad Mehdi; Jansen, Floris P; Glover, Gary H

2018-01-01

The recent introduction of simultaneous whole-body PET/MR scanners has enabled new research taking advantage of the complementary information obtainable with PET and MRI. One such application is kinetic modeling, which requires high levels of PET quantitative stability. To accomplish the required PET stability levels, the PET subsystem must be sufficiently isolated from the effects of MR activity. Performance measurements have previously been published, demonstrating sufficient PET stability in the presence of MR pulsing for typical clinical use; however, PET stability during radiofrequency (RF)-intensive and gradient-intensive sequences has not previously been evaluated for a clinical whole-body scanner. In this work, PET stability of the GE SIGNA PET/MR was examined during simultaneous scanning of aggressive MR pulse sequences. Methods: PET performance tests were acquired with MR idle and during simultaneous MR pulsing. Recent system improvements mitigating RF interference and gain variation were used. A fast recovery fast spin echo MR sequence was selected for high RF power, and an echo planar imaging sequence was selected for its high heat-inducing gradients. Measurements were performed to determine PET stability under varying MR conditions using the following metrics: sensitivity, scatter fraction, contrast recovery, uniformity, count rate performance, and image quantitation. A final PET quantitative stability assessment for simultaneous PET scanning during functional MRI studies was performed with a spiral in-and-out gradient echo sequence. Results: Quantitation stability of a 68 Ge flood phantom was demonstrated within 0.34%. Normalized sensitivity was stable during simultaneous scanning within 0.3%. Scatter fraction measured with a 68 Ge line source in the scatter phantom was stable within the range of 40.4%-40.6%. Contrast recovery and uniformity were comparable for PET images acquired simultaneously with multiple MR conditions. Peak noise equivalent count rate was 224 kcps at an effective activity concentration of 18.6 kBq/mL, and the count rate curves and scatter fraction curve were consistent for the alternating MR pulsing states. A final test demonstrated quantitative stability during a spiral functional MRI sequence. Conclusion: PET stability metrics demonstrated that PET quantitation was not affected during simultaneous aggressive MRI. This stability enables demanding applications such as kinetic modeling. © 2018 by the Society of Nuclear Medicine and Molecular Imaging.

Rotating single-shot acquisition (RoSA) with composite reconstruction for fast high-resolution diffusion imaging.

PubMed

Wen, Qiuting; Kodiweera, Chandana; Dale, Brian M; Shivraman, Giri; Wu, Yu-Chien

2018-01-01

To accelerate high-resolution diffusion imaging, rotating single-shot acquisition (RoSA) with composite reconstruction is proposed. Acceleration was achieved by acquiring only one rotating single-shot blade per diffusion direction, and high-resolution diffusion-weighted (DW) images were reconstructed by using similarities of neighboring DW images. A parallel imaging technique was implemented in RoSA to further improve the image quality and acquisition speed. RoSA performance was evaluated by simulation and human experiments. A brain tensor phantom was developed to determine an optimal blade size and rotation angle by considering similarity in DW images, off-resonance effects, and k-space coverage. With the optimal parameters, RoSA MR pulse sequence and reconstruction algorithm were developed to acquire human brain data. For comparison, multishot echo planar imaging (EPI) and conventional single-shot EPI sequences were performed with matched scan time, resolution, field of view, and diffusion directions. The simulation indicated an optimal blade size of 48 × 256 and a 30 ° rotation angle. For 1 × 1 mm 2 in-plane resolution, RoSA was 12 times faster than the multishot acquisition with comparable image quality. With the same acquisition time as SS-EPI, RoSA provided superior image quality and minimum geometric distortion. RoSA offers fast, high-quality, high-resolution diffusion images. The composite image reconstruction is model-free and compatible with various diffusion computation approaches including parametric and nonparametric analyses. Magn Reson Med 79:264-275, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

3D real-time visualization of blood flow in cerebral aneurysms by light field particle image velocimetry

NASA Astrophysics Data System (ADS)

Carlsohn, Matthias F.; Kemmling, André; Petersen, Arne; Wietzke, Lennart

2016-04-01

Cerebral aneurysms require endovascular treatment to eliminate potentially lethal hemorrhagic rupture by hemostasis of blood flow within the aneurysm. Devices (e.g. coils and flow diverters) promote homeostasis, however, measurement of blood flow within an aneurysm or cerebral vessel before and after device placement on a microscopic level has not been possible so far. This would allow better individualized treatment planning and improve manufacture design of devices. For experimental analysis, direct measurement of real-time microscopic cerebrovascular flow in micro-structures may be an alternative to computed flow simulations. An application of microscopic aneurysm flow measurement on a regular basis to empirically assess a high number of different anatomic shapes and the corresponding effect of different devices would require a fast and reliable method at low cost with high throughout assessment. Transparent three dimensional 3D models of brain vessels and aneurysms may be used for microscopic flow measurements by particle image velocimetry (PIV), however, up to now the size of structures has set the limits for conventional 3D-imaging camera set-ups. On line flow assessment requires additional computational power to cope with the processing large amounts of data generated by sequences of multi-view stereo images, e.g. generated by a light field camera capturing the 3D information by plenoptic imaging of complex flow processes. Recently, a fast and low cost workflow for producing patient specific three dimensional models of cerebral arteries has been established by stereo-lithographic (SLA) 3D printing. These 3D arterial models are transparent an exhibit a replication precision within a submillimeter range required for accurate flow measurements under physiological conditions. We therefore test the feasibility of microscopic flow measurements by PIV analysis using a plenoptic camera system capturing light field image sequences. Averaging across a sequence of single double or triple shots of flashed images enables reconstruction of the real-time corpuscular flow through the vessel system before and after device placement. This approach could enable 3D-insight of microscopic flow within blood vessels and aneurysms at submillimeter resolution. We present an approach that allows real-time assessment of 3D particle flow by high-speed light field image analysis including a solution that addresses high computational load by image processing. The imaging set-up accomplishes fast and reliable PIV analysis in transparent 3D models of brain aneurysms at low cost. High throughput microscopic flow assessment of different shapes of brain aneurysms may therefore be possibly required for patient specific device designs.

Role of 3.0 Tesla magnetic resonance hysterosalpingography in the diagnostic work-up of female infertility.

PubMed

Cipolla, Valentina; Guerrieri, Daniele; Pietrangeli, Daniela; Santucci, Domiziana; Argirò, Renato; de Felice, Carlo

2016-09-01

Imaging evaluation plays a crucial role in the diagnostic work-up of female infertility. In recent years, the possibility to evaluate tubal patency using 1.5 Tesla magnetic resonance (1.5T MR) has been studied. To assess the feasibility of 3.0 Tesla magnetic resonance (3.0T MR) hysterosalpingography and its role in the diagnostic work-up of female infertility and to evaluate if this fast "one-stop-shop" imaging approach should be proposed as a first-line examination. A total of 116 infertile women were enrolled in this prospective study; all underwent 3.0T MR hysterosalpingography. After standard imaging of the pelvis, tubal patency was assessed by acquiring 3D dynamic time-resolved T1-weighted (T1W) sequences during manual injection of 4-5 mL of contrast solution consisting of gadolinium and normal sterile saline. Images were evaluated by two radiologists with different experience in MR imaging (MRI). The examination was successfully completed in 96.5% of cases, failure rate was 3.5%. Dynamic sequences showed bilateral tubal patency in 64.3%, unilateral tubal patency in 25.9%, and bilateral tubal occlusion in 9.8%. Extratubal abnormalities were found in 69.9% of patients. Comprehensive analysis of morphological and dynamic sequences showed extratubal abnormalities in 43.1% of patients with bilateral tubal patency. 3.0T MR hysterosalpingography is a feasible, simple, fast, safe, and well-tolerated examination, which allows evaluation of tubal patency and other pelvic causes of female infertility in a single session, and it may thus represent a "one-stop-shop" solution in female infertility diagnostic work-up. © The Foundation Acta Radiologica 2015.

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).

Bowel MR imaging with oral Gastrografin: an experimental study with healthy volunteers.

PubMed

Borthne, A S; Dormagen, J B; Gjesdal, K I; Storaas, T; Lygren, I; Geitung, J T

2003-01-01

Our objective was to evaluate Gastrografin for MR bowel imaging. Twenty-three healthy volunteers in two randomised groups received 300 or 400 ml 50% Gastrografin, drunk continuously during 2 and 3 h, respectively. Images were applied during breath-hold in three orthogonal orientations. The balanced fast-field echo (BFFE) and balanced turbo field-echo (BTFE) sequences, with acquisition times from 13 to 25 s, were used before gadolinium (Gd) DTPA implying 1- to 2-mm-thick slices locally or 6-mm-thick slices through the entire gastrointestinal tract. The Gd-enhanced images were performed using a 3D T1-weighted FFE sequence with water selective excitation (Proset). Image quality, including bowel distention, homogeneity of opacification and wall conspicuity, were evaluated by two experienced reviewers, and the adverse reactions were recorded. Very good or excellent distention, homogeneity and wall conspicuity were achieved in the central segments from the ileum to the left colon flexure in 83-96% of cases, due to the adequate contrast media supply in these regions. Distention, homogeneity and delineation were good in the central segments of the remaining bowels. Diarrhoea was a major problem affecting all participants, followed by nausea. Provided that there is modern fast sequential technology, excellent MR imaging of the bowel can be achieved by the oral administration 50% diluted Gastrografin. Further studies are needed to refine the technique and optimise the quantity and concentration of Gastrografin in order to avoid or reduce adverse reactions.

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.

Implementation of fast macromolecular proton fraction mapping on 1.5 and 3 Tesla clinical MRI scanners: preliminary experience

NASA Astrophysics Data System (ADS)

Yarnykh, V.; Korostyshevskaya, A.

2017-08-01

Macromolecular proton fraction (MPF) is a biophysical parameter describing the amount of macromolecular protons involved into magnetization exchange with water protons in tissues. MPF represents a significant interest as a magnetic resonance imaging (MRI) biomarker of myelin for clinical applications. A recent fast MPF mapping method enabled clinical translation of MPF measurements due to time-efficient acquisition based on the single-point constrained fit algorithm. However, previous MPF mapping applications utilized only 3 Tesla MRI scanners and modified pulse sequences, which are not commonly available. This study aimed to test the feasibility of MPF mapping implementation on a 1.5 Tesla clinical scanner using standard manufacturer’s sequences and compare the performance of this method between 1.5 and 3 Tesla scanners. MPF mapping was implemented on 1.5 and 3 Tesla MRI units of one manufacturer with either optimized custom-written or standard product pulse sequences. Whole-brain three-dimensional MPF maps obtained from a single volunteer were compared between field strengths and implementation options. MPF maps demonstrated similar quality at both field strengths. MPF values in segmented brain tissues and specific anatomic regions appeared in close agreement. This experiment demonstrates the feasibility of fast MPF mapping using standard sequences on 1.5 T and 3 T clinical scanners.

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.

Magnetic resonance imaging for diagnosis and assessment of cartilage defect repairs.

PubMed

Marlovits, Stefan; Mamisch, Tallal Charles; Vekszler, György; Resinger, Christoph; Trattnig, Siegfried

2008-04-01

Clinical magnetic resonance imaging (MRI) is the method of choice for the non-invasive evaluation of articular cartilage defects and the follow-up of cartilage repair procedures. The use of cartilage-sensitive sequences and a high spatial-resolution technique enables the evaluation of cartilage morphology even in the early stages of disease, as well as assessment of cartilage repair. Sequences that offer high contrast between articular cartilage and adjacent structures, such as the fat-suppressed, 3-dimensional, spoiled gradient-echo sequence and the fast spin-echo sequence, are accurate and reliable for evaluating intrachondral lesions and surface defects of articular cartilage. These sequences can also be performed together in reasonable examination times. In addition to morphology, new MRI techniques provide insight into the biochemical composition of articular cartilage and cartilage repair tissue. These techniques enable the diagnosis of early cartilage degeneration and help to monitor the effect and outcome of various surgical and non-surgical cartilage repair therapies.

Diffusion-weighted imaging in patients with acute brain ischemia at 3 T: current possibilities and future perspectives comparing conventional echoplanar diffusion-weighted imaging and fast spin echo diffusion-weighted imaging sequences using BLADE (PROPELLER).

PubMed

Fries, Peter; Runge, Val M; Kirchin, Miles A; Stemmer, Alto; Naul, L Gill; Wiliams, Kenneth D; Reith, Wolfgang; Bücker, Arno; Schneider, Günther

2009-06-01

To compare diffusion-weighted imaging (DWI) based on a fast spin echo (FSE) sequence using BLADE (PROPELLER) with conventional DWI-echoplanar imaging (EPI) techniques at 3 T and to demonstrate the influence of hardware developments on signal-to-noise ratio (SNR) with these techniques using 12- and 32-channel head coils. Fourteen patients with brain ischemia were evaluated with DWI using EPI and FSE BLADE sequences, with a 12-channel head coil, in the axial plane and 1 additional plane (either sagittal or coronal). SNR and CNR were calculated from region-of-interest measurements. Scans were evaluated in a blinded fashion by 2 experienced neuroradiologists. SNR of both DWI techniques was evaluated in 12 healthy volunteers using different parallel imaging (PI) factors (for the EPI sequence) and both the 12- and 32-channel coils. DWI-BLADE sequences acquired with the 12-channel coil revealed a significant reduction in SNR (mean +/- SD) of ischemic lesions (SNR(lesion) [5.0 +/- 2.5]), normal brain (SNR(brain) [3.0 +/- 1.9]), and subsequently in CNR (3.0 +/- 1.8) as compared with the DWI-EPI sequence (SNR(lesion) [9.3 +/- 5.2], SNR(brain) [7.7 +/- 3.5], CNR [6.1 +/- 2.8], P < 0.001). Despite this reduction in SNR and CNR, the blinded read revealed a marked preference for the DWI-BLADE sequence, or equality between the sequences, in the majority of patients because lesion detection was degraded by susceptibility artifacts on axial DWI-EPI scans in 14% to 43% of cases (but in no instance with the DWI-BLADE sequence). In particular, preference for the DWI-BLADE sequence or equality between the 2 techniques for lesion detection in the brainstem and cerebellum was observed. On some DWI-BLADE scans, in the additional plane, radial-like artifacts degraded lesion detection.In volunteers, SNR was significantly improved using the 32-channel coil, irrespective of scan technique. Comparing DWI-EPI acquired with the 12-channel coil (iPAT = 2) to DWI-BLADE acquired with the 32-channel coil, comparable SNR values were obtained. The 32-channel coil also makes feasible, with DWI-EPI, an increase in the PI factor to 4, which allows for a further reduction of bulk susceptibility artifacts. However, still DWI-BLADE sequences performed better because of absence of bulk susceptibility artifacts at comparable SNR values. Despite lower SNR at comparable PI factors, DWI-BLADE sequences acquired using the 12-channel coil are preferable in most instances, as compared with DWI-EPI sequences, because of the absence of susceptibility artifacts and subsequently improved depiction of ischemic lesions in the brainstem and cerebellum. With the 32-channel coil, recently FDA approved, DWI-BLADE acquired with an iPAT = 2 provides comparable SNR without bulk susceptibility artifacts as compared with the DWI-EPI sequences acquired for clinical routine to date and has the potential to replace the standard DWI technique for special indications like DWI of the cerebellum and the brainstem or in presence of metallic implants or hemorrhage.

Fast inner-volume imaging of the lumbar spine with a spatially focused excitation using a 3D-TSE sequence.

PubMed

Riffel, Philipp; Michaely, Henrik J; Morelli, John N; Paul, Dominik; Kannengiesser, Stephan; Schoenberg, Stefan O; Haneder, Stefan

2015-04-01

The purpose of this study was to evaluate the feasibility and technical quality of a zoomed three-dimensional (3D) turbo spin-echo (TSE) sampling perfection with application optimized contrasts using different flip-angle evolutions (SPACE) sequence of the lumbar spine. In this prospective feasibility study, nine volunteers underwent a 3-T magnetic resonance examination of the lumbar spine including 1) a conventional 3D T2-weighted (T2w) SPACE sequence with generalized autocalibrating partially parallel acquisition technique acceleration factor 2 and 2) a zoomed 3D T2w SPACE sequence with a reduced field of view (reduction factor 2). Images were evaluated with regard to image sharpness, signal homogeneity, and the presence of artifacts by two experienced radiologists. For quantitative analysis, signal-to-noise ratio (SNR) values were calculated. Image sharpness of anatomic structures was statistically significantly greater with zoomed SPACE (P < .0001), whereas the signal homogeneity was statistically significantly greater with conventional SPACE (cSPACE; P = .0003). There were no statistically significant differences in extent of artifacts. Acquisition times were 8:20 minutes for cSPACE and 6:30 minutes for zoomed SPACE. Readers 1 and 2 selected zSPACE as the preferred sequence in five of nine cases. In two of nine cases, both sequences were rated as equally preferred by both the readers. SNR values were statistically significantly greater with cSPACE. In comparison to a cSPACE sequences, zoomed SPACE imaging of the lumbar spine provides sharper images in conjunction with a 25% reduction in acquisition time. Copyright © 2015 AUR. Published by Elsevier Inc. 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

Fractal-Based Image Compression

DTIC Science & Technology

1990-01-01

used Ziv - Lempel - experiments and for software development. Addi- Welch compression algorithm (ZLW) [51 [4] was used tional thanks to Roger Boss, Bill...vol17no. 6 (June 4) and with the minimum number of maps. [5] J. Ziv and A. Lempel , Compression of !ndivid- 5 Summary ual Sequences via Variable-Rate...transient and should be discarded. 2.5 Collage Theorem algorithm2 C3.2 Deterministic Algorithm for IFS Attractor For fast image compression the best

Quantifying metal-induced susceptibility artifacts of the instrumented spine at 1.5T using fast-spin echo and 3D-multispectral MRI.

PubMed

Kaushik, S Sivaram; Karr, Robin; Runquist, Matthew; Marszalkowski, Cathy; Sharma, Abhishiek; Rand, Scott D; Maiman, Dennis; Koch, Kevin M

2017-01-01

To evaluate magnetic resonance imaging (MRI) artifacts near metallic spinal instrumentation using both conventional metal artifact reduction sequences (MARS) and 3D multispectral imaging sequences (3D-MSI). Both MARS and 3D-MSI images were acquired in 10 subjects with titanium spinal hardware on a 1.5T GE 450W scanner. Clinical computed tomography (CT) images were used to measure the volume of the implant using seed-based region growing. Using 30-40 landmarks, the MARS and 3D-MSI images were coregistered to the CT images. Three independent users manually segmented the artifact volume from both MR sequences. For five L-spine subjects, one user independently segmented the nerve root in both MARS and 3D-MSI images. For all 10 subjects, the measured artifact volume for the 3D-MSI images closely matched that of the CT implant volume (absolute error: 4.3 ± 2.0 cm 3 ). The MARS artifact volume was ∼8-fold higher than that of the 3D-MSI images (30.7 ± 20.2, P = 0.002). The average nerve root volume for the MARS images was 24 ± 7.3% lower than the 3D-MSI images (P = 0.06). Compared to 3D-MSI images, the higher-resolution MARS images may help study features farther away from the implant surface. However, the MARS images retained substantial artifacts in the slice-dimension that result in a larger artifact volume. These artifacts have the potential to obscure physiologically relevant features, and can be mitigated with 3D-MSI sequences. Hence, MR study protocols may benefit with the inclusion both MARS and 3D-MSI sequences to accurately study pathology near the spine. 2 J. Magn. Reson. Imaging 2017;45:51-58. © 2016 International Society for Magnetic Resonance in Medicine.

Protocol optimization of sacroiliac joint MR Imaging at 3 Tesla: Impact of coil design and motion resistant sequences on image quality.

PubMed

Gondim Teixeira, P A; Bravetti, M; Hossu, G; Lecocq, S; Petit, D; Loeuille, D; Blum, A

2017-12-01

To evaluate the impact of coil design and motion-resistant sequences on the quality of sacroiliac magnetic resonance imaging (MRI) examination in patients with spondyloarthropathy. One hundred and twenty-one patients with suspected sacroiliitis and referred for MRI of the sacroiliac joints were retrospectively evaluated with MRI at 3-Tesla. There were 78 women and 43 men with a mean age of 36.7±11.5 (SD) years (range: 15.8-78.4 years). Conventional and motion-resistant fat-saturated fast-spin echo T2-weighted sequences were performed with two different coils. Image quality was subjectively evaluated by two independent readers (R1 and R2) using a four-point scale. Confidence in the identification of bone marrow edema pattern (BMEP) was also evaluated subjectively using a three-point scale. Phased array body coil yielded improved image quality compared to surface coil (14.1 to 30.4% for R1 and 14.6 to 25.7% for R2; P<0.0001). The impact of the sequence type on quality was also statistically significant (P=0.0046). BMEP was identified in 40 patients and best inter-reader agreement was obtained using the combination of phased-array body coil with motion-resistant T2-weighted sequence (kappa 0.990). The smallest number of indeterminate BMEP zones was seen on MRI set acquired with the phased-array body coil and motion-resistant T2-weighted sequence. Phased array body coil and motion-resistant T2-weighted sequences perform better than surface coil and conventional T2-weighted sequences for the evaluation of sacroiliac joints, increasing confidence in the identification of BMEP. Copyright © 2017 Editions françaises de radiologie. Published by Elsevier Masson SAS. All rights reserved.

Magnetic resonance imaging of the fetal brain.

PubMed

Tee, L Mf; Kan, E Yl; Cheung, J Cy; Leung, W C

2016-06-01

This review covers the recent literature on fetal brain magnetic resonance imaging, with emphasis on techniques, advances, common indications, and safety. We conducted a search of MEDLINE for articles published after 2010. The search terms used were "(fetal OR foetal OR fetus OR foetus) AND (MR OR MRI OR [magnetic resonance]) AND (brain OR cerebral)". Consensus statements from major authorities were also included. As a result, 44 relevant articles were included and formed the basis of this review. One major challenge is fetal motion that is largely overcome by ultra-fast sequences. Currently, single-shot fast spin-echo T2-weighted imaging remains the mainstay for motion resistance and anatomical delineation. Recently, a snap-shot inversion recovery sequence has enabled robust T1-weighted images to be obtained, which is previously a challenge for standard gradient-echo acquisitions. Fetal diffusion-weighted imaging, diffusion tensor imaging, and magnetic resonance spectroscopy are also being developed. With multiplanar capabilities, superior contrast resolution and field of view, magnetic resonance imaging does not have the limitations of sonography, and can provide additional important information. Common indications include ventriculomegaly, callosum and posterior fossa abnormalities, and twin complications. There are safety concerns about magnetic resonance-induced heating and acoustic damage but current literature showed no conclusive evidence of deleterious fetal effects. The American College of Radiology guideline states that pregnant patients can be accepted to undergo magnetic resonance imaging at any stage of pregnancy if risk-benefit ratio to patients warrants that the study be performed. Magnetic resonance imaging of the fetal brain is a safe and powerful adjunct to sonography in prenatal diagnosis. It can provide additional information that aids clinical management, prognostication, and counselling.

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

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.

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.

Real-time chirp-coded imaging with a programmable ultrasound biomicroscope.

PubMed

Bosisio, Mattéo R; Hasquenoph, Jean-Michel; Sandrin, Laurent; Laugier, Pascal; Bridal, S Lori; Yon, Sylvain

2010-03-01

Ultrasound biomicroscopy (UBM) of mice can provide a testing ground for new imaging strategies. The UBM system presented in this paper facilitates the development of imaging and measurement methods with programmable design, arbitrary waveform coding, broad bandwidth (2-80 MHz), digital filtering, programmable processing, RF data acquisition, multithread/multicore real-time display, and rapid mechanical scanning (

Liver acquisition with acceleration volume acquisition gadolinium-enhanced magnetic resonance combined with T2 sequences in the diagnosis of local recurrence of rectal cancer.

PubMed

Cao, Wuteng; Li, Fangqian; Gong, Jiaying; Liu, Dechao; Deng, Yanhong; Kang, Liang; Zhou, Zhiyang

2016-11-22

To investigate the efficacy of liver acquisition with acceleration volume acquisition (LAVA) gadolinium-enhanced magnetic resonance (MR) sequences and to assess its added accuracy in diagnosing local recurrence (LR) of rectal cancer with conventional T2-weighted fast spin echo (FSE) sequences. Pelvic MRI, including T2-weighted FSE sequences, gadolinium-enhanced sequences of LAVA and T1-weighted FSE with fat suppression, was performed on 225 patients with postoperative rectal cancer. Two readers evaluated the presence of LR according to "T2" (T2 sequences only), "T2 + LAVA-Gad" (LAVA and T2 imaging), and "T2 + T1-fs-Gad" (T1 fat suppression-enhanced sequence with T2 images). To evaluate diagnostic efficiency, imaging quality with LAVA and T1-fs-Gad by subjective scores and the signal intensity (SI) ratio. In the result, the SI ratio of LAVA was significantly higher than that of T1-fs-Gad (p = 0.0001). The diagnostic efficiency of "T2 + LAVA-Gad" was better than that of "T2 + T1-fs-Gad" (p = 0.0016 for Reader 1, p = 0.0001 for Reader 2) and T2 imaging only (p = 0.0001 for Reader 1; p = 0.0001 for Reader 2). Therefore, LAVA gadolinium-enhanced MR increases the accuracy of diagnosis of LR from rectal cancer and could replace conventional T1 gadolinium-enhanced sequences in the postoperative pelvic follow-up of rectal cancer.

FISSA: A neuropil decontamination toolbox for calcium imaging signals.

PubMed

Keemink, Sander W; Lowe, Scott C; Pakan, Janelle M P; Dylda, Evelyn; van Rossum, Mark C W; Rochefort, Nathalie L

2018-02-22

In vivo calcium imaging has become a method of choice to image neuronal population activity throughout the nervous system. These experiments generate large sequences of images. Their analysis is computationally intensive and typically involves motion correction, image segmentation into regions of interest (ROIs), and extraction of fluorescence traces from each ROI. Out of focus fluorescence from surrounding neuropil and other cells can strongly contaminate the signal assigned to a given ROI. In this study, we introduce the FISSA toolbox (Fast Image Signal Separation Analysis) for neuropil decontamination. Given pre-defined ROIs, the FISSA toolbox automatically extracts the surrounding local neuropil and performs blind-source separation with non-negative matrix factorization. Using both simulated and in vivo data, we show that this toolbox performs similarly or better than existing published methods. FISSA requires only little RAM, and allows for fast processing of large datasets even on a standard laptop. The FISSA toolbox is available in Python, with an option for MATLAB format outputs, and can easily be integrated into existing workflows. It is available from Github and the standard Python repositories.

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.

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.

Unusual MRI findings in an immunocompetent patient with EBV encephalitis: a case report

PubMed Central

2011-01-01

Blackground It is well-known that Epstein-Barr virus (EBV) can affect the central nervous system (CNS). Case presentation Herein the authors report unusual timely Magnetic Resonance Imaging (MRI) brain scan findings in an immunocompetent patient with EBV encephalitis. Diffusion weighted MRI sequence performed during the acute phase of the disease was normal, whereas the Fast Relaxation Fast Spin Echo T2 image showed diffuse signal intensity changes in white matter. The enhancement pattern suggested an inflammatory response restricted to the brain microcirculation. Acyclovir and corticosteroid therapy was administered. After three weeks, all signal intensities returned to normal and the patient showed clinical recovery. Conclusion This report demonstrates that EBV in an immunocompetent adult can present with diffuse, reversible brain white matter involvement in the acute phase of mononucleosis. Moreover, our case suggests that a negative DWI sequence is associated with a favorable improvement in severe EBV CNS infection. More extensive studies are needed to assess what other instrumental data can help to distinguish viral lesions from other causes in the acute phase of disease. PMID:21435249

a Fast Segmentation Algorithm for C-V Model Based on Exponential Image Sequence Generation

NASA Astrophysics Data System (ADS)

Hu, J.; Lu, L.; Xu, J.; Zhang, J.

2017-09-01

For the island coastline segmentation, a fast segmentation algorithm for C-V model method based on exponential image sequence generation is proposed in this paper. The exponential multi-scale C-V model with level set inheritance and boundary inheritance is developed. The main research contributions are as follows: 1) the problems of the "holes" and "gaps" are solved when extraction coastline through the small scale shrinkage, low-pass filtering and area sorting of region. 2) the initial value of SDF (Signal Distance Function) and the level set are given by Otsu segmentation based on the difference of reflection SAR on land and sea, which are finely close to the coastline. 3) the computational complexity of continuous transition are successfully reduced between the different scales by the SDF and of level set inheritance. Experiment results show that the method accelerates the acquisition of initial level set formation, shortens the time of the extraction of coastline, at the same time, removes the non-coastline body part and improves the identification precision of the main body coastline, which automates the process of coastline segmentation.

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.

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.

Rapid whole-brain resting-state fMRI at 3 T: Efficiency-optimized three-dimensional EPI versus repetition time-matched simultaneous-multi-slice EPI.

PubMed

Stirnberg, Rüdiger; Huijbers, Willem; Brenner, Daniel; Poser, Benedikt A; Breteler, Monique; Stöcker, Tony

2017-12-01

State-of-the-art simultaneous-multi-slice (SMS-)EPI and 3D-EPI share several properties that benefit functional MRI acquisition. Both sequences employ equivalent parallel imaging undersampling with controlled aliasing to achieve high temporal sampling rates. As a volumetric imaging sequence, 3D-EPI offers additional means of acceleration complementary to 2D-CAIPIRINHA sampling, such as fast water excitation and elliptical sampling. We performed an application-oriented comparison between a tailored, six-fold CAIPIRINHA-accelerated 3D-EPI protocol at 530 ms temporal and 2.4 mm isotropic spatial resolution and an SMS-EPI protocol with identical spatial and temporal resolution for whole-brain resting-state fMRI at 3 T. The latter required eight-fold slice acceleration to compensate for the lack of elliptical sampling and fast water excitation. Both sequences used vendor-supplied on-line image reconstruction. We acquired test/retest resting-state fMRI scans in ten volunteers, with simultaneous acquisition of cardiac and respiration data, subsequently used for optional physiological noise removal (nuisance regression). We found that the 3D-EPI protocol has significantly increased temporal signal-to-noise ratio throughout the brain as compared to the SMS-EPI protocol, especially when employing motion and nuisance regression. Both sequence types reliably identified known functional networks with stronger functional connectivity values for the 3D-EPI protocol. We conclude that the more time-efficient 3D-EPI primarily benefits from reduced parallel imaging noise due to a higher, actual k-space sampling density compared to SMS-EPI. The resultant BOLD sensitivity increase makes 3D-EPI a valuable alternative to SMS-EPI for whole-brain fMRI at 3 T, with voxel sizes well below 3 mm isotropic and sampling rates high enough to separate dominant cardiac signals from BOLD signals in the frequency domain. Copyright © 2017 Elsevier Inc. All rights reserved.

A flexible new method for 3D measurement based on multi-view image sequences

NASA Astrophysics Data System (ADS)

Cui, Haihua; Zhao, Zhimin; Cheng, Xiaosheng; Guo, Changye; Jia, Huayu

2016-11-01

Three-dimensional measurement is the base part for reverse engineering. The paper developed a new flexible and fast optical measurement method based on multi-view geometry theory. At first, feature points are detected and matched with improved SIFT algorithm. The Hellinger Kernel is used to estimate the histogram distance instead of traditional Euclidean distance, which is immunity to the weak texture image; then a new filter three-principle for filtering the calculation of essential matrix is designed, the essential matrix is calculated using the improved a Contrario Ransac filter method. One view point cloud is constructed accurately with two view images; after this, the overlapped features are used to eliminate the accumulated errors caused by added view images, which improved the camera's position precision. At last, the method is verified with the application of dental restoration CAD/CAM, experiment results show that the proposed method is fast, accurate and flexible for tooth 3D measurement.

Brain MR imaging at ultra-low radiofrequency power.

PubMed

Sarkar, Subhendra N; Alsop, David C; Madhuranthakam, Ananth J; Busse, Reed F; Robson, Philip M; Rofsky, Neil M; Hackney, David B

2011-05-01

To explore the lower limits for radiofrequency (RF) power-induced specific absorption rate (SAR) achievable at 1.5 T for brain magnetic resonance (MR) imaging without loss of tissue signal or contrast present in high-SAR clinical imaging in order to create a potentially viable MR method at ultra-low RF power to image tissues containing implanted devices. An institutional review board-approved HIPAA-compliant prospective MR study design was used, with written informed consent from all subjects prior to MR sessions. Seven healthy subjects were imaged prospectively at 1.5 T with ultra-low-SAR optimized three-dimensional (3D) fast spin-echo (FSE) and fluid-attenuated inversion-recovery (FLAIR) T2-weighted sequences and an ultra-low-SAR 3D spoiled gradient-recalled acquisition in the steady state T1-weighted sequence. Corresponding high-SAR two-dimensional (2D) clinical sequences were also performed. In addition to qualitative comparisons, absolute signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) for multicoil, parallel imaging acquisitions were generated by using a Monte Carlo method for quantitative comparison between ultra-low-SAR and high-SAR results. There were minor to moderate differences in the absolute tissue SNR and CNR values and in qualitative appearance of brain images obtained by using ultra-low-SAR and high-SAR techniques. High-SAR 2D T2-weighted imaging produced slightly higher SNR, while ultra-low-SAR 3D technique not only produced higher SNR for T1-weighted and FLAIR images but also higher CNRs for all three sequences for most of the brain tissues. The 3D techniques adopted here led to a decrease in the absorbed RF power by two orders of magnitude at 1.5 T, and still the image quality was preserved within clinically acceptable imaging times. RSNA, 2011

1.5 versus 3 versus 7 Tesla in abdominal MRI: A comparative study.

PubMed

Laader, Anja; Beiderwellen, Karsten; Kraff, Oliver; Maderwald, Stefan; Wrede, Karsten; Ladd, Mark E; Lauenstein, Thomas C; Forsting, Michael; Quick, Harald H; Nassenstein, Kai; Umutlu, Lale

2017-01-01

The aim of this study was to investigate and compare the feasibility as well as potential impact of altered magnetic field properties on image quality and potential artifacts of 1.5 Tesla, 3 Tesla and 7 Tesla non-enhanced abdominal MRI. Magnetic Resonance (MR) imaging of the upper abdomen was performed in 10 healthy volunteers on a 1.5 Tesla, a 3 Tesla and a 7 Tesla MR system. The study protocol comprised a (1) T1-weighted fat-saturated spoiled gradient-echo sequence (2D FLASH), (2) T1-weighted fat-saturated volumetric interpolated breath hold examination sequence (3D VIBE), (3) T1-weighted 2D in and opposed phase sequence, (4) True fast imaging with steady-state precession sequence (TrueFISP) and (5) T2-weighted turbo spin-echo (TSE) sequence. For comparison reasons field of view and acquisition times were kept comparable for each correlating sequence at all three field strengths, while trying to achieve the highest possible spatial resolution. Qualitative and quantitative analyses were tested for significant differences. While 1.5 and 3 Tesla MRI revealed comparable results in all assessed features and sequences, 7 Tesla MRI yielded considerable differences in T1 and T2 weighted imaging. Benefits of 7 Tesla MRI encompassed an increased higher spatial resolution and a non-enhanced hyperintense vessel signal at 7 Tesla, potentially offering a more accurate diagnosis of abdominal parenchymatous and vasculature disease. 7 Tesla MRI was also shown to be more impaired by artifacts, including residual B1 inhomogeneities, susceptibility and chemical shift artifacts, resulting in reduced overall image quality and overall image impairment ratings. While 1.5 and 3 Tesla T2w imaging showed equivalently high image quality, 7 Tesla revealed strong impairments in its diagnostic value. Our results demonstrate the feasibility and overall comparable imaging ability of T1-weighted 7 Tesla abdominal MRI towards 3 Tesla and 1.5 Tesla MRI, yielding a promising diagnostic potential for non-enhanced Magnetic Resonance Angiography (MRA). 1.5 Tesla and 3 Tesla offer comparably high-quality T2w imaging, showing superior diagnostic quality over 7 Tesla MRI.

1.5 versus 3 versus 7 Tesla in abdominal MRI: A comparative study

PubMed Central

Beiderwellen, Karsten; Kraff, Oliver; Maderwald, Stefan; Wrede, Karsten; Ladd, Mark E.; Lauenstein, Thomas C.; Forsting, Michael; Quick, Harald H.; Nassenstein, Kai; Umutlu, Lale

2017-01-01

Objectives The aim of this study was to investigate and compare the feasibility as well as potential impact of altered magnetic field properties on image quality and potential artifacts of 1.5 Tesla, 3 Tesla and 7 Tesla non-enhanced abdominal MRI. Materials and methods Magnetic Resonance (MR) imaging of the upper abdomen was performed in 10 healthy volunteers on a 1.5 Tesla, a 3 Tesla and a 7 Tesla MR system. The study protocol comprised a (1) T1-weighted fat-saturated spoiled gradient-echo sequence (2D FLASH), (2) T1-weighted fat-saturated volumetric interpolated breath hold examination sequence (3D VIBE), (3) T1-weighted 2D in and opposed phase sequence, (4) True fast imaging with steady-state precession sequence (TrueFISP) and (5) T2-weighted turbo spin-echo (TSE) sequence. For comparison reasons field of view and acquisition times were kept comparable for each correlating sequence at all three field strengths, while trying to achieve the highest possible spatial resolution. Qualitative and quantitative analyses were tested for significant differences. Results While 1.5 and 3 Tesla MRI revealed comparable results in all assessed features and sequences, 7 Tesla MRI yielded considerable differences in T1 and T2 weighted imaging. Benefits of 7 Tesla MRI encompassed an increased higher spatial resolution and a non-enhanced hyperintense vessel signal at 7 Tesla, potentially offering a more accurate diagnosis of abdominal parenchymatous and vasculature disease. 7 Tesla MRI was also shown to be more impaired by artifacts, including residual B1 inhomogeneities, susceptibility and chemical shift artifacts, resulting in reduced overall image quality and overall image impairment ratings. While 1.5 and 3 Tesla T2w imaging showed equivalently high image quality, 7 Tesla revealed strong impairments in its diagnostic value. Conclusions Our results demonstrate the feasibility and overall comparable imaging ability of T1-weighted 7 Tesla abdominal MRI towards 3 Tesla and 1.5 Tesla MRI, yielding a promising diagnostic potential for non-enhanced Magnetic Resonance Angiography (MRA). 1.5 Tesla and 3 Tesla offer comparably high-quality T2w imaging, showing superior diagnostic quality over 7 Tesla MRI. PMID:29125850

SAR and scan-time optimized 3D whole-brain double inversion recovery imaging at 7T.

PubMed

Pracht, Eberhard D; Feiweier, Thorsten; Ehses, Philipp; Brenner, Daniel; Roebroeck, Alard; Weber, Bernd; Stöcker, Tony

2018-05-01

The aim of this project was to implement an ultra-high field (UHF) optimized double inversion recovery (DIR) sequence for gray matter (GM) imaging, enabling whole brain coverage in short acquisition times ( ≈5 min, image resolution 1 mm 3 ). A 3D variable flip angle DIR turbo spin echo (TSE) sequence was optimized for UHF application. We implemented an improved, fast, and specific absorption rate (SAR) efficient TSE imaging module, utilizing improved reordering. The DIR preparation was tailored to UHF application. Additionally, fat artifacts were minimized by employing water excitation instead of fat saturation. GM images, covering the whole brain, were acquired in 7 min scan time at 1 mm isotropic resolution. SAR issues were overcome by using a dedicated flip angle calculation considering SAR and SNR efficiency. Furthermore, UHF related artifacts were minimized. The suggested sequence is suitable to generate GM images with whole-brain coverage at UHF. Due to the short total acquisition times and overall robustness, this approach can potentially enable DIR application in a routine setting and enhance lesion detection in neurological diseases. Magn Reson Med 79:2620-2628, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Simultaneous Multi-Slice fMRI using Spiral Trajectories

PubMed Central

Zahneisen, Benjamin; Poser, Benedikt A.; Ernst, Thomas; Stenger, V. Andrew

2014-01-01

Parallel imaging methods using multi-coil receiver arrays have been shown to be effective for increasing MRI acquisition speed. However parallel imaging methods for fMRI with 2D sequences show only limited improvements in temporal resolution because of the long echo times needed for BOLD contrast. Recently, Simultaneous Multi-Slice (SMS) imaging techniques have been shown to increase fMRI temporal resolution by factors of four and higher. In SMS fMRI multiple slices can be acquired simultaneously using Echo Planar Imaging (EPI) and the overlapping slices are un-aliased using a parallel imaging reconstruction with multiple receivers. The slice separation can be further improved using the “blipped-CAIPI” EPI sequence that provides a more efficient sampling of the SMS 3D k-space. In this paper a blipped-spiral SMS sequence for ultra-fast fMRI is presented. The blipped-spiral sequence combines the sampling efficiency of spiral trajectories with the SMS encoding concept used in blipped-CAIPI EPI. We show that blipped spiral acquisition can achieve almost whole brain coverage at 3 mm isotropic resolution in 168 ms. It is also demonstrated that the high temporal resolution allows for dynamic BOLD lag time measurement using visual/motor and retinotopic mapping paradigms. The local BOLD lag time within the visual cortex following the retinotopic mapping stimulation of expanding flickering rings is directly measured and easily translated into an eccentricity map of the cortex. PMID:24518259

Abdominal MRI at 3.0 T: LAVA-Flex compared with conventional fat suppression T1-weighted images.

PubMed

Li, Xing Hui; Zhu, Jiang; Zhang, Xiao Ming; Ji, Yi Fan; Chen, Tian Wu; Huang, Xiao Hua; Yang, Lin; Zeng, Nan Lin

2014-07-01

To study liver imaging with volume acceleration-flexible (LAVA-Flex) for abdominal magnetic resonance imaging (MRI) at 3.0 T and compare the image quality of abdominal organs between LAVA-Flex and fast spoiled gradient-recalled (FSPGR) T1-weighted imaging. Our Institutional Review Board approval was obtained in this retrospective study. Sixty-nine subjects had both FSPGR and LAVA-Flex sequences. Two radiologists independently scored the acquisitions for image quality, fat suppression quality, and artifacts and the values obtained were compared with the Wilcoxon signed rank test. According to the signal intensity (SI) measurements, the uniformity of fat suppression, the contrast between muscle and fat and normal liver and liver lesions were compared by the paired t-test. The liver and spleen SI on the fat-only phase were analyzed in the fatty liver patients. Compared with FSPGR imaging, LAVA-Flex images had better and more homogenous fat suppression and lower susceptibility artifact (qualitative scores: 4.70 vs. 4.00, 4.86% vs. 7.14%, 4.60 and 4.10, respectively). The contrast between muscle and fat and between the liver and pathologic lesions was significantly improved on the LAVA-Flex sequence. The contrast value of the fatty liver and spleen was higher than that of the liver and spleen. The LAVA-Flex sequence offers superior and more homogenous fat suppression of the abdomen than does the FSPGR sequence. The fat-only phase can be a simple and effective method of assessing fatty liver. © 2013 Wiley Periodicals, Inc.

A fast and automatic fusion algorithm for unregistered multi-exposure image sequence

NASA Astrophysics Data System (ADS)

Liu, Yan; Yu, Feihong

2014-09-01

Human visual system (HVS) can visualize all the brightness levels of the scene through visual adaptation. However, the dynamic range of most commercial digital cameras and display devices are smaller than the dynamic range of human eye. This implies low dynamic range (LDR) images captured by normal digital camera may lose image details. We propose an efficient approach to high dynamic (HDR) image fusion that copes with image displacement and image blur degradation in a computationally efficient manner, which is suitable for implementation on mobile devices. The various image registration algorithms proposed in the previous literatures are unable to meet the efficiency and performance requirements in the application of mobile devices. In this paper, we selected Oriented Brief (ORB) detector to extract local image structures. The descriptor selected in multi-exposure image fusion algorithm has to be fast and robust to illumination variations and geometric deformations. ORB descriptor is the best candidate in our algorithm. Further, we perform an improved RANdom Sample Consensus (RANSAC) algorithm to reject incorrect matches. For the fusion of images, a new approach based on Stationary Wavelet Transform (SWT) is used. The experimental results demonstrate that the proposed algorithm generates high quality images at low computational cost. Comparisons with a number of other feature matching methods show that our method gets better performance.

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.

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.

Magnetic resonance cinematography of the fingers: a 3.0 Tesla feasibility study with comparison of incremental and continuous dynamic protocols.

PubMed

Bayer, Thomas; Adler, Werner; Janka, Rolf; Uder, Michael; Roemer, Frank

2017-12-01

To study the feasibility of magnetic resonance cinematography of the fingers (MRCF) with comparison of image quality of different protocols for depicting the finger anatomy during motion. MRCF was performed during a full flexion and extension movement in 14 healthy volunteers using a finger-gating device. Three real-time sequences (frame rates 17-59 images/min) and one proton density (PD) sequence (3 images/min) were acquired during incremental and continuous motion. Analyses were performed independently by three readers. Qualitative image analysis included Likert-scale grading from 0 (useless) to 5 (excellent) and specific visual analog scale (VAS) grading from 0 (insufficient) to 100 (excellent). Signal-to-noise calculation was performed. Overall percentage agreement and mean absolute disagreement were calculated. Within the real-time sequences a high frame-rate true fast imaging with steady-state free precession (TRUFI) yielded the best image quality with Likert and overall VAS scores of 3.0 ± 0.2 and 60.4 ± 25.3, respectively. The best sequence regarding image quality was an incremental PD with mean values of 4.8 ± 0.2 and 91.2 ± 9.4, respectively. Overall percentage agreement and mean absolute disagreement were 47.9 and 0.7, respectively. No statistically significant SNR differences were found between continuous and incremental motion for the real-time protocols. MRCF is feasible with appropriate image quality during continuous motion using a finger-gating device. Almost perfect image quality is achievable with incremental PD imaging, which represents a compromise for MRCF with the drawback of prolonged scanning time.

Ultrafast Pulse Sequencing for Fast Projective Measurements of Atomic Hyperfine Qubits

NASA Astrophysics Data System (ADS)

Ip, Michael; Ransford, Anthony; Campbell, Wesley

2015-05-01

Projective readout of quantum information stored in atomic hyperfine structure typically uses state-dependent CW laser-induced fluorescence. This method requires an often sophisticated imaging system to spatially filter out the background CW laser light. We present an alternative approach that instead uses simple pulse sequences from a mode-locked laser to affect the same state-dependent excitations in less than 1 ns. The resulting atomic fluorescence occurs in the dark, allowing the placement of non-imaging detectors right next to the atom to improve the qubit state detection efficiency and speed. We also discuss methods of Doppler cooling with mode-locked lasers for trapped ions, where the creation of the necessary UV light is often difficult with CW lasers.

Automated segmentation of three-dimensional MR brain images

NASA Astrophysics Data System (ADS)

Park, Jonggeun; Baek, Byungjun; Ahn, Choong-Il; Ku, Kyo Bum; Jeong, Dong Kyun; Lee, Chulhee

2006-03-01

Brain segmentation is a challenging problem due to the complexity of the brain. In this paper, we propose an automated brain segmentation method for 3D magnetic resonance (MR) brain images which are represented as a sequence of 2D brain images. The proposed method consists of three steps: pre-processing, removal of non-brain regions (e.g., the skull, meninges, other organs, etc), and spinal cord restoration. In pre-processing, we perform adaptive thresholding which takes into account variable intensities of MR brain images corresponding to various image acquisition conditions. In segmentation process, we iteratively apply 2D morphological operations and masking for the sequences of 2D sagittal, coronal, and axial planes in order to remove non-brain tissues. Next, final 3D brain regions are obtained by applying OR operation for segmentation results of three planes. Finally we reconstruct the spinal cord truncated during the previous processes. Experiments are performed with fifteen 3D MR brain image sets with 8-bit gray-scale. Experiment results show the proposed algorithm is fast, and provides robust and satisfactory results.

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.

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

High-speed large angle mammography tomosynthesis system

NASA Astrophysics Data System (ADS)

Eberhard, Jeffrey W.; Staudinger, Paul; Smolenski, Joe; Ding, Jason; Schmitz, Andrea; McCoy, Julie; Rumsey, Michael; Al-Khalidy, Abdulrahman; Ross, William; Landberg, Cynthia E.; Claus, Bernhard E. H.; Carson, Paul; Goodsitt, Mitchell; Chan, Heang-Ping; Roubidoux, Marilyn; Thomas, Jerry A.; Osland, Jacqueline

2006-03-01

A new mammography tomosynthesis prototype system that acquires 21 projection images over a 60 degree angular range in approximately 8 seconds has been developed and characterized. Fast imaging sequences are facilitated by a high power tube and generator for faster delivery of the x-ray exposure and a high speed detector read-out. An enhanced a-Si/CsI flat panel digital detector provides greater DQE at low exposure, enabling tomo image sequence acquisitions at total patient dose levels between 150% and 200% of the dose of a standard mammographic view. For clinical scenarios where a single MLO tomographic acquisition per breast may replace the standard CC and MLO views, total tomosynthesis breast dose is comparable to or below the dose in standard mammography. The system supports co-registered acquisition of x-ray tomosynthesis and 3-D ultrasound data sets by incorporating an ultrasound transducer scanning system that flips into position above the compression paddle for the ultrasound exam. Initial images acquired with the system are presented.

Application of time-resolved shadowgraph imaging and computer analysis to study micrometer-scale response of superfluid helium

NASA Astrophysics Data System (ADS)

Sajjadi, Seyed; Buelna, Xavier; Eloranta, Jussi

2018-01-01

Application of inexpensive light emitting diodes as backlight sources for time-resolved shadowgraph imaging is demonstrated. The two light sources tested are able to produce light pulse sequences in the nanosecond and microsecond time regimes. After determining their time response characteristics, the diodes were applied to study the gas bubble formation around laser-heated copper nanoparticles in superfluid helium at 1.7 K and to determine the local cavitation bubble dynamics around fast moving metal micro-particles in the liquid. A convolutional neural network algorithm for analyzing the shadowgraph images by a computer is presented and the method is validated against the results from manual image analysis. The second application employed the red-green-blue light emitting diode source that produces light pulse sequences of the individual colors such that three separate shadowgraph frames can be recorded onto the color pixels of a charge-coupled device camera. Such an image sequence can be used to determine the moving object geometry, local velocity, and acceleration/deceleration. These data can be used to calculate, for example, the instantaneous Reynolds number for the liquid flow around the particle. Although specifically demonstrated for superfluid helium, the technique can be used to study the dynamic response of any medium that exhibits spatial variations in the index of refraction.

Ultrafast Brain MRI: Clinical Deployment and Comparison to Conventional Brain MRI at 3T.

PubMed

Prakkamakul, Supada; Witzel, Thomas; Huang, Susie; Boulter, Daniel; Borja, Maria J; Schaefer, Pamela; Rosen, Bruce; Heberlein, Keith; Ratai, Eva; Gonzalez, Gilberto; Rapalino, Otto

2016-09-01

To compare an ultrafast brain magnetic resonance imaging (MRI) protocol to the conventional protocol in motion-prone inpatient clinical settings. This retrospective study was HIPAA compliant and approved by the Institutional Review Board with waived inform consent. Fifty-nine inpatients (30 males, 29 females; mean age 55.1, range 23-93 years)who underwent 3-Tesla brain MRI using ultrafast and conventional protocols, both including five sequences, were included in the study. The total scan time for five ultrafast sequences was 4 minutes 59 seconds. The ideal conventional acquisition time was 10 minutes 32 seconds but the actual acquisition took 15-20 minutes. The average scan times for ultrafast localizers, T1-weighted, T2-weighted, fluid-attenuated inversion recovery (FLAIR), diffusion-weighted, T2*-weighted sequences were 14, 41, 62, 96, 80, 6 seconds, respectively. Two blinded neuroradiologists independently assessed three aspects: (1) image quality, (2) gray-white matter (GM-WM) differentiation, and (3) diagnostic concordance for the detection of six clinically relevant imaging findings. Wilcoxon signed-rank test was used to compare image quality and GM-WM scores. Interobserver reproducibility was calculated. The ultrafast T1-weighted sequence demonstrated significantly better image quality (P = .005) and GM-WM differentiation (P < .001) compared to the conventional sequence. There was high agreement (>85%) between both protocols for the detection of mass-like lesion, hemorrhage, diffusion restriction, WM FLAIR hyperintensities, subarachnoid FLAIR hyperintensities, and hydrocephalus. The ultrafast protocol achieved at least comparable image quality and high diagnostic concordance compared to the conventional protocol. This fast protocol can be a viable option to replace the conventional protocol in motion-prone inpatient clinical settings. Copyright © 2016 by the American Society of Neuroimaging.

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

BlochSolver: A GPU-optimized fast 3D MRI simulator for experimentally compatible pulse sequences

NASA Astrophysics Data System (ADS)

Kose, Ryoichi; Kose, Katsumi

2017-08-01

A magnetic resonance imaging (MRI) simulator, which reproduces MRI experiments using computers, has been developed using two graphic-processor-unit (GPU) boards (GTX 1080). The MRI simulator was developed to run according to pulse sequences used in experiments. Experiments and simulations were performed to demonstrate the usefulness of the MRI simulator for three types of pulse sequences, namely, three-dimensional (3D) gradient-echo, 3D radio-frequency spoiled gradient-echo, and gradient-echo multislice with practical matrix sizes. The results demonstrated that the calculation speed using two GPU boards was typically about 7 TFLOPS and about 14 times faster than the calculation speed using CPUs (two 18-core Xeons). We also found that MR images acquired by experiment could be reproduced using an appropriate number of subvoxels, and that 3D isotropic and two-dimensional multislice imaging experiments for practical matrix sizes could be simulated using the MRI simulator. Therefore, we concluded that such powerful MRI simulators are expected to become an indispensable tool for MRI research and development.

The Fast Spiral-SelMQC Technique for In Vivo MR Spectroscopic Imaging of Polyunsaturated Fatty Acids (PUFA) in Human Breast Tissue‡

PubMed Central

Zhu, He; Rubin, Denis; He, Qiuhong

2011-01-01

The Selective Multiple-Quantum Coherence Transfer (Sel-MQC) method has been applied to image polyunsaturated fatty acids (PUFA) distributions in human breast tissues in vivo for cancer detection, with complete suppression of the unwanted lipid and water signals in a single scan. The Cartesian k-space mapping of PUFA in vivo using the Sel-MQC CSI technique, however, requires excessive MR scan time. In this article, we report a fast Spiral-SelMQC sequence employing a rapid spiral k-space sampling scheme. The Spiral-SelMQC images of PUFA distribution in human breast were acquired using two-interleaved spirals on a 3T GE Signa MRI scanner. Approximately 160-fold reduction of acquisition time was observed as compared to the corresponding Sel-MQC CSI method with an equivalent number of scans, permitting acquisition of high-resolution PUFA images in minutes. The reconstructed Spiral-SelMQC PUFA images of human breast tissues achieved a sub-millimeter resolution of 0.54×0.54 or 0.63×0.63mm2/pixel for FOV = 14 or 16cm, respectively. The Spiral-SelMQC parameters for PUFA detection were optimized in 2D Sel-MQC experiments to suppress monounsaturated fatty acids (MUFA) and other lipid signals. The fast in vivo Spiral-SelMQC imaging method will be applied to study human breast cancer and other human diseases in extracranial organs. PMID:22028250

Thermographic measurements of high-speed metal cutting

NASA Astrophysics Data System (ADS)

Mueller, Bernhard; Renz, Ulrich

2002-03-01

Thermographic measurements of a high-speed cutting process have been performed with an infrared camera. To realize images without motion blur the integration times were reduced to a few microseconds. Since the high tool wear influences the measured temperatures a set-up has been realized which enables small cutting lengths. Only single images have been recorded because the process is too fast to acquire a sequence of images even with the frame rate of the very fast infrared camera which has been used. To expose the camera when the rotating tool is in the middle of the camera image an experimental set-up with a light barrier and a digital delay generator with a time resolution of 1 ns has been realized. This enables a very exact triggering of the camera at the desired position of the tool in the image. Since the cutting depth is between 0.1 and 0.2 mm a high spatial resolution was also necessary which was obtained by a special close-up lens allowing a resolution of app. 45 microns. The experimental set-up will be described and infrared images and evaluated temperatures of a titanium alloy and a carbon steel will be presented for cutting speeds up to 42 m/s.

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.

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.

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.

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.

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.

Determining Angular Frequency from Video with a Generalized Fast Fourier Transform

DTIC Science & Technology

2012-03-22

depicted in the first row, where n = (0, . . . , 7). It turns out the Mercedes - Benz shape in these images is rotating by a factor of 3(2π 8 ) radians in...a GST rotation example of data length N = 8 applied to the Mercedes - Benz shape. The first row is the original X sequence. Each column under that...rate of rotation by computing the sharpness of the sum. In Figure 2, GST(X[3]) appears to be the sharpest GST image; this confirms that the Mercedes

Pulseq-Graphical Programming Interface: Open source visual environment for prototyping pulse sequences and integrated magnetic resonance imaging algorithm development.

PubMed

Ravi, Keerthi Sravan; Potdar, Sneha; Poojar, Pavan; Reddy, Ashok Kumar; Kroboth, Stefan; Nielsen, Jon-Fredrik; Zaitsev, Maxim; Venkatesan, Ramesh; Geethanath, Sairam

2018-03-11

To provide a single open-source platform for comprehensive MR algorithm development inclusive of simulations, pulse sequence design and deployment, reconstruction, and image analysis. We integrated the "Pulseq" platform for vendor-independent pulse programming with Graphical Programming Interface (GPI), a scientific development environment based on Python. Our integrated platform, Pulseq-GPI, permits sequences to be defined visually and exported to the Pulseq file format for execution on an MR scanner. For comparison, Pulseq files using either MATLAB only ("MATLAB-Pulseq") or Python only ("Python-Pulseq") were generated. We demonstrated three fundamental sequences on a 1.5 T scanner. Execution times of the three variants of implementation were compared on two operating systems. In vitro phantom images indicate equivalence with the vendor supplied implementations and MATLAB-Pulseq. The examples demonstrated in this work illustrate the unifying capability of Pulseq-GPI. The execution times of all the three implementations were fast (a few seconds). The software is capable of user-interface based development and/or command line programming. The tool demonstrated here, Pulseq-GPI, integrates the open-source simulation, reconstruction and analysis capabilities of GPI Lab with the pulse sequence design and deployment features of Pulseq. Current and future work includes providing an ISMRMRD interface and incorporating Specific Absorption Ratio and Peripheral Nerve Stimulation computations. Copyright © 2018 Elsevier Inc. All rights reserved.

Balanced Steady-State Free Precession (bSSFP) from an effective field perspective: Application to the detection of chemical exchange (bSSFPX).

PubMed

Zhang, Shu; Liu, Zheng; Grant, Aaron; Keupp, Jochen; Lenkinski, Robert E; Vinogradov, Elena

2017-02-01

Chemical exchange saturation transfer (CEST) is a novel contrast mechanism and it is gaining increasing popularity as many promising applications have been proposed and investigated. Fast and quantitative CEST imaging techniques are further needed in order to increase the applicability of CEST for clinical use as well as to derive quantitative physiological and biological information. Steady-state methods for fast CEST imaging have been reported recently. Here, we observe that an extreme case of these methods is a balanced steady-state free precession (bSSFP) sequence. The bSSFP in itself is sensitive to the exchange processes; hence, no additional saturation or preparation is needed for CEST-like data acquisition. The bSSFP experiment can be regarded as observation during saturation, without separate saturation and acquisition modules as used in standard CEST and similar experiments. One of the differences from standard CEST methods is that the bSSFP spectrum is an XY-spectrum not a Z-spectrum. As the first proof-of-principle step, we have implemented the steady-state bSSFP sequence for chemical exchange detection (bSSFPX) and verified its feasibility in phantom studies. These studies have shown that bSSFPX can achieve exchange-mediated contrast comparable to the standard CEST experiment. Therefore, the bSSFPX method has a potential for fast and quantitative CEST data acquisition. Copyright © 2016 Elsevier Inc. All rights reserved.

Chemical Exchange Saturation Transfer (CEST) MR Technique for Liver Imaging at 3.0 Tesla: an Evaluation of Different Offset Number and an After-Meal and Over-Night-Fast Comparison.

PubMed

Deng, Min; Chen, Shu-Zhong; Yuan, Jing; Chan, Queenie; Zhou, Jinyuan; Wáng, Yì-Xiáng J

2016-04-01

This study seeks to explore whether chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) can detect liver composition changes between after-meal and over-night-fast statuses. Fifteen healthy volunteers were scanned on a 3.0-T human MRI scanner in the evening 1.5-2 h after dinner and in the morning after over-night (12-h) fasting. Among them, seven volunteers were scanned twice to assess the scan-rescan reproducibility. Images were acquired at offsets (n = 41, increment = 0.25 ppm) from -5 to 5 ppm using a turbo spin echo (TSE) sequence with a continuous rectangular saturation pulse. Amide proton transfer-weighted (APTw) and GlycoCEST signals were quantified with the asymmetric magnetization transfer ratio (MTRasym) at 3.5 ppm and the total MTRasym integrated from 0.5 to 1.5 ppm from the corrected Z-spectrum, respectively. To explore scan time reduction, CEST images were reconstructed using 31 offsets (with 20% time reduction) and 21 offsets (with 40% time reduction), respectively. For reproducibility, GlycoCEST measurements in 41 offsets showed the smallest scan-rescan mean measurements variability, indicated by the lowest mean difference of -0.049% (95% limits of agreement, -0.209 to 0.111%); for APTw, the smallest mean difference was found to be 0.112% (95% limits of agreement, -0.698 to 0.921%) in 41 offsets. Compared with after-meal, both GlycoCEST measurement and APTw measurement under different offset number decreased after 12-h fasting. However, as the offsets number decreased (41 offsets vs. 31 offsets vs. 21 offsets), GlycoCEST map and APTw map became more heterogeneous and noisier. Our results show that CEST liver imaging at 3.0 T has high sensitivity for fasting.

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.

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.

Carr-Purcell-Meiboom-Gill imaging of prostate cancer: quantitative T2 values for cancer discrimination.

PubMed

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

2009-05-01

Quantitative, apparent T(2) 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 T(2) 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 x 1.1 x 4 mm(3) was obtained in 10.7 min, resulting in data sets suitable for generating high-quality images with variable T(2)-weighting and for evaluating quantitative T(2) 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 T(1)- and T(2)-weighted signal intensities and available histopathology reports, yielded significantly (P<.0001) longer apparent T(2) 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 T(2)-weighted fast spin echo (FSE) imaging alone, including quantitative T(2) values for cancer discrimination as well as proton density maps without the point spread function degradation associated with short effective echo time FSE sequences.

Hybrid cardiac imaging with MR-CAT scan: a feasibility study.

