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1

Simulation Study on Active Noise Control for a 4 Tesla MRI Scanner  

PubMed Central

The purpose of this work is to study computationally the possibility of the application of a hybrid active noise control technique for MRI acoustic noise reduction. A hybrid control system combined with both feedforward and feedback loops embedded is proposed for potential application on active MRI noise reduction. A set of computational simulation studies were performed. Sets of MRI acoustic noise emissions measured at the patient's left ear location were recorded and used in the simulation study. By comparing three different control systems, namely the feedback, the feedforward and the hybrid control, our results revealed that the hybrid control system is the most effective. The hybrid control system achieved approximately a 20 dB reduction at the principal frequency component. We concluded that the proposed hybrid active control scheme could have a potential application for MRI scanner noise reduction.

Li, Mingfeng; Lim, Teik C.; Lee, Jing-Huei

2008-01-01

2

Occupational exposure of healthcare and research staff to static magnetic stray fields from 1.5-7 Tesla MRI scanners is associated with reporting of transient symptoms  

PubMed Central

Objectives Limited data is available about incidence of acute transient symptoms associated with occupational exposure to static magnetic stray fields from MRI scanners. We aimed to assess the incidence of these symptoms among healthcare and research staff working with MRI scanners, and their association with static magnetic field exposure. Methods We performed an observational study among 361 employees of 14 clinical and research MRI facilities in The Netherlands. Each participant completed a diary during one or more work shifts inside and/or outside the MRI facility, reporting work activities and symptoms (from a list of potentially MRI-related symptoms, complemented with unrelated symptoms) experienced during a working day. We analysed 633 diaries. Exposure categories were defined by strength and type of MRI scanner, using non-MRI shifts as the reference category for statistical analysis. Non-MRI shifts originated from MRI staff who also participated on MRI days, as well as CT radiographers who never worked with MRI. Results Varying per exposure category, symptoms were reported during 16–39% of the MRI work shifts. We observed a positive association between scanner strength and reported symptoms among healthcare and research staff working with closed-bore MRI scanners of 1.5 Tesla (T) and higher (1.5?T OR=1.88; 3.0?T OR=2.14; 7.0?T OR=4.17). This finding was mainly driven by reporting of vertigo and metallic taste. Conclusions The results suggest an exposure-response association between exposure to strong static magnetic fields (and associated motion-induced time-varying magnetic fields) and reporting of transient symptoms on the same day of exposure. Trial registration number 11-032/C

Schaap, Kristel; Christopher-de Vries, Yvette; Mason, Catherine K; de Vocht, Frank; Portengen, Lutzen; Kromhout, Hans

2014-01-01

3

MRI scanner transport system.  

PubMed

A computer-controlled transport system has been designed and tested for small bore magnetic resonance scanners for animal research. The transport system allows remote animal positioning based on scout images using a graphic interface. The design utilized commercially available components suitable for use in the scanner's strong magnetic field. Tests indicate positioning accuracy of the transport system to be within 0.13 mm. PMID:8084229

Phillips, J R; Falconer, J C; Botzer, S; Narayana, P A

1994-07-01

4

An RF dosimeter for independent SAR measurement in MRI scanners  

SciTech Connect

Purpose: The monitoring and management of radio frequency (RF) exposure is critical for ensuring magnetic resonance imaging (MRI) safety. Commercial MRI scanners can overestimate specific absorption rates (SAR) and improperly restrict clinical MRI scans or the application of new MRI sequences, while underestimation of SAR can lead to tissue heating and thermal injury. Accurate scanner-independent RF dosimetry is essential for measuring actual exposure when SAR is critical for ensuring regulatory compliance and MRI safety, for establishing RF exposure while evaluating interventional leads and devices, and for routine MRI quality assessment by medical physicists. However, at present there are no scanner-independent SAR dosimeters. Methods: An SAR dosimeter with an RF transducer comprises two orthogonal, rectangular copper loops and a spherical MRI phantom. The transducer is placed in the magnet bore and calibrated to approximate the resistive loading of the scanner's whole-body birdcage RF coil for human subjects in Philips, GE and Siemens 3 tesla (3T) MRI scanners. The transducer loop reactances are adjusted to minimize interference with the transmit RF field (B{sub 1}) at the MRI frequency. Power from the RF transducer is sampled with a high dynamic range power monitor and recorded on a computer. The deposited power is calibrated and tested on eight different MRI scanners. Whole-body absorbed power vs weight and body mass index (BMI) is measured directly on 26 subjects. Results: A single linear calibration curve sufficed for RF dosimetry at 127.8 MHz on three different Philips and three GE 3T MRI scanners. An RF dosimeter operating at 123.2 MHz on two Siemens 3T scanners required a separate transducer and a slightly different calibration curve. Measurement accuracy was ?3%. With the torso landmarked at the xiphoid, human adult whole?body absorbed power varied approximately linearly with patient weight and BMI. This indicates that whole-body torso SAR is on average independent of the imaging subject, albeit with fluctuations. Conclusions: Our 3T RF dosimeter and transducers accurately measure RF exposure in body-equivalent loads and provide scanner-independent assessments of whole-body RF power deposition for establishing safety compliance useful for MRI sequence and device testing.

Qian, Di; Bottomley, Paul A. [Division of MR Research, Department of Radiology, Johns Hopkins School of Medicine, Baltimore, Maryland 21287 and Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States)] [Division of MR Research, Department of Radiology, Johns Hopkins School of Medicine, Baltimore, Maryland 21287 and Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); El-Sharkawy, AbdEl-Monem M.; Edelstein, William A., E-mail: w.edelstein@gmail.com [Division of MR Research, Department of Radiology, Johns Hopkins School of Medicine, Baltimore, Maryland 21287 (United States)

2013-12-15

5

Combined PET/MRI scanner  

DOEpatents

A combined PET/MRI scanner generally includes a magnet for producing a magnetic field suitable for magnetic resonance imaging, a radiofrequency (RF) coil disposed within the magnetic field produced by the magnet and a ring tomograph disposed within the magnetic field produced by the magnet. The ring tomograph includes a scintillator layer for outputting at least one photon in response to an annihilation event, a detection array coupled to the scintillator layer for detecting the at least one photon outputted by the scintillator layer and for outputting a detection signal in response to the detected photon and a front-end electronic array coupled to the detection array for receiving the detection signal, wherein the front-end array has a preamplifier and a shaper network for conditioning the detection signal.

Schlyer, David (Bellport, NY); Woody, Craig L. (Setauket, NY); Rooney, William (Miller Place, NY); Vaska, Paul (Sound Beach, NY); Stoll, Sean (Wading River, NY); Pratte, Jean-Francois (Stony Brook, NY); O'Connor, Paul (Bellport, NY)

2007-10-23

6

Muscle-fat MRI: 1.5 tesla and 3.0 tesla versus histology.  

PubMed

Introduction: We evaluated muscle/fat fraction (MFF) accuracy and reliability measured with an MR imaging technique at 1.5 Tesla (T) and 3.0T scanner strengths, using biopsy as reference. Methods: MRI was performed on muscle samples from pig and rabbit species (n?=?8) at 1.5T and 3.0T. A chemical shift based 2-point Dixon method was used, collecting in-phase and out-of-phase data for fat/water of muscle samples. Values were compared with MFFs calculated from histology. Results: No significant difference was found between 1.5T and 3.0T (P values?=?0.41-0.96), or between histology and imaging (P?=?0.83) for any muscle tested. Conclusions: Results suggest that a 2-point Dixon fat/water separation MRI technique may provide reliable quantification of MFFs at varying field strengths across different animal species, and consistency was established with biopsy. The results set a foundation for larger scale investigation of quantifying muscle fat in neuromuscular disorders. Muscle Nerve 50:170-176, 2014. PMID:24677256

Smith, Andrew C; Parrish, Todd B; Abbott, Rebecca; Hoggarth, Mark A; Mendoza, Karl; Chen, Yu Fen; Elliott, James M

2014-08-01

7

[3 Tesla MRI: successful results with higher field strengths].  

PubMed

The recent development of 3 Tesla MRI (3T MRI) has been fueled by promise of increased signal-to-noise ratio(SNR). Many are excited about the opportunity to not only use the increased SNR for clearer images, but also the chance to exchange it for better resolution or faster scans. These possibilities have caused a rapid increase in the market for 3T MRI, where the faster scanning tips an already advantageous economic outlook in favor of the user. As a result, the global market for 3T has grown from a research only market just a few years ago to an ever-increasing clinically oriented customer base. There are, however, significant obstacles to 3T MRI presented by the physics at higher field strengths. For example, the T1 relaxation times are prolonged with increasing magnet field strength. Further, the increased RF-energy deposition (SAR), the larger the chemical shift and the stronger susceptibility effect have to be considered as challenges. It is critical that one looks at both the advantages and disadvantages of using 3T. While there are many issues to address aand a number of different methods for doing so, to properly tackle each of these concerns will take time and effort on the part od researchers and clinicians. The optimization of 3T MRI scanning will have to be a combined effort, though much of the work to date has been in neuroimaging. Multiple applications have been explored in addition to clinical anatomical imaging, where resolution is improved showing structure in the brain never seen before in human MRI. Body and cardiac imaging provide a great challenge but are also achievable at 3T. As an example, the full range of clinical applications currently achieved on today's state-of-the-art 1.5T cardiac MR scanners has also been demonstrated at 3T. In the body, the full range of contrast is available over large fields of view allowing whole liver studies in the clinic or, as needed, one may choose a smaller field of view for high-resolution imaging of the pancreas. The ability to increase resolution for musculoskeletal imaging has provided previously unseen detail. Bone structure, cartilage, and tendons and ligaments can be clearly visualized and pathology more easily detected due to an increased image quality. As the increase in field strength continues, a push to look at 7T has begun. The design philosophy is to keep the system as similar as possible, while changing only the frequency-dependent components. To date, both animal and human imaging have been performed on a whole body 7T scanner. Results show promise for both detailed imaging and functional MRI, but the road ahead is too long to be able to predict where it will end. The move toward higher field strengths is an exciting adventure in which 3T plays the role of trailblazer. PMID:14997868

Schmitt, F; Grosu, D; Mohr, C; Purdy, D; Salem, K; Scott, K T; Stoeckel, B

2004-01-01

8

4 Tesla MRI for Neurodegenerative Diseases.  

National Technical Information Service (NTIS)

During the past year, nine research projects have used the 4Tesla magnet (for a total of 398 scans), and 55 developmental scans had been completed. Since the last progress report, we upgraded the shim currents which substantially improved the quality of i...

M. W. Weiner

2005-01-01

9

3 Tesla intraoperative MRI for brain tumor surgery.  

PubMed

Implementation of intraoperative magnetic resonance imaging (iMRI) has been shown to optimize the extent of resection and safety of brain tumor surgery. In addition, iMRI can help account for the phenomenon of brain shift and can help to detect complications earlier than routine postoperative imaging, which can potentially improve patient outcome. The higher signal-to-noise ratio offered by 3 Tesla (T) iMRI compared with lower field strength systems is particularly advantageous. The purpose of this article is to review the imaging protocols, imaging findings, and technical considerations related to 3T iMRI. To maximize efficiency, iMRI sequences can be tailored to particular types of tumors and procedures, including nonenhancing brain tumor surgery, enhancing brain tumor surgery, transsphenoidal pituitary tumor surgery, and laser ablation. Unique imaging findings on iMRI include the presence of surgically induced enhancement, which can be a potential confounder for residual enhancing tumor, and hyperacute hemorrhage, which tends to have intermediate signal on T1-weighted sequences and high signal on T2-weighted sequences due to the presence of oxyhemoglobin. MR compatibility and radiofrequency shielding pose particularly stringent technical constraints at 3T and influence the design and usage of the surgical suite with iMRI. PMID:24921066

Ginat, Daniel Thomas; Swearingen, Brooke; Curry, William; Cahill, Daniel; Madsen, Joseph; Schaefer, Pamela W

2014-06-01

10

Early Knee Changes in Dancers Identified by Ultra High Field 7 Tesla MRI  

PubMed Central

Introduction We aimed to determine whether a unique, ultra high-field 7 Tesla (T) MRI scanner could detect occult cartilage and meniscal injuries in asymptomatic female dancers. Materials and Methods This study had institutional review board approval. We recruited eight pre-professional female dancers and nine non-athletic, female controls. We scanned the dominant knee on a 7T MRI scanner using a 3D-FLASH sequence and a proton density, fast spin-echo sequence to evaluate cartilage and menisci, respectively. Two radiologists scored cartilage (International Cartilage Repair Society classification) and meniscal (Stoller classification) lesions. We applied two-tailed z- and t-tests to determine statistical significance. Results There were no cartilage lesions in dancers or controls. For the medial meniscus, the dancers compared to controls demonstrated higher mean MRI score (2.38±0.61 vs. 1.0±0.97, p<0.0001) and higher frequency of mean grade 2 lesions (88% vs. 11%, p<0.01). For the lateral meniscus, there was no difference in score (0.5±0.81 vs. 0.5±0.78, p=0.78) in dancers compared to controls. Discussion Asymptomatic dancers demonstrate occult medial meniscal lesions. Because this has been described in early osteoarthritis, close surveillance of dancers’ knee symptoms and function with appropriate activity modification may help maintain their long-term knee health.

Chang, Gregory; Diamond, Matthew; Nevsky, Gregory; Regatte, Ravinder R.; Weiss, David S.

2012-01-01

11

Imaging Findings of Brain Death on 3-Tesla MRI  

PubMed Central

Objective To demonstrate the usefulness of 3-tesla (3T) magnetic resonance imaging (MRI) including T2-weighted imaging (T2WI), diffusion weighted imaging (DWI), time-of-flight (TOF) magnetic resonance angiography (MRA), T2*-weighted gradient recalled echo (GRE), and susceptibility weighted imaging (SWI) in diagnosing brain death. Materials and Methods Magnetic resonance imaging findings for 10 patients with clinically verified brain death (group I) and seven patients with comatose or stuporous mentality who did not meet the clinical criteria of brain death (group II) were retrospectively reviewed. Results Tonsilar herniation and loss of intraarterial flow signal voids (LIFSV) on T2WI were highly sensitive and specific findings for the diagnosis of brain death (p < 0.001 and < 0.001, respectively). DWI, TOF-MRA, and GRE findings were statistically different between the two groups (p = 0.015, 0.029, and 0.003, respectively). However, cortical high signal intensities in T2WI and SWI findings were not statistically different between the two group (p = 0.412 and 1.0, respectively). Conclusion T2-weighted imaging, DWI, and MRA using 3T MRI may be useful for diagnosing brain death. However, SWI findings are not specific due to high false positive findings.

Sohn, Chul-Ho; Lee, Hwa-Pyung; Park, Jun Beom; Kim, Ealmaan; Kim, Eunhee; Park, Ui Jun; Kim, Hyoung-Tae; Ku, Jeonghun

2012-01-01

12

A fiber-optic system for recording skin conductance in the MRI scanner.  

PubMed

The acquisition of the skin conductance response (SCR) during functional magnetic resonance imaging (fMRI) raises significant safety issues, as well as practical ones, which need to be addressed in order for these experiments to be conducted safely and successfully. Metallic and conductive wires in the presence of time-varying gradient magnetic fields such as those present in fMRI experiments may induce heating, as well as electric fields, in these components and, if in contact with the subject, could produce severe burns and electric shocks. Moreover, these metallic and conductive components can significantly distort the magnetic field, resulting in image artifacts. A system for recording the SCR in humans simultaneously with fMRI is presented. The device is a fiber-optic-based transducer, which records the SCR from two fingers of the same hand, using electrodes containing inline radio frequency (RF) suppression filters and protective resistive loads. The fiber-optic SCR transducer was tested using 1.5 and 3.0 Tesla MRI scanners running EPI sequences. This system was able to safely record SCRs free of RF interference during an fMRI experiment, and the fiber-optic design of the transducer eliminated any artifacts on the MRI scan. PMID:16629299

Lagopoulos, Jim; Malhi, Gin S; Shnier, Ronald C

2005-11-01

13

Speech Perception in MRI Scanner Noise by Persons with Aphasia  

ERIC Educational Resources Information Center

Purpose: To examine reductions in performance on auditory tasks by aphasic and neurologically intact individuals as a result of concomitant magnetic resonance imaging (MRI) scanner noise. Method: Four tasks together forming a continuum of linguistic complexity were developed. They included complex-tone pitch discrimination, same-different…

Healy, Eric W.; Moser, Dana C.; Morrow-Odom, K. Leigh; Hall, Deborah A.; Fridriksson, Julius

2007-01-01

14

Hippocampal T2 hyperintensities on 7 Tesla MRI?  

PubMed Central

Hippocampal focal T2 hyperintensities (HT2Hs), also referred to as hippocampal sulcal cavities, are a common finding on Magnetic Resonance (MR) images. There is uncertainty about their etiology and clinical significance. In this study we aimed to describe these HT2Hs in more detail using high resolution 7 Tesla MR imaging, addressing 1) the MR signal characteristics of HT2Hs, 2) their occurrence frequency, 3) their location within the hippocampus, and 4) their relation with age. We also performed an explorative post-mortem study to examine the histology of HT2Hs. Fifty-eight persons without a history of invalidating neurological or psychiatric disease (mean age 64 ± 8 years; range 43–78 years), recruited through their general practitioners, were included in this study. They all underwent 7 Tesla MRI, including a T1, T2, and FLAIR image. MR signal characteristics of the HT2Hs were assessed on these images by two raters. Also, the location and number of the HT2Hs were assessed. In addition, four formalin-fixed brain slices from two subjects were scanned overnight. HT2Hs identified in these slices were subjected to histopathological analysis. HT2Hs were present in 97% of the subjects (median number per person 10; range 0–20). All HT2Hs detected on the T2 sequence were hypointense on T1 weighted images. Of all HT2Hs, 94% was hypointense and 6% hyperintense on FLAIR. FLAIR hypointense HT2Hs were all located in the vestigial sulcus of the hippocampus, FLAIR hyperintense HT2Hs in the hippocampal sulcus or the gray matter. Post-mortem MRI and histopathological analysis suggested that the hypointense HT2Hs on FLAIR were cavities filled with cerebrospinal fluid. A hyperintense HT2H on FLAIR proved to be a microinfarct upon microscopy. In conclusion, hippocampal T2Hs are extremely common and unrelated to age. They can be divided into two types (hypo- and hyperintense on FLAIR), probably with different etiology.

van Veluw, Susanne J.; Wisse, Laura E.M.; Kuijf, Hugo J.; Spliet, Wim G.M.; Hendrikse, Jeroen; Luijten, Peter R.; Geerlings, Mirjam I.; Biessels, Geert Jan

2013-01-01

15

Implementation of wavelet encoding spectroscopic imaging technique on a 3 Tesla whole body MR scanner: in vitro results.  

PubMed

Proton magnetic resonance spectroscopic imaging (MRSI) provides spatial information about tissue metabolite concentrations used in differentiating diseased from normal tissue. Obtaining metabolic maps with high spatial resolution requires long acquisition time where the patient has to lie still inside the magnet bore (scanner) especially if classical Chemical Shift Imaging (CSI) is used. To reduce acquisition time and obtain a more accurate metabolite distribution with low voxel contamination in MRSI, we have recently proposed and successfully implemented a full Wavelet Encoding-Spectroscopic Imaging (WE-SI) technique on a 1.5 Tesla whole body MR clinical scanner. In this paper we describe the implementation of the WE-SI technique at higher magnetic field strength (B(0)) on a clinical 3 Tesla Siemens scanner equipped with parallel imaging tools for better sensitivity. This increases the signal to noise ratio (SNR) and allows combination of the proposed technique with the so-called parallel imaging approach for further acquisition time reduction. PMID:19963541

Fu, Y; Ijare, O; Thomas, G; Fazel-Rezai, R; Serrai, H

2009-01-01

16

Measurement and evaluation of the acoustic noise of a 3 Tesla MR scanner.  

PubMed

We measured the sound level and frequencies of the acoustic noise generated by a 3 Tesla (T) MR scanner, and investigated the subjective sound level for 30 healthy volunteers with either earplugs, headphones or both. The sound level of 3T was found to be higher than that of 1.5T in all sequences. The peak sound pressure level of 3T ranged from 125.7 dB for MR angiography to 130.7 dB for single shot EPI on the linear scale. The equivalent noise level was from 110.0 dB for FLAIR to 115.8 dB for T1-IR on the A-weighted scale, which exceeded 99 dB, the level regulated by the International Electrotechnical Commission (IEC). The study of the subjective sound level showed that the effect of noise reduction was not significantly different between earplugs and headphones. However, the use of both devices could reduce the subjective sound level significantly better than either one alone (P < 0.01). Thus we propose wearing both devices for ear-protection during 3T examinations. PMID:17378177

Hattori, Yoko; Fukatsu, Hiroshi; Ishigaki, Takeo

2007-01-01

17

Absolute Temperature Monitoring Using RF Radiometry in the MRI Scanner  

PubMed Central

Temperature detection using microwave radiometry has proven value for noninvasively measuring the absolute temperature of tissues inside the body. However, current clinical radiometers operate in the gigahertz range, which limits their depth of penetration. We have designed and built a noninvasive radiometer which operates at radio frequencies (64 MHz) with ?100-kHz bandwidth, using an external RF loop coil as a thermal detector. The core of the radiometer is an accurate impedance measurement and automatic matching circuit of 0.05 ? accuracy to compensate for any load variations. The radiometer permits temperature measurements with accuracy of ±0.1°K, over a tested physiological range of 28° C–40° C in saline phantoms whose electric properties match those of tissue. Because 1.5 T magnetic resonance imaging (MRI) scanners also operate at 64 MHz, we demonstrate the feasibility of integrating our radiometer with an MRI scanner to monitor RF power deposition and temperature dosimetry, obtaining coarse, spatially resolved, absolute thermal maps in the physiological range. We conclude that RF radiometry offers promise as a direct, noninvasive method of monitoring tissue heating during MRI studies and thereby providing an independent means of verifying patient-safe operation. Other potential applications include titration of hyper- and hypo-therapies.

El-Sharkawy, AbdEl-Monem M.; Sotiriadis, Paul P.; Bottomley, Paul A.; Atalar, Ergin

2007-01-01

18

Evaluation of pressure-driven brain infusions in non-human primates by intra-operative 7 Tesla MRI  

PubMed Central

PURPOSE The goal of this study was to characterize the effects of pressure-driven brain infusions using high field intra-operative MRI. Understanding these effects is critical for upcoming neurodegeneration and oncology trials using convection-enhanced delivery (CED) to achieve large drug distributions with minimal off-target exposure. MATERIALS AND METHODS High-resolution T2-weighted and diffusion-tensor images were acquired serially on a 7 Tesla MRI scanner during six CED infusions in non-human primates. The images were used to evaluate the size, distribution, diffusivity and temporal dynamics of the infusions. RESULTS The infusion distribution had high contrast in the T2-weighted images. Diffusion tensor images showed the infusion increased diffusivity, reduced tortuosity and reduced anisotropy. These results suggested CED caused an increase in the extracellular space. CONCLUSIONS High-field intra-operative MRI can be used to monitor the distribution of infusate and changes in the geometry of the brain’s porous matrix. These techniques could be used to optimize the effectiveness of pressure-driven drug delivery to the brain.

Rosenbluth, Kathryn H.; Martin, Alastair J.; Bringas, John; Bankiewicz, Krystof S.

2012-01-01

19

Reliability of Stereotactic Coordinates of 1.5-Tesla and 3-Tesla MRI in Radiosurgery and Functional Neurosurgery  

PubMed Central

Objective The aims of this study are to identify interpersonal differences in defining coordinates and to figure out the degree of distortion of the MRI and compare the accuracy between CT, 1.5-tesla (T) and 3.0T MRI. Methods We compared coordinates in the CT images defined by 2 neurosurgeons. We also calculated the errors of 1.5T MRI and those of 3.0T. We compared the errors of the 1.5T with those of the 3.0T. In addition, we compared the errors in each sequence and in each axis. Results The mean difference in the CT images between the two neurosurgeons was 0.48±0.22 mm. The mean errors of the 1.5T were 1.55±0.48 mm (T1), 0.75±0.38 (T2), and 1.07±0.57 (FLAIR) and those of the 3.0T were 2.35±0.53 (T1), 2.18±0.76 (T2), and 2.16±0.77 (FLAIR). The smallest mean errors out of all the axes were in the x axis : 0.28-0.34 (1.5T) and 0.31-0.52 (3.0T). The smallest errors out of all the MRI sequences were in the T2 : 0.29-0.58 (1.5T) and 0.31-1.85 (3.0T). Conclusion There was no interpersonal difference in running the Gamma Plan® to define coordinates. The errors of the 3.0T were greater than those of the 1.5T, and these errors were not of an acceptable level. The x coordinate error was the smallest and the z coordinate error was the greatest regardless of the MRI sequence. The T2 sequence was the most accurate sequence.

Lee, Sun-il; Jin, Seong Jin; Jin, Sung-Chul; Kim, Jung Soo; Jeon, Kyoung Dong

2014-01-01

20

Focused tight dressing does not prevent cochlear implant magnet migration under 1.5 Tesla MRI.  

PubMed

We report a retrospective case of inner magnet migration, which occurred after 1.5 Tesla MRI scanning in an adult recipient of a bilateral cochlear implant (CI) despite a focused head dressing. The patient, bilaterally implanted with Nucleus 5 CIs (Cochlear LTD, Sydney, Australia), underwent a 1.5 Tesla cholangio-MRI scan for biliary duct pathology. In subsequent days, a focal skin alteration appeared over the left inner coil. Plain skull radiographs showed partial magnet migration on the left side. Surgical exploration confirmed magnet twisting; the magnet was effectively repositioned. Left CI performance was restored to pre-migration level. The wound healed without complications. Thus, focused dressing does not prevent magnet migration in CI recipients undergoing 1.5 Tesla MRI. All patients should be counselled on this potential complication. A minor surgical procedure is required to reposition the magnet. Nevertheless, timely diagnosis is necessary to prevent skin breakdown and subsequent device contamination. Plain skull radiograph is very effective in identifying magnet twisting; it should be performed systematically after MRI or minimally on all suspected cases. PMID:23853406

Cuda, D; Murri, A; Succo, G

2013-04-01

21

Ventricular Assist Device implant (AB 5000) prototype cannula: In vitro assessment of MRI issues at 3Tesla  

Microsoft Academic Search

PURPOSE: To evaluate MRI issues at 3-Tesla for a ventricular assist device (VAD). METHODS: The AB5000 Ventricle with a prototype Nitinol wire-reinforced In-Flow Cannula and Out-Flow Cannula attached (Abiomed, Inc., Danvers, MA) was evaluated for magnetic field interactions, heating, and artifacts at 3-Tesla. MRI-related heating was assessed with the device in a gelled-saline-filled, head\\/torso phantom using a transmit\\/received RF body

Frank G Shellock; Samuel Valencerina

2008-01-01

22

Acute Posterior Ischemic Optic Neuropathy Mimicking Posterior Cerebral Artery Stroke Visualized by 3-Tesla MRI  

PubMed Central

Acute ischemic lesions of the posterior optic nerve and optic tract can produce a variety of visual field defects. A 71-year-old woman presented with acute hemianopia, which led to rt-PA thrombolysis for suspected posterior cerebral artery ischemia. 3-Tesla cMRI, however, revealed the cause to be an acute posterior ischemic optic neuropathy. Cases like this may be more common than thought and quite regularly overlooked in clinical practice, especially when there is no high-resolution MRI available. This case strengthens the importance of repeat MR imaging in patients with persistent visual field defects.

Menzel, Tilman; Kern, Rolf; Griebe, Martin; Hennerici, Michael; Fatar, Marc

2012-01-01

23

The effect of scanner sound in visual, motor, and auditory functional MRI  

Microsoft Academic Search

The potentially important effect of gradient switching sound on brain function during functional magnetic resonance imaging (fMRI) was studied by comparing experiments with low and high scanner sound levels. To provide a low sound level experiment, a sparse scanning method was used, characterized by long, 9 sec, periods of scanner silence interspersed with 1 sec echopla- nar imaging (EPI) bursts.

Michael R. Elliott; Richard W. Bowtell; Peter G. Morris

1999-01-01

24

Cerebral cortical microinfarcts at 7Tesla MRI in patients with early Alzheimer's disease.  

PubMed

Cerebral microinfarcts (CMIs) are a common finding in neuropathological studies of aging and dementia. Recently, it has become possible to detect CMIs in vivo. We studied CMI occurrence in 29 patients with mild cognitive impairment or early Alzheimer's disease (AD) and 22 non-demented individuals on 7Tesla MRI. CMI occurrence in patients (55%) and controls (45%) was not significantly different. In patients, CMI number tended to be related to microbleed number (p = 0.07). This first in vivo study of CMIs in early AD does not confirm findings from autopsy studies. Further studies are needed to clarify the role of CMIs in AD. PMID:24121967

van Veluw, Susanne J; Heringa, Sophie M; Kuijf, Hugo J; Koek, Huiberdina L; Luijten, Peter R; Biessels, Geert Jan

2014-01-01

25

Application of chemical exchange saturation transfer (CEST) MRI for endogenous contrast at 7 Tesla.  

PubMed

Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) indirectly images exchangeable solute protons resonating at frequencies different than bulk water. These solute protons are selectively saturated using low bandwidth RF irradiation and saturation is transferred to bulk water protons via chemical exchange, resulting in an attenuation of the measured water proton signal. CEST MRI is an advanced MRI technique with wide application potential due to the ability to examine complex molecular contributions. CEST MRI at high field (7 Tesla [7 T]) will improve the overall results due to increase in signal, T1 relaxation time, and chemical shift dispersion. Increased field strength translates to enhanced quantification of the metabolite of interest, allowing more fundamental studies on underlying pathophysiology. CEST contrast is affected by several tissue properties, such as the concentrations of exchange partners and their rate of proton exchange, whose effects have been examined and explored in this review. We have highlighted the background of CEST MRI, typical implementation strategy, and complications at 7 T. PMID:23402307

Dula, Adrienne N; Smith, Seth A; Gore, John C

2013-10-01

26

A Novel 16-Channel Receive Coil Array for Accelerated Upper Airway MRI at 3 Tesla  

PubMed Central

Upper airway MRI provides a non-invasive assessment of speech and swallowing disorders and sleep apnea. Recent work has demonstrated the value of high-resolution three-dimensional (3D) imaging and dynamic 2D imaging and the importance of further improvements in spatio-temporal resolution. The purpose of the study was to describe a novel 16-channel 3 Tesla receive coil that is highly sensitive to the human upper airway and investigate the performance of accelerated upper airway MRI with the coil. In 3D imaging of the upper airway during static posture, 6-fold acceleration is demonstrated using parallel imaging, potentially leading to capturing a whole 3D vocal tract with 1.25 mm isotropic resolution within 9 seconds of sustained sound production. Midsagittal spiral parallel imaging of vocal tract dynamics during natural speech production is demonstrated with 2 × 2 mm2 in-plane spatial and 84 ms temporal resolution.

Kim, Yoon-Chul; Hayes, Cecil E.; Narayanan, Shrikanth S.; Nayak, Krishna S.

2010-01-01

27

A Comprehensive Segmentation, Registration, and Cancer Detection Scheme on 3 Tesla In Vivo Prostate DCE MRI  

PubMed Central

Recently, high resolution 3 Tesla (T) Dynamic Contrast-Enhanced MRI (DCE-MRI) of the prostate has emerged as a promising technique for detecting prostate cancer (CaP). Computer-aided diagnosis (CAD) schemes for DCE-MRI data have thus far been primarily developed for breast cancer and typically involve model fitting of dynamic intensity changes as a function of contrast agent uptake by the lesion, as done by schemes such as the 3 time point (TP) scheme. Non-linear dimensionality reduction schemes such as locally linear embedding (LLE) have been previously shown to be useful in faithfully embedding high dimensional biomedical data into a lower dimensional subspace while preserving the non-linear geometry of the data manifold. In this paper, we present a novel unsupervised detection scheme for CaP from 3T DCE-MRI that combines LLE and consensus clustering to discriminate between tissue classes at the image pixel level. The methodology comprises 3 distinct steps. First, a multi-attribute active shape model is used to automatically segment the prostate boundary from in vivo 3 T MR imagery. A robust multimodal registration scheme is then used to non-linearly align corresponding whole mount histological and DCE-MRI sections from prostatectomy specimens to determine the spatial extent of CaP. LLE followed by consensus clustering is finally used to identify distinct clusters. Quantitative evaluation on 21 histology-MRI slice pairs against registered CaP ground truth yielded a maximum CaP detection sensitivity of 60.72% and specificity of 83.24% while the popular 3TP scheme gave an accuracy of 38.22%.