PubMed

Hillenbrand, C; Sandstede, J; Pabst, T; Hahn, D; Haase, A; Jakob, P M

2000-06-01

We demonstrate the feasibility of a new versatile hybrid imaging concept, the combined acquisition technique (CAT), for cardiac imaging. The cardiac CAT approach, which combines new methodology with existing technology, essentially integrates fast low-angle shot (FLASH) and echoplanar imaging (EPI) modules in a sequential fashion, whereby each acquisition module is employed with independently optimized imaging parameters. One important CAT sequence optimization feature is the ability to use different bandwidths for different acquisition modules. Twelve healthy subjects were imaged using three cardiac CAT acquisition strategies: a) CAT was used to reduce breath-hold duration times while maintaining constant spatial resolution; b) CAT was used to increase spatial resolution in a given breath-hold time; and c) single-heart beat CAT imaging was performed. The results obtained demonstrate the feasibility of cardiac imaging using the CAT approach and the potential of this technique to accelerate the imaging process with almost conserved image quality. Copyright 2000 Wiley-Liss, Inc.

An algorithm to compute the sequency ordered Walsh transform

NASA Technical Reports Server (NTRS)

Larsen, H.

1976-01-01

A fast sequency-ordered Walsh transform algorithm is presented; this sequency-ordered fast transform is complementary to the sequency-ordered fast Walsh transform introduced by Manz (1972) and eliminating gray code reordering through a modification of the basic fast Hadamard transform structure. The new algorithm retains the advantages of its complement (it is in place and is its own inverse), while differing in having a decimation-in time structure, accepting data in normal order, and returning the coefficients in bit-reversed sequency order. Applications include estimation of Walsh power spectra for a random process, sequency filtering and computing logical autocorrelations, and selective bit reversing.

Comparison of qualitative and quantitative evaluation of diffusion-weighted MRI and chemical-shift imaging in the differentiation of benign and malignant vertebral body fractures.

PubMed

Geith, Tobias; Schmidt, Gerwin; Biffar, Andreas; Dietrich, Olaf; Dürr, Hans Roland; Reiser, Maximilian; Baur-Melnyk, Andrea

2012-11-01

The objective of our study was to compare the diagnostic value of qualitative diffusion-weighted imaging (DWI), quantitative DWI, and chemical-shift imaging in a single prospective cohort of patients with acute osteoporotic and malignant vertebral fractures. The study group was composed of patients with 26 osteoporotic vertebral fractures (18 women, eight men; mean age, 69 years; age range, 31 years 6 months to 86 years 2 months) and 20 malignant vertebral fractures (nine women, 11 men; mean age, 63.4 years; age range, 24 years 8 months to 86 years 4 months). T1-weighted, STIR, and T2-weighted sequences were acquired at 1.5 T. A DW reverse fast imaging with steady-state free precession (PSIF) sequence at different delta values was evaluated qualitatively. A DW echo-planar imaging (EPI) sequence and a DW single-shot turbo spin-echo (TSE) sequence at different b values were evaluated qualitatively and quantitatively using the apparent diffusion coefficient. Opposed-phase sequences were used to assess signal intensity qualitatively. The signal loss between in- and opposed-phase images was determined quantitatively. Two-tailed Fisher exact test, Mann-Whitney test, and receiver operating characteristic analysis were performed. Sensitivities, specificities, and accuracies were determined. Qualitative DW-PSIF imaging (delta = 3 ms) showed the best performance for distinguishing between benign and malignant fractures (sensitivity, 100%; specificity, 88.5%; accuracy, 93.5%). Qualitative DW-EPI (b = 50 s/mm(2) [p = 1.00]; b = 250 s/mm(2) [p = 0.50]) and DW single-shot TSE imaging (b = 100 s/mm(2) [p = 1.00]; b = 250 s/mm(2) [p = 0.18]; b = 400 s/mm(2) [p = 0.18]; b = 600 s/mm(2) [p = 0.39]) did not indicate significant differences between benign and malignant fractures. DW-EPI using a b value of 500 s/mm(2) (p = 0.01) indicated significant differences between benign and malignant vertebral fractures. Quantitative DW-EPI (p = 0.09) and qualitative opposed-phase imaging (p = 0.06) did not exhibit significant differences, quantitative DW single-shot TSE imaging (p = 0.002) and quantitative chemical-shift imaging (p = 0.01) showed significant differences between benign and malignant fractures. The DW-PSIF sequence (delta = 3 ms) had the highest accuracy in differentiating benign from malignant vertebral fractures. Quantitative chemical-shift imaging and quantitative DW single-shot TSE imaging had a lower accuracy than DW-PSIF imaging because of a large overlap. Qualitative assessment of opposed-phase, DW-EPI, and DW single-shot TSE sequences and quantitative assessment of the DW-EPI sequence were not suitable for distinguishing between benign and malignant vertebral fractures.

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.

Evaluation of Image Quality in Three-dimensional Fat-suppressed T1-weighted Images with Fast Acquisition Mode for Upper Abdomen.

PubMed

Saito, Shigeyoshi; Tanaka, Keiko; Tarewaki, Hiroyuki; Koyama, Yoshihiro; Hashido, Takashi

2016-01-01

We compared the uniformity of fat-suppression and image quality using three-dimensional fat-suppressed T 1 -weighted gradient-echo sequences that are liver acquisition with volume acceleration (LAVA) and Turbo-LAVA at 3.0T-MRI. The subjects were seven patients with liver disease (mean age, 66.7±8.2 years). The axial slices of two LAVA sequences were used for the comparison of the uniformity of fat-suppression and image quality at a region-of-interest (ROI) of the liver dome, the porta, and the renal hilum. To yield a quantitative measurement of the uniformity of fat suppression, the percentage standard deviation (%SD) was calculated by comparing two sequences. For image signal to noise ratio (SNR), the contrast between the liver and fat (C liver-fat ), and the liver and muscle (C liver-muscle ), the other ROIs were placed in the superficial fat, liver, spleen, pancreas, and muscle. The %SD in Turbo-LAVA (28.1±16.8%) was lower than that in LAVA (41.5±13.4%). The SNRs in Turbo-LAVA (17.8±4.1 [liver], 12.5±3.0 [pancreas], 14.7±1.6 [spleen], 8.2±3.5 [fat]) were lower than those in LAVA (20.9±6.1 [liver], 16.8±4.1 [pancreas], 17.4±2.4 [spleen], 12.0±4.5 [fat]). While, the C liver-fat in the Turbo-LAVA (0.72±0.06) was significantly higher than that in LAVA (0.59±0.07). Turbo-LAVA sequence offers superior and more homogenous fat-suppression in comparison to LAVA sequence.

A fast one-chip event-preprocessor and sequencer for the Simbol-X Low Energy Detector

NASA Astrophysics Data System (ADS)

Schanz, T.; Tenzer, C.; Maier, D.; Kendziorra, E.; Santangelo, A.

2010-12-01

We present an FPGA-based digital camera electronics consisting of an Event-Preprocessor (EPP) for on-board data preprocessing and a related Sequencer (SEQ) to generate the necessary signals to control the readout of the detector. The device has been originally designed for the Simbol-X low energy detector (LED). The EPP operates on 64×64 pixel images and has a real-time processing capability of more than 8000 frames per second. The already working releases of the EPP and the SEQ are now combined into one Digital-Camera-Controller-Chip (D3C).

Cardiovascular magnetic resonance physics for clinicians: part II

PubMed Central

2012-01-01

This is the second of two reviews that is intended to cover the essential aspects of cardiovascular magnetic resonance (CMR) physics in a way that is understandable and relevant to clinicians using CMR in their daily practice. Starting with the basic pulse sequences and contrast mechanisms described in part I, it briefly discusses further approaches to accelerate image acquisition. It then continues by showing in detail how the contrast behaviour of black blood fast spin echo and bright blood cine gradient echo techniques can be modified by adding rf preparation pulses to derive a number of more specialised pulse sequences. The simplest examples described include T2-weighted oedema imaging, fat suppression and myocardial tagging cine pulse sequences. Two further important derivatives of the gradient echo pulse sequence, obtained by adding preparation pulses, are used in combination with the administration of a gadolinium-based contrast agent for myocardial perfusion imaging and the assessment of myocardial tissue viability using a late gadolinium enhancement (LGE) technique. These two imaging techniques are discussed in more detail, outlining the basic principles of each pulse sequence, the practical steps required to achieve the best results in a clinical setting and, in the case of perfusion, explaining some of the factors that influence current approaches to perfusion image analysis. The key principles of contrast-enhanced magnetic resonance angiography (CE-MRA) are also explained in detail, especially focusing on timing of the acquisition following contrast agent bolus administration, and current approaches to achieving time resolved MRA. Alternative MRA techniques that do not require the use of an endogenous contrast agent are summarised, and the specialised pulse sequence used to image the coronary arteries, using respiratory navigator gating, is described in detail. The article concludes by explaining the principle behind phase contrast imaging techniques which create images that represent the phase of the MR signal rather than the magnitude. It is shown how this principle can be used to generate velocity maps by designing gradient waveforms that give rise to a relative phase change that is proportional to velocity. Choice of velocity encoding range and key pitfalls in the use of this technique are discussed. PMID:22995744

Quantifying cortical surface harmonic deformation with stereovision during open cranial neurosurgery

NASA Astrophysics Data System (ADS)

Ji, Songbai; Fan, Xiaoyao; Roberts, David W.; Paulsen, Keith D.

2012-02-01

Cortical surface harmonic motion during open cranial neurosurgery is well observed in image-guided neurosurgery. Recently, we quantified cortical surface deformation noninvasively with synchronized blood pressure pulsation (BPP) from a sequence of stereo image pairs using optical flow motion tracking. With three subjects, we found the average cortical surface displacement can reach more than 1 mm and in-plane principal strains of up to 7% relative to the first image pair. In addition, the temporal changes in deformation and strain were in concert with BPP and patient respiration [1]. However, because deformation was essentially computed relative to an arbitrary reference, comparing cortical surface deformation at different times was not possible. In this study, we extend the technique developed earlier by establishing a more reliable reference profile of the cortical surface for each sequence of stereo image acquisitions. Specifically, fast Fourier transform (FFT) was applied to the dynamic cortical surface deformation, and the fundamental frequencies corresponding to patient respiration and BPP were identified, which were used to determine the number of image acquisitions for use in averaging cortical surface images. This technique is important because it potentially allows in vivo characterization of soft tissue biomechanical properties using intraoperative stereovision and motion tracking.

Neurovascular Study of the Trigeminal Nerve at 3 T MRI

PubMed Central

Gonzalez, Nadia; Muñoz, Alexandra; Bravo, Fernando; Sarroca, Daniel; Morales, Carlos

2015-01-01

This study aimed to show a novel visualization method to investigate neurovascular compression of the trigeminal nerve (TN) using a volume-rendering fusion imaging technique of 3D fast imaging employing steady-state acquisition (3D FIESTA) and coregistered 3D time of flight MR angiography (3D TOF MRA) sequences, which we called “neurovascular study of the trigeminal nerve”. We prospectively studied 30 patients with unilateral trigeminal neuralgia (TN) and 50 subjects without symptoms of TN (control group), on a 3 Tesla scanner. All patients were assessed using 3D FIESTA and 3D TOF MRA sequences centered on the pons, as well as a standard brain protocol including axial T1, T2, FLAIR and GRE sequences to exclude other pathologies that could cause TN. Post-contrast T1-weighted sequences were also performed. All cases showing arterial imprinting on the trigeminal nerve (n = 11) were identified on the ipsilateral side of the pain. No significant relationship was found between the presence of an artery in contact with the trigeminal nerve and TN. Eight cases were found showing arterial contact on the ipsilateral side of the pain and five cases of arterial contact on the contralateral side. The fusion imaging technique of 3D FIESTA and 3D TOF MRA sequences, combining the high anatomical detail provided by the 3D FIESTA sequence with the 3D TOF MRA sequence and its capacity to depict arterial structures, results in a tool that enables quick and efficient visualization and assessment of the relationship between the trigeminal nerve and the neighboring vascular structures. PMID:25924169

A Low-Cost PC-Based Image Workstation for Dynamic Interactive Display of Three-Dimensional Anatomy

NASA Astrophysics Data System (ADS)

Barrett, William A.; Raya, Sai P.; Udupa, Jayaram K.

1989-05-01

A system for interactive definition, automated extraction, and dynamic interactive display of three-dimensional anatomy has been developed and implemented on a low-cost PC-based image workstation. An iconic display is used for staging predefined image sequences through specified increments of tilt and rotation over a solid viewing angle. Use of a fast processor facilitates rapid extraction and rendering of the anatomy into predefined image views. These views are formatted into a display matrix in a large image memory for rapid interactive selection and display of arbitrary spatially adjacent images within the viewing angle, thereby providing motion parallax depth cueing for efficient and accurate perception of true three-dimensional shape, size, structure, and spatial interrelationships of the imaged anatomy. The visual effect is that of holding and rotating the anatomy in the hand.

Onboard Image Registration from Invariant Features

NASA Technical Reports Server (NTRS)

Wang, Yi; Ng, Justin; Garay, Michael J.; Burl, Michael C

2008-01-01

This paper describes a feature-based image registration technique that is potentially well-suited for onboard deployment. The overall goal is to provide a fast, robust method for dynamically combining observations from multiple platforms into sensors webs that respond quickly to short-lived events and provide rich observations of objects that evolve in space and time. The approach, which has enjoyed considerable success in mainstream computer vision applications, uses invariant SIFT descriptors extracted at image interest points together with the RANSAC algorithm to robustly estimate transformation parameters that relate one image to another. Experimental results for two satellite image registration tasks are presented: (1) automatic registration of images from the MODIS instrument on Terra to the MODIS instrument on Aqua and (2) automatic stabilization of a multi-day sequence of GOES-West images collected during the October 2007 Southern California wildfires.

Implications of oxidative stress in the brain plasticity originated by fasting: a BOLD-fMRI study.

PubMed

Belaïch, Rachida; Boujraf, Saïd; Benzagmout, Mohammed; Magoul, Rabia; Maaroufi, Mustapha; Tizniti, Siham

2017-11-01

The goal of this study was assessing the intermittent fasting effect on brain plasticity and oxidative stress (OS) using blood-oxygenation-level dependent (BOLD)-functional magnetic resonance image (fMRI) approach. Evidences of physiological and molecular phenomena involved in this process are discussed and compared to reported literature. Six fully healthy male non-smokers volunteered in this study. All volunteers were right handed, and have an equilibrated, consistent and healthy daily nutritional habit, and a healthy lifestyle. Participants were allowed consuming food during evening and night time while fasting with self-prohibiting food and liquids during 14 hours/day from sunrise to sunset. All participants underwent identical brain BOLD-fMRI protocol. The images were acquired in the Department of Radiology and Clinical Imaging of the University Hospital of Fez, Fez, Morocco. The anatomical brain and BOLD-fMRIs were acquired using a 1.5-Tesla scanner (Signa, General Electric, Milwaukee, United States). BOLD-fMRI image acquisition was done using single-shot gradient echo echo-planer imaging sequence. BOLD-fMRI paradigm consisted of the motor task where volunteers were asked to perform finger taping of the right hand. Two BOLD-fMRI scan sessions were performed, the first one between the 5th and 10th days preceding the start of fasting and the second between days 25th and 28th of the fasting month. All sessions were performed between 3:30 PM and 5:30 PM. Although individual maps were originated from different individual participants, they cover the same anatomic area in each case. Image processing and statistical analysis were conducted with Statistical Parameter Mapping version 8 (2008, Welcome Department of Cognitive Neurology, London UK). The maximal BOLD signal changes were calculated for each subject in the motor area M1; Activation maps were calculated and overlaid on the anatomical images. Group analysis of the data was performed, and the average volume and the maximum intensity of BOLD signal in the activated area M1 was determined for all studied volunteers. The current study allowed measuring regional brain volumes and neural network activity before and during an extended period of fasting using BOLD-fMRI. This demonstrated and confirmed the impact of fasting on human brain structure and function. Further studies are required to elucidate mechanisms and enable direct inference of a diet-induced OS effect on the brain.

POCS-based reconstruction of multiplexed sensitivity encoded MRI (POCSMUSE): a general algorithm for reducing motion-related artifacts

PubMed Central

Chu, Mei-Lan; Chang, Hing-Chiu; Chung, Hsiao-Wen; Truong, Trong-Kha; Bashir, Mustafa R.; Chen, Nan-kuei

2014-01-01

Purpose A projection onto convex sets reconstruction of multiplexed sensitivity encoded MRI (POCSMUSE) is developed to reduce motion-related artifacts, including respiration artifacts in abdominal imaging and aliasing artifacts in interleaved diffusion weighted imaging (DWI). Theory Images with reduced artifacts are reconstructed with an iterative POCS procedure that uses the coil sensitivity profile as a constraint. This method can be applied to data obtained with different pulse sequences and k-space trajectories. In addition, various constraints can be incorporated to stabilize the reconstruction of ill-conditioned matrices. Methods The POCSMUSE technique was applied to abdominal fast spin-echo imaging data, and its effectiveness in respiratory-triggered scans was evaluated. The POCSMUSE method was also applied to reduce aliasing artifacts due to shot-to-shot phase variations in interleaved DWI data corresponding to different k-space trajectories and matrix condition numbers. Results Experimental results show that the POCSMUSE technique can effectively reduce motion-related artifacts in data obtained with different pulse sequences, k-space trajectories and contrasts. Conclusion POCSMUSE is a general post-processing algorithm for reduction of motion-related artifacts. It is compatible with different pulse sequences, and can also be used to further reduce residual artifacts in data produced by existing motion artifact reduction methods. PMID:25394325

MRI technique for the snapshot imaging of quantitative velocity maps using RARE

NASA Astrophysics Data System (ADS)

Shiko, G.; Sederman, A. J.; Gladden, L. F.

2012-03-01

A quantitative PGSE-RARE pulse sequence was developed and successfully applied to the in situ dissolution of two pharmaceutical formulations dissolving over a range of timescales. The new technique was chosen over other existing fast velocity imaging techniques because it is T2 weighted, not T2∗ weighted, and is, therefore, robust for imaging time-varying interfaces and flow in magnetically heterogeneous systems. The complex signal was preserved intact by separating odd and even echoes to obtain two phase maps which are then averaged in post-processing. Initially, the validity of the technique was shown when imaging laminar flow in a pipe. Subsequently, the dissolution of two drugs was followed in situ, where the technique enables the imaging and quantification of changes in the form of the tablet and the flow field surrounding it at high spatial and temporal resolution. First, the complete 3D velocity field around an eroding salicylic acid tablet was acquired at a resolution of 98 × 49 μm2, within 20 min, and monitored over ˜13 h. The tablet was observed to experience a heterogeneous flow field and, hence a heterogeneous shear field, which resulted in the non-symmetric erosion of the tablet. Second, the dissolution of a fast dissolving immediate release tablet was followed using one-shot 2D velocity images acquired every 5.2 s at a resolution of 390 × 390 μm2. The quantitative nature of the technique and fast acquisition times provided invaluable information on the dissolution behaviour of this tablet, which had not been attainable previously with conventional quantitative MRI techniques.

Comparison of three-dimensional visualization techniques for depicting the scala vestibuli and scala tympani of the cochlea by using high-resolution MR imaging.

PubMed

Hans, P; Grant, A J; Laitt, R D; Ramsden, R T; Kassner, A; Jackson, A

1999-08-01

Cochlear implantation requires introduction of a stimulating electrode array into the scala vestibuli or scala tympani. Although these structures can be separately identified on many high-resolution scans, it is often difficult to ascertain whether these channels are patent throughout their length. The aim of this study was to determine whether an optimized combination of an imaging protocol and a visualization technique allows routine 3D rendering of the scala vestibuli and scala tympani. A submillimeter T2 fast spin-echo imaging sequence was designed to optimize the performance of 3D visualization methods. The spatial resolution was determined experimentally using primary images and 3D surface and volume renderings from eight healthy subjects. These data were used to develop the imaging sequence and to compare the quality and signal-to-noise dependency of four data visualization algorithms: maximum intensity projection, ray casting with transparent voxels, ray casting with opaque voxels, and isosurface rendering. The ability of these methods to produce 3D renderings of the scala tympani and scala vestibuli was also examined. The imaging technique was used in five patients with sensorineural deafness. Visualization techniques produced optimal results in combination with an isotropic volume imaging sequence. Clinicians preferred the isosurface-rendered images to other 3D visualizations. Both isosurface and ray casting displayed the scala vestibuli and scala tympani throughout their length. Abnormalities were shown in three patients, and in one of these, a focal occlusion of the scala tympani was confirmed at surgery. Three-dimensional images of the scala vestibuli and scala tympani can be routinely produced. The combination of an MR sequence optimized for use with isosurface rendering or ray-casting algorithms can produce 3D images with greater spatial resolution and anatomic detail than has been possible previously.

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.

Tumour auto-contouring on 2d cine MRI for locally advanced lung cancer: A comparative study.

PubMed

Fast, Martin F; Eiben, Björn; Menten, Martin J; Wetscherek, Andreas; Hawkes, David J; McClelland, Jamie R; Oelfke, Uwe

2017-12-01

Radiotherapy guidance based on magnetic resonance imaging (MRI) is currently becoming a clinical reality. Fast 2d cine MRI sequences are expected to increase the precision of radiation delivery by facilitating tumour delineation during treatment. This study compares four auto-contouring algorithms for the task of delineating the primary tumour in six locally advanced (LA) lung cancer patients. Twenty-two cine MRI sequences were acquired using either a balanced steady-state free precession or a spoiled gradient echo imaging technique. Contours derived by the auto-contouring algorithms were compared against manual reference contours. A selection of eight image data sets was also used to assess the inter-observer delineation uncertainty. Algorithmically derived contours agreed well with the manual reference contours (median Dice similarity index: ⩾0.91). Multi-template matching and deformable image registration performed significantly better than feature-driven registration and the pulse-coupled neural network (PCNN). Neither MRI sequence nor image orientation was a conclusive predictor for algorithmic performance. Motion significantly degraded the performance of the PCNN. The inter-observer variability was of the same order of magnitude as the algorithmic performance. Auto-contouring of tumours on cine MRI is feasible in LA lung cancer patients. Despite large variations in implementation complexity, the different algorithms all have relatively similar performance. Copyright © 2017 The Author(s). Published by Elsevier B.V. All rights reserved.

Methods for 2-D and 3-D Endobronchial Ultrasound Image Segmentation.

PubMed

Zang, Xiaonan; Bascom, Rebecca; Gilbert, Christopher; Toth, Jennifer; Higgins, William

2016-07-01

Endobronchial ultrasound (EBUS) is now commonly used for cancer-staging bronchoscopy. Unfortunately, EBUS is challenging to use and interpreting EBUS video sequences is difficult. Other ultrasound imaging domains, hampered by related difficulties, have benefited from computer-based image-segmentation methods. Yet, so far, no such methods have been proposed for EBUS. We propose image-segmentation methods for 2-D EBUS frames and 3-D EBUS sequences. Our 2-D method adapts the fast-marching level-set process, anisotropic diffusion, and region growing to the problem of segmenting 2-D EBUS frames. Our 3-D method builds upon the 2-D method while also incorporating the geodesic level-set process for segmenting EBUS sequences. Tests with lung-cancer patient data showed that the methods ran fully automatically for nearly 80% of test cases. For the remaining cases, the only user-interaction required was the selection of a seed point. When compared to ground-truth segmentations, the 2-D method achieved an overall Dice index = 90.0% ±4.9%, while the 3-D method achieved an overall Dice index = 83.9 ± 6.0%. In addition, the computation time (2-D, 0.070 s/frame; 3-D, 0.088 s/frame) was two orders of magnitude faster than interactive contour definition. Finally, we demonstrate the potential of the methods for EBUS localization in a multimodal image-guided bronchoscopy system.

Non-mydriatic video ophthalmoscope to measure fast temporal changes of the human retina

NASA Astrophysics Data System (ADS)

Tornow, Ralf P.; Kolář, Radim; Odstrčilík, Jan

2015-07-01

The analysis of fast temporal changes of the human retina can be used to get insight to normal physiological behavior and to detect pathological deviations. This can be important for the early detection of glaucoma and other eye diseases. We developed a small, lightweight, USB powered video ophthalmoscope that allows taking video sequences of the human retina with at least 25 frames per second without dilating the pupil. Short sequences (about 10 s) of the optic nerve head (20° x 15°) are recorded from subjects and registered offline using two-stage process (phase correlation and Lucas-Kanade approach) to compensate for eye movements. From registered video sequences, different parameters can be calculated. Two applications are described here: measurement of (i) cardiac cycle induced pulsatile reflection changes and (ii) eye movements and fixation pattern. Cardiac cycle induced pulsatile reflection changes are caused by changing blood volume in the retina. Waveform and pulse parameters like amplitude and rise time can be measured in any selected areas within the retinal image. Fixation pattern ΔY(ΔX) can be assessed from eye movements during video acquisition. The eye movements ΔX[t], ΔY[t] are derived from image registration results with high temporal (40 ms) and spatial (1,86 arcmin) resolution. Parameters of pulsatile reflection changes and fixation pattern can be affected in beginning glaucoma and the method described here may support early detection of glaucoma and other eye disease.

Fast CT-PRESS-based spiral chemical shift imaging at 3 Tesla.

PubMed

Mayer, Dirk; Kim, Dong-Hyun; Adalsteinsson, Elfar; Spielman, Daniel M

2006-05-01

A new sequence is presented that combines constant-time point-resolved spectroscopy (CT-PRESS) with fast spiral chemical shift imaging. It allows the acquisition of multivoxel spectra without line splitting with a minimum total measurement time of less than 5 min for a field of view of 24 cm and a nominal 1.5x1.5-cm2 in-plane resolution. Measurements were performed with 17 CS encoding steps in t1 (Deltat1=12.8 ms) and an average echo time of 151 ms, which was determined by simulating the CT-PRESS experiment for the spin systems of glutamate (Glu) and myo-inositol (mI). Signals from N-acetyl-aspartate, total creatine, choline-containing compounds (Cho), Glu, and mI were detected in a healthy volunteer with no or only minor baseline distortions within 14 min on a 3 T MR scanner. Copyright (c) 2006 Wiley-Liss, Inc.

Comparing light sensitivity, linearity and step response of electronic cameras for ophthalmology.

PubMed

Kopp, O; Markert, S; Tornow, R P

2002-01-01

To develop and test a procedure to measure and compare light sensitivity, linearity and step response of electronic cameras. The pixel value (PV) of digitized images as a function of light intensity (I) was measured. The sensitivity was calculated from the slope of the P(I) function, the linearity was estimated from the correlation coefficient of this function. To measure the step response, a short sequence of images was acquired. During acquisition, a light source was switched on and off using a fast shutter. The resulting PV was calculated for each video field of the sequence. A CCD camera optimized for the near-infrared (IR) spectrum showed the highest sensitivity for both, visible and IR light. There are little differences in linearity. The step response depends on the procedure of integration and read out.

The Role of Nonlinear Gradients in Parallel Imaging: A k-Space Based Analysis.

PubMed

Galiana, Gigi; Stockmann, Jason P; Tam, Leo; Peters, Dana; Tagare, Hemant; Constable, R Todd

2012-09-01

Sequences that encode the spatial information of an object using nonlinear gradient fields are a new frontier in MRI, with potential to provide lower peripheral nerve stimulation, windowed fields of view, tailored spatially-varying resolution, curved slices that mirror physiological geometry, and, most importantly, very fast parallel imaging with multichannel coils. The acceleration for multichannel images is generally explained by the fact that curvilinear gradient isocontours better complement the azimuthal spatial encoding provided by typical receiver arrays. However, the details of this complementarity have been more difficult to specify. We present a simple and intuitive framework for describing the mechanics of image formation with nonlinear gradients, and we use this framework to review some the main classes of nonlinear encoding schemes.

Echo-Planar Imaging for a 9.4 Tesla Vertical-Bore Superconducting Magnet Using an Unshielded Gradient Coil.

PubMed

Kodama, Nao; Kose, Katsumi

2016-10-11

Echo-planar imaging (EPI) sequences were developed for a 9.4 Tesla vertical standard bore (~54 mm) superconducting magnet using an unshielded gradient coil optimized for live mice imaging and a data correction technique with reference scans. Because EPI requires fast switching of intense magnetic field gradients, eddy currents were induced in the surrounding metallic materials, e.g., the room temperature bore, and this produced serious artifacts on the EPI images. We solved the problem using an unshielded gradient coil set of proper size (outer diameter = 39 mm, inner diameter = 32 mm) with time control of the current rise and reference scans. The obtained EPI images of a phantom and a plant sample were almost artifact-free and demonstrated the promise of our approach.

Image Navigation and Registration Performance Assessment Evaluation Tools for GOES-R ABI and GLM

NASA Technical Reports Server (NTRS)

Houchin, Scott; Porter, Brian; Graybill, Justin; Slingerland, Philip

2017-01-01

The GOES-R Flight Project has developed an Image Navigation and Registration (INR) Performance Assessment Tool Set (IPATS) for measuring Advanced Baseline Imager (ABI) and Geostationary Lightning Mapper (GLM) INR performance metrics in the post-launch period for performance evaluation and long term monitoring. IPATS utilizes a modular algorithmic design to allow user selection of data processing sequences optimized for generation of each INR metric. This novel modular approach minimizes duplication of common processing elements, thereby maximizing code efficiency and speed. Fast processing is essential given the large number of sub-image registrations required to generate INR metrics for the many images produced over a 24 hour evaluation period. This paper describes the software design and implementation of IPATS and provides preliminary test results.

Acceleration techniques and their impact on arterial input function sampling: Non-accelerated versus view-sharing and compressed sensing sequences.

PubMed

Benz, Matthias R; Bongartz, Georg; Froehlich, Johannes M; Winkel, David; Boll, Daniel T; Heye, Tobias

2018-07-01

The aim was to investigate the variation of the arterial input function (AIF) within and between various DCE MRI sequences. A dynamic flow-phantom and steady signal reference were scanned on a 3T MRI using fast low angle shot (FLASH) 2d, FLASH3d (parallel imaging factor (P) = P0, P2, P4), volumetric interpolated breath-hold examination (VIBE) (P = P0, P3, P2 × 2, P2 × 3, P3 × 2), golden-angle radial sparse parallel imaging (GRASP), and time-resolved imaging with stochastic trajectories (TWIST). Signal over time curves were normalized and quantitatively analyzed by full width half maximum (FWHM) measurements to assess variation within and between sequences. The coefficient of variation (CV) for the steady signal reference ranged from 0.07-0.8%. The non-accelerated gradient echo FLASH2d, FLASH3d, and VIBE sequences showed low within sequence variation with 2.1%, 1.0%, and 1.6%. The maximum FWHM CV was 3.2% for parallel imaging acceleration (VIBE P2 × 3), 2.7% for GRASP and 9.1% for TWIST. The FWHM CV between sequences ranged from 8.5-14.4% for most non-accelerated/accelerated gradient echo sequences except 6.2% for FLASH3d P0 and 0.3% for FLASH3d P2; GRASP FWHM CV was 9.9% versus 28% for TWIST. MRI acceleration techniques vary in reproducibility and quantification of the AIF. Incomplete coverage of the k-space with TWIST as a representative of view-sharing techniques showed the highest variation within sequences and might be less suited for reproducible quantification of the AIF. Copyright © 2018 Elsevier B.V. All rights reserved.

Substitute CT generation from a single ultra short time echo MRI sequence: preliminary study

NASA Astrophysics Data System (ADS)

Ghose, Soumya; Dowling, Jason A.; Rai, Robba; Liney, Gary P.

2017-04-01

In MR guided radiation therapy planning both MR and CT images for a patient are acquired and co-registered to obtain a tissue specific HU map. Generation of the HU map directly from the MRI would eliminate the CT acquisition and may improve radiation therapy planning. In this preliminary study of substitute CT (sCT) generation, two porcine leg phantoms were scanned using a 3D ultrashort echo time (PETRA) sequence and co-registered to corresponding CT images to build tissue specific regression models. The model was created from one co-registered CT-PETRA pair to generate the sCT for the other PETRA image. An expectation maximization based clustering was performed on the co-registered PETRA image to identify the soft tissues, dense bone and air class membership probabilities. A tissue specific non linear regression model was built from one registered CT-PETRA pair dataset to predict the sCT of the second PETRA image in a two-fold cross validation schema. A complete substitute CT is generated in 3 min. The mean absolute HU error for air was 0.3 HU, bone was 95 HU, fat was 30 HU and for muscle it was 10 HU. The mean surface reconstruction error for the bone was 1.3 mm. The PETRA sequence enabled a low mean absolute surface distance for the bone and a low HU error for other classes. The sCT generated from a single PETRA sequence shows promise for the generation of fast sCT for MRI based radiation therapy planning.

Segmentation and tracking in echocardiographic sequences: active contours guided by optical flow estimates

NASA Technical Reports Server (NTRS)

Mikic, I.; Krucinski, S.; Thomas, J. D.

1998-01-01

This paper presents a method for segmentation and tracking of cardiac structures in ultrasound image sequences. The developed algorithm is based on the active contour framework. This approach requires initial placement of the contour close to the desired position in the image, usually an object outline. Best contour shape and position are then calculated, assuming that at this configuration a global energy function, associated with a contour, attains its minimum. Active contours can be used for tracking by selecting a solution from a previous frame as an initial position in a present frame. Such an approach, however, fails for large displacements of the object of interest. This paper presents a technique that incorporates the information on pixel velocities (optical flow) into the estimate of initial contour to enable tracking of fast-moving objects. The algorithm was tested on several ultrasound image sequences, each covering one complete cardiac cycle. The contour successfully tracked boundaries of mitral valve leaflets, aortic root and endocardial borders of the left ventricle. The algorithm-generated outlines were compared against manual tracings by expert physicians. The automated method resulted in contours that were within the boundaries of intraobserver variability.

Fast l₁-SPIRiT compressed sensing parallel imaging MRI: scalable parallel implementation and clinically feasible runtime.

PubMed

Murphy, Mark; Alley, Marcus; Demmel, James; Keutzer, Kurt; Vasanawala, Shreyas; Lustig, Michael

2012-06-01

We present l₁-SPIRiT, a simple algorithm for auto calibrating parallel imaging (acPI) and compressed sensing (CS) that permits an efficient implementation with clinically-feasible runtimes. We propose a CS objective function that minimizes cross-channel joint sparsity in the wavelet domain. Our reconstruction minimizes this objective via iterative soft-thresholding, and integrates naturally with iterative self-consistent parallel imaging (SPIRiT). Like many iterative magnetic resonance imaging reconstructions, l₁-SPIRiT's image quality comes at a high computational cost. Excessively long runtimes are a barrier to the clinical use of any reconstruction approach, and thus we discuss our approach to efficiently parallelizing l₁-SPIRiT and to achieving clinically-feasible runtimes. We present parallelizations of l₁-SPIRiT for both multi-GPU systems and multi-core CPUs, and discuss the software optimization and parallelization decisions made in our implementation. The performance of these alternatives depends on the processor architecture, the size of the image matrix, and the number of parallel imaging channels. Fundamentally, achieving fast runtime requires the correct trade-off between cache usage and parallelization overheads. We demonstrate image quality via a case from our clinical experimentation, using a custom 3DFT spoiled gradient echo (SPGR) sequence with up to 8× acceleration via Poisson-disc undersampling in the two phase-encoded directions.

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.

Efficient iris recognition by characterizing key local variations.

PubMed

Ma, Li; Tan, Tieniu; Wang, Yunhong; Zhang, Dexin

2004-06-01

Unlike other biometrics such as fingerprints and face, the distinct aspect of iris comes from randomly distributed features. This leads to its high reliability for personal identification, and at the same time, the difficulty in effectively representing such details in an image. This paper describes an efficient algorithm for iris recognition by characterizing key local variations. The basic idea is that local sharp variation points, denoting the appearing or vanishing of an important image structure, are utilized to represent the characteristics of the iris. The whole procedure of feature extraction includes two steps: 1) a set of one-dimensional intensity signals is constructed to effectively characterize the most important information of the original two-dimensional image; 2) using a particular class of wavelets, a position sequence of local sharp variation points in such signals is recorded as features. We also present a fast matching scheme based on exclusive OR operation to compute the similarity between a pair of position sequences. Experimental results on 2255 iris images show that the performance of the proposed method is encouraging and comparable to the best iris recognition algorithm found in the current literature.

Local/non-local regularized image segmentation using graph-cuts: application to dynamic and multispectral MRI.

PubMed

Hanson, Erik A; Lundervold, Arvid

2013-11-01

Multispectral, multichannel, or time series image segmentation is important for image analysis in a wide range of applications. Regularization of the segmentation is commonly performed using local image information causing the segmented image to be locally smooth or piecewise constant. A new spatial regularization method, incorporating non-local information, was developed and tested. Our spatial regularization method applies to feature space classification in multichannel images such as color images and MR image sequences. The spatial regularization involves local edge properties, region boundary minimization, as well as non-local similarities. The method is implemented in a discrete graph-cut setting allowing fast computations. The method was tested on multidimensional MRI recordings from human kidney and brain in addition to simulated MRI volumes. The proposed method successfully segment regions with both smooth and complex non-smooth shapes with a minimum of user interaction.

Metal Artifact Reduction With MAVRIC SL at 3-T MRI in Patients With Hip Arthroplasty

PubMed Central

Choi, Soo-Jung; Koch, Kevin M.; Hargreaves, Brian A.; Stevens, Kathryn J.; Gold, Garry E.

2015-01-01

OBJECTIVE The objective of our study was to compare the multiacquisition variable-resonance image combination selective (MAVRIC SL) sequence with the 2D fast spin-echo (FSE) sequence for metal artifact reduction on 3-T MRI in patients with hip arthroplasty (HA). MATERIALS AND METHODS Matched 2D FSE and MAVRIC SL images of 21 hips (19 patients with HA) were included in the study group. Paired image sets, composed of 13 coronal and 12 axial slices (total, 25 image sets), of the 21 hips were evaluated. For quantitative analysis, the artifact area was measured at the level of the hip and femur. For qualitative analysis, two musculoskeletal radiologists independently compared paired 2D FSE and MAVRIC SL sets in terms of artifacts, depiction of anatomic detail, level of diagnostic confidence, and detection of abnormal findings. RESULTS The measured artifact area was significantly smaller (p < 0.05) on MAVRIC SL than 2D FSE at both the level of hip (59.9% reduction with MAVRIC SL) and femur (31.3% reduction with MAVRIC SL). The artifact score was also significantly decreased (p < 0.0001) with MAVRIC SL compared with 2D FSE for both reviewers. The hip joint capsule and the tendon attachment sites of the obturator externus and iliopsoas muscles were better depicted with MAVRIC SL than 2D FSE (p < 0.0125). Abnormal findings were significantly better shown on MAVRIC SL imaging compared with 2D FSE imaging (p < 0.0001). CONCLUSION The MAVRIC SL sequence can significantly reduce metal artifact on 3-T MRI compared with the 2D FSE sequence and can increase diagnostic confidence of 3-T MRI in patients with total HA. PMID:25539249

Magnetic resonance enteroclysis in patients with Crohn's disease: fat saturated T2-weighted sequences for evaluation of inflammatory activity.

PubMed

Grieser, Christian; Denecke, Timm; Steffen, Ingo G; Werner, Scarlett; Kröncke, Thomas; Guckelberger, Olaf; Pape, Ulrich-Frank; Meier, Johannes; Thiel, Regina; Kivelitz, Dietmar; Sturm, Andreas; Hamm, Bernd; Röttgen, Rainer

2012-04-01

To evaluate fat saturated (fs) T2-weighted (w) fast relaxation fast spin echo (FRFSE)-sequences compared to the standard protocol with contrast agent for the evaluation of inflammatory activity in patients with Crohn's Disease (CD). Fourty-eight patients (male, 17; female, 33; mean age, 37 years) with suspicion of inflammatory activity in proven CD who underwent MR enteroclysis (MRE) at 1.5T (GE Healthcare) were retrospectively included. Two blinded radiologists analyzed MRE images for presence and extent of CD lesions and degree of local inflammation for fsT2-w FRFSE and contrast enhanced T1-w images (T2-activity; T1-activity; score, 1-4) in consensus. Furthermore, mural signal intensity (SI) ratios (T2-ratio; T1-ratio) were recorded. Patient based MRE findings were correlated with endoscopic (45 patients), surgical (6 patients), histopathological, and clinical data (CDAI) as a surrogate reference standard. In total, 24 of 48 eligible patients presented with acute inflammatory activity with 123 affected bowel segments. ROC analysis of the total inflammatory score presented an AUC of 0.93 (p<0.001) for T2-activity (T1-activity, AUC 0.63; p=0.019). ROC analysis revealed an AUC of 0.76 (p<0.001) for the T2-ratio (T1-ratio, AUC 0.51; p=0.93). General linear regression model revealed T2-activity (p=0.001) and age (p=0.024) as predictive factors of acute bowel inflammation. T2-w FRFSE-sequences can depict CD lesions and help to assess the inflammation activity, even with improved accuracy as compared to contrast-enhanced T1-w sequences. Copyright © 2011 European Crohn's and Colitis Organisation. Published by Elsevier B.V. All rights reserved.

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.

Applications of nuclear magnetic resonance in paediatric surgery: magnetic resonance cholangiopancreatography and new sequences.

PubMed

Ragazzi, S; Vanzulli, A; Del Maschio, A; Tomaselli, V; Dell' Agnola, C A

2007-12-01

The aim of the study was to evaluate fast magnetic resonance cholangio-pancreatography (MRCP) sequences as an alternative and safe investigation method for neonatal and children's pancreaticobiliary diseases. Between January 2000 and December 2000, five children (age: 1 month 14 years; mean: 7 years) affected by pancreaticobiliary diseases or already operated for biliary pathologies were studied. Patients were evaluated by 1.5 T magnet single shot T2-weighted sequences (1 image per s, TR = infinite, TE = 150-180 ms). T1-weighted conventional sequences were obtained to study parenchymal tissue. No patient needed general anaesthetic. Only in one case was sedation necessary. Fast MRCP sequences provided very precise information on biliary tract anatomy. They revealed the intra and extrahepatic bile ducts, the gallbladder, the common bile duct and the bilio-pancreatic junction in all cases investigated. MRCP allowed us to evaluate Roux-en-Y type bilio-enteric anastomosis as accurately as percutaneous transhepatic cholangiography (PTC). In addition MRCP was the only reliable study in evaluating Roux-en-Y type anastomosis where ultrasonography (US) and endoscopic retrograde cholangiography (ERCP) could not be used. In conclusion MRCP is an accurate and non-invasive method with which to investigate the anatomy of the pancreaticobiliary tract in children. It could become the investigation of choice after US in the case of biliary and pancreatic diseases.

Assessment of blood supply to intracranial pathologies in children using MR digital subtraction angiography.

PubMed

Chooi, Weng Kong; Connolly, Dan J A; Coley, Stuart C; Griffiths, Paul D

2006-10-01

MR digital subtraction angiography (MR-DSA) is a contrast-enhanced MR angiographic sequence that enables time-resolved evaluation of the cerebral circulation. We describe the feasibility and technical success of our attempts at MR-DSA for the assessment of intracranial pathology in children. We performed MR-DSA in 15 children (age range 5 days to 16 years) referred for MR imaging because of known or suspected intracranial pathology that required a dynamic assessment of the cerebral vasculature. MR-DSA consisted of a thick (6-10 mm) slice-selective RF-spoiled fast gradient-echo sequence (RF-FAST) acquired before and during passage of an intravenously administered bolus of Gd-DTPA. The images were subtracted and viewed as a cine loop. MR-DSA was performed successfully in all patients. High-flow lesions were shown in four patients; these included vein of Galen aneurysmal malformation, dural fistula, and two partially treated arteriovenous malformations (AVMs). Low-flow lesions were seen in three patients, all of which were tumours. Normal flow was confirmed in eight patients including two with successfully treated AVMs, and in three patients with cavernomas. Our early experience suggests that MR-DSA is a realistic, non-invasive alternative to catheter angiography in certain clinical settings.

Comparison of FSE T2 W PROPELLER and 3D-FIESTA of 3 T MR for the internal auditory canal.

PubMed

Wu, Hai-Bo; Yuan, Hui-Shu; Ma, Furong; Zhao, Qiang

The study compared the use of periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) technique fast spin echo (FSE) T2 W and the sequence of three-dimensional fast imaging employing steady-state acquisition (3D-FIESTA) technique in the MRI of the internal auditory canal for overall image quality improvement. One hundred thirty-two patients undergoing FSE T2 W PROPELLER and 3D-FIESTA examinations of the internal auditory canal were included. All examinations were performed at 3.0 T with comparison of a sagittal oblique FSE T2 W sequence with the PROPELLER technique to 3D-FIESTA in the same reconstructed orientation with PROPELLER. Image quality was evaluated by two radiologists using a 4-point scale. The Wilcoxon signed rank test was used to compare the data of the two techniques. The image quality of FSE T2 W PROPELLER was significantly improved compared to the reconstructed images of 3D-FIESTA. Observer 1: median FSE T2 W with PROPELLER, 4 [mean, 3.455] versus median reconstructed 3D-FIESTA, 3 [mean, 3.15], (P<.001); Observer 2: median FSE T2 W with PROPELLER, 4 [mean, 3.47] versus median reconstructed 3D-FIESTA, 3 [mean, 3.25], (P<.001). Interobserver agreement was good (k value, 0.73) for the rating of the overall image quality. The FSE T2 W PROPELLER technique for MRI of internal auditory canal reduced uncertainty caused by motion artifact and improved the quality of the image compared to the reconstructed 3D-FIESTA. It was affected by different parameters including the blade width, echo train length (ETL). This is explained by data oversampling at the center region of k-space, which requires additional imaging time over conventional MRI techniques. Increasing blade was expected to improve motion correction effects but also the signal-to-noise ratio. ETL increases the image sharpness and the overall image quality. Copyright © 2016. Published by Elsevier Inc.

Real-time image reconstruction and display system for MRI using a high-speed personal computer.

PubMed

Haishi, T; Kose, K

1998-09-01

A real-time NMR image reconstruction and display system was developed using a high-speed personal computer and optimized for the 32-bit multitasking Microsoft Windows 95 operating system. The system was operated at various CPU clock frequencies by changing the motherboard clock frequency and the processor/bus frequency ratio. When the Pentium CPU was used at the 200 MHz clock frequency, the reconstruction time for one 128 x 128 pixel image was 48 ms and that for the image display on the enlarged 256 x 256 pixel window was about 8 ms. NMR imaging experiments were performed with three fast imaging sequences (FLASH, multishot EPI, and one-shot EPI) to demonstrate the ability of the real-time system. It was concluded that in most cases, high-speed PC would be the best choice for the image reconstruction and display system for real-time MRI. Copyright 1998 Academic Press.

Fast ℓ1-SPIRiT Compressed Sensing Parallel Imaging MRI: Scalable Parallel Implementation and Clinically Feasible Runtime

PubMed Central

Murphy, Mark; Alley, Marcus; Demmel, James; Keutzer, Kurt; Vasanawala, Shreyas; Lustig, Michael

2012-01-01

We present ℓ1-SPIRiT, a simple algorithm for auto calibrating parallel imaging (acPI) and compressed sensing (CS) that permits an efficient implementation with clinically-feasible runtimes. We propose a CS objective function that minimizes cross-channel joint sparsity in the Wavelet domain. Our reconstruction minimizes this objective via iterative soft-thresholding, and integrates naturally with iterative Self-Consistent Parallel Imaging (SPIRiT). Like many iterative MRI reconstructions, ℓ1-SPIRiT’s image quality comes at a high computational cost. Excessively long runtimes are a barrier to the clinical use of any reconstruction approach, and thus we discuss our approach to efficiently parallelizing ℓ1-SPIRiT and to achieving clinically-feasible runtimes. We present parallelizations of ℓ1-SPIRiT for both multi-GPU systems and multi-core CPUs, and discuss the software optimization and parallelization decisions made in our implementation. The performance of these alternatives depends on the processor architecture, the size of the image matrix, and the number of parallel imaging channels. Fundamentally, achieving fast runtime requires the correct trade-off between cache usage and parallelization overheads. We demonstrate image quality via a case from our clinical experimentation, using a custom 3DFT Spoiled Gradient Echo (SPGR) sequence with up to 8× acceleration via poisson-disc undersampling in the two phase-encoded directions. PMID:22345529

Fast-Spiking Interneurons Supply Feedforward Control of Bursting, Calcium, and Plasticity for Efficient Learning.

PubMed

Owen, Scott F; Berke, Joshua D; Kreitzer, Anatol C

2018-02-08

Fast-spiking interneurons (FSIs) are a prominent class of forebrain GABAergic cells implicated in two seemingly independent network functions: gain control and network plasticity. Little is known, however, about how these roles interact. Here, we use a combination of cell-type-specific ablation, optogenetics, electrophysiology, imaging, and behavior to describe a unified mechanism by which striatal FSIs control burst firing, calcium influx, and synaptic plasticity in neighboring medium spiny projection neurons (MSNs). In vivo silencing of FSIs increased bursting, calcium transients, and AMPA/NMDA ratios in MSNs. In a motor sequence task, FSI silencing increased the frequency of calcium transients but reduced the specificity with which transients aligned to individual task events. Consistent with this, ablation of FSIs disrupted the acquisition of striatum-dependent egocentric learning strategies. Together, our data support a model in which feedforward inhibition from FSIs temporally restricts MSN bursting and calcium-dependent synaptic plasticity to facilitate striatum-dependent sequence learning. Copyright © 2018 Elsevier Inc. All rights reserved.

MRI technique for the snapshot imaging of quantitative velocity maps using RARE.

PubMed

Shiko, G; Sederman, A J; Gladden, L F

2012-03-01

A quantitative PGSE-RARE pulse sequence was developed and successfully applied to the in situ dissolution of two pharmaceutical formulations dissolving over a range of timescales. The new technique was chosen over other existing fast velocity imaging techniques because it is T(2) weighted, not T(2)(∗) weighted, and is, therefore, robust for imaging time-varying interfaces and flow in magnetically heterogeneous systems. The complex signal was preserved intact by separating odd and even echoes to obtain two phase maps which are then averaged in post-processing. Initially, the validity of the technique was shown when imaging laminar flow in a pipe. Subsequently, the dissolution of two drugs was followed in situ, where the technique enables the imaging and quantification of changes in the form of the tablet and the flow field surrounding it at high spatial and temporal resolution. First, the complete 3D velocity field around an eroding salicylic acid tablet was acquired at a resolution of 98×49 μm(2), within 20 min, and monitored over ∼13 h. The tablet was observed to experience a heterogeneous flow field and, hence a heterogeneous shear field, which resulted in the non-symmetric erosion of the tablet. Second, the dissolution of a fast dissolving immediate release tablet was followed using one-shot 2D velocity images acquired every 5.2 s at a resolution of 390×390 μm(2). The quantitative nature of the technique and fast acquisition times provided invaluable information on the dissolution behaviour of this tablet, which had not been attainable previously with conventional quantitative MRI techniques. Copyright © 2012 Elsevier Inc. All rights reserved.

Echo-Planar Imaging for a 9.4 Tesla Vertical-Bore Superconducting Magnet Using an Unshielded Gradient Coil

PubMed Central

KODAMA, Nao; KOSE, Katsumi

2016-01-01

Echo-planar imaging (EPI) sequences were developed for a 9.4 Tesla vertical standard bore (∼54 mm) superconducting magnet using an unshielded gradient coil optimized for live mice imaging and a data correction technique with reference scans. Because EPI requires fast switching of intense magnetic field gradients, eddy currents were induced in the surrounding metallic materials, e.g., the room temperature bore, and this produced serious artifacts on the EPI images. We solved the problem using an unshielded gradient coil set of proper size (outer diameter = 39 mm, inner diameter = 32 mm) with time control of the current rise and reference scans. The obtained EPI images of a phantom and a plant sample were almost artifact-free and demonstrated the promise of our approach. PMID:27001398

A re-sequencing based assessment of genomic heterogeneity and fast neutron-induced deletions in a common bean cultivar

USDA-ARS?s Scientific Manuscript database

A small fast neutron mutant population has been established from Phaseolus vulgaris cv. Red Hawk. We leveraged the available P. vulgaris genome sequence and high throughput next generation DNA sequencing to examine the genomic structure of five Phaseolus vulgaris cv. Red Hawk fast neutron mutants wi...

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.

Using the auxiliary camera for system calibration of 3D measurement by digital speckle

NASA Astrophysics Data System (ADS)

Xue, Junpeng; Su, Xianyu; Zhang, Qican

2014-06-01

The study of 3D shape measurement by digital speckle temporal sequence correlation have drawn a lot of attention by its own advantages, however, the measurement mainly for depth z-coordinate, horizontal physical coordinate (x, y) are usually marked as image pixel coordinate. In this paper, a new approach for the system calibration is proposed. With an auxiliary camera, we made up the temporary binocular vision system, which are used for the calibration of horizontal coordinates (mm) while the temporal sequence reference-speckle-sets are calibrated. First, the binocular vision system has been calibrated using the traditional method. Then, the digital speckles are projected on the reference plane, which is moved by equal distance in the direction of depth, temporal sequence speckle images are acquired with camera as reference sets. When the reference plane is in the first position and final position, crossed fringe pattern are projected to the plane respectively. The control points of pixel coordinates are extracted by Fourier analysis from the images, and the physical coordinates are calculated by the binocular vision. The physical coordinates corresponding to each pixel of the images are calculated by interpolation algorithm. Finally, the x and y corresponding to arbitrary depth value z are obtained by the geometric formula. Experiments prove that our method can fast and flexibly measure the 3D shape of an object as point cloud.

Real-time volumetric relative dosimetry for magnetic resonance—image-guided radiation therapy (MR-IGRT)

NASA Astrophysics Data System (ADS)

Lee, Hannah J.; Kadbi, Mo; Bosco, Gary; Ibbott, Geoffrey S.

2018-02-01

The integration of magnetic resonance imaging (MRI) with linear accelerators (linac) has enabled the use of 3D MR-visible gel dosimeters for real-time verification of volumetric dose distributions. Several iron-based radiochromic 3D gels were created in-house then imaged and irradiated in a pre-clinical 1.5 T-7 MV MR-Linac. MR images were acquired using a range of balanced-fast field echo (b-FFE) sequences during irradiation to assess the contrast and dose response in irradiated regions and to minimize the presence of MR artifacts. Out of four radiochromic 3D gel formulations, the FOX 3D gel was found to provide superior MR contrast in the irradiated regions. The FOX gels responded linearly with respect to real-time dose and the signal remained stable post-irradiation for at least 20 min. The response of the FOX gel also was found to be unaffected by the radiofrequency and gradient fields created by the b-FFE sequence during irradiation. A reusable version of the FOX gel was used for b-FFE sequence optimization to reduce artifacts by increasing the number of averages at the expense of temporal resolution. Regardless of the real-time MR sequence used, the FOX 3D gels responded linearly to dose with minimal magnetic field effects due to the strong 1.5 T field or gradient fields present during imaging. These gels can easily be made in-house using non-reusable and reusable formulations depending on the needs of the clinic, and the results of this study encourage further applications of 3D gels for MR-IGRT applications.

Evaluation of intervertebral disc cartilaginous endplate structure using magnetic resonance imaging.

PubMed

Moon, Sung M; Yoder, Jonathon H; Wright, Alexander C; Smith, Lachlan J; Vresilovic, Edward J; Elliott, Dawn M

2013-08-01

The cartilaginous endplate (CEP) is a thin layer of hyaline cartilage positioned between the vertebral endplate and nucleus pulposus (NP) that functions both as a mechanical barrier and as a gateway for nutrient transport into the disc. Despite its critical role in disc nutrition and degeneration, the morphology of the CEP has not been well characterized. The objective of this study was to visualize and report observations of the CEP three-dimensional morphology, and quantify CEP thickness using an MRI FLASH (fast low-angle shot) pulse sequence. MR imaging of ex vivo human cadaveric lumbar spine segments (N = 17) was performed in a 7T MRI scanner with sequence parameters that were selected by utilizing high-resolution T1 mapping, and an analytical MRI signal model to optimize image contrast between CEP and NP. The CEP thickness at five locations along the mid-sagittal AP direction (center, 5 mm, 10 mm off-center towards anterior and posterior) was measured, and analyzed using two-way ANOVA and a post hoc Bonferonni test. For further investigation, six in vivo volunteers were imaged with a similar sequence in a 3T MRI scanner. In addition, decalcified and undecalcified histology was performed, which confirmed that the FLASH sequence successfully detected the CEP. CEP thickness determined by MRI in the mid-sagittal plane across all lumbar disc levels and locations was 0.77 ± 0.24 mm ex vivo. The CEP thickness was not different across disc levels, but was thinner toward the center of the disc. This study demonstrates the potential of MRI FLASH imaging for structural quantification of the CEP geometry, which may be developed as a technique to evaluate changes in the CEP with disc degeneration in future applications.

SU-G-IeP1-09: MRI Evaluation of a Direction-Modulated Brachytherapy (DMBT) Tandem Applicator for Cervical Cancer On 3T

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

Soliman, A; Safigholi, H; Sunnybrook Health Sciences Centre, Toronto, ON

2016-06-15

Purpose: To assess image quality and artifact extent of a novel direction modulated brachytherapy (DMBT) tandem applicator on a 3T MRI using various clinical imaging sequences. Methods: The tandem applicator is composed of a tungsten alloy with 6 peripheral grooves covered with a PEEK tip. An MR-compatible phantom with similar dimensions to the female pelvis was manufactured. To visually assess the spatial shift of the applicator’s tip, a mountable radial-fiducial with 4 plastic rods, each of 3mm diameter, was designed to tightly fit on the applicator. The rods are separated by 16 mm and mounted at 90-degree relative to onemore » another. The pelvis phantom was filled with a solution of MnCl2 to mimic T2 relaxation time of the cervix (60-80 ms at 3T).Imaging was performed on a 3T Philips Achieva using a 16-channel Torso coil array. Four MR sequences were tested: T2-weighted fast spin-echo (T2w-FSE), proton density weighted FSE (PDw-FSE), T1-weighted FSE (T1w-FSE) and T1 weighted spoiled gradient echo (T1w-GE). The spatial resolution was kept the same between all sequences: 0.6 × 0.6 × 3 mm{sup 3} with no slice gaps. Para-sagittal images were acquired with the applicator fixed at a 30-degree angle anterior to the B0- field to mimic clinical settings. Results: Minimal artifacts were observed on T2w-FSE, PDw-FSE and T1-FSE, while significant artifacts were seen on T1w-GE images. Artifacts induced in all 3 FSE sequences did not hinder accurate localisation of the tip and the applicator boundaries. The drift of the applicator’s centreline from the radial fiducials was measured and found to be < 1 mm for the 3 FSE sequences. Conclusion: The tungsten–based DMBT applicator can be potentially used on 3T with various clinical sequences without inducing significant artifacts. Further validation on patients as well as the evaluation of relative SNR among the different sequences is required.« less

Early Effects of Combretastatin A4 Phosphate Assessed by Anatomic and Carbogen-Based Functional Magnetic Resonance Imaging on Rat Bladder Tumors Implanted in Nude Mice1

PubMed Central

Thomas, Carole D.; Walczak, Christine; Kaffy, Julia; Pontikis, Renée; Jouanneau, Jacqueline; Volk, Andreas

2006-01-01

Abstract Combretastatin A4 phosphate (CA4P) causes rapid disruption of the tumor vasculature and is currently being evaluated for antivascular therapy. We describe the initial results obtained with a noninvasive multi-parametric magnetic resonance imaging (MRI) approach to assess the early effects of CA4P on rat bladder tumors implanted on nude mice. MRI (4.7 T) comprised a fast spin-echo sequence for growth curve assessment; a multislice multiecho sequence for T2 measurement before, 15 minutes after, and 24 hours after CA4P (100 mg/kg); and a fast T2w* gradient-echo sequence to assess MR signal modification under carbogen breathing before, 35 minutes after, and 24 hours after CA4P. The tumor fraction with increased T2w* signal intensity under carbogen (T+) was used to quantify CA4P effect on functional vasculature. CA4P slowed tumor growth over 24 hours and accelerated necrosis development. T+ decrease was observed already at 35 minutes post-CA4P. Early T2 increase was observed in regions becoming necrotic at 24 hours post-CA4P, as confirmed by high T2 and histology. These regions exhibited, under carbogen, a switch from T2w* signal increase before CA4P to a decrease post-CA4P. The combination of carbogen-based functional MRI and T2 measurement may be useful for the early follow-up of antivascular therapy without the administration of contrast agents. PMID:16867221

Early effects of combretastatin A4 phosphate assessed by anatomic and carbogen-based functional magnetic resonance imaging on rat bladder tumors implanted in nude mice.

PubMed

Thomas, Carole D; Walczak, Christine; Kaffy, Julia; Pontikis, Renée; Jouanneau, Jacqueline; Volk, Andreas

2006-07-01

Combretastatin A4 phosphate (CA4P) causes rapid disruption of the tumor vasculature and is currently being evaluated for antivascular therapy. We describe the initial results obtained with a noninvasive multiparametric magnetic resonance imaging (MRI) approach to assess the early effects of CA4P on rat bladder tumors implanted on nude mice. MRI (4.7 T) comprised a fast spin-echo sequence for growth curve assessment; a multislice multiecho sequence for T2 measurement before, 15 minutes after, and 24 hours after CA4P (100 mg/kg); and a fast T2w* gradient-echo sequence to assess MR signal modification under carbogen breathing before, 35 minutes after, and 24 hours after CA4P. The tumor fraction with increased T2w* signal intensity under carbogen (T+) was used to quantify CA4P effect on functional vasculature. CA4P slowed tumor growth over 24 hours and accelerated necrosis development. T+ decrease was observed already at 35 minutes post-CA4P. Early T2 increase was observed in regions becoming necrotic at 24 hours post-CA4P, as confirmed by high T2 and histology. These regions exhibited, under carbogen, a switch from T2w* signal increase before CA4P to a decrease postCA4P. The combination of carbogen-based functional MRI and T2 measurement may be useful for the early follow-up of antivascular therapy without the administration of contrast agents.

Evaluation of takayasu arteritis with delayed contrast-enhanced MR imaging by a free-breathing 3D IR turbo FLASH.

PubMed

Liu, Min; Liu, Weifang; Li, Haoyuan; Shu, Xiaoming; Tao, Xincao; Zhai, Zhenguo

2017-12-01

The primary aim of our case-control study was to observe delayed contrast-enhanced magnetic resonance imaging (DCE-MRI) in patients with Takayasu arteritis (TA) in comparison with magnetic resonance angiography (MRA). Twenty-seven patients including 15 with active TA and 12 with stable TA who underwent both aortic MRA and DCE-MRI were included. A total of 27 sex- and age-matched healthy volunteers were enrolled as the control group. MRA were obtained with T1WI-volume-interpolated breath-hold examination sequence or fast low-angle shot (FLASH) sequence. DCE-MRI was acquired with a free-breathing three-dimensional inversion recovery Turbo fast low-angle shot (3D IR Turbo FLASH). Neither stenosis nor delayed enhancement of arterial wall was shown in the control group. In patients with stable TA, arterial stenosis was observed on MRA. On DCE-MR, delayed enhancement of arterial walls could be observed in the active TA group but not in the stable TA group or the control group. Stenotic arteries on MRA were comparable in the active TA and stable TA (χ = 2.70, P = .259); however, delayed enhancement of arterial walls in the active-TA group were more than those in the stable group (χ = 27.00, P < .001). Our results suggest that DCE-MRI with the free-breathing 3D IR Turbo FLASH sequence could assess TA and delayed enhancement on DCE-MRI is one characteristics of the active TA. Copyright © 2017 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.