Viswanath, Satish; Bloch, Nicholas; Rofsky, Neil; Lenkinski, Robert; Genega, Elisabeth; Chappelow, Jonathan; Toth, Robert; Madabhushi, Anant

2009-01-01

28

A Comprehensive Segmentation, Registration, and Cancer Detection Scheme on 3 Tesla In Vivo Prostate DCE-MRI  

Microsoft Academic Search

\\u000a Recently, high resolution 3 Tesla (T) Dynamic Contrast-Enhanced MRI (DCE-MRI) of the prostate has emerged as a promising modality\\u000a for detecting prostate cancer (CaP). Computer-aided diagnosis (CAD) schemes for DCE-MRI data have thus far been primarily\\u000a developed for breast cancer and typically involve model fitting of dynamic intensity changes as a function of contrast agent\\u000a uptake by the lesion. Comparatively

Satish Viswanath; B. Nicolas Bloch; Elisabeth Genega; Neil Rofsky; Robert Lenkinski; Jonathan Chappelow; Robert Toth; Anant Madabhushi

29

MR Scanner Systems Should Be Adequately Characterized in Diffusion-MRI of the Breast  

PubMed Central

Breast imaging represents a relatively recent and promising field of application of quantitative diffusion-MRI techniques. In view of the importance of guaranteeing and assessing its reliability in clinical as well as research settings, the aim of this study was to specifically characterize how the main MR scanner system-related factors affect quantitative measurements in diffusion-MRI of the breast. In particular, phantom acquisitions were performed on three 1.5 T MR scanner systems by different manufacturers, all equipped with a dedicated multi-channel breast coil as well as acquisition sequences for diffusion-MRI of the breast. We assessed the accuracy, inter-scan and inter-scanner reproducibility of the mean apparent diffusion coefficient measured along the main orthogonal directions () as well as of diffusion-tensor imaging (DTI)-derived mean diffusivity (MD) measurements. Additionally, we estimated spatial non-uniformity of (NU) and MD (NUMD) maps. We showed that the signal-to-noise ratio as well as overall calibration of high strength diffusion gradients system in typical acquisition sequences for diffusion-MRI of the breast varied across MR scanner systems, introducing systematic bias in the measurements of diffusion indices. While and MD values were not appreciably different from each other, they substantially varied across MR scanner systems. The mean of the accuracies of measured and MD was in the range [?2.3%,11.9%], and the mean of the coefficients of variation for and MD measurements across MR scanner systems was 6.8%. The coefficient of variation for repeated measurements of both and MD was < 1%, while NU and NUMD values were <4%. Our results highlight that MR scanner system-related factors can substantially affect quantitative diffusion-MRI of the breast. Therefore, a specific quality control program for assessing and monitoring the performance of MR scanner systems for diffusion-MRI of the breast is highly recommended at every site, especially in multicenter and longitudinal studies.

Giannelli, Marco; Sghedoni, Roberto; Iacconi, Chiara; Iori, Mauro; Traino, Antonio Claudio; Guerrisi, Maria; Mascalchi, Mario; Toschi, Nicola; Diciotti, Stefano

2014-01-01

30

MR scanner systems should be adequately characterized in diffusion-MRI of the breast.  

PubMed

Breast imaging represents a relatively recent and promising field of application of quantitative diffusion-MRI techniques. In view of the importance of guaranteeing and assessing its reliability in clinical as well as research settings, the aim of this study was to specifically characterize how the main MR scanner system-related factors affect quantitative measurements in diffusion-MRI of the breast. In particular, phantom acquisitions were performed on three 1.5 T MR scanner systems by different manufacturers, all equipped with a dedicated multi-channel breast coil as well as acquisition sequences for diffusion-MRI of the breast. We assessed the accuracy, inter-scan and inter-scanner reproducibility of the mean apparent diffusion coefficient measured along the main orthogonal directions () as well as of diffusion-tensor imaging (DTI)-derived mean diffusivity (MD) measurements. Additionally, we estimated spatial non-uniformity of (NU) and MD (NUMD) maps. We showed that the signal-to-noise ratio as well as overall calibration of high strength diffusion gradients system in typical acquisition sequences for diffusion-MRI of the breast varied across MR scanner systems, introducing systematic bias in the measurements of diffusion indices. While and MD values were not appreciably different from each other, they substantially varied across MR scanner systems. The mean of the accuracies of measured and MD was in the range [-2.3%,11.9%], and the mean of the coefficients of variation for and MD measurements across MR scanner systems was 6.8%. The coefficient of variation for repeated measurements of both and MD was < 1%, while NU and NUMD values were <4%. Our results highlight that MR scanner system-related factors can substantially affect quantitative diffusion-MRI of the breast. Therefore, a specific quality control program for assessing and monitoring the performance of MR scanner systems for diffusion-MRI of the breast is highly recommended at every site, especially in multicenter and longitudinal studies. PMID:24489711

Giannelli, Marco; Sghedoni, Roberto; Iacconi, Chiara; Iori, Mauro; Traino, Antonio Claudio; Guerrisi, Maria; Mascalchi, Mario; Toschi, Nicola; Diciotti, Stefano

2014-01-01

31

Clinical Evaluation of Stereotactic Target Localization Using 3-Tesla MRI for Radiosurgery Planning  

SciTech Connect

Purpose: Increasing the magnetic resonance imaging (MRI) field strength can improve image resolution and quality, but concerns remain regarding the influence on geometric fidelity. The objectives of the present study were to spatially investigate the effect of 3-Tesla (3T) MRI on clinical target localization for stereotactic radiosurgery. Methods and Materials: A total of 39 patients were enrolled in a research ethics board-approved prospective clinical trial. Imaging (1.5T and 3T MRI and computed tomography) was performed after stereotactic frame placement. Stereotactic target localization at 1.5T vs. 3T was retrospectively analyzed in a representative cohort of patients with tumor (n = 4) and functional (n = 5) radiosurgical targets. The spatial congruency of the tumor gross target volumes was determined by the mean discrepancy between the average gross target volume surfaces at 1.5T and 3T. Reproducibility was assessed by the displacement from an averaged surface and volume congruency. Spatial congruency and the reproducibility of functional radiosurgical targets was determined by comparing the mean and standard deviation of the isocenter coordinates. Results: Overall, the mean absolute discrepancy across all patients was 0.67 mm (95% confidence interval, 0.51-0.83), significantly <1 mm (p < .010). No differences were found in the overall interuser target volume congruence (mean, 84% for 1.5T vs. 84% for 3T, p > .4), and the gross target volume surface mean displacements were similar within and between users. The overall average isocenter coordinate discrepancy for the functional targets at 1.5T and 3T was 0.33 mm (95% confidence interval, 0.20-0.48), with no patient-specific differences between the mean values (p >.2) or standard deviations (p >.1). Conclusion: Our results have provided clinically relevant evidence supporting the spatial validity of 3T MRI for use in stereotactic radiosurgery under the imaging conditions used.

MacFadden, Derek [University of Toronto Faculty of Medicine, Toronto, ON (Canada); Zhang Beibei; Brock, Kristy K. [Radiation Medicine Program, Princess Margaret Hospital, University Health Network, Toronto, ON (Canada); Hodaie, Mojgan [Division of Neurosurgery, Toronto Western Hospital, Toronto, ON (Canada); Laperriere, Normand [Radiation Medicine Program, Princess Margaret Hospital, University Health Network, Toronto, ON (Canada); Department of Radiation Oncology, University of Toronto, Toronto, ON (Canada); Schwartz, Michael [Division of Neurosurgery, Toronto Western Hospital, Toronto, ON (Canada); Tsao, May [Department of Radiation Oncology, University of Toronto, Toronto, ON (Canada); Department of Radiation Oncology, Sunnybrook Regional Cancer Centre, Toronto, ON (Canada); Stainsby, Jeffrey [Applied Science Laboratories, GE Healthcare, Mississauga, ON (Canada); Lockwood, Gina [Radiation Medicine Program, Princess Margaret Hospital, University Health Network, Toronto, ON (Canada); Mikulis, David [Department of Medical Imaging, University Health Network, Toronto, ON (Canada); Menard, Cynthia, E-mail: cynthia.menard@rmp.uhn.on.c [Radiation Medicine Program, Princess Margaret Hospital, University Health Network, Toronto, ON (Canada); Department of Radiation Oncology, University of Toronto, Toronto, ON (Canada)

2010-04-15

32

Ultrahigh-Field MRI in Human Ischemic Stroke - a 7 Tesla Study  

PubMed Central

Introduction Magnetic resonance imaging (MRI) using field strengths up to 3 Tesla (T) has proven to be a powerful tool for stroke diagnosis. Recently, ultrahigh-field (UHF) MRI at 7 T has shown relevant diagnostic benefits in imaging of neurological diseases, but its value for stroke imaging has not been investigated yet. We present the first evaluation of a clinically feasible stroke imaging protocol at 7 T. For comparison an established stroke imaging protocol was applied at 3 T. Methods In a prospective imaging study seven patients with subacute and chronic stroke were included. Imaging at 3 T was immediately followed by 7 T imaging. Both protocols included T1-weighted 3D Magnetization-Prepared Rapid-Acquired Gradient-Echo (3D-MPRAGE), T2-weighted 2D Fluid Attenuated Inversion Recovery (2D-FLAIR), T2-weighted 2D Fluid Attenuated Inversion Recovery (2D-T2-TSE), T2* weighted 2D Fast Low Angle Shot Gradient Echo (2D-HemoFLASH) and 3D Time-of-Flight angiography (3D-TOF). Results The diagnostic information relevant for clinical stroke imaging obtained at 3 T was equally available at 7 T. Higher spatial resolution at 7 T revealed more anatomical details precisely depicting ischemic lesions and periinfarct alterations. A clear benefit in anatomical resolution was also demonstrated for vessel imaging at 7 T. RF power deposition constraints induced scan time prolongation and reduced brain coverage for 2D-FLAIR, 2D-T2-TSE and 3D-TOF at 7 T versus 3 T. Conclusions The potential of 7 T MRI for human stroke imaging is shown. Our pilot study encourages a further evaluation of the diagnostic benefit of stroke imaging at 7 T in a larger study.

Bauer, Miriam; Stengl, Katharina L.; Mutke, Matthias A.; Tovar-Martinez, Elena; Wuerfel, Jens; Endres, Matthias; Niendorf, Thoralf; Sobesky, Jan

2012-01-01

33

Ventricular Assist Device implant (AB 5000) prototype cannula: In vitro assessment of MRI issues at 3-Tesla  

PubMed Central

Purpose To evaluate MRI issues at 3-Tesla for a ventricular assist device (VAD). Methods The AB5000 Ventricle with a prototype Nitinol wire-reinforced In-Flow Cannula and Out-Flow Cannula attached (Abiomed, Inc., Danvers, MA) was evaluated for magnetic field interactions, heating, and artifacts at 3-Tesla. MRI-related heating was assessed with the device in a gelled-saline-filled, head/torso phantom using a transmit/received RF body coil while performing MRI at a whole body averaged SAR of 3-W/kg for 15-min. Artifacts were assessed for the main metallic component of this VAD (atrial cannula) using T1-weighted, spin echo and gradient echo pulse sequences. Results The AB5000 Ventricle with the prototype In-Flow Cannula and Out-Flow Cannula attached showed relatively minor magnetic field interactions that will not cause movement in situ. Heating was not excessive (highest temperature change, +0.8°C). Artifacts may create issues for diagnostic imaging if the area of interest is in the same area or close to the implanted metallic component of this VAD (i.e., the venous cannula). Conclusion The results of this investigation demonstrated that it would be acceptable for a patient with this VAD (AB5000 Ventricle with a prototype Nitinol wire-reinforced In-Flow Cannula and Out-Flow Cannula attached) to undergo MRI at 3-Tesla or less. Notably, it is likely that the operation console for this device requires positioning a suitable distance (beyond the 100 Gauss line or in the MR control room) from the 3-Tesla MR system to ensure proper function of the VAD.

Shellock, Frank G; Valencerina, Samuel

2008-01-01

34

High-resolution phased-array MRI of the human brain at 7 tesla: initial experience in multiple sclerosis patients  

Microsoft Academic Search

Recent advancement for magnetic resonance imaging (MRI) involves the incorporation of higher-field strengths. Although imagers with higher magnetic field strengths were developed and tested in research labs, the direct application to patient MR studies have been extremely limited. Imaging at 7 Tesla (7T) affords advantages in signal-to-noise ratio and image contrast and resolution; however, these benefits can only be realized

Meredith Metcalf; Duan Xu; Darin T Okuda; Lucas Carvajal; Radhika Srinivasan; Douglas A C Kelley; Pratik Mukherjee; Sarah J Nelson; Daniel B Vigneron; Daniel Pelletier

2010-01-01

35

Ubiquitous remote operation collaborative interface for MRI scanners  

NASA Astrophysics Data System (ADS)

We have developed a remote control interface for research class magnetic resonance imaging (MRI) spectrometers. The goal of the interface is to provide a better collaborative environment for geographically dispersed researchers and a tool that can teach students of medical imaging in a network-based laboratory using state-of-the-art MR instrumentation that would not otherwise be available. The interface for the remote operator(s) is now ubiquitous web browser, which was chosen for the ease of controlling the operator interface, the display of both image and text information, and the wide availability on many computer platforms. The remote operator is presented with an active display in which they may select and control most of the parameters in the MRI experiment. The MR parameters are relayed via web browser to a CGI program running in a standard web server, which passes said parameters to the MRI manufacturers control software. The data returned to the operator(s) consists of the parameters used in acquiring that image, a flat 8-bit grayscale GIF representation of the image, and a 16-bit grayscale image that can be viewed by an appropriate application. It is obvious that the utility of this interface would be helpful for researchers of regional and national facilities to more closely collaborate with colleagues across their region, the nation, or the world. And medical imaging students can put much of their classroom discussions into practice on machinery that would not normally be available to them.

Morris, H. Douglas

2001-05-01

36

Use of a clinical MRI scanner for preclinical research on rats  

Microsoft Academic Search

This study evaluated the feasibility of imaging rat brains using a human whole-body 3-T magnetic resonance imaging (MRI) scanner\\u000a with specially developed transmit-and-receive radiofrequency coils. The T1- and T2-weighted images obtained showed reasonable contrast. Acquired contrast-free time-of-flight magnetic resonance angiography\\u000a images clearly showed the cortical middle cerebral artery (MCA) branches, and interhemispheric differences could be observed.\\u000a Dynamic susceptibility contrast MRI

Akihide Yamamoto; Hiroshi Sato; Jun-ichiro Enmi; Kenji Ishida; Takayuki Ose; Atsuomi Kimura; Hideaki Fujiwara; Hiroshi Watabe; Takuya Hayashi; Hidehiro Iida

2009-01-01

37

Occupational exposure measurements of static and pulsed gradient magnetic fields in the vicinity of MRI scanners.  

PubMed

Recent advances in magnetic resonance imaging (MRI) have increased occupational exposure to magnetic fields. In this study, we examined the assessment of occupational exposure to gradient magnetic fields and time-varying magnetic fields generated by motion in non-homogeneous static magnetic fields of MRI scanners. These magnetic field components can be measured simultaneously with an induction coil setup that detects the time rate of change of magnetic flux density (dB/dt). The setup developed was used to measure the field components around two MRI units (1 T open and 3 T conventional). The measured values can be compared with dB/dt reference levels derived from magnetic flux density reference levels given by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). The measured motion-induced dB/dt values were above the dB/dt reference levels for both MRI units. The measured values for the gradient fields (echo planar imaging (EPI) and fast field echo (FFE) sequences) also exceeded the dB/dt reference levels in positions where the medical staff may have access during interventional procedures. The highest motion-induced dB/dt values were 0.7 T s(-1) for the 1 T scanner and 3 T s(-1) for the 3 T scanner when only the static field was present. Even higher values (6.5 T s(-1)) were measured for simultaneous exposure to motion-induced and gradient fields in the vicinity of the 3 T scanner. PMID:19293469

Kännälä, Sami; Toivo, Tim; Alanko, Tommi; Jokela, Kari

2009-04-01

38

EEG-MRI co-registration and sensor labeling using a 3D laser scanner.  

PubMed

This paper deals with the co-registration of an MRI scan with EEG sensors. We set out to evaluate the effectiveness of a 3D handheld laser scanner, a device that is not widely used for co-registration, applying a semi-automatic procedure that also labels EEG sensors. The scanner acquired the sensors' positions and the face shape, and the scalp mesh was obtained from the MRI scan. A pre-alignment step, using the position of three fiducial landmarks, provided an initial value for co-registration, and the sensors were automatically labeled. Co-registration was then performed using an iterative closest point algorithm applied to the face shape. The procedure was conducted on five subjects with two scans of EEG sensors and one MRI scan each. The mean time for the digitization of the 64 sensors and three landmarks was 53 s. The average scanning time for the face shape was 2 min 6 s for an average number of 5,263 points. The mean residual error of the sensors co-registration was 2.11 mm. These results suggest that the laser scanner associated with an efficient co-registration and sensor labeling algorithm is sufficiently accurate, fast and user-friendly for longitudinal and retrospective brain sources imaging studies. PMID:21140291

Koessler, L; Cecchin, T; Caspary, O; Benhadid, A; Vespignani, H; Maillard, L

2011-03-01

39

Functionality of veterinary identification microchips following low- (0.5 tesla) and high-field (3 tesla) magnetic resonance imaging.  

PubMed

The ability to read patient identification microchips relies on the use of radiofrequency pulses. Since radiofrequency pulses also form an integral part of the magnetic resonance imaging (MRI) process, the possibility of loss of microchip function during MRI scanning is of concern. Previous clinical trials have shown microchip function to be unaffected by MR imaging using a field strength of 1 Tesla and 1.5. As veterinary MRI scanners range widely in field strength, this study was devised to determine whether exposure to lower or higher field strengths than 1 Tesla would affect the function of different types of microchip. In a phantom study, a total of 300 International Standards Organisation (ISO)-approved microchips (100 each of three different types: ISO FDX-B 1.4 × 9 mm, ISO FDX-B 2.12 × 12 mm, ISO HDX 3.8 × 23 mm) were tested in a low field (0.5) and a high field scanner (3.0 Tesla). A total of 50 microchips of each type were tested in each scanner. The phantom was composed of a fluid-filled freezer pack onto which a plastic pillow and a cardboard strip with affixed microchips were positioned. Following an MRI scan protocol simulating a head study, all of the microchips were accurately readable. Neither 0.5 nor 3 Tesla imaging affected microchip function in this study. PMID:23763334

Piesnack, Susann; Frame, Mairi E; Oechtering, Gerhard; Ludewig, Eberhard

2013-01-01

40

Awake language mapping and 3-Tesla intraoperative MRI-guided volumetric resection for gliomas in language areas.  

PubMed

The use of both awake surgery and intraoperative MRI (iMRI) has been reported to optimize the maximal safe resection of gliomas. However, there has been little research into combining these two demanding procedures. We report our unique experience with, and methodology of, awake surgery in a movable iMRI system, and we quantitatively evaluate the contribution of the combination on the extent of resection (EOR) and functional outcome of patients with gliomas involving language areas. From March 2011 to November 2011, 30 consecutive patients who underwent awake surgery with iMRI guidance were prospectively investigated. The EOR was assessed by volumetric analysis. Language assessment was conducted before surgery and 1 week, 1 month, 3 months and 6 months after surgery using the Aphasia Battery of Chinese. Awake language mapping integrated with 3.0 Tesla iMRI was safely performed for all patients. An additional resection was conducted in 11 of 30 patients (36.7%) after iMRI. The median EOR significantly increased from 92.5% (range, 75.1-97.0%) to 100% (range, 92.6-100%) as a result of iMRI (p<0.01). Gross total resection was achieved in 18 patients (60.0%), and in seven of those patients (23.3%), the gross total resection could be attributed to iMRI. A total of 12 patients (40.0%) suffered from transient language deficits; however, only one (3.3%) patient developed a permanent deficit. This study demonstrates the potential utility of combining awake craniotomy with iMRI; it is safe and reliable to perform awake surgery using a movable iMRI. PMID:23850046

Lu, Junfeng; Wu, Jinsong; Yao, Chengjun; Zhuang, Dongxiao; Qiu, Tianming; Hu, Xiaobing; Zhang, Jie; Gong, Xiu; Liang, Weimin; Mao, Ying; Zhou, Liangfu

2013-09-01

41

Multimodal image registration of ex vivo 4 Tesla MRI with whole mount histology for prostate cancer detection  

NASA Astrophysics Data System (ADS)

In this paper we present novel methods for registration and subsequent evaluation of whole mount prostate histological sections to corresponding 4 Tesla ex vivo magnetic resonance imaging (MRI) slices to complement our existing computer-aided diagnosis (CAD) system for detection of prostatic adenocarcinoma from high resolution MRI. The CAD system is trained using voxels labeled as cancer on MRI by experts who visually aligned histology with MRI. To address voxel labeling errors on account of manual alignment and delineation, we have developed a registration method called combined feature ensemble mutual information (COFEMI) to automatically map spatial extent of prostate cancer from histology onto corresponding MRI for prostatectomy specimens. Our method improves over intensity-based similarity metrics (mutual information) by incorporating unique information from feature spaces that are relatively robust to intensity artifacts and which accentuate the structural details in the target and template images to be registered. Our registration algorithm accounts for linear gland deformations in the histological sections resulting from gland fixing and serial sectioning. Following automatic registration of MRI and histology, cancer extent from histological sections are mapped to the corresponding registered MRI slices. The manually delineated cancer areas on MRI obtained via manual alignment of histological sections and MRI are compared with corresponding cancer extent obtained via COFEMI by a novel registration evaluation technique based on use of non-linear dimensionality reduction (locally linear embedding (LLE)). The cancer map on MRI determined by COFEMI was found to be significantly more accurate compared to the manually determined cancer mask. The performance of COFEMI was also found to be superior compared to image intensity-based mutual information registration.

Chappelow, Jonathan; Madabhushi, Anant; Rosen, Mark; Tomaszeweski, John; Feldman, Michael

2007-03-01

42

COMPET: High resolution high sensitivity MRI compatible pre-clinical PET scanner  

NASA Astrophysics Data System (ADS)

COMPET is a pre-clinical MRI compatible PET scanner which decouples sensitivity and resolution by the use of a novel detector design. The detector has been built using 8×8cm2 square layers consisting of 30 LYSO crystals (2×3×80mm2) interleaved with 24 Wavelength Shifting Fibers (WLS) (3×1×80mm3). By stacking several layers into a module, the point-of-interaction (POI) can be measured in 3D. Four layers form a PET ring where the sensitivity can be increased by stacking several layers. The layers can be stacked so that no inter-crystal or inter-module gap is formed. COMPET has used four assembled layers for module and scanner characterization. The modules are connected to the COMPET data-acquisition chain and the reconstructed images are produced with the novel geometry-independent COMPET image reconstruction algorithm. Time and energy resolution have been resolved and found to be around 4 ns and 14% respectively. Tests for MRI interference and count rate performance have been carried out. The reconstruction algorithm has been verified with data acquired by means of a COMPET full ring PET scanner.

Hines, Kim-Eigard; Bolle, Erlend; Rissi, Michael; Volgyes, David; Dorholt, Ole; Røhne, Ole; Stapnes, Steinar; Bjaalie, Jan G.; Skretting, Arne

2013-12-01

43

Validation of radiocarpal joint contact models based on images from a clinical MRI scanner  

PubMed Central

This study was undertaken to assess MRI-based radiocarpal surface contact models of functional loading in a clinical MRI scanner for future in vivo studies, by comparison with experimental measures from three cadaver forearm specimens. Experimental data was acquired using a Tekscan sensor during simulated light grasp. MR images were used to obtain model geometry and kinematics (image registration). Peak and average contact pressures, contact forces and contact areas were determined in the radiolunate and radioscaphoid joints. Contact area was also measured directly from MR images acquired with load and compared to model data. Based on the validation criteria (within 25% of experimental data), out of the six articulations (three specimens with two articulations each), two met the criterion for average contact pressure (0%, 14%); one for peak pressure (20%); one for contact force (5%); four for contact area with respect to experiment (8%, 13%, 19%, 23%), and three contact areas met the criterion with respect to direct measurements (14%, 21%, 21%). Absolute differences between model and experimental peak contact pressures were reasonably low (within 2.5 MPa). Overall, the results indicate that MRI-based models generated from 3T clinical MR scanner appear sufficient to obtain clinically relevant data.

Johnson, Joshua E.; McIff, Terence E.; Lee, Phil; Toby, E. Bruce; Fischer, Kenneth J.

2012-01-01

44

A comprehensive segmentation, registration, and cancer detection scheme on 3 Tesla in vivo prostate DCE-MRI.  

PubMed

Recently, high resolution 3 Tesla (T) Dynamic Contrast-Enhanced MRI (DCE-MRI) of the prostate has emerged as a promising modality for detecting prostate cancer (CaP). Computer-aided diagnosis (CAD) schemes for DCE-MRI data have thus far been primarily developed for breast cancer and typically involve model fitting of dynamic intensity changes as a function of contrast agent uptake by the lesion. Comparatively there is relatively little work in developing CAD schemes for prostate DCE-MRI. In this paper, we present a novel unsupervised detection scheme for CaP from 3 T DCE-MRI which comprises 3 distinct steps. First, a multi-attribute active shape model is used to automatically segment the prostate boundary from 3 T in vivo MR imagery. A robust multimodal registration scheme is then used to non-linearly align corresponding whole mount histological and DCE-MRI sections from prostatectomy specimens to determine the spatial extent of CaP. Non-linear dimensionality reduction schemes such as locally linear embedding (LLE) have been previously shown to be useful in projecting such high dimensional biomedical data into a lower dimensional subspace while preserving the non-linear geometry of the data manifold. DCE-MRI data is embedded via LLE and then classified via unsupervised consensus clustering to identify distinct classes. Quantitative evaluation on 21 histology-MRI slice pairs against registered CaP ground truth estimates yielded a maximum CaP detection accuracy of 77.20% while the popular three time point (3TP) scheme yielded an accuracy of 67.37%. PMID:18979803

Viswanath, Satish; Bloch, B Nicolas; Genega, Elisabeth; Rofsky, Neil; Lenkinski, Robert; Chappelow, Jonathan; Toth, Robert; Madabhushi, Anant

2008-01-01

45

Preparing children with a mock scanner training protocol results in high quality structural and functional MRI scans.  

PubMed

We evaluated the use of a mock scanner training protocol as an alternative for sedation and for preparing young children for (functional) magnetic resonance imaging (MRI). Children with severe mental retardation or developmental disorders were excluded. A group of 90 children (median age 6.5 years, range 3.65-14.5 years) participated in this study. Children were referred to the actual MRI investigation only when they passed the training. We assessed the pass rate of the mock scanner training sessions. In addition, the quality of both structural and functional MRI (fMRI) scans was rated on a semi-quantitative scale. The overall pass rate of the mock scanner training sessions was 85/90. Structural scans of diagnostic quality were obtained in 81/90 children, and fMRI scans with sufficient quality for further analysis were obtained in 30/43 of the children. Even in children under 7 years of age, who are generally sedated, the success rate of structural scans with diagnostic quality was 53/60. FMRI scans with sufficient quality were obtained in 23/36 of the children in this younger age group. The association between age and proportion of children with fMRI scans of sufficient quality was not statistically significant. We conclude that a mock MRI scanner training protocol can be useful to prepare children for a diagnostic MRI scan. It may reduce the need for sedation in young children undergoing MRI. Our protocol is also effective in preparing young children to participate in fMRI investigations. PMID:20225122

de Bie, Henrica M A; Boersma, Maria; Wattjes, Mike P; Adriaanse, Sofie; Vermeulen, R Jeroen; Oostrom, Kim J; Huisman, Jaap; Veltman, Dick J; Delemarre-Van de Waal, Henriette A

2010-09-01

46

Preparing children with a mock scanner training protocol results in high quality structural and functional MRI scans  

PubMed Central

We evaluated the use of a mock scanner training protocol as an alternative for sedation and for preparing young children for (functional) magnetic resonance imaging (MRI). Children with severe mental retardation or developmental disorders were excluded. A group of 90 children (median age 6.5 years, range 3.65–14.5 years) participated in this study. Children were referred to the actual MRI investigation only when they passed the training. We assessed the pass rate of the mock scanner training sessions. In addition, the quality of both structural and functional MRI (fMRI) scans was rated on a semi-quantitative scale. The overall pass rate of the mock scanner training sessions was 85/90. Structural scans of diagnostic quality were obtained in 81/90 children, and fMRI scans with sufficient quality for further analysis were obtained in 30/43 of the children. Even in children under 7 years of age, who are generally sedated, the success rate of structural scans with diagnostic quality was 53/60. FMRI scans with sufficient quality were obtained in 23/36 of the children in this younger age group. The association between age and proportion of children with fMRI scans of sufficient quality was not statistically significant. We conclude that a mock MRI scanner training protocol can be useful to prepare children for a diagnostic MRI scan. It may reduce the need for sedation in young children undergoing MRI. Our protocol is also effective in preparing young children to participate in fMRI investigations.

Boersma, Maria; Wattjes, Mike P.; Adriaanse, Sofie; Vermeulen, R. Jeroen; Oostrom, Kim J.; Huisman, Jaap; Veltman, Dick J.; Delemarre-Van de Waal, Henriette A.

2010-01-01

47

An in vitro assessment of MRI issues at 3-Tesla for antimicrobial, silver-containing wound dressings?.  

PubMed

Although no reports of adverse events have been published to date, the presence of metallic dressing ingredients may present an magnetic resonance imaging (MRI) safety concern for patients using silver-containing wound dressings. The purpose of this in vitro study was to test magnetic field interactions (ie, translational attraction and torque), heating, artifacts, and conductivity (ie, electrical resistance) when using MRI at 3-Tesla for two (nonborder and border) silver-containing wound dressings. The results indicated the dressings displayed no magnetic field interactions (deflection angle 0?; no torque), and in each case, MRI-related heating effects were at the same levels as the background temperature increases (ie, <1.8?C). The dressings created extremely subtle artifacts (one-for-one relationship) on the MR images. With regard to the conductivity assessments, the average resistance values were 20 kOhm and 1.1 kOhm, respectively, for the nonborder and border wound dressings, which were acceptable levels. The findings show the two silver-containing wound dressings tested will not pose hazards or risks to patients and, thus, are considered "MR safe" according to the current labeling terminology used for medical products, and each dressing may be left in place when a patient undergoes an MRI examination. To date, only a hydrofiber silver-containing dressing has been tested for MRI safety. Because of potential variances in material characteristics, MRI test results are specific to the dressings tested and cannot be applied to other products. Future studies to define the level of silver concentration in dressings that may pose a hazard for performing an MRI are warranted. PMID:23134899

Escher, Kirin B; Shellock, Frank G

2012-11-01

48

Acoustic pressure waves induced in human heads by RF pulses from high-field MRI scanners.  