Spatial patterns of fasting and fed antropyloric pressure waves in humans.

PubMed Central

Sun, W M; Hebbard, G S; Malbert, C H; Jones, K L; Doran, S; Horowitz, M; Dent, J

1997-01-01

1. Gastric mechanics were investigated by categorizing the temporal and spatial patterning of pressure waves associated with individual gastric contractions. 2. In twelve healthy volunteers, intraluminal pressures were monitored from nine side hole recording points spaced at 1.5 cm intervals along the antrum, pylorus and duodenum. 3. Pressure wave sequences that occurred during phase II fasting contractions (n = 221) and after food (n = 778) were evaluated. 4. The most common pattern of pressure wave onset along the antrum was a variable combination of antegrade, synchronous and retrograde propagation between side hole pairs. This variable pattern accounted for 42% of sequences after food, and 34% during fasting (P < 0.05). Other common pressure wave sequence patterns were: purely antegrade-29% after food and 42% during fasting (P < 0.05); purely synchronous-23% fed and 17% fasting; and purely retrograde-6% fed and 8% fasting. The length of sequences was shorter after food (P < 0.05). Some sequences 'skipped' individual recording points. 5. The spatial patterning of gastric pressure wave sequences is diverse, and may explain the differing mechanical outcomes among individual gastric contractions. 6. Better understanding of gastric mechanics may be gained from temporally precise correlations of luminal flows and pressures and gastric wall motion during individual gastric contraction sequences. PMID:9306286

Ultra-fast speech comprehension in blind subjects engages primary visual cortex, fusiform gyrus, and pulvinar – a functional magnetic resonance imaging (fMRI) study

PubMed Central

2013-01-01

Background Individuals suffering from vision loss of a peripheral origin may learn to understand spoken language at a rate of up to about 22 syllables (syl) per second - exceeding by far the maximum performance level of normal-sighted listeners (ca. 8 syl/s). To further elucidate the brain mechanisms underlying this extraordinary skill, functional magnetic resonance imaging (fMRI) was performed in blind subjects of varying ultra-fast speech comprehension capabilities and sighted individuals while listening to sentence utterances of a moderately fast (8 syl/s) or ultra-fast (16 syl/s) syllabic rate. Results Besides left inferior frontal gyrus (IFG), bilateral posterior superior temporal sulcus (pSTS) and left supplementary motor area (SMA), blind people highly proficient in ultra-fast speech perception showed significant hemodynamic activation of right-hemispheric primary visual cortex (V1), contralateral fusiform gyrus (FG), and bilateral pulvinar (Pv). Conclusions Presumably, FG supports the left-hemispheric perisylvian “language network”, i.e., IFG and superior temporal lobe, during the (segmental) sequencing of verbal utterances whereas the collaboration of bilateral pulvinar, right auditory cortex, and ipsilateral V1 implements a signal-driven timing mechanism related to syllabic (suprasegmental) modulation of the speech signal. These data structures, conveyed via left SMA to the perisylvian “language zones”, might facilitate – under time-critical conditions – the consolidation of linguistic information at the level of verbal working memory. PMID:23879896

Quantitative evaluation of susceptibility effects caused by dental materials in head magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Strocchi, S.; Ghielmi, M.; Basilico, F.; Macchi, A.; Novario, R.; Ferretti, R.; Binaghi, E.

2016-03-01

This work quantitatively evaluates the effects induced by susceptibility characteristics of materials commonly used in dental practice on the quality of head MR images in a clinical 1.5T device. The proposed evaluation procedure measures the image artifacts induced by susceptibility in MR images by providing an index consistent with the global degradation as perceived by the experts. Susceptibility artifacts were evaluated in a near-clinical setup, using a phantom with susceptibility and geometric characteristics similar to that of a human head. We tested different dentist materials, called PAL Keramit, Ti6Al4V-ELI, Keramit NP, ILOR F, Zirconia and used different clinical MR acquisition sequences, such as "classical" SE and fast, gradient, and diffusion sequences. The evaluation is designed as a matching process between reference and artifacts affected images recording the same scene. The extent of the degradation induced by susceptibility is then measured in terms of similarity with the corresponding reference image. The matching process involves a multimodal registration task and the use an adequate similarity index psychophysically validated, based on correlation coefficient. The proposed analyses are integrated within a computer-supported procedure that interactively guides the users in the different phases of the evaluation method. 2-Dimensional and 3-dimensional indexes are used for each material and each acquisition sequence. From these, we drew a ranking of the materials, averaging the results obtained. Zirconia and ILOR F appear to be the best choice from the susceptibility artefacts point of view, followed, in order, by PAL Keramit, Ti6Al4V-ELI and Keramit NP.

Effect of pulse sequence parameter selection on signal strength in positive-contrast MRI markers for MRI-based prostate postimplant assessment

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

Lim, Tze Yee

Purpose: For postimplant dosimetric assessment, computed tomography (CT) is commonly used to identify prostate brachytherapy seeds, at the expense of accurate anatomical contouring. Magnetic resonance imaging (MRI) is superior to CT for anatomical delineation, but identification of the negative-contrast seeds is challenging. Positive-contrast MRI markers were proposed to replace spacers to assist seed localization on MRI images. Visualization of these markers under varying scan parameters was investigated. Methods: To simulate a clinical scenario, a prostate phantom was implanted with 66 markers and 86 seeds, and imaged on a 3.0T MRI scanner using a 3D fast radiofrequency-spoiled gradient recalled echo acquisitionmore » with various combinations of scan parameters. Scan parameters, including flip angle, number of excitations, bandwidth, field-of-view, slice thickness, and encoding steps were systematically varied to study their effects on signal, noise, scan time, image resolution, and artifacts. Results: The effects of pulse sequence parameter selection on the marker signal strength and image noise were characterized. The authors also examined the tradeoff between signal-to-noise ratio, scan time, and image artifacts, such as the wraparound artifact, susceptibility artifact, chemical shift artifact, and partial volume averaging artifact. Given reasonable scan time and managable artifacts, the authors recommended scan parameter combinations that can provide robust visualization of the MRI markers. Conclusions: The recommended MRI pulse sequence protocol allows for consistent visualization of the markers to assist seed localization, potentially enabling MRI-only prostate postimplant dosimetry.« less

Fetal eye movements on magnetic resonance imaging.

PubMed

Woitek, Ramona; Kasprian, Gregor; Lindner, Christian; Stuhr, Fritz; Weber, Michael; Schöpf, Veronika; Brugger, Peter C; Asenbaum, Ulrika; Furtner, Julia; Bettelheim, Dieter; Seidl, Rainer; Prayer, Daniela

2013-01-01

Eye movements are the physical expression of upper fetal brainstem function. Our aim was to identify and differentiate specific types of fetal eye movement patterns using dynamic MRI sequences. Their occurrence as well as the presence of conjugated eyeball motion and consistently parallel eyeball position was systematically analyzed. Dynamic SSFP sequences were acquired in 72 singleton fetuses (17-40 GW, three age groups [17-23 GW, 24-32 GW, 33-40 GW]). Fetal eye movements were evaluated according to a modified classification originally published by Birnholz (1981): Type 0: no eye movements; Type I: single transient deviations; Type Ia: fast deviation, slower reposition; Type Ib: fast deviation, fast reposition; Type II: single prolonged eye movements; Type III: complex sequences; and Type IV: nystagmoid. In 95.8% of fetuses, the evaluation of eye movements was possible using MRI, with a mean acquisition time of 70 seconds. Due to head motion, 4.2% of the fetuses and 20.1% of all dynamic SSFP sequences were excluded. Eye movements were observed in 45 fetuses (65.2%). Significant differences between the age groups were found for Type I (p = 0.03), Type Ia (p = 0.031), and Type IV eye movements (p = 0.033). Consistently parallel bulbs were found in 27.3-45%. In human fetuses, different eye movement patterns can be identified and described by MRI in utero. In addition to the originally classified eye movement patterns, a novel subtype has been observed, which apparently characterizes an important step in fetal brainstem development. We evaluated, for the first time, eyeball position in fetuses. Ultimately, the assessment of fetal eye movements by MRI yields the potential to identify early signs of brainstem dysfunction, as encountered in brain malformations such as Chiari II or molar tooth malformations.

MR-compatibility assessment of MADPET4: a study of interferences between an SiPM-based PET insert and a 7 T MRI system.

PubMed

Omidvari, Negar; Topping, Geoffrey; Cabello, Jorge; Paul, Stephan; Schwaiger, Markus; Ziegler, Sibylle I

2018-05-01

Compromises in the design of a positron emission tomography (PET) insert for a magnetic resonance imaging (MRI) system should minimize the deterioration of image quality in both modalities, particularly when simultaneous demanding acquisitions are performed. In this work, the advantages of using individually read-out crystals with high-gain silicon photomultipliers (SiPMs) were studied with a small animal PET insert for a 7 T MRI system, in which the SiPM charge was transferred to outside the MRI scanner using coaxial cables. The interferences between the two systems were studied with three radio-frequency (RF) coil configurations. The effects of PET on the static magnetic field, flip angle distribution, RF noise, and image quality of various MRI sequences (gradient echo, spin echo, and echo planar imaging (EPI) at 1 H frequency, and chemical shift imaging at 13 C frequency) were investigated. The effects of fast-switching gradient fields and RF pulses on PET count rate were studied, while the PET insert and the readout electronics were not shielded. Operating the insert inside a 1 H volume coil, used for RF transmission and reception, limited the MRI to T1-weighted imaging, due to coil detuning and RF attenuation, and resulted in significant PET count loss. Using a surface receive coil allowed all tested MR sequences to be used with the insert, with 45-59% signal-to-noise ratio (SNR) degradation, compared to without PET. With a 1 H/ 13 C volume coil inside the insert and shielded by a copper tube, the SNR degradation was limited to 23-30% with all tested sequences. The insert did not introduce any discernible distortions into images of two tested EPI sequences. Use of truncated sinc shaped RF excitation pulses and gradient field switching had negligible effects on PET count rate. However, PET count rate was substantially affected by high-power RF block pulses and temperature variations due to high gradient duty cycles.

Efficient Wide Baseline Structure from Motion

NASA Astrophysics Data System (ADS)

Michelini, Mario; Mayer, Helmut

2016-06-01

This paper presents a Structure from Motion approach for complex unorganized image sets. To achieve high accuracy and robustness, image triplets are employed and (an approximate) camera calibration is assumed to be known. The focus lies on a complete linking of images even in case of large image distortions, e.g., caused by wide baselines, as well as weak baselines. A method for embedding image descriptors into Hamming space is proposed for fast image similarity ranking. The later is employed to limit the number of pairs to be matched by a wide baseline method. An iterative graph-based approach is proposed formulating image linking as the search for a terminal Steiner minimum tree in a line graph. Finally, additional links are determined and employed to improve the accuracy of the pose estimation. By this means, loops in long image sequences are implicitly closed. The potential of the proposed approach is demonstrated by results for several complex image sets also in comparison with VisualSFM.

High-resolution imaging of (100) kyanite surfaces using friction force microscopy in water

NASA Astrophysics Data System (ADS)

Pimentel, Carlos; Gnecco, Enrico; Pina, Carlos M.

2015-05-01

In this paper, we present high-resolution friction force microscopy (FFM) images of the (100) face of kyanite (Al2SiO5) immersed in water. These images show an almost rectangular lattice presumably defined by the protruding oxygen of AlO6 polyhedra. Surface lattice parameters measured on two-dimensional fast Fourier transform (2D-FFT) plots of recorded high-resolution friction maps are in good agreement with lattice parameters calculated from the bulk mineral structure. Friction measurements performed along the [001] and [010] directions on the kyanite (100) face provide similar friction coefficients μ ≈ 0.10, even if the sequences of AlO6 polyhedra are different along the two crystallographic directions.

Positive Selection Underlies Faster-Z Evolution of Gene Expression in Birds

PubMed Central

Dean, Rebecca; Harrison, Peter W.; Wright, Alison E.; Zimmer, Fabian; Mank, Judith E.

2015-01-01

The elevated rate of evolution for genes on sex chromosomes compared with autosomes (Fast-X or Fast-Z evolution) can result either from positive selection in the heterogametic sex or from nonadaptive consequences of reduced relative effective population size. Recent work in birds suggests that Fast-Z of coding sequence is primarily due to relaxed purifying selection resulting from reduced relative effective population size. However, gene sequence and gene expression are often subject to distinct evolutionary pressures; therefore, we tested for Fast-Z in gene expression using next-generation RNA-sequencing data from multiple avian species. Similar to studies of Fast-Z in coding sequence, we recover clear signatures of Fast-Z in gene expression; however, in contrast to coding sequence, our data indicate that Fast-Z in expression is due to positive selection acting primarily in females. In the soma, where gene expression is highly correlated between the sexes, we detected Fast-Z in both sexes, although at a higher rate in females, suggesting that many positively selected expression changes in females are also expressed in males. In the gonad, where intersexual correlations in expression are much lower, we detected Fast-Z for female gene expression, but crucially, not males. This suggests that a large amount of expression variation is sex-specific in its effects within the gonad. Taken together, our results indicate that Fast-Z evolution of gene expression is the product of positive selection acting on recessive beneficial alleles in the heterogametic sex. More broadly, our analysis suggests that the adaptive potential of Z chromosome gene expression may be much greater than that of gene sequence, results which have important implications for the role of sex chromosomes in speciation and sexual selection. PMID:26067773

Gradient-Induced Voltages on 12-Lead ECGs during High Duty-Cycle MRI Sequences and a Method for Their Removal considering Linear and Concomitant Gradient Terms

PubMed Central

Zhang, Shelley HuaLei; Ho Tse, Zion Tsz; Dumoulin, Charles L.; Kwong, Raymond Y.; Stevenson, William G.; Watkins, Ronald; Ward, Jay; Wang, Wei; Schmidt, Ehud J.

2015-01-01

Purpose To restore 12-lead ECG signal fidelity inside MRI by removing magnetic-field gradient induced-voltages during high gradient-duty-cycle sequences. Theory and Methods A theoretical equation was derived, providing first- and second-order electrical fields induced at individual ECG electrode as a function of gradient fields. Experiments were performed at 3T on healthy volunteers, using a customized acquisition system which captured full amplitude and frequency response of ECGs, or a commercial recording system. The 19 equation coefficients were derived by linear regression of data from accelerated sequences, and used to compute induced-voltages in real-time during full-resolution sequences to remove ECG artifacts. Restored traces were evaluated relative to ones acquired without imaging. Results Measured induced-voltages were 0.7V peak-to-peak during balanced Steady-State Free Precession (bSSFP) with heart at the isocenter. Applying the equation during gradient echo sequencing, three-dimensional fast spin echo and multi-slice bSSFP imaging restored nonsaturated traces and second-order concomitant terms showed larger contributions in electrodes farther from the magnet isocenter. Equation coefficients are evaluated with high repeatability (ρ = 0.996) and are subject, sequence, and slice-orientation dependent. Conclusion Close agreement between theoretical and measured gradient-induced voltages allowed for real-time removal. Prospective estimation of sequence-periods where large induced-voltages occur may allow hardware removal of these signals. PMID:26101951

Real-Time Digital Bright Field Technology for Rapid Antibiotic Susceptibility Testing.

PubMed

Canali, Chiara; Spillum, Erik; Valvik, Martin; Agersnap, Niels; Olesen, Tom

2018-01-01

Optical scanning through bacterial samples and image-based analysis may provide a robust method for bacterial identification, fast estimation of growth rates and their modulation due to the presence of antimicrobial agents. Here, we describe an automated digital, time-lapse, bright field imaging system (oCelloScope, BioSense Solutions ApS, Farum, Denmark) for rapid and higher throughput antibiotic susceptibility testing (AST) of up to 96 bacteria-antibiotic combinations at a time. The imaging system consists of a digital camera, an illumination unit and a lens where the optical axis is tilted 6.25° relative to the horizontal plane of the stage. Such tilting grants more freedom of operation at both high and low concentrations of microorganisms. When considering a bacterial suspension in a microwell, the oCelloScope acquires a sequence of 6.25°-tilted images to form an image Z-stack. The stack contains the best-focus image, as well as the adjacent out-of-focus images (which contain progressively more out-of-focus bacteria, the further the distance from the best-focus position). The acquisition process is repeated over time, so that the time-lapse sequence of best-focus images is used to generate a video. The setting of the experiment, image analysis and generation of time-lapse videos can be performed through a dedicated software (UniExplorer, BioSense Solutions ApS). The acquired images can be processed for online and offline quantification of several morphological parameters, microbial growth, and inhibition over time.

TH-A-BRF-05: MRI of Individual Lymph Nodes to Guide Regional Breast Radiotherapy

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

Heijst, T van; Asselen, B van; Lagendijk, J

2014-06-15

Purpose: In regional radiotherapy (RT) for breast-cancer patients, direct visualization of individual lymph nodes (LNs) may reduce target volumes and Result in lower toxicity (i.e. reduced radiation pneumonitis, arm edema, arm morbidity), relative to standard CT-based delineations. To this end, newly designed magnetic resonance imaging (MRI) sequences were optimized and assessed qualitatively and quantitatively. Methods: In ten healthy female volunteers, a scanning protocol was developed and optimized. Coronal images were acquired in supine RT position positioned on a wedge board on a 1.5 T Ingenia (Philips) wide-bore MRI. In four volunteers the optimized MRI protocol was applied, including a 3-dimensionalmore » (3D) T1-weighted (T1w) fast-field-echo (FFE). T2w sequences, including 3D FFE, 3D and 2D fast spin echo (FSE), and diffusion-weighted single-shot echo-planar imaging (DWI) were also performed. Several fatsuppression techniques were used. Qualitative evaluation parameters included LN contrast, motion susceptibility, visibility of anatomical structures, and fat suppression. The number of visible axillary and supraclavicular LNs was also determined. Results: T1 FFE, insensitive to motion, lacked contrast of LNs, which often blended in with soft tissue and blood. T2 FFE showed high contrast, but some LNs were obscured due to motion. Both 2D and 3D FSE were motion-insensitive having high contrast, although some blood remained visible. 2D FSE showed more anatomical details, while in 3D FSE, some blurring occurred. DWI showed high LN contrast, but suffered from geometric distortions and low resolution. Fat suppression by mDixon was the most reliable in regions with magnetic-field inhomogeneities. The FSE sequences showed the highest sensitivity for LN detection. Conclusion: MRI of regional LNs was achieved in volunteers. The FSE techniques were robust and the most sensitive. Our optimized MRI sequences can facilitate direct delineation of individual LNs. This can Result in smaller target volumes and reduced toxicity in regional RT compared to standard CT planning.« less

Reliability of high- and low-field magnetic resonance imaging systems for detection of cartilage and bone lesions in the equine cadaver fetlock.

PubMed

Smith, M A; Dyson, S J; Murray, R C

2012-11-01

To determine the reliability of 2 magnetic resonance imaging (MRI) systems for detection of cartilage and bone lesions of the equine fetlock. To test the hypotheses that lesions in cartilage, subchondral and trabecular bone of the equine fetlock verified using histopathology can be detected on high- and low-field MR images with a low incidence of false positive or negative results; that low-field images are less reliable than high-field images for detection of cartilage lesions; and that combining results of interpretation from different pulse sequences increases detection of cartilage lesions. High- and low-field MRI was performed on 19 limbs from horses identified with fetlock lameness prior to euthanasia. Grading systems were used to score cartilage, subchondral and trabecular bone on MR images and histopathology. Sensitivity and specificity were calculated for images. High-field T2*-weighted gradient echo (T2*W-GRE) and low-field T2-weighted fast spin echo (T2W-FSE) images had high sensitivity but low specificity for detection of cartilage lesions. All pulse sequences had high sensitivity and low-moderate specificity for detection of subchondral bone lesions and moderate sensitivity and moderate-high specificity for detection of trabecular bone lesions (histopathology as gold standard). For detection of lesions of trabecular bone low-field T2*W-GRE images had higher sensitivity and specificity than T2W-FSE images. There is high likelihood of false positive results using high- or low-field MRI for detection of cartilage lesions and moderate-high likelihood of false positive results for detection of subchondral bone lesions compared with histopathology. Combining results of interpretation from different pulse sequences did not increase detection of cartilage lesions. MRI interpretation of trabecular bone was more reliable than cartilage or subchondral bone in both MR systems. Independent interpretation of a variety of pulse sequences may maximise detection of cartilage and bone lesions in the fetlock. Clinicians should be aware of potential false positive and negative results. © 2012 EVJ Ltd.

Fast reconstruction of off-axis digital holograms based on digital spatial multiplexing.

PubMed

Sha, Bei; Liu, Xuan; Ge, Xiao-Lu; Guo, Cheng-Shan

2014-09-22

A method for fast reconstruction of off-axis digital holograms based on digital multiplexing algorithm is proposed. Instead of the existed angular multiplexing (AM), the new method utilizes a spatial multiplexing (SM) algorithm, in which four off-axis holograms recorded in sequence are synthesized into one SM function through multiplying each hologram with a tilted plane wave and then adding them up. In comparison with the conventional methods, the SM algorithm simplifies two-dimensional (2-D) Fourier transforms (FTs) of four N*N arrays into a 1.25-D FTs of one N*N arrays. Experimental results demonstrate that, using the SM algorithm, the computational efficiency can be improved and the reconstructed wavefronts keep the same quality as those retrieved based on the existed AM method. This algorithm may be useful in design of a fast preview system of dynamic wavefront imaging in digital holography.

FliMax, a novel stimulus device for panoramic and highspeed presentation of behaviourally generated optic flow.

PubMed

Lindemann, J P; Kern, R; Michaelis, C; Meyer, P; van Hateren, J H; Egelhaaf, M

2003-03-01

A high-speed panoramic visual stimulation device is introduced which is suitable to analyse visual interneurons during stimulation with rapid image displacements as experienced by fast moving animals. The responses of an identified motion sensitive neuron in the visual system of the blowfly to behaviourally generated image sequences are very complex and hard to predict from the established input circuitry of the neuron. This finding suggests that the computational significance of visual interneurons can only be assessed if they are characterised not only by conventional stimuli as are often used for systems analysis, but also by behaviourally relevant input.

Accelerating acquisition strategies for low-frequency conductivity imaging using MREIT

NASA Astrophysics Data System (ADS)

Song, Yizhuang; Seo, Jin Keun; Chauhan, Munish; Indahlastari, Aprinda; Ashok Kumar, Neeta; Sadleir, Rosalind

2018-02-01

We sought to improve efficiency of magnetic resonance electrical impedance tomography data acquisition so that fast conductivity changes or electric field variations could be monitored. Undersampling of k-space was used to decrease acquisition times in spin-echo-based sequences by a factor of two. Full MREIT data were reconstructed using continuity assumptions and preliminary scans gathered without current. We found that phase data were reconstructed faithfully from undersampled data. Conductivity reconstructions of phantom data were also possible. Therefore, undersampled k-space methods can potentially be used to accelerate MREIT acquisition. This method could be an advantage in imaging real-time conductivity changes with MREIT.

Breath-held MR Cholangiopancreatography (MRCP) using a 3D Dixon fat–water separated balanced steady state free precession sequence

PubMed Central

Glockner, James F.; Saranathan, Manojkumar; Bayram, Ersin; Lee, Christine U.

2014-01-01

A novel 3D breath-held Dixon fat–water separated balanced steady state free precession (b-SSFP) sequence for MR cholangiopancreatography (MRCP) is described and its potential clinical utility assessed in a series of patients. The main motivation is to develop a robust breath-held alternative to the respiratory gated 3D Fast Spin Echo (FSE) sequence, the current clinical sequence of choice for MRCP. Respiratory gated acquisitions are susceptible to motion artifacts and blurring in patients with significant diaphragmatic drift, erratic respiratory rhythms or sleep apnea. A two point Dixon fat–water separation scheme was developed which eliminates signal loss arising from B0 inhomogeneity effects and minimizes artifacts from perturbation of the b-SSFP steady state. Preliminary results from qualitative analysis of 49 patients demonstrate robust performance of the 3D Dixon b-SSFP sequence with diagnostic image quality acquired in a 20–24 s breath-hold. PMID:23876262

Towards fast and accurate temperature mapping with proton resonance frequency-based MR thermometry

PubMed Central

Yuan, Jing; Mei, Chang-Sheng; Panych, Lawrence P.; McDannold, Nathan J.; Madore, Bruno

2012-01-01

The capability to image temperature is a very attractive feature of MRI and has been actively exploited for guiding minimally-invasive thermal therapies. Among many MR-based temperature-sensitive approaches, proton resonance frequency (PRF) thermometry provides the advantage of excellent linearity of signal with temperature over a large temperature range. Furthermore, the PRF shift has been shown to be fairly independent of tissue type and thermal history. For these reasons, PRF method has evolved into the most widely used MR-based thermometry method. In the present paper, the basic principles of PRF-based temperature mapping will be reviewed, along with associated pulse sequence designs. Technical advancements aimed at increasing the imaging speed and/or temperature accuracy of PRF-based thermometry sequences, such as image acceleration, fat suppression, reduced field-of-view imaging, as well as motion tracking and correction, will be discussed. The development of accurate MR thermometry methods applicable to moving organs with non-negligible fat content represents a very challenging goal, but recent developments suggest that this goal may be achieved. If so, MR-guided thermal therapies may be expected to play an increasingly-important therapeutic and palliative role, as a minimally-invasive alternative to surgery. PMID:22773966

Acquisition of New DNA Sequences After Infection of Chicken Cells with Avian Myeloblastosis Virus

PubMed Central

Shoyab, M.; Baluda, M. A.; Evans, R.

1974-01-01

DNA-RNA hybridization studies between 70S RNA from avian myeloblastosis virus (AMV) and an excess of DNA from (i) AMV-induced leukemic chicken myeloblasts or (ii) a mixture of normal and of congenitally infected K-137 chicken embryos producing avian leukosis viruses revealed the presence of fast- and slow-hybridizing virus-specific DNA sequences. However, the leukemic cells contained twice the level of AMV-specific DNA sequences observed in normal chicken embryonic cells. The fast-reacting sequences were two to three times more numerous in leukemic DNA than in DNA from the mixed embryos. The slow-reacting sequences had a reiteration frequency of approximately 9 and 6, in the two respective systems. Both the fast- and the slow-reacting DNA sequences in leukemic cells exhibited a higher Tm (2 C) than the respective DNA sequences in normal cells. In normal and leukemic cells the slow hybrid sequences appeared to have a Tm which was 2 C higher than that of the fast hybrid sequences. Individual non-virus-producing chicken embryos, either group-specific antigen positive or negative, contained 40 to 100 copies of the fast sequences and 2 to 6 copies of the slowly hybridizing sequences per cell genome. Normal rat cells did not contain DNA that hybridized with AMV RNA, whereas non-virus-producing rat cells transformed by B-77 avian sarcoma virus contained only the slowly reacting sequences. The results demonstrate that leukemic cells transformed by AMV contain new AMV-specific DNA sequences which were not present before infection. PMID:16789139

Motion Artifact Reduction in Pediatric Diffusion Tensor Imaging Using Fast Prospective Correction

PubMed Central

Alhamud, A.; Taylor, Paul A.; Laughton, Barbara; van der Kouwe, André J.W.; Meintjes, Ernesta M.

2014-01-01

Purpose To evaluate the patterns of head motion in scans of young children and to examine the influence of corrective techniques, both qualitatively and quantitatively. We investigate changes that both retrospective (with and without diffusion table reorientation) and prospective (implemented with a short navigator sequence) motion correction induce in the resulting diffusion tensor measures. Materials and Methods Eighteen pediatric subjects (aged 5–6 years) were scanned using 1) a twice-refocused, 2D diffusion pulse sequence, 2) a prospectively motion-corrected, navigated diffusion sequence with reacquisition of a maximum of five corrupted diffusion volumes, and 3) a T1-weighted structural image. Mean fractional anisotropy (FA) values in white and gray matter regions, as well as tractography in the brainstem and projection fibers, were evaluated to assess differences arising from retrospective (via FLIRT in FSL) and prospective motion correction. In addition to human scans, a stationary phantom was also used for further evaluation. Results In several white and gray matter regions retrospective correction led to significantly (P < 0.05) reduced FA means and altered distributions compared to the navigated sequence. Spurious tractographic changes in the retrospectively corrected data were also observed in subject data, as well as in phantom and simulated data. Conclusion Due to the heterogeneity of brain structures and the comparatively low resolution (~2 mm) of diffusion data using 2D single shot sequencing, retrospective motion correction is susceptible to distortion from partial voluming. These changes often negatively bias diffusion tensor imaging parameters. Prospective motion correction was shown to produce smaller changes. PMID:24935904

Motion artifact reduction in pediatric diffusion tensor imaging using fast prospective correction.

PubMed

Alhamud, A; Taylor, Paul A; Laughton, Barbara; van der Kouwe, André J W; Meintjes, Ernesta M

2015-05-01

To evaluate the patterns of head motion in scans of young children and to examine the influence of corrective techniques, both qualitatively and quantitatively. We investigate changes that both retrospective (with and without diffusion table reorientation) and prospective (implemented with a short navigator sequence) motion correction induce in the resulting diffusion tensor measures. Eighteen pediatric subjects (aged 5-6 years) were scanned using 1) a twice-refocused, 2D diffusion pulse sequence, 2) a prospectively motion-corrected, navigated diffusion sequence with reacquisition of a maximum of five corrupted diffusion volumes, and 3) a T1 -weighted structural image. Mean fractional anisotropy (FA) values in white and gray matter regions, as well as tractography in the brainstem and projection fibers, were evaluated to assess differences arising from retrospective (via FLIRT in FSL) and prospective motion correction. In addition to human scans, a stationary phantom was also used for further evaluation. In several white and gray matter regions retrospective correction led to significantly (P < 0.05) reduced FA means and altered distributions compared to the navigated sequence. Spurious tractographic changes in the retrospectively corrected data were also observed in subject data, as well as in phantom and simulated data. Due to the heterogeneity of brain structures and the comparatively low resolution (∼2 mm) of diffusion data using 2D single shot sequencing, retrospective motion correction is susceptible to distortion from partial voluming. These changes often negatively bias diffusion tensor imaging parameters. Prospective motion correction was shown to produce smaller changes. © 2014 Wiley Periodicals, Inc.

The effect of crack cocaine addiction and age on the microstructure and morphology of the human striatum and thalamus using shape analysis and fast diffusion kurtosis imaging.

PubMed

Garza-Villarreal, E A; Chakravarty, M M; Hansen, B; Eskildsen, S F; Devenyi, G A; Castillo-Padilla, D; Balducci, T; Reyes-Zamorano, E; Jespersen, S N; Perez-Palacios, P; Patel, R; Gonzalez-Olvera, J J

2017-05-09

The striatum and thalamus are subcortical structures intimately involved in addiction. The morphology and microstructure of these have been studied in murine models of cocaine addiction (CA), showing an effect of drug use, but also chronological age in morphology. Human studies using non-invasive magnetic resonance imaging (MRI) have shown inconsistencies in volume changes, and have also shown an age effect. In this exploratory study, we used MRI-based volumetric and novel shape analysis, as well as a novel fast diffusion kurtosis imaging sequence to study the morphology and microstructure of striatum and thalamus in crack CA compared to matched healthy controls (HCs), while investigating the effect of age and years of cocaine consumption. We did not find significant differences in volume and mean kurtosis (MKT) between groups. However, we found significant contraction of nucleus accumbens in CA compared to HCs. We also found significant age-related changes in volume and MKT of CA in striatum and thalamus that are different to those seen in normal aging. Interestingly, we found different effects and contributions of age and years of consumption in volume, displacement and MKT changes, suggesting that each measure provides different but complementing information about morphological brain changes, and that not all changes are related to the toxicity or the addiction to the drug. Our findings suggest that the use of finer methods and sequences provides complementing information about morphological and microstructural changes in CA, and that brain alterations in CA are related cocaine use and age differently.

The effect of crack cocaine addiction and age on the microstructure and morphology of the human striatum and thalamus using shape analysis and fast diffusion kurtosis imaging

PubMed Central

Garza-Villarreal, E A; Chakravarty, MM; Hansen, B; Eskildsen, S F; Devenyi, G A; Castillo-Padilla, D; Balducci, T; Reyes-Zamorano, E; Jespersen, S N; Perez-Palacios, P; Patel, R; Gonzalez-Olvera, J J

2017-01-01

The striatum and thalamus are subcortical structures intimately involved in addiction. The morphology and microstructure of these have been studied in murine models of cocaine addiction (CA), showing an effect of drug use, but also chronological age in morphology. Human studies using non-invasive magnetic resonance imaging (MRI) have shown inconsistencies in volume changes, and have also shown an age effect. In this exploratory study, we used MRI-based volumetric and novel shape analysis, as well as a novel fast diffusion kurtosis imaging sequence to study the morphology and microstructure of striatum and thalamus in crack CA compared to matched healthy controls (HCs), while investigating the effect of age and years of cocaine consumption. We did not find significant differences in volume and mean kurtosis (MKT) between groups. However, we found significant contraction of nucleus accumbens in CA compared to HCs. We also found significant age-related changes in volume and MKT of CA in striatum and thalamus that are different to those seen in normal aging. Interestingly, we found different effects and contributions of age and years of consumption in volume, displacement and MKT changes, suggesting that each measure provides different but complementing information about morphological brain changes, and that not all changes are related to the toxicity or the addiction to the drug. Our findings suggest that the use of finer methods and sequences provides complementing information about morphological and microstructural changes in CA, and that brain alterations in CA are related cocaine use and age differently. PMID:28485734

Lung MRI at 1.5 and 3 Tesla: observer preference study and lesion contrast using five different pulse sequences.

PubMed

Fink, Christian; Puderbach, Michael; Biederer, Juergen; Fabel, Michael; Dietrich, Olaf; Kauczor, Hans-Ulrich; Reiser, Maximilian F; Schönberg, Stefan O

2007-06-01

To compare the image quality and lesion contrast of lung MRI using 5 different pulse sequences at 1.5 T and 3 T. Lung MRI was performed at 1.5 T and 3 T using 5 pulse sequences which have been previously proposed for lung MRI: 3D volumetric interpolated breath-hold examination (VIBE), true fast imaging with steady-state precession (TrueFISP), half-Fourier single-shot turbo spin-echo (HASTE), short tau inversion recovery (STIR), T2-weighted turbo spin-echo (TSE). In addition to 4 healthy volunteers, 5 porcine lungs were examined in a dedicated chest phantom. Lung pathology (nodules and infiltrates) was simulated in the phantom by intrapulmonary and intrabronchial injections of agarose. CT was performed in the phantom for correlation. Image quality of the sequences was ranked in a side-by-side comparison by 3 blinded radiologists regarding the delineation of pulmonary and mediastinal anatomy, conspicuity of pulmonary nodules and infiltrates, and presence of artifacts. The contrast of nodules and infiltrates (CNODULES and CINFILTRATES) defined by the ratio of the signal intensities of the lesion and adjacent normal lung parenchyma was determined. There were no relevant differences regarding the preference for the individual sequences between both field strengths. TSE was the preferred sequence for the visualization of the mediastinum at both field strengths. For the visualization of lung parenchyma the observers preferred TrueFISP in volunteers and TSE in the phantom studies. At both field strengths VIBE achieved the best rating for the depiction of nodules, whereas HASTE was rated best for the delineation of infiltrates. TrueFISP had the fewest artifacts in volunteers, whereas STIR showed the fewest artifacts in the phantom. For all but the TrueFISP sequence the lesion contrast increased from 1.5 T to 3 T. At both field strengths VIBE showed the highest CNODULES (6.6 and 7.1) and HASTE the highest CINFILTRATES (6.1 and 6.3). The imaging characteristics of different pulse sequences used for lung MRI do not substantially differ between 1.5 T and 3 T. A higher lesion contrast can be expected at 3 T.

[Magnetic resonance in traumatic brain injury: A comparative study of the different conventional magnetic resonance imaging sequences and their diagnostic value in diffuse axonal injury].

PubMed

Cicuendez, Marta; Castaño-León, Ana; Ramos, Ana; Hilario, Amaya; Gómez, Pedro A; Lagares, Alfonso

To compare the identification capability of traumatic axonal injury (TAI) by different sequences on conventional magnetic resonance (MR) studies in traumatic brain injury (TBI) patients. We retropectevely analyzed 264 TBI patients to whom a MR had been performed in the first 60 days after trauma. All clinical variables related to prognosis were registered, as well as the data from the initial computed tomography. The MR imaging protocol consisted of a 3-plane localizer sequence T1-weighted and T2-weighted fast spin-echo, FLAIR and gradient-echo images (GRET2*). TAI lesions were classified according to Gentry and Firsching classifications. We calculated weighted kappa coefficients and the area under the ROC curve for each MR sequence. A multivariable analyses was performed to correlate MR findings in each sequence with the final outcome of the patients. TAI lesions were adequately visualized on T2, FLAIR and GRET2* sequences in more than 80% of the studies. Subcortical TAI lesions were well on FLAIR and GRET2* sequences visualized hemorrhagic TAI lesions. We saw that these MR sequences had a high inter-rater agreement for TAI diagnosis (0.8). T2 sequence presented the highest value on ROC curve in Gentry (0.68, 95%CI: 0.61-0.76, p<0.001, Nagerlkerke-R 2 0.26) and Firsching classifications (0.64, 95%CI 0.57-0.72, p<0.001, Nagerlkerke-R 2 0.19), followed by FLAIR and GRET2* sequences. Both classifications determined by each of these sequences were associated with poor outcome after performing a multivariable analyses adjusted for prognostic factors (p<0.02). We recommend to perform conventional MR study in subacute phase including T2, FLAIR and GRET2* sequences for visualize TAI lesions. These MR findings added prognostic information in TBI patients. Copyright © 2017 Sociedad Española de Neurocirugía. Publicado por Elsevier España, S.L.U. All rights reserved.

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.

NIR hyperspectral compressive imager based on a modified Fabry–Perot resonator

NASA Astrophysics Data System (ADS)

Oiknine, Yaniv; August, Isaac; Blumberg, Dan G.; Stern, Adrian

2018-04-01

The acquisition of hyperspectral (HS) image datacubes with available 2D sensor arrays involves a time consuming scanning process. In the last decade, several compressive sensing (CS) techniques were proposed to reduce the HS acquisition time. In this paper, we present a method for near-infrared (NIR) HS imaging which relies on our rapid CS resonator spectroscopy technique. Within the framework of CS, and by using a modified Fabry–Perot resonator, a sequence of spectrally modulated images is used to recover NIR HS datacubes. Owing to the innovative CS design, we demonstrate the ability to reconstruct NIR HS images with hundreds of spectral bands from an order of magnitude fewer measurements, i.e. with a compression ratio of about 10:1. This high compression ratio, together with the high optical throughput of the system, facilitates fast acquisition of large HS datacubes.

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.

Evaluation of heart perfusion in patients with acute myocardial infarction using dynamic contrast-enhanced magnetic resonance imaging.

PubMed

Nielsen, Gitte; Fritz-Hansen, Thomas; Dirks, Christina G; Jensen, Gorm B; Larsson, Henrik B W

2004-09-01

To investigate the diagnostic ability of quantitative magnetic resonance imaging (MRI) heart perfusion in acute heart patients, a fast, multislice dynamic contrast-enhanced MRI sequence was applied to patients with acute myocardial infarction. Seven patients with acute transmural myocardial infarction were studied using a Turbo-fast low angle shot (FLASH) MRI sequence to monitor the first pass of an extravascular contrast agent (CA), gadolinium diethylene triamine pentaacetic acid (Gd-DTPA). Quantitation of perfusion, expressed as Ki (mL/100 g/minute), in five slices, each having 60 sectors, provided an estimation of the severity and extent of the perfusion deficiency. Reperfusion was assessed both by noninvasive criteria and by coronary angiography (CAG). The Ki maps clearly delineated the infarction in all patients. Thrombolytic treatment was clearly beneficial in one case, but had no effect in the two other cases. Over the time-course of the study, normal perfusion values were not reestablished following thrombolytic treatment in all cases investigated. This study shows that quantitative MRI perfusion values can be obtained from acutely ill patients following acute myocardial infarction. The technique provides information on both the volume and severity of affected myocardial tissue, enabling the power of treatment regimes to be assessed objectively, and this approach should aid individual patient stratification and prognosis. Copyright 2004 Wiley-Liss, Inc.

Digital readout for image converter cameras

NASA Astrophysics Data System (ADS)

Honour, Joseph

1991-04-01

There is an increasing need for fast and reliable analysis of recorded sequences from image converter cameras so that experimental information can be readily evaluated without recourse to more time consuming photographic procedures. A digital readout system has been developed using a randomly triggerable high resolution CCD camera, the output of which is suitable for use with IBM AT compatible PC. Within half a second from receipt of trigger pulse, the frame reformatter displays the image and transfer to storage media can be readily achieved via the PC and dedicated software. Two software programmes offer different levels of image manipulation which includes enhancement routines and parameter calculations with accuracy down to pixel levels. Hard copy prints can be acquired using a specially adapted Polaroid printer, outputs for laser and video printer extend the overall versatility of the system.

FAST: FAST Analysis of Sequences Toolbox

PubMed Central

Lawrence, Travis J.; Kauffman, Kyle T.; Amrine, Katherine C. H.; Carper, Dana L.; Lee, Raymond S.; Becich, Peter J.; Canales, Claudia J.; Ardell, David H.

2015-01-01

FAST (FAST Analysis of Sequences Toolbox) provides simple, powerful open source command-line tools to filter, transform, annotate and analyze biological sequence data. Modeled after the GNU (GNU's Not Unix) Textutils such as grep, cut, and tr, FAST tools such as fasgrep, fascut, and fastr make it easy to rapidly prototype expressive bioinformatic workflows in a compact and generic command vocabulary. Compact combinatorial encoding of data workflows with FAST commands can simplify the documentation and reproducibility of bioinformatic protocols, supporting better transparency in biological data science. Interface self-consistency and conformity with conventions of GNU, Matlab, Perl, BioPerl, R, and GenBank help make FAST easy and rewarding to learn. FAST automates numerical, taxonomic, and text-based sorting, selection and transformation of sequence records and alignment sites based on content, index ranges, descriptive tags, annotated features, and in-line calculated analytics, including composition and codon usage. Automated content- and feature-based extraction of sites and support for molecular population genetic statistics make FAST useful for molecular evolutionary analysis. FAST is portable, easy to install and secure thanks to the relative maturity of its Perl and BioPerl foundations, with stable releases posted to CPAN. Development as well as a publicly accessible Cookbook and Wiki are available on the FAST GitHub repository at https://github.com/tlawrence3/FAST. The default data exchange format in FAST is Multi-FastA (specifically, a restriction of BioPerl FastA format). Sanger and Illumina 1.8+ FastQ formatted files are also supported. FAST makes it easier for non-programmer biologists to interactively investigate and control biological data at the speed of thought. PMID:26042145

Segmentation of solid subregion of high grade gliomas in MRI images based on active contour model (ACM)

NASA Astrophysics Data System (ADS)

Seow, P.; Win, M. T.; Wong, J. H. D.; Abdullah, N. A.; Ramli, N.

2016-03-01

Gliomas are tumours arising from the interstitial tissue of the brain which are heterogeneous, infiltrative and possess ill-defined borders. Tumour subregions (e.g. solid enhancing part, edema and necrosis) are often used for tumour characterisation. Tumour demarcation into substructures facilitates glioma staging and provides essential information. Manual segmentation had several drawbacks that include laborious, time consuming, subjected to intra and inter-rater variability and hindered by diversity in the appearance of tumour tissues. In this work, active contour model (ACM) was used to segment the solid enhancing subregion of the tumour. 2D brain image acquisition data using 3T MRI fast spoiled gradient echo sequence in post gadolinium of four histologically proven high-grade glioma patients were obtained. Preprocessing of the images which includes subtraction and skull stripping were performed and then followed by ACM segmentation. The results of the automatic segmentation method were compared against the manual delineation of the tumour by a trainee radiologist. Both results were further validated by an experienced neuroradiologist and a brief quantitative evaluations (pixel area and difference ratio) were performed. Preliminary results of the clinical data showed the potential of ACM model in the application of fast and large scale tumour segmentation in medical imaging.

Bacterial identification and subtyping using DNA microarray and DNA sequencing.

PubMed

Al-Khaldi, Sufian F; Mossoba, Magdi M; Allard, Marc M; Lienau, E Kurt; Brown, Eric D

2012-01-01

The era of fast and accurate discovery of biological sequence motifs in prokaryotic and eukaryotic cells is here. The co-evolution of direct genome sequencing and DNA microarray strategies not only will identify, isotype, and serotype pathogenic bacteria, but also it will aid in the discovery of new gene functions by detecting gene expressions in different diseases and environmental conditions. Microarray bacterial identification has made great advances in working with pure and mixed bacterial samples. The technological advances have moved beyond bacterial gene expression to include bacterial identification and isotyping. Application of new tools such as mid-infrared chemical imaging improves detection of hybridization in DNA microarrays. The research in this field is promising and future work will reveal the potential of infrared technology in bacterial identification. On the other hand, DNA sequencing by using 454 pyrosequencing is so cost effective that the promise of $1,000 per bacterial genome sequence is becoming a reality. Pyrosequencing technology is a simple to use technique that can produce accurate and quantitative analysis of DNA sequences with a great speed. The deposition of massive amounts of bacterial genomic information in databanks is creating fingerprint phylogenetic analysis that will ultimately replace several technologies such as Pulsed Field Gel Electrophoresis. In this chapter, we will review (1) the use of DNA microarray using fluorescence and infrared imaging detection for identification of pathogenic bacteria, and (2) use of pyrosequencing in DNA cluster analysis to fingerprint bacterial phylogenetic trees.

Noninvasive identification of peripheral vessels of oral and maxillofacial regions by using electrocardiography-triggered three-dimensional fast asymmetric spin-echo sequences.

PubMed

Tanaka, Tatsurou; Oda, Masafumi; Kito, Shinji; Wakasugi-Sato, Nao; Matsumoto-Takeda, Shinobu; Otsuka, Kozue; Yoshioka, Izumi; Habu, Manabu; Kokuryo, Shinya; Kodama, Masaaki; Nogami, Shinnosuke; Miyamoto, Ikuya; Yamamoto, Noriaki; Ishikawa, Ayataka; Matsuo, Kou; Shiiba, Shunji; Seta, Yuji; Yamashita, Yoshihiro; Takahashi, Tetsu; Tominaga, Kazuhiro; Morimoto, Yasuhiro

2011-10-01

The aim of this study was to evaluate the 3-dimensional images of thinner main peripheral vessels in oral and maxillofacial regions made without contrast medium by using a new technique, fresh blood imaging (FBI). A second objective was to discern arteries from veins by using the combination of FBI with the subtraction technique. Images from FBI were compared with those from 3-dimensional phase-contrast magnetic resonance angiography (MRA) of blood vessels in 20 healthy subjects. All images were scored for visualization and image quality of the main blood vessels. In addition, appropriate flow-spoiled gradient pulses were applied to differentiate arteries from veins in the peripheral vasculature using a combination of FBI sequences and subtraction between systole- and diastole-triggered images. The scores of MRA using FBI for the visualization of thin blood vessels were significantly better than those using phase contrast, whereas scores for the visualization of main blood vessels were equal. Additionally, we succeeded in our initial attempt to differentiate arteries from veins with a reasonable acquisition time. Our initial experience shows that FBI could be a useful method to identify 3-dimensional vasculature and to differentiate arteries from veins among thinner peripheral vessels in the oral and maxillofacial regions without using contrast medium. Copyright © 2011 Mosby, Inc. All rights reserved.

SYNMAG PHOTOMETRY: A FAST TOOL FOR CATALOG-LEVEL MATCHED COLORS OF EXTENDED SOURCES

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

Bundy, Kevin; Yasuda, Naoki; Hogg, David W.

2012-12-01

Obtaining reliable, matched photometry for galaxies imaged by different observatories represents a key challenge in the era of wide-field surveys spanning more than several hundred square degrees. Methods such as flux fitting, profile fitting, and PSF homogenization followed by matched-aperture photometry are all computationally expensive. We present an alternative solution called 'synthetic aperture photometry' that exploits galaxy profile fits in one band to efficiently model the observed, point-spread-function-convolved light profile in other bands and predict the flux in arbitrarily sized apertures. Because aperture magnitudes are the most widely tabulated flux measurements in survey catalogs, producing synthetic aperture magnitudes (SYNMAGs) enablesmore » very fast matched photometry at the catalog level, without reprocessing imaging data. We make our code public and apply it to obtain matched photometry between Sloan Digital Sky Survey ugriz and UKIDSS YJHK imaging, recovering red-sequence colors and photometric redshifts with a scatter and accuracy as good as if not better than FWHM-homogenized photometry from the GAMA Survey. Finally, we list some specific measurements that upcoming surveys could make available to facilitate and ease the use of SYNMAGs.« less

A Fast Variant of 1H Spectroscopic U-FLARE Imaging Using Adjusted Chemical Shift Phase Encoding

NASA Astrophysics Data System (ADS)

Ebel, Andreas; Dreher, Wolfgang; Leibfritz, Dieter

2000-02-01

So far, fast spectroscopic imaging (SI) using the U-FLARE sequence has provided metabolic maps indirectly via Fourier transformation (FT) along the chemical shift (CS) dimension and subsequent peak integration. However, a large number of CS encoding steps Nω is needed to cover the spectral bandwidth and to achieve sufficient spectral resolution for peak integration even if the number of resonance lines is small compared to Nω and even if only metabolic images are of interest and not the spectra in each voxel. Other reconstruction algorithms require extensive prior knowledge, starting values, and/or model functions. An adjusted CS phase encoding scheme (APE) can be used to overcome these drawbacks. It incorporates prior knowledge only about the resonance frequencies present in the sample. Thus, Nω can be reduced by a factor of 4 for many 1H in vivo studies while no spectra have to be reconstructed, and no additional user interaction, prior knowledge, starting values, or model function are required. Phantom measurements and in vivo experiments on rat brain have been performed at 4.7 T to test the feasibility of the method for proton SI.

Congenital heart disease in adults: Quantitative and qualitative evaluation of IR FLASH and IR SSFP MRA techniques using a blood pool contrast agent in the steady state and comparison to first pass MRA.

PubMed

Febbo, Jennifer A; Galizia, Mauricio S; Murphy, Ian G; Popescu, Andrada; Bi, Xiaoming; Turin, Alexander; Collins, Jeremy; Markl, Michael; Edelman, Robert R; Carr, James C

2015-10-01

To evaluate magnetic resonance angiography sequences during the contrast steady-state (SS-MRA) using inversion recovery (IR) with fast low-angle shot (IR-FLASH) or steady-state free precession (IR-SSFP) read-outs, following the injection of a blood-pool contrast agent, and compare them to first-pass MR angiography (FP-MRA) in adults with congenital heart disease (CHD). Twenty-three adult patients with CHD who underwent both SS-MRA and FP-MRA using a 1.5-T scanner were retrospectively identified. Signal-to-noise and contrast-to-noise ratios were obtained at eight locations within the aorta and pulmonary vessels.. Image quality and the presence of artifacts were subjectively assessed by two radiologists. The presence of pathology was noted and given a confidence score. There was no difference in vessel dimensions among the sequences. IR-SSFP showed better image quality and fewer artifacts than IR-FLASH and FP-MRA. Confidence scores were significantly higher for SS-MRA compared to FP-MRA. Seven cases (30.4%) had findings detected at SS-MRA that were not detected at FP-MRA, and 2 cases (8.7%) had findings detected by IR-SSFP only. SS-MRA of the thoracic vasculature using a blood pool contrast agent offers superior image quality and reveals more abnormalities compared to standard FP-MRA in adults with CHD, and it is best achieved with an IR-SSFP sequence. These sequences could lead to increased detection rates of abnormalities and provide a simpler protocol image acquisition. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Fast diffusion kurtosis imaging (DKI) with Inherent COrrelation-based Normalization (ICON) enhances automatic segmentation of heterogeneous diffusion MRI lesion in acute stroke.

PubMed

Zhou, Iris Yuwen; Guo, Yingkun; Igarashi, Takahiro; Wang, Yu; Mandeville, Emiri; Chan, Suk-Tak; Wen, Lingyi; Vangel, Mark; Lo, Eng H; Ji, Xunming; Sun, Phillip Zhe

2016-12-01

Diffusion kurtosis imaging (DKI) has been shown to augment diffusion-weighted imaging (DWI) for the definition of irreversible ischemic injury. However, the complexity of cerebral structure/composition makes the kurtosis map heterogeneous, limiting the specificity of kurtosis hyperintensity to acute ischemia. We propose an Inherent COrrelation-based Normalization (ICON) analysis to suppress the intrinsic kurtosis heterogeneity for improved characterization of heterogeneous ischemic tissue injury. Fast DKI and relaxation measurements were performed on normal (n = 10) and stroke rats following middle cerebral artery occlusion (MCAO) (n = 20). We evaluated the correlations between mean kurtosis (MK), mean diffusivity (MD) and fractional anisotropy (FA) derived from the fast DKI sequence and relaxation rates R 1 and R 2 , and found a highly significant correlation between MK and R 1 (p < 0.001). We showed that ICON analysis suppressed the intrinsic kurtosis heterogeneity in normal cerebral tissue, enabling automated tissue segmentation in an animal stroke model. We found significantly different kurtosis and diffusivity lesion volumes: 147 ± 59 and 180 ± 66 mm 3 , respectively (p = 0.003, paired t-test). The ratio of kurtosis to diffusivity lesion volume was 84% ± 19% (p < 0.001, one-sample t-test). We found that relaxation-normalized MK (RNMK), but not MD, values were significantly different between kurtosis and diffusivity lesions (p < 0.001, analysis of variance). Our study showed that fast DKI with ICON analysis provides a promising means of demarcation of heterogeneous DWI stroke lesions. Copyright © 2016 John Wiley & Sons, Ltd.

Positive Selection Underlies Faster-Z Evolution of Gene Expression in Birds.

PubMed

Dean, Rebecca; Harrison, Peter W; Wright, Alison E; Zimmer, Fabian; Mank, Judith E

2015-10-01

The elevated rate of evolution for genes on sex chromosomes compared with autosomes (Fast-X or Fast-Z evolution) can result either from positive selection in the heterogametic sex or from nonadaptive consequences of reduced relative effective population size. Recent work in birds suggests that Fast-Z of coding sequence is primarily due to relaxed purifying selection resulting from reduced relative effective population size. However, gene sequence and gene expression are often subject to distinct evolutionary pressures; therefore, we tested for Fast-Z in gene expression using next-generation RNA-sequencing data from multiple avian species. Similar to studies of Fast-Z in coding sequence, we recover clear signatures of Fast-Z in gene expression; however, in contrast to coding sequence, our data indicate that Fast-Z in expression is due to positive selection acting primarily in females. In the soma, where gene expression is highly correlated between the sexes, we detected Fast-Z in both sexes, although at a higher rate in females, suggesting that many positively selected expression changes in females are also expressed in males. In the gonad, where intersexual correlations in expression are much lower, we detected Fast-Z for female gene expression, but crucially, not males. This suggests that a large amount of expression variation is sex-specific in its effects within the gonad. Taken together, our results indicate that Fast-Z evolution of gene expression is the product of positive selection acting on recessive beneficial alleles in the heterogametic sex. More broadly, our analysis suggests that the adaptive potential of Z chromosome gene expression may be much greater than that of gene sequence, results which have important implications for the role of sex chromosomes in speciation and sexual selection. © The Author 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Placental fetal stem segmentation in a sequence of histology images

NASA Astrophysics Data System (ADS)

Athavale, Prashant; Vese, Luminita A.

2012-02-01

Recent research in perinatal pathology argues that analyzing properties of the placenta may reveal important information on how certain diseases progress. One important property is the structure of the placental fetal stems. Analysis of the fetal stems in a placenta could be useful in the study and diagnosis of some diseases like autism. To study the fetal stem structure effectively, we need to automatically and accurately track fetal stems through a sequence of digitized hematoxylin and eosin (H&E) stained histology slides. There are many problems in successfully achieving this goal. A few of the problems are: large size of images, misalignment of the consecutive H&E slides, unpredictable inaccuracies of manual tracing, very complicated texture patterns of various tissue types without clear characteristics, just to name a few. In this paper we propose a novel algorithm to achieve automatic tracing of the fetal stem in a sequence of H&E images, based on an inaccurate manual segmentation of a fetal stem in one of the images. This algorithm combines global affine registration, local non-affine registration and a novel 'dynamic' version of the active contours model without edges. We first use global affine image registration of all the images based on displacement, scaling and rotation. This gives us approximate location of the corresponding fetal stem in the image that needs to be traced. We then use the affine registration algorithm "locally" near this location. At this point, we use a fast non-affine registration based on L2-similarity measure and diffusion regularization to get a better location of the fetal stem. Finally, we have to take into account inaccuracies in the initial tracing. This is achieved through a novel dynamic version of the active contours model without edges where the coefficients of the fitting terms are computed iteratively to ensure that we obtain a unique stem in the segmentation. The segmentation thus obtained can then be used as an initial guess to obtain segmentation in the rest of the images in the sequence. This constitutes an important step in the extraction and understanding of the fetal stem vasculature.

Sensitivity-encoded (SENSE) proton echo-planar spectroscopic imaging (PEPSI) in the human brain.

PubMed

Lin, Fa-Hsuan; Tsai, Shang-Yueh; Otazo, Ricardo; Caprihan, Arvind; Wald, Lawrence L; Belliveau, John W; Posse, Stefan

2007-02-01

Magnetic resonance spectroscopic imaging (MRSI) provides spatially resolved metabolite information that is invaluable for both neuroscience studies and clinical applications. However, lengthy data acquisition times, which are a result of time-consuming phase encoding, represent a major challenge for MRSI. Fast MRSI pulse sequences that use echo-planar readout gradients, such as proton echo-planar spectroscopic imaging (PEPSI), are capable of fast spectral-spatial encoding and thus enable acceleration of image acquisition times. Combining PEPSI with recent advances in parallel MRI utilizing RF coil arrays can further accelerate MRSI data acquisition. Here we investigate the feasibility of ultrafast spectroscopic imaging at high field (3T and 4T) by combining PEPSI with sensitivity-encoded (SENSE) MRI using eight-channel head coil arrays. We show that the acquisition of single-average SENSE-PEPSI data at a short TE (15 ms) can be accelerated to 32 s or less, depending on the field strength, to obtain metabolic images of choline (Cho), creatine (Cre), N-acetyl-aspartate (NAA), and J-coupled metabolites (e.g., glutamate (Glu) and inositol (Ino)) with acceptable spectral quality and localization. The experimentally measured reductions in signal-to-noise ratio (SNR) and Cramer-Rao lower bounds (CRLBs) of metabolite resonances were well explained by both the g-factor and reduced measurement times. Thus, this technology is a promising means of reducing the scan times of 3D acquisitions and time-resolved 2D measurements. Copyright (c) 2007 Wiley-Liss, Inc.

MRI of the temporo-mandibular joint: which sequence is best suited to assess the cortical bone of the mandibular condyle? A cadaveric study using micro-CT as the standard of reference.

PubMed

Karlo, Christoph A; Patcas, Raphael; Kau, Thomas; Watzal, Helmut; Signorelli, Luca; Müller, Lukas; Ullrich, Oliver; Luder, Hans-Ulrich; Kellenberger, Christian J

2012-07-01

To determine the best suited sagittal MRI sequence out of a standard temporo-mandibular joint (TMJ) imaging protocol for the assessment of the cortical bone of the mandibular condyles of cadaveric specimens using micro-CT as the standard of reference. Sixteen TMJs in 8 human cadaveric heads (mean age, 81 years) were examined by MRI. Upon all sagittal sequences, two observers measured the cortical bone thickness (CBT) of the anterior, superior and posterior portions of the mandibular condyles (i.e. objective analysis), and assessed for the presence of cortical bone thinning, erosions or surface irregularities as well as subcortical bone cysts and anterior osteophytes (i.e. subjective analysis). Micro-CT of the condyles was performed to serve as the standard of reference for statistical analysis. Inter-observer agreements for objective (r = 0.83-0.99, P < 0.01) and subjective (κ = 0.67-0.88) analyses were very good. Mean CBT measurements were most accurate, and cortical bone thinning, erosions, surface irregularities and subcortical bone cysts were best depicted on the 3D fast spoiled gradient echo recalled sequence (3D FSPGR). The most reliable MRI sequence to assess the cortical bone of the mandibular condyles on sagittal imaging planes is the 3D FSPGR sequence. MRI may be used to assess the cortical bone of the TMJ. • Depiction of cortical bone is best on 3D FSPGR sequences. • MRI can assess treatment response in patients with TMJ abnormalities.

SU-E-J-223: A BOLD Contrast Imaging Sequence to Evaluate Oxygenation Changes Due to Breath Holding for Breast Radiotherapy: A Pilot Study

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

Adamson, J; Chang, Z; Cai, J

Purpose: To develop a robust MRI sequence to measure BOLD breath hold induced contrast in context of breast radiotherapy. Methods: Two sequences were selected from prior studies as candidates to measure BOLD contrast attributable to breath holding within the breast: (1) T2* based Gradient Echo EPI (TR/TE = 500/41ms, flip angle = 60°), and (2) T2 based Single Shot Fast Spin Echo (SSFSE) (TR/TE = 3000/60ms). We enrolled ten women post-lumpectomy for breast cancer who were undergoing treatment planning for whole breast radiotherapy. Each session utilized a 1.5T GE MRI and 4 channel breast coil with the subject immobilized pronemore » on a custom board. For each sequence, 1–3 planes of the lumpectomy breast were imaged continuously during a background measurement (1min) and intermittent breath holds (20–40s per breath hold, 3–5 holds per sequence). BOLD contrast was quantified as correlation of changes in per-pixel intensity with the breath hold schedule convolved with a hemodynamic response function. Subtle motion was corrected using a deformable registration algorithm. Correlation with breath-holding was considered significant if p<0.001. Results: The percentage of the breast ROI with positive BOLD contrast measured by the two sequences were in agreement with a correlation coefficient of R=0.72 (p=0.02). While both sequences demonstrated areas with strong BOLD response, the response was more systematic throughout the breast for the SSFSE (T2) sequence (% breast with response in the same direction: 51.2%±0.7% for T2* vs. 68.1%±16% for T2). In addition, the T2 sequence was less prone to magnetic susceptibility artifacts, especially in presence of seroma, and provided a more robust image with little distortion or artifacts. Conclusion: A T2 SSFSE sequence shows promise for measuring BOLD contrast in the context of breast radiotherapy utilizing a breath hold technique. Further study in a larger patient cohort is warranted to better refine this novel technique.« less

Neurologic 3D MR Spectroscopic Imaging with Low-Power Adiabatic Pulses and Fast Spiral Acquisition

PubMed Central

Gagoski, Borjan A.; Sorensen, A. Gregory

2012-01-01

Purpose: To improve clinical three-dimensional (3D) MR spectroscopic imaging with more accurate localization and faster acquisition schemes. Materials and Methods: Institutional review board approval and patient informed consent were obtained. Data were acquired with a 3-T MR imager and a 32-channel head coil in phantoms, five healthy volunteers, and five patients with glioblastoma. Excitation was performed with localized adiabatic spin-echo refocusing (LASER) by using adiabatic gradient-offset independent adiabaticity wideband uniform rate and smooth truncation (GOIA-W[16,4]) pulses with 3.5-msec duration, 20-kHz bandwidth, 0.81-kHz amplitude, and 45-msec echo time. Interleaved constant-density spirals simultaneously encoded one frequency and two spatial dimensions. Conventional phase encoding (PE) (1-cm3 voxels) was performed after LASER excitation and was the reference standard. Spectra acquired with spiral encoding at similar and higher spatial resolution and with shorter imaging time were compared with those acquired with PE. Metabolite levels were fitted with software, and Bland-Altman analysis was performed. Results: Clinical 3D MR spectroscopic images were acquired four times faster with spiral protocols than with the elliptical PE protocol at low spatial resolution (1 cm3). Higher-spatial-resolution images (0.39 cm3) were acquired twice as fast with spiral protocols compared with the low-spatial-resolution elliptical PE protocol. A minimum signal-to-noise ratio (SNR) of 5 was obtained with spiral protocols under these conditions and was considered clinically adequate to reliably distinguish metabolites from noise. The apparent SNR loss was not linear with decreasing voxel sizes because of longer local T2* times. Improvement of spectral line width from 4.8 Hz to 3.5 Hz was observed at high spatial resolution. The Bland-Altman agreement between spiral and PE data is characterized by narrow 95% confidence intervals for their differences (0.12, 0.18 of their means). GOIA-W(16,4) pulses minimize chemical-shift displacement error to 2.1%, reduce nonuniformity of excitation to 5%, and eliminate the need for outer volume suppression. Conclusion: The proposed adiabatic spiral 3D MR spectroscopic imaging sequence can be performed in a standard clinical MR environment. Improvements in image quality and imaging time could enable more routine acquisition of spectroscopic data than is possible with current pulse sequences. © RSNA, 2011 PMID:22187628

Comparison of neonatal MRI examinations with and without an MR-compatible incubator: advantages in examination feasibility and clinical decision-making.