PubMed

The current evolution toward greater image resolution from magnetic resonance image (MRI) scanners has prompted the exploration of higher strength magnetic fields and use of higher levels of radio frequencies (RFs). Auditory perception of RF pulses by humans has been reported during MRI with head coils. It has shown that the mechanism of interaction for the auditory effect is caused by an RF pulse-induced thermoelastic pressure wave inside the head. We report a computational study of the intensity and frequency of thermoelastic pressure waves generated by RF pulses in the human head inside high-field MRI and clinical scanners. The U.S. Food and Drug Administration (U.S. FDA) guides limit the local specific absorption rate (SAR) in the body-including the head-to 8 W kg(-1). We present results as functions of SAR and show that for a given SAR the peak acoustic pressures generated in the anatomic head model were essentially the same at 64, 300, and 400 MHz (1.5, 7.0, and 9.4 T). Pressures generated in the anatomic head are comparable to the threshold pressure of 20 mPa for sound perception by humans at the cochlea for 4 W kg(-1). Moreover, results indicate that the peak acoustic pressure in the brain is only 2 to 3 times the auditory threshold at the U.S. FDA guideline of 8 W kg(-1). Even at a high SAR of 20 W kg(-1), where the acoustic pressure in the brain could be more than 7 times the auditory threshold, the sound pressure levels would not be more than 17 db above threshold of perception at the cochlea. PMID:20220368

Lin, James C; Wang, Zhangwei

2010-04-01

49

Studies of the interactions of an MRI system with the shielding in a combined PET/MRI scanner  

PubMed Central

A positron emission tomography (PET) system or ‘insert’ has been constructed for placement and operation in the bore of a small animal magnetic resonance imaging (MRI) scanner to allow simultaneous MR and PET imaging. The insert contains electronics, components with a variety of magnetic properties, and large continuous sheets of metal— all characteristics of an object that should, by conventional wisdom, never be placed in the bore of an MR scanner, especially near the imaging volume. There are a variety of ways the two systems might be expected to interact that could negatively impact the performance of either or both. In this article, the interaction mechanisms, particularly the impacts of the PET insert and shielding on MR imaging, are defined and explored. Additionally, some of the difficulties in quantifying errors introduced into the MR images as a result of the presence of the PET components are demonstrated. Several different approaches are used to characterize image artifacts and determine optimal placement of the shielding. Data are also presented that suggest ways the shielding could be modified to reduce errors and enable placement closer to the isocenter of the magnet.

Peng, Bo J.; Walton, Jeffrey H.; Cherry, Simon R.; Willig-Onwuachi, Jacob

2010-01-01

50

MRI from 400 gauss to 1.5 tesla and beyond  

Microsoft Academic Search

Magnetic Resonance Imaging (MRI) is arguably the most novel and important medical imaging modality since the advent of the X-ray. MRI grew out of the long development of atomic spectroscopy, atomic and molecular beam resonance and, finally, nuclear magnetic resonance (NMR) in condensed matter. The operation and economics of MRI systems depend on the performance of magnets, pulsed magnetic field

William Edelstein

2006-01-01

51

The Roles of Functional MRI in MR-Guided Neurosurgery in a Combined 1.5 Tesla MR-Operating Room  

Microsoft Academic Search

\\u000a \\u000a Background and Purpose. During MR-guided neurosurgical procedures performed in a combined 1.5 Tesla MR-operating room (MR-OR), we have successfully\\u000a implemented and validated a functional MRI (fMRI) scheme for efficiently localizing eloquent functional areas and assessing\\u000a their proximity to a lesion volume immediately prior to the craniotomy.\\u000a \\u000a \\u000a \\u000a Methods. The fMRI examination consists of a dynamical blood oxygenation level dependent (BOLD) MR

H. Liu; W. A. Hall; C. L. Truwit

52

Lesion morphology at 7 Tesla MRI differentiates Susac syndrome from multiple sclerosis  

Microsoft Academic Search

BACKGROUND: Although an orphan disease with still obscure aetiopathogenesis, Susac syndrome has to be considered as differential diagnosis in multiple sclerosis (MS), since its clinical presentation and paraclinical features including routine magnetic resonance imaging (MRI) findings partially overlap. OBJECTIVE: We aimed to study a potential benefit of 7T MRI for (i) the differentiation between Susac syndrome and MS and (ii)

J. Wuerfel; T. Sinnecker; E. B. Ringelstein; W. Schwindt; T. Niendorf; F. Paul; I. Kleffner; J. Dorr

2012-01-01

53

Iron Accumulation in Deep Cortical Layers Accounts for MRI Signal Abnormalities in ALS: Correlating 7 Tesla MRI and Pathology  

PubMed Central

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by cortical and spinal motor neuron dysfunction. Routine magnetic resonance imaging (MRI) studies have previously shown hypointense signal in the motor cortex on T2-weighted images in some ALS patients, however, the cause of this finding is unknown. To investigate the utility of this MR signal change as a marker of cortical motor neuron degeneration, signal abnormalities on 3T and 7T MR images of the brain were compared, and pathology was obtained in two ALS patients to determine the origin of the motor cortex hypointensity. Nineteen patients with clinically probable or definite ALS by El Escorial criteria and 19 healthy controls underwent 3T MRI. A 7T MRI scan was carried out on five ALS patients who had motor cortex hypointensity on the 3T FLAIR sequence and on three healthy controls. Postmortem 7T MRI of the brain was performed in one ALS patient and histological studies of the brains and spinal cords were obtained post-mortem in two patients. The motor cortex hypointensity on 3T FLAIR images was present in greater frequency in ALS patients. Increased hypointensity correlated with greater severity of upper motor neuron impairment. Analysis of 7T T2*-weighted gradient echo imaging localized the signal alteration to the deeper layers of the motor cortex in both ALS patients. Pathological studies showed increased iron accumulation in microglial cells in areas corresponding to the location of the signal changes on the 3T and 7T MRI of the motor cortex. These findings indicate that the motor cortex hypointensity on 3T MRI FLAIR images in ALS is due to increased iron accumulation by microglia.

Kwan, Justin Y.; Jeong, Suh Young; Van Gelderen, Peter; Deng, Han-Xiang; Quezado, Martha M.; Danielian, Laura E.; Butman, John A.; Chen, Lingye; Bayat, Elham; Russell, James; Siddique, Teepu; Duyn, Jeff H.; Rouault, Tracey A.; Floeter, Mary Kay

2012-01-01

54

A 32-Channel Lattice Transmission Line Array for Parallel Transmit and Receive MRI at 7 Tesla  

PubMed Central

Transmit and receive RF coil arrays have proven to be particularly beneficial for ultra-high-field MR. Transmit coil arrays enable such techniques as B1+ shimming to substantially improve transmit B1 homogeneity compared to conventional volume coil designs, and receive coil arrays offer enhanced parallel imaging performance and SNR. Concentric coil arrangements hold promise for developing transceiver arrays incorporating large numbers of coil elements. At magnetic field strengths of 7 tesla and higher where the Larmor frequencies of interest can exceed 300 MHz, the coil array design must also overcome the problem of the coil conductor length approaching the RF wavelength. In this study, a novel concentric arrangement of resonance elements built from capacitively-shortened half-wavelength transmission lines is presented. This approach was utilized to construct an array with whole-brain coverage using 16 transceiver elements and 16 receive-only elements, resulting in a coil with a total of 16 transmit and 32 receive channels.

Adriany, Gregor; Auerbach, Edward J.; Snyder, Carl J.; Gozubuyuk, Ark; Moeller, Steen; Ritter, Johannes; van de Moortele, Pierre-Francois; Vaughan, Tommy; Ugurbil, Kamil

2010-01-01

55

Whole brain quantitative T2 MRI across multiple scanners with dual echo FSE: Applications to AD, MCI, and normal aging  

PubMed Central

The ability to pool data from multiple MRI scanners is becoming increasingly important with the influx in multi-site research studies. Fast spin echo (FSE) dual spin echo sequences are often chosen for such studies based principally on their short acquisition time and clinically useful contrasts they provide for assessing gross pathology. The practicality of measuring FSE-T2 relaxation properties has rarely been assessed. Here, FSE-T2 relaxation properties are examined across the three main scanner vendors (General Electric (GE), Philips, and Siemens). The American College of Radiology (ACR) phantom was scanned on four 1.5T platforms (two GE, one Philips, and one Siemens) to determine if the dual echo pulse sequence is susceptible to vendor-based variance. In addition, data from 85 subjects spanning the spectrum of normal aging, mild cognitive impairment (MCI), and Alzheimer’s disease (AD) was obtained from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) to affirm the presence of any phantom based between vendor variance and determine the relationship between this variance and disease. FSE-T2 relaxation properties, including peak FSE-T2 and histogram width, were calculated for each phantom and human subject. Direct correspondence was found between the phantom and human subject data. Peak FSE-T2 of Siemens scanners was consistently at least 20ms prolonged compared to GE and Philips. Siemens scanners showed broader FSE-T2 histograms than the other scanners. Greater variance was observed across GE scanners than either Philips or Siemens. FSE-T2 differences were much greater with scanner vendor than between diagnostic groups, as no significant changes in peak FSE-T2 or histogram width between normal aged, MCI, and AD subject groups were observed. These results indicate that whole brain histogram measures are not sensitive enough to detect FSE-T2 changes between normal aging, MCI, and AD and that FSE-T2 is highly variable across scanner vendors.

Bauer, Corinna M; Jara, Hernan; Killiany, Ron

2010-01-01

56

3D 23Na MRI of human skeletal muscle at 7 Tesla: initial experience  

PubMed Central

Objective To evaluate healthy skeletal muscle pre- and post-exercise via 7 T 23Na MRI and muscle proton T2 mapping, and to evaluate diabetic muscle pre- and post-exercise via 7 T 23Na MRI. Methods The calves of seven healthy subjects underwent imaging pre- and post-exercise via 7 T 23Na MRI (3D fast low angle shot, TR/TE=80 ms/0.160 ms, 4 mm × 4 mm × 4 mm) and 1 week later by 1H MRI (multiple spin-echo sequence, TR/TE=3,000 ms/15–90 ms). Four type 2 diabetics also participated in the 23Na MRI protocol. Pre- and post-exercise sodium signal intensity (SI) and proton T2 relaxation values were measured/calculated for soleus (S), gastrocnemius (G), and a control, tibialis anterior (TA). Two-tailed t tests were performed. Results In S/G in healthy subjects post-exercise, sodium SI increased 8–13% (p<0.03), then decreased (t1/2=22 min), and 1H T2 values increased 12–17% (p<0.03), then decreased (t1/2=12–15 min). In TA, no significant changes in sodium SI or 1H T2 values were seen (?2.4 to 1%, p>0.17). In S/G in diabetics, sodium SI increased 10–11% (p<0.04), then decreased (t1/2=27–37 min) without significant change in the TA SI (?3.6%, p= 0.066). Conclusion It is feasible to evaluate skeletal muscle via 3D 23Na MRI at 7 T. Post-exercise muscle 1H T2 values return to baseline more rapidly than sodium SI. Diabetics may demonstrate delayed muscle sodium SI recovery compared with healthy subjects.

Wang, Ligong; Schweitzer, Mark E.; Regatte, Ravinder R.

2013-01-01

57

Assessment of MRI issues at 3-Tesla for metallic surgical implants: findings applied to 61 additional skin closure staples and vessel ligation clips  

PubMed Central

Purpose Metallic skin closure staples and vessel ligation clips should be tested at 3-Tesla to characterize MRI issues in order to ensure patient safety. Therefore, metallic surgical implants were assessed at 3-Tesla for magnetic field interactions, MRI-related heating, and artifacts. Methods A skin closure staple (Visistat Skin Stapler, staple, Polytetrafluoroethylene, PTFE, coated 316L/316LVM stainless steel; Teleflex Medical, Durham, NC) and a vessel ligation clip (Hemoclip Traditional, stainless steel; Teleflex Medical, Durham, NC) that represented the largest metallic sizes made from materials with the highest magnetic susceptibilities (i.e., based on material information) among 61 other surgical implants (52 metallic implants, 9 nonmetallic implants) underwent evaluation for magnetic field interactions, MRI-related heating, and artifacts using standardized techniques. MRI-related heating was assessed by placing each implant in a gelled-saline-filled phantom with MRI performed using a transmit/receive RF body coil at an MR system reported, whole body averaged SAR of 2.9-W/kg for 15-min. Artifacts were characterized using T1-weighted, SE and GRE pulse sequences. Results Each surgical implant showed minor magnetic field interactions (20- and 27-degrees, which is acceptable from a safety consideration). Heating was not substantial (highest temperature change, ? 1.6°C). Artifacts may create issues if the area of interest is in the same area or close to the respective surgical implant. Conclusions The results demonstrated that it would be acceptable for patients with these metallic surgical implants to undergo MRI at 3-Tesla or less. Because of the materials and dimensions of the surgical implants that underwent testing, these findings pertain to 61 additional similar implants.

2012-01-01

58

Numerical evaluation of E-fields induced by body motion near high-field MRI scanner.  

PubMed

In modern magnetic resonance imaging (MRI), both patients and radiologists are exposed to strong, nonuniform static magnetic fields inside or outside of the scanner, in which the body movement may be able to induce electric currents in tissues which could be possibly harmful. This paper presents theoretical investigations into the spatial distribution of induced E-fields in the human model when moving at various positions around the magnet. The numerical calculations are based on an efficient, quasistatic, finite-difference scheme and an anatomically realistic, full-body, male model. 3D field profiles from an actively-shielded 4 T magnet system are used and the body model projected through the field profile with normalized velocity. The simulation shows that it is possible to induce E-fields/currents near the level of physiological significance under some circumstances and provides insight into the spatial characteristics of the induced fields. The results are easy to extrapolate to very high field strengths for the safety evaluation at a variety of field strengths and motion velocities. PMID:17271880

Crozier, S; Liu, F

2004-01-01

59

A 32-channel lattice transmission line array for parallel transmit and receive MRI at 7 tesla.  

PubMed

Transmit and receive RF coil arrays have proven to be particularly beneficial for ultra-high-field MR. Transmit coil arrays enable such techniques as B(1) (+) shimming to substantially improve transmit B(1) homogeneity compared to conventional volume coil designs, and receive coil arrays offer enhanced parallel imaging performance and SNR. Concentric coil arrangements hold promise for developing transceiver arrays incorporating large numbers of coil elements. At magnetic field strengths of 7 tesla and higher where the Larmor frequencies of interest can exceed 300 MHz, the coil array design must also overcome the problem of the coil conductor length approaching the RF wavelength. In this study, a novel concentric arrangement of resonance elements built from capacitively-shortened half-wavelength transmission lines is presented. This approach was utilized to construct an array with whole-brain coverage using 16 transceiver elements and 16 receive-only elements, resulting in a coil with a total of 16 transmit and 32 receive channels. PMID:20512850

Adriany, Gregor; Auerbach, Edward J; Snyder, Carl J; Gözübüyük, Ark; Moeller, Steen; Ritter, Johannes; Van de Moortele, Pierre-François; Vaughan, Tommy; U?urbil, Kâmil

2010-06-01

60

Robust Detection of Ocular Dominance Columns in Humans using Hahn Spin Echo BOLD functional MRI at 7 Tesla  

PubMed Central

Cells in the mammalian brain tend to be grouped together according to their afferent and efferent connectivity, as well as their physiological properties. The columnar structures of neocortex are prominent examples of such modular organization, and have been studied extensively in anatomical and physiological experiments in rats, cats and monkeys. The importance of noninvasive study of such structures, in particular in human subjects, cannot be overemphasized. Not surprisingly, therefore, many attempts were made to map cortical columns using functional magnetic resonance imaging (fMRI). Yet, the robustness, repeatability, and generality of the hitherto used fMRI methodologies have been a subject of intensive debate. Using differential mapping in a high magnetic field magnet (7 Tesla), we demonstrate here the ability of Hahn Spin-Echo (HSE) BOLD to map the ocular dominance columns (ODCs) of the human visual cortex reproducibly over several days with a high degree of accuracy, relative to expected spatial patterns from post-mortem data. On the other hand, the conventional Gradient-Echo (GE) blood oxygen level dependent (BOLD) signal in some cases failed to resolve ODCs uniformily across the selected gray matter region, due to the presence of non-specific signals. HSE signals uniformly resolved the ODC patterns, providing a more generalized mapping methodology (i.e. one that does not require experimental parameters or approaches to be adjusted because of potential large vessel effects) that can be – in principle – used to map unknown columnar systems in the human brain, potentially paving the way both for the study of the functional architecture of human sensory cortices, and of brain modules underlying specific cognitive processes.

Yacoub, Essa; Shmuel, Amir; Logothetis, Nikos; Ugurbil, Kamil

2007-01-01

61

BOLD fMRI signal characteristics of S1- and S2-SSFP at 7 Tesla.  

PubMed

Object: To compare the BOLD fMRI signal characteristics at in the cortex and on the pial surface for a non-balanced steady-state free precession sequence (nb-SSFP) at 7 T. Materials and Methods: A multi-echo nb-SSFP sequence was used for high resolution fMRI at 7 T. Two S1 (S(+)) echoes at different echo times were acquired together with an S2 (S(-)) echo. The primary visual cortex (V1) was examined using a reversing checkerboard paradigm at an isotropic resolution of 0.75 mm, with 35 volumes acquired and a total scan time of 27 min. Results: Significant activation was observed in all subjects for all three acquired echoes. For the S1 signal at the longer TE, the activation induced signal change was about 4% in the cortex and 10% at the cortical surface, while for S2 the corresponding values were 3 and 5%. Conclusion: For both S1 and S2 data, the BOLD signal peaks at the pial surface. The large pial surface signal change in S2 may be caused by dynamic averaging around post-capillary vessels embedded within CSF. This is made possible by the long diffusion times of the pathways contributing to the S2 signal and the relatively high diffusion coefficient of CSF. The results indicate that S2-SSFP might not be a suited alternative to spin-echo for high-resolution fMRI at 7 T. PMID:24659952

Goa, Pål E; Koopmans, Peter J; Poser, Benedikt A; Barth, Markus; Norris, David G

2014-01-01

62

Quantitative assessment of trabecular bone micro-architecture of the wrist via 7 Tesla MRI: preliminary results  

PubMed Central

Object The goal of this study was to determine the feasibility of performing quantitative 7T magnetic resonance imaging (MRI) assessment of trabecular bone micro-architecture of the wrist, a common fracture site. Materials and methods The wrists of 4 healthy subjects (1 woman, 3 men, 28±8.9 years) were scanned on a 7T whole body MR scanner using a 3D fast low-angle shot (FLASH) sequence (TR/TE = 20/4.5ms, 0.169 × 0.169 × 0.5mm). Trabecular bone was segmented and divided into 4 or 8 angular subregions. Total bone volume (TBV), bone volume fraction (BVF), surface-curve ratio (SC), and erosion index (EI) were computed. Subjects were scanned twice to assess measurement reproducibility. Results Group mean subregional values for TBV, BVF, SC, and EI (8 subregion analysis) were as follows: 8489 ± 3686, 0.27 ± 0.045, 9.61 ± 6.52; and 1.43 ± 1.25. Within each individual, there was subregional variation in TBV, SC, and EI (>5%), but not BVF (<5%). Intersubject variation (?12%) existed for all parameters. Within-subject coefficients of variation were ?10%. Conclusion This is the first study to perform quantitative 7T MRI assessment of trabecular bone micro-architecture of the wrist. This method could be utilized to study perturbations in bone structure in subjects with osteoporosis or other bone disorders.

Wang, Ligong; Liang, Guoyuan; Babb, James S.; Wiggins, Graham C.; Saha, Punam K.; Regatte, Ravinder R.

2013-01-01

63

Computational dosimetry of induced electric fields during realistic movements in the vicinity of a 3 T MRI scanner  

NASA Astrophysics Data System (ADS)

Medical staff working near magnetic resonance imaging (MRI) scanners are exposed both to the static magnetic field itself and also to electric currents that are induced in the body when the body moves in the magnetic field. However, there are currently limited data available on the induced electric field for realistic movements. This study computationally investigates the movement induced electric fields for realistic movements in the magnetic field of a 3 T MRI scanner. The path of movement near the MRI scanner is based on magnetic field measurements using a coil sensor attached to a human volunteer. Utilizing realistic models for both the motion of the head and the magnetic field of the MRI scanner, the induced fields are computationally determined using the finite-element method for five high-resolution numerical anatomical models. The results show that the time-derivative of the magnetic flux density (dB/dt) is approximately linearly proportional to the induced electric field in the head, independent of the position of the head with respect to the magnet. This supports the use of dB/dt measurements for occupational exposure assessment. For the path of movement considered herein, the spatial maximum of the induced electric field is close to the basic restriction for the peripheral nervous system and exceeds the basic restriction for the central nervous system in the international guidelines. The 99th percentile electric field is a considerably less restrictive metric for the exposure than the spatial maximum electric field; the former is typically 60-70% lower than the latter. However, the 99th percentile electric field may exceed the basic restriction for dB/dt values that can be encountered during tasks commonly performed by MRI workers. It is also shown that the movement-induced eddy currents may reach magnitudes that could electrically stimulate the vestibular system, which could play a significant role in the generation of vertigo-like sensations reported by people moving in a strong static magnetic field.

Laakso, Ilkka; Kännälä, Sami; Jokela, Kari

2013-04-01

64

Computational dosimetry of induced electric fields during realistic movements in the vicinity of a 3 T MRI scanner.  

PubMed

Medical staff working near magnetic resonance imaging (MRI) scanners are exposed both to the static magnetic field itself and also to electric currents that are induced in the body when the body moves in the magnetic field. However, there are currently limited data available on the induced electric field for realistic movements. This study computationally investigates the movement induced electric fields for realistic movements in the magnetic field of a 3 T MRI scanner. The path of movement near the MRI scanner is based on magnetic field measurements using a coil sensor attached to a human volunteer. Utilizing realistic models for both the motion of the head and the magnetic field of the MRI scanner, the induced fields are computationally determined using the finite-element method for five high-resolution numerical anatomical models. The results show that the time-derivative of the magnetic flux density (dB/dt) is approximately linearly proportional to the induced electric field in the head, independent of the position of the head with respect to the magnet. This supports the use of dB/dt measurements for occupational exposure assessment. For the path of movement considered herein, the spatial maximum of the induced electric field is close to the basic restriction for the peripheral nervous system and exceeds the basic restriction for the central nervous system in the international guidelines. The 99th percentile electric field is a considerably less restrictive metric for the exposure than the spatial maximum electric field; the former is typically 60-70% lower than the latter. However, the 99th percentile electric field may exceed the basic restriction for dB/dt values that can be encountered during tasks commonly performed by MRI workers. It is also shown that the movement-induced eddy currents may reach magnitudes that could electrically stimulate the vestibular system, which could play a significant role in the generation of vertigo-like sensations reported by people moving in a strong static magnetic field. PMID:23552657

Laakso, Ilkka; Kännälä, Sami; Jokela, Kari

2013-04-21

65

Improved assessment of cartilage repair tissue using fluid-suppressed 23Na inversion recovery MRI at 7 Tesla: preliminary results  

PubMed Central

Objectives To evaluate cartilage repair and native tissue using a three-dimensional (3D), radial, ultra-short echo time (UTE) 23Na MR sequence without and with an inversion recovery (IR) preparation pulse for fluid suppression at 7 Tesla (T). Methods This study had institutional review board approval. We recruited 11 consecutive patients (41.5±11.8 years) from an orthopaedic surgery practice who had undergone a knee cartilage restoration procedure. The subjects were examined postoperatively (median=26 weeks) with 7-T MRI using: proton-T2 (TR/TE=3,000 ms/60 ms); sodium UTE (TR/TE=100 ms/0.4 ms); fluid-suppressed, sodium UTE adiabatic IR. Cartilage sodium concentrations in repair tissue ([Na+]R), adjacent native cartilage ([Na+]N), and native cartilage within the opposite, non-surgical compartment ([Na+]N2) were calculated using external NaCl phantoms. Results For conventional sodium imaging, mean [Na+]R, [Na+]N, [Na+]N2 were 177.8±54.1 mM, 170.1±40.7 mM, 172.2±30 mM respectively. Differences in [Na+]R versus [Na+]N (P=0.59) and [Na+]N versus [Na+]N2 (P=0.89) were not significant. For sodium IR imaging, mean [Na+]R, [Na+]N, [Na+]N2 were 108.9±29.8 mM, 204.6±34.7 mM, 249.9± 44.6 mM respectively. Decreases in [Na+]R versus [Na+]N (P=0.0.0000035) and [Na+]N versus [Na+]N2 (P=0.015) were significant. Conclusions Sodium IR imaging at 7 T can suppress the signal from free sodium within synovial fluid. This may allow improved assessment of [Na+] within cartilage repair and native tissue.

Madelin, Guillaume; Sherman, Orrin H.; Strauss, Eric J.; Xia, Ding; Recht, Michael P.; Jerschow, Alexej; Regatte, Ravinder R.

2013-01-01

66

Effects of simultaneous EEG recording on MRI data quality at 1.5, 3 and 7 tesla.  

PubMed

Although the focus of attention on data degradation during simultaneous MRI/EEG recording has to date largely been upon EEG artefacts, the presence of the conducting wires and electrodes of the EEG recording system also causes some degradation of MRI data quality. This may result from magnetic susceptibility effects which lead to signal drop-out and image distortion, as well as the perturbation of the radiofrequency fields, which can cause local signal changes and a global reduction in the signal to noise ratio (SNR) of magnetic resonance images. Here, we quantify the effect of commercially available 32 and 64 electrode caps on the quality of MR images obtained in scanners operating at magnetic fields of 1.5, 3 and 7 T, via the use of MR-based, field-mapping techniques and analysis of the SNR in echo planar image time series. The electrodes are shown to be the dominant source of magnetic field inhomogeneity, although the localised nature of the field perturbation that they produce means that the effect on the signal intensity from the brain is not significant. In the particular EEG caps investigated here, RF inhomogeneity linked to the longer ECG and EOG leads causes some reduction in the signal intensity in images obtained at 3 and 7 T. Measurements of the standard deviation of white matter signal in EPI time series indicates that the introduction of the EEG cap produces a small reduction in the image signal to noise ratio, which increases with the number of electrodes used. PMID:17689767

Mullinger, Karen; Debener, Stefan; Coxon, Ronald; Bowtell, Richard

2008-03-01

67

Correction of inter-scanner and within-subject variance in structural MRI based automated diagnosing.  

PubMed

Automated analysis of structural magnetic resonance images is a promising way to improve early detection of neurodegenerative brain diseases. Clinical applications of such methods involve multiple scanners with potentially different hardware and/or acquisition sequences and demographically heterogeneous groups. To improve classification performance, we propose to correct effects of subject-specific covariates (such as age, total intracranial volume, and sex) as well as effects of scanner by using a non-linear Gaussian process model. To test the efficacy of the correction, we performed classification of carriers of the genetic mutation leading to Huntington's disease (HD) versus healthy controls. Half of the HD carriers were free of typical HD symptoms and had an estimated 5 to 20years before onset of clinical symptoms, thus providing a model for preclinical diagnosis of a neurodegenerative disease. Structural magnetic resonance brain images were acquired at four sites with pairs of sites which had the identical scanner type, equipment, and acquisition parameters. For automatic classification, we used spatially normalized probabilistic maps of gray matter, then removed confounding effects by Gaussian process regression, and then performed classification with a support vector machine. Voxel-based morphometry of gray matter maps showed disease effects that were spatially wider spread than effects of scanner, but no significant interactions between scanner and disease were found. A model trained with data from a single scanner generalized well to data from a different scanner. When confounding diagnostics groups and scanner during training, e.g. by using controls from one scanner and gene carriers from another, classification accuracy dropped significantly in many cases. By regressing out confounds with Gaussian process regression, the performance levels were comparable to those obtained in scenarios without confound. We conclude that models trained on data acquired with a single scanner generalized well to data acquired with a different same-generation scanner even when the vendor differed. When confounding grouping and scanner during training is unavoidable to gather training data, regressing out inter-scanner and between-subject variability can reduce the loss in accuracy due to the confound. PMID:24791746

Kostro, Daniel; Abdulkadir, Ahmed; Durr, Alexandra; Roos, Raymund; Leavitt, Blair R; Johnson, Hans; Cash, David; Tabrizi, Sarah J; Scahill, Rachael I; Ronneberger, Olaf; Klöppel, Stefan

2014-09-01

68

Commissioning of a new wide-bore MRI scanner for radiotherapy planning of head and neck cancer  

PubMed Central

Objective: A combination of CT and MRI is recommended for radiotherapy planning of head and neck cancers, and optimal spatial co-registration is achieved by imaging in the treatment position using the necessary immobilisation devices on both occasions, something which requires wide-bore scanners. Quality assurance experiments were carried out to commission a newly installed 1.5-T wide-bore MRI scanner and a dedicated, flexible six-channel phased array head and neck coil. Methods: Signal-to-noise ratio (SNR) and spatial signal uniformity were quantified using a homogeneous aqueous phantom, and geometric distortion was quantified using a phantom with water-filled fiducials in a grid pattern. Volunteer scans were also used to determine the in vivo image quality. Clinically relevant T1 weighted and T2 weighted fat-suppressed sequences were assessed in multiple scan planes (both sequences fast spin echo based). The performance of two online signal uniformity correction schemes, one utilising low-resolution reference scans and the other not utilising low-resolution reference scans, was compared. Results: Geometric distortions, for a ±35-kHz bandwidth, were <1?mm for locations within 10?cm of the isocentre rising to 1.8?mm at 18?cm away. SNR was above 50, and uniformity in the axial plane was 71% and 95% before and after uniformity correction, respectively. Conclusion: The combined performance of the wide-bore scanner and the dedicated coil was adjudged adequate, although superior–inferior spatial coverage was slightly limited in the lower neck. Advances in knowledge: These results will be of interest to the increasing number of oncology centres that are seeking to incorporate MRI into planning practice using dedicated equipment.

Liney, G P; Owen, S C; Beaumont, A K E; Lazar, V R; Manton, D J

2013-01-01

69

Evaluating requirements for spatial resolution of fMRI for neurosurgical planning  

Microsoft Academic Search

Abstract: The unambiguous localization of eloquent functional areas is necessary to decrease the neuro-logical morbidity of neurosurgical procedures. We explored the minimum spatial resolution requirements for functional magnetic resonance imaging (fMRI) data acquisition when brain mapping is used in neurosurgical planning and navigation. Using a 1.5 Tesla clinical MRI scanner, eight patients with brain tumors underwent fMRI scans using spatial

Seung-Schik Yoo; Ion-Florin Talos; Alexandra J. Golby; Peter Mc L. Black; Lawrence P. Panych

2004-01-01

70

The Role of Magnetic Resonance Imaging (MRI) in Prostate Cancer Imaging and Staging at 1.5 and 3 Tesla : The Beth Israel Deaconess Medical Center (BIDMC) Approach  

PubMed Central

Management decisions for patients with prostate cancer present a dilemma for both patients and their clinicians because prostate cancers demonstrate a wide range in biologic activity, with the majority of cases not leading to a prostate cancer related death. Furthermore, the current treatment options have significant side effects, such as incontinence, rectal injury and impotence. Key elements for guiding appropriate treatment include: distinction of organ-confined disease from extracapsular extension (ECE); and determination of tumor volume and tumor grade, none of which have been satisfactorily accomplished in today’s pre-treatment paradigm. Magnetic resonance imaging (MRI) has the capability to assess prostate tissue, both functionally and morphologically. MRI as a staging tool has not shown enough consistency or sufficient accuracy for widespread adoption in clinical practice; yet, recent technical developments in MRI have yielded improved results. At our institution we have combined the use of new endorectal 3 Tesla MRI technology, T2-weighted, and high spatial resolution dynamic-contrast enhanced (DCE) MRI to non-invasively assess the prostate with higher signal-to-noise ratio and spatial resolution than previously achieved. This approach allows assessment of prostate-tissue morphology and kinetics, thus providing a non-invasive tool for tumor detection and staging and, consequently, directing biopsy and treatment specifically to diseased areas for a pre-treatment evaluation that can assist in the rational selection of patients for appropriate prostate cancer therapy.

Bloch, B. Nicolas; Lenkinski, Robert. E.; Rofsky, Neil M.