PubMed

Rona, Z; Klebermass, K; Cardona, F; Czaba, C D; Brugger, P C; Weninger, M; Pollak, A; Prayer, D

2010-09-01

To assess the utility of an MRI-compatible incubator (INC) by comparing. In a retrospective study, the clinical and radiological aspects of 129 neonatal MRI examinations during a 3 year period were analyzed. Routine protocols including fast spin-echo T2-weighted (w) sequences, axial T1w, Gradient-echo, diffusion sequences, and 3D T1 gradient-echo sequences were performed routinely, angiography and spectroscopy were added in some cases. Diffusion-tensor imaging was done in 50% of the babies examined in the INC and 26% without INC. Sequences, adapted from fetal MR-protocols were done in infants younger than 32 gestational weeks. Benefit from MR-information with respect to further management was evaluated. The number of the examinations increased (30-99), while the mean age (43-38, 8 weeks of gestational age) and weight (3308-2766 g) decreased significantly with the use of the MR-compatible incubator. The mean imaging time (34, 43-30, 29 min) decreased, with a mean of one additionally performed sequence in the INC group. All infants received sedatives according to our anaesthetic protocol preceding imaging, but a repeated dose was never necessary (10% without INC) using the INC. Regarding all cases, MR-based changes in clinical management were initiated in 58%, while in 57% of cases the initial ultrasound diagnosis was changed or further specified. The use of the INC enables the MR access of unstable infants with suspect CNS problems to the management, of whom is improved by MR information to significantly higher percentage, than without INC. Copyright (c) 2010 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.

Improved Contrast-Enhanced Ultrasound Imaging With Multiplane-Wave Imaging.

PubMed

Gong, Ping; Song, Pengfei; Chen, Shigao

2018-02-01

Contrast-enhanced ultrasound (CEUS) imaging has great potential for use in new ultrasound clinical applications such as myocardial perfusion imaging and abdominal lesion characterization. In CEUS imaging, contrast agents (i.e., microbubbles) are used to improve contrast between blood and tissue because of their high nonlinearity under low ultrasound pressure. However, the quality of CEUS imaging sometimes suffers from a low signal-to-noise ratio (SNR) in deeper imaging regions when a low mechanical index (MI) is used to avoid microbubble disruption, especially for imaging at off-resonance transmit frequencies. In this paper, we propose a new strategy of combining CEUS sequences with the recently proposed multiplane-wave (MW) compounding method to improve the SNR of CEUS in deeper imaging regions without increasing MI or sacrificing frame rate. The MW-CEUS method emits multiple Hadamard-coded CEUS pulses in each transmission event (i.e., pulse-echo event). The received echo signals first undergo fundamental bandpass filtering (i.e., the filter is centered on the transmit frequency) to eliminate the microbubble's second-harmonic signals because they cannot be encoded by pulse inversion. The filtered signals are then Hadamard decoded and realigned in fast time to recover the signals as they would have been obtained using classic CEUS pulses, followed by designed recombination to cancel the linear tissue responses. The MW-CEUS method significantly improved contrast-to-tissue ratio and SNR of CEUS imaging by transmitting longer coded pulses. The image resolution was also preserved. The microbubble disruption ratio and motion artifacts in MW-CEUS were similar to those of classic CEUS imaging. In addition, the MW-CEUS sequence can be adapted to other transmission coding formats. These properties of MW-CEUS can potentially facilitate CEUS imaging for many clinical applications, especially assessing deep abdominal organs or the heart.

High-resolution proton density weighted three-dimensional fast spin echo (3D-FSE) of the knee with IDEAL at 1.5 Tesla: comparison with 3D-FSE and 2D-FSE--initial experience.

PubMed

McMahon, Colm J; Madhuranthakam, Ananth J; Wu, Jim S; Yablon, Corrie M; Wei, Jesse L; Rofsky, Neil M; Hochman, Mary G

2012-02-01

To assess the feasibility of combining three-dimensional fast spin echo (3D-FSE) and Iterative-decomposition-of water-and-fat-with-echo asymmetry-and-least-squares-estimation (IDEAL) at 1.5 Tesla (T), generating a high-resolution 3D isotropic proton density-weighted image set with and without "fat-suppression" (FS) in a single acquisition, and to compare with 2D-FSE and 3D-FSE (without IDEAL). Ten asymptomatic volunteers prospectively underwent sagittal 3D-FSE-IDEAL, 3D-FSE, and 2D-FSE sequences at 1.5T (slice thickness [ST]: 0.8 mm, 0.8 mm, and 3.5 mm, respectively). 3D-FSE and 2D-FSE were repeated with frequency-selective FS. Fluid, cartilage, and muscle signal-to-noise ratio (SNR) and fluid-cartilage contrast-to-noise ratio (CNR) were compared among sequences. Three blinded reviewers independently scored quality of menisci/cartilage depiction for all sequences. "Fat-suppression" was qualitatively scored and compared among sequences. 3D-FSE-IDEAL fluid-cartilage CNR was higher than in 2D-FSE (P < 0.05), not different from 3D-FSE (P = 0.31). There was no significant difference in fluid SNR among sequences. 2D-FSE cartilage SNR was higher than in 3D FSE-IDEAL (P < 0.05), not different to 3D-FSE (P = 0.059). 2D-FSE muscle SNR was higher than in 3D-FSE-IDEAL (P < 0.05) and 3D-FSE (P < 0.05). Good or excellent depiction of menisci/cartilage was achieved using 3D-FSE-IDEAL in the acquired sagittal and reformatted planes. Excellent, homogeneous "fat-suppression" was achieved using 3D-FSE-IDEAL, superior to FS-3D-FSE and FS-2D-FSE (P < 0.05). 3D FSE-IDEAL is a feasible approach to acquire multiplanar images of diagnostic quality, both with and without homogeneous "fat-suppression" from a single acquisition. Copyright © 2011 Wiley Periodicals, Inc.

Ocular volumetry using fast high-resolution MRI during visual fixation.

PubMed

Tanitame, K; Sone, T; Miyoshi, T; Tanitame, N; Otani, K; Akiyama, Y; Takasu, M; Date, S; Kiuchi, Y; Awai, K

2013-04-01

Volumetry may be useful for evaluating treatment response and prognosis of intraocular lesions. Phantom, volunteer, and patient studies were performed to determine whether ocular MR volumetry is reproducible. Half-Fourier single-shot RARE and FSPGR sequences at 1.5T with a 76-mm-diameter surface coil were optimized to obtain still ocular images. Volumetry accuracies of each sequence were compared with simulated subretinal phantom volumes. Ocular volumetry was performed in 15 volunteers twice in 1 week by using contiguous axial images of the globes while the subjects stared at a target, and images were acquired in 2 seconds before the subjects were instructed to blink, with this process repeated as necessary. Imaging, intraobserver, and interobserver reproducibility for volumes of the whole eyeball and anterior chamber were assessed. Ocular volumetry was also performed in 6 patients with intraocular tumors before and after treatment. The phantom study demonstrated that measurement error rates with RARE were significantly lower than with FSPGR (P<.01). The volunteer study demonstrated excellent imaging and intraobserver reproducibility of RARE volumetry for whole eyeballs and anterior chambers (P<.01). Although no interobserver differences were observed in anterior chamber volume measurement (P=.33), there was a significant difference between the 2 observers in eyeball volume measurement (P<.01). Follow-up volumetric data were useful for treatment decisions in all patients. Ocular volumetry from contiguous ultrafast RARE images obtained during visual fixation is feasible in volunteer and patient studies and is superior to FSPGR images.

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.

Quantitative analysis of cardiovascular MR images.

PubMed

van der Geest, R J; de Roos, A; van der Wall, E E; Reiber, J H

1997-06-01

The diagnosis of cardiovascular disease requires the precise assessment of both morphology and function. Nearly all aspects of cardiovascular function and flow can be quantified nowadays with fast magnetic resonance (MR) imaging techniques. Conventional and breath-hold cine MR imaging allow the precise and highly reproducible assessment of global and regional left ventricular function. During the same examination, velocity encoded cine (VEC) MR imaging provides measurements of blood flow in the heart and great vessels. Quantitative image analysis often still relies on manual tracing of contours in the images. Reliable automated or semi-automated image analysis software would be very helpful to overcome the limitations associated with the manual and tedious processing of the images. Recent progress in MR imaging of the coronary arteries and myocardial perfusion imaging with contrast media, along with the further development of faster imaging sequences, suggest that MR imaging could evolve into a single technique ('one stop shop') for the evaluation of many aspects of heart disease. As a result, it is very likely that the need for automated image segmentation and analysis software algorithms will further increase. In this paper the developments directed towards the automated image analysis and semi-automated contour detection for cardiovascular MR imaging are presented.

Fast imaging employing steady-state acquisition (FIESTA) MRI to investigate cerebrospinal fluid (CSF) within dural reflections of posterior fossa cranial nerves

PubMed Central

Scoffings, Daniel; Ajithkumar, Thankamma; Williams, Michael V; Jefferies, Sarah J

2016-01-01

Objective: There is no consensus approach to covering skull base meningeal reflections—and cerebrospinal fluid (CSF) therein—of the posterior fossa cranial nerves (CNs VII–XII) when planning radiotherapy (RT) for medulloblastoma and ependymoma. We sought to determine whether MRI and specifically fast imaging employing steady-state acquisition (FIESTA) sequences can answer this anatomical question and guide RT planning. Methods: 96 posterior fossa FIESTA sequences were reviewed. Following exclusions, measurements were made on the following scans for each foramen respectively (left, right); internal acoustic meatus (IAM) (86, 84), jugular foramen (JF) (83, 85) and hypoglossal canal (HC) (42, 45). A protocol describes measurement procedure. Two observers measured distances for five cases and agreement was assessed. One observer measured all the remaining cases. Results: IAM and JF measurement interobserver variability was compared. Mean measurement difference between observers was −0.275 mm (standard deviation 0.557). IAM and JF measurements were normally distributed. Mean IAM distance was 12.2 mm [95% confidence interval (CI) 8.8–15.6]; JF was 7.3 mm (95% CI 4.0–10.6). The HC was difficult to visualize on many images and data followed a bimodal distribution. Conclusion: Dural reflections of posterior fossa CNs are well demonstrated by FIESTA MRI. Measuring CSF extension into these structures is feasible and robust; mean CSF extension into IAM and JF was measured. We plan further work to assess coverage of these structures with photon and proton RT plans. Advances in knowledge: We have described CSF extension beyond the internal table of the skull into the IAM, JF and HC. Oncologists planning RT for patients with medulloblastoma and ependymoma may use these data to guide contouring. PMID:27636022

Fast imaging employing steady-state acquisition (FIESTA) MRI to investigate cerebrospinal fluid (CSF) within dural reflections of posterior fossa cranial nerves.

PubMed

Noble, David J; Scoffings, Daniel; Ajithkumar, Thankamma; Williams, Michael V; Jefferies, Sarah J

2016-11-01

There is no consensus approach to covering skull base meningeal reflections-and cerebrospinal fluid (CSF) therein-of the posterior fossa cranial nerves (CNs VII-XII) when planning radiotherapy (RT) for medulloblastoma and ependymoma. We sought to determine whether MRI and specifically fast imaging employing steady-state acquisition (FIESTA) sequences can answer this anatomical question and guide RT planning. 96 posterior fossa FIESTA sequences were reviewed. Following exclusions, measurements were made on the following scans for each foramen respectively (left, right); internal acoustic meatus (IAM) (86, 84), jugular foramen (JF) (83, 85) and hypoglossal canal (HC) (42, 45). A protocol describes measurement procedure. Two observers measured distances for five cases and agreement was assessed. One observer measured all the remaining cases. IAM and JF measurement interobserver variability was compared. Mean measurement difference between observers was -0.275 mm (standard deviation 0.557). IAM and JF measurements were normally distributed. Mean IAM distance was 12.2 mm [95% confidence interval (CI) 8.8-15.6]; JF was 7.3 mm (95% CI 4.0-10.6). The HC was difficult to visualize on many images and data followed a bimodal distribution. Dural reflections of posterior fossa CNs are well demonstrated by FIESTA MRI. Measuring CSF extension into these structures is feasible and robust; mean CSF extension into IAM and JF was measured. We plan further work to assess coverage of these structures with photon and proton RT plans. Advances in knowledge: We have described CSF extension beyond the internal table of the skull into the IAM, JF and HC. Oncologists planning RT for patients with medulloblastoma and ependymoma may use these data to guide contouring.

SU-E-J-214: MR Protocol Development to Visualize Sirius MRI Markers in Prostate Brachytherapy Patients for MR-Based Post-Implant Dosimetry

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

Lim, T; Wang, J; Frank, S

Purpose: The current CT-based post-implant dosimetry allows precise seed localization but limited anatomical delineation. Switching to MR-based post-implant dosimetry is confounded by imprecise seed localization. One approach is to place positive-contrast markers (Sirius) adjacent to the negative-contrast seeds. This patient study aims to assess the utility of a 3D fast spoiled gradient-recalled echo (FSPGR) sequence to visualize Sirius markers for post-implant dosimetry. Methods: MRI images were acquired in prostate implant patients (n=10) on Day 0 (day-of-implant) and Day 30. The post-implant MR protocol consisted of 3D T2-weighted fast-spin-echo (FSE), T2-weighted 2D-FSE (axial) and T1-weighted 2D-FSE (axial/sagittal/coronal). We incorporated a 3D-FSPGRmore » sequence into the post-implant MR protocol to visualize the Sirius markers. Patients were scanned with different number-of-excitations (6, 8, 10), field-of-view (10cm, 14cm, 18cm), slice thickness (1mm, 0.8mm), flip angle (14 degrees, 20 degrees), bandwidth (122.070 Hz/pixel, 325.508 Hz/pixel, 390.625 Hz/pixel), phase encoding steps (160, 192, 224, 256), frequency-encoding direction (right/left, anterior/posterior), echo-time type (minimum-full, out-of-phase), field strength (1.5T, 3T), contrast (with, without), scanner vendor (Siemens, GE), coil (endorectal-coil only, endorectal-and-torso-coil, torsocoil only), endorectal-coil filling (30cc, 50cc) and endorectal-coil filling type (air, perfluorocarbon [PFC]). For post-implant dosimetric evaluation with greater anatomical detail, 3D-FSE images were fused with 3D-FSPGR images. For comparison with CT-based post-implant dosimetry, CT images were fused with 3D-FSPGR images. Results: The 3D-FSPGR sequence facilitated visualization of markers in patients. Marker visualization helped distinguish signal voids as seeds versus needle tracks for more definitive MR-based post-implant dosimetry. On the CT-MR fused images, the distance between the seed on CT to MR images was 3.2±1.6mm in patients with no endorectal coil, 2.3±0.8mm in patients with 30cc-PFC-filled endorectal-coil and 5.0±1.8mm in patients with 50cc-PFC-filled endorectal-coil. Conclusion: An MR protocol to visualize positive-contrast Sirius markers to assist in the identification of negative-contrast seeds was demonstrated. S Frank is a co-founder of C4 Imaging LLC, the manufacturer of the MRI markers.« less

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.

Fast registration and reconstruction of aliased low-resolution frames by use of a modified maximum-likelihood approach.

PubMed

Alam, M S; Bognar, J G; Cain, S; Yasuda, B J

1998-03-10

During the process of microscanning a controlled vibrating mirror typically is used to produce subpixel shifts in a sequence of forward-looking infrared (FLIR) images. If the FLIR is mounted on a moving platform, such as an aircraft, uncontrolled random vibrations associated with the platform can be used to generate the shifts. Iterative techniques such as the expectation-maximization (EM) approach by means of the maximum-likelihood algorithm can be used to generate high-resolution images from multiple randomly shifted aliased frames. In the maximum-likelihood approach the data are considered to be Poisson random variables and an EM algorithm is developed that iteratively estimates an unaliased image that is compensated for known imager-system blur while it simultaneously estimates the translational shifts. Although this algorithm yields high-resolution images from a sequence of randomly shifted frames, it requires significant computation time and cannot be implemented for real-time applications that use the currently available high-performance processors. The new image shifts are iteratively calculated by evaluation of a cost function that compares the shifted and interlaced data frames with the corresponding values in the algorithm's latest estimate of the high-resolution image. We present a registration algorithm that estimates the shifts in one step. The shift parameters provided by the new algorithm are accurate enough to eliminate the need for iterative recalculation of translational shifts. Using this shift information, we apply a simplified version of the EM algorithm to estimate a high-resolution image from a given sequence of video frames. The proposed modified EM algorithm has been found to reduce significantly the computational burden when compared with the original EM algorithm, thus making it more attractive for practical implementation. Both simulation and experimental results are presented to verify the effectiveness of the proposed technique.

Efficacy of periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) for shoulder magnetic resonance (MR) imaging.

PubMed

Nagatomo, Kazuya; Yabuuchi, Hidetake; Yamasaki, Yuzo; Narita, Hiroshi; Kumazawa, Seiji; Kojima, Tsukasa; Sakai, Noriyuki; Masaki, Masahumi; Kimura, Hiroshi

2016-10-01

To elucidate the utility of PROPELLER for motion artefact reduction on shoulder MRI and to examine the influence of streak artefacts on diagnosis of clinical images. 15 healthy volunteers and 48 patients underwent shoulder MRI with/without PROPELLER (coronal oblique proton density-fast spin echo [PD-FSE], sagittal oblique T2-FSE). In a volunteer study, all sequences were performed in both static and exercise-loaded conditions. Two radiologists graded artefacts and delineation of various anatomical structures in the volunteer study and motion and streak artefacts in the clinical study. Mean scores were compared between sequences with/without PROPELLER. In the clinical study, mean scores of motion artefacts were compared with mean scores of streak artefacts. Wilcoxon signed-rank test was used for all comparisons. In both studies, PROPELLER significantly reduced motion artefacts (P<0.05). In the volunteer study, it significantly improved delineations in sagittal oblique images in the exercise-loaded condition (P<0.05). In the clinical study, streak artefacts appeared dominantly on images with PROPELLER (P<0.05), but influenced diagnosis to a lesser extent than motion artefacts. PROPELLER can reduce motion artefacts in shoulder MRI. While it does cause streak artefacts, it affects diagnosis to a lesser extent. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

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.

Adaptive multiple super fast simulated annealing for stochastic microstructure reconstruction

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

Ryu, Seun; Lin, Guang; Sun, Xin

2013-01-01

Fast image reconstruction from statistical information is critical in image fusion from multimodality chemical imaging instrumentation to create high resolution image with large domain. Stochastic methods have been used widely in image reconstruction from two point correlation function. The main challenge is to increase the efficiency of reconstruction. A novel simulated annealing method is proposed for fast solution of image reconstruction. Combining the advantage of very fast cooling schedules, dynamic adaption and parallelization, the new simulation annealing algorithm increases the efficiencies by several orders of magnitude, making the large domain image fusion feasible.

Fast interactive exploration of 4D MRI flow data

NASA Astrophysics Data System (ADS)

Hennemuth, A.; Friman, O.; Schumann, C.; Bock, J.; Drexl, J.; Huellebrand, M.; Markl, M.; Peitgen, H.-O.

2011-03-01

1- or 2-directional MRI blood flow mapping sequences are an integral part of standard MR protocols for diagnosis and therapy control in heart diseases. Recent progress in rapid MRI has made it possible to acquire volumetric, 3-directional cine images in reasonable scan time. In addition to flow and velocity measurements relative to arbitrarily oriented image planes, the analysis of 3-dimensional trajectories enables the visualization of flow patterns, local features of flow trajectories or possible paths into specific regions. The anatomical and functional information allows for advanced hemodynamic analysis in different application areas like stroke risk assessment, congenital and acquired heart disease, aneurysms or abdominal collaterals and cranial blood flow. The complexity of the 4D MRI flow datasets and the flow related image analysis tasks makes the development of fast comprehensive data exploration software for advanced flow analysis a challenging task. Most existing tools address only individual aspects of the analysis pipeline such as pre-processing, quantification or visualization, or are difficult to use for clinicians. The goal of the presented work is to provide a software solution that supports the whole image analysis pipeline and enables data exploration with fast intuitive interaction and visualization methods. The implemented methods facilitate the segmentation and inspection of different vascular systems. Arbitrary 2- or 3-dimensional regions for quantitative analysis and particle tracing can be defined interactively. Synchronized views of animated 3D path lines, 2D velocity or flow overlays and flow curves offer a detailed insight into local hemodynamics. The application of the analysis pipeline is shown for 6 cases from clinical practice, illustrating the usefulness for different clinical questions. Initial user tests show that the software is intuitive to learn and even inexperienced users achieve good results within reasonable processing times.

High frequency oscillations are associated with cognitive processing in human recognition memory.

PubMed

Kucewicz, Michal T; Cimbalnik, Jan; Matsumoto, Joseph Y; Brinkmann, Benjamin H; Bower, Mark R; Vasoli, Vincent; Sulc, Vlastimil; Meyer, Fred; Marsh, W R; Stead, S M; Worrell, Gregory A

2014-08-01

High frequency oscillations are associated with normal brain function, but also increasingly recognized as potential biomarkers of the epileptogenic brain. Their role in human cognition has been predominantly studied in classical gamma frequencies (30-100 Hz), which reflect neuronal network coordination involved in attention, learning and memory. Invasive brain recordings in animals and humans demonstrate that physiological oscillations extend beyond the gamma frequency range, but their function in human cognitive processing has not been fully elucidated. Here we investigate high frequency oscillations spanning the high gamma (50-125 Hz), ripple (125-250 Hz) and fast ripple (250-500 Hz) frequency bands using intracranial recordings from 12 patients (five males and seven females, age 21-63 years) during memory encoding and recall of a series of affectively charged images. Presentation of the images induced high frequency oscillations in all three studied bands within the primary visual, limbic and higher order cortical regions in a sequence consistent with the visual processing stream. These induced oscillations were detected on individual electrodes localized in the amygdala, hippocampus and specific neocortical areas, revealing discrete oscillations of characteristic frequency, duration and latency from image presentation. Memory encoding and recall significantly modulated the number of induced high gamma, ripple and fast ripple detections in the studied structures, which was greater in the primary sensory areas during the encoding (Wilcoxon rank sum test, P = 0.002) and in the higher-order cortical association areas during the recall (Wilcoxon rank sum test, P = 0.001) of memorized images. Furthermore, the induced high gamma, ripple and fast ripple responses discriminated the encoded and the affectively charged images. In summary, our results show that high frequency oscillations, spanning a wide range of frequencies, are associated with memory processing and generated along distributed cortical and limbic brain regions. These findings support an important role for fast network synchronization in human cognition and extend our understanding of normal physiological brain activity during memory processing. © The Author (2014). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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.

MR-compatibility assessment of MADPET4: a study of interferences between an SiPM-based PET insert and a 7 T MRI system

NASA Astrophysics Data System (ADS)

Omidvari, Negar; Topping, Geoffrey; Cabello, Jorge; Paul, Stephan; Schwaiger, Markus; Ziegler, Sibylle I.

2018-05-01

Compromises in the design of a positron emission tomography (PET) insert for a magnetic resonance imaging (MRI) system should minimize the deterioration of image quality in both modalities, particularly when simultaneous demanding acquisitions are performed. In this work, the advantages of using individually read-out crystals with high-gain silicon photomultipliers (SiPMs) were studied with a small animal PET insert for a 7 T MRI system, in which the SiPM charge was transferred to outside the MRI scanner using coaxial cables. The interferences between the two systems were studied with three radio-frequency (RF) coil configurations. The effects of PET on the static magnetic field, flip angle distribution, RF noise, and image quality of various MRI sequences (gradient echo, spin echo, and echo planar imaging (EPI) at 1H frequency, and chemical shift imaging at 13C frequency) were investigated. The effects of fast-switching gradient fields and RF pulses on PET count rate were studied, while the PET insert and the readout electronics were not shielded. Operating the insert inside a 1H volume coil, used for RF transmission and reception, limited the MRI to T1-weighted imaging, due to coil detuning and RF attenuation, and resulted in significant PET count loss. Using a surface receive coil allowed all tested MR sequences to be used with the insert, with 45–59% signal-to-noise ratio (SNR) degradation, compared to without PET. With a 1H/13C volume coil inside the insert and shielded by a copper tube, the SNR degradation was limited to 23–30% with all tested sequences. The insert did not introduce any discernible distortions into images of two tested EPI sequences. Use of truncated sinc shaped RF excitation pulses and gradient field switching had negligible effects on PET count rate. However, PET count rate was substantially affected by high-power RF block pulses and temperature variations due to high gradient duty cycles.

A peripheral component interconnect express-based scalable and highly integrated pulsed spectrometer for solution state dynamic nuclear polarization.

PubMed

He, Yugui; Feng, Jiwen; Zhang, Zhi; Wang, Chao; Wang, Dong; Chen, Fang; Liu, Maili; Liu, Chaoyang

2015-08-01

High sensitivity, high data rates, fast pulses, and accurate synchronization all represent challenges for modern nuclear magnetic resonance spectrometers, which make any expansion or adaptation of these devices to new techniques and experiments difficult. Here, we present a Peripheral Component Interconnect Express (PCIe)-based highly integrated distributed digital architecture pulsed spectrometer that is implemented with electron and nucleus double resonances and is scalable specifically for broad dynamic nuclear polarization (DNP) enhancement applications, including DNP-magnetic resonance spectroscopy/imaging (DNP-MRS/MRI). The distributed modularized architecture can implement more transceiver channels flexibly to meet a variety of MRS/MRI instrumentation needs. The proposed PCIe bus with high data rates can significantly improve data transmission efficiency and communication reliability and allow precise control of pulse sequences. An external high speed double data rate memory chip is used to store acquired data and pulse sequence elements, which greatly accelerates the execution of the pulse sequence, reduces the TR (time of repetition) interval, and improves the accuracy of TR in imaging sequences. Using clock phase-shift technology, we can produce digital pulses accurately with high timing resolution of 1 ns and narrow widths of 4 ns to control the microwave pulses required by pulsed DNP and ensure overall system synchronization. The proposed spectrometer is proved to be both feasible and reliable by observation of a maximum signal enhancement factor of approximately -170 for (1)H, and a high quality water image was successfully obtained by DNP-enhanced spin-echo (1)H MRI at 0.35 T.

A peripheral component interconnect express-based scalable and highly integrated pulsed spectrometer for solution state dynamic nuclear polarization

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

He, Yugui; Liu, Chaoyang, E-mail: chyliu@wipm.ac.cn; State Key Laboratory of Magnet Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071

2015-08-15

High sensitivity, high data rates, fast pulses, and accurate synchronization all represent challenges for modern nuclear magnetic resonance spectrometers, which make any expansion or adaptation of these devices to new techniques and experiments difficult. Here, we present a Peripheral Component Interconnect Express (PCIe)-based highly integrated distributed digital architecture pulsed spectrometer that is implemented with electron and nucleus double resonances and is scalable specifically for broad dynamic nuclear polarization (DNP) enhancement applications, including DNP-magnetic resonance spectroscopy/imaging (DNP-MRS/MRI). The distributed modularized architecture can implement more transceiver channels flexibly to meet a variety of MRS/MRI instrumentation needs. The proposed PCIe bus with highmore » data rates can significantly improve data transmission efficiency and communication reliability and allow precise control of pulse sequences. An external high speed double data rate memory chip is used to store acquired data and pulse sequence elements, which greatly accelerates the execution of the pulse sequence, reduces the TR (time of repetition) interval, and improves the accuracy of TR in imaging sequences. Using clock phase-shift technology, we can produce digital pulses accurately with high timing resolution of 1 ns and narrow widths of 4 ns to control the microwave pulses required by pulsed DNP and ensure overall system synchronization. The proposed spectrometer is proved to be both feasible and reliable by observation of a maximum signal enhancement factor of approximately −170 for {sup 1}H, and a high quality water image was successfully obtained by DNP-enhanced spin-echo {sup 1}H MRI at 0.35 T.« less

Fast neutron imaging device and method

DOEpatents

Popov, Vladimir; Degtiarenko, Pavel; Musatov, Igor V.

2014-02-11

A fast neutron imaging apparatus and method of constructing fast neutron radiography images, the apparatus including a neutron source and a detector that provides event-by-event acquisition of position and energy deposition, and optionally timing and pulse shape for each individual neutron event detected by the detector. The method for constructing fast neutron radiography images utilizes the apparatus of the invention.

Optimization of magnetic flux density for fast MREIT conductivity imaging using multi-echo interleaved partial fourier acquisitions.

PubMed

Chauhan, Munish; Jeong, Woo Chul; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

2013-08-27

Magnetic resonance electrical impedance tomography (MREIT) has been introduced as a non-invasive method for visualizing the internal conductivity and/or current density of an electrically conductive object by externally injected currents. The injected current through a pair of surface electrodes induces a magnetic flux density distribution inside the imaging object, which results in additional magnetic flux density. To measure the magnetic flux density signal in MREIT, the phase difference approach in an interleaved encoding scheme cancels out the systematic artifacts accumulated in phase signals and also reduces the random noise effect by doubling the measured magnetic flux density signal. For practical applications of in vivo MREIT, it is essential to reduce the scan duration maintaining spatial-resolution and sufficient contrast. In this paper, we optimize the magnetic flux density by using a fast gradient multi-echo MR pulse sequence. To recover the one component of magnetic flux density Bz, we use a coupled partial Fourier acquisitions in the interleaved sense. To prove the proposed algorithm, we performed numerical simulations using a two-dimensional finite-element model. For a real experiment, we designed a phantom filled with a calibrated saline solution and located a rubber balloon inside the phantom. The rubber balloon was inflated by injecting the same saline solution during the MREIT imaging. We used the multi-echo fast low angle shot (FLASH) MR pulse sequence for MRI scan, which allows the reduction of measuring time without a substantial loss in image quality. Under the assumption of a priori phase artifact map from a reference scan, we rigorously investigated the convergence ratio of the proposed method, which was closely related with the number of measured phase encode set and the frequency range of the background field inhomogeneity. In the phantom experiment with a partial Fourier acquisition, the total scan time was less than 6 seconds to measure the magnetic flux density Bz data with 128×128 spacial matrix size, where it required 10.24 seconds to fill the complete k-space region. Numerical simulation and experimental results demonstrated that the proposed method reduces the scanning time and provides the recovered Bz data comparable to what we obtained by measuring complete k-space data.

New Techniques for High-Contrast Imaging with ADI: The ACORNS-ADI SEEDS Data Reduction Pipeline

NASA Technical Reports Server (NTRS)

Brandt, Timothy D.; McElwain, Michael W.; Turner, Edwin L.; Abe, L.; Brandner, W.; Carson, J.; Egner, S.; Feldt, M.; Golota, T.; Grady, C. A.;

Metal-induced streak artifact reduction using iterative reconstruction algorithms in x-ray computed tomography image of the dentoalveolar region.

PubMed

Dong, Jian; Hayakawa, Yoshihiko; Kannenberg, Sven; Kober, Cornelia

2013-02-01

The objective of this study was to reduce metal-induced streak artifact on oral and maxillofacial x-ray computed tomography (CT) images by developing the fast statistical image reconstruction system using iterative reconstruction algorithms. Adjacent CT images often depict similar anatomical structures in thin slices. So, first, images were reconstructed using the same projection data of an artifact-free image. Second, images were processed by the successive iterative restoration method where projection data were generated from reconstructed image in sequence. Besides the maximum likelihood-expectation maximization algorithm, the ordered subset-expectation maximization algorithm (OS-EM) was examined. Also, small region of interest (ROI) setting and reverse processing were applied for improving performance. Both algorithms reduced artifacts instead of slightly decreasing gray levels. The OS-EM and small ROI reduced the processing duration without apparent detriments. Sequential and reverse processing did not show apparent effects. Two alternatives in iterative reconstruction methods were effective for artifact reduction. The OS-EM algorithm and small ROI setting improved the performance. Copyright © 2012 Elsevier Inc. All rights reserved.

Age-related cerebral white matter changes and pulse-wave encephalopathy: observations with three-dimensional MRI.

PubMed

Henry Feugeas, Marie Cécile; De Marco, Giovanni; Peretti, Ilana Idy; Godon-Hardy, Sylvie; Fredy, Daniel; Claeys, Elisabeth Schouman

2005-11-01

Our purpose was to investigate leukoaraïosis (LA) using three-dimensional MR imaging combined with advanced image-processing technology to attempt to group signal abnormalities according to their etiology. Coronal T2-weighted fast fluid-attenuated inversion-recovery (FLAIR) sequences and three-dimensional T1-weighted fast spoiled gradient recalled echo sequences were used to examine cerebral white matter changes in 75 elderly people with memory complaint but no dementia. They were otherwise healthy, community-dwelling subjects. Three subtypes of LA were defined on the basis of their shape, geography and extent: the so-called subependymal/subpial LA, perivascular LA and "bands" along long white matter tracts. Subependymal changes were directly contiguous with ventricular spaces. They showed features of "water hammer" lesions with ventricular systematisation and a more frequent location around the frontal horns than around the bodies (P=.0008). The use of cerebrospinal fluid (CSF) contiguity criterion allowed a classification of splenial changes in the subpial group. Conversely, posterior periventricular lesions in the centrum ovale as well as irregular and extensive periventricular lesions were not directly contiguous with CSF spaces. The so-called perivascular changes showed features of small-vessel-associated disease; they surrounded linear CSF-like signals that followed the direction of perforating vessels. Distribution of these perivascular changes appeared heterogeneous (P ranging from .04 to 5.10(-16)). These findings suggest that subependymal/subpial LA and subcortical LA may be separate manifestations of a single underlying pulse-wave encephalopathy.

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.

Imaging and histological features of central subchondral osteophytes in racehorses with metacarpophalangeal joint osteoarthritis.

PubMed

Olive, J; D'Anjou, M A; Girard, C; Laverty, S; Theoret, C L

2009-12-01

Marginal osteophytes represent a well known component of osteoarthritis in man and animals. Conversely, central subchondral osteophytes (COs), which are commonly present in human knees with osteoarthritis, have not been reported in horses. To describe and compare computed radiography (CR), single-slice computed tomography (CT), 1.5 Tesla magnetic resonance imaging (MRI), and histological features of COs in equine metacarpophalangeal joints with macroscopic evidence of naturally-occurring osteoarthritis. MRI sequences (sagittal spoiled gradient recalled echo [SPGR] with fat saturation, sagittal T2-weighted fast spin echo with fat saturation [T2-FS], dorsal and transverse T1-weighted gradient-recalled echo [GRE], and sagittal T2*-weighted gradient echo with fast imaging employing steady state acquisition [FIESTA]), as well as transverse and reformatted sagittal CTI and 4 computed radiographic (CR) views of 20 paired metacarpophalangeal joints were acquired ex vivo. Following macroscopic evaluation, samples were harvested in predetermined sites of the metacarpal condyle for subsequent histology. The prevalence and detection level of COs was determined for each imaging modality. Abnormalities consistent with COs were clearly depicted on MRI, using the SPGR sequence, in 7/20 (35%) joints. They were identified as a focal hypointense protuberance from the subchondral plate into the cartilage, at the palmarodistal aspect (n=7) and/or at the very dorsal aspect (n=2) of the metacarpal condyle. COs were visible but less obvious in 5 of the 7 joints using FIESTA and reformatted sagittal CT, and were not identifiable on T2-FS, T1-GRE or CR. Microscopically, they consisted of dense bone protruding into the calcified cartilage and disrupting the tidemarks, and they were consistently associated with overlying cartilage defects. Subchondral osteophytes are a feature of osteoarthritis of equine metacarpophalangeal joints and they may be diagnosed using 1.5 Tesla MRI and CT. Central subchondral osteophytes on MRI represent indirect evidence of cartilage damage in horses.

FAST (Four chamber view And Swing Technique) Echo: a Novel and Simple Algorithm to Visualize Standard Fetal Echocardiographic Planes

PubMed Central

Yeo, Lami; Romero, Roberto; Jodicke, Cristiano; Oggè, Giovanna; Lee, Wesley; Kusanovic, Juan Pedro; Vaisbuch, Edi; Hassan, Sonia S.

2010-01-01

Objective To describe a novel and simple algorithm (FAST Echo: Four chamber view And Swing Technique) to visualize standard diagnostic planes of fetal echocardiography from dataset volumes obtained with spatiotemporal image correlation (STIC) and applying a new display technology (OmniView). Methods We developed an algorithm to image standard fetal echocardiographic planes by drawing four dissecting lines through the longitudinal view of the ductal arch contained in a STIC volume dataset. Three of the lines are locked to provide simultaneous visualization of targeted planes, and the fourth line (unlocked) “swings” through the ductal arch image (“swing technique”), providing an infinite number of cardiac planes in sequence. Each line generated the following plane(s): 1) Line 1: three-vessels and trachea view; 2) Line 2: five-chamber view and long axis view of the aorta (obtained by rotation of the five-chamber view on the y-axis); 3) Line 3: four-chamber view; and 4) “Swing” line: three-vessels and trachea view, five-chamber view and/or long axis view of the aorta, four-chamber view, and stomach. The algorithm was then tested in 50 normal hearts (15.3 – 40 weeks of gestation) and visualization rates for cardiac diagnostic planes were calculated. To determine if the algorithm could identify planes that departed from the normal images, we tested the algorithm in 5 cases with proven congenital heart defects. Results In normal cases, the FAST Echo algorithm (3 locked lines and rotation of the five-chamber view on the y-axis) was able to generate the intended planes (longitudinal view of the ductal arch, pulmonary artery, three-vessels and trachea view, five-chamber view, long axis view of the aorta, four-chamber view): 1) individually in 100% of cases [except for the three-vessel and trachea view, which was seen in 98% (49/50)]; and 2) simultaneously in 98% (49/50). The “swing technique” was able to generate the three-vessels and trachea view, five-chamber view and/or long axis view of the aorta, four-chamber view, and stomach in 100% of normal cases. In the abnormal cases, the FAST Echo algorithm demonstrated the cardiac defects and displayed views that deviated from what was expected from the examination of normal hearts. The “swing technique” was useful in demonstrating the specific diagnosis due to visualization of an infinite number of cardiac planes in sequence. Conclusions This novel and simple algorithm can be used to visualize standard fetal echocardiographic planes in normal fetal hearts. The FAST Echo algorithm may simplify examination of the fetal heart and could reduce operator dependency. Using this algorithm, the inability to obtain expected views or the appearance of abnormal views in the generated planes should raise the index of suspicion for congenital heart disease. PMID:20878671

Four-chamber view and 'swing technique' (FAST) echo: a novel and simple algorithm to visualize standard fetal echocardiographic planes.

PubMed

Yeo, L; Romero, R; Jodicke, C; Oggè, G; Lee, W; Kusanovic, J P; Vaisbuch, E; Hassan, S

2011-04-01

To describe a novel and simple algorithm (four-chamber view and 'swing technique' (FAST) echo) for visualization of standard diagnostic planes of fetal echocardiography from dataset volumes obtained with spatiotemporal image correlation (STIC) and applying a new display technology (OmniView). We developed an algorithm to image standard fetal echocardiographic planes by drawing four dissecting lines through the longitudinal view of the ductal arch contained in a STIC volume dataset. Three of the lines are locked to provide simultaneous visualization of targeted planes, and the fourth line (unlocked) 'swings' through the ductal arch image (swing technique), providing an infinite number of cardiac planes in sequence. Each line generates the following plane(s): (a) Line 1: three-vessels and trachea view; (b) Line 2: five-chamber view and long-axis view of the aorta (obtained by rotation of the five-chamber view on the y-axis); (c) Line 3: four-chamber view; and (d) 'swing line': three-vessels and trachea view, five-chamber view and/or long-axis view of the aorta, four-chamber view and stomach. The algorithm was then tested in 50 normal hearts in fetuses at 15.3-40 weeks' gestation and visualization rates for cardiac diagnostic planes were calculated. To determine whether the algorithm could identify planes that departed from the normal images, we tested the algorithm in five cases with proven congenital heart defects. In normal cases, the FAST echo algorithm (three locked lines and rotation of the five-chamber view on the y-axis) was able to generate the intended planes (longitudinal view of the ductal arch, pulmonary artery, three-vessels and trachea view, five-chamber view, long-axis view of the aorta, four-chamber view) individually in 100% of cases (except for the three-vessels and trachea view, which was seen in 98% (49/50)) and simultaneously in 98% (49/50). The swing technique was able to generate the three-vessels and trachea view, five-chamber view and/or long-axis view of the aorta, four-chamber view and stomach in 100% of normal cases. In the abnormal cases, the FAST echo algorithm demonstrated the cardiac defects and displayed views that deviated from what was expected from the examination of normal hearts. The swing technique was useful for demonstrating the specific diagnosis due to visualization of an infinite number of cardiac planes in sequence. This novel and simple algorithm can be used to visualize standard fetal echocardiographic planes in normal fetal hearts. The FAST echo algorithm may simplify examination of the fetal heart and could reduce operator dependency. Using this algorithm, inability to obtain expected views or the appearance of abnormal views in the generated planes should raise the index of suspicion for congenital heart disease. Copyright © 2011 ISUOG. Published by John Wiley & Sons, Ltd.

Ultrashort echo time magnetization transfer (UTE-MT) imaging of cortical bone.

PubMed

Chang, Eric Y; Bae, Won C; Shao, Hongda; Biswas, Reni; Li, Shihong; Chen, Jun; Patil, Shantanu; Healey, Robert; D'Lima, Darryl D; Chung, Christine B; Du, Jiang

2015-07-01

Magnetization transfer (MT) imaging is one way to indirectly assess pools of protons with fast transverse relaxation. However, conventional MT imaging sequences are not applicable to short T2 tissues such as cortical bone. Ultrashort echo time (UTE) sequences with TE values as low as 8 µs can detect signals from different water components in cortical bone. In this study we aim to evaluate two-dimensional UTE-MT imaging of cortical bone and its application in assessing cortical bone porosity as measured by micro-computed tomography (μCT) and biomechanical properties. In total, 38 human cadaveric distal femur and proximal tibia bones were sectioned to produce 122 rectangular pieces of cortical bone for quantitative UTE-MT MR imaging, μCT, and biomechanical testing. Off-resonance saturation ratios (OSRs) with a series of MT pulse frequency offsets (Δf) were calculated and compared with porosity assessed with μCT, as well as elastic (modulus, yield stress, and strain) and failure (ultimate stress, failure strain, and energy) properties, using Pearson correlation and linear regression. A moderately strong negative correlation was observed between OSR and μCT porosity (R(2)  = 0.46-0.51), while a moderate positive correlation was observed between OSR and yield stress (R(2)  = 0.25-0.30) and failure stress (R(2)  = 0.31-0.35), and a weak positive correlation (R(2)  = 0.09-0.12) between OSR and Young's modulus at all off-resonance saturation frequencies. OSR determined with the UTE-MT sequence provides quantitative information on cortical bone and is sensitive to μCT porosity and biomechanical function. Copyright © 2015 John Wiley & Sons, Ltd.

A compact Acousto-Optic Lens for 2D and 3D femtosecond based 2-photon microscopy.

PubMed

Kirkby, Paul A; Srinivas Nadella, K M Naga; Silver, R Angus

2010-06-21

We describe a high speed 3D Acousto-Optic Lens Microscope (AOLM) for femtosecond 2-photon imaging. By optimizing the design of the 4 AO Deflectors (AODs) and by deriving new control algorithms, we have developed a compact spherical AOL with a low temporal dispersion that enables 2-photon imaging at 10-fold lower power than previously reported. We show that the AOLM can perform high speed 2D raster-scan imaging (>150 Hz) without scan rate dependent astigmatism. It can deflect and focus a laser beam in a 3D random access sequence at 30 kHz and has an extended focusing range (>137 mum; 40X 0.8NA objective). These features are likely to make the AOLM a useful tool for studying fast physiological processes distributed in 3D space.

Multi-contrast MRI registration of carotid arteries based on cross-sectional images and lumen boundaries

NASA Astrophysics Data System (ADS)

Wu, Yu-Xia; Zhang, Xi; Xu, Xiao-Pan; Liu, Yang; Zhang, Guo-Peng; Li, Bao-Juan; Chen, Hui-Jun; Lu, Hong-Bing

2017-02-01

Ischemic stroke has great correlation with carotid atherosclerosis and is mostly caused by vulnerable plaques. It's particularly important to analysis the components of plaques for the detection of vulnerable plaques. Recently plaque analysis based on multi-contrast magnetic resonance imaging has attracted great attention. Though multi-contrast MR imaging has potentials in enhanced demonstration of carotid wall, its performance is hampered by the misalignment of different imaging sequences. In this study, a coarse-to-fine registration strategy based on cross-sectional images and wall boundaries is proposed to solve the problem. It includes two steps: a rigid step using the iterative closest points to register the centerlines of carotid artery extracted from multi-contrast MR images, and a non-rigid step using the thin plate spline to register the lumen boundaries of carotid artery. In the rigid step, the centerline was extracted by tracking the crosssectional images along the vessel direction calculated by Hessian matrix. In the non-rigid step, a shape context descriptor is introduced to find corresponding points of two similar boundaries. In addition, the deterministic annealing technique is used to find a globally optimized solution. The proposed strategy was evaluated by newly developed three-dimensional, fast and high resolution multi-contrast black blood MR imaging. Quantitative validation indicated that after registration, the overlap of two boundaries from different sequences is 95%, and their mean surface distance is 0.12 mm. In conclusion, the proposed algorithm has improved the accuracy of registration effectively for further component analysis of carotid plaques.

Fetal Eye Movements on Magnetic Resonance Imaging

PubMed Central

Woitek, Ramona; Kasprian, Gregor; Lindner, Christian; Stuhr, Fritz; Weber, Michael; Schöpf, Veronika; Brugger, Peter C.; Asenbaum, Ulrika; Furtner, Julia; Bettelheim, Dieter; Seidl, Rainer; Prayer, Daniela

2013-01-01

Objectives Eye movements are the physical expression of upper fetal brainstem function. Our aim was to identify and differentiate specific types of fetal eye movement patterns using dynamic MRI sequences. Their occurrence as well as the presence of conjugated eyeball motion and consistently parallel eyeball position was systematically analyzed. Methods Dynamic SSFP sequences were acquired in 72 singleton fetuses (17–40 GW, three age groups [17–23 GW, 24–32 GW, 33–40 GW]). Fetal eye movements were evaluated according to a modified classification originally published by Birnholz (1981): Type 0: no eye movements; Type I: single transient deviations; Type Ia: fast deviation, slower reposition; Type Ib: fast deviation, fast reposition; Type II: single prolonged eye movements; Type III: complex sequences; and Type IV: nystagmoid. Results In 95.8% of fetuses, the evaluation of eye movements was possible using MRI, with a mean acquisition time of 70 seconds. Due to head motion, 4.2% of the fetuses and 20.1% of all dynamic SSFP sequences were excluded. Eye movements were observed in 45 fetuses (65.2%). Significant differences between the age groups were found for Type I (p = 0.03), Type Ia (p = 0.031), and Type IV eye movements (p = 0.033). Consistently parallel bulbs were found in 27.3–45%. Conclusions In human fetuses, different eye movement patterns can be identified and described by MRI in utero. In addition to the originally classified eye movement patterns, a novel subtype has been observed, which apparently characterizes an important step in fetal brainstem development. We evaluated, for the first time, eyeball position in fetuses. Ultimately, the assessment of fetal eye movements by MRI yields the potential to identify early signs of brainstem dysfunction, as encountered in brain malformations such as Chiari II or molar tooth malformations. PMID:24194885

Magnetic resonance imaging of granular materials

NASA Astrophysics Data System (ADS)

Stannarius, Ralf

2017-05-01

Magnetic Resonance Imaging (MRI) has become one of the most important tools to screen humans in medicine; virtually every modern hospital is equipped with a Nuclear Magnetic Resonance (NMR) tomograph. The potential of NMR in 3D imaging tasks is by far greater, but there is only "a handful" of MRI studies of particulate matter. The method is expensive, time-consuming, and requires a deep understanding of pulse sequences, signal acquisition, and processing. We give a short introduction into the physical principles of this imaging technique, describe its advantages and limitations for the screening of granular matter, and present a number of examples of different application purposes, from the exploration of granular packing, via the detection of flow and particle diffusion, to real dynamic measurements. Probably, X-ray computed tomography is preferable in most applications, but fast imaging of single slices with modern MRI techniques is unmatched, and the additional opportunity to retrieve spatially resolved flow and diffusion profiles without particle tracking is a unique feature.

3D Fast Spin Echo T2-weighted Contrast for Imaging the Female Cervix

NASA Astrophysics Data System (ADS)

Vargas Sanchez, Andrea Fernanda

Magnetic Resonance Imaging (MRI) with T2-weighted contrast is the preferred modality for treatment planning and monitoring of cervical cancer. Current clinical protocols image the volume of interest multiple times with two dimensional (2D) T2-weighted MRI techniques. It is of interest to replace these multiple 2D acquisitions with a single three dimensional (3D) MRI acquisition to save time. However, at present the image contrast of standard 3D MRI does not distinguish cervical healthy tissue from cancerous tissue. The purpose of this thesis is to better understand the underlying factors that govern the contrast of 3D MRI and exploit this understanding via sequence modifications to improve the contrast. Numerical simulations are developed to predict observed contrast alterations and to propose an improvement. Improvements of image contrast are shown in simulation and with healthy volunteers. Reported results are only preliminary but a promising start to establish definitively 3D MRI for cervical cancer applications.

DSA Image Blood Vessel Skeleton Extraction Based on Anti-concentration Diffusion and Level Set Method

NASA Astrophysics Data System (ADS)

Xu, Jing; Wu, Jian; Feng, Daming; Cui, Zhiming

Serious types of vascular diseases such as carotid stenosis, aneurysm and vascular malformation may lead to brain stroke, which are the third leading cause of death and the number one cause of disability. In the clinical practice of diagnosis and treatment of cerebral vascular diseases, how to do effective detection and description of the vascular structure of two-dimensional angiography sequence image that is blood vessel skeleton extraction has been a difficult study for a long time. This paper mainly discussed two-dimensional image of blood vessel skeleton extraction based on the level set method, first do the preprocessing to the DSA image, namely uses anti-concentration diffusion model for the effective enhancement and uses improved Otsu local threshold segmentation technology based on regional division for the image binarization, then vascular skeleton extraction based on GMM (Group marching method) with fast sweeping theory was actualized. Experiments show that our approach not only improved the time complexity, but also make a good extraction results.

The segmentation of bones in pelvic CT images based on extraction of key frames.

PubMed

Yu, Hui; Wang, Haijun; Shi, Yao; Xu, Ke; Yu, Xuyao; Cao, Yuzhen

2018-05-22

Bone segmentation is important in computed tomography (CT) imaging of the pelvis, which assists physicians in the early diagnosis of pelvic injury, in planning operations, and in evaluating the effects of surgical treatment. This study developed a new algorithm for the accurate, fast, and efficient segmentation of the pelvis. The proposed method consists of two main parts: the extraction of key frames and the segmentation of pelvic CT images. Key frames were extracted based on pixel difference, mutual information and normalized correlation coefficient. In the pelvis segmentation phase, skeleton extraction from CT images and a marker-based watershed algorithm were combined to segment the pelvis. To meet the requirements of clinical application, physician's judgment is needed. Therefore the proposed methodology is semi-automated. In this paper, 5 sets of CT data were used to test the overlapping area, and 15 CT images were used to determine the average deviation distance. The average overlapping area of the 5 sets was greater than 94%, and the minimum average deviation distance was approximately 0.58 pixels. In addition, the key frame extraction efficiency and the running time of the proposed method were evaluated on 20 sets of CT data. For each set, approximately 13% of the images were selected as key frames, and the average processing time was approximately 2 min (the time for manual marking was not included). The proposed method is able to achieve accurate, fast, and efficient segmentation of pelvic CT image sequences. Segmentation results not only provide an important reference for early diagnosis and decisions regarding surgical procedures, they also offer more accurate data for medical image registration, recognition and 3D reconstruction.

An enhanced fast scanning algorithm for image segmentation

NASA Astrophysics Data System (ADS)

Ismael, Ahmed Naser; Yusof, Yuhanis binti

2015-12-01

Segmentation is an essential and important process that separates an image into regions that have similar characteristics or features. This will transform the image for a better image analysis and evaluation. An important benefit of segmentation is the identification of region of interest in a particular image. Various algorithms have been proposed for image segmentation and this includes the Fast Scanning algorithm which has been employed on food, sport and medical images. It scans all pixels in the image and cluster each pixel according to the upper and left neighbor pixels. The clustering process in Fast Scanning algorithm is performed by merging pixels with similar neighbor based on an identified threshold. Such an approach will lead to a weak reliability and shape matching of the produced segments. This paper proposes an adaptive threshold function to be used in the clustering process of the Fast Scanning algorithm. This function used the gray'value in the image's pixels and variance Also, the level of the image that is more the threshold are converted into intensity values between 0 and 1, and other values are converted into intensity values zero. The proposed enhanced Fast Scanning algorithm is realized on images of the public and private transportation in Iraq. Evaluation is later made by comparing the produced images of proposed algorithm and the standard Fast Scanning algorithm. The results showed that proposed algorithm is faster in terms the time from standard fast scanning.

SU-E-J-240: Development of a Novel 4D MRI Sequence for Real-Time Liver Tumor Tracking During Radiotherapy

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

Zhuang, L; Burmeister, J; Ye, Y

2015-06-15

Purpose: To develop a Novel 4D MRI Technique that is feasible for realtime liver tumor tracking during radiotherapy. Methods: A volunteer underwent an abdominal 2D fast EPI coronal scan on a 3.0T MRI scanner (Siemens Inc., Germany). An optimal set of parameters was determined based on image quality and scan time. A total of 23 slices were scanned to cover the whole liver in the test scan. For each scan position, the 2D images were retrospectively sorted into multiple phases based on breathing signal extracted from the images. Consequently the 2D slices with same phase numbers were stacked to formmore » one 3D image. Multiple phases of 3D images formed the 4D MRI sequence representing one breathing cycle. Results: The optimal set of scan parameters were: TR= 57ms, TE= 19ms, FOV read= 320mm and flip angle= 30°, which resulted in a total scan time of 14s for 200 frames (FMs) per slice and image resolution of (2.5mm,2.5mm,5.0mm) in three directions. Ten phases of 3D images were generated, each of which had 23 slices. Based on our test scan, only 100FMs were necessary for the phase sorting process which may lower the scan time to 7s/100FMs/slice. For example, only 5 slices/35s are necessary for a 4D MRI scan to cover liver tumor size ≤ 2cm leading to the possibility of tumor trajectory tracking every 35s during treatment. Conclusion: The novel 4D MRI technique we developed can reconstruct a 4D liver MRI sequence representing one breathing cycle (7s/ slice) without an external monitor. This technique can potentially be used for real-time liver tumor tracking during radiotherapy.« less

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.

Evaluation of shoulder pathology: three-dimensional enhanced T1 high-resolution isotropic volume excitation MR vs two-dimensional fast spin echo T2 fat saturation MR.

PubMed

Park, H J; Lee, S Y; Kim, M S; Choi, S H; Chung, E C; Kook, S H; Kim, E

2015-03-01

To evaluate the diagnostic accuracy of three-dimensional (3D) enhanced T1 high-resolution isotropic volume excitation (eTHRIVE) shoulder MR for the detection of rotator cuff tears, labral lesions and calcific tendonitis of the rotator cuff in comparison with two-dimensional (2D) fast spin echo T2 fat saturation (FS) MR. This retrospective study included 73 patients who underwent shoulder MRI using the eTHRIVE technique. Shoulder MR images were interpreted separately by two radiologists. They evaluated anatomic identification and image quality of the shoulder joint on routine MRI sequences (axial and oblique coronal T2 FS images) and compared them with the reformatted eTHRIVE images. The images were scored on a four-point scale (0, poor; 1, questionable; 2, adequate; 3, excellent) according to the degree of homogeneous and sufficient fat saturation to penetrate bone and soft tissue, visualization of the glenoid labrum and distinction of the supraspinatus tendon (SST). The diagnostic accuracy of eTHRIVE images compared with routine MRI sequences was evaluated in the setting of rotator cuff tears, glenoid labral injuries and calcific tendonitis of the SST. Fat saturation scores for eTHRIVE were significantly higher than those of the T2 FS for both radiologists. The sensitivity and accuracy of the T2 FS in diagnosing rotor cuff tears were >90%, whereas sensitivity and accuracy of the eTHRIVE method were significantly lower. The sensitivity, specificity and accuracy of both images in diagnosing labral injuries and calcific tendonitis were similar and showed no significant differences. The specificity of both images for the diagnosis of labral injuries and calcific tendonitis was higher than the sensitivities. The accuracy of 3D eTHRIVE imaging was comparable to that of 2D FSE T2 FS for the diagnosis of glenoid labral injury and calcific tendonitis of SST. The 3D eTHRIVE technique was superior to 2D FSE T2 FS in terms of fat saturation. Overall, 3D eTHRIVE was inferior to T2 FS in the evaluation of rotator cuff tears because of poor contrast between joint fluid and tendons. The accuracy of 3D eTHRIVE imaging is comparable to that of 2D FSE T2 FS for the diagnosis of glenoid labral injury and calcific tendonitis of SST.

An objective electrophysiological marker of face individualisation impairment in acquired prosopagnosia with fast periodic visual stimulation.

PubMed

Liu-Shuang, Joan; Torfs, Katrien; Rossion, Bruno

2016-03-01

One of the most striking pieces of evidence for a specialised face processing system in humans is acquired prosopagnosia, i.e. the inability to individualise faces following brain damage. However, a sensitive and objective non-behavioural marker for this deficit is difficult to provide with standard event-related potentials (ERPs), such as the well-known face-related N170 component reported and investigated in-depth by our late distinguished colleague Shlomo Bentin. Here we demonstrate that fast periodic visual stimulation (FPVS) in electrophysiology can quantify face individualisation impairment in acquired prosopagnosia. In Experiment 1 (Liu-Shuang et al., 2014), identical faces were presented at a rate of 5.88 Hz (i.e., ≈ 6 images/s, SOA=170 ms, 1 fixation per image), with different faces appearing every 5th face (5.88 Hz/5=1.18 Hz). Responses of interest were identified at these predetermined frequencies (i.e., objectively) in the EEG frequency-domain data. A well-studied case of acquired prosopagnosia (PS) and a group of age- and gender-matched controls completed only 4 × 1-min stimulation sequences, with an orthogonal fixation cross task. Contrarily to controls, PS did not show face individualisation responses at 1.18 Hz, in line with her prosopagnosia. However, her response at 5.88 Hz, reflecting general visual processing, was within the normal range. In Experiment 2 (Rossion et al., 2015), we presented natural (i.e., unsegmented) images of objects at 5.88 Hz, with face images shown every 5th image (1.18 Hz). In accordance with her preserved ability to categorise a face as a face, and despite extensive brain lesions potentially affecting the overall EEG signal-to-noise ratio, PS showed 1.18 Hz face-selective responses within the normal range. Collectively, these findings show that fast periodic visual stimulation provides objective and sensitive electrophysiological markers of preserved and impaired face processing abilities in the neuropsychological population. Copyright © 2015 Elsevier Ltd. All rights reserved.

MEG source imaging method using fast L1 minimum-norm and its applications to signals with brain noise and human resting-state source amplitude images.

PubMed

Huang, Ming-Xiong; Huang, Charles W; Robb, Ashley; Angeles, AnneMarie; Nichols, Sharon L; Baker, Dewleen G; Song, Tao; Harrington, Deborah L; Theilmann, Rebecca J; Srinivasan, Ramesh; Heister, David; Diwakar, Mithun; Canive, Jose M; Edgar, J Christopher; Chen, Yu-Han; Ji, Zhengwei; Shen, Max; El-Gabalawy, Fady; Levy, Michael; McLay, Robert; Webb-Murphy, Jennifer; Liu, Thomas T; Drake, Angela; Lee, Roland R

2014-01-01

The present study developed a fast MEG source imaging technique based on Fast Vector-based Spatio-Temporal Analysis using a L1-minimum-norm (Fast-VESTAL) and then used the method to obtain the source amplitude images of resting-state magnetoencephalography (MEG) signals for different frequency bands. The Fast-VESTAL technique consists of two steps. First, L1-minimum-norm MEG source images were obtained for the dominant spatial modes of sensor-waveform covariance matrix. Next, accurate source time-courses with millisecond temporal resolution were obtained using an inverse operator constructed from the spatial source images of Step 1. Using simulations, Fast-VESTAL's performance was assessed for its 1) ability to localize multiple correlated sources; 2) ability to faithfully recover source time-courses; 3) robustness to different SNR conditions including SNR with negative dB levels; 4) capability to handle correlated brain noise; and 5) statistical maps of MEG source images. An objective pre-whitening method was also developed and integrated with Fast-VESTAL to remove correlated brain noise. Fast-VESTAL's performance was then examined in the analysis of human median-nerve MEG responses. The results demonstrated that this method easily distinguished sources in the entire somatosensory network. Next, Fast-VESTAL was applied to obtain the first whole-head MEG source-amplitude images from resting-state signals in 41 healthy control subjects, for all standard frequency bands. Comparisons between resting-state MEG sources images and known neurophysiology were provided. Additionally, in simulations and cases with MEG human responses, the results obtained from using conventional beamformer technique were compared with those from Fast-VESTAL, which highlighted the beamformer's problems of signal leaking and distorted source time-courses. © 2013.