2009-01-01

71

3 Tesla multiparametric MRI for GTV-definition of Dominant Intraprostatic Lesions in patients with Prostate Cancer - an interobserver variability study  

PubMed Central

Purpose To evaluate the interobserver variability of gross tumor volume (GTV) - delineation of Dominant Intraprostatic Lesions (DIPL) in patients with prostate cancer using published MRI criteria for multiparametric MRI at 3 Tesla by 6 different observers. Material and methods 90 GTV-datasets based on 15 multiparametric MRI sequences (T2w, diffusion weighted (DWI) and dynamic contrast enhanced (DCE)) of 5 patients with prostate cancer were generated for GTV-delineation of DIPL by 6 observers. The reference GTV-dataset was contoured by a radiologist with expertise in diagnostic imaging of prostate cancer using MRI. Subsequent GTV-delineation was performed by 5 radiation oncologists who received teaching of MRI-features of primary prostate cancer before starting contouring session. GTV-datasets were contoured using Oncentra Masterplan® and iplan® Net. For purposes of comparison GTV-datasets were imported to the Artiview® platform (Aquilab®), GTV-values and the similarity indices or Kappa indices (KI) were calculated with the postulation that a KI?>?0.7 indicates excellent, a KI > 0.6 to < 0.7 substantial and KI > 0.5 to < 0.6 moderate agreement. Additionally all observers rated difficulties of contouring for each MRI-sequence using a 3 point rating scale (1?=?easy to delineate, 2?=?minor difficulties, 3?=?major difficulties). Results GTV contouring using T2w (KI-T2w?=?0.61) and DCE images (KI-DCE?=?0.63) resulted in substantial agreement. GTV contouring using DWI images resulted in moderate agreement (KI-DWI?=?0.51). KI-T2w and KI-DCE was significantly higher than KI-DWI (p?=?0.01 and p?=?0.003). Degree of difficulty in contouring GTV was significantly lower using T2w and DCE compared to DWI-sequences (both p?Tesla for GTV-definition of DIPL in prostate cancer patients by radiation oncologists with knowledge of MRI features results in substantial agreement compared to an experienced MRI-radiologist, but for radiotherapy purposes higher KI are desirable, strengthen the need for expert surveillance. DWI sequence for GTV delineation was considered as difficult in application.

2013-01-01

72

MRI Acquisition ACRING-6677  

Cancer.gov

MRI Technical Acquisition (ACRIN-6677 Protocol) Required Hardware/Software: Most modern 1.5 Tesla or 3.0 Tesla MRI systems can adequately perform the required examinations. Under certain circumstances, older systems can also perform well, while on

73

HR 3 Tesla MRI for the diagnosis of endolymphatic hydrops and differential diagnosis of inner ear tumors--demonstrated by two cases with similar symptoms.  

PubMed

The synchronous appearance of different inner ear pathologies with a nearly equivalent clinical manifestation such as Menière's disease and vestibular schwannoma is very rare but leads to a relevant dilemma concerning therapy options. MRI is the method of choice to detect intralabyrinthine tumors. Since endolymphatic hydrops is considered the morphological equivalent of Menière's disease, magnetic resonance imaging including hT2w-FLAIR sequences 4?h after i.?v. administration of gadolinium-based contrast agents (GBCA) allows the diagnosis and grading of endolymphatic hydrops in vivo synchronous to diagnosis and monitoring of ILT. To this day, only a few cases of intralabyrinthine schwannoma could be shown to appear simultaneously with endolymphatic hydrops by MRI, but to our knowledge the dedicated distinction of endolymphatic space has not been previously demonstrated. The aim of this work was not only to detect the coincidence of endolymphatic hydrops and vestibular schwannoma, but also to differentiate tumor tissue from endolymphatic space by 3 Tesla MRI. This enables therapy options that are originally indicated for Menière's disease. The aim of this work was to describe the feasibility and usefulness of endolymphatic hydrops MRI on intralabyrinthal tumors in a special case of intravestibular schwannoma to demonstrate the high clinical relevance and impact in therapeutic decision-making for the synchronous appearance of endolymphatic hydrops and intralabyrinthine tumors. Therefore, we present a typical case of Menière's disease in contrast to a patient with an intralabyrinthine schwannoma and Menière-like symptoms. PMID:24452492

Homann, G; Fahrendorf, D; Niederstadt, T; Nagelmann, N; Heindel, W; Lütkenhöner, B; Böckenfeld, Y; Basel, T; Vieth, V

2014-03-01

74

A novel active MR probe using a miniaturized optical link for a 1.5-T MRI scanner.  

PubMed

Applying an active intravascular MR catheter device that allows signal transmission from the catheter tip requires special means to avoid radiofrequency-induced heating. This article presents a novel, miniaturized all-optical active MR probe to use with real-time MRI in minimally invasive interventions for catheter guidance and intravascular imaging. An optical link transmits the received MR signals from the catheter tip to the MR receiver with inherently radiofrequency-safe optical fibers. Furthermore, power is supplied optically to the transmitter as well. The complete integration into a small tube of 6-Fr (2-mm diameter) size with a 7-Fr (2.33-mm diameter) rigid tubing was realized using chip components for the optical modulator and a novel miniaturized optical bench fabricated from silicon substrates with 3D self-aligning structures for fiber integration. In MRI phantom measurements, projection-based tip tracking and high-resolution imaging were successfully performed with the optical link inside a 1.5-T MRI scanner. Images were obtained in a homogeneous phantom liquid, and first pictures were acquired from inside a kiwi that demonstrates the potential of the MR-safe optical link. The signal-to-noise ratio has significantly improved compared with former systems, and it is demonstrated that the novel optical link exhibits a signal-to-noise ratio comparable to a direct electrical link. PMID:21837807

Fandrey, Stephan; Weiss, Steffen; Müller, Jörg

2012-01-01

75

Initial experience with MR-imaging of intracranial midline-lesions and lesions of the cervical spine at half tesla  

Microsoft Academic Search

Summary Fifty-two patients were examined both with computed tomography using a different third generation scanner and by magnetic resonance imaging (MRI) at half Tesla field strength (Philips Gyroscan 5 S). Excellent contrast and spatial resolution as well as initial comparative results of normal anatomy and also selected clinical cases were demonstrated with the spin-echo (SE) and\\/or inversion recovery (IR) technique.

Rainer Guido Bluemm; Danièle Balériaux; Gerhard Lausberg; Jacques Brotchi

1984-01-01

76

A Two-dimensional Sixteen Channel Transmit/Receive Coil Array for Cardiac MRI at 7.0 Tesla: Design, Evaluation and Application  

PubMed Central

Purpose To design, evaluate and apply a two-dimensional 16 channel transmit/receive coil array tailored for cardiac MRI at 7.0 Tesla. Material and Methods The cardiac coil array consists of 2 sections each using 8 elements arranged in a 2 × 4 array. RF safety was validated by SAR simulations. Cardiac imaging was performed using 2D CINE FLASH imaging, T2* mapping and fat-water separation imaging. The characteristics of the coil array were analyzed including parallel imaging performance, left ventricular chamber quantification and overall image quality. Results RF characteristics were found to be appropriate for all subjects included in the study. The SAR values derived from the simulations fall well in the limits of legal guidelines. The baseline SNR advantage at 7.0 T was put to use to acquire 2D CINE images of the heart with a very high spatial resolution of (1 × 1 × 4) mm3. The proposed coil array supports 1D acceleration factors of up to R=4 without impairing image quality significantly. Conclusions The 16 channel TX/RX coil has the capability to acquire high contrast and high spatial resolution images of the heart at 7.0 Tesla.

Thalhammer, Christof; Renz, Wolfgang; Winter, Lukas; Hezel, Fabian; Rieger, Jan; Pfeiffer, Harald; Graessl, Andreas; Seifert, Frank; Hoffmann, Werner; von Knobelsdorff-Brenkenhoff, Florian; Tkachenko, Valeriy; Schulz-Menger, Jeanette; Kellman, Peter; Niendorf, Thoralf

2012-01-01

77

A fast multiparameter MRI approach for acute stroke assessment on a 3T clinical scanner: preliminary results in a non-human primate model with transient ischemic occlusion  

PubMed Central

Many MRI parameters have been explored and demonstrated the capability or potential to evaluate acute stroke injury, providing anatomical, microstructural, functional, or neurochemical information for diagnostic purposes and therapeutic development. However, the application of multiparameter MRI approach is hindered in clinic due to the very limited time window after stroke insult. Parallel imaging technique can accelerate MRI data acquisition dramatically and has been incorporated in modern clinical scanners and increasingly applied for various diagnostic purposes. In the present study, a fast multiparameter MRI approach including structural T1-weighted imaging (T1W), T2-weighted imaging (T2W), diffusion tensor imaging (DTI), T2-mapping, proton magnetic resonance spectroscopy, cerebral blood flow (CBF), and magnetization transfer (MT) imaging, was implemented and optimized for assessing acute stroke injury on a 3T clinical scanner. A macaque model of transient ischemic stroke induced by a minimal interventional approach was utilized for evaluating the multiparameter MRI approach. The preliminary results indicate the surgical procedure successfully induced ischemic occlusion in the cortex and/or subcortex in adult macaque monkeys (n=4). Application of parallel imaging technique substantially reduced the scanning duration of most MRI data acquisitions, allowing for fast and repeated evaluation of acute stroke injury. Hence, the use of the multiparameter MRI approach with up to five quantitative measures can provide significant advantages in preclinical or clinical studies of stroke disease.

Tong, Frank; Li, Chun-Xia; Yan, Yumei; Nair, Govind; Nagaoka, Tsukasa; Tanaka, Yoji; Zola, Stuart; Howell, Leonard

2014-01-01

78

A fast multiparameter MRI approach for acute stroke assessment on a 3T clinical scanner: preliminary results in a non-human primate model with transient ischemic occlusion.  

PubMed

Many MRI parameters have been explored and demonstrated the capability or potential to evaluate acute stroke injury, providing anatomical, microstructural, functional, or neurochemical information for diagnostic purposes and therapeutic development. However, the application of multiparameter MRI approach is hindered in clinic due to the very limited time window after stroke insult. Parallel imaging technique can accelerate MRI data acquisition dramatically and has been incorporated in modern clinical scanners and increasingly applied for various diagnostic purposes. In the present study, a fast multiparameter MRI approach including structural T1-weighted imaging (T1W), T2-weighted imaging (T2W), diffusion tensor imaging (DTI), T2-mapping, proton magnetic resonance spectroscopy, cerebral blood flow (CBF), and magnetization transfer (MT) imaging, was implemented and optimized for assessing acute stroke injury on a 3T clinical scanner. A macaque model of transient ischemic stroke induced by a minimal interventional approach was utilized for evaluating the multiparameter MRI approach. The preliminary results indicate the surgical procedure successfully induced ischemic occlusion in the cortex and/or subcortex in adult macaque monkeys (n=4). Application of parallel imaging technique substantially reduced the scanning duration of most MRI data acquisitions, allowing for fast and repeated evaluation of acute stroke injury. Hence, the use of the multiparameter MRI approach with up to five quantitative measures can provide significant advantages in preclinical or clinical studies of stroke disease. PMID:24834423

Zhang, Xiaodong; Tong, Frank; Li, Chun-Xia; Yan, Yumei; Nair, Govind; Nagaoka, Tsukasa; Tanaka, Yoji; Zola, Stuart; Howell, Leonard

2014-04-01

79

New shielding configurations for a simultaneous PET/MRI scanner at 7T.  

PubMed

Understanding sources of electromagnetic interference are important in designing any electronic system. This is especially true when combining positron emission tomography (PET) and magnetic resonance imaging (MRI) in a multimodality system as coupling between the subsystems can degrade the performance of either modality. For this reason, eliminating radio frequency (RF) interference and gradient-induced eddy currents have been major challenges in building simultaneous hybrid PET/MRI systems. MRI requires negligible RF interference at the Larmor resonance frequency, while RF interference at almost any frequency may corrupt PET data. Moreover, any scheme that minimizes these interactions would, ideally, not compromise the performance of either subsystem. This paper lays out a plan to resolve these problems. A carbon fiber composite material is found to be a good RF shield at the Larmor frequency (300MHz in this work) while introducing negligible gradient eddy currents. This carbon fiber composite also provides excellent structural support for the PET detector components. Low frequency electromagnetic radiation (81kHz here) from the switching power supplies of the gradient amplifiers was also found to interfere with the PET detector. Placing the PET detector module between two carbon fiber tubes and grounding the inner carbon fiber tube to the PET detector module ground reduced this interference. Further reductions were achieved by adding thin copper (Cu) foil on the outer carbon fiber case and electrically grounding the PET detector module so that all 3 components had a common ground, i.e. with the PET detector in an electrostatic cage. Finally, gradient switching typical in MRI sequences can result in count losses in the particular PET detector design studied. Moreover, the magnitude of this effect depends on the location of the detector within the magnet bore and which MRI gradient is being switched. These findings have a bearing on future designs of PET/MRI systems. PMID:24380812

Peng, Bo J; Wu, Yibao; Cherry, Simon R; Walton, Jeffrey H

2014-02-01

80

In vivo imaging of pancreatic tumours and liver metastases using 7 Tesla MRI in a murine orthotopic pancreatic cancer model and a liver metastases model  

PubMed Central

Background Pancreatic cancer is the fourth leading cause of tumour death in the western world. However, appropriate tumour models are scarce. Here we present a syngeneic murine pancreatic cancer model using 7 Tesla MRI and evaluate its clinical relevance and applicability. Methods 6606PDA murine pancreatic cancer cells were orthotopically injected into the pancreatic head. Liver metastases were induced through splenic injection. Animals were analyzed by MRI three and five weeks following injection. Tumours were detected using T2-weighted high resolution sequences. Tumour volumes were determined by callipers and MRI. Liver metastases were analyzed using gadolinium-EOB-DTPA and T1-weighted 3D-Flash sequences. Tumour blood flow was measured using low molecular gadobutrol and high molecular gadolinium-DTPA. Results MRI handling and applicability was similar to human systems, resolution as low as 0.1 mm. After 5 weeks tumour volumes differed significantly (p < 0.01) when comparing calliper measurments (n = 5, mean 1065 mm3+/-243 mm3) with MRI (mean 918 mm3+/-193 mm3) with MRI being more precise. Histology (n = 5) confirmed MRI tumour measurements (mean size MRI 38.5 mm2+/-22.8 mm2 versus 32.6 mm2+/-22.6 mm2 (histology), p < 0,0004) with differences due to fixation and processing of specimens. After splenic injection all mice developed liver metastases with a mean of 8 metastases and a mean volume of 173.8 mm3+/-56.7 mm3 after 5 weeks. Lymphnodes were also easily identified. Tumour accumulation of gadobutrol was significantly (p < 0.05) higher than gadolinium-DTPA. All imaging experiments could be done repeatedly to comply with the 3R-principle thus reducing the number of experimental animals. Conclusions This model permits monitoring of tumour growth and metastasis formation in longitudinal non-invasive high-resolution MR studies including using contrast agents comparable to human pancreatic cancer. This multidisciplinary environment enables radiologists, surgeons and physicians to further improve translational research and therapies of pancreatic cancer.

2011-01-01

81

Safety Implications of High-Field MRI: Actuation of Endogenous Magnetic Iron Oxides in the Human Body  

Microsoft Academic Search

BackgroundMagnetic Resonance Imaging scanners have become ubiquitous in hospitals and high-field systems (greater than 3 Tesla) are becoming increasingly common. In light of recent European Union moves to limit high-field exposure for those working with MRI scanners, we have evaluated the potential for detrimental cellular effects via nanomagnetic actuation of endogenous iron oxides in the body.MethodologyTheoretical models and experimental data

Jon Dobson; Richard Bowtell; Ana Garcia-Prieto; Quentin Pankhurst; Igor Sokolov

2009-01-01

82

Data-driven optimization and evaluation of 2D EPI and 3D PRESTO for BOLD fMRI at 7 Tesla: I. Focal coverage  

PubMed Central

Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) is commonly performed using 2D single-shot echo-planar imaging (EPI). However, single-shot EPI at 7 Tesla (T) often suffers from significant geometric distortions (due to low bandwidth (BW) in the phase-encode (PE) direction) and amplified physiological noise. Recent studies have suggested that 3D multi-shot sequences such as PRESTO may offer comparable BOLD contrast-to-noise ratio with increased volume coverage and decreased geometric distortions. Thus, a four-way group-level comparison was performed between 2D and 3D acquisition sequences at two in-plane resolutions. The quality of fMRI data was evaluated via metrics of prediction and reproducibility using NPAIRS (Non-parametric Prediction, Activation, Influence and Reproducibility re-Sampling). Group activation maps were optimized for each acquisition strategy by selecting the number of principal components that jointly maximized prediction and reproducibility, and showed good agreement in sensitivity and specificity for positive BOLD changes. High-resolution EPI exhibited the highest z-scores of the four acquisition sequences; however, it suffered from the lowest BW in the PE direction (resulting in the worst geometric distortions) and limited spatial coverage, and also caused some subject discomfort through peripheral nerve stimulation (PNS). In comparison, PRESTO also had high z-scores (higher than EPI for a matched in-plane resolution), the highest BW in the PE direction (producing images with superior geometric fidelity), the potential for whole-brain coverage, and no reported PNS. This study provides evidence to support the use of 3D multi-shot acquisition sequences in lieu of single-shot EPI for ultra high field BOLD fMRI at 7T.

Barry, Robert L.; Strother, Stephen C.; Gatenby, J. Christopher; Gore, John C.

2011-01-01

83

Prediction of Prostate Cancer Extracapsular Extension with High Spatial Resolution Dynamic Contrast-Enhanced 3 Tesla MRI  

PubMed Central

Objectives To assess the value of dynamic contrast-enhanced (DCE) combined with T2-weighted (T2W) endorectal coil (ERC) magnetic resonance imaging (MRI) at 3 T (3T) for determining extracapsular extension (ECE) of prostate cancer. Methods In this IRB-approved study, ERC 3T MRI of the prostate was performed in 108 patients prior to radical prostatectomy. T2W fast spin-echo and DCE 3D gradient echo images were acquired. The interpretations of readers with varied experience were analyzed. MRI-based staging results were compared with radical prostatectomy histology. Descriptive statistics were generated for prediction of ECE and staging accuracies were determined by the area under the receiver-operating-characteristic curve. Results The overall sensitivity, specificity, positive predictive value, and negative predictive value for ECE were 75%, 92%, 79% and 91%, respectively. Diagnostic accuracy for staging was 86%, 80% and 91% for all readers, experienced and less experienced readers, respectively. Conclusions ERC 3T MRI of the prostate combining DCE and T2W imaging is an accurate pretheurapeutic staging tool for assessment of ECE in clinical practice across varying levels of reader experience.

Bloch, B. Nicolas; Genega, Elizabeth M.; Costa, Daniel N.; Pedrosa, Ivan; Smith, Martin P.; Kressel, Herbert Y.; Ngo, Long; Sanda, Martin G.; DeWolf, William C.; Rofsky, Neil M.

2013-01-01

84

Sustained Reperfusion after Blockade of Glycoprotein-Receptor-Ib in Focal Cerebral Ischemia: An MRI Study at 17.6 Tesla  

PubMed Central

Background Inhibition of early platelet adhesion by blockade of glycoprotein-IB (GPIb) protects mice from ischemic stroke. To elucidate underlying mechanisms in-vivo, infarct development was followed by ultra-high field MRI at 17.6 Tesla. Methods Cerebral infarction was induced by transient-middle-cerebral-artery-occlusion (tMCAO) for 1 hour in C57/BL6 control mice (N?=?10) and mice treated with 100 µg Fab-fragments of the GPIb blocking antibody p0p/B 1 h after tMCAO (N?=?10). To control for the effect of reperfusion, additional mice underwent permanent occlusion and received anti-GPIb treatment (N?=?6; pMCAO) or remained without treatment (N?=?3; pMCAO). MRI 2 h and 24 h after MCAO measured cerebral-blood-flow (CBF) by continuous arterial-spin labelling, the apparent-diffusion-coefficient (ADC), quantitative-T2 and T2-weighted imaging. All images were registered to a standard mouse brain MRI atlas and statistically analysed voxel-wise, and by cortico-subcortical ROI analysis. Results Anti-GPIb treatment led to a relative increase of postischemic CBF vs. controls in the cortical territory of the MCA (2 h: 44.2±6.9 ml/100 g/min versus 24 h: 60.5±8.4; p?=?0.0012, F(1,18)?=?14.63) after tMCAO. Subcortical CBF 2 h after tMCAO was higher in anti-GPIb treated animals (45.3±5.9 vs. controls: 33.6±4.3; p?=?0.04). In both regions, CBF findings were clearly related to a lower probability of infarction (Cortex/Subcortex of treated group: 35%/65% vs. controls: 95%/100%) and improved quantitative-T2 and ADC. After pMCAO, anti-GPIb treated mice developed similar infarcts preceded by severe irreversible hypoperfusion as controls after tMCAO indicating dependency of stroke protection on reperfusion. Conclusion Blockade of platelet adhesion by anti-GPIb-Fab-fragments results in substantially improved CBF early during reperfusion. This finding was in exact spatial correspondence with the prevention of cerebral infarction and indicates in-vivo an increased patency of the microcirculation. Thus, progression of infarction during early ischemia and reperfusion can be mitigated by anti-platelet treatment.

Kraft, Peter; Bartsch, Andreas J.; Jakob, Peter; Nieswandt, Bernhard; Bendszus, Martin; Stoll, Guido

2011-01-01

85

The pattern of exposure to static magnetic field of nurses involved in activities related to contrast administration into patients diagnosed in 1.5 T MRI scanners.  

PubMed

Static magnetic fields (SMFs) and time-varying electromagnetic fields exposure is necessary to obtain the diagnostic information regarding the structure of patient's tissues, by the use of magnetic resonance imaging (MRI) scanners. A diagnostic procedure may also include the administration of pharmaceuticals called contrast, which are to be applied to a patient during the examination. The nurses involved in administering contrast into a patient during the pause in examination are approaching permanently active magnets of MRI scanners and are exposed to SMF. There were performed measurements of spatial distribution of SMF in the vicinity of MRI magnets and parameters of personal exposure of nurses (i.e. individual exposimetric profiles of variability in time of SMF affecting the nurse who is performing tasks in the vicinity of magnet, characterized by statistical parameters of recorded magnetic flux density affecting the nurse). The SMF exposure in the vicinity of various MRI magnets depends on both magnetic flux density of the main field B 0 (applicable to a patient) and the construction of the scanner, but the most important factor determining the workers' exposure is the work practice. In the course of a patient's routine examination in scanners of B? = 1.5 T, the nurses are present over ?0.4-2.9 min in SMF exceeding 0.03% of B? (i.e. 0.5 mT), but only sometimes they are present in SMF exceeding 5% of B 0 (i.e. 75 mT). When patients need more attention because of their health status/condition, the nurses' exposure may be significantly longer--it may even exceed 10 min and 30% of B 0 (i.e. 500 mT). We have found that the level of exposure of nurses to SMF may vary from < 5% of the main field (a median value: 0.5-1.5%; inter-quartile range: 0.04-8.8%; max value: 1.3-12% of B?) when a patient is moved from the magnets bore before contrast administration, up to the main field level (B?) when a patient stays in the magnets bore and nurse is crawling into the bore. PMID:23675621

Karpowicz, Jolanta; Gryz, Krzysztof

2013-06-01

86

Image distortion and artifacts caused by the use of a titanium aneurism clip in 1.5 tesla- and 3 tesla-magnetic resonance imaging: effect on (60)cobalt stereotactic radiosurgery treatment planning.  

PubMed

In gamma knife stereotactic radiosurgery (GKSRS) treatment planning, 1.5 tesla (T)-magnetic resonance imaging (MRI) is normally used to identify the target lesion. Image artifacts and distortion arise in MRI if a titanium clip is surgically implanted in the brain to treat cerebral aneurysm. 3-T MRI scanners, which are increasingly being adopted, provide imaging of anatomic structures with better clinical usefulness than 1.5-T MRI machines. We investigated signal defects and image distortions both close to and more distant from the titanium clip in 1.5-T and 3-T MRI. Two kinds of phantoms were scanned using 1.5-T and 3-T MRI. Acquisitions with and without the clip were performed under the same scan parameters. No difference was observed between 1.5 T and 3 T in local decrease of signal intensity; however, image distortion was observed at 20 mm from the clip in 3 T. Over the whole region, the distortions caused by the clip were less than 0.3 mm and 1.6 mm under 1.5-T and 3-T MRI, respectively. The geometric accuracy of 1.5-T MRI was better than 3-T MRI and thus better for GKSRS treatment planning. 3-T MRI, however, appears less suitable for use in treatment planning. PMID:24953318

Nakazawa, Hisato; Yamamuro, Osamu; Uchiyama, Yukio; Komori, Masataka

2014-06-01

87

High-field 4.23 tesla magnetic resonance imaging: initial experience in turbo-inversion recovery imaging and fMRI physics  

Microsoft Academic Search

High-field magnetic resonance imaging (MRI) offers functional, biochemical and physiological information. High field is advantageous for both fMRI signal generated from deoxyhemoglobin and blood oxygen, and intracellular sodium by inversion recovery MRI imaging. High field MRI was used to image human and primates for sodium MRI imaging.

Rakesh Sharma

2004-01-01

88

Functional diffusion tensor imaging at 3 Tesla  

PubMed Central

In a previous study we reported on a non-invasive functional diffusion tensor imaging (fDTI) method to measure neuronal signals directly from subtle changes in fractional anisotropy along white matter tracts. We hypothesized that these fractional anisotropy changes relate to morphological changes of glial cells induced by axonal activity. In the present study we set out to replicate the results of the previous study with an improved fDTI scan acquisition scheme. A group of twelve healthy human participants were scanned on a 3 Tesla MRI scanner. Activation was revealed in the contralateral thalamo-cortical tract and optic radiations during tactile and visual stimulation, respectively. Mean percent signal change in FA was 3.47% for the tactile task and 3.79% for the visual task, while for the MD the mean percent signal change was only -0.10 and -0.09%. The results support the notion of different response functions for tactile and visual stimuli. With this study we successfully replicated our previous findings using the same types of stimuli but on a different group of healthy participants and at different field-strength. The successful replication of our first fDTI results suggests that the non-invasive fDTI method is robust enough to study the functional neural networks in the human brain within a practically feasible time period.

Mandl, Rene C. W.; Schnack, Hugo G.; Zwiers, Marcel P.; Kahn, Rene S.; Hulshoff Pol, Hilleke E.

2013-01-01

89

Association between in-scanner head motion with cerebral white matter microstructure: a multiband diffusion-weighted MRI study  

PubMed Central

Diffusion-weighted Magnetic Resonance Imaging (DW-MRI) has emerged as the most popular neuroimaging technique used to depict the biological microstructural properties of human brain white matter. However, like other MRI techniques, traditional DW-MRI data remains subject to head motion artifacts during scanning. For example, previous studies have indicated that, with traditional DW-MRI data, head motion artifacts significantly affect the evaluation of diffusion metrics. Actually, DW-MRI data scanned with higher sampling rate are important for accurately evaluating diffusion metrics because it allows for full-brain coverage through the acquisition of multiple slices simultaneously and more gradient directions. Here, we employed a publicly available multiband DW-MRI dataset to investigate the association between motion and diffusion metrics with the standard pipeline, tract-based spatial statistics (TBSS). The diffusion metrics used in this study included not only the commonly used metrics (i.e., FA and MD) in DW-MRI studies, but also newly proposed inter-voxel metric, local diffusion homogeneity (LDH). We found that the motion effects in FA and MD seems to be mitigated to some extent, but the effect on MD still exists. Furthermore, the effect in LDH is much more pronounced. These results indicate that researchers shall be cautious when conducting data analysis and interpretation. Finally, the motion-diffusion association is discussed.

2014-01-01

90

PLACD-7T Study: Atherosclerotic Carotid Plaque Components Correlated with Cerebral Damage at 7 Tesla Magnetic Resonance Imaging  

PubMed Central

Introduction: In patients with carotid artery stenosis histological plaque composition is associated with plaque stability and with presenting symptomatology. Preferentially, plaque vulnerability should be taken into account in pre-operative work-up of patients with severe carotid artery stenosis. However, currently no appropriate and conclusive (non-) invasive technique to differentiate between the high and low risk carotid artery plaque in vivo is available. We propose that 7 Tesla human high resolution MRI scanning will visualize carotid plaque characteristics more precisely and will enable correlation of these specific components with cerebral damage. Study objective: The aim of the PlaCD-7T study is 1: to correlate 7T imaging with carotid plaque histology (gold standard); and 2: to correlate plaque characteristics with cerebral damage ((clinically silent) cerebral (micro) infarcts or bleeds) on 7 Tesla high resolution (HR) MRI. Design: We propose a single center prospective study for either symptomatic or asymptomatic patients with haemodynamic significant (70%) stenosis of at least one of the carotid arteries. The Athero-Express (AE) biobank histological analysis will be derived according to standard protocol. Patients included in the AE and our prospective study will undergo a pre-operative 7 Tesla HR-MRI scan of both the head and neck area. Discussion: We hypothesize that the 7 Tesla MRI scanner will allow early identification of high risk carotid plaques being associated with micro infarcted cerebral areas, and will thus be able to identify patients with a high risk of periprocedural stroke, by identification of surrogate measures of increased cardiovascular risk.

den Hartog, A.G; Bovens, S.M; Koning, W; Hendrikse, J; Pasterkamp, G; Moll, F.L; de Borst, G.J

2011-01-01

91

An Approach for Preoperative Planning and Performance of MR-guided Interventions Demonstrated With a Manual Manipulator in a 1.5T MRI Scanner  

SciTech Connect

Purpose: The aim of this work was to develop and test a general methodology for the planning and performance of robot-assisted, MR-guided interventions. This methodology also includes the employment of software tools with appropriately tailored routines to effectively exploit the capabilities of MRI and address the relevant spatial limitations. Methods: The described methodology consists of: (1) patient-customized feasibility study that focuses on the geometric limitations imposed by the gantry, the robotic hardware, and interventional tools, as well as the patient; (2) stereotactic preoperative planning for initial positioning of the manipulator and alignment of its end-effector with a selected target; and (3) real-time, intraoperative tool tracking and monitoring of the actual intervention execution. Testing was performed inside a standard 1.5T MRI scanner in which the MR-compatible manipulator is deployed to provide the required access. Results: A volunteer imaging study demonstrates the application of the feasibility stage. A phantom study on needle targeting is also presented, demonstrating the applicability and effectiveness of the proposed preoperative and intraoperative stages of the methodology. For this purpose, a manually actuated, MR-compatible robotic manipulation system was used to accurately acquire a prescribed target through alternative approaching paths. Conclusions: The methodology presented and experimentally examined allows the effective performance of MR-guided interventions. It is suitable for, but not restricted to, needle-targeting applications assisted by a robotic manipulation system, which can be deployed inside a cylindrical scanner to provide the required access to the patient facilitating real-time guidance and monitoring.

Seimenis, Ioannis [Medical Diagnostic Center 'Ayios Therissos' (Cyprus); Tsekos, Nikolaos V. [University of Huston, Medical Robotics Lab, Department of Computer Science (United States); Keroglou, Christoforos [University of Cyprus, Department of Electrical and Computer Engineering (Cyprus); Eracleous, Eleni [Medical Diagnostic Center 'Ayios Therissos' (Cyprus); Pitris, Constantinos [University of Cyprus, Department of Electrical and Computer Engineering (Cyprus); Christoforou, Eftychios G., E-mail: e.christoforou@ucy.ac.cy [University of Cyprus, KIOS Research Center (Cyprus)

2012-04-15

92

Towards undistorted and noise-free speech in an MRI scanner: correlation subtraction followed by spectral noise gating.  

PubMed

Noise cancellation in an MRI environment is difficult due to the high noise levels that are in the spectral range of human speech. This paper describes a two-step method to cancel MRI noise that combines operations in both the time domain (correlation subtraction) and the frequency domain (spectral noise gating). The resulting filtered recording has a noise power suppression of over 100?dB, a significant improvement over previously described techniques on MRI noise cancellation. The distortion is lower and the noise suppression higher than using spectral noise gating in isolation. Implementation of this method will aid in detailed studies of speech in relation to vocal tract and velopharyngeal function. PMID:24606243

Inouye, Joshua M; Blemker, Silvia S; Inouye, David I

2014-03-01

93

Detection of cortical thickness correlates of cognitive performance: Reliability across MRI scan sessions, scanners, and field strengths  

Microsoft Academic Search

In normal humans, relationships between cognitive test performance and cortical structure have received little study, in part, because of the paucity of tools for measuring cortical structure. Computational morphometric methods have recently been developed that enable the measurement of cortical thickness from MRI data, but little data exist on their reliability. We undertook this study to evaluate the reliability of

B. C. Dickerson; E. Fenstermacher; D. H. Salat; D. A. Wolk; R. P. Maguire; R. Desikan; J. Pacheco; B. T. Quinn; A. Van der Kouwe; D. N. Greve; D. Blacker; M. S. Albert; R. J. Killiany; B. Fischl

2008-01-01

94

Probabilistic atlas-based segmentation of combined T1-weighted and DUTE MRI for calculation of head attenuation maps in integrated PET/MRI scanners.  

PubMed

We present a new MRI-based attenuation correction (AC) approach for integrated PET/MRI systems that combines both segmentation- and atlas-based methods by incorporating dual-echo ultra-short echo-time (DUTE) and T1-weighted (T1w) MRI data and a probabilistic atlas. Segmented atlases were constructed from CT training data using a leave-one-out framework and combined with T1w, DUTE, and CT data to train a classifier that computes the probability of air/soft tissue/bone at each voxel. This classifier was applied to segment the MRI of the subject of interest and attenuation maps (?-maps) were generated by assigning specific linear attenuation coefficients (LACs) to each tissue class. The ?-maps generated with this "Atlas-T1w-DUTE" approach were compared to those obtained from DUTE data using a previously proposed method. For validation of the segmentation results, segmented CT ?-maps were considered to the "silver standard"; the segmentation accuracy was assessed qualitatively and quantitatively through calculation of the Dice similarity coefficient (DSC). Relative change (RC) maps between the CT and MRI-based attenuation corrected PET volumes were also calculated for a global voxel-wise assessment of the reconstruction results. The ?-maps obtained using the Atlas-T1w-DUTE classifier agreed well with those derived from CT; the mean DSCs for the Atlas-T1w-DUTE-based ?-maps across all subjects were higher than those for DUTE-based ?-maps; the atlas-based ?-maps also showed a lower percentage of misclassified voxels across all subjects. RC maps from the atlas-based technique also demonstrated improvement in the PET data compared to the DUTE method, both globally as well as regionally. PMID:24753982

Poynton, Clare B; Chen, Kevin T; Chonde, Daniel B; Izquierdo-Garcia, David; Gollub, Randy L; Gerstner, Elizabeth R; Batchelor, Tracy T; Catana, Ciprian

2014-01-01

95

Probabilistic atlas-based segmentation of combined T1-weighted and DUTE MRI for calculation of head attenuation maps in integrated PET/MRI scanners  

PubMed Central

We present a new MRI-based attenuation correction (AC) approach for integrated PET/MRI systems that combines both segmentation- and atlas-based methods by incorporating dual-echo ultra-short echo-time (DUTE) and T1-weighted (T1w) MRI data and a probabilistic atlas. Segmented atlases were constructed from CT training data using a leave-one-out framework and combined with T1w, DUTE, and CT data to train a classifier that computes the probability of air/soft tissue/bone at each voxel. This classifier was applied to segment the MRI of the subject of interest and attenuation maps (?-maps) were generated by assigning specific linear attenuation coefficients (LACs) to each tissue class. The ?-maps generated with this “Atlas-T1w-DUTE” approach were compared to those obtained from DUTE data using a previously proposed method. For validation of the segmentation results, segmented CT ?-maps were considered to the “silver standard”; the segmentation accuracy was assessed qualitatively and quantitatively through calculation of the Dice similarity coefficient (DSC). Relative change (RC) maps between the CT and MRI-based attenuation corrected PET volumes were also calculated for a global voxel-wise assessment of the reconstruction results. The ?-maps obtained using the Atlas-T1w-DUTE classifier agreed well with those derived from CT; the mean DSCs for the Atlas-T1w-DUTE-based ?-maps across all subjects were higher than those for DUTE-based ?-maps; the atlas-based ?-maps also showed a lower percentage of misclassified voxels across all subjects. RC maps from the atlas-based technique also demonstrated improvement in the PET data compared to the DUTE method, both globally as well as regionally.

Poynton, Clare B; Chen, Kevin T; Chonde, Daniel B; Izquierdo-Garcia, David; Gollub, Randy L; Gerstner, Elizabeth R; Batchelor, Tracy T; Catana, Ciprian

2014-01-01

96

Prostate Cancer Detection Using High-Spatial Resolution MRI at 7.0 Tesla: Correlation with Histopathologic Findings at Radical Prostatectomy.  

National Technical Information Service (NTIS)

This study aims to develop high spatial-resolution prostate MRI at 7.0T. During this first phase of our study, we aimed to perform technical development and optimization of the necessary hardware and software to be able to perform 7.0T prostate MRI in a c...

A. B. Rosenkrantz

2012-01-01

97

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 Central

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.

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

2013-01-01

98

Magnetic resonance microimaging of human skin vasculature in vivo at 3 Tesla.  

PubMed

MRI can be used to investigate human skin microvasculature in vivo, provided adequate spatial resolution. Therefore, the sensitivity of the experiment has to be optimized to achieve sufficient signal-to-noise ratio (SNR) within reasonable measurement time to minimize motion artifacts, improve patient comfort and save costs. In this work, the high sensitivity of a 15 mm surface coil and the signal strength of a 3 Tesla scanner, together with a three-dimensional gradient echo sequence and post-processing have been combined to obtain high SNR. Images of human skin with isotropic spatial resolution of 100 ?m were acquired within 10 min and the cutaneous vasculature could be visualized in 3D [Correction made here after initial online publication.], based on three averaged scans. The presented method can be used for diagnosis and, due to its non-invasiveness, treatment monitoring of vascular pathologies in the skin, such as inflammation, vascular malformation, or neoangiogenesis in superficial tumors. PMID:21254205

Laistler, Elmar; Loewe, Robert; Moser, Ewald

2011-06-01

99

Can the Neural Basis of Repression Be Studied in the MRI Scanner? New Insights from Two Free Association Paradigms  

PubMed Central

Background The psychodynamic theory of repression suggests that experiences which are related to internal conflicts become unconscious. Previous attempts to investigate repression experimentally were based on voluntary, intentional suppression of stimulus material. Unconscious repression of conflict-related material is arguably due to different processes, but has never been studied with neuroimaging methods. Methods We used functional magnetic resonance imaging (fMRI) in addition with skin conductance recordings during two free association paradigms to identify the neural mechanisms underlying forgetting of freely associated words according to repression theory. Results In the first experiment, free association to subsequently forgotten words was accompanied by increases in skin conductance responses (SCRs) and reaction times (RTs), indicating autonomic arousal, and by activation of the anterior cingulate cortex. These findings are consistent with the hypothesis that these associations were repressed because they elicited internal conflicts. To test this idea more directly, we conducted a second experiment in which participants freely associated to conflict-related sentences. Indeed, these associations were more likely to be forgotten than associations to not conflict-related sentences and were accompanied by increases in SCRs and RTs. Furthermore, we observed enhanced activation of the anterior cingulate cortex and deactivation of hippocampus and parahippocampal cortex during association to conflict-related sentences. Conclusions These two experiments demonstrate that high autonomic arousal during free association predicts subsequent memory failure, accompanied by increased activation of conflict-related and deactivation of memory-related brain regions. These results are consistent with the hypothesis that during repression, explicit memory systems are down-regulated by the anterior cingulate cortex.

Kessler, Henrik; Do Lam, Anne T. A.; Fell, Juergen; Schmidt, Anna-Christine; Axmacher, Nikolai

2013-01-01

100

Skin and proximity effects in the conductors of split gradient coils for a hybrid Linac-MRI scanner  

NASA Astrophysics Data System (ADS)

In magnetic resonance imaging (MRI), rapidly changing gradient fields are applied to encode the magnetic resonance signal with spatial position; however eddy currents are induced in the surrounding conducting structures depending on the geometry of the conductor and the excitation waveform. These alternating fields change the spatial profile of the current density within the coil track with the applied frequencies of the input waveform and by their proximity to other conductors. In this paper, the impact of the conductor width and the excited frequency over the parameters that characterise the performance of split transverse and longitudinal gradient coils are studied. Thirty x-gradient coils were designed using a “free-surface” coil design method and the track width was varied from 1 mm to 30 mm with an increment value of 1 mm; a frequency sweep analysis in the range of 100 Hz to 10 kHz was performed using the multi-layer integral method (MIM) and parameters such as power loss produced by the coil and generated in the cryostat, inductance, coil efficiency (field strength/operating current), magnetic field profile produced by the coil and the eddy currents were studied. An experimental validation of the theoretical model was performed on an example coil. Coils with filamentary conductor segments were also studied to compare the simulated parameters with those produced by coils with a finite track. There was found to be a significant difference between the parameters calculated using filamentary coils and those obtained when the coil is simulated using finite size tracks. A wider track width produces coil with superior efficiency and low resistance; however, due to the skin effect, the power loss increases faster in wider tracks than in those generated in coils with narrow tracks. It was demonstrated that rapidly changing current paths must be avoided in order to mitigate the power loss and the spatial asymmetry in the current density profile. The decision of using narrow or wider tracks in split coils should be carefully investigated using a temperature analysis which includes skin and proximity effects.

Tang, Fangfang; Lopez, Hector Sanchez; Freschi, Fabio; Smith, Elliot; Li, Yu; Fuentes, Miguel; Liu, Feng; Repetto, Maurizio; Crozier, Stuart

2014-05-01

101

Skin and proximity effects in the conductors of split gradient coils for a hybrid Linac-MRI scanner.  

PubMed

In magnetic resonance imaging (MRI), rapidly changing gradient fields are applied to encode the magnetic resonance signal with spatial position; however eddy currents are induced in the surrounding conducting structures depending on the geometry of the conductor and the excitation waveform. These alternating fields change the spatial profile of the current density within the coil track with the applied frequencies of the input waveform and by their proximity to other conductors. In this paper, the impact of the conductor width and the excited frequency over the parameters that characterise the performance of split transverse and longitudinal gradient coils are studied. Thirty x-gradient coils were designed using a "free-surface" coil design method and the track width was varied from 1mm to 30mm with an increment value of 1mm; a frequency sweep analysis in the range of 100Hz to 10kHz was performed using the multi-layer integral method (MIM) and parameters such as power loss produced by the coil and generated in the cryostat, inductance, coil efficiency (field strength/operating current), magnetic field profile produced by the coil and the eddy currents were studied. An experimental validation of the theoretical model was performed on an example coil. Coils with filamentary conductor segments were also studied to compare the simulated parameters with those produced by coils with a finite track. There was found to be a significant difference between the parameters calculated using filamentary coils and those obtained when the coil is simulated using finite size tracks. A wider track width produces coil with superior efficiency and low resistance; however, due to the skin effect, the power loss increases faster in wider tracks than in those generated in coils with narrow tracks. It was demonstrated that rapidly changing current paths must be avoided in order to mitigate the power loss and the spatial asymmetry in the current density profile. The decision of using narrow or wider tracks in split coils should be carefully investigated using a temperature analysis which includes skin and proximity effects. PMID:24607826

Tang, Fangfang; Lopez, Hector Sanchez; Freschi, Fabio; Smith, Elliot; Li, Yu; Fuentes, Miguel; Liu, Feng; Repetto, Maurizio; Crozier, Stuart

2014-05-01

102

Non-Enhanced MR Imaging of Cerebral Aneurysms: 7 Tesla versus 1.5 Tesla  

PubMed Central

Purpose To prospectively evaluate 7 Tesla time-of-flight (TOF) magnetic resonance angiography (MRA) in comparison to 1.5 Tesla TOF MRA and 7 Tesla non-contrast enhanced magnetization-prepared rapid acquisition gradient-echo (MPRAGE) for delineation of unruptured intracranial aneurysms (UIA). Material and Methods Sixteen neurosurgical patients (male n?=?5, female n?=?11) with single or multiple UIA were enrolled in this trial. All patients were accordingly examined at 7 Tesla and 1.5 Tesla MRI utilizing dedicated head coils. The following sequences were obtained: 7 Tesla TOF MRA, 1.5 Tesla TOF MRA and 7 Tesla non-contrast enhanced MPRAGE. Image analysis was performed by two radiologists with regard to delineation of aneurysm features (dome, neck, parent vessel), presence of artifacts, vessel-tissue-contrast and overall image quality. Interobserver accordance and intermethod comparisons were calculated by kappa coefficient and Lin's concordance correlation coefficient. Results A total of 20 intracranial aneurysms were detected in 16 patients, with two patients showing multiple aneurysms (n?=?2, n?=?4). Out of 20 intracranial aneurysms, 14 aneurysms were located in the anterior circulation and 6 aneurysms in the posterior circulation. 7 Tesla MPRAGE imaging was superior over 1.5 and 7 Tesla TOF MRA in the assessment of all considered aneurysm and image quality features (e.g. image quality: mean MPRAGE7T: 5.0; mean TOF7T: 4.3; mean TOF1.5T: 4.3). Ratings for 7 Tesla TOF MRA were equal or higher over 1.5 Tesla TOF MRA for all assessed features except for artifact delineation (mean TOF7T: 4.3; mean TOF1.5T 4.4). Interobserver accordance was good to excellent for most ratings. Conclusion 7 Tesla MPRAGE imaging demonstrated its superiority in the detection and assessment of UIA as well as overall imaging features, offering excellent interobserver accordance and highest scores for all ratings. Hence, it may bear the potential to serve as a high-quality diagnostic tool for pretherapeutic assessment and follow-up of untreated UIA.

Wrede, Karsten H.; Dammann, Philipp; Monninghoff, Christoph; Johst, Soren; Maderwald, Stefan; Sandalcioglu, I. Erol; Muller, Oliver; Ozkan, Neriman; Ladd, Mark E.; Forsting, Michael; Schlamann, Marc U.; Sure, Ulrich; Umutlu, Lale

2014-01-01

103

Functional MRI at 4.7 Tesla of the Rat Brain during Electric Stimulation of Forepaw, Hindpaw, or Tail in Single and Multislice Experiments  

Microsoft Academic Search

Stimulation of peripheral nerves activates corresponding regions in sensorimotor cortex. We have applied functional magnetic resonance imaging (fMRI) techniques to monitor activated brain regions by means of measuring changes of blood oxygenation level-dependent contrast during electric stimulation of the forepaw, hindpaw, or tail in rats. During ?-chloralose anesthesia, artificial respiration, and complete muscle relaxation, stimulations were delivered at 3 Hz

C. Spenger; A. Josephson; T. Klason; M. Hoehn; W. Schwindt; M. Ingvar; L. Olson

2000-01-01

104

Edison vs. Tesla  

SciTech Connect

As Edison vs. Tesla week heats up at the Energy Department, we are exploring the rivalry between Thomas Edison and Nikola Tesla and how their work is still impacting the way we use energy today. Whether you're on Team Tesla or Team Edison, both inventors were key players in creating things like batteries, power plants and wireless technologies -- all innovations we still use today. And as we move toward a clean energy future, energy efficient lighting, like LED bulbs, and more efficient electric motors not only help us save money on electricity costs but help combat climate change. For this, Tesla and Edison both deserve our recognition.

Hogan, Kathleen; Wallace, Hal; Ivestor, Rob

2013-11-20

105

Edison vs. Tesla  

ScienceCinema

As Edison vs. Tesla week heats up at the Energy Department, we are exploring the rivalry between Thomas Edison and Nikola Tesla and how their work is still impacting the way we use energy today. Whether you're on Team Tesla or Team Edison, both inventors were key players in creating things like batteries, power plants and wireless technologies -- all innovations we still use today. And as we move toward a clean energy future, energy efficient lighting, like LED bulbs, and more efficient electric motors not only help us save money on electricity costs but help combat climate change. For this, Tesla and Edison both deserve our recognition.

Hogan, Kathleen; Wallace, Hal; Ivestor, Rob

2014-01-07

106

Scanner Art  

ERIC Educational Resources Information Center

In this article, the authors describe how they incorporated environmental awareness into their art curriculum. Here, they describe a digital photography project in which their students used flatbed scanners as cameras. Their students composed their objects directly on the scanner. The lesson enabled students to realize that artists have voices…

Jaworski, Joy; Murphy, Kris

2009-01-01

107

Integrating structural and functional imaging for computer assisted detection of prostate cancer on multi-protocol in vivo 3 Tesla MRI  

Microsoft Academic Search

Screening and detection of prostate cancer (CaP) currently lacks an image-based protocol which is reflected in the high false negative rates currently associated with blinded sextant biopsies. Multi-protocol magnetic resonance imaging (MRI) offers high resolution functional and structural data about internal body structures (such as the prostate). In this paper we present a novel comprehensive computer-aided scheme for CaP detection

Satish Viswanath; B. Nicolas Bloch; Mark Rosen; Jonathan Chappelow; Robert Toth; Neil Rofsky; Robert Lenkinski; Elizabeth Genega; Arjun Kalyanpur; Anant Madabhushi

2009-01-01

108

Integrating structural and functional imaging for computer assisted detection of prostate cancer on multi-protocol in vivo 3 Tesla MRI  

NASA Astrophysics Data System (ADS)

Screening and detection of prostate cancer (CaP) currently lacks an image-based protocol which is reflected in the high false negative rates currently associated with blinded sextant biopsies. Multi-protocol magnetic resonance imaging (MRI) offers high resolution functional and structural data about internal body structures (such as the prostate). In this paper we present a novel comprehensive computer-aided scheme for CaP detection from high resolution in vivo multi-protocol MRI by integrating functional and structural information obtained via dynamic-contrast enhanced (DCE) and T2-weighted (T2-w) MRI, respectively. Our scheme is fully-automated and comprises (a) prostate segmentation, (b) multimodal image registration, and (c) data representation and multi-classifier modules for information fusion. Following prostate boundary segmentation via an improved active shape model, the DCE/T2-w protocols and the T2-w/ex vivo histological prostatectomy specimens are brought into alignment via a deformable, multi-attribute registration scheme. T2-w/histology alignment allows for the mapping of true CaP extent onto the in vivo MRI, which is used for training and evaluation of a multi-protocol MRI CaP classifier. The meta-classifier used is a random forest constructed by bagging multiple decision tree classifiers, each trained individually on T2-w structural, textural and DCE functional attributes. 3-fold classifier cross validation was performed using a set of 18 images derived from 6 patient datasets on a per-pixel basis. Our results show that the results of CaP detection obtained from integration of T2-w structural textural data and DCE functional data (area under the ROC curve of 0.815) significantly outperforms detection based on either of the individual modalities (0.704 (T2-w) and 0.682 (DCE)). It was also found that a meta-classifier trained directly on integrated T2-w and DCE data (data-level integration) significantly outperformed a decision-level meta-classifier, constructed by combining the classifier outputs from the individual T2-w and DCE channels.

Viswanath, Satish; Bloch, B. Nicolas; Rosen, Mark; Chappelow, Jonathan; Toth, Robert; Rofsky, Neil; Lenkinski, Robert; Genega, Elizabeth; Kalyanpur, Arjun; Madabhushi, Anant

2009-02-01

109

SOLID STATE TESLA COIL  

Microsoft Academic Search

Some years ago I developed an interest in Tesla coils. I was teaching a senior elective course at Kansas State University where we talked about power MOSFETs and topics related to high voltages and currents. I decided to use a Tesla coil as a class project. We would talk about design aspects, then design, build, and test a coil. The

Gary L. Johnson

2001-01-01

110

Tesla and AND gates  

Microsoft Academic Search

This column takes a closer look at the work of Nikola Tesla, a brilliant engineer and scientist who made incredible contributions in many diverse areas, such as radar and radio. Tesla was the first person to be awarded a patent on an AND gate.

Mel Breuer

2007-01-01

111

Molecular imaging probes spy on the body's inner workings: miniaturized microscopes, microbubbles, 7- and 15-T scanners, diffusion-tensor MRI, and other molecular-imaging technologies are pushing molecular imaging into the future.  

PubMed

Molecular imaging is one of the hot-button areas within medical imaging. This technology employs imaging techniques in concert with molecular probes, or biomarkers, that together noninvasively spy on cellular function and molecular processes. In some cases, this technology may be able to detect the very earliest stages of diseases and eliminate them on the spot. This paper discusses how miniaturized microscopes, microbubbles, 7T and 15T scanners, diffusion-tensor MRI and other molecular imaging technologies are pushing molecular imaging into the future. PMID:23411435

Mertz, Leslie

2013-01-01

112

Multi-Channel Metabolic Imaging, with SENSE reconstruction, of Hyperpolarized [1-13C] Pyruvate in a Live Rat at 3.0 tesla on a Clinical MR Scanner*  

PubMed Central

We report metabolic images of 13C, following injection of a bolus of of hyperpolarized [1-13C] pyruvate in a live rat. The data were acquired on a clinical scanner, using custom coils for volume transmission and array reception. Proton blocking of all carbon resonators enabled proton anatomic imaging with the system body coil, to allow for registration of anatomic and metabolic images, for which good correlation was achieved, with some anatomic features (kidney and heart) clearly visible in a carbon image, without reference to the corresponding proton image. Parallel imaging with sensitivity encoding was used to increase the spatial resolution in the SI direction of the rat. The signal to noise ratio in was in some instances unexpectedly high in the parallel images; variability of the polarization among different trials, plus partial volume effects, are noted as a possible cause of this.

Tropp, James; Lupo, Janine M.; Chen, Albert; Calderon, Paul; McCune, Don; Grafendorfer, Thomas; Ozturk-Isik, Esin; Larson, Peder E. Z.; Hu, Simon; Yen, Yi-Fen; Robb, Fraser; Bok, Robert; Schulte, Rolf; Xu, Duan; Hurd, Ralph; Vigneron, Daniel; Nelson, Sarah

2012-01-01

113

Piezoelectric scanners  

NASA Astrophysics Data System (ADS)

Bimorph piezoelectric elements show relative large axial displacements at moderate voltages. Their response to voltage variations is very fast. The reproducibility of the displacement is practically limited only by the mechanical and electrical supplementary equipment. In combination with a deflection mirror linear scans or two-dimensional scan pattern can be generated. Fast scanning with good linearity and repeatability is possible, either in a resonant mode or in a random access mode. However, the hysteresis of the piezoelectric material and the large capacitance of the elements impose some constraints on the applicability of the piezoelectric scanners. In the first part of the paper the properties of piezoelectric elements are discussed in view of scanner application; in the second part an experimental single mirror two-axis piezoelectric scanner is described. Some suggestions for future applications of piezoelectric scanners are made.

Hohner, M.; Manhart, S.

1987-03-01

114

In Vivo13C Magnetic Resonance Spectroscopy of Human Brain on a Clinical 3 Tesla Scanner Using [2-13C]Glucose Infusion and Low Power Stochastic Decoupling  

PubMed Central

This study presents the detection of [2-13C]glucose metabolism in the carboxylic/amide region in the human brain, and demonstrates that the cerebral metabolism of [2-13C]glucose can be studied in human subjects in the presence of severe hardware constraints of widely available 3 T clinical scanners and with low power stochastic decoupling. In the carboxylic/amide region of human brain, the primary products of 13C label incorporation from [2-13C]glucose into glutamate, glutamine, aspartate, ?-aminobutyric acid, and N-acetylaspartate were detected. Unlike the commonly used alkanyl region where lipid signals spread over a broad frequency range, the carboxylic carbon signal of lipids was found to be confined to a narrow range centered at 172.5 ppm and present no spectral interference in the absence of lipid suppression. Comparison using phantoms shows that stochastic decoupling is far superior than the commonly used WALTZ sequence at very low decoupling power at 3 T. It was found that glutamine C1 and C5 can be decoupled using stochastic decoupling at 2.2 W although glutamine protons span a frequency range of ?700 Hz. Detailed specific absorption rate analysis was also performed using finite difference time domain numerical simulation.

Li, Shizhe; Zhang, Yan; Wang, Shumin; Yang, Jehoon; Araneta, Maria Ferraris; Farris, Amanda; Johnson, Christopher; Fox, Stephen; Innis, Robert; Shen, Jun

2009-01-01

115

Science at 100 Tesla  

NASA Astrophysics Data System (ADS)

Within the last year, Los Alamos National Labs produced magnetic fields of 100 tesla strength non-destructively for the first time. Fields of such a strength open up many new possibilities for condensed matter research. I will present some recent examples of condensed matter physics experiments performed in magnetic fields reaching 100 tesla, which includes recent work on high temperature superconductivity, magnetism and low dimensional materials.

Harrison, Neil

2012-10-01

116

Tesla's contribution to radiowave propagation  

Microsoft Academic Search

We review Nikola Tesla's contribution to radiowave propagation and wireless power transmission. Tesla's patents, published and unpublished notes about radiowave propagation and wireless power transmission are less known, and if known to some extent, they are usually wrongly interpreted

Aleksandar Marincic; Djuradj Budimir

2001-01-01

117

Magnetic resonance imaging of iron-oxide labeled SK-Mel 28 human melanoma cells in the chick embryo using a clinical whole body MRI scanner  

Microsoft Academic Search

Purpose: To evaluate advantages and limitations of magnetic resonance imaging (MRI) to monitor the migration of superparamagnetic\\u000a iron oxide (SPIO) labeled cells in the chick embryo.\\u000a \\u000a \\u000a Materials and methods: Labeled human SK-Mel 28 melanoma cells were injected into the E2 chick embryo neural tube. Embryos were examined with a\\u000a clinical 3 T MRI whole body system using 3D T2*-weighted sequences

M. Oppitz; J. Pintaske; R. Kehlbach; F. Schick; G. Schriek; C. Busch

2007-01-01

118

Blood Flow and Anatomical MRI in a Mouse Model of Retinitis Pigmentosa  

PubMed Central

This study tested the sensitivity of an arterial spin labeling MRI method to image changes in retinal and choroidal blood flow (BF) and anatomical thickness of the retina in the rd10 mouse model of retinitis pigmentosa. High-resolution (42×42?m) MRI was performed on rd10 mice and age-matched controls at 25, 35, and 60 days of age (n=6 each group) on a 7-Tesla scanner. Anatomical MRI was acquired and quantitative BF was imaged using arterial spin labeling MRI with a separate cardiac labeling coil. Histology was obtained to confirm thickness changes in the retina. In control mice, the retinal and choroidal vascular layers were quantitatively resolved. In rd10 mice, retinal BF decreased progressively over time while choroidal BF was unchanged. The rd10 retina became progressively thinner at later time points compared to age-matched controls by anatomical MRI and histology (p<0.01). BF and anatomical MRI were capable of detecting decreased BF and thickness in the rd10 mouse retina. Because BF is tightly coupled to metabolic function, BF MRI has the potential to non-invasively assess retinal diseases in which metabolism and function are perturbed and to evaluate novel treatments, complementing existing retinal imaging techniques.

Muir, Eric R; De La Garza, Bryan; Duong, Timothy Q

2012-01-01

119

Development of functional imaging in the human brain (fMRI); the University of Minnesota experience  

PubMed Central

The human functional magnetic resonance imaging (fMRI) experiments performed in the Center for Magnetic Resonance Research (CMRR), University of Minnesota, were planned between two colleagues who had worked together previously in Bell Laboratories in the late nineteen seventies, namely myself and Seiji Ogawa. These experiments were motivated by the Blood Oxygenation Level Dependent (BOLD) contrast developed by Seiji. We discussed and planned human studies to explore imaging human brain activity using the BOLD mechanism on the 4 Tesla human system that I was expecting to receive for CMRR. We started these experiments as soon as this 4 Tesla instrument became marginally operational. These were the very first studies performed on the 4 Tesla scanner in CMRR; had the scanner became functional earlier, they would have been started earlier as well. We had positive results certainly by August 1991 annual meeting of the Society of Magnetic Resonance in Medicine (SMRM) and took some of the data with us to that meeting. I believe, however, that neither the MGH colleagues nor us, at the time, had enough data and/or conviction to publish these extraordinary observations; it took more or less another six months or so before the papers from these two groups were submitted for publication within five days of each other to the Proceedings of the National Academy of Sciences, USA, after rejections by Nature. Based on this record, it is fair to say that fMRI was achieved independently and at about the same time at MGH, in an effort credited largely to Ken Kwong, and in CMRR, University of Minnesota in an effort led by myself and Seiji Ogawa.

Ugurbil, Kamil

2012-01-01

120

Note: Tesla transformer damping.  

PubMed

Unexpected heavy damping in the two winding Tesla pulse transformer is shown to be due to small primary inductances. A small primary inductance is a necessary condition of operability, but is also a refractory inefficiency. A 30% performance loss is demonstrated using a typical "spiral strip" transformer. The loss is investigated by examining damping terms added to the transformer's governing equations. A significant alteration of the transformer's architecture is suggested to mitigate these losses. Experimental and simulated data comparing the 2 and 3 winding transformers are cited to support the suggestion. PMID:22852736

Reed, J L

2012-07-01

121

Note: Tesla transformer damping  

NASA Astrophysics Data System (ADS)

Unexpected heavy damping in the two winding Tesla pulse transformer is shown to be due to small primary inductances. A small primary inductance is a necessary condition of operability, but is also a refractory inefficiency. A 30% performance loss is demonstrated using a typical ``spiral strip'' transformer. The loss is investigated by examining damping terms added to the transformer's governing equations. A significant alteration of the transformer's architecture is suggested to mitigate these losses. Experimental and simulated data comparing the 2 and 3 winding transformers are cited to support the suggestion.

Reed, J. L.

2012-07-01

122

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

PubMed

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. PMID:24439698

Krämer, Martin; Reichenbach, Jürgen R

2014-05-01

123

Design of a small animal MR compatible PET scanner  

Microsoft Academic Search

Using a combination of Monte Carlo simulations and experimental measurements we have designed a small-animal MRI-compatible PET (McPET) scanner for simultaneous PET imaging and MRI of mice and rats in vivo. The scanner consists of one ring of 480 LSO (Lu2SiO5 ) crystals arranged in three layers, with 160 crystals per layer. The crystal dimensions are 2×3×7.5 mm3. This was

Randal Slates; Simon Cherry; Abdel Boutefnouchet; Yiping Shao; M. Dahlborn; Keyvan Farahani

1999-01-01

124

[Optimized magnetic resonance sequences and parameters with operative assisted images for radical prostatectomy at 3 tesla-magnetic resonance image].  

PubMed

The objective of our study was to optimize magnetic resonance image (MRI) sequences and parameters using operative assisted images (three-dimensional images) for radical prostatectomy at 3 tesla (T) MRI. Five healthy volunteers underwent MRI on the 3.0 T scanner. Various sequences and parameters [Cube (TE/TR = 18, 50, 90 ms/2000 ms), FIESTA (TE/TR/FA = 2.4 ms/5 ms/40 degrees, 90 degrees), fSPGR (TE/TR/FA = 2.3 ms/11.2 ms/20 degrees), slice thickness = 1.2 mm, matrix = 192 x 160] were respectively compared. Several structures of the pelvis (the central zones and transition zones of the prostate, the peripheral zones of the prostate, seminal vesicles, rectum wall, bladder, muscle and fat) were determined. The signal intensities of these structures were measured on reformatted axial images and compared against several structures of the pelvis. Correlation with various sequences and parameters was based on the signal-to-noise ratio (SNR), the contrast ratio (CR) and the presence of artifacts. Student's t-test was used for statistical analysis. With Cube (TE/TR = 50 ms/2000 ms), the average value of visual evaluation with artifacts was high, and SNR and CR were higher than for other sequence and parameters. Optimized MRI sequences and parameters were Cube (TE/TR = 50 ms/2000 ms) which provides improved SNR and CR and the presence of artifacts with operative assisted images for radical prostatectomy. These operative assisted images obtained from Cube (TE/TR = 50 ms/2000 ms) are likely to be useful for surgery. PMID:23964533

Shirase, Ryuji; Sakurai, Yuuki; Nagahama, Hiroshi; Harada, Kuniaki; Takashima, Hiroyuki; Nakanishi, Mitsuhiro; Harada, Kohei; Shishido, Hiroki; Imamura, Rui; Sakata, Motomichi; Hatakenaka, Masamitsu

2013-05-01

125

Murine orthostatic response during prolonged vertical studies: effect on cerebral blood flow measured by arterial spin-labeled MRI.  