MEG Source Imaging Method using Fast L1 Minimum-norm and its Applications to Signals with Brain Noise and Human Resting-state Source Amplitude Images

PubMed Central

Huang, Ming-Xiong; Huang, Charles W.; Robb, Ashley; Angeles, AnneMarie; Nichols, Sharon L.; Baker, Dewleen G.; Song, Tao; Harrington, Deborah L.; Theilmann, Rebecca J.; Srinivasan, Ramesh; Heister, David; Diwakar, Mithun; Canive, Jose M.; Edgar, J. Christopher; Chen, Yu-Han; Ji, Zhengwei; Shen, Max; El-Gabalawy, Fady; Levy, Michael; McLay, Robert; Webb-Murphy, Jennifer; Liu, Thomas T.; Drake, Angela; Lee, Roland R.

2014-01-01

The present study developed a fast MEG source imaging technique based on Fast Vector-based Spatio-Temporal Analysis using a L1-minimum-norm (Fast-VESTAL) and then used the method to obtain the source amplitude images of resting-state magnetoencephalography (MEG) signals for different frequency bands. The Fast-VESTAL technique consists of two steps. First, L1-minimum-norm MEG source images were obtained for the dominant spatial modes of sensor-waveform covariance matrix. Next, accurate source time-courses with millisecond temporal resolution were obtained using an inverse operator constructed from the spatial source images of Step 1. Using simulations, Fast-VESTAL’s performance of was assessed for its 1) ability to localize multiple correlated sources; 2) ability to faithfully recover source time-courses; 3) robustness to different SNR conditions including SNR with negative dB levels; 4) capability to handle correlated brain noise; and 5) statistical maps of MEG source images. An objective pre-whitening method was also developed and integrated with Fast-VESTAL to remove correlated brain noise. Fast-VESTAL’s performance was then examined in the analysis of human mediannerve MEG responses. The results demonstrated that this method easily distinguished sources in the entire somatosensory network. Next, Fast-VESTAL was applied to obtain the first whole-head MEG source-amplitude images from resting-state signals in 41 healthy control subjects, for all standard frequency bands. Comparisons between resting-state MEG sources images and known neurophysiology were provided. Additionally, in simulations and cases with MEG human responses, the results obtained from using conventional beamformer technique were compared with those from Fast-VESTAL, which highlighted the beamformer’s problems of signal leaking and distorted source time-courses. PMID:24055704

A new and fast method for preparing high quality lambda DNA suitable for sequencing.

PubMed Central

Manfioletti, G; Schneider, C

1988-01-01

A method is described for the rapid purification of high quality lambda DNA. The method can be used from either liquid or plate lysates and on a small scale or a large scale. It relies on the preadsobtion of all polyanions present in the lysate to an "insoluble" anion-exchange matrix (DEAE or TEAE). Phage particles are then disrupted by combined treatment with EDTA/proteinase K and the resulting DNA is precipitated by the addition of the cationic detergent cetyl (or hexadecyl)-trimethyl ammonium bromide-CTAB ("soluble" anion-exchange matrix). The precipitated CTAB-DNA complex is then exchanged to Na-DNA and ethanol precipitated. The resultant purified DNA is suitable for enzymatic reactions and provides a high quality template for dideoxy-sequence analysis. Images PMID:2966928

Random forest regression for magnetic resonance image synthesis.

PubMed

Jog, Amod; Carass, Aaron; Roy, Snehashis; Pham, Dzung L; Prince, Jerry L

2017-01-01

By choosing different pulse sequences and their parameters, magnetic resonance imaging (MRI) can generate a large variety of tissue contrasts. This very flexibility, however, can yield inconsistencies with MRI acquisitions across datasets or scanning sessions that can in turn cause inconsistent automated image analysis. Although image synthesis of MR images has been shown to be helpful in addressing this problem, an inability to synthesize both T 2 -weighted brain images that include the skull and FLuid Attenuated Inversion Recovery (FLAIR) images has been reported. The method described herein, called REPLICA, addresses these limitations. REPLICA is a supervised random forest image synthesis approach that learns a nonlinear regression to predict intensities of alternate tissue contrasts given specific input tissue contrasts. Experimental results include direct image comparisons between synthetic and real images, results from image analysis tasks on both synthetic and real images, and comparison against other state-of-the-art image synthesis methods. REPLICA is computationally fast, and is shown to be comparable to other methods on tasks they are able to perform. Additionally REPLICA has the capability to synthesize both T 2 -weighted images of the full head and FLAIR images, and perform intensity standardization between different imaging datasets. Copyright © 2016 Elsevier B.V. All rights reserved.

Alleviating artifacts in 1H MRI thermometry by single scan spatiotemporal encoding.

PubMed

Schmidt, Rita; Frydman, Lucio

2013-10-01

Recent years have seen an increased interest in combining MRI thermometry with devices capable of destroying malignancies by heat ablation. Expected from the MR protocols are accurate and fast thermal characterizations, providing real time feedback on restricted tissue volumes and/or rapidly moving organs like liver. This article explores the potential advantages of relying on spatiotemporally encoded (SPEN) sequences for retrieving real-time thermometric images based on the water's proton resonance frequency (PRF) shifts. Hybrid spatiotemporal/k-space encoding single-scan MRI experiments were implemented on animal and human scanners, and their abilities to deliver single- and multi-slice real-time thermometric measurements based on PRF-derived phase maps in phantoms and in vivo, were compared against echo planar imaging (EPI) and gradient-echo counterparts. Under comparable acquisition conditions, SPEN exhibited advantages vis-à-vis EPI in terms of dealing with inhomogeneous magnetic field distortions, with shifts arising due to changes in the central frequency offsets, with PRF distributions, and for zooming into restricted fields-of-view without special pulse sequence provisions. This work confirms the ability of SPEN sequences, particularly when implemented under fully-refocused conditions, to exploit their built-in robustness to shift- and field-derived inhomogeneities for monitoring thermal changes in real-time under in vitro and in vivo conditions.

Vehicle counting system using real-time video processing

NASA Astrophysics Data System (ADS)

Crisóstomo-Romero, Pedro M.

2006-02-01

Transit studies are important for planning a road network with optimal vehicular flow. A vehicular count is essential. This article presents a vehicle counting system based on video processing. An advantage of such system is the greater detail than is possible to obtain, like shape, size and speed of vehicles. The system uses a video camera placed above the street to image transit in real-time. The video camera must be placed at least 6 meters above the street level to achieve proper acquisition quality. Fast image processing algorithms and small image dimensions are used to allow real-time processing. Digital filters, mathematical morphology, segmentation and other techniques allow identifying and counting all vehicles in the image sequences. The system was implemented under Linux in a 1.8 GHz Pentium 4 computer. A successful count was obtained with frame rates of 15 frames per second for images of size 240x180 pixels and 24 frames per second for images of size 180x120 pixels, thus being able to count vehicles whose speeds do not exceed 150 km/h.

The role of MR imaging in detection of hepatic iron overload in patients with cirrhosis of different origins

PubMed Central

2010-01-01

Background There are many pathological conditions with hepatic iron overload. Classical definite diagnostic methods of these disorders are invasive and based on a direct tissue biopsy material. For the last years the role of MR imaging in liver diagnostics has been increasing. MRI shows changes of liver intensity in patients with hepatic iron overload. Changes in MR signal are an indirect consequence of change of relaxation times T2 and T2*, that can be directly measured. The purpose of the study was to evaluate usefulness of MR imaging in the detection of hepatic iron overload in patients with cirrhosis of different origins. Methods MR imaging at 1.5T was prospectively performed in 44 patients with liver cirrhosis who had undergone liver biopsy with histopathological assessment of hepatic iron deposits. In all patients the following sequences were used: SE, Express, GRE in T2 and T1-weighted images. Signal intensity (SI) was measured on images obtained with each T2 weighted sequence by means of regions of interest, placed in the liver and paraspinal muscles. The correlation between iron overload, histopathological score, serum ferritin and SI ratio was analyzed. Results In 20 patients with iron overload confirmed by the biopsy, the liver parenchyma demonstrated lower signal intensity than that of paraspinal muscles. This effect was visible only in 8 patients with hepatic iron overload in Express T2-weighted images. Higher signal intensity of liver than that of skeletal muscles on GRE - T2 weighted images was noted in 24 patients with cirrhosis and without elevated hepatic iron concentration. We observed a correlation between low and high iron concentration and liver to muscle SI ratio. Conclusion MR imaging is a useful and fast noninvasive diagnostic tool for the detection of liver iron overload in patients with cirrhosis of different origins. Liver to muscle SI ratio in GRE-T2-weighted sequence facilitates to differentiate patients with low and high degree of hepatic iron overload, which correlates with the origin of liver cirrhosis. PMID:20105330

The role of MR imaging in detection of hepatic iron overload in patients with cirrhosis of different origins.

PubMed

Szurowska, Edyta; Sikorska, Katarzyna; Izycka-Swieszewska, E; Nowicki, Tomasz; Romanowski, Tomasz; Bielawski, Krzysztof P; Studniarek, Michał

2010-01-27

There are many pathological conditions with hepatic iron overload. Classical definite diagnostic methods of these disorders are invasive and based on a direct tissue biopsy material. For the last years the role of MR imaging in liver diagnostics has been increasing. MRI shows changes of liver intensity in patients with hepatic iron overload. Changes in MR signal are an indirect consequence of change of relaxation times T2 and T2*, that can be directly measured. The purpose of the study was to evaluate usefulness of MR imaging in the detection of hepatic iron overload in patients with cirrhosis of different origins. MR imaging at 1.5T was prospectively performed in 44 patients with liver cirrhosis who had undergone liver biopsy with histopathological assessment of hepatic iron deposits. In all patients the following sequences were used: SE, Express, GRE in T2 and T1-weighted images. Signal intensity (SI) was measured on images obtained with each T2 weighted sequence by means of regions of interest, placed in the liver and paraspinal muscles. The correlation between iron overload, histopathological score, serum ferritin and SI ratio was analyzed. In 20 patients with iron overload confirmed by the biopsy, the liver parenchyma demonstrated lower signal intensity than that of paraspinal muscles. This effect was visible only in 8 patients with hepatic iron overload in Express T2-weighted images. Higher signal intensity of liver than that of skeletal muscles on GRE - T2 weighted images was noted in 24 patients with cirrhosis and without elevated hepatic iron concentration. We observed a correlation between low and high iron concentration and liver to muscle SI ratio. MR imaging is a useful and fast noninvasive diagnostic tool for the detection of liver iron overload in patients with cirrhosis of different origins.Liver to muscle SI ratio in GRE-T2-weighted sequence facilitates to differentiate patients with low and high degree of hepatic iron overload, which correlates with the origin of liver cirrhosis.

[The 18F-FDG myocardial metabolic imaging in twenty seven pilots with regular aerobic training].

PubMed

Fang, Ting-Zheng; Zhu, Jia-Rui; Chuan, Ling; Zhao, Wen-Rui; Xu, Gen-Xiang; Yang, Min-Fu; He, Zuo-Xiang

2009-02-01

To evaluate the characteristics of myocardial (18)F-FDG imaging in pilots with regular aerobic exercise training. Twenty seven healthy male pilots with regular aerobic exercise training were included in this study. The subjects were divided into fasting (n = 17) or non-fasting group (n = 10). Fluorine-18-labeled deoxyglucose and Tc-99m-sestamibi dual-nuclide myocardial imaging were obtained at rest and at target heart rate during bicycle ergometer test. The exercise and rest myocardial perfusion imaging were analyzed for myocardial ischemia presence. The myocardial metabolism imaging was analyzed with the visual semi-quantitative analyses model of seventeen segments. The secondary-extreme heart rate (195-age) was achieved in all subjects. There was no myocardial ischemia in all perfusion imaging. In the visual qualitative analyses, four myocardial metabolism imaging failed in the fasting group while one failed in the non-fasting group (P > 0.05). In the visual semi-quantitative analyses, myocardial metabolism imaging scores at rest or exercise in all segments were similar between two groups (P > 0.05). In the fasting group, the myocardial metabolism imaging scores during exercise were significantly higher than those at rest in 6 segments (P < 0.05). In the non-fasting group, the scores of 3 exercise myocardial metabolism imaging were significantly higher than those at rest (P < 0.05). Satisfactory high-quality myocardial metabolism imaging could be obtained at fasting and exercise situations in subjects with regular aerobic exercise.

FAST - FREEDOM ASSEMBLY SEQUENCING TOOL PROTOTYPE

NASA Technical Reports Server (NTRS)

Borden, C. S.

1994-01-01

FAST is a project management tool designed to optimize the assembly sequence of Space Station Freedom. An appropriate assembly sequence coordinates engineering, design, utilization, transportation availability, and operations requirements. Since complex designs tend to change frequently, FAST assesses the system level effects of detailed changes and produces output metrics that identify preferred assembly sequences. FAST incorporates Space Shuttle integration, Space Station hardware, on-orbit operations, and programmatic drivers as either precedence relations or numerical data. Hardware sequencing information can either be input directly and evaluated via the "specified" mode of operation or evaluated from the input precedence relations in the "flexible" mode. In the specified mode, FAST takes as its input a list of the cargo elements assigned to each flight. The program determines positions for the cargo elements that maximize the center of gravity (c.g.) margin. These positions are restricted by the geometry of the cargo elements and the location of attachment fittings both in the orbiter and on the cargo elements. FAST calculates every permutation of cargo element location according to its height, trunnion fitting locations, and required intercargo element spacing. Each cargo element is tested in both its normal and reversed orientation (rotated 180 degrees). The best solution is that which maximizes the c.g. margin for each flight. In the flexible mode, FAST begins with the first flight and determines all feasible combinations of cargo elements according to mass, volume, EVA, and precedence relation constraints. The program generates an assembly sequence that meets mass, volume, position, EVA, and precedence constraints while minimizing the total number of Shuttle flights required. Issues associated with ground operations, spacecraft performance, logistics requirements and user requirements will be addressed in future versions of the model. FAST is written in C-Language and has been implemented on DEC VAX series computers running VMS. The program is distributed in executable form. The source code is also provided, but it cannot be compiled without the Tree Manipulation Based Routines (TMBR) package from the Jet Propulsion Laboratory, which is not currently available from COSMIC. The main memory requirement is based on the data used to drive the FAST program. All applications should easily run on an installation with 10Mb of main memory. FAST was developed in 1990 and is a copyrighted work with all copyright vested in NASA. DEC, VAX and VMS are trademarks of Digital Equipment Corporation.

A compact acousto-optic lens for 2D and 3D femtosecond based 2-photon microscopy

PubMed Central

Kirkby, Paul A.; Naga Srinivas, N.K.M.; Silver, R. Angus

2010-01-01

We describe a high speed 3D Acousto-Optic Lens Microscope (AOLM) for femtosecond 2-photon imaging. By optimizing the design of the 4 AO Deflectors (AODs) and by deriving new control algorithms, we have developed a compact spherical AOL with a low temporal dispersion that enables 2-photon imaging at 10-fold lower power than previously reported. We show that the AOLM can perform high speed 2D raster-scan imaging (>150 Hz) without scan rate dependent astigmatism. It can deflect and focus a laser beam in a 3D random access sequence at 30 kHz and has an extended focusing range (>137 μm; 40X 0.8NA objective). These features are likely to make the AOLM a useful tool for studying fast physiological processes distributed in 3D space PMID:20588506

Resolution enhancement of low-quality videos using a high-resolution frame

NASA Astrophysics Data System (ADS)

Pham, Tuan Q.; van Vliet, Lucas J.; Schutte, Klamer

2006-01-01

This paper proposes an example-based Super-Resolution (SR) algorithm of compressed videos in the Discrete Cosine Transform (DCT) domain. Input to the system is a Low-Resolution (LR) compressed video together with a High-Resolution (HR) still image of similar content. Using a training set of corresponding LR-HR pairs of image patches from the HR still image, high-frequency details are transferred from the HR source to the LR video. The DCT-domain algorithm is much faster than example-based SR in spatial domain 6 because of a reduction in search dimensionality, which is a direct result of the compact and uncorrelated DCT representation. Fast searching techniques like tree-structure vector quantization 16 and coherence search1 are also key to the improved efficiency. Preliminary results on MJPEG sequence show promising result of the DCT-domain SR synthesis approach.

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.

High-speed 3D surface measurement with a fringe projection based optical sensor

NASA Astrophysics Data System (ADS)

Bräuer-Burchardt, Christian; Heist, Stefan; Kühmstedt, Peter; Notni, Gunther

2014-05-01

A new optical sensor based on fringe projection technique for the accurate and fast measurement of the surface of objects mainly for industrial inspection tasks is introduced. High-speed fringe projection and image recording with 180 Hz allows 3D rates up to 60 Hz. The high measurement velocity was achieved by consequent fringe code reduction and parallel data processing. Reduction of the image sequence length was obtained by omission of the Gray-code sequence by using the geometric restrictions of the measurement objects. The sensor realizes three different measurement fields between 20 x 20 mm2 and 40 x 40 mm2 with lateral spatial solutions between 10 μm and 20 μm with the same working distance. Measurement object height extension is between +/- 0.5 mm and +/- 2 mm. Height resolution between 1 μm and 5 μm can be achieved depending on the properties of the measurement objects. The sensor may be used e.g. for quality inspection of conductor boards or plugs in real-time industrial applications.

High-accuracy and robust face recognition system based on optical parallel correlator using a temporal image sequence

NASA Astrophysics Data System (ADS)

Watanabe, Eriko; Ishikawa, Mami; Ohta, Maiko; Kodate, Kashiko

2005-09-01

Face recognition is used in a wide range of security systems, such as monitoring credit card use, searching for individuals with street cameras via Internet and maintaining immigration control. There are still many technical subjects under study. For instance, the number of images that can be stored is limited under the current system, and the rate of recognition must be improved to account for photo shots taken at different angles under various conditions. We implemented a fully automatic Fast Face Recognition Optical Correlator (FARCO) system by using a 1000 frame/s optical parallel correlator designed and assembled by us. Operational speed for the 1: N (i.e. matching a pair of images among N, where N refers to the number of images in the database) identification experiment (4000 face images) amounts to less than 1.5 seconds, including the pre/post processing. From trial 1: N identification experiments using FARCO, we acquired low error rates of 2.6% False Reject Rate and 1.3% False Accept Rate. By making the most of the high-speed data-processing capability of this system, much more robustness can be achieved for various recognition conditions when large-category data are registered for a single person. We propose a face recognition algorithm for the FARCO while employing a temporal image sequence of moving images. Applying this algorithm to a natural posture, a two times higher recognition rate scored compared with our conventional system. The system has high potential for future use in a variety of purposes such as search for criminal suspects by use of street and airport video cameras, registration of babies at hospitals or handling of an immeasurable number of images in a database.

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

Spread-Spectrum Beamforming and Clutter Filtering for Plane-Wave Color Doppler Imaging.

PubMed

Mansour, Omar; Poepping, Tamie L; Lacefield, James C

2016-07-21

Plane-wave imaging is desirable for its ability to achieve high frame rates, allowing the capture of fast dynamic events and continuous Doppler data. In most implementations of plane-wave imaging, multiple low-resolution images from different plane wave tilt angles are compounded to form a single high-resolution image, thereby reducing the frame rate. Compounding improves the lateral beam profile in the high-resolution image, but it also acts as a low-pass filter in slow time that causes attenuation and aliasing of signals with high Doppler shifts. This paper introduces a spread-spectrum color Doppler imaging method that produces high-resolution images without the use of compounding, thereby eliminating the tradeoff between beam quality, maximum unaliased Doppler frequency, and frame rate. The method uses a long, random sequence of transmit angles rather than a linear sweep of plane wave directions. The random angle sequence randomizes the phase of off-focus (clutter) signals, thereby spreading the clutter power in the Doppler spectrum, while keeping the spectrum of the in-focus signal intact. The ensemble of randomly tilted low-resolution frames also acts as the Doppler ensemble, so it can be much longer than a conventional linear sweep, thereby improving beam formation while also making the slow-time Doppler sampling frequency equal to the pulse repetition frequency. Experiments performed using a carotid artery phantom with constant flow demonstrate that the spread-spectrum method more accurately measures the parabolic flow profile of the vessel and outperforms conventional plane-wave Doppler in both contrast resolution and estimation of high flow velocities. The spread-spectrum method is expected to be valuable for Doppler applications that require measurement of high velocities at high frame rates.

TH-EF-BRA-11: Feasibility of Super-Resolution Time-Resolved 4DMRI for Multi-Breath Volumetric Motion Simulation in Radiotherapy Planning

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

Li, G; Zakian, K; Deasy, J

Purpose: To develop a novel super-resolution time-resolved 4DMRI technique to evaluate multi-breath, irregular and complex organ motion without respiratory surrogate for radiotherapy planning. Methods: The super-resolution time-resolved (TR) 4DMRI approach combines a series of low-resolution 3D cine MRI images acquired during free breathing (FB) with a high-resolution breath-hold (BH) 3DMRI via deformable image registration (DIR). Five volunteers participated in the study under an IRB-approved protocol. The 3D cine images with voxel size of 5×5×5 mm{sup 3} at two volumes per second (2Hz) were acquired coronally using a T1 fast field echo sequence, half-scan (0.8) acceleration, and SENSE (3) parallel imaging.more » Phase-encoding was set in the lateral direction to minimize motion artifacts. The BH image with voxel size of 2×2×2 mm{sup 3} was acquired using the same sequence within 10 seconds. A demons-based DIR program was employed to produce super-resolution 2Hz 4DMRI. Registration quality was visually assessed using difference images between TR 4DMRI and 3D cine and quantitatively assessed using average voxel correlation. The fidelity of the 3D cine images was assessed using a gel phantom and a 1D motion platform by comparing mobile and static images. Results: Owing to voxel intensity similarity using the same MRI scanning sequence, accurate DIR between FB and BH images is achieved. The voxel correlations between 3D cine and TR 4DMRI are greater than 0.92 in all cases and the difference images illustrate minimal residual error with little systematic patterns. The 3D cine images of the mobile gel phantom preserve object geometry with minimal scanning artifacts. Conclusion: The super-resolution time-resolved 4DMRI technique has been achieved via DIR, providing a potential solution for multi-breath motion assessment. Accurate DIR mapping has been achieved to map high-resolution BH images to low-resolution FB images, producing 2Hz volumetric high-resolution 4DMRI. Further validation and improvement are still required prior to clinical applications. This study is in part supported by the NIH (U54CA137788/U54CA132378).« less

An integrated approach to fast and informative morphological vouchering of nematodes for applications in molecular barcoding

PubMed Central

De Ley, Paul; De Ley, Irma Tandingan; Morris, Krystalynne; Abebe, Eyualem; Mundo-Ocampo, Manuel; Yoder, Melissa; Heras, Joseph; Waumann, Dora; Rocha-Olivares, Axayácatl; Jay Burr, A.H; Baldwin, James G; Thomas, W. Kelley

2005-01-01

Molecular surveys of meiofaunal diversity face some interesting methodological challenges when it comes to interstitial nematodes from soils and sediments. Morphology-based surveys are greatly limited in processing speed, while barcoding approaches for nematodes are hampered by difficulties of matching sequence data with traditional taxonomy. Intermediate technology is needed to bridge the gap between both approaches. An example of such technology is video capture and editing microscopy, which consists of the recording of taxonomically informative multifocal series of microscopy images as digital video clips. The integration of multifocal imaging with sequence analysis of the D2D3 region of large subunit (LSU) rDNA is illustrated here in the context of a combined morphological and barcode sequencing survey of marine nematodes from Baja California and California. The resulting video clips and sequence data are made available online in the database NemATOL (http://nematol.unh.edu/). Analyses of 37 barcoded nematodes suggest that these represent at least 32 species, none of which matches available D2D3 sequences in public databases. The recorded multifocal vouchers allowed us to identify most specimens to genus, and will be used to match specimens with subsequent species identifications and descriptions of preserved specimens. Like molecular barcodes, multifocal voucher archives are part of a wider effort at structuring and changing the process of biodiversity discovery. We argue that data-rich surveys and phylogenetic tools for analysis of barcode sequences are an essential component of the exploration of phyla with a high fraction of undiscovered species. Our methods are also directly applicable to other meiofauna such as for example gastrotrichs and tardigrades. PMID:16214752

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.

A programmable systolic array correlator as a trigger processor for electron pairs in rich (ring image Cherenkov) counters

NASA Astrophysics Data System (ADS)

Männer, R.

1989-12-01

This paper describes a systolic array processor for a ring image Cherenkov counter which is capable of identifying pairs of electron circles with a known radius and a certain minimum distance within 15 μs. The processor is a very flexible and fast device. It consists of 128 x 128 processing elements (PEs), where one PE is assigned to each pixel of the image. All PEs run synchronously at 40 MHz. The identification of electron circles is done by correlating the detector image with the proper circle circumference. Circle centers are found by peak detection in the correlation result. A second correlation with a circle disc allows circles of closed electron pairs to be rejected. The trigger decision is generated if a pseudo adder detects at least two remaining circles. The device is controlled by a freely programmable sequencer. A VLSI chip containing 8 x 8 PEs is being developed using a VENUS design system and will be produced in 2μ CMOS technology.

Thought Speed, Mood, and the Experience of Mental Motion.

PubMed

Pronin, Emily; Jacobs, Elana

2008-11-01

This article presents a theoretical account relating thought speed to mood and psychological experience. Thought sequences that occur at a fast speed generally induce more positive affect than do those that occur slowly. Thought speed constitutes one aspect of mental motion. Another aspect involves thought variability, or the degree to which thoughts in a sequence either vary widely from or revolve closely around a theme. Thought sequences possessing more motion (occurring fast and varying widely) generally produce more positive affect than do sequences possessing little motion (occurring slowly and repetitively). When speed and variability oppose each other, such that one is low and the other is high, predictable psychological states also emerge. For example, whereas slow, repetitive thinking can prompt dejection, fast, repetitive thinking can prompt anxiety. This distinction is related to the fact that fast thinking involves greater actual and felt energy than slow thinking does. Effects of mental motion occur independent of the specific content of thought. Their consequences for mood and energy hold psychotherapeutic relevance. © 2008 Association for Psychological Science.

Flexible, fast and accurate sequence alignment profiling on GPGPU with PaSWAS.

PubMed

Warris, Sven; Yalcin, Feyruz; Jackson, Katherine J L; Nap, Jan Peter

2015-01-01

To obtain large-scale sequence alignments in a fast and flexible way is an important step in the analyses of next generation sequencing data. Applications based on the Smith-Waterman (SW) algorithm are often either not fast enough, limited to dedicated tasks or not sufficiently accurate due to statistical issues. Current SW implementations that run on graphics hardware do not report the alignment details necessary for further analysis. With the Parallel SW Alignment Software (PaSWAS) it is possible (a) to have easy access to the computational power of NVIDIA-based general purpose graphics processing units (GPGPUs) to perform high-speed sequence alignments, and (b) retrieve relevant information such as score, number of gaps and mismatches. The software reports multiple hits per alignment. The added value of the new SW implementation is demonstrated with two test cases: (1) tag recovery in next generation sequence data and (2) isotype assignment within an immunoglobulin 454 sequence data set. Both cases show the usability and versatility of the new parallel Smith-Waterman implementation.

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

Non-contrast-enhanced perfusion and ventilation assessment of the human lung by means of fourier decomposition in proton MRI.

PubMed

Bauman, Grzegorz; Puderbach, Michael; Deimling, Michael; Jellus, Vladimir; Chefd'hotel, Christophe; Dinkel, Julien; Hintze, Christian; Kauczor, Hans-Ulrich; Schad, Lothar R

2009-09-01

Assessment of regional lung perfusion and ventilation has significant clinical value for the diagnosis and follow-up of pulmonary diseases. In this work a new method of non-contrast-enhanced functional lung MRI (not dependent on intravenous or inhalative contrast agents) is proposed. A two-dimensional (2D) true fast imaging with steady precession (TrueFISP) pulse sequence (TR/TE = 1.9 ms/0.8 ms, acquisition time [TA] = 112 ms/image) was implemented on a 1.5T whole-body MR scanner. The imaging protocol comprised sets of 198 lung images acquired with an imaging rate of 3.33 images/s in coronal and sagittal view. No electrocardiogram (ECG) or respiratory triggering was used. A nonrigid image registration algorithm was applied to compensate for respiratory motion. Rapid data acquisition allowed observing intensity changes in corresponding lung areas with respect to the cardiac and respiratory frequencies. After a Fourier analysis along the time domain, two spectral lines corresponding to both frequencies were used to calculate the perfusion- and ventilation-weighted images. The described method was applied in preliminary studies on volunteers and patients showing clinical relevance to obtain non-contrast-enhanced perfusion and ventilation data.

CoGI: Towards Compressing Genomes as an Image.

PubMed

Xie, Xiaojing; Zhou, Shuigeng; Guan, Jihong

2015-01-01

Genomic science is now facing an explosive increase of data thanks to the fast development of sequencing technology. This situation poses serious challenges to genomic data storage and transferring. It is desirable to compress data to reduce storage and transferring cost, and thus to boost data distribution and utilization efficiency. Up to now, a number of algorithms / tools have been developed for compressing genomic sequences. Unlike the existing algorithms, most of which treat genomes as one-dimensional text strings and compress them based on dictionaries or probability models, this paper proposes a novel approach called CoGI (the abbreviation of Compressing Genomes as an Image) for genome compression, which transforms the genomic sequences to a two-dimensional binary image (or bitmap), then applies a rectangular partition coding algorithm to compress the binary image. CoGI can be used as either a reference-based compressor or a reference-free compressor. For the former, we develop two entropy-based algorithms to select a proper reference genome. Performance evaluation is conducted on various genomes. Experimental results show that the reference-based CoGI significantly outperforms two state-of-the-art reference-based genome compressors GReEn and RLZ-opt in both compression ratio and compression efficiency. It also achieves comparable compression ratio but two orders of magnitude higher compression efficiency in comparison with XM--one state-of-the-art reference-free genome compressor. Furthermore, our approach performs much better than Gzip--a general-purpose and widely-used compressor, in both compression speed and compression ratio. So, CoGI can serve as an effective and practical genome compressor. The source code and other related documents of CoGI are available at: http://admis.fudan.edu.cn/projects/cogi.htm.

An Imaging Sensor-Aided Vision Navigation Approach that Uses a Geo-Referenced Image Database.

PubMed

Li, Yan; Hu, Qingwu; Wu, Meng; Gao, Yang

2016-01-28

In determining position and attitude, vision navigation via real-time image processing of data collected from imaging sensors is advanced without a high-performance global positioning system (GPS) and an inertial measurement unit (IMU). Vision navigation is widely used in indoor navigation, far space navigation, and multiple sensor-integrated mobile mapping. This paper proposes a novel vision navigation approach aided by imaging sensors and that uses a high-accuracy geo-referenced image database (GRID) for high-precision navigation of multiple sensor platforms in environments with poor GPS. First, the framework of GRID-aided vision navigation is developed with sequence images from land-based mobile mapping systems that integrate multiple sensors. Second, a highly efficient GRID storage management model is established based on the linear index of a road segment for fast image searches and retrieval. Third, a robust image matching algorithm is presented to search and match a real-time image with the GRID. Subsequently, the image matched with the real-time scene is considered to calculate the 3D navigation parameter of multiple sensor platforms. Experimental results show that the proposed approach retrieves images efficiently and has navigation accuracies of 1.2 m in a plane and 1.8 m in height under GPS loss in 5 min and within 1500 m.

An Imaging Sensor-Aided Vision Navigation Approach that Uses a Geo-Referenced Image Database

PubMed Central

Li, Yan; Hu, Qingwu; Wu, Meng; Gao, Yang

2016-01-01

In determining position and attitude, vision navigation via real-time image processing of data collected from imaging sensors is advanced without a high-performance global positioning system (GPS) and an inertial measurement unit (IMU). Vision navigation is widely used in indoor navigation, far space navigation, and multiple sensor-integrated mobile mapping. This paper proposes a novel vision navigation approach aided by imaging sensors and that uses a high-accuracy geo-referenced image database (GRID) for high-precision navigation of multiple sensor platforms in environments with poor GPS. First, the framework of GRID-aided vision navigation is developed with sequence images from land-based mobile mapping systems that integrate multiple sensors. Second, a highly efficient GRID storage management model is established based on the linear index of a road segment for fast image searches and retrieval. Third, a robust image matching algorithm is presented to search and match a real-time image with the GRID. Subsequently, the image matched with the real-time scene is considered to calculate the 3D navigation parameter of multiple sensor platforms. Experimental results show that the proposed approach retrieves images efficiently and has navigation accuracies of 1.2 m in a plane and 1.8 m in height under GPS loss in 5 min and within 1500 m. PMID:26828496

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.

GRAPPA reconstructed wave-CAIPI MP-RAGE at 7 Tesla.

PubMed

Schwarz, Jolanda M; Pracht, Eberhard D; Brenner, Daniel; Reuter, Martin; Stöcker, Tony

2018-04-16

The aim of this project was to develop a GRAPPA-based reconstruction for wave-CAIPI data. Wave-CAIPI fully exploits the 3D coil sensitivity variations by combining corkscrew k-space trajectories with CAIPIRINHA sampling. It reduces artifacts and limits reconstruction induced spatially varying noise enhancement. The GRAPPA-based wave-CAIPI method is robust and does not depend on the accuracy of coil sensitivity estimations. We developed a GRAPPA-based, noniterative wave-CAIPI reconstruction algorithm utilizing multiple GRAPPA kernels. For data acquisition, we implemented a fast 3D magnetization-prepared rapid gradient-echo wave-CAIPI sequence tailored for ultra-high field application. The imaging results were evaluated by comparing the g-factor and the root mean square error to Cartesian CAIPIRINHA acquisitions. Additionally, to assess the performance of subcortical segmentations (calculated by FreeSurfer), the data were analyzed across five subjects. Sixteen-fold accelerated whole brain magnetization-prepared rapid gradient-echo data (1 mm isotropic resolution) were acquired in 40 seconds at 7T. A clear improvement in image quality compared to Cartesian CAIPIRINHA sampling was observed. For the chosen imaging protocol, the results of 16-fold accelerated wave-CAIPI acquisitions were comparable to results of 12-fold accelerated Cartesian CAIPIRINHA. In comparison to the originally proposed SENSitivity Encoding reconstruction of Wave-CAIPI data, the GRAPPA approach provided similar image quality. High-quality, wave-CAIPI magnetization-prepared rapid gradient-echo images can be reconstructed by means of a GRAPPA-based reconstruction algorithm. Even for high acceleration factors, the noniterative reconstruction is robust and does not require coil sensitivity estimations. By altering the aliasing pattern, ultra-fast whole-brain structural imaging becomes feasible. © 2018 International Society for Magnetic Resonance in Medicine.

Large-field high-resolution mosaic movies

NASA Astrophysics Data System (ADS)

Hammerschlag, Robert H.; Sliepen, Guus; Bettonvil, Felix C. M.; Jägers, Aswin P. L.; Sütterlin, Peter; Martin, Sara F.

2012-09-01

Movies with fields-of-view larger than normal for high-resolution telescopes will give a better understanding of processes on the Sun, such as filament and active region developments and their possible interactions. New active regions can influence, by their emergence, their environment to the extent of possibly serving as an igniter of the eruption of a nearby filament. A method to create a large field-of-view is to join several fields-of-view into a mosaic. Fields are imaged quickly one after another using fast telescope-pointing. Such a pointing cycle has been automated at the Dutch Open Telescope (DOT), a high-resolution solar telescope located on the Canary Island La Palma. The observer can draw with the computer mouse the desired total field in the guider-telescope image of the whole Sun. The guider telescope is equipped with an H-alpha filter and electronic enhancement of contrast in the image for good visibility of filaments and prominences. The number and positions of the subfields are calculated automatically and represented by an array of bright points indicating the subfield centers inside the drawn rectangle of the total field on the computer screen with the whole-sun image. When the exposures start the telescope repeats automatically the sequence of subfields. Automatic production of flats is also programmed including defocusing and fast motion over the solar disk of the image field. For the first time mosaic movies were programmed from stored information on automated telescope motions from one field to the next. The mosaic movies fill the gap between whole-sun images with limited resolution of synoptic telescopes including space instruments and small-field high-cadence movies of high-resolution solar telescopes.

HIGH SPEED CAMERA

DOEpatents

Rogers, B.T. Jr.; Davis, W.C.

1957-12-17

This patent relates to high speed cameras having resolution times of less than one-tenth microseconds suitable for filming distinct sequences of a very fast event such as an explosion. This camera consists of a rotating mirror with reflecting surfaces on both sides, a narrow mirror acting as a slit in a focal plane shutter, various other mirror and lens systems as well as an innage recording surface. The combination of the rotating mirrors and the slit mirror causes discrete, narrow, separate pictures to fall upon the film plane, thereby forming a moving image increment of the photographed event. Placing a reflecting surface on each side of the rotating mirror cancels the image velocity that one side of the rotating mirror would impart, so as a camera having this short a resolution time is thereby possible.

Fast calcium and voltage-sensitive dye imaging in enteric neurones reveal calcium peaks associated with single action potential discharge.

PubMed

Michel, K; Michaelis, M; Mazzuoli, G; Mueller, K; Vanden Berghe, P; Schemann, M

2011-12-15

Slow changes in [Ca(2+)](i) reflect increased neuronal activity. Our study demonstrates that single-trial fast [Ca(2+)](i) imaging (≥200 Hz sampling rate) revealed peaks each of which are associated with single spike discharge recorded by consecutive voltage-sensitive dye (VSD) imaging in enteric neurones and nerve fibres. Fast [Ca(2+)](i) imaging also revealed subthreshold fast excitatory postsynaptic potentials. Nicotine-evoked [Ca(2+)](i) peaks were reduced by -conotoxin and blocked by ruthenium red or tetrodotoxin. Fast [Ca(2+)](i) imaging can be used to directly record single action potentials in enteric neurones. [Ca(2+)](i) peaks required opening of voltage-gated sodium and calcium channels as well as Ca(2+) release from intracellular stores.

A Fast-Time Simulation Tool for Analysis of Airport Arrival Traffic

NASA Technical Reports Server (NTRS)

Erzberger, Heinz; Meyn, Larry A.; Neuman, Frank

2004-01-01

The basic objective of arrival sequencing in air traffic control automation is to match traffic demand and airport capacity while minimizing delays. The performance of an automated arrival scheduling system, such as the Traffic Management Advisor developed by NASA for the FAA, can be studied by a fast-time simulation that does not involve running expensive and time-consuming real-time simulations. The fast-time simulation models runway configurations, the characteristics of arrival traffic, deviations from predicted arrival times, as well as the arrival sequencing and scheduling algorithm. This report reviews the development of the fast-time simulation method used originally by NASA in the design of the sequencing and scheduling algorithm for the Traffic Management Advisor. The utility of this method of simulation is demonstrated by examining the effect on delays of altering arrival schedules at a hub airport.

Fast cine-magnetic resonance imaging point tracking for prostate cancer radiation therapy planning

NASA Astrophysics Data System (ADS)

Dowling, J.; Dang, K.; Fox, Chris D.; Chandra, S.; Gill, Suki; Kron, T.; Pham, D.; Foroudi, F.

2014-03-01

The analysis of intra-fraction organ motion is important for improving the precision of radiation therapy treatment delivery. One method to quantify this motion is for one or more observers to manually identify anatomic points of interest (POIs) on each slice of a cine-MRI sequence. However this is labour intensive and inter- and intra- observer variation can introduce uncertainty. In this paper a fast method for non-rigid registration based point tracking in cine-MRI sagittal and coronal series is described which identifies POIs in 0.98 seconds per sagittal slice and 1.35 seconds per coronal slice. The manual and automatic points were highly correlated (r>0.99, p<0.001) for all organs and the difference generally less than 1mm. For prostate planning peristalsis and rectal gas can result in unpredictable out of plane motion, suggesting the results may require manual verification.

Simulator evaluation of the final approach spacing tool

NASA Technical Reports Server (NTRS)

Davis, Thomas J.; Erzberger, Heinz; Green, Steven M.

1990-01-01

The design and simulator evaluation of an automation tool for assisting terminal radar approach controllers in sequencing and spacing traffic onto the final approach course is described. The automation tool, referred to as the Final Approach Spacing Tool (FAST), displays speed and heading advisories for arrivals as well as sequencing information on the controller's radar display. The main functional elements of FAST are a scheduler that schedules and sequences the traffic, a 4-D trajectory synthesizer that generates the advisories, and a graphical interface that displays the information to the controller. FAST was implemented on a high performance workstation. It can be operated as a stand-alone in the Terminal Radar Approach Control (TRACON) Facility or as an element of a system integrated with automation tools in the Air Route Traffic Control Center (ARTCC). FAST was evaluated by experienced TRACON controllers in a real-time air traffic control simulation. Simulation results show that FAST significantly reduced controller workload and demonstrated a potential for an increase in landing rate.

Fast imputation using medium- or low-coverage sequence data

USDA-ARS?s Scientific Manuscript database

Direct imputation from raw sequence reads can be more accurate than calling genotypes first and then imputing, especially if read depth is low or error rates high, but different imputation strategies are required than those used for data from genotyping chips. A fast algorithm to impute from lower t...

[Quality of 3D magnetic resonance imaging of coronary arteries in patients with D-transposition of the great arteries after the Jatene switch procedure].

PubMed

Marín Rodríguez, C; Lancharro Zapata, Á; Rodríguez Ogando, A; Carrasco Muñoz, S; Ruiz Martín, Y; Sánchez Alegre, M L; Maroto Alvaro, E

2015-01-01

To evaluate the quality of images obtained with 3D balanced fast-field echo whole heart (WH3D) MRI sequences for assessing the coronary anastomosis and coronary stenosis in patients with D-transposition of the great arteries who have undergone the Jatene switch procedure. We retrieved 100 WH3D studies done in 83 patients who had undergone the Jatene switch procedure from our pediatric cardiac MRI database; 84 of these studies fulfilled the criteria for inclusion in the study. We evaluated coronary stenoses on WH3D MR images and their correlation with coronary CT or angiography images. We retrospectively studied the quality of the images of the proximal coronary arteries using a four-point scale and correlating the findings with age, heart rate, and heart size. Of the 84 studies, 4 (4.8%) were of a quality considered «insufficient for diagnosis», 7 (8.3%) were considered «fair», 23 (27.4%) «good», and 50 (59.5%) «excellent». The quality of the image of the coronary arteries was significantly correlated with heart rate. MRI detected stenosis in the origin of the coronary arteries in 9 (10.7%) studies. Images obtained with the WH3D MRI sequence in patients who had undergone the Jatene procedure were of diagnostic quality in most cases and were better in patients with lower heart rates. In 10.7%, stenosis in the origin of the coronary arteries that required new studies was detected. Copyright © 2014 SERAM. Published by Elsevier España, S.L.U. All rights reserved.

[Imaging of the intrahepatic biliary tree with thick slice MR cholangiography].

PubMed

Leclerc, J C; Cannard, L; Lefèvre, F; Debelle, L; Béot, S; Boccaccini, H; Bazin, C; Régent, D

2001-02-01

To assess the value of single shot fast spin echo MR sequence (SS-FSE) in the evaluation of the normal and pathologic intrahepatic biliary tree. 418 consecutive patients (457 examinations) referred for clinical and/or biological suspicion of biliary obstruction underwent MR cholangiopancreatography (MRCP). All patients were imaged with a Signa 1.5 T GE MR unit, with High Gradient Field Strength and Torso Phased Array Coil. Biliary ducts were imaged with SS-FSE sequence, coronal and oblique coronal 20 mm thick slices on a 256 x 256 matrix. Total acquisition time was 1 second. Source images were reviewed by two radiologists blinded to clinical information. In case of disagreement, a third radiologist's opinion was requested. In all cases, MRCP results were compared with direct biliary tract evaluation, other imaging studies and clinical and biological follow-up. In all cases, MRCP produced high quality images. Numerous branch of division were observed although the peripheral intrahepatic ducts were well seen in more than 90% in an area 2 cm below the capsule. The number of division was statistically higher when mechanical obstruction was present. Intrahepatic calculi or peripheral cholangiocarcinoma were well detect by MRCP. For the detection of cholangitis, MRCP sensitivity was 87.5% but the positive predictive value was only 57.7% because of a high number of false positive. The diagnosis of primary sclerosing cholangitis must be made only on strict criteria and slightly dilated peripheral bile ducts unconnected to the central ducts in several hepatic segments were a characteristic MR sign of primary sclerosing cholangitis. MRCP can be proposed as a first intention imaging technique for the evaluation of intrahepatic ducts.

Lip reading using neural networks

NASA Astrophysics Data System (ADS)

Kalbande, Dhananjay; Mishra, Akassh A.; Patil, Sanjivani; Nirgudkar, Sneha; Patel, Prashant

2011-10-01

Computerized lip reading, or speech reading, is concerned with the difficult task of converting a video signal of a speaking person to written text. It has several applications like teaching deaf and dumb to speak and communicate effectively with the other people, its crime fighting potential and invariance to acoustic environment. We convert the video of the subject speaking vowels into images and then images are further selected manually for processing. However, several factors like fast speech, bad pronunciation, and poor illumination, movement of face, moustaches and beards make lip reading difficult. Contour tracking methods and Template matching are used for the extraction of lips from the face. K Nearest Neighbor algorithm is then used to classify the 'speaking' images and the 'silent' images. The sequence of images is then transformed into segments of utterances. Feature vector is calculated on each frame for all the segments and is stored in the database with properly labeled class. Character recognition is performed using modified KNN algorithm which assigns more weight to nearer neighbors. This paper reports the recognition of vowels using KNN algorithms

A possible application of magnetic resonance imaging for pharmaceutical research.

PubMed

Kowalczuk, Joanna; Tritt-Goc, Jadwiga

2011-03-18

Magnetic resonance imaging (MRI) is a non-destructive and non-invasive method, the experiment can be conducted in situ and allows the studying of the sample and the different processes in vitro or in vivo. 1D, 2D or 3D imaging can be undertaken. MRI is nowadays most widely used in medicine as a clinical diagnostic tool, but has still seen limited application in the food and pharmaceutical sciences. The different imaging pulse sequences of MRI allow to image the processes that take place in a wide scale range from ms (dissolution of compact tablets) to hours (hydration of drug delivery systems) for mobile as well as for rigid spins, usually protons. The paper gives examples of MRI application of in vitro imaging of pharmaceutical dosage based on hydroxypropyl methylcellulose which have focused on water-penetration, diffusion, polymer swelling, and drug release, characterized with respect to other physical parameters such as pH and the molecular weight of polymer. Tetracycline hydrochloride was used as a model drug. NMR imaging of density distributions and fast kinetics of the dissolution behavior of compact tablets is presented for paracetamol tablets. Copyright © 2010 Elsevier B.V. All rights reserved.

Implementation of compressive sensing for preclinical cine-MRI

NASA Astrophysics Data System (ADS)

Tan, Elliot; Yang, Ming; Ma, Lixin; Zheng, Yahong Rosa

2014-03-01

This paper presents a practical implementation of Compressive Sensing (CS) for a preclinical MRI machine to acquire randomly undersampled k-space data in cardiac function imaging applications. First, random undersampling masks were generated based on Gaussian, Cauchy, wrapped Cauchy and von Mises probability distribution functions by the inverse transform method. The best masks for undersampling ratios of 0.3, 0.4 and 0.5 were chosen for animal experimentation, and were programmed into a Bruker Avance III BioSpec 7.0T MRI system through method programming in ParaVision. Three undersampled mouse heart datasets were obtained using a fast low angle shot (FLASH) sequence, along with a control undersampled phantom dataset. ECG and respiratory gating was used to obtain high quality images. After CS reconstructions were applied to all acquired data, resulting images were quantitatively analyzed using the performance metrics of reconstruction error and Structural Similarity Index (SSIM). The comparative analysis indicated that CS reconstructed images from MRI machine undersampled data were indeed comparable to CS reconstructed images from retrospective undersampled data, and that CS techniques are practical in a preclinical setting. The implementation achieved 2 to 4 times acceleration for image acquisition and satisfactory quality of image reconstruction.

Migration of the digital interactive breast-imaging teaching file

NASA Astrophysics Data System (ADS)

Cao, Fei; Sickles, Edward A.; Huang, H. K.; Zhou, Xiaoqiang

1998-06-01

The digital breast imaging teaching file developed during the last two years in our laboratory has been used successfully at UCSF (University of California, San Francisco) as a routine teaching tool for training radiology residents and fellows in mammography. Building on this success, we have ported the teaching file from an old Pixar imaging/Sun SPARC 470 display system to our newly designed telemammography display workstation (Ultra SPARC 2 platform with two DOME Md5/SBX display boards). The old Pixar/Sun 470 system, although adequate for fast and high-resolution image display, is 4- year-old technology, expensive to maintain and difficult to upgrade. The new display workstation is more cost-effective and is also compatible with the digital image format from a full-field direct digital mammography system. The digital teaching file is built on a sophisticated computer-aided instruction (CAI) model, which simulates the management sequences used in imaging interpretation and work-up. Each user can be prompted to respond by making his/her own observations, assessments, and work-up decisions as well as the marking of image abnormalities. This effectively replaces the traditional 'show-and-tell' teaching file experience with an interactive, response-driven type of instruction.

MR contrast media for myocardial viability, microvascular integrity and perfusion.

PubMed

Saeed, M; Wendland, M F; Watzinger, N; Akbari, H; Higgins, C B

2000-06-01

Cardiovascular imaging requires an appreciation of rapidly evolving MR imaging sequences as well as careful utilization of intravascular, extracellular and intracellular MR contrast media. At the present time, clinical studies are restricted to the use of extracellular MR contrast media. MR imaging has the potential to noninvasively measure multiple parameters of the cardiovascular system in a single imaging session. Recent advances in fast and ultrafast MR imaging have considerably enhanced the capability of this technique, beyond the assessment of left ventricular wall motion and morphology into visualization of the coronary arteries and measurement of blood flow. During the course of the last several years, multiple strategies for imaging viable myocardium have been developed and validated using MR contrast media. Contrast enhanced dynamic MR imaging provides information regarding microvascular integrity and perfusion. Because these information can be provided noninvasively by MR imaging, repeated measurements can be performed in longitudinal studies to monitor the progression or regression of myocardial injury. Similar studies are needed to examine the effects of newly developed cardioprotective therapeutics. Development of suitable intravascular MR contrast medium may be essential for visualization of the coronary arteries and interventional therapies. MR imaging may emerge as one-stop-shop for evaluating the heart and coronary system. This capability will make MR imaging cost-effective in the first decade of this millennium.

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.

Pediatric head and neck lesions: assessment of vascularity by MR digital subtraction angiography.

PubMed

Chooi, Weng Kong; Woodhouse, Neil; Coley, Stuart C; Griffiths, Paul D

2004-08-01

Pediatric head and neck lesions can be difficult to characterize on clinical grounds alone. We investigated the use of dynamic MR digital subtraction angiography as a noninvasive adjunct for the assessment of the vascularity of these abnormalities. Twelve patients (age range, 2 days to 16 years) with known or suspected vascular abnormalities were studied. Routine MR imaging, time-of-flight MR angiography, and MR digital subtraction angiography were performed in all patients. The dynamic sequence was acquired in two planes at one frame per second by using a thick section (6-10 cm) selective radio-frequency spoiled fast gradient-echo sequence and an IV administered bolus of contrast material. The images were subtracted from a preliminary mask sequence and viewed as a video-inverted cine loop. In all cases, MR digital subtraction angiography was successfully performed. The technique showed the following: 1) slow flow lesions (two choroidal angiomas, eyelid hemangioma, and scalp venous malformation); 2) high flow lesions that were not always suspected by clinical examination alone (parotid hemangioma, scalp, occipital, and eyelid arteriovenous malformations plus a palatal teratoma); 3) a hypovascular tumor for which a biopsy could be safely performed (Burkitt lymphoma); and 4) a hypervascular tumor of the palate (cystic teratoma). Our early experience suggests that MR digital subtraction angiography can be reliably performed in children of all ages without complication. The technique provided a noninvasive assessment of the vascularity of each lesion that could not always have been predicted on the basis of clinical examination or routine MR imaging alone.

Breath-hold black-blood T1rho mapping improves liver T1rho quantification in healthy volunteers.

PubMed

Wáng, Yì Xiáng J; Deng, Min; Lo, Gladys G; Liang, Dong; Yuan, Jing; Chen, Weitian

2018-03-01

Background Recent researches suggest that T1rho may be a non-invasive and quantitative technique for detecting and grading liver fibrosis. Purpose To compare a multi-breath-hold bright-blood fast gradient echo (GRE) imaging and a single breath-hold single-shot fast spin echo (FSE) imaging with black-blood effect for liver parenchyma T1rho measurement and to study liver physiological T1rho value in healthy volunteers. Material and Methods The institutional Ethics Committee approved this study. 28 healthy participants (18 men, 10 women; age = 29.6 ± 5.1 years) underwent GRE liver T1rho imaging, and 20 healthy participants (10 men, 10 women; age = 36.9 ± 10.3 years) underwent novel black-blood FSE liver T1rho imaging, both at 3T with spin-lock frequency of 500 Hz. The FSE technique allows simultaneous acquisition of four spin lock times (TSLs; 1 ms, 10 ms, 30 ms, 50msec) in 10 s. Results For FSE technique the intra-scan repeatability intraclass correlation coefficient (ICC) was 0.98; while the inter-scan reproducibility ICC was 0.82 which is better than GRE technique's 0.76. Liver T1rho value in women tended to have a higher value than T1rho values in men (FSE: 42.28 ± 4.06 ms for women and 39.13 ± 2.12 ms for men; GRE: 44.44 ± 1.62 ms for women and 42.36 ± 2.00 ms for men) and FSE technique showed liver T1rho value decreased slightly as age increased. Conclusion Single breath-hold black-blood FSE sequence has better scan-rescan reproducibility than multi-breath-hold bright-blood GRE sequence. Gender and age dependence of liver T1rho in healthy participants is observed, with young women tending to have a higher T1rho measurement.

Distributed file management for remote clinical image-viewing stations

NASA Astrophysics Data System (ADS)

Ligier, Yves; Ratib, Osman M.; Girard, Christian; Logean, Marianne; Trayser, Gerhard

1996-05-01

The Geneva PACS is based on a distributed architecture, with different archive servers used to store all the image files produced by digital imaging modalities. Images can then be visualized on different display stations with the Osiris software. Image visualization require to have the image file physically present on the local station. Thus, images must be transferred from archive servers to local display stations in an acceptable way, which means fast and user friendly where the notion of file must be hidden to users. The transfer of image files is done according to different schemes including prefetching and direct image selection. Prefetching allows the retrieval of previous studies of a patient in advance. A direct image selection is also provided in order to retrieve images on request. When images are transferred locally on the display station, they are stored in Papyrus files, each file containing a set of images. File names are used by the Osiris viewing software to open image sequences. But file names alone are not explicit enough to properly describe the content of the file. A specific utility has been developed to present a list of patients, and for each patient a list of exams which can be selected and automatically displayed. The system has been successfully tested in different clinical environments. It will be soon extended on a hospital wide basis.

Enhanced subject-specific resting-state network detection and extraction with fast fMRI.

PubMed

Akin, Burak; Lee, Hsu-Lei; Hennig, Jürgen; LeVan, Pierre

2017-02-01

Resting-state networks have become an important tool for the study of brain function. An ultra-fast imaging technique that allows to measure brain function, called Magnetic Resonance Encephalography (MREG), achieves an order of magnitude higher temporal resolution than standard echo-planar imaging (EPI). This new sequence helps to correct physiological artifacts and improves the sensitivity of the fMRI analysis. In this study, EPI is compared with MREG in terms of capability to extract resting-state networks. Healthy controls underwent two consecutive resting-state scans, one with EPI and the other with MREG. Subject-level independent component analyses (ICA) were performed separately for each of the two datasets. Using Stanford FIND atlas parcels as network templates, the presence of ICA maps corresponding to each network was quantified in each subject. The number of detected individual networks was significantly higher in the MREG data set than for EPI. Moreover, using short time segments of MREG data, such as 50 seconds, one can still detect and track consistent networks. Fast fMRI thus results in an increased capability to extract distinct functional regions at the individual subject level for the same scan times, and also allow the extraction of consistent networks within shorter time intervals than when using EPI, which is notably relevant for the analysis of dynamic functional connectivity fluctuations. Hum Brain Mapp 38:817-830, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Fast neutron mutants database and web displays at SoyBase

USDA-ARS?s Scientific Manuscript database

SoyBase, the USDA-ARS soybean genetics and genomics database, has been expanded to include data for the fast neutron mutants produced by Bolon, Vance, et al. In addition to the expected text and sequence homology searches and visualization of the indels in the context of the genome sequence viewer, ...

Systematic evaluation of heteronuclear spin decoupling in solid-state NMR at the rotary-resonance conditions in the regime of fast magic-angle spinning

NASA Astrophysics Data System (ADS)

Sharma, Kshama; Madhu, P. K.; Agarwal, Vipin

2016-09-01

The performance of heteronuclear spin decoupling sequences in solid-state NMR severely degrades when the proton radiofrequency (RF) nutation frequencies (ν1) are close to or at multiples of magic-angle spinning (MAS) frequency (νr) that are referred to as rotary-resonance recoupling conditions (ν1 = n · νr). Recently, two schemes, namely, PISSARRO and rCWApA, have been shown to be less affected by the problem of MAS and RF interference, specifically at the n = 2 rotary-resonance recoupling condition, especially in the fast MAS regime. Here, we systematically evaluate the loss in intensity of several heteronuclear spin decoupling sequences at the n = 1, 2 conditions compared to high-power decoupling in the fast-MAS regime. We propose that in the fast-MAS regime (above 40 kHz) the entire discussion about RF and MAS interference can be avoided by using appropriate low-power decoupling sequences which give comparable performance to decoupling sequences with high-power 1H irradiation of ca.195 kHz.

Increased Speed and Image Quality for Pelvic Single-Shot Fast Spin-Echo Imaging with Variable Refocusing Flip Angles and Full-Fourier Acquisition

PubMed Central

Litwiller, Daniel V.; Saranathan, Manojkumar; Vasanawala, Shreyas S.

2017-01-01

Purpose To assess image quality and speed improvements for single-shot fast spin-echo (SSFSE) with variable refocusing flip angles and full-Fourier acquisition (vrfSSFSE) pelvic imaging via a prospective trial performed in the context of uterine leiomyoma evaluation. Materials and Methods Institutional review board approval and informed consent were obtained. vrfSSFSE and conventional SSFSE sagittal and coronal oblique acquisitions were performed in 54 consecutive female patients referred for 3-T magnetic resonance (MR) evaluation of known or suspected uterine leiomyomas. Two radiologists who were blinded to the image acquisition technique semiquantitatively scored images on a scale from −2 to 2 for noise, image contrast, sharpness, artifacts, and perceived ability to evaluate uterine, ovarian, and musculoskeletal structures. The null hypothesis of no significant difference between pulse sequences was assessed with a Wilcoxon signed rank test by using a Holm-Bonferroni correction for multiple comparisons. Results Because of reductions in specific absorption rate, vrfSSFSE imaging demonstrated significantly increased speed (more than twofold, P < .0001), with mean repetition times compared with conventional SSFSE imaging decreasing from 1358 to 613 msec for sagittal acquisitions and from 1494 to 621 msec for coronal oblique acquisitions. Almost all assessed image quality and perceived diagnostic capability parameters were significantly improved with vrfSSFSE imaging. These improvements included noise, sharpness, and ability to evaluate the junctional zone, myometrium, and musculoskeletal structures for both sagittal acquisitions (mean values of 0.56, 0.63, 0.42, 0.56, and 0.80, respectively; all P values < .0001) and coronal oblique acquisitions (mean values of 0.81, 1.09, 0.65, 0.93, and 1.12, respectively; all P values < .0001). For evaluation of artifacts, there was an insufficient number of cases with differences to allow statistical testing. Conclusion Compared with conventional SSFSE acquisition, vrfSSFSE acquisition increases 3-T imaging speed via reduced specific absorption rate and leads to significant improvements in perceived image quality and perceived diagnostic capability when evaluating pelvic structures. © RSNA, 2016 Online supplemental material is available for this article. PMID:27564132

Evaluation of PET and MR datasets in integrated 18F-FDG PET/MRI: A comparison of different MR sequences for whole-body restaging of breast cancer patients.

PubMed

Grueneisen, Johannes; Sawicki, Lino Morris; Wetter, Axel; Kirchner, Julian; Kinner, Sonja; Aktas, Bahriye; Forsting, Michael; Ruhlmann, Verena; Umutlu, Lale

2017-04-01

To investigate the diagnostic value of different MR sequences and 18F-FDG PET data for whole-body restaging of breast cancer patients utilizing PET/MRI. A total of 36 patients with suspected tumor recurrence of breast cancer based on clinical follow-up or abnormal findings in follow-up examinations (e.g. CT, MRI) were prospectively enrolled in this study. All patients underwent a PET/CT and subsequently an additional PET/MR scan. Two readers were instructed to identify the occurrence of a tumor relapse in subsequent MR and PET/MR readings, utilizing different MR sequence constellations for each session. The diagnostic confidence for the determination of a malignant or benign lesion was qualitatively rated (3-point ordinal scale) for each lesion in the different reading sessions and the lesion conspicuity (4-point ordinal scale) for the three different MR sequences was additionally evaluated. Tumor recurrence was present in 25/36 (69%) patients. All three PET/MRI readings showed a significantly higher accuracy as well as higher confidence levels for the detection of recurrent breast cancer lesions when compared to MRI alone (p<0.05). Furthermore, all three PET/MR sequence constellations showed comparable diagnostic accuracy for the identification of a breast cancer recurrence (p>0.05), yet the highest confidence levels were obtained, when all three MR sequences were used for image interpretation. Moreover, contrast-enhanced T1-weighted VIBE imaging showed significantly higher values for the delineation of malignant and benign lesions when compared to T2w HASTE and diffusion-weighted imaging. Integrated PET/MRI provides superior restaging of breast cancer patients over MRI alone. Facing the need for appropriate and efficient whole-body PET/MR protocols, our results show the feasibility of fast and morphologically adequate PET/MR protocols. However, considering an equivalent accuracy for the detection of breast cancer recurrences in the three PET/MR readings, the application of contrast-agent and the inclusion of DWI in the study protocol seems to be debatable. Copyright © 2017 Elsevier B.V. All rights reserved.

Fast H-DROP: A thirty times accelerated version of H-DROP for interactive SVM-based prediction of helical domain linkers

NASA Astrophysics Data System (ADS)

Richa, Tambi; Ide, Soichiro; Suzuki, Ryosuke; Ebina, Teppei; Kuroda, Yutaka

2017-02-01

Efficient and rapid prediction of domain regions from amino acid sequence information alone is often required for swift structural and functional characterization of large multi-domain proteins. Here we introduce Fast H-DROP, a thirty times accelerated version of our previously reported H-DROP (Helical Domain linker pRediction using OPtimal features), which is unique in specifically predicting helical domain linkers (boundaries). Fast H-DROP, analogously to H-DROP, uses optimum features selected from a set of 3000 ones by combining a random forest and a stepwise feature selection protocol. We reduced the computational time from 8.5 min per sequence in H-DROP to 14 s per sequence in Fast H-DROP on an 8 Xeon processor Linux server by using SWISS-PROT instead of Genbank non-redundant (nr) database for generating the PSSMs. The sensitivity and precision of Fast H-DROP assessed by cross-validation were 33.7 and 36.2%, which were merely 2% lower than that of H-DROP. The reduced computational time of Fast H-DROP, without affecting prediction performances, makes it more interactive and user-friendly. Fast H-DROP and H-DROP are freely available from http://domserv.lab.tuat.ac.jp/.