PubMed

High-field MRI scanners are, in principle, well suited for mouse studies; however, many high-field magnets employ a vertical design that may influence the physiological state of the rodent. The purpose of this study was to investigate the orthostatic response of cerebral blood flow (CBF) in mice during a prolonged MR experiment in the vertical position. Arterial spin-labeled (ASL) MRI was performed at 4.7-Tesla with a 15-cm gradient insert that allowed horizontal and vertical CBF measurements to be obtained with the same scanner. For mice in the head-up (HU) vertical position, CBF decreased by approximately 40% compared to the horizontal position, although blood pressure did not differ. Furthermore, CBF values for vertically positioned mice treated with phenylephrine remained constant while blood pressure increased. These results support the conclusion that cerebral autoregulation was intact, albeit at a lower level. Since CBF recovers to near horizontal values by volume loading with saline, it appears that a decrease in central venous pressure (CVP) leading to an increase in sympathetic tone may be a contributing mechanism for lowered CBF. This suggests that using an HU vertical position for MRI in mice may have broader implications, especially for studies that rely on CBF (such as BOLD and fMRI). PMID:16142710

Foley, Lesley M; Hitchens, T Kevin; Kochanek, Patrick M; Melick, John A; Jackson, Edwin K; Ho, Chien

2005-10-01

126

The Interventional Loopless Antenna at 7 Tesla  

PubMed Central

The loopless antenna MRI detector is comprised of a tuned coaxial cable with an extended central conductor that can be fabricated at sub-millimeter diameters for inteventional use in guidewires, catheters or needles. Prior work up to 4.7T suggests a near-quadratic gain in signal-to-noise ratio (SNR) with field strength, and safe operation at 3T. Here for the first time, the SNR performance and RF safety of the loopless antenna is investigated both theoretically, using the electro-magnetic method-of-moments, and experimentally in a standard 7T human scanner. The results are compared with equivalent 3T devices. An absolute SNR gain of 5.7±1.5-fold was realized at 7T vs. 3T: more than 20-fold higher than at 1.5T. The effective field-of-view (FOV) area also increased approximately 10-fold compared to 3T. Testing in a saline gel phantom suggested safe operation is possible with maximum local 1-g average specific absorption rates of <12W/kg and temperature increases of <1.9°C, normalized to a 4W/kg RF field exposure at 7T. The antenna did not affect the power applied to the scanner's transmit coil. The SNR gain enabled MRI microscopy at 40-50?m resolution in diseased human arterial specimens, offering the potential of high-resolution large-FOV or endoscopic MRI for targeted intervention in focal disease.

Erturk, Mehmet Arcan; El-Sharkawy, AbdEl-Monem M.; Bottomley, Paul A.

2012-01-01

127

Nikola Tesla: 145 years of visionary ideas  

Microsoft Academic Search

The paper gives a short review of Tesla's major inventions including the rotating magnetic field, the Tesla coil and transformer, and the power struggle between Edison's direct current systems and the Tesla-Westinghouse alternating current approach. It also looks at some of Tesla's visionary ideas

Jasmina Vujic; Aleksandar Marincic; Milos Ercegovac; Bratislav Milovanovic

2001-01-01

128

Integrating a MRI scanner with a 6 MV radiotherapy accelerator: impact of the surface orientation on the entrance and exit dose due to the transverse magnetic field.  

PubMed

At the UMC Utrecht, in collaboration with Elekta and Philips Research Hamburg, we are developing a radiotherapy accelerator with integrated MRI functionality. The radiation dose will be delivered in the presence of a lateral 1.5 T field. Although the photon beam is not affected by the magnetic field, the actual dose deposition is done by a cascade of secondary electrons and these electrons are affected by the Lorentz force. The magnetic field causes a reduced build-up distance: because the trajectory of the electrons between collisions is curved, the entrance depth in tissue decreases. Also, at tissue-air interfaces an increased dose occurs due to the so-called electron return effect (ERE): electrons leaving tissue will describe a circular path in air and re-enter the tissue yielding a local dose increase. In this paper the impact of a 1.5 T magnetic field on both the build-up distance and the dose increase due to the ERE will be investigated as a function of the angle between the surface and the incident beam. Monte Carlo simulations demonstrate that in the presence of a 1.5 T magnetic field, the surface dose, the build-up distance and the exit dose depend more heavily on the surface orientation than in the case without magnetic field. This is caused by the asymmetrical pointspread kernel in the presence of 1.5 T and the directional behaviour of the re-entering electrons. Simulations on geometrical phantoms show that ERE dose increase at air cavities can be avoided using opposing beams, also when the air-tissue boundary is not perpendicular to the beam. For the more general case in patient anatomies, more problems may arise. Future work will address the possibilities and limitations of opposing beams in combination with IMRT in a magnetic field. PMID:17264362

Raaijmakers, A J E; Raaymakers, B W; van der Meer, S; Lagendijk, J J W

2007-02-21

129

[70 years of Nikola Tesla studies].  

PubMed

Nikola Tesla's studies of chemistry are described including his not very scholarly affair in Maribor. After almost a century and half of hypothesis at least usable scenario of Tesla's life and "work" in Maribor is provided. The chemistry achievements of Tesla's most influential professors Martin Sekuli? and Tesla's Graz professors are put into the limelight. The fact that Tesla in Graz studied on the technological chemistry Faculty of Polytechnic is focused. PMID:23878954

Juznic, Stanislav

2013-01-01

130

Safety of localizing epilepsy monitoring intracranial electroencephalograph electrodes using MRI: Radiofrequency-induced heating  

PubMed Central

Purpose To investigate heating during postimplantation localization of intracranial electroencephalograph (EEG) electrodes by MRI. Materials and Methods A phantom patient with a realistic arrangement of electrodes was used to simulate tissue heating during MRI. Measurements were performed using 1.5 Tesla (T) and 3T MRI scanners, using head- and body-transmit RF-coils. Two electrode-lead configurations were assessed: a “standard” condition with external electrode-leads physically separated and a “fault” condition with all lead terminations electrically shorted. Results Using a head-transmit–receive coil and a 2.4 W/kg head-average specific absorption rate (SAR) sequence, at 1.5T the maximum temperature change remained within safe limits (<1°C). Under “standard” conditions, we observed greater heating (?2.0°C) at 3T on one system and similar heating (<1°C) on a second, compared with the 1.5T system. In all cases these temperature maxima occurred at the grid electrode. In the “fault” condition, larger temperature increases were observed at both field strengths, particularly for the depth electrodes. Conversely, with a body-transmit coil at 3T significant heating (+6.4°C) was observed (same sequence, 1.2/0.5 W/kg head/body-average) at the grid electrode under “standard” conditions, substantially exceeding safe limits. These temperature increases neglect perfusion, a major source of heat dissipation in vivo. Conclusion MRI for intracranial electrode localization can be performed safely at both 1.5T and 3T provided a head-transmit coil is used, electrode leads are separated, and scanner-reported SARs are limited as determined in advance for specific scanner models, RF coils and implant arrangements. Neglecting these restrictions may result in tissue injury. J. Magn. Reson. Imaging 2008;28:1233–1244. © 2008 Wiley-Liss, Inc.

Carmichael, David W; Thornton, John S; Rodionov, Roman; Thornton, Rachel; McEvoy, Andrew; Allen, Philip J; Lemieux, Louis

2008-01-01

131

What is Scanner and NonScanner?  

... NOAA satellite platforms by TRW of Redondo Beach, CA. Scanner A set of three co-planar detectors (longwave, shortwave and total ... satellite track (in its normal operational mode). The scanner instrument has a smaller footprint (40 km at nadir) and scanned across ...

2013-03-05

132

Nikola Tesla: the Moon's rotation.  

NASA Astrophysics Data System (ADS)

The review of three articles by N. Tesla, published in the year 1919 in the journal "Electrical experimenter" is given, with special reference to the astronomical contents and to circumstances in which they appeared.

Tomi?, A.; Jovanovi?, B. S.

1993-09-01

133

[Nikola Tesla in medicine, too].  

PubMed

Using primary and secondary sources we have shown in this paper the influence of Nikola Tesla's work on the field of medicine. The description of his experiments conduced within secondary-school education programs aimed to present the popularization of his work in Croatia. Although Tesla was dedicated primarily to physics and was not directly involved in biomedical research, his work significantly contributed to paving the way of medical physics particularly radiology and high-frequency electrotherapy. PMID:18383745

Hanzek, Branko; Jakobovi?, Zvonimir

2007-12-01

134

A Phantom for Diffusion MRI  

Cancer.gov

Combining a Diffusion MRI phantom with a resolution phantom would allow the same device to be used to calibrate an MR scanner''s image quality and the accuracy and precision of its diffusion measurements. This would be useful particularly for Radiological QA and for use in assuring data quality in longitudinal and multi-subject studies.

135

Improving the spatial accuracy in functional magnetic resonance imaging (fMRI) based on the blood oxygenation level dependent (BOLD) effect: benefits from parallel imaging and a 32-channel head array coil at 1.5 Tesla.  

PubMed

Geometric distortions and low spatial resolution are current limitations in functional magnetic resonance imaging (fMRI). The aim of this study was to evaluate if application of parallel imaging or significant reduction of voxel size in combination with a new 32-channel head array coil can reduce those drawbacks at 1.5 T for a simple hand motor task. Therefore, maximum t-values (tmax) in different regions of activation, time-dependent signal-to-noise ratios (SNR(t)) as well as distortions within the precentral gyrus were evaluated. Comparing fMRI with and without parallel imaging in 17 healthy subjects revealed significantly reduced geometric distortions in anterior-posterior direction. Using parallel imaging, tmax only showed a mild reduction (7-11%) although SNR(t) was significantly diminished (25%). In 7 healthy subjects high-resolution (2 x 2 x 2 mm3) fMRI was compared with standard fMRI (3 x 3 x 3 mm3) in a 32-channel coil and with high-resolution fMRI in a 12-channel coil. The new coil yielded a clear improvement for tmax (21-32%) and SNR(t) (51%) in comparison with the 12-channel coil. Geometric distortions were smaller due to the smaller voxel size. Therefore, the reduction in tmax (8-16%) and SNR(t) (52%) in the high-resolution experiment seems to be tolerable with this coil. In conclusion, parallel imaging is an alternative to reduce geometric distortions in fMRI at 1.5 T. Using a 32-channel coil, reduction of the voxel size might be the preferable way to improve spatial accuracy. PMID:19713602

Fellner, C; Doenitz, C; Finkenzeller, T; Jung, E M; Rennert, J; Schlaier, J

2009-01-01

136

Ultrashort Echo Time for Improved Positive-Contrast Manganese-Enhanced MRI of Cancer  

PubMed Central

Objective Manganese (Mn) is a positive magnetic resonance imaging (MRI) contrast agent that has been used to obtain physiological, biochemical, and molecular biological information. There is great interest to broaden its applications, but a major challenge is to increase detection sensitivity. Another challenge is distinguishing regions of Mn-related signal enhancement from background tissue with inherently similar contrast. To overcome these limitations, this study investigates the use of ultrashort echo time (UTE) and subtraction UTE (SubUTE) imaging for more sensitive and specific determination of Mn accumulation. Materials and Methods Simulations were performed to investigate the feasibility of UTE and SubUTE for Mn-enhanced MRI and to optimize imaging parameters. Phantoms containing aqueous Mn solutions were imaged on a MRI scanner to validate simulations predictions. Breast cancer cells that are very aggressive (MDA-MB-231 and a more aggressive variant LM2) and a less aggressive cell line (MCF7) were labeled with Mn and imaged on MRI. All imaging was performed on a 3 Tesla scanner and compared UTE and SubUTE against conventional T1-weighted spoiled gradient echo (SPGR) imaging. Results Simulations and phantom imaging demonstrated that UTE and SubUTE provided sustained and linearly increasing positive contrast over a wide range of Mn concentrations, whereas conventional SPGR displayed signal plateau and eventual decrease. Higher flip angles are optimal for imaging higher Mn concentrations. Breast cancer cell imaging demonstrated that UTE and SubUTE provided high sensitivity, with SubUTE providing background suppression for improved specificity and eliminating the need for a pre-contrast baseline image. The SubUTE sequence allowed the best distinction of aggressive breast cancer cells. Conclusions UTE and SubUTE allow more sensitive and specific positive-contrast detection of Mn enhancement. This imaging capability can potentially open many new doors for Mn-enhanced MRI in vascular, cellular, and molecular imaging.

Nofiele, Joris Tchouala; Cheng, Hai-Ling Margaret

2013-01-01

137

Brain Activation in Response to Visually Evoked Sexual Arousal in Male-to-Female Transsexuals: 3.0 Tesla Functional Magnetic Resonance Imaging  

PubMed Central

Objective This study used functional magnetic resonance imaging (fMRI) to contrast the differential brain activation patterns in response to visual stimulation with both male and female erotic nude pictures in male-to-female (MTF) transsexuals who underwent a sex reassignment surgery. Materials and Methods A total of nine healthy MTF transsexuals after a sex reassignment surgery underwent fMRI on a 3.0 Tesla MR Scanner. The brain activation patterns were induced by visual stimulation with both male and female erotic nude pictures. Results The sex hormone levels of the postoperative MTF transsexuals were in the normal range of healthy heterosexual females. The brain areas, which were activated by viewing male nude pictures when compared with viewing female nude pictures, included predominantly the cerebellum, hippocampus, putamen, anterior cingulate gyrus, head of caudate nucleus, amygdala, midbrain, thalamus, insula, and body of caudate nucleus. On the other hand, brain activation induced by viewing female nude pictures was predominantly observed in the hypothalamus and the septal area. Conclusion Our findings suggest that distinct brain activation patterns associated with visual sexual arousal in postoperative MTF transsexuals reflect their sexual orientation to males.

Oh, Seok-Kyun; Kim, Gwang-Won; Yang, Jong-Chul; Kim, Seok-Kwun; Kang, Heoung-Keun

2012-01-01

138

Mapping tissue sodium concentration in the human brain: A comparison of MR sequences at 9.4Tesla.  

PubMed

Sodium is the second most abundant MR-active nucleus in the human body and is of fundamental importance for the function of cells. Previous studies have shown that many pathophysiological conditions induce an increase of the average tissue sodium concentration. To date, several MR sequences have been used to measure sodium. The aim of this study was to evaluate the performance and suitability of five different MR sequences for quantitative sodium imaging on a whole-body 9.4Tesla MR scanner. Numerical simulations, phantom experiments and in vivo imaging on healthy subjects were carried out. The results demonstrate that, of these five sequences, the Twisted Projection Imaging sequence is optimal for quantitative sodium imaging, as it combines a number of features which are particularly relevant in order to obtain high quality quantitative images of sodium. These include: ultra-short echo times, efficient k-space sampling, and robustness against off-resonance effects. Mapping of sodium in the human brain is a technique not yet fully explored in neuroscience. Ultra-high field sodium MRI may provide new insights into the pathogenesis of neurological disorders, and may help to develop new and disease-specific biomarkers for the early diagnosis and therapeutic intervention before irreversible brain damage has taken place. PMID:24721332

Romanzetti, Sandro; Mirkes, Christian C; Fiege, Daniel P; Celik, Avdo; Felder, Jörg; Shah, N Jon

2014-08-01

139

Functional MRI for immediate monitoring stereotactic thalamotomy in a patient with essential tremor.  

PubMed

The effect of stereotactic thalamotomy was assessed with pre- and postoperative functional magnetic resonance imaging (fMRI) under motor stimulation. A patient with unilateral essential tremor (ET) of the left arm underwent stereotactically guided thalamotomy of the right ventral intermediate thalamic nucleus (VIM). FMRI was done directly before and after surgery on a 1.5-Tesla scanner. The stimulation paradigm was maintainance of the affected arm in an extended position and hand clenching being performed in a block design manner. Statistical analysis was done with Brain Voyager 2000. After thalamotomy the tremor diminished completely. As a difference between the pre- and postoperative fMRI, a significant activation was found in the VIM contralateral to the activation site, adjacent to the inferior olivary nucleus contralateral to the activation site and in the dorsal cingulum. In conclusion, fMRI can detect the functional effect of thalamotomy for tremor treatment. Direct postoperative fMRI provides a sufficient method for estimating the effect of thalamotomy immediately after intervention. The importance of the intermediate thalamic nucleus and the olivary nucleus in tremor generation is supported by our findings. PMID:16625350

Hesselmann, Volker; Maarouf, Mohammed; Hunsche, Stefan; Lasek, Kathrin; Schaaf, Maike; Krug, Barbara; Lackner, Klaus; Sturm, Volker; Wedekind, Christoph

2006-10-01

140

The Underwater Communication System of Nikola Tesla  

Microsoft Academic Search

Modern analysts, both those who believe Tesla had discovered something new and those who believe he was mistaken in his observations, see Tesla's transmission method the same as pre- sent day broadcast radio technology. The broadcast model assumes that there is an antenna propagating electromagnetic waves omnidirectionally into the air. The Tesla supporters propose many ingenious, but implausible, schemes that

Oliver Nichelson

141

7 Tesla imaging of cerebral radiation necrosis after arteriovenous malformations treatment using amide proton transfer (APT) imaging.  

PubMed

Arteriovenous malformations (AVM) can be treated with stereotactic radiosurgery. An infrequent, but important complication of this treatment is radionecrosis, which can be detected by MRI. However, the imaging characteristics of necrosis are unspecific in conventional MRI. Here, we report a case of necrosis after radiotherapy of an AVM to illustrate the potential of 7 Tesla MRI including amide proton transfer (APT) for necrosis imaging. PMID:22246564

Gerigk, Lars; Schmitt, Benjamin; Stieltjes, Bram; Röder, Falk; Essig, Marco; Bock, Michael; Schlemmer, Heinz-Peter; Röthke, Matthias

2012-05-01

142

TESLA-N electron scattering with polarized targets at TESLA  

Microsoft Academic Search

Measurements of polarized eN scattering can be realized at the TESLA linear collider facility at DESY with luminosities that are about two orders of magnitude higher than those expected for other experiments at comparable energies. A large variety of polarized parton distribution and fragmentation functions can be determined with unprecedented accuracy, many of them for the first time. .

2001-01-01

143

Volitional Reduction of Anterior Cingulate Cortex Activity Produces Decreased Cue Craving in Smoking Cessation: A Preliminary Real-Time fMRI Study  

PubMed Central

Numerous research groups are now using analysis of blood-oxygen-level dependent (BOLD) functional magnetic resonance imaging (fMRI) results and relaying back information about regional activity in their brains to participants in the scanner in “real time”. In this study, we explored the feasibility of self-regulation of frontal cortical activation using real time fMRI (rtfMRI) neurofeedback in nicotine-dependent cigarette smokers during exposure to smoking cues. Ten cigarette smokers were shown smoking-related visual cues in a 3 Tesla MRI scanner to induce their nicotine craving. Participants were instructed to modify their craving using rtfMRI feedback with two different approaches. In a “reduce craving” paradigm, participants were instructed to “reduce” their craving, and decrease the anterior cingulate cortex (ACC) activity. In a separate “increase resistance” paradigm, participants were asked to increase their resistance to craving and to increase middle prefrontal cortex (mPFC) activity. We found that participants were able to significantly reduce the BOLD signal in the ACC during the “reduce craving” task (p=0.028). There was a significant correlation between decreased ACC activation and reduced craving ratings during the “reduce craving” session (p=0.011). In contrast, there was no modulation of the BOLD signal in mPFC during the “increase resistance” session. These preliminary results suggest that some smokers may be able to use neurofeedback via rtfMRI to voluntarily regulate ACC activation and temporarily reduce smoking cue-induced craving. Further research is needed to determine the optimal parameters of neurofeedback rtfMRI, and whether it might eventually become a therapeutic tool for nicotine dependence.

Li, Xingbao; Hartwell, Karen J.; Borckardt, Jeffery; Prisciandaro, James J.; Saladin, Michael E.; Morgan, Paul S.; Johnson, Kevin A.; LeMatty, Todd; Brady, Kathleen T.; George, Mark S.

2012-01-01

144

Quantitative Renal Perfusion Measurements in a Rat Model of Acute Kidney Injury at 3T: Testing Inter- and Intramethodical Significance of ASL and DCE-MRI  

PubMed Central

Objectives To establish arterial spin labelling (ASL) for quantitative renal perfusion measurements in a rat model at 3 Tesla and to test the diagnostic significance of ASL and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in a model of acute kidney injury (AKI). Material and Methods ASL and DCE-MRI were consecutively employed on six Lewis rats, five of which had a unilateral ischaemic AKI. All measurements in this study were performed on a 3 Tesla MR scanner using a FAIR True-FISP approach and a TWIST sequence for ASL and DCE-MRI, respectively. Perfusion maps were calculated for both methods and the cortical perfusion of healthy and diseased kidneys was inter- and intramethodically compared using a region-of-interest based analysis. Results/Significance Both methods produce significantly different values for the healthy and the diseased kidneys (P<0.01). The mean difference was 147±47 ml/100 g/min and 141±46 ml/100 g/min for ASL and DCE-MRI, respectively. ASL measurements yielded a mean cortical perfusion of 416±124 ml/100 g/min for the healthy and 316±102 ml/100 g/min for the diseased kidneys. The DCE-MRI values were systematically higher and the mean cortical renal blood flow (RBF) was found to be 542±85 ml/100 g/min (healthy) and 407±119 ml/100 g/min (AKI). Conclusion Both methods are equally able to detect abnormal perfusion in diseased (AKI) kidneys. This shows that ASL is a capable alternative to DCE-MRI regarding the detection of abnormal renal blood flow. Regarding absolute perfusion values, nontrivial differences and variations remain when comparing the two methods.

Zimmer, Fabian; Zollner, Frank G.; Hoeger, Simone; Klotz, Sarah; Tsagogiorgas, Charalambos; Kramer, Bernhard K.; Schad, Lothar R.

2013-01-01

145

Effect of Acupuncture in Mild Cognitive Impairment and Alzheimer Disease: A Functional MRI Study  

PubMed Central

We aim to clarify the mechanisms of acupuncture in treating mild cognitive impairment (MCI) and Alzheimer disease (AD) by using functional magnetic resonance imaging (fMRI). Thirty-six right-handed subjects (8 MCI patients, 14 AD patients, and 14 healthy elders) participated in this study. Clinical and neuropsychological examinations were performed on all the subjects. MRI data acquisition was performed on a SIEMENS verio 3-Tesla scanner. The fMRI study used a single block experimental design. We first acquired the baseline resting state data in the initial 3 minutes; we then acquired the fMRI data during the procession of acupuncture stimulation on the acupoints of Tai chong and Hegu for the following 3 minutes. Last, we acquired fMRI data for another 10 minutes after the needle was withdrawn. The preprocessing and data analysis were performed using the statistical parametric mapping (SPM8) software. Then the two-sample t-tests were performed between each two groups of different states. We found that during the resting state, brain activities in AD and MCI patients were different from those of control subjects. During the acupuncture and the second resting state after acupuncture, when comparing to resting state, there are several regions showing increased or decreased activities in MCI, AD subjects compared to normal subjects. Most of the regions were involved in the temporal lobe and the frontal lobe, which were closely related to the memory and cognition. In conclusion, we investigated the effect of acupuncture in AD and MCI patients by combing fMRI and traditional acupuncture. Our fMRI study confirmed that acupuncture at Tai chong (Liv3) and He gu (LI4) can activate certain cognitive-related regions in AD and MCI patients.

Wang, Zhiqun; Nie, Binbin; Li, Donghong; Zhao, Zhilian; Han, Ying; Song, Haiqing; Xu, Jianyang; Shan, Baoci; Lu, Jie; Li, Kuncheng

2012-01-01

146

Evaluating requirements for spatial resolution of fMRI for neurosurgical planning.  

PubMed

The unambiguous localization of eloquent functional areas is necessary to decrease the neurological morbidity of neurosurgical procedures. We explored the minimum spatial resolution requirements for functional magnetic resonance imaging (fMRI) data acquisition when brain mapping is used in neurosurgical planning and navigation. Using a 1.5 Tesla clinical MRI scanner, eight patients with brain tumors underwent fMRI scans using spatial resolution of approximately 4 x 4 x 4 mm(3) to map the eloquent motor and language areas during the performance of cognitive/sensorimotor tasks. The fMRI results were then used intra-operatively in an open MRI system to delineate eloquent areas. Retrospectively, activation patterns were visually inspected by a neurosurgeon to determine qualitatively whether ambiguity with respect to the activation boundaries, due to low spatial resolution, could be of potential significance for surgical guidance. A significant degree of ambiguity in both the extent and shape of activation was judged to be present in data from six of the eight patients. Analysis of fMRI data at multiple resolutions from a normal volunteer showed that at 3 mm isotropic resolution, eloquent areas were better localized within the gray matter although there was still some potential for ambiguity caused by activations appearing to cross a sulcus. The data acquired with 2-mm isotropic voxels significantly enhanced the spatial localization of activation to within the gray matter. Thus, isotropic spatial resolution on the order of 2 x 2 x 2 mm(3), which is much higher than the resolutions used in typical fMRI examinations, may be needed for the unambiguous identification of cortical activation with respect to tumors and important anatomical landmarks. PMID:14689508

Yoo, Seung-Schik; Talos, Ion-Florin; Golby, Alexandra J; Black, Peter McL; Panych, Lawrence P

2004-01-01

147

Nikola Tesla Educational Opportunity School.  

ERIC Educational Resources Information Center

Describes the architectural design, costs, general description, and square footage data for the Nikola Tesla Educational Opportunity School in Colorado Springs, Colorado. A floor plan and photos are included along with a list of manufacturers and suppliers used for the project. (GR)

Design Cost Data, 2001

2001-01-01

148

Luminosity monitor studies for TESLA.  

National Technical Information Service (NTIS)

The feasibility of a luminosity monitor based on a radiative Bhabha detector is investigated n the context of the TESLA linear collider. Another option based on low energy e(sup +)e(sup -) pair calorimetry is also discussed. In order to monitor the beam p...

O. Napoly D. Schulte

1997-01-01

149

Functional magnetic resonance imaging of eye dominance at 4 tesla.  

PubMed

We studied eye dominance in visual cortex and lateral geniculate nucleus (LGN) using functional magnetic resonance imaging (fMRI) at a very high magnetic field (4 tesla). Eight normal volunteers were studied with fMRI at 4 tesla during alternating monocular visual stimulation. The acquisition was repeated twice in 4 subjects to confirm reproducibility. In addition, magnetic resonance signal intensities during three conditions (right eye stimulation, left eye stimulation, and control condition) were compared to determine whether the observed area was truly or relatively monocular in 2 subjects. In both the individual and group analyses, the anterior striate cortex was consistently activated by the contralateral eye more than the ipsilateral eye. Additionally, we found evidence that there were areas in the bilateral LGN which were more active during the stimulation of the contralateral eye than during the stimulation of the ipsilateral eye. The activated areas were reproducible, and the mean ratio of the overlapping area was 0.71 for the repeated scans. The additional experiment revealed that the area in the anterior visual cortex could be divided into two parts, one truly monocular and the other relatively monocular. Our finding confirmed previous fMRI results at 1.5 tesla showing that eye dominance was observed in the contralateral anterior visual cortex. However, the eye dominance in the visual cortex was found not only in the most anterior area corresponding to the monocular temporal crescent but also in the more posterior area, presumably showing the greater sensitivity of the temporal visual field (nasal retina) as compared with the nasal visual field (temporal retina) in the peripheral visual field (peripheral retina). In addition, it is suggested that the nasotemporal asymmetry of the retina and the visual fields is represented in the LGN as well as in the visual cortex. PMID:11586061

Miki, A; Liu, G T; Englander, S A; van Erp, T G; Bonhomme, G R; Aleman, D O; Liu, C S; Haselgrove, J C

2001-01-01

150

INVESTIGATING LASER SCANNER ACCURACY  

Microsoft Academic Search

Questions concerning the quality and accuracy of the recorded 3D points of laser scanners recei ve little attention. In a resear ch project, i3mainz has installed a number of different test target s that allow an investigation in the quality of points recorded by laser scanners and the geometric models derived from the point clouds. The standardized tests also allow

W. Boehler; M. Bordas Vicent; A. Marbs

2003-01-01

151

Scanner analyzer target  

Microsoft Academic Search

This paper describes a black and white photographic chart called the 'Scanner Analyzer Target' developed as a practical aid toward analyzing scanned image quality produced by binary digital document scanners used as input devices in document image processing systems. The target is used by factory-line personnel as an 'adjustment-set' tool, by the quality control department as an image quality judgement

Roland Simonis

1991-01-01

152

Workflow assessment of 3T MRI-guided transperineal targeted prostate biopsy using a robotic needle guidance  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) guided transperineal targeted prostate biopsy has become a valuable instrument for detection of prostate cancer in patients with continuing suspicion for aggressive cancer after transrectal ultrasound guided (TRUS) guided biopsy. The MRI-guided procedures are performed using mechanical targeting devices or templates, which suffer from limitations of spatial sampling resolution and/or manual in-bore adjustments. To overcome these limitations, we developed and clinically deployed an MRI-compatible piezoceramic-motor actuated needle guidance device, Smart Template, which allows automated needle guidance with high targeting resolution for use in a wide closed-bore 3-Tesla MRI scanner. One of the main limitations of the MRI-guided procedure is the lengthy procedure time compared to conventional TRUS-guided procedures. In order to optimize the procedure, we assessed workflow of 30 MRI-guided biopsy procedures using the Smart Template with focus on procedure time. An average of 3.4 (range: 2~6) targets were preprocedurally selected per procedure and 2.2 ± 0.8 biopsies were performed for each target with an average insertion attempt of 1.9 ± 0.7 per biopsy. The average technical preparation time was 14 ± 7 min and the in-MRI patient preparation time was 42 ± 7 min. After 21 ± 7 min of initial imaging, 64 ± 12 min of biopsy was performed yielding an average of 10 ± 2 min per tissue sample. The total procedure time occupying the MRI suite was 138 ± 16 min. No noticeable tendency in the length of any time segment was observed over the 30 clinical cases.

Song, Sang-Eun; Tuncali, Kemal; Tokuda, Junichi; Fedorov, Andriy; Penzkofer, Tobias; Fennessy, Fiona; Tempany, Clare; Yoshimitsu, Kitaro; Magill, John; Hata, Nobuhiko

2014-03-01

153

Review of quantitative MRI principles for gel dosimetry  

Microsoft Academic Search

The radiation dose distribution absorbed by polymer gel dosimeters can be read out by several methods such as magnetic resonance imaging (MRI), optical CT, X-ray CT and ultrasound. MRI was the first method that was explored to read out polymer gel dosimeters. Although MRI was soon recognised as a promising technique, limited access to MRI scanners and the often (wrongly

Yves DeDeene

2009-01-01

154

A novel integrative method for analyzing eye and hand behaviour during reaching and grasping in an MRI environment.  

PubMed

The development of noninvasive neuroimaging techniques, such as fMRI, has rapidly advanced our understanding of the neural systems underlying the integration of visual and motor information. However, the fMRI experimental design is restricted by several environmental elements, such as the presence of the magnetic field and the restricted view of the participant, making it difficult to monitor and measure behaviour. The present article describes a novel, specialized software package developed in our laboratory called Biometric Integration Recording and Analysis (BIRA). BIRA integrates video with kinematic data derived from the hand and eye, acquired using MRI-compatible equipment. The present article demonstrates the acquisition and analysis of eye and hand data using BIRA in a mock (0 Tesla) scanner. A method for collecting and integrating gaze and kinematic data in fMRI studies on visuomotor behaviour has several advantages: Specifically, it will allow for more sophisticated, behaviourally driven analyses and eliminate potential confounds of gaze or kinematic data. PMID:21424188

Lawrence, Jane M; Abhari, Kamyar; Prime, Steven L; Meek, Benjamin P; Desanghere, Loni; Baugh, Lee A; Marotta, Jonathan J

2011-06-01

155

Image quality and signal distribution in 1.5-T and 3-T MRI in mild traumatic brain injury patients  

NASA Astrophysics Data System (ADS)

Clear standards are lacking in the imaging modalities of the deficit in mild traumatic brain injury (MTBI) patients. The purpose of this study is to compare the image quality by signal distribution between 1.5 Tesla and 3 Tesla MRI in turbo spin echo (TSE) and gradient echo (GRE) images in normal hospital settings and to find preferences for which field to use in MTBI patients. We studied 40 MTBI patients with TSE and GRE; 20 patients were imaged at 1.5 T and 20 at 3 T. The imaging parameters were optimized separately for the two scanners. Histograms of the signal distribution in 22 ROIs were fitted to a 1-peak Gaussian model and the resulting peak positions were scaled in respect to the peak positions of genu of the corpus callosum and the caudate nuclei. Correlation of the contrast of the ROIs in reference to genu of the corpus callosum between both the two scanners and the two imaging sequences was good. Image contrast was similar at both in the TSE images; in the GRE images contrast improved from 1.5 T to 3 T. However, based on peak positions and widths, a slight drawback in the separability between the ROIs was observed when 1.5 T MRI was replaced by 3 T. No clear improvement in tissue contrast or separability of 3 T was found compared to 1.5 T. Imaging of MTBI with 3 T should therefore be based on other advantages of high-field imaging, such as improved SNR and spatial resolution.