SoFAST: Automated Flare Detection with the PROBA2/SWAP EUV Imager

NASA Astrophysics Data System (ADS)

Bonte, K.; Berghmans, D.; De Groof, A.; Steed, K.; Poedts, S.

2013-08-01

The Sun Watcher with Active Pixels and Image Processing (SWAP) EUV imager onboard PROBA2 provides a non-stop stream of coronal extreme-ultraviolet (EUV) images at a cadence of typically 130 seconds. These images show the solar drivers of space-weather, such as flares and erupting filaments. We have developed a software tool that automatically processes the images and localises and identifies flares. On one hand, the output of this software tool is intended as a service to the Space Weather Segment of ESA's Space Situational Awareness (SSA) program. On the other hand, we consider the PROBA2/SWAP images as a model for the data from the Extreme Ultraviolet Imager (EUI) instrument prepared for the future Solar Orbiter mission, where onboard intelligence is required for prioritising data within the challenging telemetry quota. In this article we present the concept of the software, the first statistics on its effectiveness and the online display in real time of its results. Our results indicate that it is not only possible to detect EUV flares automatically in an acquired dataset, but that quantifying a range of EUV dynamics is also possible. The method is based on thresholding of macropixelled image sequences. The robustness and simplicity of the algorithm is a clear advantage for future onboard use.

Possibility Study of Scale Invariant Feature Transform (SIFT) Algorithm Application to Spine Magnetic Resonance Imaging

PubMed Central

Lee, Dong-Hoon; Lee, Do-Wan; Han, Bong-Soo

2016-01-01

The purpose of this study is an application of scale invariant feature transform (SIFT) algorithm to stitch the cervical-thoracic-lumbar (C-T-L) spine magnetic resonance (MR) images to provide a view of the entire spine in a single image. All MR images were acquired with fast spin echo (FSE) pulse sequence using two MR scanners (1.5 T and 3.0 T). The stitching procedures for each part of spine MR image were performed and implemented on a graphic user interface (GUI) configuration. Moreover, the stitching process is performed in two categories; manual point-to-point (mPTP) selection that performed by user specified corresponding matching points, and automated point-to-point (aPTP) selection that performed by SIFT algorithm. The stitched images using SIFT algorithm showed fine registered results and quantitatively acquired values also indicated little errors compared with commercially mounted stitching algorithm in MRI systems. Our study presented a preliminary validation of the SIFT algorithm application to MRI spine images, and the results indicated that the proposed approach can be performed well for the improvement of diagnosis. We believe that our approach can be helpful for the clinical application and extension of other medical imaging modalities for image stitching. PMID:27064404

Quantum-Sequencing: Fast electronic single DNA molecule sequencing

NASA Astrophysics Data System (ADS)

Casamada Ribot, Josep; Chatterjee, Anushree; Nagpal, Prashant

2014-03-01

A major goal of third-generation sequencing technologies is to develop a fast, reliable, enzyme-free, high-throughput and cost-effective, single-molecule sequencing method. Here, we present the first demonstration of unique ``electronic fingerprint'' of all nucleotides (A, G, T, C), with single-molecule DNA sequencing, using Quantum-tunneling Sequencing (Q-Seq) at room temperature. We show that the electronic state of the nucleobases shift depending on the pH, with most distinct states identified at acidic pH. We also demonstrate identification of single nucleotide modifications (methylation here). Using these unique electronic fingerprints (or tunneling data), we report a partial sequence of beta lactamase (bla) gene, which encodes resistance to beta-lactam antibiotics, with over 95% success rate. These results highlight the potential of Q-Seq as a robust technique for next-generation sequencing.

Time-of-flight magnetic resonance angiography imaging of a residual arteriovenous malformation nidus after Onyx embolization for stereotactic radiosurgery planning. Technical note.

PubMed

Loy, David N; Rich, Keith M; Simpson, Joseph; Dorward, Ian; Santanam, Lakshmi; Derdeyn, Colin P

2009-05-01

This report demonstrates that time-of-flight (TOF) MR angiography is a useful adjunct for planning stereotactic radiosurgery (SRS) of large arteriovenous malformations (AVMs) after staged embolization with Onyx. Onyx (ethylene vinyl copolymer), a recently approved liquid embolic agent, has been increasingly used to exclude portions of large AVMs from the parent circulation prior to SRS. Limiting SRS to regions of persistent arteriovenous shunting and excluding regions eliminated by embolization may reduce unnecessary radiation doses to eloquent brain structures. However, SRS dosimetry planning presents unique challenges after Onyx embolization because it creates extensive artifacts on CT scans, and it cannot be delineated from untreated nidus on standard MR sequences. During the radiosurgery procedure, MR images were obtained using a GE Signa 1.5-T unit. Standard axial T2 fast spin echo high-resolution images (TR 3000 msec, TE 108 msec, slice thickness 2.5 mm) were generated for optimal visualization of brain tissue and AVM flow voids. The 3D TOF MR angiography images of the circle of Willis and vertebral arteries were subsequently obtained to visualize AVM regions embolized with Onyx (TR 37 msec, TE 6.9 msec, flip angle 20 degrees). Adjunct TOF MR angiography images demonstrated excellent contrast between nidus embolized with Onyx and regions of persistent arteriovenous shunting within a large AVM prior to SRS. Additional information derived from these sequences resulted in substantial adjustments to the treatment plan and an overall reduction in the treated tissue volume.

The development and optimisation of 3D black-blood R2* mapping of the carotid artery wall.

PubMed

Yuan, Jianmin; Graves, Martin J; Patterson, Andrew J; Priest, Andrew N; Ruetten, Pascal P R; Usman, Ammara; Gillard, Jonathan H

2017-12-01

To develop and optimise a 3D black-blood R 2 * mapping sequence for imaging the carotid artery wall, using optimal blood suppression and k-space view ordering. Two different blood suppression preparation methods were used; Delay Alternating with Nutation for Tailored Excitation (DANTE) and improved Motion Sensitive Driven Equilibrium (iMSDE) were each combined with a three-dimensional (3D) multi-echo Fast Spoiled GRadient echo (ME-FSPGR) readout. Three different k-space view-order designs: Radial Fan-beam Encoding Ordering (RFEO), Distance-Determined Encoding Ordering (DDEO) and Centric Phase Encoding Order (CPEO) were investigated. The sequences were evaluated through Bloch simulation and in a cohort of twenty volunteers. The vessel wall Signal-to-Noise Ratio (SNR), Contrast-to-Noise Ratio (CNR) and R 2 *, and the sternocleidomastoid muscle R 2 * were measured and compared. Different numbers of acquisitions-per-shot (APS) were evaluated to further optimise the effectiveness of blood suppression. All sequences resulted in comparable R 2 * measurements to a conventional, i.e. non-blood suppressed sequence in the sternocleidomastoid muscle of the volunteers. Both Bloch simulations and volunteer data showed that DANTE has a higher signal intensity and results in a higher image SNR than iMSDE. Blood suppression efficiency was not significantly different when using different k-space view orders. Smaller APS achieved better blood suppression. The use of blood-suppression preparation methods does not affect the measurement of R 2 *. DANTE prepared ME-FSPGR sequence with a small number of acquisitions-per-shot can provide high quality black-blood R 2 * measurements of the carotid vessel wall. Copyright © 2017 Elsevier Inc. All rights reserved.

A new strategy for fast radiofrequency CW EPR imaging: Direct detection with rapid scan and rotating gradients

PubMed Central

Subramanian, Sankaran; Koscielniak, Janusz W.; Devasahayam, Nallathamby; Pursley, Randall H.; Pohida, Thomas J.; Krishna, Murali C.

2007-01-01

Rapid field scan on the order of T/s using high frequency sinusoidal or triangular sweep fields superimposed on the main Zeeman field, was used for direct detection of signals without low-frequency field modulation. Simultaneous application of space-encoding rotating field gradients have been employed to perform fast CW EPR imaging using direct detection that could, in principle, approach the speed of pulsed FT EPR imaging. The method takes advantage of the well-known rapid-scan strategy in CW NMR and EPR that allows arbitrarily fast field sweep and the simultaneous application of spinning gradients that allows fast spatial encoding. This leads to fast functional EPR imaging and, depending on the spin concentration, spectrometer sensitivity and detection band width, can provide improved temporal resolution that is important to interrogate dynamics of spin perfusion, pharmacokinetics, spectral spatial imaging, dynamic oxymetry, etc. PMID:17350865

Diagnostic performance of dark-blood T2-weighted CMR for evaluation of acute myocardial injury.

PubMed

Srichai, Monvadi B; Lim, Ruth P; Lath, Narayan; Babb, James; Axel, Leon; Kim, Daniel

2013-01-01

We compared the image quality and diagnostic performance of 2 fat-suppression methods for black-blood T2-weighted fast spin-echo (FSE), which are as follows: (a) short T1 inversion recovery (STIR; FSE-STIR) and (b) spectral adiabatic inversion recovery (SPAIR; FSE-SPAIR), for detection of acute myocardial injury. Edema-sensitive T2-weighted FSE cardiac magnetic resonance (CMR) imaging is useful in detecting acute myocardial injury but may experience reduced myocardial signal and signal dropout. The SPAIR pulse aims to eliminate artifacts associated with the STIR pulse. A total of 65 consecutive patients referred for CMR evaluation of myocardial structure and function underwent FSE-STIR and FSE-SPAIR, in addition to cine and late gadolinium enhancement (LGE) CMR. T2-weighted FSE images were independently evaluated by 2 readers for image quality and artifacts (Likert scale of 1-5; best-worst) and presence of increased myocardial signal suggestive of edema. In addition, clinical CMR interpretation, incorporating all CMR sequences available, was recorded for comparison. Diagnostic performance of each T2-weighted sequence was measured using recent (<30 days) troponin elevation greater than 2 times the upper limit of normal as the reference standard for acute myocardial injury. Of the 65 patients, there were 21 (32%) with acute myocardial injury. Image quality and artifact scores were significantly better with FSE-SPAIR compared with FSE-STIR (2.15 vs 2.68, P < 0.01; 2.62 vs 3.05, P < 0.01, respectively). The sensitivity, specificity, positive predictive value, and negative predictive value for acute myocardial injury were as follows: 29%, 93%, 67%, and 73% for FSE-SPAIR; 38%, 91%, 67%, and 75% for FSE-STIR; 71%, 98%, 94%, and 88% for clinical interpretation including LGE, T2, and wall motion. There was a statistically significant difference in sensitivity between the clinical interpretation and each of the T2-weighted sequences but not between each T2-weighted sequence. Although FSE-SPAIR demonstrated significantly improved image quality and decreased artifacts, isolated interpretations of each T2-weighted technique demonstrated high specificity but overall low sensitivity for the detection of myocardial injury, with no difference in accuracy between the techniques. However, real-world interpretation in combination with cine and LGE CMR methods significantly improves the overall sensitivity and diagnostic performance.

Accurate and simple method for quantification of hepatic fat content using magnetic resonance imaging: a prospective study in biopsy-proven nonalcoholic fatty liver disease.

PubMed

Hatta, Tomoko; Fujinaga, Yasunari; Kadoya, Masumi; Ueda, Hitoshi; Murayama, Hiroaki; Kurozumi, Masahiro; Ueda, Kazuhiko; Komatsu, Michiharu; Nagaya, Tadanobu; Joshita, Satoru; Kodama, Ryo; Tanaka, Eiji; Uehara, Tsuyoshi; Sano, Kenji; Tanaka, Naoki

2010-12-01

To assess the degree of hepatic fat content, simple and noninvasive methods with high objectivity and reproducibility are required. Magnetic resonance imaging (MRI) is one such candidate, although its accuracy remains unclear. We aimed to validate an MRI method for quantifying hepatic fat content by calibrating MRI reading with a phantom and comparing MRI measurements in human subjects with estimates of liver fat content in liver biopsy specimens. The MRI method was performed by a combination of MRI calibration using a phantom and double-echo chemical shift gradient-echo sequence (double-echo fast low-angle shot sequence) that has been widely used on a 1.5-T scanner. Liver fat content in patients with nonalcoholic fatty liver disease (NAFLD, n = 26) was derived from a calibration curve generated by scanning the phantom. Liver fat was also estimated by optical image analysis. The correlation between the MRI measurements and liver histology findings was examined prospectively. Magnetic resonance imaging measurements showed a strong correlation with liver fat content estimated from the results of light microscopic examination (correlation coefficient 0.91, P < 0.001) regardless of the degree of hepatic steatosis. Moreover, the severity of lobular inflammation or fibrosis did not influence the MRI measurements. This MRI method is simple and noninvasive, has excellent ability to quantify hepatic fat content even in NAFLD patients with mild steatosis or advanced fibrosis, and can be performed easily without special devices.

Optimizing T2-weighted magnetic resonance sequences for surface coil microimaging of the eye with regard to lid, eyeball and head moving artifacts.

PubMed

Obata, Takayuki; Uemura, Koji; Nonaka, Hiroi; Tamura, Mitsuru; Tanada, Shuji; Ikehira, Hiroo

2006-01-01

To acquire high-resolution magnetic resonance (MR) images, we developed a new blinking artifact reduced pulse (BARP) sequence with a surface coil specialized for microscopic imaging (47 mm in diameter). To reduce eye movement, we ascertained that the subjects' eyes were kept open and fixated to the target in the 1.5-T MR gantry. To reduce motion artifacts from blinking, we inserted rest periods for blinking (1.5 s within every 5 s) during MR scanning (T2-weighted fast spin echo; repetition time, 5 s; echo time, 100 ms; echo train, 11; matrix, 256 x 128; field of view, 5 cm; 1-mm thickness x 30 slices). Three scans (100 s x 3) were performed for each normal subject, and they were added together after automatic adjustment for location to reduce quality loss caused by head motion. T2-weighted MR images were acquired with a high resolution and a high signal-to-noise ratio. Motion artifacts were reduced with BARP, as compared with those with random blinking. Intraocular structures such as the iris and ciliary muscles were clearly visualized. Because the whole eye can be covered with a 1-mm thickness by this method, three-dimensional maps can easily be generated from the obtained images. The application of BARP with a surface coil of the human eye might become a useful and widely adopted procedure for MR microimaging.

Heterogeneity image patch index and its application to consumer video summarization.

PubMed

Dang, Chinh T; Radha, Hayder

2014-06-01

Automatic video summarization is indispensable for fast browsing and efficient management of large video libraries. In this paper, we introduce an image feature that we refer to as heterogeneity image patch (HIP) index. The proposed HIP index provides a new entropy-based measure of the heterogeneity of patches within any picture. By evaluating this index for every frame in a video sequence, we generate a HIP curve for that sequence. We exploit the HIP curve in solving two categories of video summarization applications: key frame extraction and dynamic video skimming. Under the key frame extraction frame-work, a set of candidate key frames is selected from abundant video frames based on the HIP curve. Then, a proposed patch-based image dissimilarity measure is used to create affinity matrix of these candidates. Finally, a set of key frames is extracted from the affinity matrix using a min–max based algorithm. Under video skimming, we propose a method to measure the distance between a video and its skimmed representation. The video skimming problem is then mapped into an optimization framework and solved by minimizing a HIP-based distance for a set of extracted excerpts. The HIP framework is pixel-based and does not require semantic information or complex camera motion estimation. Our simulation results are based on experiments performed on consumer videos and are compared with state-of-the-art methods. It is shown that the HIP approach outperforms other leading methods, while maintaining low complexity.

Direct magnetic field estimation based on echo planar raw data.

PubMed

Testud, Frederik; Splitthoff, Daniel Nicolas; Speck, Oliver; Hennig, Jürgen; Zaitsev, Maxim

2010-07-01

Gradient recalled echo echo planar imaging is widely used in functional magnetic resonance imaging. The fast data acquisition is, however, very sensitive to field inhomogeneities which manifest themselves as artifacts in the images. Typically used correction methods have the common deficit that the data for the correction are acquired only once at the beginning of the experiment, assuming the field inhomogeneity distribution B(0) does not change over the course of the experiment. In this paper, methods to extract the magnetic field distribution from the acquired k-space data or from the reconstructed phase image of a gradient echo planar sequence are compared and extended. A common derivation for the presented approaches provides a solid theoretical basis, enables a fair comparison and demonstrates the equivalence of the k-space and the image phase based approaches. The image phase analysis is extended here to calculate the local gradient in the readout direction and improvements are introduced to the echo shift analysis, referred to here as "k-space filtering analysis." The described methods are compared to experimentally acquired B(0) maps in phantoms and in vivo. The k-space filtering analysis presented in this work demonstrated to be the most sensitive method to detect field inhomogeneities.

Frequency tagging to track the neural processing of contrast in fast, continuous sound sequences.

PubMed

Nozaradan, Sylvie; Mouraux, André; Cousineau, Marion

2017-07-01

The human auditory system presents a remarkable ability to detect rapid changes in fast, continuous acoustic sequences, as best illustrated in speech and music. However, the neural processing of rapid auditory contrast remains largely unclear, probably due to the lack of methods to objectively dissociate the response components specifically related to the contrast from the other components in response to the sequence of fast continuous sounds. To overcome this issue, we tested a novel use of the frequency-tagging approach allowing contrast-specific neural responses to be tracked based on their expected frequencies. The EEG was recorded while participants listened to 40-s sequences of sounds presented at 8Hz. A tone or interaural time contrast was embedded every fifth sound (AAAAB), such that a response observed in the EEG at exactly 8 Hz/5 (1.6 Hz) or harmonics should be the signature of contrast processing by neural populations. Contrast-related responses were successfully identified, even in the case of very fine contrasts. Moreover, analysis of the time course of the responses revealed a stable amplitude over repetitions of the AAAAB patterns in the sequence, except for the response to perceptually salient contrasts that showed a buildup and decay across repetitions of the sounds. Overall, this new combination of frequency-tagging with an oddball design provides a valuable complement to the classic, transient, evoked potentials approach, especially in the context of rapid auditory information. Specifically, we provide objective evidence on the neural processing of contrast embedded in fast, continuous sound sequences. NEW & NOTEWORTHY Recent theories suggest that the basis of neurodevelopmental auditory disorders such as dyslexia might be an impaired processing of fast auditory changes, highlighting how the encoding of rapid acoustic information is critical for auditory communication. Here, we present a novel electrophysiological approach to capture in humans neural markers of contrasts in fast continuous tone sequences. Contrast-specific responses were successfully identified, even for very fine contrasts, providing direct insight on the encoding of rapid auditory information. Copyright © 2017 the American Physiological Society.

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.

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.

Magnetic Particle Imaging (MPI) for NMR and MRI researchers

NASA Astrophysics Data System (ADS)

Saritas, Emine U.; Goodwill, Patrick W.; Croft, Laura R.; Konkle, Justin J.; Lu, Kuan; Zheng, Bo; Conolly, Steven M.

2013-04-01

Magnetic Particle Imaging (MPI) is a new tracer imaging modality that is gaining significant interest from NMR and MRI researchers. While the physics of MPI differ substantially from MRI, it employs hardware and imaging concepts that are familiar to MRI researchers, such as magnetic excitation and detection, pulse sequences, and relaxation effects. Furthermore, MPI employs the same superparamagnetic iron oxide (SPIO) contrast agents that are sometimes used for MR angiography and are often used for MRI cell tracking studies. These SPIOs are much safer for humans than iodine or gadolinium, especially for Chronic Kidney Disease (CKD) patients. The weak kidneys of CKD patients cannot safely excrete iodine or gadolinium, leading to increased morbidity and mortality after iodinated X-ray or CT angiograms, or after gadolinium-MRA studies. Iron oxides, on the other hand, are processed in the liver, and have been shown to be safe even for CKD patients. Unlike the “black blood” contrast generated by SPIOs in MRI due to increased T2∗ dephasing, SPIOs in MPI generate positive, “bright blood” contrast. With this ideal contrast, even prototype MPI scanners can already achieve fast, high-sensitivity, and high-contrast angiograms with millimeter-scale resolutions in phantoms and in animals. Moreover, MPI shows great potential for an exciting array of applications, including stem cell tracking in vivo, first-pass contrast studies to diagnose or stage cancer, and inflammation imaging in vivo. So far, only a handful of prototype small-animal MPI scanners have been constructed worldwide. Hence, MPI is open to great advances, especially in hardware, pulse sequence, and nanoparticle improvements, with the potential to revolutionize the biomedical imaging field.

Fast Simulation of Dynamic Ultrasound Images Using the GPU.

PubMed

Storve, Sigurd; Torp, Hans

2017-10-01

Simulated ultrasound data is a valuable tool for development and validation of quantitative image analysis methods in echocardiography. Unfortunately, simulation time can become prohibitive for phantoms consisting of a large number of point scatterers. The COLE algorithm by Gao et al. is a fast convolution-based simulator that trades simulation accuracy for improved speed. We present highly efficient parallelized CPU and GPU implementations of the COLE algorithm with an emphasis on dynamic simulations involving moving point scatterers. We argue that it is crucial to minimize the amount of data transfers from the CPU to achieve good performance on the GPU. We achieve this by storing the complete trajectories of the dynamic point scatterers as spline curves in the GPU memory. This leads to good efficiency when simulating sequences consisting of a large number of frames, such as B-mode and tissue Doppler data for a full cardiac cycle. In addition, we propose a phase-based subsample delay technique that efficiently eliminates flickering artifacts seen in B-mode sequences when COLE is used without enough temporal oversampling. To assess the performance, we used a laptop computer and a desktop computer, each equipped with a multicore Intel CPU and an NVIDIA GPU. Running the simulator on a high-end TITAN X GPU, we observed two orders of magnitude speedup compared to the parallel CPU version, three orders of magnitude speedup compared to simulation times reported by Gao et al. in their paper on COLE, and a speedup of 27000 times compared to the multithreaded version of Field II, using numbers reported in a paper by Jensen. We hope that by releasing the simulator as an open-source project we will encourage its use and further development.

111In-labeled lactam bridge-cyclized alpha-melanocyte stimulating hormone peptide analogues for melanoma imaging.

PubMed

Miao, Yubin; Gallazzi, Fabio; Guo, Haixun; Quinn, Thomas P

2008-02-01

The purpose of this study was to examine the influence of the lactam bridge cyclization on melanoma targeting and biodistribution properties of the radiolabeled conjugates. Two novel lactam bridge-cyclized alpha-MSH peptide analogues, DOTA-CycMSH (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-c[Lys-Nle-Glu-His-DPhe-Arg-Trp-Gly-Arg-Pro-Val-Asp]) and DOTA-GlyGlu-CycMSH (DOTA-Gly-Glu-c[Lys-Nle-Glu-His-DPhe-Arg-Trp-Gly-Arg-Pro-Val-Asp]), were synthesized and radiolabeled with (111)In. The internalization and efflux of (111)In-labeled CycMSH peptides were examined in B16/F1 melanoma cells. The melanoma targeting properties, pharmacokinetics, and SPECT/CT imaging of (111)In-labeled CycMSH peptides were determined in B16/F1 melanoma-bearing C57 mice. Both (111)In-DOTA-CycMSH and (111)In-DOTA-GlyGlu-CycMSH exhibited fast internalization and extended retention in B16/F1 cells. The tumor uptake values of (111)In-DOTA-CycMSH and (111)In-DOTA-GlyGlu-CycMSH were 9.53+/-1.41% injected dose/gram (% ID/g) and 10.40+/-1.40% ID/g at 2 h postinjection, respectively. Flank melanoma tumors were clearly visualized with (111)In-DOTA-CycMSH and (111)In-DOTA-GlyGlu-CycMSH by SPECT/CT images at 2 h postinjection. Whole-body clearance of the peptides was fast, with greater than 90% of the radioactivities cleared through urinary system by 2 h postinjection. There was low radioactivity (<0.8% ID/g) accumulated in blood and normal organs except kidneys at all time points investigated. Introduction of a negatively charged linker (-Gly-Glu-) into the peptide sequence decreased the renal uptake by 44% without affecting the tumor uptake at 4 h postinjection. High receptor-mediated melanoma uptakes coupled with fast whole-body clearance in B16/F1 melanoma-bearing C57 mice demonstrated the feasibility of using (111)In-labeled lactam bridge-cyclized alpha-MSH peptide analogues as a novel class of imaging probes for receptor-targeting melanoma imaging.

Development of a Large Field of View Shadowgraph System for a 16 Ft. Transonic Wind Tunnel

NASA Technical Reports Server (NTRS)

Talley, Michael A.; Jones, Stephen B.; Goodman, Wesley L.

2000-01-01

A large field of view shadowgraph flow visualization system for the Langley 16 ft. Transonic Tunnel (16 ft.TT) has been developed to provide fast, low cost, aerodynamic design concept evaluation capability to support the development of the next generation of commercial and military aircraft and space launch vehicles. Key features of the 16 ft. TT shadowgraph system are: (1) high resolution (1280 X 1024) digital snap shots and sequences; (2) video recording of shadowgraph at 30 frames per second; (3) pan, tilt, & zoom to find and observe flow features; (4) one microsecond flash for freeze frame images; (5) large field of view approximately 12 X 6 ft; and (6) a low maintenance, high signal/noise ratio, retro-reflective screen to allow shadowgraph imaging while test section lights are on.

Pretargeted Molecular Imaging and Radioimmunotherapy

PubMed Central

Goldenberg, David M.; Chang, Chien-Hsing; Rossi, Edmund A.; J, William; McBride; Sharkey, Robert M.

2012-01-01

Pretargeting is a multi-step process that first has an unlabeled bispecific antibody (bsMAb) localize within a tumor by virtue of its anti-tumor binding site(s) before administering a small, fast-clearing radiolabeled compound that then attaches to the other portion of the bsMAb. The compound's rapid clearance significantly reduces radiation exposure outside of the tumor and its small size permits speedy delivery to the tumor, creating excellent tumor/nontumor ratios in less than 1 hour. Haptens that bind to an anti-hapten antibody, biotin that binds to streptavidin, or an oligonucleotide binding to a complementary oligonucleotide sequence have all been radiolabeled for use by pretargeting. This review will focus on a highly flexible anti-hapten bsMAb platform that has been used to target a variety of radionuclides to image (SPECT and PET) as well as treat tumors. PMID:22737190

Independent motion detection with a rival penalized adaptive particle filter

NASA Astrophysics Data System (ADS)

Becker, Stefan; Hübner, Wolfgang; Arens, Michael

2014-10-01

Aggregation of pixel based motion detection into regions of interest, which include views of single moving objects in a scene is an essential pre-processing step in many vision systems. Motion events of this type provide significant information about the object type or build the basis for action recognition. Further, motion is an essential saliency measure, which is able to effectively support high level image analysis. When applied to static cameras, background subtraction methods achieve good results. On the other hand, motion aggregation on freely moving cameras is still a widely unsolved problem. The image flow, measured on a freely moving camera is the result from two major motion types. First the ego-motion of the camera and second object motion, that is independent from the camera motion. When capturing a scene with a camera these two motion types are adverse blended together. In this paper, we propose an approach to detect multiple moving objects from a mobile monocular camera system in an outdoor environment. The overall processing pipeline consists of a fast ego-motion compensation algorithm in the preprocessing stage. Real-time performance is achieved by using a sparse optical flow algorithm as an initial processing stage and a densely applied probabilistic filter in the post-processing stage. Thereby, we follow the idea proposed by Jung and Sukhatme. Normalized intensity differences originating from a sequence of ego-motion compensated difference images represent the probability of moving objects. Noise and registration artefacts are filtered out, using a Bayesian formulation. The resulting a posteriori distribution is located on image regions, showing strong amplitudes in the difference image which are in accordance with the motion prediction. In order to effectively estimate the a posteriori distribution, a particle filter is used. In addition to the fast ego-motion compensation, the main contribution of this paper is the design of the probabilistic filter for real-time detection and tracking of independently moving objects. The proposed approach introduces a competition scheme between particles in order to ensure an improved multi-modality. Further, the filter design helps to generate a particle distribution which is homogenous even in the presence of multiple targets showing non-rigid motion patterns. The effectiveness of the method is shown on exemplary outdoor sequences.

Automatic pose correction for image-guided nonhuman primate brain surgery planning

NASA Astrophysics Data System (ADS)

Ghafurian, Soheil; Chen, Antong; Hines, Catherine; Dogdas, Belma; Bone, Ashleigh; Lodge, Kenneth; O'Malley, Stacey; Winkelmann, Christopher T.; Bagchi, Ansuman; Lubbers, Laura S.; Uslaner, Jason M.; Johnson, Colena; Renger, John; Zariwala, Hatim A.

2016-03-01

Intracranial delivery of recombinant DNA and neurochemical analysis in nonhuman primate (NHP) requires precise targeting of various brain structures via imaging derived coordinates in stereotactic surgeries. To attain targeting precision, the surgical planning needs to be done on preoperative three dimensional (3D) CT and/or MR images, in which the animals head is fixed in a pose identical to the pose during the stereotactic surgery. The matching of the image to the pose in the stereotactic frame can be done manually by detecting key anatomical landmarks on the 3D MR and CT images such as ear canal and ear bar zero position. This is not only time intensive but also prone to error due to the varying initial poses in the images which affects both the landmark detection and rotation estimation. We have introduced a fast, reproducible, and semi-automatic method to detect the stereotactic coordinate system in the image and correct the pose. The method begins with a rigid registration of the subject images to an atlas and proceeds to detect the anatomical landmarks through a sequence of optimization, deformable and multimodal registration algorithms. The results showed similar precision (maximum difference of 1.71 in average in-plane rotation) to a manual pose correction.

New Techniques for High-contrast Imaging with ADI: The ACORNS-ADI SEEDS Data Reduction Pipeline

NASA Astrophysics Data System (ADS)

Brandt, Timothy D.; McElwain, Michael W.; Turner, Edwin L.; Abe, L.; Brandner, W.; Carson, J.; Egner, S.; Feldt, M.; Golota, T.; Goto, M.; Grady, C. A.; Guyon, O.; Hashimoto, J.; Hayano, Y.; Hayashi, M.; Hayashi, S.; Henning, T.; Hodapp, K. W.; Ishii, M.; Iye, M.; Janson, M.; Kandori, R.; Knapp, G. R.; Kudo, T.; Kusakabe, N.; Kuzuhara, M.; Kwon, J.; Matsuo, T.; Miyama, S.; Morino, J.-I.; Moro-Martín, A.; Nishimura, T.; Pyo, T.-S.; Serabyn, E.; Suto, H.; Suzuki, R.; Takami, M.; Takato, N.; Terada, H.; Thalmann, C.; Tomono, D.; Watanabe, M.; Wisniewski, J. P.; Yamada, T.; Takami, H.; Usuda, T.; Tamura, M.

2013-02-01

We describe Algorithms for Calibration, Optimized Registration, and Nulling the Star in Angular Differential Imaging (ACORNS-ADI), a new, parallelized software package to reduce high-contrast imaging data, and its application to data from the SEEDS survey. We implement several new algorithms, including a method to register saturated images, a trimmed mean for combining an image sequence that reduces noise by up to ~20%, and a robust and computationally fast method to compute the sensitivity of a high-contrast observation everywhere on the field of view without introducing artificial sources. We also include a description of image processing steps to remove electronic artifacts specific to Hawaii2-RG detectors like the one used for SEEDS, and a detailed analysis of the Locally Optimized Combination of Images (LOCI) algorithm commonly used to reduce high-contrast imaging data. ACORNS-ADI is written in python. It is efficient and open-source, and includes several optional features which may improve performance on data from other instruments. ACORNS-ADI requires minimal modification to reduce data from instruments other than HiCIAO. It is freely available for download at www.github.com/t-brandt/acorns-adi under a Berkeley Software Distribution (BSD) license. Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Extraction of Blebs in Human Embryonic Stem Cell Videos.

PubMed

Guan, Benjamin X; Bhanu, Bir; Talbot, Prue; Weng, Nikki Jo-Hao

2016-01-01

Blebbing is an important biological indicator in determining the health of human embryonic stem cells (hESC). Especially, areas of a bleb sequence in a video are often used to distinguish two cell blebbing behaviors in hESC: dynamic and apoptotic blebbings. This paper analyzes various segmentation methods for bleb extraction in hESC videos and introduces a bio-inspired score function to improve the performance in bleb extraction. Full bleb formation consists of bleb expansion and retraction. Blebs change their size and image properties dynamically in both processes and between frames. Therefore, adaptive parameters are needed for each segmentation method. A score function derived from the change of bleb area and orientation between consecutive frames is proposed which provides adaptive parameters for bleb extraction in videos. In comparison to manual analysis, the proposed method provides an automated fast and accurate approach for bleb sequence extraction.

Accelerated radiation damping for increased spin equilibrium (ARISE): a new method for controlling the recovery of longitudinal magnetization.

PubMed

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

2008-11-01

Control of the longitudinal magnetization in fast gradient-echo (GRE) sequences is an important factor in 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 T(1) relaxation. The method is characterized in GRE 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 (10 ms) during a refocused interval of a crushed GRE sequence allowed greater than 99% recovery of the longitudinal magnetization when very little T(2) relaxation had time to occur. An appropriate application might be to improve 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 GRE sequences.

Thermal imaging for cold air flow visualisation and analysis

NASA Astrophysics Data System (ADS)

Grudzielanek, M.; Pflitsch, A.; Cermak, J.

2012-04-01

In this work we present first applications of a thermal imaging system for animated visualization and analysis of cold air flow in field studies. The development of mobile thermal imaging systems advanced very fast in the last decades. The surface temperature of objects, which is detected with long-wave infrared radiation, affords conclusions in different problems of research. Modern thermal imaging systems allow infrared picture-sequences and a following data analysis; the systems are not exclusive imaging methods like in the past. Thus, the monitoring and analysing of dynamic processes became possible. We measured the cold air flow on a sloping grassland area with standard methods (sonic anemometers and temperature loggers) plus a thermal imaging system measuring in the range from 7.5 to 14µm. To analyse the cold air with the thermal measurements, we collected the surface infrared temperatures at a projection screen, which was located in cold air flow direction, opposite the infrared (IR) camera. The intention of using a thermal imaging system for our work was: 1. to get a general idea of practicability in our problem, 2. to assess the value of the extensive and more detailed data sets and 3. to optimise visualisation. The results were very promising. Through the possibility of generating time-lapse movies of the image sequences in time scaling, processes of cold air flow, like flow waves, turbulence and general flow speed, can be directly identified. Vertical temperature gradients and near-ground inversions can be visualised very well. Time-lapse movies will be presented. The extensive data collection permits a higher spatial resolution of the data than standard methods, so that cold air flow attributes can be explored in much more detail. Time series are extracted from the IR data series, analysed statistically, and compared to data obtained using traditional systems. Finally, we assess the usefulness of the additional measurement of cold air flow with thermal imaging systems.

An algorithm for extraction of periodic signals from sparse, irregularly sampled data

NASA Technical Reports Server (NTRS)

Wilcox, J. Z.

1994-01-01

Temporal gaps in discrete sampling sequences produce spurious Fourier components at the intermodulation frequencies of an oscillatory signal and the temporal gaps, thus significantly complicating spectral analysis of such sparsely sampled data. A new fast Fourier transform (FFT)-based algorithm has been developed, suitable for spectral analysis of sparsely sampled data with a relatively small number of oscillatory components buried in background noise. The algorithm's principal idea has its origin in the so-called 'clean' algorithm used to sharpen images of scenes corrupted by atmospheric and sensor aperture effects. It identifies as the signal's 'true' frequency that oscillatory component which, when passed through the same sampling sequence as the original data, produces a Fourier image that is the best match to the original Fourier space. The algorithm has generally met with succession trials with simulated data with a low signal-to-noise ratio, including those of a type similar to hourly residuals for Earth orientation parameters extracted from VLBI data. For eight oscillatory components in the diurnal and semidiurnal bands, all components with an amplitude-noise ratio greater than 0.2 were successfully extracted for all sequences and duty cycles (greater than 0.1) tested; the amplitude-noise ratios of the extracted signals were as low as 0.05 for high duty cycles and long sampling sequences. When, in addition to these high frequencies, strong low-frequency components are present in the data, the low-frequency components are generally eliminated first, by employing a version of the algorithm that searches for non-integer multiples of the discrete FET minimum frequency.

Determination of mouse skeletal muscle architecture using three-dimensional diffusion tensor imaging.

PubMed

Heemskerk, Anneriet M; Strijkers, Gustav J; Vilanova, Anna; Drost, Maarten R; Nicolay, Klaas

2005-06-01

Muscle architecture is the main determinant of the mechanical behavior of skeletal muscles. This study explored the feasibility of diffusion tensor imaging (DTI) and fiber tracking to noninvasively determine the in vivo three-dimensional (3D) architecture of skeletal muscle in mouse hind leg. In six mice, the hindlimb was imaged with a diffusion-weighted (DW) 3D fast spin-echo (FSE) sequence followed by the acquisition of an exercise-induced, T(2)-enhanced data set. The data showed the expected fiber organization, from which the physiological cross-sectional area (PCSA), fiber length, and pennation angle for the tibialis anterior (TA) were obtained. The values of these parameters ranged from 5.4-9.1 mm(2), 5.8-7.8 mm, and 21-24 degrees , respectively, which is in agreement with values obtained previously with the use of invasive methods. This study shows that 3D DT acquisition and fiber tracking is feasible for the skeletal muscle of mice, and thus enables the quantitative determination of muscle architecture.

Design and theoretical investigation of a digital x-ray detector with large area and high spatial resolution

NASA Astrophysics Data System (ADS)

Gui, Jianbao; Guo, Jinchuan; Yang, Qinlao; Liu, Xin; Niu, Hanben

2007-05-01

X-ray phase contrast imaging is a promising new technology today, but the requirements of a digital detector with large area, high spatial resolution and high sensitivity bring forward a large challenge to researchers. This paper is related to the design and theoretical investigation of an x-ray direct conversion digital detector based on mercuric iodide photoconductive layer with the latent charge image readout by photoinduced discharge (PID). Mercuric iodide has been verified having a good imaging performance (high sensitivity, low dark current, low voltage operation and good lag characteristics) compared with the other competitive materials (α-Se,PbI II,CdTe,CdZnTe) and can be easily deposited on large substrates in the manner of polycrystalline. By use of line scanning laser beam and parallel multi-electrode readout make the system have high spatial resolution and fast readout speed suitable for instant general radiography and even rapid sequence radiography.

Minor head injury in children.

PubMed

Klig, Jean E; Kaplan, Carl P

2010-06-01

This review will examine mild closed head injury (CHI) and the current evidence on head computed tomography (CT) imaging risks in children, prediction rules to guide decisions on CT scan use, and issues of concussion after initial evaluation. The current literature offers preliminary evidence on the risks of radiation exposure from CT scans in children. A recent study introduces a validated prediction rule for use in mild CHI, to limit the number of CT scans performed. Concurrent with this progress, fast (or short sequence) MRI represents an emerging technology that may prove to be a viable alternative to CT scan use in certain cases of mild CHI where imaging is desired. The initial emergency department evaluation for mild CHI is the start point for a sequence of follow-up to assure that postconcussive symptoms fully resolve. The literature on sports-related concussion offers some information that may be used for patients with non-sports-related concussion. It is clear that CT scan use should be as safe and limited in scope as possible for children. Common decisions on the use of CT imaging for mild head injury can now be guided by a prediction rule for clinically important traumatic brain injury. Parameters for the follow-up care of patients with mild CHI after emergency department discharge are needed in the future to assure that postconcussive symptoms are adequately screened for full resolution.

Wireless Mobile Technology to Improve Workflow and Feasibility of MR-Guided Percutaneous Interventions

PubMed Central

Rube, Martin A.; Holbrook, Andrew B.; Cox, Benjamin F.; Buciuc, Razvan; Melzer, Andreas

2015-01-01

Purpose A wireless interactive display and control device combined with a platform-independent web-based User Interface (UI) was developed to improve the workflow for interventional Magnetic Resonance Imaging (iMRI). Methods The iMRI-UI enables image acquisition of up to three independent slices using various pulse sequences with different contrast weighting. Pulse sequence, scan geometry and related parameters can be changed on the fly via the iMRI-UI using a tablet computer for improved lesion detection and interventional device targeting. The iMRI-UI was validated for core biopsies with a liver phantom (n=40) and Thiel soft-embalmed human cadavers (n=24) in a clinical 1.5T MRI scanner. Results The iMRI-UI components and setup were tested and found conditionally MRI-safe to use according to current ASTM standards. Despite minor temporary touchscreen interference at a close distance to the bore (<20 cm), no other issues regarding quality or imaging artefacts were observed. The 3D root-mean-square distance error was 2.8±1.0 (phantom) / 2.9±0.8 mm (cadaver) and overall procedure times ranged between 12–22 (phantom) / 20–55 minutes (cadaver). Conclusions The wireless iMRI-UI control setup enabled fast and accurate interventional biopsy needle placements along complex trajectories and improved the workflow for percutaneous interventions under MRI guidance in a preclinical trial. PMID:25179151

PROPELLER EPI: An MRI Technique Suitable for Diffusion Tensor Imaging at High Field Strength With Reduced Geometric Distortions

PubMed Central

Wang, Fu-Nien; Huang, Teng-Yi; Lin, Fa-Hsuan; Chuang, Tzu-Chao; Chen, Nan-Kuei; Chung, Hsiao-Wen; Chen, Cheng-Yu; Kwong, Kenneth K.

2013-01-01

A technique suitable for diffusion tensor imaging (DTI) at high field strengths is presented in this work. The method is based on a periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) k-space trajectory using EPI as the signal readout module, and hence is dubbed PROPELLER EPI. The implementation of PROPELLER EPI included a series of correction schemes to reduce possible errors associated with the intrinsically higher sensitivity of EPI to off-resonance effects. Experimental results on a 3.0 Tesla MR system showed that the PROPELLER EPI images exhibit substantially reduced geometric distortions compared with single-shot EPI, at a much lower RF specific absorption rate (SAR) than the original version of the PROPELLER fast spin-echo (FSE) technique. For DTI, the self-navigated phase-correction capability of the PROPELLER EPI sequence was shown to be effective for in vivo imaging. A higher signal-to-noise ratio (SNR) compared to single-shot EPI at an identical total scan time was achieved, which is advantageous for routine DTI applications in clinical practice. PMID:16206142

PROPELLER EPI: an MRI technique suitable for diffusion tensor imaging at high field strength with reduced geometric distortions.

PubMed

Wang, Fu-Nien; Huang, Teng-Yi; Lin, Fa-Hsuan; Chuang, Tzu-Chao; Chen, Nan-Kuei; Chung, Hsiao-Wen; Chen, Cheng-Yu; Kwong, Kenneth K

2005-11-01

A technique suitable for diffusion tensor imaging (DTI) at high field strengths is presented in this work. The method is based on a periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) k-space trajectory using EPI as the signal readout module, and hence is dubbed PROPELLER EPI. The implementation of PROPELLER EPI included a series of correction schemes to reduce possible errors associated with the intrinsically higher sensitivity of EPI to off-resonance effects. Experimental results on a 3.0 Tesla MR system showed that the PROPELLER EPI images exhibit substantially reduced geometric distortions compared with single-shot EPI, at a much lower RF specific absorption rate (SAR) than the original version of the PROPELLER fast spin-echo (FSE) technique. For DTI, the self-navigated phase-correction capability of the PROPELLER EPI sequence was shown to be effective for in vivo imaging. A higher signal-to-noise ratio (SNR) compared to single-shot EPI at an identical total scan time was achieved, which is advantageous for routine DTI applications in clinical practice. (c) 2005 Wiley-Liss, Inc.

Profiling defect depth in composite materials using thermal imaging NDE

NASA Astrophysics Data System (ADS)

Obeidat, Omar; Yu, Qiuye; Han, Xiaoyan

2018-04-01

Sonic Infrared (IR) NDE, is a relatively new NDE technology; it has been demonstrated as a reliable and sensitive method to detect defects. SIR uses ultrasonic excitation with IR imaging to detect defects and flaws in the structures being inspected. An IR camera captures infrared radiation from the target for a period of time covering the ultrasound pulse. This period of time may be much longer than the pulse depending on the defect depth and the thermal properties of the materials. With the increasing deployment of composites in modern aerospace and automobile structures, fast, wide-area and reliable NDE methods are necessary. Impact damage is one of the major concerns in modern composites. Damage can occur at a certain depth without any visual indication on the surface. Defect depth information can influence maintenance decisions. Depth profiling relies on the time delays in the captured image sequence. We'll present our work on the defect depth profiling by using the temporal information of IR images. An analytical model is introduced to describe heat diffusion from subsurface defects in composite materials. Depth profiling using peak time is introduced as well.

3D deformable image matching: a hierarchical approach over nested subspaces

NASA Astrophysics Data System (ADS)

Musse, Olivier; Heitz, Fabrice; Armspach, Jean-Paul

2000-06-01

This paper presents a fast hierarchical method to perform dense deformable inter-subject matching of 3D MR Images of the brain. To recover the complex morphological variations in neuroanatomy, a hierarchy of 3D deformations fields is estimated, by minimizing a global energy function over a sequence of nested subspaces. The nested subspaces, generated from a single scaling function, consist of deformation fields constrained at different scales. The highly non linear energy function, describing the interactions between the target and the source images, is minimized using a coarse-to-fine continuation strategy over this hierarchy. The resulting deformable matching method shows low sensitivity to local minima and is able to track large non-linear deformations, with moderate computational load. The performances of the approach are assessed both on simulated 3D transformations and on a real data base of 3D brain MR Images from different individuals. The method has shown efficient in putting into correspondence the principle anatomical structures of the brain. An application to atlas-based MRI segmentation, by transporting a labeled segmentation map on patient data, is also presented.

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.

Error mitigation for CCSD compressed imager data

NASA Astrophysics Data System (ADS)

Gladkova, Irina; Grossberg, Michael; Gottipati, Srikanth; Shahriar, Fazlul; Bonev, George

2009-08-01

To efficiently use the limited bandwidth available on the downlink from satellite to ground station, imager data is usually compressed before transmission. Transmission introduces unavoidable errors, which are only partially removed by forward error correction and packetization. In the case of the commonly used CCSD Rice-based compression, it results in a contiguous sequence of dummy values along scan lines in a band of the imager data. We have developed a method capable of using the image statistics to provide a principled estimate of the missing data. Our method outperforms interpolation yet can be performed fast enough to provide uninterrupted data flow. The estimation of the lost data provides significant value to end users who may use only part of the data, may not have statistical tools, or lack the expertise to mitigate the impact of the lost data. Since the locations of the lost data will be clearly marked as meta-data in the HDF or NetCDF header, experts who prefer to handle error mitigation themselves will be free to use or ignore our estimates as they see fit.

An interior-point method for total variation regularized positron emission tomography image reconstruction

NASA Astrophysics Data System (ADS)

Bai, Bing

2012-03-01

There has been a lot of work on total variation (TV) regularized tomographic image reconstruction recently. Many of them use gradient-based optimization algorithms with a differentiable approximation of the TV functional. In this paper we apply TV regularization in Positron Emission Tomography (PET) image reconstruction. We reconstruct the PET image in a Bayesian framework, using Poisson noise model and TV prior functional. The original optimization problem is transformed to an equivalent problem with inequality constraints by adding auxiliary variables. Then we use an interior point method with logarithmic barrier functions to solve the constrained optimization problem. In this method, a series of points approaching the solution from inside the feasible region are found by solving a sequence of subproblems characterized by an increasing positive parameter. We use preconditioned conjugate gradient (PCG) algorithm to solve the subproblems directly. The nonnegativity constraint is enforced by bend line search. The exact expression of the TV functional is used in our calculations. Simulation results show that the algorithm converges fast and the convergence is insensitive to the values of the regularization and reconstruction parameters.

The Filament Sensor for Near Real-Time Detection of Cytoskeletal Fiber Structures

PubMed Central

Eltzner, Benjamin; Wollnik, Carina; Gottschlich, Carsten; Huckemann, Stephan; Rehfeldt, Florian

2015-01-01

A reliable extraction of filament data from microscopic images is of high interest in the analysis of acto-myosin structures as early morphological markers in mechanically guided differentiation of human mesenchymal stem cells and the understanding of the underlying fiber arrangement processes. In this paper, we propose the filament sensor (FS), a fast and robust processing sequence which detects and records location, orientation, length, and width for each single filament of an image, and thus allows for the above described analysis. The extraction of these features has previously not been possible with existing methods. We evaluate the performance of the proposed FS in terms of accuracy and speed in comparison to three existing methods with respect to their limited output. Further, we provide a benchmark dataset of real cell images along with filaments manually marked by a human expert as well as simulated benchmark images. The FS clearly outperforms existing methods in terms of computational runtime and filament extraction accuracy. The implementation of the FS and the benchmark database are available as open source. PMID:25996921

Stereoscopic Planar Laser-Induced Fluorescence Imaging at 500 kHz

NASA Technical Reports Server (NTRS)

Medford, Taylor L.; Danehy, Paul M.; Jones, Stephen B.; Jiang, N.; Webster, M.; Lempert, Walter; Miller, J.; Meyer, T.

2011-01-01

A new measurement technique for obtaining time- and spatially-resolved image sequences in hypersonic flows is developed. Nitric-oxide planar laser-induced fluorescence (NO PLIF) has previously been used to investigate transition from laminar to turbulent flow in hypersonic boundary layers using both planar and volumetric imaging capabilities. Low flow rates of NO were typically seeded into the flow, minimally perturbing the flow. The volumetric imaging was performed at a measurement rate of 10 Hz using a thick planar laser sheet that excited NO fluorescence. The fluorescence was captured by a pair of cameras having slightly different views of the flow. Subsequent stereoscopic reconstruction of these images allowed the three-dimensional flow structures to be viewed. In the current paper, this approach has been extended to 50,000 times higher repetition rates. A laser operating at 500 kHz excites the seeded NO molecules, and a camera, synchronized with the laser and fitted with a beam-splitting assembly, acquires two separate images of the flow. The resulting stereoscopic images provide three-dimensional flow visualizations at 500 kHz for the first time. The 200 ns exposure time in each frame is fast enough to freeze the flow while the 500 kHz repetition rate is fast enough to time-resolve changes in the flow being studied. This method is applied to visualize the evolving hypersonic flow structures that propagate downstream of a discrete protuberance attached to a flat plate. The technique was demonstrated in the NASA Langley Research Center s 31-Inch Mach 10 Air Tunnel facility. Different tunnel Reynolds number conditions, NO flow rates and two different cylindrical protuberance heights were investigated. The location of the onset of flow unsteadiness, an indicator of transition, was observed to move downstream during the tunnel runs, coinciding with an increase in the model temperature.

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.

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.

Accelerated dynamic EPR imaging using fast acquisition and compressive recovery

NASA Astrophysics Data System (ADS)

Ahmad, Rizwan; Samouilov, Alexandre; Zweier, Jay L.

2016-12-01

Electron paramagnetic resonance (EPR) allows quantitative imaging of tissue redox status, which provides important information about ischemic syndromes, cancer and other pathologies. For continuous wave EPR imaging, however, poor signal-to-noise ratio and low acquisition efficiency limit its ability to image dynamic processes in vivo including tissue redox, where conditions can change rapidly. Here, we present a data acquisition and processing framework that couples fast acquisition with compressive sensing-inspired image recovery to enable EPR-based redox imaging with high spatial and temporal resolutions. The fast acquisition (FA) allows collecting more, albeit noisier, projections in a given scan time. The composite regularization based processing method, called spatio-temporal adaptive recovery (STAR), not only exploits sparsity in multiple representations of the spatio-temporal image but also adaptively adjusts the regularization strength for each representation based on its inherent level of the sparsity. As a result, STAR adjusts to the disparity in the level of sparsity across multiple representations, without introducing any tuning parameter. Our simulation and phantom imaging studies indicate that a combination of fast acquisition and STAR (FASTAR) enables high-fidelity recovery of volumetric image series, with each volumetric image employing less than 10 s of scan. In addition to image fidelity, the time constants derived from FASTAR also match closely to the ground truth even when a small number of projections are used for recovery. This development will enhance the capability of EPR to study fast dynamic processes that cannot be investigated using existing EPR imaging techniques.

AfterQC: automatic filtering, trimming, error removing and quality control for fastq data.

PubMed

Chen, Shifu; Huang, Tanxiao; Zhou, Yanqing; Han, Yue; Xu, Mingyan; Gu, Jia

2017-03-14

Some applications, especially those clinical applications requiring high accuracy of sequencing data, usually have to face the troubles caused by unavoidable sequencing errors. Several tools have been proposed to profile the sequencing quality, but few of them can quantify or correct the sequencing errors. This unmet requirement motivated us to develop AfterQC, a tool with functions to profile sequencing errors and correct most of them, plus highly automated quality control and data filtering features. Different from most tools, AfterQC analyses the overlapping of paired sequences for pair-end sequencing data. Based on overlapping analysis, AfterQC can detect and cut adapters, and furthermore it gives a novel function to correct wrong bases in the overlapping regions. Another new feature is to detect and visualise sequencing bubbles, which can be commonly found on the flowcell lanes and may raise sequencing errors. Besides normal per cycle quality and base content plotting, AfterQC also provides features like polyX (a long sub-sequence of a same base X) filtering, automatic trimming and K-MER based strand bias profiling. For each single or pair of FastQ files, AfterQC filters out bad reads, detects and eliminates sequencer's bubble effects, trims reads at front and tail, detects the sequencing errors and corrects part of them, and finally outputs clean data and generates HTML reports with interactive figures. AfterQC can run in batch mode with multiprocess support, it can run with a single FastQ file, a single pair of FastQ files (for pair-end sequencing), or a folder for all included FastQ files to be processed automatically. Based on overlapping analysis, AfterQC can estimate the sequencing error rate and profile the error transform distribution. The results of our error profiling tests show that the error distribution is highly platform dependent. Much more than just another new quality control (QC) tool, AfterQC is able to perform quality control, data filtering, error profiling and base correction automatically. Experimental results show that AfterQC can help to eliminate the sequencing errors for pair-end sequencing data to provide much cleaner outputs, and consequently help to reduce the false-positive variants, especially for the low-frequency somatic mutations. While providing rich configurable options, AfterQC can detect and set all the options automatically and require no argument in most cases.

In vitro comparison of water displacement method and 3 Tesla MRI for MR-volumetry of the olfactory bulb: which sequence is appropriate?

PubMed

Burmeister, Hartmut Peter; Möslein, Constanze; Bitter, Thomas; Fröber, Rosemarie; Herrmann, Karl-Heinz; Baltzer, Pascal Andreas Thomas; Gudziol, Hilmar; Dietzel, Matthias; Guntinas-Lichius, Orlando; Kaiser, Werner Alois

2011-10-01

Magnetic resonance imaging olfactory bulb (OB) volumetry (OBV) is already used as a complementary prognostic tool to assess olfactory disorders. However, a reference standard in imaging for OBV has not been established. The aim of this in vitro study was to compare volumetric results of different magnetic resonance sequences for OBV at 3 T to genuine OB volumes measured by water displacement. The volumes of 15 human cadaveric OBs were measured using the water displacement method in this institutional review board-approved prospective study. The magnetic resonance imaging protocol at 3 T included constructive interference in steady state (CISS), T2-weighted (T2w) three-dimensional (3D) sampling perfection with application-optimized contrasts using different flip-angle evolutions (SPACE), T2w two-dimensional (2D) turbo spin-echo (TSE), and T1-weighted (T1w) 3D fast low-angle shot (FLASH) sequences. Two blinded observers independently performed two OB volumetric assessments per bulbus and sequence. Intraobserver and interobserver reliabilities were assessed by intraclass correlation coefficients. Bland-Altman plots were analyzed to evaluate systematic biases and concordance correlation coefficients to assess reproducibility. For both observers, intraclass correlation coefficient analysis yielded almost perfect results for intraobserver reliability (CISS, 0.94-0.98; T2w 3D SPACE, 0.93-0.98; T2w 2D TSE, 0.98-0.98; T1w 3D FLASH, 0.95-0.99). Interobserver reliability showed almost perfect agreement for all sequences (CISS, 0.98; T2w 3D SPACE, 0.89; T2w 2D TSE, 0.93; T1w 3D FLASH, 0.97). The CISS sequence yielded the highest mean concordance correlation coefficient (0.95) and the highest combination of precision (0.97) and accuracy (0.98) values. In comparison with the water displacement method, Bland-Altman analyses revealed the lowest systematic bias (-0.5%) for the CISS sequence, followed by T1w 3D FLASH (-1.3%), T2w 3D SPACE (-7.5%), and T2w 2D TSE (-10.9%) sequences. Compared to the water displacement method, the CISS sequence is suited best to validly and reliably measure OB volumes because of its highest values for accuracy and precision and lowest systematic bias. Copyright © 2011 AUR. Published by Elsevier Inc. All rights reserved.

ARYANA: Aligning Reads by Yet Another Approach

PubMed Central

2014-01-01

Motivation Although there are many different algorithms and software tools for aligning sequencing reads, fast gapped sequence search is far from solved. Strong interest in fast alignment is best reflected in the $106 prize for the Innocentive competition on aligning a collection of reads to a given database of reference genomes. In addition, de novo assembly of next-generation sequencing long reads requires fast overlap-layout-concensus algorithms which depend on fast and accurate alignment. Contribution We introduce ARYANA, a fast gapped read aligner, developed on the base of BWA indexing infrastructure with a completely new alignment engine that makes it significantly faster than three other aligners: Bowtie2, BWA and SeqAlto, with comparable generality and accuracy. Instead of the time-consuming backtracking procedures for handling mismatches, ARYANA comes with the seed-and-extend algorithmic framework and a significantly improved efficiency by integrating novel algorithmic techniques including dynamic seed selection, bidirectional seed extension, reset-free hash tables, and gap-filling dynamic programming. As the read length increases ARYANA's superiority in terms of speed and alignment rate becomes more evident. This is in perfect harmony with the read length trend as the sequencing technologies evolve. The algorithmic platform of ARYANA makes it easy to develop mission-specific aligners for other applications using ARYANA engine. Availability ARYANA with complete source code can be obtained from http://github.com/aryana-aligner PMID:25252881

ARYANA: Aligning Reads by Yet Another Approach.

PubMed

Gholami, Milad; Arbabi, Aryan; Sharifi-Zarchi, Ali; Chitsaz, Hamidreza; Sadeghi, Mehdi

2014-01-01

Although there are many different algorithms and software tools for aligning sequencing reads, fast gapped sequence search is far from solved. Strong interest in fast alignment is best reflected in the $10(6) prize for the Innocentive competition on aligning a collection of reads to a given database of reference genomes. In addition, de novo assembly of next-generation sequencing long reads requires fast overlap-layout-concensus algorithms which depend on fast and accurate alignment. We introduce ARYANA, a fast gapped read aligner, developed on the base of BWA indexing infrastructure with a completely new alignment engine that makes it significantly faster than three other aligners: Bowtie2, BWA and SeqAlto, with comparable generality and accuracy. Instead of the time-consuming backtracking procedures for handling mismatches, ARYANA comes with the seed-and-extend algorithmic framework and a significantly improved efficiency by integrating novel algorithmic techniques including dynamic seed selection, bidirectional seed extension, reset-free hash tables, and gap-filling dynamic programming. As the read length increases ARYANA's superiority in terms of speed and alignment rate becomes more evident. This is in perfect harmony with the read length trend as the sequencing technologies evolve. The algorithmic platform of ARYANA makes it easy to develop mission-specific aligners for other applications using ARYANA engine. ARYANA with complete source code can be obtained from http://github.com/aryana-aligner.

Fast alignment-free sequence comparison using spaced-word frequencies.

PubMed

Leimeister, Chris-Andre; Boden, Marcus; Horwege, Sebastian; Lindner, Sebastian; Morgenstern, Burkhard

2014-07-15

Alignment-free methods for sequence comparison are increasingly used for genome analysis and phylogeny reconstruction; they circumvent various difficulties of traditional alignment-based approaches. In particular, alignment-free methods are much faster than pairwise or multiple alignments. They are, however, less accurate than methods based on sequence alignment. Most alignment-free approaches work by comparing the word composition of sequences. A well-known problem with these methods is that neighbouring word matches are far from independent. To reduce the statistical dependency between adjacent word matches, we propose to use 'spaced words', defined by patterns of 'match' and 'don't care' positions, for alignment-free sequence comparison. We describe a fast implementation of this approach using recursive hashing and bit operations, and we show that further improvements can be achieved by using multiple patterns instead of single patterns. To evaluate our approach, we use spaced-word frequencies as a basis for fast phylogeny reconstruction. Using real-world and simulated sequence data, we demonstrate that our multiple-pattern approach produces better phylogenies than approaches relying on contiguous words. Our program is freely available at http://spaced.gobics.de/. © The Author 2014. Published by Oxford University Press.

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.

Chemical exchange saturation transfer (CEST) MR technique for in-vivo liver imaging at 3.0 tesla.

PubMed

Chen, Shu-Zhong; Yuan, Jing; Deng, Min; Wei, Juan; Zhou, Jinyuan; Wáng, Yì-Xiáng J

2016-06-01

To evaluate Chemical Exchange Saturation Transfer (CEST) MRI for liver imaging at 3.0-T. Images were acquired at offsets (n = 41, increment = 0.25 ppm) from -5 to 5 ppm using a TSE sequence with a continuous rectangular saturation pulse. Amide proton transfer-weighted (APTw) and GlycoCEST signals were quantified as the asymmetric magnetization transfer ratio (MTRasym) at 3.5 ppm and the total MTRasym integrated from 0.5 to 1.5 ppm, respectively, from the corrected Z-spectrum. Reproducibility was assessed for rats and humans. Eight rats were devoid of chow for 24 hours and scanned before and after fasting. Eleven rats were scanned before and after one-time CCl4 intoxication. For reproducibility, rat liver APTw and GlycoCEST measurements had 95 % limits of agreement of -1.49 % to 1.28 % and -0.317 % to 0.345 %. Human liver APTw and GlycoCEST measurements had 95 % limits of agreement of -0.842 % to 0.899 % and -0.344 % to 0.164 %. After 24 hours, fasting rat liver APTw and GlycoCEST signals decreased from 2.38 ± 0.86 % to 0.67 ± 1.12 % and from 0.34 ± 0.26 % to -0.18 ± 0.37 % respectively (p < 0.05). After CCl4 intoxication rat liver APTw and GlycoCEST signals decreased from 2.46 ± 0.48 % to 1.10 ± 0.77 %, and from 0.34 ± 0.23 % to -0.16 ± 0.51 % respectively (p < 0.05). CEST liver imaging at 3.0-T showed high sensitivity for fasting as well as CCl4 intoxication. • CEST MRI of in-vivo liver was demonstrated at clinical 3 T field strength. • After 24-hour fasting, rat liver APTw and GlycoCEST signals decreased significantly. • After CCl4 intoxication both rat liver APTw and GlycoCEST signals decreased significantly. • Good scan-rescan reproducibility of liver CEST MRI was shown in healthy volunteers.

A fast image registration approach of neural activities in light-sheet fluorescence microscopy images

NASA Astrophysics Data System (ADS)

Meng, Hui; Hui, Hui; Hu, Chaoen; Yang, Xin; Tian, Jie

2017-03-01

The ability of fast and single-neuron resolution imaging of neural activities enables light-sheet fluorescence microscopy (LSFM) as a powerful imaging technique in functional neural connection applications. The state-of-art LSFM imaging system can record the neuronal activities of entire brain for small animal, such as zebrafish or C. elegans at single-neuron resolution. However, the stimulated and spontaneous movements in animal brain result in inconsistent neuron positions during recording process. It is time consuming to register the acquired large-scale images with conventional method. In this work, we address the problem of fast registration of neural positions in stacks of LSFM images. This is necessary to register brain structures and activities. To achieve fast registration of neural activities, we present a rigid registration architecture by implementation of Graphics Processing Unit (GPU). In this approach, the image stacks were preprocessed on GPU by mean stretching to reduce the computation effort. The present image was registered to the previous image stack that considered as reference. A fast Fourier transform (FFT) algorithm was used for calculating the shift of the image stack. The calculations for image registration were performed in different threads while the preparation functionality was refactored and called only once by the master thread. We implemented our registration algorithm on NVIDIA Quadro K4200 GPU under Compute Unified Device Architecture (CUDA) programming environment. The experimental results showed that the registration computation can speed-up to 550ms for a full high-resolution brain image. Our approach also has potential to be used for other dynamic image registrations in biomedical applications.

High-Speed and Scalable Whole-Brain Imaging in Rodents and Primates.

PubMed

Seiriki, Kaoru; Kasai, Atsushi; Hashimoto, Takeshi; Schulze, Wiebke; Niu, Misaki; Yamaguchi, Shun; Nakazawa, Takanobu; Inoue, Ken-Ichi; Uezono, Shiori; Takada, Masahiko; Naka, Yuichiro; Igarashi, Hisato; Tanuma, Masato; Waschek, James A; Ago, Yukio; Tanaka, Kenji F; Hayata-Takano, Atsuko; Nagayasu, Kazuki; Shintani, Norihito; Hashimoto, Ryota; Kunii, Yasuto; Hino, Mizuki; Matsumoto, Junya; Yabe, Hirooki; Nagai, Takeharu; Fujita, Katsumasa; Matsuda, Toshio; Takuma, Kazuhiro; Baba, Akemichi; Hashimoto, Hitoshi

2017-06-21

Subcellular resolution imaging of the whole brain and subsequent image analysis are prerequisites for understanding anatomical and functional brain networks. Here, we have developed a very high-speed serial-sectioning imaging system named FAST (block-face serial microscopy tomography), which acquires high-resolution images of a whole mouse brain in a speed range comparable to that of light-sheet fluorescence microscopy. FAST enables complete visualization of the brain at a resolution sufficient to resolve all cells and their subcellular structures. FAST renders unbiased quantitative group comparisons of normal and disease model brain cells for the whole brain at a high spatial resolution. Furthermore, FAST is highly scalable to non-human primate brains and human postmortem brain tissues, and can visualize neuronal projections in a whole adult marmoset brain. Thus, FAST provides new opportunities for global approaches that will allow for a better understanding of brain systems in multiple animal models and in human diseases. Copyright © 2017 Elsevier Inc. All rights reserved.

Development of a High-Throughput Microwave Imaging System for Concealed Weapons Detection

DTIC Science & Technology

2016-07-15

hardware. Index Terms—Microwave imaging, multistatic radar, Fast Fourier Transform (FFT). I. INTRODUCTION Near-field microwave imaging is a non-ionizing...configuration, but its computational demands are extreme. Fast Fourier Transform (FFT) imaging has long been used to efficiently construct images sampled with...Simulated image of 25 point scatterers imaged at range 1.5m, with array layout depicted in Fig. 3. Left: image formed with Equation (5) ( Fourier

Ultra-fast framing camera tube

DOEpatents

Kalibjian, Ralph

1981-01-01

An electronic framing camera tube features focal plane image dissection and synchronized restoration of the dissected electron line images to form two-dimensional framed images. Ultra-fast framing is performed by first streaking a two-dimensional electron image across a narrow slit, thereby dissecting the two-dimensional electron image into sequential electron line images. The dissected electron line images are then restored into a framed image by a restorer deflector operated synchronously with the dissector deflector. The number of framed images on the tube's viewing screen is equal to the number of dissecting slits in the tube. The distinguishing features of this ultra-fast framing camera tube are the focal plane dissecting slits, and the synchronously-operated restorer deflector which restores the dissected electron line images into a two-dimensional framed image. The framing camera tube can produce image frames having high spatial resolution of optical events in the sub-100 picosecond range.

Parallel imaging of knee cartilage at 3 Tesla.

PubMed

Zuo, Jin; Li, Xiaojuan; Banerjee, Suchandrima; Han, Eric; Majumdar, Sharmila

2007-10-01

To evaluate the feasibility and reproducibility of quantitative cartilage imaging with parallel imaging at 3T and to determine the impact of the acceleration factor (AF) on morphological and relaxation measurements. An eight-channel phased-array knee coil was employed for conventional and parallel imaging on a 3T scanner. The imaging protocol consisted of a T2-weighted fast spin echo (FSE), a 3D-spoiled gradient echo (SPGR), a custom 3D-SPGR T1rho, and a 3D-SPGR T2 sequence. Parallel imaging was performed with an array spatial sensitivity technique (ASSET). The left knees of six healthy volunteers were scanned with both conventional and parallel imaging (AF = 2). Morphological parameters and relaxation maps from parallel imaging methods (AF = 2) showed comparable results with conventional method. The intraclass correlation coefficient (ICC) of the two methods for cartilage volume, mean cartilage thickness, T1rho, and T2 were 0.999, 0.977, 0.964, and 0.969, respectively, while demonstrating excellent reproducibility. No significant measurement differences were found when AF reached 3 despite the low signal-to-noise ratio (SNR). The study demonstrated that parallel imaging can be applied to current knee cartilage quantification at AF = 2 without degrading measurement accuracy with good reproducibility while effectively reducing scan time. Shorter imaging times can be achieved with higher AF at the cost of SNR. (c) 2007 Wiley-Liss, Inc.

Motion-sensitized SPRITE measurements of hydrodynamic cavitation in fast pipe flow.

PubMed

Adair, Alexander; Mastikhin, Igor V; Newling, Benedict

2018-06-01

The pressure variations experienced by a liquid flowing through a pipe constriction can, in some cases, result in the formation of a bubble cloud (i.e., hydrodynamic cavitation). Due to the nature of the bubble cloud, it is ideally measured through the use of non-optical and non-invasive techniques; therefore, it is well-suited for study by magnetic resonance imaging. This paper demonstrates the use of Conical SPRITE (a 3D, centric-scan, pure phase-encoding pulse sequence) to acquire time-averaged void fraction and velocity information about hydrodynamic cavitation for water flowing through a pipe constriction. Copyright © 2018 Elsevier Inc. All rights reserved.

Application of Integral Optical Flow for Determining Crowd Movement from Video Images Obtained Using Video Surveillance Systems

NASA Astrophysics Data System (ADS)

Chen, H.; Ye, Sh.; Nedzvedz, O. V.; Ablameyko, S. V.

2018-03-01

Study of crowd movement is an important practical problem, and its solution is used in video surveillance systems for preventing various emergency situations. In the general case, a group of fast-moving people is of more interest than a group of stationary or slow-moving people. We propose a new method for crowd movement analysis using a video sequence, based on integral optical flow. We have determined several characteristics of a moving crowd such as density, speed, direction of motion, symmetry, and in/out index. These characteristics are used for further analysis of a video scene.

Non-enhanced magnetic resonance imaging of the small bowel at 7 Tesla in comparison to 1.5 Tesla: First steps towards clinical application.

PubMed

Hahnemann, Maria L; Kraff, Oliver; Maderwald, Stefan; Johst, Soeren; Orzada, Stephan; Umutlu, Lale; Ladd, Mark E; Quick, Harald H; Lauenstein, Thomas C

2016-06-01

To perform non-enhanced (NE) magnetic resonance imaging (MRI) of the small bowel at 7 Tesla (7T) and to compare it with 1.5 Tesla (1.5T). Twelve healthy subjects were prospectively examined using a 1.5T and 7T MRI system. Coronal and axial true fast imaging with steady-state precession (TrueFISP) imaging and a coronal T2-weighted (T2w) half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence were acquired. Image analysis was performed by 1) visual evaluation of tissue contrast and detail detectability, 2) measurement and calculation of contrast ratios and 3) assessment of artifacts. NE MRI of the small bowel at 7T was technically feasible. In the vast majority of the cases, tissue contrast and image details were equivalent at both field strengths. At 7T, two cases revealed better detail detectability in the TrueFISP, and better contrast in the HASTE. Susceptibility artifacts and B1 inhomogeneities were significantly increased at 7T. This study provides first insights into NE ultra-high field MRI of the small bowel and may be considered an important step towards high quality T2w abdominal imaging at 7T MRI. Copyright © 2016 Elsevier Inc. All rights reserved.

Managing multiple image stacks from confocal laser scanning microscopy

NASA Astrophysics Data System (ADS)

Zerbe, Joerg; Goetze, Christian H.; Zuschratter, Werner

1999-05-01

A major goal in neuroanatomy is to obtain precise information about the functional organization of neuronal assemblies and their interconnections. Therefore, the analysis of histological sections frequently requires high resolution images in combination with an overview about the structure. To overcome this conflict we have previously introduced a software for the automatic acquisition of multiple image stacks (3D-MISA) in confocal laser scanning microscopy. Here, we describe a Windows NT based software for fast and easy navigation through the multiple images stacks (MIS-browser), the visualization of individual channels and layers and the selection of user defined subregions. In addition, the MIS browser provides useful tools for the visualization and evaluation of the datavolume, as for instance brightness and contrast corrections of individual layers and channels. Moreover, it includes a maximum intensity projection, panning and zoom in/out functions within selected channels or focal planes (x/y) and tracking along the z-axis. The import module accepts any tiff-format and reconstructs the original image arrangement after the user has defined the sequence of images in x/y and z and the number of channels. The implemented export module allows storage of user defined subregions (new single image stacks) for further 3D-reconstruction and evaluation.

Cerebral perfusion imaging with bolus harmonic imaging (Honorable Mention Poster Award)

NASA Astrophysics Data System (ADS)

Kier, Christian; Toth, Daniel; Meyer-Wiethe, Karsten; Schindler, Angela; Cangur, Hakan; Seidel, Gunter; Aach, Til

2005-04-01

Fast visualisation of cerebral microcirculation supports diagnosis of acute stroke. However, the commonly used CT/MRI-based methods are time consuming, costly and not applicable to every patient. The bolus perfusion harmonic imaging (BHI) method is an ultrasound imaging technique which makes use of the fact, that ultrasound contrast agents unlike biological tissues resonate at harmonic frequencies. Exploiting this effect, the contrast between perfused and non-perfused areas can be improved. Thus, BHI overcomes the low signal-to-noise ratio of transcranial ultrasound and the high impedance of the skull. By analysing image sequences, visualising the qualitative characteristics of an US contrast agent bolus injection becomes possible. The analysis consists of calculating four perfusion-related parameters, Local Peak Intensity, Time To Peak, Area Under Curve, and Average Rising, from the time/intensity curve and providing them as colour-coded images. For calculating these parameters the fundamental assumption is that image intensity corresponds to contrast agent concentration which in turn shows the perfusion of the corresponding brain region. In a clinical study on patients suffering from acute ischemic stroke it is shown that some of the parameters correlate significantly to the infarction area. Thus, BHI becomes a less time-consuming and inexpensive bedside method for diagnosis of cerebral perfusion deficits.

Fast and efficient search for MPEG-4 video using adjacent pixel intensity difference quantization histogram feature

NASA Astrophysics Data System (ADS)

Lee, Feifei; Kotani, Koji; Chen, Qiu; Ohmi, Tadahiro

2010-02-01

In this paper, a fast search algorithm for MPEG-4 video clips from video database is proposed. An adjacent pixel intensity difference quantization (APIDQ) histogram is utilized as the feature vector of VOP (video object plane), which had been reliably applied to human face recognition previously. Instead of fully decompressed video sequence, partially decoded data, namely DC sequence of the video object are extracted from the video sequence. Combined with active search, a temporal pruning algorithm, fast and robust video search can be realized. The proposed search algorithm has been evaluated by total 15 hours of video contained of TV programs such as drama, talk, news, etc. to search for given 200 MPEG-4 video clips which each length is 15 seconds. Experimental results show the proposed algorithm can detect the similar video clip in merely 80ms, and Equal Error Rate (ERR) of 2 % in drama and news categories are achieved, which are more accurately and robust than conventional fast video search algorithm.

Tissue-Specific Imaging Is a Robust Methodology to Differentiate In Vivo T1 Black Holes with Advanced Multiple Sclerosis–Induced Damage

PubMed Central

Riva, M.; Ikonomidou, V.N.; Ostuni, J.J.; van Gelderen, P.; Auh, S.; Ohayon, J.M.; Tovar-Moll, F.; Richert, N.D.; Duyn, J.H.; Bagnato, F.

2017-01-01

BACKGROUND AND PURPOSE Brains of patients with multiple sclerosis (MS) characteristically have “black holes” (BHs), hypointense lesions on T1-weighted (T1W) spin-echo (SE) images. Although conventional MR imaging can disclose chronic BHs (CBHs), it cannot stage the degree of their pathologic condition. Tissue-specific imaging (TSI), a recently introduced MR imaging technique, allows selective visualization of white matter (WM), gray matter (GM), and CSF on the basis of T1 values of classes of tissue. We investigated the ability of TSI-CSF to separate CBHs with longer T1 values, which likely represent lesions containing higher levels of destruction and unbound water. MATERIALS AND METHODS Eighteen patients with MS, who had already undergone MR imaging twice (24 months apart) on a 1.5T scanner, underwent a 3T MR imaging examination. Images acquired at 1.5T included sequences of precontrast and postcontrast T1W SE, T2-weighted (T2W) SE, and magnetization transfer (MT). Sequences obtained at 3T included precontrast and postcontrast T1W SE, T2W SE, T1 inversion recovery prepared fast spoiled gradient recalled-echo (IR-FSPGR) and TSI. A BH on the 3T-IR-FSPGR was defined as a CBH if seen as a hypointense, nonenhancing lesion with a corresponding T2 abnormality for at least 24 months. CBHs were separated into 2 groups: those visible as hyperintensities on TSI-CSF (group A), and those not appearing on the TSI-CSF (group B). RESULTS Mean MT ratios of group-A lesions (0.22 ± 0.06, 0.13–0.35) were lower (F1,13 = 60.39; P < .0001) than those of group-B lesions (0.32 ± 0.03, 0.27–0.36). CONCLUSIONS Group-A lesions had more advanced tissue damage; thus, TSI is a potentially valuable method for qualitative and objective identification. PMID:19406765

Diffusion Tensor Imaging of Lumbar Nerve Roots: Comparison Between Fast Readout-Segmented and Selective-Excitation Acquisitions.

PubMed

Manoliu, Andrei; Ho, Michael; Nanz, Daniel; Piccirelli, Marco; Dappa, Evelyn; Klarhöfer, Markus; Del Grande, Filippo; Kuhn, Felix Pierre

2016-08-01

The aim of this study was to compare the quality of recently emerged advanced diffusion tensor imaging (DTI) techniques with conventional single-shot echo-planar imaging (EPI) in a functional assessment of lumbar nerve roots. The institutional review board approved the study including 12 healthy volunteers. Diffusion tensor imaging was performed at 3 T (MAGNETOM Skyra; Siemens Healthcare) with b-values of 0 and 700 s/mm and an isotropic spatial resolution for subsequent multiplanar reformatting. The nerve roots L2 to S1 were imaged in coronal orientation with readout-segmented EPI (rs-DTI) and selective-excitation EPI (sTX-DTI) with an acquisition time of 5 minutes each, and in axial orientation with single-shot EPI (ss-DTI) with an acquisition time of 12 minutes (scan parameters as in recent literature). Two independent readers qualitatively and quantitatively assessed image quality. The interobserver reliability ranged from "substantial" to "almost perfect" for all examined parameter and all 3 sequences (κ = 0.70-0.94). Overall image quality was rated higher, and artifact levels were scored lower for rs-DTI and sTX-DTI than for ss-DTI (P = 0.007-0.027), while fractional anisotropy and signal-to-noise ratio values were similar for all sequences (P ≥ 0.306 and P ≥ 0.100, respectively). Contrast-to-noise ratios were significantly higher for rs-DTI and ss-DTI than for sTX-DTI (P = 0.004-0.013). Despite shorter acquisition times, rs-DTI and sTX-DTI produced images of higher quality with smaller geometrical distortions than the current standard of reference, ss-DTI. Thus, DTI acquisitions in the coronal plane, requiring fewer slices for full coverage of exiting nerve roots, may allow for functional neurography in scan times suitable for routine clinical practice.

Image Quality of Cardiac Magnetic Resonance Imaging in Patients With an Implantable Cardioverter Defibrillator System Designed for the Magnetic Resonance Imaging Environment.

PubMed

Schwitter, Juerg; Gold, Michael R; Al Fagih, Ahmed; Lee, Sung; Peterson, Michael; Ciuffo, Allen; Zhang, Yan; Kristiansen, Nina; Kanal, Emanuel; Sommer, Torsten

2016-05-01

Recently, magnetic resonance (MR)-conditional implantable cardioverter defibrillator (ICD) systems have become available. However, associated cardiac MR image (MRI) quality is unknown. The goal was to evaluate the image quality performance of various cardiac MR sequences in a multicenter trial of patients implanted with an MR-conditional ICD system. The Evera-MRI trial enrolled 275 patients in 42 centers worldwide. There were 263 patients implanted with an Evera-MRI single- or dual-chamber ICD and randomized to controls (n=88) and MRI (n=175), 156 of whom underwent a protocol-required MRI (9-12 weeks post implant). Steady-state-free-precession (SSFP) and fast-gradient-echo (FGE) sequences were acquired in short-axis and horizontal long-axis orientations. Qualitative and quantitative assessment of image quality was performed by using a 7-point scale (grades 1-3: good quality, grades 6-7: nondiagnostic) and measuring ICD- and lead-related artifact size. Good to moderate image quality (grades 1-5) was obtained in 53% and 74% of SSFP and FGE acquisitions, respectively, covering the left ventricle, and in 69% and 84%, respectively, covering the right ventricle. Odds for better image quality were greater for right ventricle versus left ventricle (odds ratio, 1.8; 95% confidence interval, 1.5-2.2; P<0.0001) and greater for FGE versus SSFP (odds ratio, 3.5; 95% confidence interval, 2.5-4.8; P<0.0001). Compared with SSFP, ICD-related artifacts on FGE were smaller (141±65 versus 75±57 mm, respectively; P<0.0001). Lead artifacts were much smaller than ICD artifacts (P<0.0001). FGE yields good to moderate quality in 74% of left ventricle and 84% of right ventricle acquisitions and performs better than SSFP in patients with an MRI-conditional ICD system. In these patients, cardiac MRI can offer diagnostic information in most cases. URL: http://www.clinicaltrials.gov. Unique identifier: NCT02117414. © 2016 American Heart Association, Inc.

Magnetic resonance imaging for simultaneous morphological and functional evaluation of esophageal motility disorders.

PubMed

Miyazaki, Yasuhiro; Nakajima, Kiyokazu; Sumikawa, Mitsuhiro; Yamasaki, Makoto; Takahashi, Tsuyoshi; Miyata, Hiroshi; Takiguchi, Shuji; Kurokawa, Yukinori; Tomiyama, Noriyuki; Mori, Masaki; Doki, Yuichiro

2014-04-01

The purpose of this study was to evaluate the feasibility and safety of esophageal functional magnetic resonance imaging (fMRI) for the diagnosis of achalasia. Eleven patients with suspected achalasia and three normal subjects underwent fMRI while swallowing clear liquid with original sequences; "T2-weighed single-shot fast spin-echo" and "Fast Imaging Employing Steady-state Acquisition". The fMRI-based diagnosis was compared with that based on manometry. The luminal fluctuation index (LFI) and Dd/Ds ratio were used for the objective evaluation of the esophageal peristalsis and relaxation of the lower esophageal sphincter (LES). Functional MRI showed a dilated tortuous esophagus with no tumor, poor clearance, simultaneous waves, aperistalsis, and impaired LES relaxation in all but one case, allowing the diagnosis of achalasia with accuracy similar to that of manometry. The LFI (median 0.08, range 0.03-0.25) and Dd/Ds ratio (1.40, 1.0-2.3) of the patient group were significantly lower than those of the normal subjects [1.50, 2.32-4.05, and 2.59 (2.32-4.05)]. No severe adverse events directly related to fMRI were noted. Using our protocol, fMRI was considered to be safe and feasible for the diagnosis of achalasia. Given the widespread use of MRI, esophageal fMRI, which does not require exposure to radiation, could be a potentially useful diagnostic tool for patients with esophageal motility disorders.

Big Data Application in Biomedical Research and Health Care: A Literature Review.

PubMed

Luo, Jake; Wu, Min; Gopukumar, Deepika; Zhao, Yiqing

2016-01-01

Big data technologies are increasingly used for biomedical and health-care informatics research. Large amounts of biological and clinical data have been generated and collected at an unprecedented speed and scale. For example, the new generation of sequencing technologies enables the processing of billions of DNA sequence data per day, and the application of electronic health records (EHRs) is documenting large amounts of patient data. The cost of acquiring and analyzing biomedical data is expected to decrease dramatically with the help of technology upgrades, such as the emergence of new sequencing machines, the development of novel hardware and software for parallel computing, and the extensive expansion of EHRs. Big data applications present new opportunities to discover new knowledge and create novel methods to improve the quality of health care. The application of big data in health care is a fast-growing field, with many new discoveries and methodologies published in the last five years. In this paper, we review and discuss big data application in four major biomedical subdisciplines: (1) bioinformatics, (2) clinical informatics, (3) imaging informatics, and (4) public health informatics. Specifically, in bioinformatics, high-throughput experiments facilitate the research of new genome-wide association studies of diseases, and with clinical informatics, the clinical field benefits from the vast amount of collected patient data for making intelligent decisions. Imaging informatics is now more rapidly integrated with cloud platforms to share medical image data and workflows, and public health informatics leverages big data techniques for predicting and monitoring infectious disease outbreaks, such as Ebola. In this paper, we review the recent progress and breakthroughs of big data applications in these health-care domains and summarize the challenges, gaps, and opportunities to improve and advance big data applications in health care.

Big Data Application in Biomedical Research and Health Care: A Literature Review

PubMed Central

Luo, Jake; Wu, Min; Gopukumar, Deepika; Zhao, Yiqing

2016-01-01

Big data technologies are increasingly used for biomedical and health-care informatics research. Large amounts of biological and clinical data have been generated and collected at an unprecedented speed and scale. For example, the new generation of sequencing technologies enables the processing of billions of DNA sequence data per day, and the application of electronic health records (EHRs) is documenting large amounts of patient data. The cost of acquiring and analyzing biomedical data is expected to decrease dramatically with the help of technology upgrades, such as the emergence of new sequencing machines, the development of novel hardware and software for parallel computing, and the extensive expansion of EHRs. Big data applications present new opportunities to discover new knowledge and create novel methods to improve the quality of health care. The application of big data in health care is a fast-growing field, with many new discoveries and methodologies published in the last five years. In this paper, we review and discuss big data application in four major biomedical subdisciplines: (1) bioinformatics, (2) clinical informatics, (3) imaging informatics, and (4) public health informatics. Specifically, in bioinformatics, high-throughput experiments facilitate the research of new genome-wide association studies of diseases, and with clinical informatics, the clinical field benefits from the vast amount of collected patient data for making intelligent decisions. Imaging informatics is now more rapidly integrated with cloud platforms to share medical image data and workflows, and public health informatics leverages big data techniques for predicting and monitoring infectious disease outbreaks, such as Ebola. In this paper, we review the recent progress and breakthroughs of big data applications in these health-care domains and summarize the challenges, gaps, and opportunities to improve and advance big data applications in health care. PMID:26843812

Non-rigid estimation of cell motion in calcium time-lapse images

NASA Astrophysics Data System (ADS)

Hachi, Siham; Lucumi Moreno, Edinson; Desmet, An-Sofie; Vanden Berghe, Pieter; Fleming, Ronan M. T.

2016-03-01

Calcium imaging is a widely used technique in neuroscience permitting the simultaneous monitoring of electro- physiological activity of hundreds of neurons at single cell resolution. Identification of neuronal activity requires rapid and reliable image analysis techniques, especially when neurons fire and move simultaneously over time. Traditionally, image segmentation is performed to extract individual neurons in the first frame of a calcium sequence. Thereafter, the mean intensity is calculated from the same region of interest in each frame to infer calcium signals. However, when cells move, deform and fire, this segmentation on its own generates artefacts and therefore biased neuronal activity. Therefore, there is a pressing need to develop a more efficient cell tracking technique. We hereby present a novel vision-based cell tracking scheme using a thin-plate spline deformable model. The thin-plate spline warping is based on control points detected using the Fast from Accelerated Segment Test descriptor and tracked using the Lucas-Kanade optical flow. Our method is able to track neurons in calcium time-series, even when there are large changes in intensity, such as during a firing event. The robustness and efficiency of the proposed approach is validated on real calcium time-lapse images of a neuronal population.

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.

Music-Based Magnetic Resonance Fingerprinting to Improve Patient Comfort During MRI Exams

PubMed Central

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

2015-01-01

Purpose The unpleasant acoustic noise is an important drawback of almost every magnetic resonance imaging scan. Instead of reducing the acoustic noise to improve patient comfort, a method is proposed to mitigate the noise problem by producing musical sounds directly from the switching magnetic fields while simultaneously quantifying multiple important tissue properties. Theory and Methods MP3 music files were converted to arbitrary encoding gradients, which were then used with varying flip angles and TRs in both 2D and 3D MRF exam. 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. Results The MRF-Music scans were shown to significantly improve the patients' comfort during the MRI scans. 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. Conclusions MRF-Music sequence provides significant improvement of the patient's comfort as compared to the MRF scan and other fast imaging techniques such as EPI and TSE scans. It is also a fast and accurate quantitative method that quantifies multiple relaxation parameter simultaneously. PMID:26178439

WE-DE-BRA-09: Fast Megavoltage CT Imaging with Rapid Scan Time and Low Imaging Dose in Helical Tomotherapy

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

Magome, T; University of Tokyo Hospital, Tokyo; University of Minnesota, Minneapolis, MN

Purpose: Megavoltage computed tomography (MVCT) imaging has been widely used for daily patient setup with helical tomotherapy (HT). One drawback of MVCT is its very long imaging time, owing to slow couch speed. The purpose of this study was to develop an MVCT imaging method allowing faster couch speeds, and to assess its accuracy for image guidance for HT. Methods: Three cadavers (mimicking closest physiological and physical system of patients) were scanned four times with couch speeds of 1, 2, 3, and 4 mm/s. The resulting MVCT images were reconstructed using an iterative reconstruction (IR) algorithm. The MVCT images weremore » registered with kilovoltage CT images, and the registration errors were compared with the errors with conventional filtered back projection (FBP) algorithm. Moreover, the fast MVCT imaging was tested in three cases of total marrow irradiation as a clinical trial. Results: Three-dimensional registration errors of the MVCT images reconstructed with the IR algorithm were significantly smaller (p < 0.05) than the errors of images reconstructed with the FBP algorithm at fast couch speeds (3, 4 mm/s). The scan time and imaging dose at a speed of 4 mm/s were reduced to 30% of those from a conventional coarse mode scan. For the patient imaging, a limited number of conventional MVCT (1.2 mm/s) and fast MVCT (3 mm/s) reveals acceptable reduced imaging time and dose able to use for anatomical registration. Conclusion: Fast MVCT with IR algorithm maybe clinically feasible alternative for rapid 3D patient localization. This technique may also be useful for calculating daily dose distributions or organ motion analyses in HT treatment over a wide area.« less

A comparison of five standard methods for evaluating image intensity uniformity in partially parallel imaging MRI

PubMed Central

Goerner, Frank L.; Duong, Timothy; Stafford, R. Jason; Clarke, Geoffrey D.

2013-01-01

Purpose: To investigate the utility of five different standard measurement methods for determining image uniformity for partially parallel imaging (PPI) acquisitions in terms of consistency across a variety of pulse sequences and reconstruction strategies. Methods: Images were produced with a phantom using a 12-channel head matrix coil in a 3T MRI system (TIM TRIO, Siemens Medical Solutions, Erlangen, Germany). Images produced using echo-planar, fast spin echo, gradient echo, and balanced steady state free precession pulse sequences were evaluated. Two different PPI reconstruction methods were investigated, generalized autocalibrating partially parallel acquisition algorithm (GRAPPA) and modified sensitivity-encoding (mSENSE) with acceleration factors (R) of 2, 3, and 4. Additionally images were acquired with conventional, two-dimensional Fourier imaging methods (R = 1). Five measurement methods of uniformity, recommended by the American College of Radiology (ACR) and the National Electrical Manufacturers Association (NEMA) were considered. The methods investigated were (1) an ACR method and a (2) NEMA method for calculating the peak deviation nonuniformity, (3) a modification of a NEMA method used to produce a gray scale uniformity map, (4) determining the normalized absolute average deviation uniformity, and (5) a NEMA method that focused on 17 areas of the image to measure uniformity. Changes in uniformity as a function of reconstruction method at the same R-value were also investigated. Two-way analysis of variance (ANOVA) was used to determine whether R-value or reconstruction method had a greater influence on signal intensity uniformity measurements for partially parallel MRI. Results: Two of the methods studied had consistently negative slopes when signal intensity uniformity was plotted against R-value. The results obtained comparing mSENSE against GRAPPA found no consistent difference between GRAPPA and mSENSE with regard to signal intensity uniformity. The results of the two-way ANOVA analysis suggest that R-value and pulse sequence type produce the largest influences on uniformity and PPI reconstruction method had relatively little effect. Conclusions: Two of the methods of measuring signal intensity uniformity, described by the (NEMA) MRI standards, consistently indicated a decrease in uniformity with an increase in R-value. Other methods investigated did not demonstrate consistent results for evaluating signal uniformity in MR images obtained by partially parallel methods. However, because the spatial distribution of noise affects uniformity, it is recommended that additional uniformity quality metrics be investigated for partially parallel MR images. PMID:23927345

Fast volumetric imaging with patterned illumination via digital micro-mirror device-based temporal focusing multiphoton microscopy.

PubMed

Chang, Chia-Yuan; Hu, Yvonne Yuling; Lin, Chun-Yu; Lin, Cheng-Han; Chang, Hsin-Yu; Tsai, Sheng-Feng; Lin, Tzu-Wei; Chen, Shean-Jen

2016-05-01

Temporal focusing multiphoton microscopy (TFMPM) has the advantage of area excitation in an axial confinement of only a few microns; hence, it can offer fast three-dimensional (3D) multiphoton imaging. Herein, fast volumetric imaging via a developed digital micromirror device (DMD)-based TFMPM has been realized through the synchronization of an electron multiplying charge-coupled device (EMCCD) with a dynamic piezoelectric stage for axial scanning. The volumetric imaging rate can achieve 30 volumes per second according to the EMCCD frame rate of more than 400 frames per second, which allows for the 3D Brownian motion of one-micron fluorescent beads to be spatially observed. Furthermore, it is demonstrated that the dynamic HiLo structural multiphoton microscope can reject background noise by way of the fast volumetric imaging with high-speed DMD patterned illumination.

Using dynamic interferometric synthetic aperature radar (InSAR) to image fast-moving surface waves

DOEpatents

Vincent, Paul

2005-06-28

A new differential technique and system for imaging dynamic (fast moving) surface waves using Dynamic Interferometric Synthetic Aperture Radar (InSAR) is introduced. This differential technique and system can sample the fast-moving surface displacement waves from a plurality of moving platform positions in either a repeat-pass single-antenna or a single-pass mode having a single-antenna dual-phase receiver or having dual physically separate antennas, and reconstruct a plurality of phase differentials from a plurality of platform positions to produce a series of desired interferometric images of the fast moving waves.

Measurement of instantaneous rotational speed using double-sine-varying-density fringe pattern

NASA Astrophysics Data System (ADS)

Zhong, Jianfeng; Zhong, Shuncong; Zhang, Qiukun; Peng, Zhike

2018-03-01

Fast and accurate rotational speed measurement is required both for condition monitoring and faults diagnose of rotating machineries. A vision- and fringe pattern-based rotational speed measurement system was proposed to measure the instantaneous rotational speed (IRS) with high accuracy and reliability. A special double-sine-varying-density fringe pattern (DSVD-FP) was designed and pasted around the shaft surface completely and worked as primary angular sensor. The rotational angle could be correctly obtained from the left and right fringe period densities (FPDs) of the DSVD-FP image sequence recorded by a high-speed camera. The instantaneous angular speed (IAS) between two adjacent frames could be calculated from the real-time rotational angle curves, thus, the IRS also could be obtained accurately and efficiently. Both the measurement principle and system design of the novel method have been presented. The influence factors on the sensing characteristics and measurement accuracy of the novel system, including the spectral centrobaric correction method (SCCM) on the FPD calculation, the noise sources introduce by the image sensor, the exposure time and the vibration of the shaft, were investigated through simulations and experiments. The sampling rate of the high speed camera could be up to 5000 Hz, thus, the measurement becomes very fast and the change in rotational speed was sensed within 0.2 ms. The experimental results for different IRS measurements and characterization of the response property of a servo motor demonstrated the high accuracy and fast measurement of the proposed technique, making it attractive for condition monitoring and faults diagnosis of rotating machineries.

Fast Image Restoration for Spatially Varying Defocus Blur of Imaging Sensor

PubMed Central

Cheong, Hejin; Chae, Eunjung; Lee, Eunsung; Jo, Gwanghyun; Paik, Joonki

2015-01-01

This paper presents a fast adaptive image restoration method for removing spatially varying out-of-focus blur of a general imaging sensor. After estimating the parameters of space-variant point-spread-function (PSF) using the derivative in each uniformly blurred region, the proposed method performs spatially adaptive image restoration by selecting the optimal restoration filter according to the estimated blur parameters. Each restoration filter is implemented in the form of a combination of multiple FIR filters, which guarantees the fast image restoration without the need of iterative or recursive processing. Experimental results show that the proposed method outperforms existing space-invariant restoration methods in the sense of both objective and subjective performance measures. The proposed algorithm can be employed to a wide area of image restoration applications, such as mobile imaging devices, robot vision, and satellite image processing. PMID:25569760

Volumetric imaging of fast biological dynamics in deep tissue via wavefront engineering

NASA Astrophysics Data System (ADS)

Kong, Lingjie; Tang, Jianyong; Cui, Meng

2016-03-01

To reveal fast biological dynamics in deep tissue, we combine two wavefront engineering methods that were developed in our laboratory, namely optical phase-locked ultrasound lens (OPLUL) based volumetric imaging and iterative multiphoton adaptive compensation technique (IMPACT). OPLUL is used to generate oscillating defocusing wavefront for fast axial scanning, and IMPACT is used to compensate the wavefront distortions for deep tissue imaging. We show its promising applications in neuroscience and immunology.

Simultaneous fast scanning XRF, dark field, phase-, and absorption contrast tomography

NASA Astrophysics Data System (ADS)

Medjoubi, Kadda; Bonissent, Alain; Leclercq, Nicolas; Langlois, Florent; Mercère, Pascal; Somogyi, Andrea

2013-09-01

Scanning hard X-ray nanoprobe imaging provides a unique tool for probing specimens with high sensitivity and large penetration depth. Moreover, the combination of complementary techniques such as X-ray fluorescence, absorption, phase contrast and dark field imaging gives complete quantitative information on the sample structure, composition and chemistry. The multi-technique "FLYSCAN" data acquisition scheme developed at Synchrotron SOLEIL permits to perform fast continuous scanning imaging and as such makes scanning tomography techniques feasible in a time-frame well-adapted to typical user experiments. Here we present the recent results of simultaneous fast scanning multi-technique tomography performed at Soleil. This fast scanning scheme will be implemented at the Nanoscopium beamline for large field of view 2D and 3D multimodal imaging.

The cost of proactive interference is constant across presentation conditions.

PubMed

Endress, Ansgar D; Siddique, Aneela

2016-10-01

Proactive interference (PI) severely constrains how many items people can remember. For example, Endress and Potter (2014a) presented participants with sequences of everyday objects at 250ms/picture, followed by a yes/no recognition test. They manipulated PI by either using new images on every trial in the unique condition (thus minimizing PI among items), or by re-using images from a limited pool for all trials in the repeated condition (thus maximizing PI among items). In the low-PI unique condition, the probability of remembering an item was essentially independent of the number of memory items, showing no clear memory limitations; more traditional working memory-like memory limitations appeared only in the high-PI repeated condition. Here, we ask whether the effects of PI are modulated by the availability of long-term memory (LTM) and verbal resources. Participants viewed sequences of 21 images, followed by a yes/no recognition test. Items were presented either quickly (250ms/image) or sufficiently slowly (1500ms/image) to produce LTM representations, either with or without verbal suppression. Across conditions, participants performed better in the unique than in the repeated condition, and better for slow than for fast presentations. In contrast, verbal suppression impaired performance only with slow presentations. The relative cost of PI was remarkably constant across conditions: relative to the unique condition, performance in the repeated condition was about 15% lower in all conditions. The cost of PI thus seems to be a function of the relative strength or recency of target items and interfering items, but relatively insensitive to other experimental manipulations. Copyright © 2016 Elsevier B.V. All rights reserved.

SU-E-J-257: Image Artifacts Caused by Implanted Calypso Beacons in MRI Studies

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

Amro, H; Chetty, I; Gordon, J

2014-06-01

Purpose: The presence of Calypso Beacon-transponders in patients can cause artifacts during MRI imaging studies. This could be a problem for post-treatment follow up of cancer patients using MRI studies to evaluate metastasis and for functional imaging studies.This work assesses (1) the volume immediately surrounding the transponders that will not be visualized by the MRI due to the beacons, and (2) the dependence of the non-visualized volume on beacon orientation, and scanning techniques. Methods: Two phantoms were used in this study (1) water filled box, (2) and a 2300 cc block of pork meat. Calypso beacons were implanted in themore » phantoms both in parallel and perpendicular orientations with respect to the MR scanner magnetic field. MR image series of the phantom were obtained with on a 1.0T high field open MR-SIM with multiple pulse sequences, for example, T1-weighted fast field echo and T2-weighted turbo spin echo. Results: On average, a no-signal region with 2 cm radius and 3 cm length was measured. Image artifacts are more significant when beacons are placed parallel to scanner magnetic field; the no-signal area around the beacon was about 0.5 cm larger in orthogonal orientation. The no-signal region surrounding the beacons slightly varies in dimension for the different pulse sequences. Conclusion: The use of Calypso beacons can prohibit the use of MRI studies in post-treatment assessments, especially in the immediate region surrounding the implanted beacon. A characterization of the MR scanner by identifying the no-signal regions due to implanted beacons is essential. This may render the use of Calypso beacons useful for some cases and give the treating physician a chance to identify those patients prior to beacon implantation.« less

Accelerated dynamic EPR imaging using fast acquisition and compressive recovery.

PubMed

Ahmad, Rizwan; Samouilov, Alexandre; Zweier, Jay L

2016-12-01

Electron paramagnetic resonance (EPR) allows quantitative imaging of tissue redox status, which provides important information about ischemic syndromes, cancer and other pathologies. For continuous wave EPR imaging, however, poor signal-to-noise ratio and low acquisition efficiency limit its ability to image dynamic processes in vivo including tissue redox, where conditions can change rapidly. Here, we present a data acquisition and processing framework that couples fast acquisition with compressive sensing-inspired image recovery to enable EPR-based redox imaging with high spatial and temporal resolutions. The fast acquisition (FA) allows collecting more, albeit noisier, projections in a given scan time. The composite regularization based processing method, called spatio-temporal adaptive recovery (STAR), not only exploits sparsity in multiple representations of the spatio-temporal image but also adaptively adjusts the regularization strength for each representation based on its inherent level of the sparsity. As a result, STAR adjusts to the disparity in the level of sparsity across multiple representations, without introducing any tuning parameter. Our simulation and phantom imaging studies indicate that a combination of fast acquisition and STAR (FASTAR) enables high-fidelity recovery of volumetric image series, with each volumetric image employing less than 10 s of scan. In addition to image fidelity, the time constants derived from FASTAR also match closely to the ground truth even when a small number of projections are used for recovery. This development will enhance the capability of EPR to study fast dynamic processes that cannot be investigated using existing EPR imaging techniques. Copyright © 2016 Elsevier Inc. All rights reserved.

SeqBox: RNAseq/ChIPseq reproducible analysis on a consumer game computer.

PubMed

Beccuti, Marco; Cordero, Francesca; Arigoni, Maddalena; Panero, Riccardo; Amparore, Elvio G; Donatelli, Susanna; Calogero, Raffaele A

2018-03-01

Short reads sequencing technology has been used for more than a decade now. However, the analysis of RNAseq and ChIPseq data is still computational demanding and the simple access to raw data does not guarantee results reproducibility between laboratories. To address these two aspects, we developed SeqBox, a cheap, efficient and reproducible RNAseq/ChIPseq hardware/software solution based on NUC6I7KYK mini-PC (an Intel consumer game computer with a fast processor and a high performance SSD disk), and Docker container platform. In SeqBox the analysis of RNAseq and ChIPseq data is supported by a friendly GUI. This allows access to fast and reproducible analysis also to scientists with/without scripting experience. Docker container images, docker4seq package and the GUI are available at http://www.bioinformatica.unito.it/reproducibile.bioinformatics.html. beccuti@di.unito.it. Supplementary data are available at Bioinformatics online. © The Author(s) 2017. Published by Oxford University Press.

Fast-response underwater TSP investigation of subcritical instabilities of a cylinder in crossflow

NASA Astrophysics Data System (ADS)

Capone, Alessandro; Klein, Christian; Di Felice, Fabio; Beifuss, Uwe; Miozzi, Massimo

2015-10-01

We investigate the classic cylinder in crossflow case to test the effectiveness of a fast-response underwater temperature-sensitive paint coating (TSP) in providing highly resolved spatial and time observations of the action of a flow over a bluff body surface. The flow is investigated at Reynolds number <190 k, before the onset of the drag-crisis state. The obtained TSP image sequences convey an accurate description of the evolution of the main features in the fluid-cylinder interaction, like the separation line position, the pattern of the large coherent structures acting on the cylinder's surface and the small-scale intermittent streamwise arrays of vortices. Ad hoc data management and features extraction techniques are proposed which allow extraction of quantitative data, such as separation line position and vortex-shedding frequency, and results are compared to the literature. Use of TSP for water applications introduces an interesting point of view about the fluid-body interactions by focusing directly on the effect of the flow on the model surface.

Scene-based nonuniformity correction algorithm based on interframe registration.

PubMed

Zuo, Chao; Chen, Qian; Gu, Guohua; Sui, Xiubao

2011-06-01

In this paper, we present a simple and effective scene-based nonuniformity correction (NUC) method for infrared focal plane arrays based on interframe registration. This method estimates the global translation between two adjacent frames and minimizes the mean square error between the two properly registered images to make any two detectors with the same scene produce the same output value. In this way, the accumulation of the registration error can be avoided and the NUC can be achieved. The advantages of the proposed algorithm lie in its low computational complexity and storage requirements and ability to capture temporal drifts in the nonuniformity parameters. The performance of the proposed technique is thoroughly studied with infrared image sequences with simulated nonuniformity and infrared imagery with real nonuniformity. It shows a significantly fast and reliable fixed-pattern noise reduction and obtains an effective frame-by-frame adaptive estimation of each detector's gain and offset.

[MR myelography: analysis of 126 cases].

PubMed

Wang, W; Zhang, X; Lu, Y

2000-03-01

To investigate the value and limitation of MR myelography (MRM) in depicting the spinal canal obstruction. Heavily T2-weighted coronal MR myelography was performed with 3D fast-spin-echo (FSE) and fat-suppression sequence in 126 cases, including 6 cerebellomedullary cistern, 18 cervical, 19 thoracic and 83 lumbar cases. The resulting slice were then projected into a composite image using a standard maxium intensity projection (MIP) algorithm. 90.5% (114/126) of MRM yielded reproducible high-quality image of the spinal thecal sac. 106 lesions (extradural, intradural, intramedullary) were detected in 101 cases (80.2%). The level and degree of spinal canal obstruction were visualized and confirmed by operation in 66 cases with a high sensitivity of 100%, and a diagnostic accuracy of 91.3%. Heavily T2 FSE MR myelography is a noninvasive and reliable method. MRM surpasses conventional and CT myelography and could replace them in some degree.

Dynamic nuclear polarization and optimal control spatial-selective 13C MRI and MRS

NASA Astrophysics Data System (ADS)

Vinding, Mads S.; Laustsen, Christoffer; Maximov, Ivan I.; Søgaard, Lise Vejby; Ardenkjær-Larsen, Jan H.; Nielsen, Niels Chr.

2013-02-01

Aimed at 13C metabolic magnetic resonance imaging (MRI) and spectroscopy (MRS) applications, we demonstrate that dynamic nuclear polarization (DNP) may be combined with optimal control 2D spatial selection to simultaneously obtain high sensitivity and well-defined spatial restriction. This is achieved through the development of spatial-selective single-shot spiral-readout MRI and MRS experiments combined with dynamic nuclear polarization hyperpolarized [1-13C]pyruvate on a 4.7 T pre-clinical MR scanner. The method stands out from related techniques by facilitating anatomic shaped region-of-interest (ROI) single metabolite signals available for higher image resolution or single-peak spectra. The 2D spatial-selective rf pulses were designed using a novel Krotov-based optimal control approach capable of iteratively fast providing successful pulse sequences in the absence of qualified initial guesses. The technique may be important for early detection of abnormal metabolism, monitoring disease progression, and drug research.

Improved target detection algorithm using Fukunaga-Koontz transform and distance classifier correlation filter

NASA Astrophysics Data System (ADS)

Bal, A.; Alam, M. S.; Aslan, M. S.

2006-05-01

Often sensor ego-motion or fast target movement causes the target to temporarily go out of the field-of-view leading to reappearing target detection problem in target tracking applications. Since the target goes out of the current frame and reenters at a later frame, the reentering location and variations in rotation, scale, and other 3D orientations of the target are not known thus complicating the detection algorithm has been developed using Fukunaga-Koontz Transform (FKT) and distance classifier correlation filter (DCCF). The detection algorithm uses target and background information, extracted from training samples, to detect possible candidate target images. The detected candidate target images are then introduced into the second algorithm, DCCF, called clutter rejection module, to determine the target coordinates are detected and tracking algorithm is initiated. The performance of the proposed FKT-DCCF based target detection algorithm has been tested using real-world forward looking infrared (FLIR) video sequences.

Design of Instrument Control Software for Solar Vector Magnetograph at Udaipur Solar Observatory

NASA Astrophysics Data System (ADS)

Gosain, Sanjay; Venkatakrishnan, P.; Venugopalan, K.

2004-04-01

A magnetograph is an instrument which makes measurement of solar magnetic field by measuring Zeeman induced polarization in solar spectral lines. In a typical filter based magnetograph there are three main modules namely, polarimeter, narrow-band spectrometer (filter), and imager(CCD camera). For a successful operation of magnetograph it is essential that these modules work in synchronization with each other. Here, we describe the design of instrument control system implemented for the Solar Vector Magnetograph under development at Udaipur Solar Observatory. The control software is written in Visual Basic and exploits the Component Object Model (COM) components for a fast and flexible application development. The user can interact with the instrument modules through a Graphical User Interface (GUI) and can program the sequence of magnetograph operations. The integration of Interactive Data Language (IDL) ActiveX components in the interface provides a powerful tool for online visualization, analysis and processing of images.

Object tracking using plenoptic image sequences

NASA Astrophysics Data System (ADS)

Kim, Jae Woo; Bae, Seong-Joon; Park, Seongjin; Kim, Do Hyung

2017-05-01

Object tracking is a very important problem in computer vision research. Among the difficulties of object tracking, partial occlusion problem is one of the most serious and challenging problems. To address the problem, we proposed novel approaches to object tracking on plenoptic image sequences. Our approaches take advantage of the refocusing capability that plenoptic images provide. Our approaches input the sequences of focal stacks constructed from plenoptic image sequences. The proposed image selection algorithms select the sequence of optimal images that can maximize the tracking accuracy from the sequence of focal stacks. Focus measure approach and confidence measure approach were proposed for image selection and both of the approaches were validated by the experiments using thirteen plenoptic image sequences that include heavily occluded target objects. The experimental results showed that the proposed approaches were satisfactory comparing to the conventional 2D object tracking algorithms.

Extracting flat-field images from scene-based image sequences using phase correlation

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

Caron, James N., E-mail: Caron@RSImd.com; Montes, Marcos J.; Obermark, Jerome L.

Flat-field image processing is an essential step in producing high-quality and radiometrically calibrated images. Flat-fielding corrects for variations in the gain of focal plane array electronics and unequal illumination from the system optics. Typically, a flat-field image is captured by imaging a radiometrically uniform surface. The flat-field image is normalized and removed from the images. There are circumstances, such as with remote sensing, where a flat-field image cannot be acquired in this manner. For these cases, we developed a phase-correlation method that allows the extraction of an effective flat-field image from a sequence of scene-based displaced images. The method usesmore » sub-pixel phase correlation image registration to align the sequence to estimate the static scene. The scene is removed from sequence producing a sequence of misaligned flat-field images. An average flat-field image is derived from the realigned flat-field sequence.« less

Fast single-pass alignment and variant calling using sequencing data

USDA-ARS?s Scientific Manuscript database

Sequencing research requires efficient computation. Few programs use already known information about DNA variants when aligning sequence data to the reference map. New program findmap.f90 reads the previous variant list before aligning sequence, calling variant alleles, and summing the allele counts...

Left ventricular function assessment using a fast 3D gradient echo pulse sequence: comparison to standard multi-breath hold 2D steady state free precession imaging and accounting for papillary muscles and trabeculations.

PubMed

Sievers, Burkhard; Schrader, Sebastian; Rehwald, Wolfgang; Hunold, Peter; Barkhausen, Joerg; Erbel, Raimund

2011-06-01

Papillary muscles and trabeculae for ventricular function analysis are known to significantly contribute to accurate volume and mass measurements. Fast imaging techniques such as three-dimensional steady-state free precession (3D SSFP) are increasingly being used to speed up imaging time, but sacrifice spatial resolution. It is unknown whether 3D SSFP, despite its reduced spatial resolution, allows for exact delineation of papillary muscles and trabeculations. We therefore compared 3D SSFP ventricular function measurements to those measured from standard multi-breath hold two-dimensional steady-state free precession cine images (standard 2D SSFP). 14 healthy subjects and 14 patients with impaired left ventricularfunction underwent 1.5 Tesla cine imaging. A stack of short axis images covering the left ventricle was acquired with 2D SSFP and 3D SSFP. Left ventricular volumes, ejection fraction, and mass were determined. Analysis was performed by substracting papillary muscles and trabeculae from left ventricular volumes. In addition, reproducibility was assessed. EDV, ESV, EF, and mass were not significantly different between 2D SSFP and 3D SSFP (mean difference healthy subjects: -0.06 +/- 3.2 ml, 0.54 +/- 2.2 ml, -0.45 +/- 1.8%, and 1.13 +/- 0.8 g, respectively; patients: 1.36 +/- 2.8 ml, -0.15 3.5 ml, 0.86 +/- 2.5%, and 0.91 +/- 0.9 g, respectively; P > or = 0.095). Intra- and interobserver variability was not different for 2D SSFP (P > or = 0.64 and P > or = 0.397) and 3D SSFP (P > or = 0.53 and P > or = 0.47). Differences in volumes, EF, and mass measurements between 3D SSFP and standard 2D SSFP are very small, and not statistically significant. 3D SSFP may be used for accurate ventricular function assessment when papillary muscles and trabeculations are to be taken into account.

INFO-RNA--a server for fast inverse RNA folding satisfying sequence constraints.

PubMed

Busch, Anke; Backofen, Rolf

2007-07-01

INFO-RNA is a new web server for designing RNA sequences that fold into a user given secondary structure. Furthermore, constraints on the sequence can be specified, e.g. one can restrict sequence positions to a fixed nucleotide or to a set of nucleotides. Moreover, the user can allow violations of the constraints at some positions, which can be advantageous in complicated cases. The INFO-RNA web server allows biologists to design RNA sequences in an automatic manner. It is clearly and intuitively arranged and easy to use. The procedure is fast, as most applications are completed within seconds and it proceeds better and faster than other existing tools. The INFO-RNA web server is freely available at http://www.bioinf.uni-freiburg.de/Software/INFO-RNA/

INFO-RNA—a server for fast inverse RNA folding satisfying sequence constraints

PubMed Central

Busch, Anke; Backofen, Rolf

2007-01-01

INFO-RNA is a new web server for designing RNA sequences that fold into a user given secondary structure. Furthermore, constraints on the sequence can be specified, e.g. one can restrict sequence positions to a fixed nucleotide or to a set of nucleotides. Moreover, the user can allow violations of the constraints at some positions, which can be advantageous in complicated cases. The INFO-RNA web server allows biologists to design RNA sequences in an automatic manner. It is clearly and intuitively arranged and easy to use. The procedure is fast, as most applications are completed within seconds and it proceeds better and faster than other existing tools. The INFO-RNA web server is freely available at http://www.bioinf.uni-freiburg.de/Software/INFO-RNA/ PMID:17452349

Fast and Robust Registration of Multimodal Remote Sensing Images via Dense Orientated Gradient Feature

NASA Astrophysics Data System (ADS)

Ye, Y.

2017-09-01

This paper presents a fast and robust method for the registration of multimodal remote sensing data (e.g., optical, LiDAR, SAR and map). The proposed method is based on the hypothesis that structural similarity between images is preserved across different modalities. In the definition of the proposed method, we first develop a pixel-wise feature descriptor named Dense Orientated Gradient Histogram (DOGH), which can be computed effectively at every pixel and is robust to non-linear intensity differences between images. Then a fast similarity metric based on DOGH is built in frequency domain using the Fast Fourier Transform (FFT) technique. Finally, a template matching scheme is applied to detect tie points between images. Experimental results on different types of multimodal remote sensing images show that the proposed similarity metric has the superior matching performance and computational efficiency than the state-of-the-art methods. Moreover, based on the proposed similarity metric, we also design a fast and robust automatic registration system for multimodal images. This system has been evaluated using a pair of very large SAR and optical images (more than 20000 × 20000 pixels). Experimental results show that our system outperforms the two popular commercial software systems (i.e. ENVI and ERDAS) in both registration accuracy and computational efficiency.

Targeted sequencing of plant genomes

Treesearch

Mark D. Huynh

2014-01-01

Next-generation sequencing (NGS) has revolutionized the field of genetics by providing a means for fast and relatively affordable sequencing. With the advancement of NGS, wholegenome sequencing (WGS) has become more commonplace. However, sequencing an entire genome is still not cost effective or even beneficial in all cases. In studies that do not require a whole-...

Assessment of inflammatory activity in Crohn's disease by means of dynamic contrast-enhanced MRI.

PubMed

Pupillo, V A; Di Cesare, E; Frieri, G; Limbucci, N; Tanga, M; Masciocchi, C

2007-09-01

Our aim was to perform a dynamic study of contrast enhancement of the intestinal wall in patients with Crohn's disease to quantitatively assess local inflammatory activity. We studied a population of 50 patients with histologically proven Crohn's disease. Magnetic resonance imaging (MRI) was performed using a 1.5-T magnet with a phased-array coil and acquisition of T2-weighted single-shot fast spin echo (SSFSE) half Fourier sequences before intravenous administration of gadolinium, and T1-weighted fast spoiled gradient (FSPGR) fat-saturated sequences before and after contrast administration. Before the examination, patents received oral polyethylene glycol (PEG) (1,000 ml for adults; 10 ml/Kg of body weight for children). Regions of interest (ROI) were placed on the normal and diseased intestinal wall to assess signal intensity and rate of increase in contrast enhancement over time. Data were compared with the Crohn's Disease Activity Index (CDAI). The diseased bowel wall showed early and intense uptake of contrast that increases over time until a plateau is reached. In patients in the remission phase after treatment, signal intensity was only slightly higher in diseased bowel loops than in healthy loops. There was a significant correlation between the peak of contrast uptake and CDAI. Dynamic MRI is a good technique for quantifying local inflammatory activity of bowel wall in patients with Crohn's disease.

Fast online and index-based algorithms for approximate search of RNA sequence-structure patterns

PubMed Central

2013-01-01

Background It is well known that the search for homologous RNAs is more effective if both sequence and structure information is incorporated into the search. However, current tools for searching with RNA sequence-structure patterns cannot fully handle mutations occurring on both these levels or are simply not fast enough for searching large sequence databases because of the high computational costs of the underlying sequence-structure alignment problem. Results We present new fast index-based and online algorithms for approximate matching of RNA sequence-structure patterns supporting a full set of edit operations on single bases and base pairs. Our methods efficiently compute semi-global alignments of structural RNA patterns and substrings of the target sequence whose costs satisfy a user-defined sequence-structure edit distance threshold. For this purpose, we introduce a new computing scheme to optimally reuse the entries of the required dynamic programming matrices for all substrings and combine it with a technique for avoiding the alignment computation of non-matching substrings. Our new index-based methods exploit suffix arrays preprocessed from the target database and achieve running times that are sublinear in the size of the searched sequences. To support the description of RNA molecules that fold into complex secondary structures with multiple ordered sequence-structure patterns, we use fast algorithms for the local or global chaining of approximate sequence-structure pattern matches. The chaining step removes spurious matches from the set of intermediate results, in particular of patterns with little specificity. In benchmark experiments on the Rfam database, our improved online algorithm is faster than the best previous method by up to factor 45. Our best new index-based algorithm achieves a speedup of factor 560. Conclusions The presented methods achieve considerable speedups compared to the best previous method. This, together with the expected sublinear running time of the presented index-based algorithms, allows for the first time approximate matching of RNA sequence-structure patterns in large sequence databases. Beyond the algorithmic contributions, we provide with RaligNAtor a robust and well documented open-source software package implementing the algorithms presented in this manuscript. The RaligNAtor software is available at http://www.zbh.uni-hamburg.de/ralignator. PMID:23865810

Gradient-Modulated SWIFT

PubMed Central

Zhang, Jinjin; Idiyatullin, Djaudat; Corum, Curtis A.; Kobayashi, Naoharu; Garwood, Michael

2017-01-01

Purpose Methods designed to image fast-relaxing spins, such as sweep imaging with Fourier transformation (SWIFT), often utilize high excitation bandwidth and duty cycle, and in some applications the optimal flip angle cannot be used without exceeding safe specific absorption rate (SAR) levels. The aim is to reduce SAR and increase the flexibility of SWIFT by applying time-varying gradient-modulation (GM). The modified sequence is called GM-SWIFT. Theory and Methods The method known as gradient-modulated offset independent adiabaticity was used to modulate the radiofrequency (RF) pulse and gradients. An expanded correlation algorithm was developed for GM-SWIFT to correct the phase and scale effects. Simulations and phantom and in vivo human experiments were performed to verify the correlation algorithm and to evaluate imaging performance. Results GM-SWIFT reduces SAR, RF amplitude, and acquisition time by up to 90%, 70%, and 45%, respectively, while maintaining image quality. The choice of GM parameter influences the lower limit of short T2* sensitivity, which can be exploited to suppress unwanted image haze from unresolvable ultrashort T2* signals originating from plastic materials in the coil housing and fixatives. Conclusions GM-SWIFT reduces peak and total RF power requirements and provides additional flexibility for optimizing SAR, RF amplitude, scan time, and image quality. PMID:25800547

Effect of time discretization of the imaging process on the accuracy of trajectory estimation in fluorescence microscopy

PubMed Central

Wong, Yau; Chao, Jerry; Lin, Zhiping; Ober, Raimund J.

2014-01-01

In fluorescence microscopy, high-speed imaging is often necessary for the proper visualization and analysis of fast subcellular dynamics. Here, we examine how the speed of image acquisition affects the accuracy with which parameters such as the starting position and speed of a microscopic non-stationary fluorescent object can be estimated from the resulting image sequence. Specifically, we use a Fisher information-based performance bound to investigate the detector-dependent effect of frame rate on the accuracy of parameter estimation. We demonstrate that when a charge-coupled device detector is used, the estimation accuracy deteriorates as the frame rate increases beyond a point where the detector’s readout noise begins to overwhelm the low number of photons detected in each frame. In contrast, we show that when an electron-multiplying charge-coupled device (EMCCD) detector is used, the estimation accuracy improves with increasing frame rate. In fact, at high frame rates where the low number of photons detected in each frame renders the fluorescent object difficult to detect visually, imaging with an EMCCD detector represents a natural implementation of the Ultrahigh Accuracy Imaging Modality, and enables estimation with an accuracy approaching that which is attainable only when a hypothetical noiseless detector is used. PMID:25321248

Increasing spatial resolution and comparison of MR imaging sequences for the inner ear

NASA Astrophysics Data System (ADS)

Snyder, Carl J.; Bolinger, Lizann; Rubinstein, Jay T.; Wang, Ge

2002-04-01

The size and location of the cochlea and cochlear nerve are needed to assess the feasibility of cochlea implantation, provide information for surgical planning, and aid in construction of cochlear models. Models of implant stimulation incorporating anatomical and physiological information are likely to provide a better understanding of the biophysics of information transferred with cochlear implants and aid in electrode design and arrangement on cochlear implants. Until recently MR did not provide the necessary image resolution and suffered from long acquisition times. The purpose of this study was to optimize both Fast Spin Echo (FSE) and Steady State Free Precession (FIESTA) imaging scan parameters for the inner ear and comparatively examine both for improved image quality and increased spatial resolution. Image quality was determined by two primary measurements, signal to noise ratio (SNR), and image sharpness. Optimized parameters for FSE were 120ms, 3000ms, 64, and 32.25kHz for the TE, TR, echo train length, and bandwidth, respectively. FIESTA parameters were optimized to 2.7, 5.5ms, 70 degree(s), and 62.5kHz, for TE, TR, flip angle, and bandwidth, respectively. While both had the same in-plane spatial resolution, 0.625mm, FIESTA data shows higher SNR per acquisition time and better edge sharpness.