Rossi, Maija E.; Dastidar, Prasun; Ryymin, Pertti; Ylinen, Aarne; Öhman, Juha; Soimakallio, Seppo; Eskola, Hannu

2009-02-01

156

The legacy of Nikola Tesla  

Microsoft Academic Search

Electrical power supply has grown enormously during this century. In 1950 the total capacity of generators producing electricity\\u000a in India was less than 3000 MW. Today, the power generating capacity is around 120,000 MW. The polyphase AC system, which\\u000a is to a large extent the legacy of Nikola Tesla, is central to all power generation. Power systems these days are

D P Sen Gupta

2007-01-01

157

Visualization of 3D geometric models of the breast created from contrast-enhanced MRI  

NASA Astrophysics Data System (ADS)

Contrast enhanced breast MRI is currently used as an adjuvant modality to x-ray mammography because of its ability to resolve ambiguities and determine the extent of malignancy. This study described techniques to create and visualize 3D geometric models of abnormal breast tissue. MRIs were performed on a General Electric 1.5 Tesla scanner using dual phased array breast coils. Image processing tasks included: 1) correction of image inhomogeneity caused by the coils, 2) segmentation of normal and abnormal tissue, and 3) modeling and visualization of the segmented tissue. The models were visualized using object-based surface rendering which revealed characteristics critical to differentiating benign from malignant tissue. Surface rendering illustrated the enhancement distribution and enhancement patterns. The modeling process condensed the multi-slice MRI data information and standardized its interpretation. Visualizing the 3D models should improve the radiologist's and/or surgeon's impression of the 3D shape, extent, and accessibility of the malignancy compared to viewing breast MRI data slice by slice.

Leader, J. Ken; Wang, Xiao Hui; Chang, Yuan-Hsiang; Chapman, Brian E.

2002-05-01

158

Navigation of a telepresence robot via covert visuospatial attention and real-time fMRI.  

PubMed

Brain-computer interfaces (BCIs) allow people with severe neurological impairment and without ability to control their muscles to regain some control over their environment. The BCI user performs a mental task to regulate brain activity, which is measured and translated into commands controlling some external device. We here show that healthy participants are capable of navigating a robot by covertly shifting their visuospatial attention. Covert Visuospatial Attention (COVISA) constitutes a very intuitive brain function for spatial navigation and does not depend on presented stimuli or on eye movements. Our robot is equipped with motors and a camera that sends visual feedback to the user who can navigate it from a remote location. We used an ultrahigh field MRI scanner (7 Tesla) to obtain fMRI signals that were decoded in real time using a support vector machine. Four healthy subjects with virtually no training succeeded in navigating the robot to at least three of four target locations. Our results thus show that with COVISA BCI, realtime robot navigation can be achieved. Since the magnitude of the fMRI signal has been shown to correlate well with the magnitude of spectral power changes in the gamma frequency band in signals measured by intracranial electrodes, the COVISA concept may in future translate to intracranial application in severely paralyzed people. PMID:22965825

Andersson, Patrik; Pluim, Josien P W; Viergever, Max A; Ramsey, Nick F

2013-01-01

159

Comparison of a 28 Channel-Receive Array Coil and Quadrature Volume Coil for Morphologic Imaging and T2 Mapping of Knee Cartilage at 7 Tesla  

PubMed Central

Purpose To compare a new birdcage-transmit, 28 channel-receive array (28 Ch) coil and a quadrature volume coil for 7 Tesla morphologic MRI and T2 mapping of knee cartilage. Methods The right knees of ten healthy subjects were imaged on a 7 Tesla whole body MR scanner using both coils. 3-dimensional fast low-angle shot (3D-FLASH) and multi-echo spin-echo (MESE) sequences were implemented. Cartilage signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), thickness, and T2 values were assessed. Results SNR/CNR was 17–400% greater for the 28 Ch compared to the quadrature coil (p?0.005). Bland-Altman plots show mean differences between measurements of tibial/femoral cartilage thickness and T2 values obtained with each coil to be small (?0.002±0.009 cm/0.003±0.011 cm) and large (?6.8±6.7 ms/?8.2±9.7 ms), respectively. For the 28 Ch coil, when parallel imaging with acceleration factors (AF) 2, 3, and 4 was performed, SNR retained was: 62–69%, 51–55%, and 39–45%. Conclusion A 28 Ch knee coil provides increased SNR/CNR for 7T cartilage morphologic imaging and T2 mapping. Coils should be switched with caution during clinical studies because T2 values may differ. The greater SNR of the 28 Ch coil could be used to perform parallel imaging with AF2 and obtain similar SNR as the quadrature coil.

Chang, Gregory; Wiggins, Graham C.; Xia, Ding; Lattanzi, Riccardo; Madelin, Guillaume; Raya, Jose G.; Finnerty, Matthew; Fujita, Hiroyuki; Recht, Michael P.; Regatte, Ravinder R.

2011-01-01

160

Tesla - A Flash of a Genius  

NASA Astrophysics Data System (ADS)

This book, which is entirely dedicated to the inventions of scientist Nikola Tesla, is divided into three parts: a) all the most important innovative technological creations from the alternate current to the death ray, Tesla research in fundamental physics with a particular attention to the concept of "ether", ball lightning physics; b) the life and the bright mind of Nikola Tesla and the reasons why some of his most recent findings were not accepted by the establishment; c) a critical discussion of the most important work by Tesla followers.

Teodorani, M.

2005-10-01

161

MRI-powered Actuators for Robotic Interventions  

PubMed Central

This paper presents a novel actuation technology for robotically assisted MRI-guided interventional procedures. Compact and wireless, the actuators are both powered and controlled by the MRI scanner. The design concept and performance limits are described and derived analytically. Simulation and experiments in a clinical MR scanner are used to validate the analysis and to demonstrate the capability of the approach for needle biopsies. The concepts of actuator locking mechanisms and multi-axis control are also introduced.

Vartholomeos, Panagiotis; Qin, Lei; Dupont, Pierre E.

2012-01-01

162

Scanner analyzer target  

NASA Astrophysics Data System (ADS)

This paper describes a black and white photographic chart called the 'Scanner Analyzer Target' developed as a practical aid toward analyzing scanned image quality produced by binary digital document scanners used as input devices in document image processing systems. The target is used by factory-line personnel as an 'adjustment-set' tool, by the quality control department as an image quality judgement tool, and by customers as an incoming inspection tool. The scanner uses a rotary drum paper transport to move the document in front of a fixed scan line. The document is illuminated by a pair of fluorescent lamps and reflected through a reduction type camera to a CCD image sensor. Scanning speeds range from 7 in./s to 12 in./s and scanning resolutions range from 200 to 300 dpi. The scanner control panel allows image quality adjustments by using 9 levels of darkness and 10 levels of sensitivity. The darkness setting controls the level of optical reflectance at which the scanner shifts its output from white to black. At low darkness setting a scanned image appears lighter than the original and at high darkness setting the resulting image is dark. The sensitivity setting controls the amount of adaptive thresholding included in the binary decision. Low sensitivity setting is adequate for high contrast originals; high sensitivity setting allows the scanner to detect low contrast information contained in different background shades (or colors). At maximum sensitivity, the scanner is extremely sensitive to high frequency (text) and tends to drop out the background information. The purpose of the target is to give the user the ability to measure a number of scanned image parameters: text legibility, resolution, focus, darkness range, shading distortion, sensitivity range, photograph dithering, vertical and horizontal pixel count, document or CCD skew, vertical resolution linearity, aspect ratio, video noise and page registration.

Simonis, Roland

1991-02-01

163

Liquid-explosives scanners stand trial in airports  

SciTech Connect

Air passengers may once more be allowed to pack beverages, lotions, and hair spray in their carry-on luggage, if imaging technologies to detect liquid explosives can prove their worth. Several competing systems, including multi-energy x-ray systems and a low-field magnetic resonance imaging (MRI) scanner, are undergoing field tests at some airports worldwide.

Matthews, Jermey N. A.

2010-07-15

164

Resting brain metabolic activity in a 4 tesla magnetic field.  

PubMed

MRI is a major tool for mapping brain function; thus it is important to assess potential effects on brain neuronal activity attributable to the requisite static magnetic field. This study used positron emission tomography (PET) and (18)F-deoxyglucose ((18)FDG) to measure brain glucose metabolism (a measure of brain function) in 12 subjects while their heads were in a 4 T MRI field during the (18)FDG uptake period. The results were compared with those obtained when the subjects were in the earth's field (PET scanner), and when they were in a simulated MRI environment in the PET instrument that imitated the restricted visual field of the MRI experiment. Whole-brain metabolism, as well as metabolism in occipital cortex and posterior cingulate gyrus, was lower in the real (4 T) and simulated (0 T) MRI environments compared with the PET. This suggests that the metabolic differences are due mainly to the visual field differences characteristic of the MRI and PET instruments. We conclude that a static magnetic field of 4 T does not in itself affect this fairly sensitive measure of brain activity. PMID:11064404

Volkow, N D; Wang, G J; Fowler, J S; Rooney, W D; Felder, C A; Lee, J H; Franceschi, D; Maynard, L; Schlyer, D J; Pan, J W; Gatley, S J; Springer Jr, C S

2000-11-01

165

Tesla - A Flash of a Genius  

Microsoft Academic Search

This book, which is entirely dedicated to the inventions of scientist Nikola Tesla, is divided into three parts: a) all the most important innovative technological creations from the alternate current to the death ray, Tesla research in fundamental physics with a particular attention to the concept of \\

M. Teodorani

2005-01-01

166

Omnipresence of Tesla's Work and Ideas  

Microsoft Academic Search

HIS paper discusses several examples of the continuing presence of Tesla's work in science, engineering, and other areas. We analyze papers and patents over an extensive period of time that cite directly Tesla's work and comment on his ideas. It is evident that the impact of some of his creations is still present in several research and industrial areas, attesting

Milos D. Ercegovac

167

Nikola Tesla: the man time forgot  

Microsoft Academic Search

The life and career of Nikola Tesla are described. His development of the AC motor and his battle with Thomas Edison over the use of AC versus DC (Edison was a proponent of the latter) are recounted. Experiments in which Tesla was far ahead of his time are described

J. I. Vuckovic

1990-01-01

168

Biochip scanner device  

DOEpatents

A biochip scanner device used to detect and acquire fluorescence signal data from biological microchips or biochips and method of use are provided. The biochip scanner device includes a laser for emitting a laser beam. A modulator, such as an optical chopper modulates the laser beam. A scanning head receives the modulated laser beam and a scanning mechanics coupled to the scanning head moves the scanning head relative to the biochip. An optical fiber delivers the modulated laser beam to the scanning head. The scanning head collects the fluorescence light from the biochip, launches it into the same optical fiber, which delivers the fluorescence into a photodetector, such as a photodiode. The biochip scanner device is used in a row scanning method to scan selected rows of the biochip with the laser beam size matching the size of the immobilization site.

Perov, Alexander (Troitsk, RU); Belgovskiy, Alexander I. (Mayfield Heights, OH); Mirzabekov, Andrei D. (Darien, IL)

2001-01-01

169

Portable biochip scanner device  

DOEpatents

A portable biochip scanner device used to detect and acquire fluorescence signal data from biological microchips (biochips) is provided. The portable biochip scanner device employs a laser for emitting an excitation beam. An optical fiber delivers the laser beam to a portable biochip scanner. A lens collimates the laser beam, the collimated laser beam is deflected by a dichroic mirror and focused by an objective lens onto a biochip. The fluorescence light from the biochip is collected and collimated by the objective lens. The fluorescence light is delivered to a photomultiplier tube (PMT) via an emission filter and a focusing lens. The focusing lens focuses the fluorescence light into a pinhole. A signal output of the PMT is processed and displayed.

Perov, Alexander (Troitsk, RU); Sharonov, Alexei (Moscow, RU); Mirzabekov, Andrei D. (Darien, IL)

2002-01-01

170

Evaluation of femoral head vascularization in slipped capital femoral epiphysis before and after cannulated screw fixation with use of contrast-enhanced MRI: initial results.  

PubMed

In this study we used contrast-enhanced magnetic resonance imaging (MRI) to evaluate the vascularization of the femoral head in children with slipped capital femoral epiphysis (SCFE) before and after cannulated screw fixation. Eleven consecutive children with SCFE, seven boys and four girls, aged 10-15 years were included in the study. There were no preslips; four children had acute, three acute-on-chronic, and four chronic SCFE. The MRI examinations were performed in a 1.5 Tesla MR scanner with use of a coronal STIR sequence, a coronal contrast-enhanced T1-weighted spin-echo sequence, and a sagittal three-dimensional gradient-echo sequence. Morphology, signal intensities, and contrast-enhancement of the femoral head were assessed by two radiologists in consensus. Morphologic distortion of the physis, bone marrow edema within the metaphysis and epiphysis, and joint effusion were the preoperative MRI findings of SCFE in each child. In nine children, the vascularization of the femoral head before and after surgery was normal. In one child, a preoperative avascular zone in the superolateral aspect of the epiphysis revascularized completely after surgery. One child with severe SCFE developed avascular necrosis of the femoral head after open reduction of the slip. We conclude that MRI allows for accurate evaluation of the femoral head vascularization before and after surgery in children with SCFE. PMID:16625344

Staatz, G; Honnef, D; Kochs, A; Hohl, C; Schmidt, T; Röhrig, H; Günther, R W

2007-01-01

171

Correlation of histological findings from a large ciliochoroidal melanoma with CT perfusion and 3T MRI dynamic enhancement studies  

PubMed Central

Background The initial use of a 64-slice computed tomography (CT) scanner for obtaining quantitative perfusion data from a large ciliochoroidal melanoma, and correlation with 3T magnetic resonance imaging (MRI) dynamic enhancement and tumor histology. Methods The CT perfusion scan was performed using 80 kVp, 250 mA and 1-sec rotation time for 40 sec. The analysis was performed using commercial perfusion analysis software with a prototype 3-dimensional motion correction tool. Dynamic contrast-enhanced 3-Tesla MRI measured the kinetics of enhancement to estimate the vascular permeability. The time-dependent enhancement patterns were obtained using the average signal intensity using Functool analysis software. The involved globe was enucleated and microscopic evaluation of the tumor was performed. Results The perfusion parameters blood flow, blood volume and permeability surface area product in the affected eye determined by CT perfusion analysis were 118 ml/100 ml/min, 11.3 ml/100 ml and 48 ml/100 ml/min. Dynamic MRI enhancement showed maximal intensity increase of 111%. The neoplasm was a ciliochoroidal spindle cell melanoma which was mitotically active (13 mitoses/40 hpf). Vascular loops and arcades were present throughout the tumor. The patient developed metastases within 9 months of presentation. Conclusion Quantitative CT perfusion analysis of ocular tumors is feasible with motion correction software.

Pulido, Jose S; Campeau, Norbert G; Klotz, Ernst; Primak, Andrew N; Saba, Osama; Gunduz, Kaan; Cantrill, Herbert; Salomao, Diva; McCollough, Cynthia H

2008-01-01

172

Hybrid Dispersion Laser Scanner  

NASA Astrophysics Data System (ADS)

Laser scanning technology is one of the most integral parts of today's scientific research, manufacturing, defense, and biomedicine. In many applications, high-speed scanning capability is essential for scanning a large area in a short time and multi-dimensional sensing of moving objects and dynamical processes with fine temporal resolution. Unfortunately, conventional laser scanners are often too slow, resulting in limited precision and utility. Here we present a new type of laser scanner that offers ~1,000 times higher scan rates than conventional state-of-the-art scanners. This method employs spatial dispersion of temporally stretched broadband optical pulses onto the target, enabling inertia-free laser scans at unprecedented scan rates of nearly 100 MHz at 800 nm. To show our scanner's broad utility, we use it to demonstrate unique and previously difficult-to-achieve capabilities in imaging, surface vibrometry, and flow cytometry at a record 2D raster scan rate of more than 100 kHz with 27,000 resolvable points.

Goda, K.; Mahjoubfar, A.; Wang, C.; Fard, A.; Adam, J.; Gossett, D. R.; Ayazi, A.; Sollier, E.; Malik, O.; Chen, E.; Liu, Y.; Brown, R.; Sarkhosh, N.; di Carlo, D.; Jalali, B.

2012-06-01

173

Lensless Image Scanner  

NASA Technical Reports Server (NTRS)

Image scanner uses moving and stationary parallel slits to produce pictures of visible, infrared, X-ray microwave, or acoustic sources. No lenses or mirrors required. Single detector views all parts of image simultaneously rather than raster making relatively-short exposure times possible. Potential applications of system include medical x-ray imaging.

Schindler, R. A.

1984-01-01

174

Hybrid Dispersion Laser Scanner  

PubMed Central

Laser scanning technology is one of the most integral parts of today's scientific research, manufacturing, defense, and biomedicine. In many applications, high-speed scanning capability is essential for scanning a large area in a short time and multi-dimensional sensing of moving objects and dynamical processes with fine temporal resolution. Unfortunately, conventional laser scanners are often too slow, resulting in limited precision and utility. Here we present a new type of laser scanner that offers ?1,000 times higher scan rates than conventional state-of-the-art scanners. This method employs spatial dispersion of temporally stretched broadband optical pulses onto the target, enabling inertia-free laser scans at unprecedented scan rates of nearly 100?MHz at 800?nm. To show our scanner's broad utility, we use it to demonstrate unique and previously difficult-to-achieve capabilities in imaging, surface vibrometry, and flow cytometry at a record 2D raster scan rate of more than 100?kHz with 27,000 resolvable points.

Goda, K.; Mahjoubfar, A.; Wang, C.; Fard, A.; Adam, J.; Gossett, D. R.; Ayazi, A.; Sollier, E.; Malik, O.; Chen, E.; Liu, Y.; Brown, R.; Sarkhosh, N.; Di Carlo, D.; Jalali, B.

2012-01-01

175

Hybrid dispersion laser scanner.  

PubMed

Laser scanning technology is one of the most integral parts of today's scientific research, manufacturing, defense, and biomedicine. In many applications, high-speed scanning capability is essential for scanning a large area in a short time and multi-dimensional sensing of moving objects and dynamical processes with fine temporal resolution. Unfortunately, conventional laser scanners are often too slow, resulting in limited precision and utility. Here we present a new type of laser scanner that offers ?1,000 times higher scan rates than conventional state-of-the-art scanners. This method employs spatial dispersion of temporally stretched broadband optical pulses onto the target, enabling inertia-free laser scans at unprecedented scan rates of nearly 100?MHz at 800?nm. To show our scanner's broad utility, we use it to demonstrate unique and previously difficult-to-achieve capabilities in imaging, surface vibrometry, and flow cytometry at a record 2D raster scan rate of more than 100?kHz with 27,000 resolvable points. PMID:22685627

Goda, K; Mahjoubfar, A; Wang, C; Fard, A; Adam, J; Gossett, D R; Ayazi, A; Sollier, E; Malik, O; Chen, E; Liu, Y; Brown, R; Sarkhosh, N; Di Carlo, D; Jalali, B

2012-01-01

176

What Scanner products are available?  

There are single satellite and combined-satellite scanner products. The best source for these data is to order the ERBE scanner CD which gives all the S4G monthly mean 2.5 degree gridded data from ...

2012-07-19

177

Head MRI  

MedlinePLUS

... the head; MRI - cranial; NMR - cranial; Cranial MRI; Brain MRI; MRI - brain; MRI - head ... tell your health care provider if you have: Brain aneurysm clips Certain types of artificial heart valves ...

178

The impact of Nikola Tesla on the cement industry  

Microsoft Academic Search

Nikola Tesla was perhaps the greatest inventor\\/engineer the world has known since the time of Leonardo da Vinci. Similar to da Vinci, Tesla's work was revolutionary, and Tesla's work was forgotten by the time his work was fully developed by others. Tesla was awarded the original patents that established the foundation for generating, delivering and utilizing the electricity used in

Jeffrey L. Sellon

1997-01-01

179

[Nikola Tesla: flashes of inspiration].  

PubMed

Nikola Tesla (1856-1943) was one of the greatest inventors in history and a key player in the revolution that led to the large-scale use of electricity. He also made important contributions to such diverse fields as x-rays, remote control, radio, the theory of consciousness or electromagnetism. In his honour, the international unit of magnetic induction was named after him. Yet, his fame is scarce in comparison with that of other inventors of the time, such as Edison, with whom he had several heated arguments. He was a rather odd, reserved person who lived for his inventions, the ideas for which came to him in moments of inspiration. In his autobiography he relates these flashes with a number of neuropsychiatric manifestations, which can be seen to include migraine auras, synaesthesiae, obsessions and compulsions. PMID:23307357

Villarejo-Galende, Albero; Herrero-San Martín, Alejandro

2013-01-16

180

Detection of Lactate with a Hadamard Slice Selected, Selective Multiple Quantum Coherence, Chemical Shift Imaging Sequence (HDMD-SelMQC-CSI) on a clinical MRI scanner: Application to Tumors and Muscle Ischemia  

PubMed Central

Lactate is an important metabolite in normal and malignant tissues detectable by NMR spectroscopy; however, it has been difficult to clinically detect the lactate methyl resonance because it is obscured by lipid resonances. The selective homonuclear multiple quantum coherence transfer (SelMQC) technique offers a method for distinguishing lipid and lactate resonances. We implemented a 3D SelMQC version with Hadamard slice selection and 2D phase encoding (HDMD-SelMQC-CSI) on a conventional clinical MR scanner. Hadamard slice selection is explained and demonstrated in vivo. This is followed by 1cm3 resolution lactate imaging with detection to 5 mM concentration in 20 minutes on a 3T clinical scanner. An analysis of quantum selection gradient duration and amplitude effects on lactate and lipid signal is presented. To demonstrate clinical feasibility, a 5 minute lactate scan of a patient with a non-Hodgkin's lymphoma in the superficial thigh is reported. The elevated lactate signal coincides with the T2-weighted image of this tumor. As a test of SelMQC sensitivity, a thigh tourniquet was applied to a normal volunteer and an increase in lactate was detected immediately after tourniquet flow constriction. In conclusion, the HDMD-SelMQC-CSI sequence is demonstrated on a phantom and in two lipid-rich, clinically relevant, in vivo conditions.

Mellon, Eric A.; Lee, Seung-Cheol; Pickup, Stephen; Kim, Sungheon; Goldstein, Steven C.; Floyd, Thomas F.; Poptani, Harish; Delikatny, E. James; Reddy, Ravinder; Glickson, Jerry D.

2010-01-01

181

Magnetic resonance electrical impedance tomography at 3 Tesla field strength.  

PubMed

Magnetic resonance electrical impedance tomography (MREIT) is a recently developed imaging technique that combines MRI and electrical impedance tomography (EIT). In MREIT, cross-sectional electrical conductivity images are reconstructed from the internal magnetic field density data produced inside an electrically conducting object when an electrical current is injected into the object. In this work we present the results of electrical conductivity imaging experiments, and performance evaluations of MREIT in terms of noise characteristics and spatial resolution. The MREIT experiment was performed with a 3.0 Tesla MRI system on a phantom with an inhomogeneous conductivity distribution. We reconstructed the conductivity images in a 128 x 128 matrix format by applying the harmonic B(z) algorithm to the z-component of the internal magnetic field density data. Since the harmonic B(z) algorithm uses only a single component of the internal magnetic field data, it was not necessary to rotate the object in the MRI scan. The root mean squared (RMS) errors of the reconstructed images were between 11% and 35% when the injection current was 24 mA. PMID:15170853

Oh, Suk H; Lee, Byung I; Park, Tae S; Lee, Soo Y; Woo, Eung J; Cho, Min H; Seo, Jin K; Kwon, Ohin

2004-06-01

182

Effects of image distortions originating from susceptibility variations and concomitant fields on diffusion MRI tractography results  

PubMed Central

In this work we investigate the effects of echo planar imaging (EPI) distortions on diffusion tensor imaging (DTI) based fiber tractography results. We propose a simple experimental framework that would enable assessing the effects of EPI distortions on the accuracy and reproducibility of fiber tractography from a pilot study on a few subjects. We compare trajectories computed from two diffusion datasets collected on each subject that are identical except for the orientation of phase encode direction, either right–left (RL) or anterior–posterior (AP). We define metrics to assess potential discrepancies between RL and AP trajectories in association, commissural, and projection pathways. Results from measurements on a 3 Tesla clinical scanner indicated that the effects of EPI distortions on computed fiber trajectories are statistically significant and large in magnitude, potentially leading to erroneous inferences about brain connectivity. The correction of EPI distortion using an image-based registration approach showed a significant improvement in tract consistency and accuracy. Although obtained in the context of a DTI experiment, our findings are generally applicable to all EPI-based diffusion MRI tractography investigations, including high angular resolution (HARDI) methods. On the basis of our findings, we recommend adding an EPI distortion correction step to the diffusion MRI processing pipeline if the output is to be used for fiber tractography.

Irfanoglu, M. Okan; Walker, Lindsay; Sarlls, Joelle; Marenco, Stefano; Pierpaoli, Carlo

2013-01-01

183

Effects of image distortions originating from susceptibility variations and concomitant fields on diffusion MRI tractography results.  

PubMed

In this work we investigate the effects of echo planar imaging (EPI) distortions on diffusion tensor imaging (DTI) based fiber tractography results. We propose a simple experimental framework that would enable assessing the effects of EPI distortions on the accuracy and reproducibility of fiber tractography from a pilot study on a few subjects. We compare trajectories computed from two diffusion datasets collected on each subject that are identical except for the orientation of phase encode direction, either right-left (RL) or anterior-posterior (AP). We define metrics to assess potential discrepancies between RL and AP trajectories in association, commissural, and projection pathways. Results from measurements on a 3 Tesla clinical scanner indicated that the effects of EPI distortions on computed fiber trajectories are statistically significant and large in magnitude, potentially leading to erroneous inferences about brain connectivity. The correction of EPI distortion using an image-based registration approach showed a significant improvement in tract consistency and accuracy. Although obtained in the context of a DTI experiment, our findings are generally applicable to all EPI-based diffusion MRI tractography investigations, including high angular resolution (HARDI) methods. On the basis of our findings, we recommend adding an EPI distortion correction step to the diffusion MRI processing pipeline if the output is to be used for fiber tractography. PMID:22401760

Irfanoglu, M Okan; Walker, Lindsay; Sarlls, Joelle; Marenco, Stefano; Pierpaoli, Carlo

2012-05-15

184

3-Tesla MRI Response to TACE in HCC (Liver Cancer)  

ClinicalTrials.gov

Adult Primary Hepatocellular Carcinoma; Advanced Adult Primary Liver Cancer; Localized Resectable Adult Primary Liver Cancer; Localized Unresectable Adult Primary Liver Cancer; Stage A Adult Primary Liver Cancer (BCLC); Stage B Adult Primary Liver Cancer (BCLC)

2014-03-20

185

High throughput optical scanner  

DOEpatents

A scanning apparatus is provided to obtain automated, rapid and sensitive scanning of substrate fluorescence, optical density or phosphorescence. The scanner uses a constant path length optical train, which enables the combination of a moving beam for high speed scanning with phase-sensitive detection for noise reduction, comprising a light source, a scanning mirror to receive light from the light source and sweep it across a steering mirror, a steering mirror to receive light from the scanning mirror and reflect it to the substrate, whereby it is swept across the substrate along a scan arc, and a photodetector to receive emitted or scattered light from the substrate, wherein the optical path length from the light source to the photodetector is substantially constant throughout the sweep across the substrate. The optical train can further include a waveguide or mirror to collect emitted or scattered light from the substrate and direct it to the photodetector. For phase-sensitive detection the light source is intensity modulated and the detector is connected to phase-sensitive detection electronics. A scanner using a substrate translator is also provided. For two dimensional imaging the substrate is translated in one dimension while the scanning mirror scans the beam in a second dimension. For a high throughput scanner, stacks of substrates are loaded onto a conveyor belt from a tray feeder.

Basiji, David A. (Seattle, WA); van den Engh, Gerrit J. (Seattle, WA)

2001-01-01

186

Synergistic enhancement of iron oxide nanoparticle and gadolinium for dual-contrast MRI  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer MR contrast agents exert influence on T{sub 1} or T{sub 2} relaxation time of the surrounding tissue. Black-Right-Pointing-Pointer Combined use of iron oxide and Gd-DTPA can improve the sensitivity/specificity of lesion detection. Black-Right-Pointing-Pointer Dual contrast MRI enhances the delineation of tumor borders and small lesions. Black-Right-Pointing-Pointer The effect of DC-MRI can come from the high paramagnetic susceptibility of Gd{sup 3+}. Black-Right-Pointing-Pointer The effect of DC-MRI can also come from the distinct pharmacokinetic distribution of SPIO and Gd-DTPA. -- Abstract: Purpose: The use of MR contrast agents allows accurate diagnosis by exerting an influence on the longitudinal (T{sub 1}) or transverse (T{sub 2}) relaxation time of the surrounding tissue. In this study, we combined the use of iron oxide (IO) particles and nonspecific extracellular gadolinium chelate (Gd) in order to further improve the sensitivity and specificity of lesion detection. Procedures: With a 7-Tesla scanner, pre-contrasted, IO-enhanced and dual contrast agent enhanced MRIs were performed in phantom, normal animals, and animal models of lymph node tumor metastases and orthotopic brain tumor. For the dual-contrast (DC) MRI, we focused on the evaluation of T{sub 2} weighted DC MRI with IO administered first, then followed by the injection of a bolus of gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). Results: Based on the C/N ratios and MRI relaxometry, the synergistic effect of coordinated administration of Gd-DTPA and IO was observed and confirmed in phantom, normal liver and tumor models. At 30 min after administration of Feridex, Gd-DTPA further decreased T{sub 2} relaxation in liver immediately after the injection. Additional administration of Gd-DTPA also immediately increased the signal contrast between tumor and brain parenchyma and maximized the C/N ratio to -4.12 {+-} 0.71. Dual contrast MRI also enhanced the delineation of tumor borders and small lesions. Conclusions: DC-MRI will be helpful to improve diagnostic accuracy and decrease the threshold size for lesion detection.