Sci-Thur PM - Colourful Interactions: Highlights 04: A Fast Quantitative MRI Acquisition and Processing Pipeline for Radiation Treatment Planning and Simulation

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

Jutras, Jean-David

MRI-only Radiation Treatment Planning (RTP) is becoming increasingly popular because of a simplified work-flow, and less inconvenience to the patient who avoids multiple scans. The advantages of MRI-based RTP over traditional CT-based RTP lie in its superior soft-tissue contrast, and absence of ionizing radiation dose. The lack of electron-density information in MRI can be addressed by automatic tissue classification. To distinguish bone from air, which both appear dark in MRI, an ultra-short echo time (UTE) pulse sequence may be used. Quantitative MRI parametric maps can provide improved tissue segmentation/classification and better sensitivity in monitoring disease progression and treatment outcome thanmore » standard weighted images. Superior tumor contrast can be achieved on pure T{sub 1} images compared to conventional T{sub 1}-weighted images acquired in the same scan duration and voxel resolution. In this study, we have developed a robust and fast quantitative MRI acquisition and post-processing work-flow that integrates these latest advances into the MRI-based RTP of brain lesions. Using 3D multi-echo FLASH images at two different optimized flip angles (both acquired in under 9 min, and 1mm isotropic resolution), parametric maps of T{sub 1}, proton-density (M{sub 0}), and T{sub 2}{sup *} are obtained with high contrast-to-noise ratio, and negligible geometrical distortions, water-fat shifts and susceptibility effects. An additional 3D UTE MRI dataset is acquired (in under 4 min) and post-processed to classify tissues for dose simulation. The pipeline was tested on four healthy volunteers and a clinical trial on brain cancer patients is underway.« less

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

Larsen, M.J.; Klingensmith, W.C. III; Kuni, C.C.

Radionuclide hepatobiliary imaging demonstrated nonvisualization of the gallbladder in four patients who were studied after fasting from 14 hr to 12 days. Two patients subsequently had normal gallbladders at autopsy, and two gave normal gallbladder visualization on repeat imaging studies after fasts of 2 to 3 hr. These findings suggest that prolonged fasting may be a cause for nonvisualization of a normal gallbladder.

Value of MR contrast media in image-guided body interventions.

PubMed

Saeed, Maythem; Wilson, Mark

2012-01-28

In the past few years, there have been multiple advances in magnetic resonance (MR) instrumentation, in vivo devices, real-time imaging sequences and interventional procedures with new therapies. More recently, interventionists have started to use minimally invasive image-guided procedures and local therapies, which reduce the pain from conventional surgery and increase drug effectiveness, respectively. Local therapy also reduces the systemic dose and eliminates the toxic side effects of some drugs to other organs. The success of MR-guided procedures depends on visualization of the targets in 3D and precise deployment of ablation catheters, local therapies and devices. MR contrast media provide a wealth of tissue contrast and allows 3D and 4D image acquisitions. After the development of fast imaging sequences, the clinical applications of MR contrast media have been substantially expanded to include pre- during- and post-interventions. Prior to intervention, MR contrast media have the potential to localize and delineate pathologic tissues of vital organs, such as the brain, heart, breast, kidney, prostate, liver and uterus. They also offer other options such as labeling therapeutic agents or cells. During intervention, these agents have the capability to map blood vessels and enhance the contrast between the endovascular guidewire/catheters/devices, blood and tissues as well as direct therapies to the target. Furthermore, labeling therapeutic agents or cells aids in visualizing their delivery sites and tracking their tissue distribution. After intervention, MR contrast media have been used for assessing the efficacy of ablation and therapies. It should be noted that most image-guided procedures are under preclinical research and development. It can be concluded that MR contrast media have great value in preclinical and some clinical interventional procedures. Future applications of MR contrast media in image-guided procedures depend on their safety, tolerability, tissue specificity and effectiveness in demonstrating success of the interventions and therapies.

'DNA Strider': a 'C' program for the fast analysis of DNA and protein sequences on the Apple Macintosh family of computers.

PubMed Central

Marck, C

1988-01-01

DNA Strider is a new integrated DNA and Protein sequence analysis program written with the C language for the Macintosh Plus, SE and II computers. It has been designed as an easy to learn and use program as well as a fast and efficient tool for the day-to-day sequence analysis work. The program consists of a multi-window sequence editor and of various DNA and Protein analysis functions. The editor may use 4 different types of sequences (DNA, degenerate DNA, RNA and one-letter coded protein) and can handle simultaneously 6 sequences of any type up to 32.5 kB each. Negative numbering of the bases is allowed for DNA sequences. All classical restriction and translation analysis functions are present and can be performed in any order on any open sequence or part of a sequence. The main feature of the program is that the same analysis function can be repeated several times on different sequences, thus generating multiple windows on the screen. Many graphic capabilities have been incorporated such as graphic restriction map, hydrophobicity profile and the CAI plot- codon adaptation index according to Sharp and Li. The restriction sites search uses a newly designed fast hexamer look-ahead algorithm. Typical runtime for the search of all sites with a library of 130 restriction endonucleases is 1 second per 10,000 bases. The circular graphic restriction map of the pBR322 plasmid can be therefore computed from its sequence and displayed on the Macintosh Plus screen within 2 seconds and its multiline restriction map obtained in a scrolling window within 5 seconds. PMID:2832831

Probabilistic Motor Sequence Yields Greater Offline and Less Online Learning than Fixed Sequence

PubMed Central

Du, Yue; Prashad, Shikha; Schoenbrun, Ilana; Clark, Jane E.

2016-01-01

It is well acknowledged that motor sequences can be learned quickly through online learning. Subsequently, the initial acquisition of a motor sequence is boosted or consolidated by offline learning. However, little is known whether offline learning can drive the fast learning of motor sequences (i.e., initial sequence learning in the first training session). To examine offline learning in the fast learning stage, we asked four groups of young adults to perform the serial reaction time (SRT) task with either a fixed or probabilistic sequence and with or without preliminary knowledge (PK) of the presence of a sequence. The sequence and PK were manipulated to emphasize either procedural (probabilistic sequence; no preliminary knowledge (NPK)) or declarative (fixed sequence; with PK) memory that were found to either facilitate or inhibit offline learning. In the SRT task, there were six learning blocks with a 2 min break between each consecutive block. Throughout the session, stimuli followed the same fixed or probabilistic pattern except in Block 5, in which stimuli appeared in a random order. We found that PK facilitated the learning of a fixed sequence, but not a probabilistic sequence. In addition to overall learning measured by the mean reaction time (RT), we examined the progressive changes in RT within and between blocks (i.e., online and offline learning, respectively). It was found that the two groups who performed the fixed sequence, regardless of PK, showed greater online learning than the other two groups who performed the probabilistic sequence. The groups who performed the probabilistic sequence, regardless of PK, did not display online learning, as indicated by a decline in performance within the learning blocks. However, they did demonstrate remarkably greater offline improvement in RT, which suggests that they are learning the probabilistic sequence offline. These results suggest that in the SRT task, the fast acquisition of a motor sequence is driven by concurrent online and offline learning. In addition, as the acquisition of a probabilistic sequence requires greater procedural memory compared to the acquisition of a fixed sequence, our results suggest that offline learning is more likely to take place in a procedural sequence learning task. PMID:26973502

Probabilistic Motor Sequence Yields Greater Offline and Less Online Learning than Fixed Sequence.

PubMed

Du, Yue; Prashad, Shikha; Schoenbrun, Ilana; Clark, Jane E

2016-01-01

It is well acknowledged that motor sequences can be learned quickly through online learning. Subsequently, the initial acquisition of a motor sequence is boosted or consolidated by offline learning. However, little is known whether offline learning can drive the fast learning of motor sequences (i.e., initial sequence learning in the first training session). To examine offline learning in the fast learning stage, we asked four groups of young adults to perform the serial reaction time (SRT) task with either a fixed or probabilistic sequence and with or without preliminary knowledge (PK) of the presence of a sequence. The sequence and PK were manipulated to emphasize either procedural (probabilistic sequence; no preliminary knowledge (NPK)) or declarative (fixed sequence; with PK) memory that were found to either facilitate or inhibit offline learning. In the SRT task, there were six learning blocks with a 2 min break between each consecutive block. Throughout the session, stimuli followed the same fixed or probabilistic pattern except in Block 5, in which stimuli appeared in a random order. We found that PK facilitated the learning of a fixed sequence, but not a probabilistic sequence. In addition to overall learning measured by the mean reaction time (RT), we examined the progressive changes in RT within and between blocks (i.e., online and offline learning, respectively). It was found that the two groups who performed the fixed sequence, regardless of PK, showed greater online learning than the other two groups who performed the probabilistic sequence. The groups who performed the probabilistic sequence, regardless of PK, did not display online learning, as indicated by a decline in performance within the learning blocks. However, they did demonstrate remarkably greater offline improvement in RT, which suggests that they are learning the probabilistic sequence offline. These results suggest that in the SRT task, the fast acquisition of a motor sequence is driven by concurrent online and offline learning. In addition, as the acquisition of a probabilistic sequence requires greater procedural memory compared to the acquisition of a fixed sequence, our results suggest that offline learning is more likely to take place in a procedural sequence learning task.

New Aspects of a Lid-Removal Mechanism in the Onset of a SEP-Producing Eruption Sequence

NASA Technical Reports Server (NTRS)

Sterling, Alphonse C.; Moore, Ronald L.; Falconer, David A.; Knox, Javon M.

2014-01-01

We examine a sequence of two ejective eruptions from a single active region on 2012 January 23, using magnetograms and EUV images from SDO/HMI and SDO/AIA, and EUV images from STEREO. Cheng et al. (2013) showed that the first eruption's ("Eruption 1'') flux rope was apparent only in "hotter'' AIA channels, and that it removed overlying field that allowed the second eruption (``Eruption 2'') to begin via ideal MHD instability; here we say Eruption 2 began via a ``lid removal'' mechanism. We show that during Eruption-1's onset, its flux rope underwent ``tether weakening'' (TW) reconnection with the field of an adjacent active region. Standard flare loops from Eruption 1 developed over Eruption-2's flux rope and enclosed filament, but these overarching new loops were unable to confine that flux rope/filament. Eruption-1's flare loops, from both TW reconnection and standard-flare-model internal reconnection, were much cooler than Eruption-2's flare loops (GOES thermal temperatures of approx. 9 MK compared to approx. 14 MK). This eruption sequence produced a strong solar energetic particle (SEP) event (10 MeV protons, >10(exp 3) pfu for 43 hrs), apparently starting when Eruption-2's CME blasted through Eruption-1's CME at 5-10 R_s. This occurred because the two CMEs originated in close proximity and in close time sequence: Eruption-1's fast rise started soon after the TW reconnection; the lid removal by Eruption-1's ejection triggered the slow onset of Eruption 2; and Eruption-2's CME, which started approx. 1 hr later, was three times faster than Eruption-1's CME.

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.

FastRNABindR: Fast and Accurate Prediction of Protein-RNA Interface Residues.

PubMed

El-Manzalawy, Yasser; Abbas, Mostafa; Malluhi, Qutaibah; Honavar, Vasant

2016-01-01

A wide range of biological processes, including regulation of gene expression, protein synthesis, and replication and assembly of many viruses are mediated by RNA-protein interactions. However, experimental determination of the structures of protein-RNA complexes is expensive and technically challenging. Hence, a number of computational tools have been developed for predicting protein-RNA interfaces. Some of the state-of-the-art protein-RNA interface predictors rely on position-specific scoring matrix (PSSM)-based encoding of the protein sequences. The computational efforts needed for generating PSSMs severely limits the practical utility of protein-RNA interface prediction servers. In this work, we experiment with two approaches, random sampling and sequence similarity reduction, for extracting a representative reference database of protein sequences from more than 50 million protein sequences in UniRef100. Our results suggest that random sampled databases produce better PSSM profiles (in terms of the number of hits used to generate the profile and the distance of the generated profile to the corresponding profile generated using the entire UniRef100 data as well as the accuracy of the machine learning classifier trained using these profiles). Based on our results, we developed FastRNABindR, an improved version of RNABindR for predicting protein-RNA interface residues using PSSM profiles generated using 1% of the UniRef100 sequences sampled uniformly at random. To the best of our knowledge, FastRNABindR is the only protein-RNA interface residue prediction online server that requires generation of PSSM profiles for query sequences and accepts hundreds of protein sequences per submission. Our approach for determining the optimal BLAST database for a protein-RNA interface residue classification task has the potential of substantially speeding up, and hence increasing the practical utility of, other amino acid sequence based predictors of protein-protein and protein-DNA interfaces.

Autologous chondrocyte implantation in knee joint: MR imaging and histologic features at 1-year follow-up.

PubMed

Tins, Bernhard J; McCall, Iain W; Takahashi, Tomoki; Cassar-Pullicino, Victor; Roberts, Sally; Ashton, Brian; Richardson, James

2005-02-01

To evaluate magnetic resonance (MR) imaging features of autologous chondrocyte implantation (ACI) grafts and compare these with graft histologic features 1 year after ACI for treatment of femoral condylar defects. This study was approved by the regional ethics committee, and all patients gave informed consent. Forty-one patients (mean age, 35 years; 30 men, 11 women) underwent ACI for treatment of femoral condylar defects. One year later, knee joint MR imaging and graft biopsy were performed. Graft biopsy results were categorized into those showing hyaline, mixed fibrohyaline cartilage, fibrocartilage, and fibrous tissue. Standard T1-, T2-, T2*-, and intermediate-weighted sequences were performed, as well as three-dimensional (3D) fast low-angle shot (FLASH) and double-echo steady-state sequences for cartilage assessment. ACI grafts were assessed for signal intensity (with FLASH sequence), thickness, overgrowth, surface smoothness, integration to adjacent cartilage and underlying bone, bone marrow edema underneath graft, and contour of bone underneath graft. MR images were assessed by two observers, first independently and then in consensus. MR imaging findings were correlated with histologic findings. All 41 grafts were present at 1-year follow-up. The graft consisted of hyaline cartilage in four, mixed fibrohyaline cartilage in 10, fibrocartilage in 25, and fibrous tissue in two cases. Graft signal intensity was virtually always lower than adjacent normal cartilage signal intensity, and there was no relationship between graft signal intensity and histologic appearance (P = .34). Graft thickness (P = .83), overgrowth (P = .69), surface smoothness (P = .28), and integration with adjacent cartilage and underlying bone (P = .90); edema in bone marrow underneath graft (P = .63); and bone contour underneath graft (P = .94) at MR imaging had no correlation with graft histologic appearance. Graft overgrowth (n = 16; 39%) and edema-like signal in bone marrow underneath graft (n = 23; 56%) were common. The origin of graft overgrowth remains unclear. With the methods presented here, MR imaging findings cannot predict ACI graft histologic features, and graft histologic appearance determined at biopsy was not related to graft signal intensity, graft thickness, overgrowth, surface smoothness, integration with adjacent cartilage or underlying bone, signal intensity change in underlying bone marrow, or underlying bone contour. Overgrowth and bone marrow changes underneath the graft were common. (c) RSNA, 2004.

SU-E-J-217: Multiparametric MR Imaging of Cranial Tumors On a Dedicated 1.0T MR Simulator Prior to Stereotactic Radiosurgery

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

Wen, N; Glide-Hurst, C; Liu, M

Purpose: Quantitative magnetic resonance imaging (MRI) of cranial lesions prior to stereotactic radiosurgery (SRS) may improve treatment planning and provide potential prognostic value. The practicality and logistics of acquiring advanced multiparametric MRI sequences to measure vascular and cellular properties of cerebral tumors are explored on a 1.0 Tesla MR Simulator. Methods: MR simulation was performed immediately following routine CT simulation on a 1T MR Simulator. MR sequences used were in the order they were performed: T2-Weighted Turbo Spin Echo (T2W-TSE), T2 FLAIR, Diffusion-weighted (DWI, b = 0, 800 to generate an apparent diffusion coefficient (ADC) map), 3D T1-Weighted Fast Fieldmore » Echo (T1W-FFE), Dynamic Contrast Enhanced (DCE) and Post Gadolinium Contrast Enhanced 3D T1W-FFE images. T1 pre-contrast values was generated by acquiring six different flip angles. The arterial input function was derived from arterial pixels in the perfusion images selected manually. The extended Tofts model was used to generate the permeability maps. Routine MRI scans took about 30 minutes to complete; the additional scans added 12 minutes. Results: To date, seven patients with cerebral tumors have been imaged and tumor physiology characterized. For example, on a glioblastoma patient, the volume contoured on T1 Gd images, ADC map and the pharmacokinetic map (Ktrans) were 1.9, 1.4, and 1.5 cc respectively with strong spatial correlation. The mean ADC value of the entire volume was 1141 μm2/s while the value in the white matter was 811 μm2/s. The mean value of Ktrans was 0.02 min-1 in the tumor volume and 0.00 in the normal white matter. Conclusion: Our initial results suggest that multiparametric MRI sequences may provide a more quantitative evaluation of vascular and tumor properties. Implementing functional imaging during MR-SIM may be particularly beneficial in assessing tumor extent, differentiating radiation necrosis from tumor recurrence, and establishing reliable bio-markers for treatment response evaluation. The Department of Radiation Oncology at Henry Ford Health System has research agreement with Varian Medical System and Philips Health Care.« less

Quantitative Imaging in Laboratory: Fast Kinetics and Fluorescence Quenching

ERIC Educational Resources Information Center

Cumberbatch, Tanya; Hanley, Quentin S.

2007-01-01

The process of quantitative imaging, which is very commonly used in laboratory, is shown to be very useful for studying the fast kinetics and fluorescence quenching of many experiments. The imaging technique is extremely cheap and hence can be used in many absorption and luminescence experiments.

FastID: Extremely Fast Forensic DNA Comparisons

DTIC Science & Technology

2017-05-19

FastID: Extremely Fast Forensic DNA Comparisons Darrell O. Ricke, PhD Bioengineering Systems & Technologies Massachusetts Institute of...Technology Lincoln Laboratory Lexington, MA USA Darrell.Ricke@ll.mit.edu Abstract—Rapid analysis of DNA forensic samples can have a critical impact on...time sensitive investigations. Analysis of forensic DNA samples by massively parallel sequencing is creating the next gold standard for DNA

SU-D-18C-01: A Novel 4D-MRI Technology Based On K-Space Retrospective Sorting

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

Liu, Y; Yin, F; Cai, J

2014-06-01

Purpose: Current 4D-MRI techniques lack sufficient temporal/spatial resolution and consistent tumor contrast. To overcome these limitations, this study presents the development and initial evaluation of an entirely new framework of 4D-MRI based on k-space retrospective sorting. Methods: An important challenge of the proposed technique is to determine the number of repeated scans(NR) required to obtain sufficient k-space data for 4D-MRI. To do that, simulations using 29 cancer patients' respiratory profiles were performed to derive the relationship between data acquisition completeness(Cp) and NR, also relationship between NR(Cp=95%) and the following factors: total slice(NS), respiratory phase bin length(Lb), frame rate(fr), resolution(R) andmore » image acquisition starting-phase(P0). To evaluate our technique, a computer simulation study on a 4D digital human phantom (XCAT) were conducted with regular breathing (fr=0.5Hz; R=256×256). A 2D echo planer imaging(EPI) MRI sequence were assumed to acquire raw k-space data, with respiratory signal and acquisition time for each k-space data line recorded simultaneously. K-space data was re-sorted based on respiratory phases. To evaluate 4D-MRI image quality, tumor trajectories were measured and compared with the input signal. Mean relative amplitude difference(D) and cross-correlation coefficient(CC) are calculated. Finally, phase-sharing sliding window technique was applied to investigate the feasibility of generating ultra-fast 4D-MRI. Result: Cp increased with NR(Cp=100*[1-exp(-0.19*NR)], when NS=30, Lb=100%/6). NR(Cp=95%) was inversely-proportional to Lb (r=0.97), but independent of other factors. 4D-MRI on XCAT demonstrated highly accurate motion information (D=0.67%, CC=0.996) with much less artifacts than those on image-based sorting 4D-MRI. Ultra-fast 4D-MRI with an apparent temporal resolution of 10 frames/second was reconstructed using the phase-sharing sliding window technique. Conclusions: A novel 4D-MRI technology based on k-space sorting has been successfully developed and evaluated on the digital phantom. Framework established can be applied to a variety of MR sequences, showing great promises to develop the optimal 4D-MRI technique for many radiation therapy applications. NIH (1R21CA165384-01A1)« less

SU-G-JeP2-14: MRI-Based HDR Prostate Brachytherapy: A Phantom Study for Interstitial Catheter Reconstruction with 0.35T MRI Images

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

Park, S; Kamrava, M; Yang, Y

Purpose: To evaluate the accuracy of interstitial catheter reconstruction with 0.35T MRI images for MRI-based HDR prostate brachytherapy. Methods: Recently, a real-time MRI-guided radiotherapy system combining a 0.35T MRI system and three cobalt 60 heads (MRIdian System, ViewRay, Cleveland, OH, USA) was installed in our department. A TrueFISP sequence for MRI acquisition at lower field on Viewray was chosen due to its fast speed and high signal-to-noise efficiency. Interstitial FlexiGuide needles were implanted into a tissue equivalent ultrasound prostate phantom (CIRS, Norfolk, Virginia, USA). After an initial 15s pilot MRI to confirm the location of the phantom, planning MRI wasmore » acquired with a 172s TrueFISP sequence. The pulse sequence parameters included: flip angle = 60 degree, echo time (TE) =1.45 ms, repetition time (TR) = 3.37 ms, slice thickness = 1.5 mm, field of view (FOV) =500 × 450mm. For a reference image, a CT scan was followed. The CT and MR scans were then fused with the MIM Maestro (MIM software Inc., Cleveland, OH, USA) and sent to the Oncentra Brachy planning system (Elekta, Veenendaal, Netherlands). Automatic catheter reconstruction using CT and MR image intensities followed by manual reconstruction was used to digitize catheters. The accuracy of catheter reconstruction was evaluated from the catheter tip location. Results: The average difference between the catheter tip locations reconstructed from the CT and MR in the transverse, anteroposterior, and craniocaudal directions was −0.1 ± 0.1 mm (left), 0.2 ± 0.2 mm (anterior), and −2.3 ± 0.5 mm (cranio). The average distance in 3D was 2.3 mm ± 0.5 mm. Conclusion: This feasibility study proved that interstitial catheters can be reconstructed with 0.35T MRI images. For more accurate catheter reconstruction which can affect final dose distribution, a systematic shift should be applied to the MR based catheter reconstruction in HDR prostate brachytherapy.« less

Design and evaluation of an air traffic control Final Approach Spacing Tool

NASA Technical Reports Server (NTRS)

Davis, Thomas J.; Erzberger, Heinz; Green, Steven M.; Nedell, William

1991-01-01

This paper describes the design and simulator evaluation of an automation tool for assisting terminal radar approach controllers in sequencing and spacing traffic onto the final approach course. The automation tool, referred to as the Final Approach Spacing Tool (FAST), displays speed and heading advisories for arriving aircraft as well as sequencing information on the controller's radar display. The main functional elements of FAST are a scheduler that schedules and sequences the traffic, a four-dimensional trajectory synthesizer that generates the advisories, and a graphical interface that displays the information to the controller. FAST has been implemented on a high-performance workstation. It can be operated as a stand-alone in the terminal radar approach control facility or as an element of a system integrated with automation tools in the air route traffic control center. FAST was evaluated by experienced air traffic controllers in a real-time air traffic control simulation. simulation results summarized in the paper show that the automation tools significantly reduced controller work load and demonstrated a potential for an increase in landing rate.

Algorithm, applications and evaluation for protein comparison by Ramanujan Fourier transform.

PubMed

Zhao, Jian; Wang, Jiasong; Hua, Wei; Ouyang, Pingkai

2015-12-01

The amino acid sequence of a protein determines its chemical properties, chain conformation and biological functions. Protein sequence comparison is of great importance to identify similarities of protein structures and infer their functions. Many properties of a protein correspond to the low-frequency signals within the sequence. Low frequency modes in protein sequences are linked to the secondary structures, membrane protein types, and sub-cellular localizations of the proteins. In this paper, we present Ramanujan Fourier transform (RFT) with a fast algorithm to analyze the low-frequency signals of protein sequences. The RFT method is applied to similarity analysis of protein sequences with the Resonant Recognition Model (RRM). The results show that the proposed fast RFT method on protein comparison is more efficient than commonly used discrete Fourier transform (DFT). RFT can detect common frequencies as significant feature for specific protein families, and the RFT spectrum heat-map of protein sequences demonstrates the information conservation in the sequence comparison. The proposed method offers a new tool for pattern recognition, feature extraction and structural analysis on protein sequences. Copyright © 2015 Elsevier Ltd. All rights reserved.

Fast Lossless Compression of Multispectral-Image Data

NASA Technical Reports Server (NTRS)

Klimesh, Matthew

2006-01-01

An algorithm that effects fast lossless compression of multispectral-image data is based on low-complexity, proven adaptive-filtering algorithms. This algorithm is intended for use in compressing multispectral-image data aboard spacecraft for transmission to Earth stations. Variants of this algorithm could be useful for lossless compression of three-dimensional medical imagery and, perhaps, for compressing image data in general.

Sensitivity of an eight-element phased array coil in 3 Tesla MR imaging: a basic analysis.

PubMed

Hiratsuka, Yoshiyasu; Miki, Hitoshi; Kikuchi, Keiichi; Kiriyama, Ikuko; Mochizuki, Teruhito; Takahashi, Shizue; Sadamoto, Kazuhiko

2007-01-01

To evaluate the performance advantages of an 8-element phased array head coil (8 ch coil) over a conventional quadrature-type birdcage head coil (QD coil) with regard to the signal-to-noise ratio (SNR) and image uniformity in 3 Tesla magnetic resonance (MR) imaging. We scanned a phantom filled with silicon oil using an 8 ch coil and a QD coil in a 3T MR imaging system and compared the SNR and image uniformity obtained from T(1)-weighted spin echo (SE) images and T(2)-weighted fast SE images between the 2 coils. We also visually evaluated images from 4 healthy volunteers. The SNR with the 8 ch coil was approximately twice that with the QD coil in the region of interest (ROI), which was set as 75% of the area in the center of the phantom images. With regard to the spatial variation of sensitivity, the SNR with the 8 ch coil was lower at the center of the images than at the periphery, whereas the SNR with the QD coil exhibited an inverse pattern. At the center of the images with the 8 ch coil, the SNR was somewhat lower, and that distribution was relatively flat compared to that in the periphery. Image uniformity varied less with the 8 ch coil than with the QD coil on both imaging sequences. The 8 ch phased array coil was useful for obtaining high quality 3T images because of its higher SNR and improved image uniformity than those obtained with conventional quadrature-type birdcage head coil.

System Integration of FastSPECT III, a Dedicated SPECT Rodent-Brain Imager Based on BazookaSPECT Detector Technology

PubMed Central

Miller, Brian W.; Furenlid, Lars R.; Moore, Stephen K.; Barber, H. Bradford; Nagarkar, Vivek V.; Barrett, Harrison H.

2010-01-01

FastSPECT III is a stationary, single-photon emission computed tomography (SPECT) imager designed specifically for imaging and studying neurological pathologies in rodent brain, including Alzheimer’s and Parkinsons’s disease. Twenty independent BazookaSPECT [1] gamma-ray detectors acquire projections of a spherical field of view with pinholes selected for desired resolution and sensitivity. Each BazookaSPECT detector comprises a columnar CsI(Tl) scintillator, image-intensifier, optical lens, and fast-frame-rate CCD camera. Data stream back to processing computers via firewire interfaces, and heavy use of graphics processing units (GPUs) ensures that each frame of data is processed in real time to extract the images of individual gamma-ray events. Details of the system design, imaging aperture fabrication methods, and preliminary projection images are presented. PMID:21218137

Principles of Quantitative MR Imaging with Illustrated Review of Applicable Modular Pulse Diagrams.

PubMed

Mills, Andrew F; Sakai, Osamu; Anderson, Stephan W; Jara, Hernan

2017-01-01

Continued improvements in diagnostic accuracy using magnetic resonance (MR) imaging will require development of methods for tissue analysis that complement traditional qualitative MR imaging studies. Quantitative MR imaging is based on measurement and interpretation of tissue-specific parameters independent of experimental design, compared with qualitative MR imaging, which relies on interpretation of tissue contrast that results from experimental pulse sequence parameters. Quantitative MR imaging represents a natural next step in the evolution of MR imaging practice, since quantitative MR imaging data can be acquired using currently available qualitative imaging pulse sequences without modifications to imaging equipment. The article presents a review of the basic physical concepts used in MR imaging and how quantitative MR imaging is distinct from qualitative MR imaging. Subsequently, the article reviews the hierarchical organization of major applicable pulse sequences used in this article, with the sequences organized into conventional, hybrid, and multispectral sequences capable of calculating the main tissue parameters of T1, T2, and proton density. While this new concept offers the potential for improved diagnostic accuracy and workflow, awareness of this extension to qualitative imaging is generally low. This article reviews the basic physical concepts in MR imaging, describes commonly measured tissue parameters in quantitative MR imaging, and presents the major available pulse sequences used for quantitative MR imaging, with a focus on the hierarchical organization of these sequences. © RSNA, 2017.

[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.

Improving whole brain structural MRI at 4.7 Tesla using 4 irregularly shaped receiver coils.

PubMed

Carmichael, David W; Thomas, David L; De Vita, Enrico; Fernández-Seara, Maria A; Chhina, Navjeet; Cooper, Mark; Sunderland, Colin; Randell, Chris; Turner, Robert; Ordidge, Roger J

2006-09-01

Both higher magnetic field strengths (> or =3 T) and multiple receiver "array coils" can provide increased signal-to-noise ratio (SNR) for MRI. This increase in SNR can be used to obtain images with higher resolution, enabling better visualisation of structures within the human brain. However, high field strength systems also suffer from increased B(1) non-uniformity and increased power deposition, reaching specific absorption rate (SAR) limits more quickly. For these problems to be mitigated, a careful choice of both the pulse sequence design and transmit RF coil is required. This paper describes the use of a prototype array coil consisting of 4 irregularly shaped coils within a standard configuration for neuroimaging at 4.7 T (a head transmit/receive volume coil to minimise SAR and a head gradient insert for maximum gradient performance). With a fast spin echo (FSE) pulse sequence optimised for 4.7 T, this provides dramatically increased quality and resolution over a large brain volume. Using the array coil, a SNR improvement relative to the volume coil of 1-1.5 times in central brain areas and 2-3 times in cortical regions was obtained. Array coil images with a resolution of 352 x 352 x 2000 mum had a SNR of 16.0 to 26.2 in central regions and 19.9 to 34.8 in cortical areas. Such images easily demonstrate cortical myeloarchitecture, while still covering most of the brain in a approximately 12 min scan.

Indirect MR lymphangiography of the head and neck using conventional gadolinium contrast: A pilot study in humans

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

Loo, Billy W.; Draney, Mary T.; Sivanandan, Ranjiv

2006-10-01

Purpose: To evaluate indirect magnetic resonance lymphangiography (MR-LAG) using interstitial injection of conventional gadolinium contrast (gadoteridol and gadopentetate dimeglumine) for delineating the primary lymphatic drainage of head-and-neck sites. Methods and Materials: We performed head-and-neck MR-LAG in 5 healthy volunteers, with injection of dermal and mucosal sites. We evaluated the safety of the procedure, the patterns of enhancement categorized by injection site and nodal level, the time course of enhancement, the optimal concentration and volume of contrast, and the optimal imaging sequence. Results: The worst side effects of interstitial contrast injection were brief, mild pain and swelling at the injected sitesmore » that were self-limited. MR-LAG resulted in consistent visualization of the primary lymphatic drainage pattern specific to each injected site, which was reproducible on repeated examinations. The best enhancement was obtained with injection of small volumes (0.3-0.5 mL) of either agent diluted, imaging within 5-15 min of injection, and a three-dimensional fast spoiled gradient echo sequence with magnetization transfer. Conclusions: We found head-and-neck MR-LAG to be a safe, convenient imaging method that provides functional information about the lymphatic drainage of injected sites. Applied to head-and-neck cancer, it has the potential to identify sites at highest risk of occult metastatic spread for radiotherapy or surgical planning, and possibly to visualize micrometastases.« less

Semiempirical studies of atomic structure. Progress report, 1 July 1991--1 October 1993

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

Curtis, L.J.

1993-10-01

Atomic structure/properties of highly ionized many-electron systems are studied using sensitive semiempirical data systematization, experiment, and theory. Measurements are made using fast ion beams, combined with data from laser- and tokamak-produced plasmas, astrophysical sources, and light sources. Results during this 3-y period are discussed under the following headings: Invited review article (decay rates in systems of negative ions to very heavy one-electron ions), fast ion beam lifetime measurements (Pt sequence, neutral carbon, Na sequence), multiplexed decay curve measurements, multiplexed decay curve measurements (lifetimes of alkali-like resonance transitions, spin-forbidden intercombination lines), lifetimes in Ne sequence, lifetimes for H and He sequences,more » data-based semiempirical formulations, calculations, and accelerator studies.« less

Development of a fusion approach selection tool

NASA Astrophysics Data System (ADS)

Pohl, C.; Zeng, Y.

2015-06-01

During the last decades number and quality of available remote sensing satellite sensors for Earth observation has grown significantly. The amount of available multi-sensor images along with their increased spatial and spectral resolution provides new challenges to Earth scientists. With a Fusion Approach Selection Tool (FAST) the remote sensing community would obtain access to an optimized and improved image processing technology. Remote sensing image fusion is a mean to produce images containing information that is not inherent in the single image alone. In the meantime the user has access to sophisticated commercialized image fusion techniques plus the option to tune the parameters of each individual technique to match the anticipated application. This leaves the operator with an uncountable number of options to combine remote sensing images, not talking about the selection of the appropriate images, resolution and bands. Image fusion can be a machine and time-consuming endeavour. In addition it requires knowledge about remote sensing, image fusion, digital image processing and the application. FAST shall provide the user with a quick overview of processing flows to choose from to reach the target. FAST will ask for available images, application parameters and desired information to process this input to come out with a workflow to quickly obtain the best results. It will optimize data and image fusion techniques. It provides an overview on the possible results from which the user can choose the best. FAST will enable even inexperienced users to use advanced processing methods to maximize the benefit of multi-sensor image exploitation.

Molecular Population Genetics of the Alcohol Dehydrogenase Gene Region of DROSOPHILA MELANOGASTER

PubMed Central

Aquadro, Charles F.; Desse, Susan F.; Bland, Molly M.; Langley, Charles H.; Laurie-Ahlberg, Cathy C.

1986-01-01

Variation in the DNA restriction map of a 13-kb region of chromosome II including the alcohol dehydrogenase structural gene (Adh) was examined in Drosophila melanogaster from natural populations. Detailed analysis of 48 D. melanogaster lines representing four eastern United States populations revealed extensive DNA sequence variation due to base substitutions, insertions and deletions. Cloning of this region from several lines allowed characterization of length variation as due to unique sequence insertions or deletions [nine sizes; 21–200 base pairs (bp)] or transposable element insertions (several sizes, 340 bp to 10.2 kb, representing four different elements). Despite this extensive variation in sequences flanking the Adh gene, only one length polymorphism is clearly associated with altered Adh expression (a copia element approximately 250 bp 5' to the distal transcript start site). Nonetheless, the frequency spectra of transposable elements within and between Drosophila species suggests they are slightly deleterious. Strong nonrandom associations are observed among Adh region sequence variants, ADH allozyme (Fast vs. Slow), ADH enzyme activity and the chromosome inversion ln(2L) t. Phylogenetic analysis of restriction map haplotypes suggest that the major twofold component of ADH activity variation (high vs. low, typical of Fast and Slow allozymes, respectively) is due to sequence variation tightly linked to and possibly distinct from that underlying the allozyme difference. The patterns of nucleotide and haplotype variation for Fast and Slow allozyme lines are consistent with the recent increase in frequency and spread of the Fast haplotype associated with high ADH activity. These data emphasize the important role of evolutionary history and strong nonrandom associations among tightly linked sequence variation as determinants of the patterns of variation observed in natural populations. PMID:3026893

FAST: framework for heterogeneous medical image computing and visualization.

PubMed

Smistad, Erik; Bozorgi, Mohammadmehdi; Lindseth, Frank

2015-11-01

Computer systems are becoming increasingly heterogeneous in the sense that they consist of different processors, such as multi-core CPUs and graphic processing units. As the amount of medical image data increases, it is crucial to exploit the computational power of these processors. However, this is currently difficult due to several factors, such as driver errors, processor differences, and the need for low-level memory handling. This paper presents a novel FrAmework for heterogeneouS medical image compuTing and visualization (FAST). The framework aims to make it easier to simultaneously process and visualize medical images efficiently on heterogeneous systems. FAST uses common image processing programming paradigms and hides the details of memory handling from the user, while enabling the use of all processors and cores on a system. The framework is open-source, cross-platform and available online. Code examples and performance measurements are presented to show the simplicity and efficiency of FAST. The results are compared to the insight toolkit (ITK) and the visualization toolkit (VTK) and show that the presented framework is faster with up to 20 times speedup on several common medical imaging algorithms. FAST enables efficient medical image computing and visualization on heterogeneous systems. Code examples and performance evaluations have demonstrated that the toolkit is both easy to use and performs better than existing frameworks, such as ITK and VTK.

High-contrast fast Fourier transform acousto-optical tomography of phantom tissues with a frequency-chirp modulation of the ultrasound.

PubMed

Forget, Benoît-Claude; Ramaz, François; Atlan, Michaël; Selb, Juliette; Boccara, Albert-Claude

2003-03-01

We report new results on acousto-optical tomography in phantom tissues using a frequency chirp modulation and a CCD camera. This technique allows quick recording of three-dimensional images of the optical contrast with a two-dimensional scan of the ultrasound source in a plane perpendicular to the ultrasonic path. The entire optical contrast along the ultrasonic path is concurrently obtained from the capture of a film sequence at a rate of 200 Hz. This technique reduces the acquisition time, and it enhances the axial resolution and thus the contrast, which are usually poor owing to the large volume of interaction of the ultrasound perturbation.

Extreme ultra-violet movie camera for imaging microsecond time scale magnetic reconnection

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

Chai, Kil-Byoung; Bellan, Paul M.

2013-12-15

An ultra-fast extreme ultra-violet (EUV) movie camera has been developed for imaging magnetic reconnection in the Caltech spheromak/astrophysical jet experiment. The camera consists of a broadband Mo:Si multilayer mirror, a fast decaying YAG:Ce scintillator, a visible light block, and a high-speed visible light CCD camera. The camera can capture EUV images as fast as 3.3 × 10{sup 6} frames per second with 0.5 cm spatial resolution. The spectral range is from 20 eV to 60 eV. EUV images reveal strong, transient, highly localized bursts of EUV radiation when magnetic reconnection occurs.

DNA methylation assessment from human slow- and fast-twitch skeletal muscle fibers

PubMed Central

Begue, Gwénaëlle; Raue, Ulrika; Jemiolo, Bozena

2017-01-01

A new application of the reduced representation bisulfite sequencing method was developed using low-DNA input to investigate the epigenetic profile of human slow- and fast-twitch skeletal muscle fibers. Successful library construction was completed with as little as 15 ng of DNA, and high-quality sequencing data were obtained with 32 ng of DNA. Analysis identified 143,160 differentially methylated CpG sites across 14,046 genes. In both fiber types, selected genes predominantly expressed in slow or fast fibers were hypomethylated, which was supported by the RNA-sequencing analysis. These are the first fiber type-specific methylation data from human skeletal muscle and provide a unique platform for future research. NEW & NOTEWORTHY This study validates a low-DNA input reduced representation bisulfite sequencing method for human muscle biopsy samples to investigate the methylation patterns at a fiber type-specific level. These are the first fiber type-specific methylation data reported from human skeletal muscle and thus provide initial insight into basal state differences in myosin heavy chain I and IIa muscle fibers among young, healthy men. PMID:28057818

Image quality assessment of silent T2 PROPELLER sequence for brain imaging in infants.

PubMed

Kim, Hyun Gi; Choi, Jin Wook; Yoon, Soo Han; Lee, Sieun

2018-02-01

Infants are vulnerable to high acoustic noise. Acoustic noise generated by MR scanning can be reduced by a silent sequence. The purpose of this study is to compare the image quality of the conventional and silent T2 PROPELLER sequences for brain imaging in infants. A total of 36 scans were acquired from 24 infants using a 3 T MR scanner. Each patient underwent both conventional and silent T2 PROPELLER sequences. Acoustic noise level was measured. Quantitative and qualitative assessments were performed with the images taken with each sequence. The sound pressure level of the conventional T2 PROPELLER imaging sequence was 92.1 dB and that of the silent T2 PROPELLER imaging sequence was 73.3 dB (reduction of 20%). On quantitative assessment, the two sequences (conventional vs silent T2 PROPELLER) did not show significant difference in relative contrast (0.069 vs 0.068, p value = 0.536) and signal-to-noise ratio (75.4 vs 114.8, p value = 0.098). Qualitative assessment of overall image quality (p value = 0.572), grey-white differentiation (p value = 0.986), shunt-related artefact (p value > 0.999), motion artefact (p value = 0.801) and myelination degree in different brain regions (p values ≥ 0.092) did not show significant difference between the two sequences. The silent T2 PROPELLER sequence reduces acoustic noise and generated comparable image quality to that of the conventional sequence. Advances in knowledge: This is the first report to compare silent T2 PROPELLER images with that of conventional T2 PROPELLER images in children.

Interleaved multishot imaging by spatiotemporal encoding: A fast, self-referenced method for high-definition diffusion and functional MRI.

PubMed

Schmidt, Rita; Seginer, Amir; Frydman, Lucio

2016-05-01

Single-shot imaging by spatiotemporal encoding (SPEN) can provide higher immunity to artifacts than its echo planar imaging-based counterparts. Further improvements in resolution and signal-to-noise ratio could be made by rescinding the sequence's single-scan nature. To explore this option, an interleaved SPEN version was developed that was capable of delivering optimized images due to its use of a referenceless correction algorithm. A characteristic element of SPEN encoding is the absence of aliasing when its signals are undersampled along the low-bandwidth dimension. This feature was exploited in this study to segment a SPEN experiment into a number of interleaved shots whose inaccuracies were automatically compared and corrected as part of a navigator-free image reconstruction analysis. This could account for normal phase noises, as well as for object motions during the signal collection. The ensuing interleaved SPEN method was applied to phantoms and human volunteers and delivered high-quality images even in inhomogeneous or mobile environments. Submillimeter functional MRI activation maps confined to gray matter regions as well as submillimeter diffusion coefficient maps of human brains were obtained. We have developed an interleaved SPEN approach for the acquisition of high-definition images that promises a wider range of functional and diffusion MRI applications even in challenging environments. © 2015 Wiley Periodicals, Inc.

Processing of Natural Echolocation Sequences in the Inferior Colliculus of Seba’s Fruit Eating Bat, Carollia perspicillata

PubMed Central

Kordes, Sebastian; Kössl, Manfred

2017-01-01

Abstract For the purpose of orientation, echolocating bats emit highly repetitive and spatially directed sonar calls. Echoes arising from call reflections are used to create an acoustic image of the environment. The inferior colliculus (IC) represents an important auditory stage for initial processing of echolocation signals. The present study addresses the following questions: (1) how does the temporal context of an echolocation sequence mimicking an approach flight of an animal affect neuronal processing of distance information to echo delays? (2) how does the IC process complex echolocation sequences containing echo information from multiple objects (multiobject sequence)? Here, we conducted neurophysiological recordings from the IC of ketamine-anaesthetized bats of the species Carollia perspicillata and compared the results from the IC with the ones from the auditory cortex (AC). Neuronal responses to an echolocation sequence was suppressed when compared to the responses to temporally isolated and randomized segments of the sequence. The neuronal suppression was weaker in the IC than in the AC. In contrast to the cortex, the time course of the acoustic events is reflected by IC activity. In the IC, suppression sharpens the neuronal tuning to specific call-echo elements and increases the signal-to-noise ratio in the units’ responses. When presenting multiple-object sequences, despite collicular suppression, the neurons responded to each object-specific echo. The latter allows parallel processing of multiple echolocation streams at the IC level. Altogether, our data suggests that temporally-precise neuronal responses in the IC could allow fast and parallel processing of multiple acoustic streams. PMID:29242823

Processing of Natural Echolocation Sequences in the Inferior Colliculus of Seba's Fruit Eating Bat, Carollia perspicillata.

PubMed

Beetz, M Jerome; Kordes, Sebastian; García-Rosales, Francisco; Kössl, Manfred; Hechavarría, Julio C

2017-01-01

For the purpose of orientation, echolocating bats emit highly repetitive and spatially directed sonar calls. Echoes arising from call reflections are used to create an acoustic image of the environment. The inferior colliculus (IC) represents an important auditory stage for initial processing of echolocation signals. The present study addresses the following questions: (1) how does the temporal context of an echolocation sequence mimicking an approach flight of an animal affect neuronal processing of distance information to echo delays? (2) how does the IC process complex echolocation sequences containing echo information from multiple objects (multiobject sequence)? Here, we conducted neurophysiological recordings from the IC of ketamine-anaesthetized bats of the species Carollia perspicillata and compared the results from the IC with the ones from the auditory cortex (AC). Neuronal responses to an echolocation sequence was suppressed when compared to the responses to temporally isolated and randomized segments of the sequence. The neuronal suppression was weaker in the IC than in the AC. In contrast to the cortex, the time course of the acoustic events is reflected by IC activity. In the IC, suppression sharpens the neuronal tuning to specific call-echo elements and increases the signal-to-noise ratio in the units' responses. When presenting multiple-object sequences, despite collicular suppression, the neurons responded to each object-specific echo. The latter allows parallel processing of multiple echolocation streams at the IC level. Altogether, our data suggests that temporally-precise neuronal responses in the IC could allow fast and parallel processing of multiple acoustic streams.

Fast iterative censoring CFAR algorithm for ship detection from SAR images

NASA Astrophysics Data System (ADS)

Gu, Dandan; Yue, Hui; Zhang, Yuan; Gao, Pengcheng

2017-11-01

Ship detection is one of the essential techniques for ship recognition from synthetic aperture radar (SAR) images. This paper presents a fast iterative detection procedure to eliminate the influence of target returns on the estimation of local sea clutter distributions for constant false alarm rate (CFAR) detectors. A fast block detector is first employed to extract potential target sub-images; and then, an iterative censoring CFAR algorithm is used to detect ship candidates from each target blocks adaptively and efficiently, where parallel detection is available, and statistical parameters of G0 distribution fitting local sea clutter well can be quickly estimated based on an integral image operator. Experimental results of TerraSAR-X images demonstrate the effectiveness of the proposed technique.

The different origins of magnetic fields and activity in the Hertzsprung gap stars, OU Andromedae and 31 Comae

NASA Astrophysics Data System (ADS)

Borisova, A.; Aurière, M.; Petit, P.; Konstantinova-Antova, R.; Charbonnel, C.; Drake, N. A.

2016-06-01

Context. When crossing the Hertzsprung gap, intermediate-mass stars develop a convective envelope. Fast rotators on the main sequence, or Ap star descendants, are expected to become magnetic active subgiants during this evolutionary phase. Aims: We compare the surface magnetic fields and activity indicators of two active, fast rotating red giants with similar masses and spectral class but different rotation rates - OU And (Prot = 24.2 d) and 31 Com (Prot = 6.8 d) - to address the question of the origin of their magnetism and high activity. Methods: Observations were carried out with the Narval spectropolarimeter in 2008 and 2013. We used the least-squares deconvolution (LSD) technique to extract Stokes V and I profiles with high signal-to-noise ratio to detect Zeeman signatures of the magnetic field of the stars. We then provide Zeeman-Doppler imaging (ZDI), activity indicators monitoring, and a precise estimation of stellar parameters. We use state-of-the-art stellar evolutionary models, including rotation, to infer the evolutionary status of our giants, as well as their initial rotation velocity on the main sequence, and we interpret our observational results in the light of the theoretical Rossby numbers. Results: The detected magnetic field of OU Andromedae (OU And) is a strong one. Its longitudinal component Bl reaches 40 G and presents an about sinusoidal variation with reversal of the polarity. The magnetic topology of OU And is dominated by large-scale elements and is mainly poloidal with an important dipole component, as well as a significant toroidal component. The detected magnetic field of 31 Comae (31 Com) is weaker, with a magnetic map showing a more complex field geometry, and poloidal and toroidal components of equal contributions. The evolutionary models show that the progenitors of OU And and 31 Com must have been rotating at velocities that correspond to 30 and 53%, respectively, of their critical rotation velocity on the zero age main sequence. Both OU And and 31 Com have very similar masses (2.7 and 2.85 M⊙, respectively), and they both lie in the Hertzsprung gap. Conclusions: OU And appears to be the probable descendant of a magnetic Ap star, and 31 Com the descendant of a relatively fast rotator on the main sequence. Because of the relatively fast rotation in the Hertzsprung gap and the onset of the development of a convective envelope, OU And also has a dynamo in operation. Based on observations obtained at the telescope Bernard Lyot (TBL) at Observatoire du Pic du Midi, CNRS/INSU and Université de Toulouse, France.

Multicore-based 3D-DWT video encoder

NASA Astrophysics Data System (ADS)

Galiano, Vicente; López-Granado, Otoniel; Malumbres, Manuel P.; Migallón, Hector

2013-12-01

Three-dimensional wavelet transform (3D-DWT) encoders are good candidates for applications like professional video editing, video surveillance, multi-spectral satellite imaging, etc. where a frame must be reconstructed as quickly as possible. In this paper, we present a new 3D-DWT video encoder based on a fast run-length coding engine. Furthermore, we present several multicore optimizations to speed-up the 3D-DWT computation. An exhaustive evaluation of the proposed encoder (3D-GOP-RL) has been performed, and we have compared the evaluation results with other video encoders in terms of rate/distortion (R/D), coding/decoding delay, and memory consumption. Results show that the proposed encoder obtains good R/D results for high-resolution video sequences with nearly in-place computation using only the memory needed to store a group of pictures. After applying the multicore optimization strategies over the 3D DWT, the proposed encoder is able to compress a full high-definition video sequence in real-time.

Real-Time Detection of Sporadic Meteors in the Intensified TV Imaging Systems.

PubMed

Vítek, Stanislav; Nasyrova, Maria

2017-12-29

The automatic observation of the night sky through wide-angle video systems with the aim of detecting meteor and fireballs is currently among routine astronomical observations. The observation is usually done in multi-station or network mode, so it is possible to estimate the direction and the speed of the body flight. The high velocity of the meteorite flying through the atmosphere determines the important features of the camera systems, namely the high frame rate. Thanks to high frame rates, such imaging systems produce a large amount of data, of which only a small fragment has scientific potential. This paper focuses on methods for the real-time detection of fast moving objects in the video sequences recorded by intensified TV systems with frame rates of about 60 frames per second. The goal of our effort is to remove all unnecessary data during the daytime and make free hard-drive capacity for the next observation. The processing of data from the MAIA (Meteor Automatic Imager and Analyzer) system is demonstrated in the paper.

Perfusion in Rat Brain at 7 T with Arterial Spin Labeling Using FAIR-TrueFISP and QUIPSS

PubMed Central

Esparza-Coss, Emilio; Wosik, Jarek; Narayana, Ponnada A.

2010-01-01

Measurement of perfusion in longitudinal studies allows for the assessment of tissue integrity and the detection of subtle pathologies. In this work, the feasibility of measuring brain perfusion in rats with high spatial resolution using arterial spin labeling (ASL) is reported. A flow sensitive alternating recovery (FAIR) sequence, coupled with a balanced gradient fast imaging with steady state precession (TrueFISP) readout section was used to minimize ghosting and geometric distortions, while achieving high SNR. The quantitative imaging of perfusion using a single subtraction (QUIPSS) method was implemented to address the effects of variable transit delays between the labeling of spins and their arrival at the imaging slice. Studies in six rats at 7 T showed good perfusion contrast with minimal geometric distortion. The measured blood flow values of 152.5 ± 6.3 ml/100g/min in gray matter and 72.3 ± 14.0 ml/100g/min in white matter are in good agreement with previously reported values based on autoradiography, considered to be the gold standard. PMID:20299174

Gapped pulses for frequency-swept MRI

NASA Astrophysics Data System (ADS)

Idiyatullin, Djaudat; Corum, Curt; Moeller, Steen; Garwood, Michael

2008-08-01

A recently introduced method called SWIFT (SWeep Imaging with Fourier Transform) is a fundamentally different approach to MRI which is particularly well suited to imaging objects with extremely fast spin-spin relaxation rates. The method exploits a frequency-swept excitation pulse and virtually simultaneous signal acquisition in a time-shared mode. Correlation of the spin system response with the excitation pulse function is used to extract the signals of interest. With SWIFT, image quality is highly dependent on producing uniform and broadband spin excitation. These requirements are satisfied by using frequency-modulated pulses belonging to the hyperbolic secant family (HS n pulses). This article describes the experimental steps needed to properly implement HS n pulses in SWIFT. In addition, properties of HS n pulses in the rapid passage, linear region are investigated, followed by an analysis of the pulses after inserting the "gaps" needed for time-shared excitation and acquisition. Finally, compact expressions are presented to estimate the amplitude and flip angle of the HS n pulses, as well as the relative energy deposited by the SWIFT sequence.

Real-Time Detection of Sporadic Meteors in the Intensified TV Imaging Systems

PubMed Central

2017-01-01

The automatic observation of the night sky through wide-angle video systems with the aim of detecting meteor and fireballs is currently among routine astronomical observations. The observation is usually done in multi-station or network mode, so it is possible to estimate the direction and the speed of the body flight. The high velocity of the meteorite flying through the atmosphere determines the important features of the camera systems, namely the high frame rate. Thanks to high frame rates, such imaging systems produce a large amount of data, of which only a small fragment has scientific potential. This paper focuses on methods for the real-time detection of fast moving objects in the video sequences recorded by intensified TV systems with frame rates of about 60 frames per second. The goal of our effort is to remove all unnecessary data during the daytime and make free hard-drive capacity for the next observation. The processing of data from the MAIA (Meteor Automatic Imager and Analyzer) system is demonstrated in the paper. PMID:29286294

MPCM: a hardware coder for super slow motion video sequences

NASA Astrophysics Data System (ADS)

Alcocer, Estefanía; López-Granado, Otoniel; Gutierrez, Roberto; Malumbres, Manuel P.

2013-12-01

In the last decade, the improvements in VLSI levels and image sensor technologies have led to a frenetic rush to provide image sensors with higher resolutions and faster frame rates. As a result, video devices were designed to capture real-time video at high-resolution formats with frame rates reaching 1,000 fps and beyond. These ultrahigh-speed video cameras are widely used in scientific and industrial applications, such as car crash tests, combustion research, materials research and testing, fluid dynamics, and flow visualization that demand real-time video capturing at extremely high frame rates with high-definition formats. Therefore, data storage capability, communication bandwidth, processing time, and power consumption are critical parameters that should be carefully considered in their design. In this paper, we propose a fast FPGA implementation of a simple codec called modulo-pulse code modulation (MPCM) which is able to reduce the bandwidth requirements up to 1.7 times at the same image quality when compared with PCM coding. This allows current high-speed cameras to capture in a continuous manner through a 40-Gbit Ethernet point-to-point access.

Image registration and analysis for quantitative myocardial perfusion: application to dynamic circular cardiac CT.

PubMed

Isola, A A; Schmitt, H; van Stevendaal, U; Begemann, P G; Coulon, P; Boussel, L; Grass, M

2011-09-21

Large area detector computed tomography systems with fast rotating gantries enable volumetric dynamic cardiac perfusion studies. Prospectively, ECG-triggered acquisitions limit the data acquisition to a predefined cardiac phase and thereby reduce x-ray dose and limit motion artefacts. Even in the case of highly accurate prospective triggering and stable heart rate, spatial misalignment of the cardiac volumes acquired and reconstructed per cardiac cycle may occur due to small motion pattern variations from cycle to cycle. These misalignments reduce the accuracy of the quantitative analysis of myocardial perfusion parameters on a per voxel basis. An image-based solution to this problem is elastic 3D image registration of dynamic volume sequences with variable contrast, as it is introduced in this contribution. After circular cone-beam CT reconstruction of cardiac volumes covering large areas of the myocardial tissue, the complete series is aligned with respect to a chosen reference volume. The results of the registration process and the perfusion analysis with and without registration are evaluated quantitatively in this paper. The spatial alignment leads to improved quantification of myocardial perfusion for three different pig data sets.

Preservation of tumour oxygen after hyperbaric oxygenation monitored by magnetic resonance imaging

PubMed Central

Kinoshita, Y; Kohshi, K; Kunugita, N; Tosaki, T; Yokota, A

1999-01-01

Hyperbaric oxygen (HBO) has been proposed to reduce tumour hypoxia by increasing the dissolved molecular oxygen in tissue. Using a non-invasive magnetic resonance imaging (MRI) technique, we monitored the changes in MRI signal intensity after HBO exposure because dissolved paramagnetic molecular oxygen itself shortens the T1 relation time. SCCVII tumour cells transplanted in mice were used. The molecular oxygen-enhanced MR images were acquired using an inversion recovery-preparation fast low angle shot (IR-FLASH) sequence sensitizing the paramagnetic effects of molecular oxygen using a 4.7 tesla MR system. MR signal of muscles decreased rapidly and returned to the control level within 40 min after decompression, whereas that of tumours decreased gradually and remained at a high level 60 min after HBO exposure. In contrast, the signal from the tumours in the normobaric oxygen group showed no significant change. Our data suggested that MR signal changes of tumours and muscles represent an alternation of extravascular oxygenation. The preserving tumour oxygen concentration after HBO exposure may be important regarding adjuvant therapy for cancer patients. © 2000 Cancer Research Campaign PMID:10638972

Development of a morphology-based modeling technique for tracking solid-body displacements: examining the reliability of a potential MRI-only approach for joint kinematics assessment.

PubMed

Mahato, Niladri K; Montuelle, Stephane; Cotton, John; Williams, Susan; Thomas, James; Clark, Brian

2016-05-18

Single or biplanar video radiography and Roentgen stereophotogrammetry (RSA) techniques used for the assessment of in-vivo joint kinematics involves application of ionizing radiation, which is a limitation for clinical research involving human subjects. To overcome this limitation, our long-term goal is to develop a magnetic resonance imaging (MRI)-only, three dimensional (3-D) modeling technique that permits dynamic imaging of joint motion in humans. Here, we present our initial findings, as well as reliability data, for an MRI-only protocol and modeling technique. We developed a morphology-based motion-analysis technique that uses MRI of custom-built solid-body objects to animate and quantify experimental displacements between them. The technique involved four major steps. First, the imaging volume was calibrated using a custom-built grid. Second, 3-D models were segmented from axial scans of two custom-built solid-body cubes. Third, these cubes were positioned at pre-determined relative displacements (translation and rotation) in the magnetic resonance coil and scanned with a T1 and a fast contrast-enhanced pulse sequences. The digital imaging and communications in medicine (DICOM) images were then processed for animation. The fourth step involved importing these processed images into an animation software, where they were displayed as background scenes. In the same step, 3-D models of the cubes were imported into the animation software, where the user manipulated the models to match their outlines in the scene (rotoscoping) and registered the models into an anatomical joint system. Measurements of displacements obtained from two different rotoscoping sessions were tested for reliability using coefficient of variations (CV), intraclass correlation coefficients (ICC), Bland-Altman plots, and Limits of Agreement analyses. Between-session reliability was high for both the T1 and the contrast-enhanced sequences. Specifically, the average CVs for translation were 4.31 % and 5.26 % for the two pulse sequences, respectively, while the ICCs were 0.99 for both. For rotation measures, the CVs were 3.19 % and 2.44 % for the two pulse sequences with the ICCs being 0.98 and 0.97, respectively. A novel biplanar imaging approach also yielded high reliability with mean CVs of 2.66 % and 3.39 % for translation in the x- and z-planes, respectively, and ICCs of 0.97 in both planes. This work provides basic proof-of-concept for a reliable marker-less non-ionizing-radiation-based quasi-dynamic motion quantification technique that can potentially be developed into a tool for real-time joint kinematics analysis.

MICRA: an automatic pipeline for fast characterization of microbial genomes from high-throughput sequencing data.

PubMed

Caboche, Ségolène; Even, Gaël; Loywick, Alexandre; Audebert, Christophe; Hot, David

2017-12-19

The increase in available sequence data has advanced the field of microbiology; however, making sense of these data without bioinformatics skills is still problematic. We describe MICRA, an automatic pipeline, available as a web interface, for microbial identification and characterization through reads analysis. MICRA uses iterative mapping against reference genomes to identify genes and variations. Additional modules allow prediction of antibiotic susceptibility and resistance and comparing the results of several samples. MICRA is fast, producing few false-positive annotations and variant calls compared to current methods, making it a tool of great interest for fully exploiting sequencing data.

Error reduction and parameter optimization of the TAPIR method for fast T1 mapping.

PubMed

Zaitsev, M; Steinhoff, S; Shah, N J

2003-06-01

A methodology is presented for the reduction of both systematic and random errors in T(1) determination using TAPIR, a Look-Locker-based fast T(1) mapping technique. The relations between various sequence parameters were carefully investigated in order to develop recipes for choosing optimal sequence parameters. Theoretical predictions for the optimal flip angle were verified experimentally. Inversion pulse imperfections were identified as the main source of systematic errors in T(1) determination with TAPIR. An effective remedy is demonstrated which includes extension of the measurement protocol to include a special sequence for mapping the inversion efficiency itself. Copyright 2003 Wiley-Liss, Inc.

ACMES: fast multiple-genome searches for short repeat sequences with concurrent cross-species information retrieval

PubMed Central

Reneker, Jeff; Shyu, Chi-Ren; Zeng, Peiyu; Polacco, Joseph C.; Gassmann, Walter

2004-01-01

We have developed a web server for the life sciences community to use to search for short repeats of DNA sequence of length between 3 and 10 000 bases within multiple species. This search employs a unique and fast hash function approach. Our system also applies information retrieval algorithms to discover knowledge of cross-species conservation of repeat sequences. Furthermore, we have incorporated a part of the Gene Ontology database into our information retrieval algorithms to broaden the coverage of the search. Our web server and tutorial can be found at http://acmes.rnet.missouri.edu. PMID:15215469

A Segmentation Method for Lung Parenchyma Image Sequences Based on Superpixels and a Self-Generating Neural Forest

PubMed Central

Liao, Xiaolei; Zhao, Juanjuan; Jiao, Cheng; Lei, Lei; Qiang, Yan; Cui, Qiang

2016-01-01

Background Lung parenchyma segmentation is often performed as an important pre-processing step in the computer-aided diagnosis of lung nodules based on CT image sequences. However, existing lung parenchyma image segmentation methods cannot fully segment all lung parenchyma images and have a slow processing speed, particularly for images in the top and bottom of the lung and the images that contain lung nodules. Method Our proposed method first uses the position of the lung parenchyma image features to obtain lung parenchyma ROI image sequences. A gradient and sequential linear iterative clustering algorithm (GSLIC) for sequence image segmentation is then proposed to segment the ROI image sequences and obtain superpixel samples. The SGNF, which is optimized by a genetic algorithm (GA), is then utilized for superpixel clustering. Finally, the grey and geometric features of the superpixel samples are used to identify and segment all of the lung parenchyma image sequences. Results Our proposed method achieves higher segmentation precision and greater accuracy in less time. It has an average processing time of 42.21 seconds for each dataset and an average volume pixel overlap ratio of 92.22 ± 4.02% for four types of lung parenchyma image sequences. PMID:27532214