Zhang, Fan [Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health - NIH, Bethesda, MD 20892 (United States) [Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health - NIH, Bethesda, MD 20892 (United States); Center for Molecular Imaging and Translational Medicine, School of Public Health, Xiamen University, Xiamen 361005 (China); Huang, Xinglu [Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health - NIH, Bethesda, MD 20892 (United States)] [Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health - NIH, Bethesda, MD 20892 (United States); Qian, Chunqi [Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, MD 20892 (United States) [Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, MD 20892 (United States); Center for Molecular Imaging and Translational Medicine, School of Public Health, Xiamen University, Xiamen 361005 (China); Zhu, Lei [Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health - NIH, Bethesda, MD 20892 (United States) [Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health - NIH, Bethesda, MD 20892 (United States); Center for Molecular Imaging and Translational Medicine, School of Public Health, Xiamen University, Xiamen 361005 (China); Hida, Naoki [Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health - NIH, Bethesda, MD 20892 (United States)] [Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health - NIH, Bethesda, MD 20892 (United States); Niu, Gang, E-mail: niug@mail.nih.gov [Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health - NIH, Bethesda, MD 20892 (United States)] [Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health - NIH, Bethesda, MD 20892 (United States); Chen, Xiaoyuan, E-mail: shawn.chen@nih.gov [Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health - NIH, Bethesda, MD 20892 (United States)] [Laboratory of Molecular Imaging and Nanomedicine (LOMIN), National Institute of Biomedical Imaging and Bioengineering (NIBIB), National Institutes of Health - NIH, Bethesda, MD 20892 (United States)

2012-09-07

187

EEG-fMRI  

PubMed Central

Objective: In patients with nonlesional frontal lobe epilepsy (FLE), the delineation of the epileptogenic zone is difficult. Therefore these patients are often not considered for surgery due to an unclear seizure focus. The aim of this study was to investigate whether EEG-fMRI can add useful information in the preoperative evaluation of these patients. Methods: Nine nonlesional FLE patients were studied with EEG-fMRI using a 3 T scanner. Spike-related blood oxygen level dependent (BOLD) signal changes were compared to the topography of the spikes and to PET and SPECT results if available. The structural MRIs were reviewed for subtle abnormalities in areas that showed BOLD responses. For operated patients, postoperative resection and histology were compared to BOLD responses. Results: Concordance between spike localization and positive BOLD response was found in 8 patients. PET and SPECT investigations corresponded with BOLD signal changes in 6 of 7 investigations. In 2 cases, reviewing the structural MRI guided by EEG-fMRI data resulted in considering a suspicious deep sulcus. Two patients were operated. In 1, the resected cortex corresponded with the suspicious sulcus and fMRI results and histology showed cortical dysplasia. In another, histology revealed an extended microdysgenesis not visible on structural MRI. EEG-fMRI had shown activation just adjacent to the resected pathologic area. Conclusions: Our study provides different types of support (topography, concordance with PET and SPECT, structural peculiarities, postoperative histology) that EEG-fMRI may help to delineate the epileptic focus in patients with nonlesional frontal lobe epilepsy, a challenging group in the preoperative evaluation. GLOSSARY BOLD = blood oxygen level dependent; FLE = frontal lobe epilepsy; fMRI = functional MRI; HFR = hemodynamic response function; IED = interictal epileptiform discharges; TE = echo time; TR = repetition time.

Moeller, F; Tyvaert, L; Nguyen, D K.; LeVan, P; Bouthillier, A; Kobayashi, E; Tampieri, D; Dubeau, F; Gotman, J

2009-01-01

188

Issues and Design Solutions Associated with Performing MRI Scans on Patients with Active Implantable Medical Devices  

Microsoft Academic Search

Magnetic Resonance Imaging (MRI) has become one of medicine's most important diagnostic tools. However, due to patient safety concerns, MRI is contraindicated by both device and MRI equipment manufacturers for patients with active implanted medical devices (AIMDs). The primary concern is overheating of implanted leadwires due to currents induced from the powerful RF fields of the MRI scanner. In pacemaker

BOB STEVENSON; WARREN DABNEY; CHRISTINE FRYSZ

2007-01-01

189

MRI driven magnetic microswimmers  

PubMed Central

Capsule endoscopy is a promising technique for diagnosing diseases in the digestive system. Here we design and characterize a miniature swimming mechanism that uses the magnetic fields of the MRI for both propulsion and wireless powering of the capsule. Our method uses both the static and the radio frequency (RF) magnetic fields inherently available in MRI to generate a propulsive force. Our study focuses on the evaluation of the propulsive force for different swimming tails and experimental estimation of the parameters that influence its magnitude. We have found that an approximately 20 mm long, 5 mm wide swimming tail is capable of producing 0.21 mN propulsive force in water when driven by a 20 Hz signal providing 0.85 mW power and the tail located within the homogeneous field of a 3 T MRI scanner. We also analyze the parallel operation of the swimming mechanism and the scanner imaging. We characterize the size of artifacts caused by the propulsion system. We show that while the magnetic micro swimmer is propelling the capsule endoscope, the operator can locate the capsule on the image of an interventional scene without being obscured by significant artifacts. Although this swimming method does not scale down favorably, the high magnetic field of the MRI allows self propulsion speed on the order of several millimeter per second and can propel an endoscopic capsule in the stomach.

Jakab, Peter; Szekely, Gabor; Hata, Nobuhiko

2013-01-01

190

In vivo estimation of bone stiffness at the distal femur and proximal tibia using ultra-high-field 7-Tesla magnetic resonance imaging and micro-finite element analysis.  

PubMed

The goal of this study was to demonstrate the feasibility of using 7-Tesla (7T) magnetic resonance imaging (MRI) and micro-finite element analysis (µFEA) to evaluate mechanical and structural properties of whole, cortical, and trabecular bone at the distal femur and proximal tibia in vivo. 14 healthy subjects were recruited (age 40.7 ± 15.7 years). The right knee was scanned on a 7T MRI scanner using a 28 channel-receive knee coil and a three-dimensional fast low-angle shot sequence (TR/TE 20 ms/5.02 ms, 0.234 mm × 0.234 mm × 1 mm, 80 axial images, 7 min 9 s). Bone was analyzed at the distal femoral metaphysis, femoral condyles, and tibial plateau. Whole, cortical, and trabecular bone stiffness was computed using µFEA. Bone volume fraction (BVF), bone areas, and cortical thickness were measured. Trabecular bone stiffness (933.7 ± 433.3 MPa) was greater than cortical bone stiffness (216 ± 152 MPa) at all three locations (P < 0.05). Across locations, there were no differences in bone stiffness (whole, cortical, or trabecular). Whole, cortical, and trabecular bone stiffness correlated with BVF (R ? 0.69, P < 0.05) and inversely correlated with corresponding whole, cortical, and trabecular areas (R ? -0.54, P < 0.05), but not with cortical thickness (R < -0.11, P > 0.05). Whole, cortical, and trabecular stiffness correlated with body mass index (R ? 0.62, P < 0.05). In conclusion, at the distal femur and proximal tibia, trabecular bone contributes 66-74% of whole bone stiffness. 7T MRI and µFEA may be used as a method to provide insight into how structural properties of cortical or trabecular bone affect bone mechanical competence in vivo. PMID:22124539

Chang, Gregory; Rajapakse, Chamith S; Babb, James S; Honig, Stephen P; Recht, Michael P; Regatte, Ravinder R

2012-03-01

191

In vivo estimation of bone stiffness at the distal femur and proximal tibia using ultra-high-field 7-Tesla magnetic resonance imaging and micro-finite element analysis  

PubMed Central

The goal of this study was to demonstrate the feasibility of using 7-Tesla (7T) magnetic resonance imaging (MRI) and micro-finite element analysis (?FEA) to evaluate mechanical and structural properties of whole, cortical, and trabecular bone at the distal femur and proximal tibia in vivo. 14 healthy subjects were recruited (age 40.7 ± 15.7 years). The right knee was scanned on a 7T MRI scanner using a 28 channel-receive knee coil and a three-dimensional fast low-angle shot sequence (TR/TE 20 ms/5.02 ms, 0.234 mm × 0.234 mm × 1 mm, 80 axial images, 7 min 9 s). Bone was analyzed at the distal femoral metaphysis, femoral condyles, and tibial plateau. Whole, cortical, and trabecular bone stiffness was computed using ?FEA. Bone volume fraction (BVF), bone areas, and cortical thickness were measured. Trabecular bone stiffness (933.7 ± 433.3 MPa) was greater than cortical bone stiffness (216 ± 152 MPa) at all three locations (P < 0.05). Across locations, there were no differences in bone stiffness (whole, cortical, or trabecular). Whole, cortical, and trabecular bone stiffness correlated with BVF (R ? 0.69, P < 0.05) and inversely correlated with corresponding whole, cortical, and trabecular areas (R ? ?0.54, P < 0.05), but not with cortical thickness (R < ?0.11, P > 0.05). Whole, cortical, and trabecular stiffness correlated with body mass index (R ? 0.62, P < 0.05). In conclusion, at the distal femur and proximal tibia, trabecular bone contributes 66–74% of whole bone stiffness. 7T MRI and ?FEA may be used as a method to provide insight into how structural properties of cortical or trabecular bone affect bone mechanical competence in vivo.

Rajapakse, Chamith S.; Babb, James S.; Honig, Stephen P.; Recht, Michael P.; Regatte, Ravinder R.

2013-01-01

192

GM2 gangliosidosis (Sandhoff's disease): two year follow-up by MRI  

Microsoft Academic Search

Two children with GM-2 gangliosidosis type 0 (Sandhoff's disease) followed up by MRI at 1.5 Tesla for 1.8 years are reported. One was presymptomatic at the first MRI examination. As her neurological status deteriorated, MRI showed low signal in bilaterally, on T2-weighted images the white matter with involvement of the optic radiations. In the second, MRI correlated well with the

W. Koelfen; M. Freund; W. Jaschke; S. Koenig; C. Schultze

1994-01-01

193

FMRI scanner noise interaction with affective neural processes.  

PubMed

The purpose of the present study was the investigation of interaction effects between functional MRI scanner noise and affective neural processes. Stimuli comprised of psychoacoustically balanced musical pieces, expressing three different emotions (fear, neutral, joy). Participants (N=34, 19 female) were split into two groups, one subjected to continuous scanning and another subjected to sparse temporal scanning that features decreased scanner noise. Tests for interaction effects between scanning group (sparse/quieter vs continuous/noisier) and emotion (fear, neutral, joy) were performed. Results revealed interactions between the affective expression of stimuli and scanning group localized in bilateral auditory cortex, insula and visual cortex (calcarine sulcus). Post-hoc comparisons revealed that during sparse scanning, but not during continuous scanning, BOLD signals were significantly stronger for joy than for fear, as well as stronger for fear than for neutral in bilateral auditory cortex. During continuous scanning, but not during sparse scanning, BOLD signals were significantly stronger for joy than for neutral in the left auditory cortex and for joy than for fear in the calcarine sulcus. To the authors' knowledge, this is the first study to show a statistical interaction effect between scanner noise and affective processes and extends evidence suggesting scanner noise to be an important factor in functional MRI research that can affect and distort affective brain processes. PMID:24260420

Skouras, Stavros; Gray, Marcus; Critchley, Hugo; Koelsch, Stefan

2013-01-01

194

MRI distortion: considerations for MRI based radiotherapy treatment planning.  

PubMed

Distortion in magnetic resonance images needs to be taken into account for the purposes of radiotherapy treatment planning (RTP). A commercial MRI grid phantom was scanned on four different MRI scanners with multiple sequences to assess variations in the geometric distortion. The distortions present across the field of view were then determined. The effect of varying bandwidth on image distortion and signal to noise was also investigated. Distortion maps were created and these were compared to the location of patient anatomy within the scanner bore to estimate the magnitude and distribution of distortions located within specific clinical regions. Distortion magnitude and patterns varied between MRI sequence protocols and scanners. The magnitude of the distortions increased with increasing distance from the isocentre of the scanner within a 2D imaging plane. Average distortion across the phantom generally remained below 2.0 mm, although towards the edge of the phantom for a turbo spin echo sequence, the distortion increased to a maximum value of 4.1 mm. Application of correction algorithms supplied by each vendor reduced but did not completely remove distortions. Increasing the bandwidth of the acquisition sequence decreased the amount of distortion at the expense of a reduction in signal-to-noise ratio of 13.5 across measured bandwidths. Imaging protocol parameters including bandwidth, slice thickness and phase encoding direction, should be noted for distortion investigations in RTP since each can influence the distortion. The magnitude of distortion varies across different clinical sites. PMID:24519001

Walker, Amy; Liney, Gary; Metcalfe, Peter; Holloway, Lois

2014-03-01

195

Science up to 100 tesla  

SciTech Connect

100 Tesla is the highest attainable field that can be held for milli-sec in a non-destructive magnet. The strongest steels turn soft under stresses of 4GPa, which is the magnetic pressure of 100 T. Until there is a breakthrough in materials, magnets having all the low temperature and high pressure trimmings will be limited to about 100 T. Within the field range 1-100 T far more resources are now devoted to producing the highest possible continuous fields (40+5 T) than to producing longer pulsed fields above 50 T. This illustrates that the utility of the field can be more important than the strength of the field to researchers in condensed matter. Discoveries are typically made in new territory, but this can be new combinations of pressure, temperature, and magnetic field, or new probes and new materials. If any activity has kept up with the proliferation of new experiments and new facilities in high magnetic field research it is the listing of experiments that could and should be done in high fields. Part of the reason for the vitality of high field research is that high fields provide a generic environment. Compared to particle accelerators and plasma machines a high field laboratory is a setting for generic science, like synchrotron light sources or neutron scattering centers. Although the latter two installations probes states, while a magnetic field creates a state. Because it is unrealistic to try to list all the science opportunities at high fields, the author list sources for lists in the public domain and gives a few examples.

Campbell, L.J. [Los Alamos National Lab., NM (United States). National High Magnetic Field Lab.

1995-05-01

196

Design and scaling of microscale Tesla turbines  

NASA Astrophysics Data System (ADS)

We report on the scaling properties and loss mechanisms of Tesla turbines and provide design recommendations for scaling such turbines to the millimeter scale. Specifically, we provide design, fabrication and experimental data for a low-pressure head hydro Tesla micro-turbine. We derive the analytical turbine performance for incompressible flow and then develop a more detailed model that predicts experimental performance by including a variety of loss mechanisms. We report the correlation between them and the experimental results. Turbines with 1 cm rotors, 36% peak efficiency (at 2 cm3 s-1 flow) and 45 mW unloaded peak power (at 12 cm3 s-1 flow) are demonstrated. We analyze the causes for head loss and shaft power loss and derive constraints on turbine design. We then analyze the effect of scaling down on turbine efficiency, power density and rotor revolutions/min. Based on the analysis, we make recommendations for the design of ˜1 mm microscale Tesla turbines.

Krishnan, Vedavalli G.; Romanin, Vince; Carey, Van P.; Maharbiz, Michel M.

2013-12-01

197

MRI artefacts after Bonebridge implantation.  

PubMed

The new transcutaneous bone conduction implant (BCI) Bonebridge (BB, MED-EL) allows the skin to remain intact and therefore overcomes some issues related to percutaneous systems, such as skin reaction around the external screw and cosmetic complaints. According to manufacturer, BB is MRI conditional up to 1,5 Tesla (T). The artefact of the neurocranium after BB implantation is extensive as shown in the present report. This has to be taken into account when patients suffering conductive, mixed or single-sided hearing loss with candidacy for a BCI are counselled. In patients with comorbid intracranial tumour or other diseases of the brain that require imaging control scans with MRI percutaneous, BCI should be the implant of choice considering the very small artefact of the percutaneous screw in MRI. PMID:24639341

Steinmetz, C; Mader, I; Arndt, S; Aschendorff, A; Laszig, R; Hassepass, F

2014-07-01

198

21 CFR 892.1220 - Fluorescent scanner.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Fluorescent scanner. 892.1220 Section 892.1220 Food...Diagnostic Devices § 892.1220 Fluorescent scanner. (a) Identification. A fluorescent scanner is a device intended to measure...

2009-04-01

199

21 CFR 892.1220 - Fluorescent scanner.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Fluorescent scanner. 892.1220 Section 892.1220 Food...Diagnostic Devices § 892.1220 Fluorescent scanner. (a) Identification. A fluorescent scanner is a device intended to measure...

2010-04-01

200

Laser Scanner Demonstration  

SciTech Connect

In the Summer of 2004 a request for proposals went out to potential vendors to offer a three-dimensional laser scanner for a number of unique metrology tasks at the Stanford Linear Accelerator Center (SLAC). Specifications were established including range, accuracy, scan density, resolution and field of view in consideration of anticipated department requirements. Four vendors visited the site to present their system and they were asked to perform three unique tests with their system on a two day visit to SLAC. Two of the three tests were created to emulate real-world applications at SLAC while the third was an accuracy and resolution series of experiments. The scope of these tests is presented and some of the vendor's results are included.

Fuss, B.

2005-09-06

201

Cerebral Activation During the Test of Spinal Cord Injury Severity in Children: an fMRI Methodological Study  

PubMed Central

Background: The International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) are internationally accepted to determine and classify the extent of motor and sensory impairment along with severity (ASIA Impairment Scale [AIS]) following spinal cord injury (SCI). The anorectal examination is a component of the ISNCSCI that determines injury severity. There is a void in the health care literature on the validity of the anorectal examination as an indication of SCI severity. Objective: To validate the use of functional magnetic resonance imagining (fMRI) for the purpose of classifying the severity of SCI in children. Methods: Seventeen patients, with the average age of 14.3 years, underwent 1 complete ISNCSCI examination. Subjects also underwent the anorectal portion of this exam while fMRI data were collected using a 3.0 Tesla Siemens Verio Scanner. Cortical areas of activation were analyzed for possible differences of cortical involvement between complete (AIS A) and incomplete (AIS B, C, and D) SCI subjects. Anxiety/anticipation of the test was also assessed. Results: This study established an fMRI imaging protocol that captures the cortical locations and intensity of activation during the test of sacral sparing. In addition to developing the data acquisition protocol, we also established the postacquisition preprocessing and statistical analysis parameters using SPM8. Conclusion: Preliminary findings indicate that fMRI is a useful tool in evaluating the validity of the anorectal examination in determining SCI severity. Assessment of which cortical regions are activated during the testing procedure provides an indication of which pathways are transmitting information to the brain.

2013-01-01

202

Decreased Retinal-Choroidal Blood Flow in Retinitis Pigmentosa as measured by MRI  

PubMed Central

Purpose To evaluate retinal and choroidal blood flow (BF) using high-resolution magnetic resonance imaging (MRI) as well as visual function measured by the electroretinogram (ERG) in patients with retinitis pigmentosa (RP). Methods MRI studies were performed in 6 RP patients (29-67 years) and 5 healthy volunteers (29-64 years) on a 3-Tesla scanner with a custom-made surface coil. Quantitative BF was measured using the pseudo-continuous arterial-spin-labeling technique at 0.5x0.8x6.0mm. Full-field ERGs of all patients were recorded. Amplitudes and implicit times of standard ERGs were analyzed. Results Basal BF in the posterior retinal-choroid was 142±16 ml/100ml/min (or 1.14±0.13 ?l/mm2/min) in the control group and was 70±19 ml/100ml/min (or 0.56±0.15 ?l/mm2/min) in the RP group. Retinal-choroidal BF was significantly reduced by 52±8% in RP patients compared to controls (P<0.05). ERG a- and b-wave amplitudes of RP patients were reduced and b-wave implicit times were delayed. There were statistically significant correlations between a-wave amplitude and BF value (r=0.9, P<0.05) but not between b-wave amplitude and BF value (r =0.7, P=0.2). Conclusions This study demonstrates a novel non-invasive MRI approach to measure quantitative retinal and choroidal BF in RP patients. We found that retinal-choroidal BF was markedly reduced and significantly correlated with reduced amplitudes of the a-wave of the standard combined ERG.

Zhang, Yi; Harrison, Joseph M; Nateras, Oscar San Emeterio; Chalfin, Steven; Duong, Timothy Q

2013-01-01

203

Subfields of the hippocampal formation at 7 T MRI: in vivo volumetric assessment.  

PubMed

Animal and human autopsy studies suggest that subfields of the hippocampal formation are differentially affected by neuropsychiatric diseases. Therefore, subfield volumes may be more sensitive to effects of disease processes. The few human studies that segmented subfields of the hippocampal formation in vivo either assessed the subfields only in the body of the hippocampus, assessed only three subfields, or did not take the differential angulation of the head of the hippocampus into account. We developed a protocol using 7 Tesla MRI with isotropic voxels to reliably delineate the entorhinal cortex (ERC), subiculum (SUB), CA1, CA2, CA3, dentate gyrus (DG)&CA4 along the full-length of the hippocampus. Fourteen subjects (aged 54-74 years, 2 men and 12 women) were scanned with a 3D turbo spin echo (TSE) sequence with isotropic voxels of 0.7 × 0.7 × 0.7 mm(3) on a 7 T MRI whole body scanner. Based on previous protocols and extensive anatomic atlases, a new protocol for segmentation of subfields of the hippocampal formation was formulated. ERC, SUB, CA1, CA2, CA3 and DG&CA4 were manually segmented twice by one rater from coronal MR images. Good-to-excellent consistency was found for all subfields (Intraclass Correlation Coefficient's (ICC) varying from 0.74 to 0.98). Accuracy as measured with the Dice Similarity Index (DSI) was above 0.82 for all subfields, with the exception of the smaller subfield CA3 (0.68-0.70). In conclusion, this study shows that it is possible to delineate the main subfields of the hippocampal formation along its full-length in vivo at 7 T MRI. Our data give evidence that this can be done in a reliable manner. Segmentation of subfields in the full-length of the hippocampus may bolster the study of the etiology neuropsychiatric diseases. PMID:22440643

Wisse, L E M; Gerritsen, L; Zwanenburg, J J M; Kuijf, H J; Luijten, P R; Biessels, G J; Geerlings, M I

2012-07-16

204

Abnormal activation of the motor cortical network in idiopathic scoliosis demonstrated by functional MRI.  

PubMed

The aetiology of idiopathic scoliosis (IS) remains unknown, but there is growing support for the possibility of an underlying neurological disorder. Functional magnetic resonance imaging (fMRI) can characterize the abnormal activation of the sensorimotor brain network in movement disorders and could provide further insights into the neuropathogenesis of IS. Twenty subjects were included in the study; 10 adolescents with IS (mean age of 15.2, 8 girls and 2 boys) and 10 age-matched healthy controls. The average Cobb angle of the primary curve in the IS patients was 35° (range 27°-55°). All participants underwent a block-design fMRI experiment in a 1.5-Tesla MRI scanner to explore cortical activation following a simple motor task. Rest periods alternated with activation periods during which participants were required to open and close their hand at an internally paced rate of approximately 1 Hz. Data were analyzed with Statistical Parametric Mapping (SPM5) including age, sex and laterality as nuisance variables to minimise the presence of bias in the results. Compared to controls, IS patients showed significant increases in blood oxygenation level dependent (BOLD) activity in contralateral supplementary motor area when performing the motor task with either hand. No significant differences were observed when testing between groups in the functional activation in the primary motor cortex, premotor cortex and somatosensory cortex. Additionally, the IS group showed a greater interhemispheric asymmetry index than the control group (0.30 vs. 0.13, p < 0.001). This study demonstrates an abnormal pattern of brain activation in secondary motor areas during movement execution in patients with IS. These findings support the hypothesis that a sensorimotor integration disorder underlies the pathogenesis of IS. PMID:21499781

Domenech, Julio; García-Martí, G; Martí-Bonmatí, L; Barrios, C; Tormos, J M; Pascual-Leone, A

2011-07-01

205

Multiple single-point imaging (mSPI) as a tool for capturing and characterizing MR signals and repetitive signal disturbances with high temporal resolution: the MRI scanner as a high-speed camera.  

PubMed

In this paper we aim to lay down and demonstrate the use of multiple single-point imaging (mSPI) as a tool for capturing and characterizing steady-state MR signals and repetitive disturbances thereof with high temporal resolution. To achieve this goal, various 2D mSPI sequences were derived from the nearest standard 3D imaging sequences by (i) replacing the excitation of a 3D slab by the excitation of a 2D slice orthogonal to the read axis, (ii) setting the readout gradient to zero, and (iii) leaving out the inverse Fourier transform in the read direction. The thus created mSPI sequences, albeit slow with regard to the spatial encoding part, were shown to result into a series of densely spaced 2D single-point images in the time domain enabling monitoring of the evolution of the magnetization with a high temporal resolution and without interference from any encoding gradients. The high-speed capabilities of mSPI were demonstrated by capturing and characterizing the free induction decays and spin echoes of substances with long T2s (>30 ms) and long and short T2*s (4 - >30 ms) and by monitoring the perturbation of the transverse magnetization by, respectively, a titanium cylinder, representing a static disturbance; a pulsed magnetic field gradient, representing a stimulus inherent to a conventional MRI experiment; and a pulsed electric current, representing an external stimulus. The results of the study indicate the potential of mSPI for assessing the evolution of the magnetization and, when properly synchronized with the acquisition, repeatable disturbances thereof with a temporal resolution that is ultimately limited by the bandwidth of the receiver, but in practice governed by the SNR of the experiment and the magnitude of the disturbance. Potential applications of mSPI can be envisaged in research areas that are concerned with MR signal behavior, MR system performance and MR evaluation of magnetically evoked responses. PMID:23759651

Bakker, Chris J G; van Gorp, Jetse S; Verwoerd, Jan L; Westra, Albert H; Bouwman, Job G; Zijlstra, Frank; Seevinck, Peter R

2013-09-01

206

MIT 12 Tesla Coil test results  

Microsoft Academic Search

Test results from the MIT 12 Tesla Coil experiment are presented. The coil was tested in the High Field Test Facility (HFTF) of the Lawrence Livermore National Laboratory in October 1984 and January 1985. The experiment measured the performance of an Internally Cooled, Cabled Superconductor (ICCS) of practical size, intended for use in magnetic fusion experiments. The MIT coil carried

M. M. Steeves; M. O. Hoenig

1985-01-01

207

Side scanner for supermarkets: a new scanner design standard  

NASA Astrophysics Data System (ADS)

High speed UPC bar code has become a standard mode of data capture for supermarkets in the US, Europe, and Japan. The influence of the ergonomics community on the design of the scanner is evident. During the past decade the ergonomic issues of cashier in check-outs has led to occupational hand-wrist cumulative trauma disorders, in most cases causing carpal tunnel syndrome, a permanent hand injury. In this paper, the design of a side scanner to resolve the issues is discussed. The complex optical module and the sensor for aforesaid side scanner is described. The ergonomic advantages offer the old counter mounted vertical scanner has been experimentally proved by the industrial funded study at an independent university.

Cheng, Charles K.; Cheng, J. K.

1996-09-01

208

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

PubMed Central

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

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

2009-01-01

209

[Recent advances in newborn MRI].  

PubMed

The accurate morphological exploration of the brain is a major challenge in neonatology that advances in magnetic resonance imaging (MRI) can now provide. MRI is the gold standard if an hypoxic ischemic pathology is suspected in a full term neonate. In prematures, the specific role of MRI remains to be defined, secondary to US in any case. We present a state of the art of hardware and software technical developments in MRI. The increase in magnetic field strength (3 tesla) and the emergence of new MRI sequences provide access to new information. They both have positive and negative consequences on the daily clinical data acquisition use. The semiology of brain imaging in full term newborns and prematures is more extensive and complex and thereby more difficult to interpret. The segmentation of different brain structures in the newborn, even very premature, is now available. It is now possible to dissociate the cortex and basal ganglia from the cerebral white matter, to calculate the volume of anatomical structures, which improves the morphometric quantification and the understanding of the normal and abnormal brain development. MRI is a powerful tool to analyze the neonatal brain. The relevance of the diagnostic contribution requires an adaptation of the parameters of the sequences to acquire and of the image processing methods. PMID:24837857

Morel, B; Hornoy, P; Husson, B; Bloch, I; Adamsbaum, C

2014-07-01

210

Chest MRI  

MedlinePLUS

... from the NHLBI on Twitter. What Is Chest MRI? Chest MRI (magnetic resonance imaging) is a safe, noninvasive test. "Noninvasive" means that ... your chest wall, heart, and blood vessels. Chest MRI uses radio waves, magnets, and a computer to ...

211

Cardiac MRI  

MedlinePLUS

... from the NHLBI on Twitter. What Is Cardiac MRI? Magnetic resonance imaging (MRI) is a safe, noninvasive test that creates detailed ... and no instruments are inserted into your body. MRI uses radio waves, magnets, and a computer to ...

212

A multi-scanner study of subcortical brain volume abnormalities in schizophrenia.  

PubMed

Schizophrenia patients show significant subcortical brain abnormalities. We examined these abnormalities using automated image analysis software and provide effect size estimates for prospective multi-scanner schizophrenia studies. Subcortical and intracranial volumes were obtained using FreeSurfer 5.0.0 from high-resolution structural imaging scans from 186 schizophrenia patients (mean age±S.D.=38.9±11.6, 78% males) and 176 demographically similar controls (mean age±S.D.=37.5±11.2, 72% males). Scans were acquired from seven 3-Tesla scanners. Univariate mixed model regression analyses compared between-group volume differences. Weighted mean effect sizes (and number of subjects needed for 80% power at ?=0.05) were computed based on the individual single site studies as well as on the overall multi-site study. Schizophrenia patients have significantly smaller intracranial, amygdala, and hippocampus volumes and larger lateral ventricle, putamen and pallidum volumes compared with healthy volunteers. Weighted mean effect sizes based on single site studies were generally larger than effect sizes computed based on analysis of the overall multi-site sample. Prospectively collected structural imaging data can be combined across sites to increase statistical power for meaningful group comparisons. Even when using similar scan protocols at each scanner, some between-site variance remains. The multi-scanner effect sizes provided by this study should help in the design of future multi-scanner schizophrenia imaging studies. PMID:24650452

van Erp, Theo G M; Greve, Douglas N; Rasmussen, Jerod; Turner, Jessica; Calhoun, Vince D; Young, Sarah; Mueller, Bryon; Brown, Gregory G; McCarthy, Gregory; Glover, Gary H; Lim, Kelvin O; Bustillo, Juan R; Belger, Aysenil; McEwen, Sarah; Voyvodic, James; Mathalon, Daniel H; Keator, David; Preda, Adrian; Nguyen, Dana; Ford, Judith M; Potkin, Steven G; Fbirn

2014-04-30

213

Impairment of chondrocyte biosynthetic activity by exposure to 3-tesla high-field magnetic resonance imaging is temporary  

PubMed Central

The influence of magnetic resonance imaging (MRI) devices at high field strengths on living tissues is unknown. We investigated the effects of a 3-tesla electromagnetic field (EMF) on the biosynthetic activity of bovine articular cartilage. Bovine articular cartilage was obtained from juvenile and adult animals. Whole joints or cartilage explants were subjected to a pulsed 3-tesla EMF; controls were left unexposed. Synthesis of sulfated glycosaminoglycans (sGAGs) was measured by using [35S]sulfate incorporation; mRNA encoding the cartilage markers aggrecan and type II collagen, as well as IL-1?, were analyzed by RT–PCR. Furthermore, effects of the 3-tesla EMF were determined over the course of time directly after exposure (day 0) and at days 3 and 6. In addition, the influence of a 1.5-tesla EMF on cartilage sGAG synthesis was evaluated. Chondrocyte cell death was assessed by staining with Annexin V and TdT-mediated dUTP nick end labelling (TUNEL). Exposure to the EMF resulted in a significant decrease in cartilage macromolecule synthesis. Gene expression of both aggrecan and IL-1?, but not of collagen type II, was reduced in comparison with controls. Staining with Annexin V and TUNEL revealed no evidence of cell death. Interestingly, chondrocytes regained their biosynthetic activity within 3 days after exposure, as shown by proteoglycan synthesis rate and mRNA expression levels. Cartilage samples exposed to a 1.5-tesla EMF remained unaffected. Although MRI devices with a field strength of more than 1.5 T provide a better signal-to-noise ratio and thereby higher spatial resolution, their high field strength impairs the biosynthetic activity of articular chondrocytes in vitro. Although this decrease in biosynthetic activity seems to be transient, articular cartilage exposed to high-energy EMF may become vulnerable to damage.

Sunk, Ilse-Gerlinde; Trattnig, Siegfried; Graninger, Winfried B; Amoyo, Love; Tuerk, Birgit; Steiner, Carl-Walter; Smolen, Josef S; Bobacz, Klaus

2006-01-01

214

MSS D Multispectral Scanner System  

NASA Technical Reports Server (NTRS)

The development and acceptance testing of the 4-band Multispectral Scanners to be flown on LANDSAT D and LANDSAT D Earth resources satellites are summarized. Emphasis is placed on the acceptance test phase of the program. Test history and acceptance test algorithms are discussed. Trend data of all the key performance parameters are included and discussed separately for each of the two multispectral scanner instruments. Anomalies encountered and their resolutions are included.

Lauletta, A. M.; Johnson, R. L.; Brinkman, K. L. (principal investigators)

1982-01-01

215

Micromachined Optical Scanner for Optical Measurement System  

Microsoft Academic Search

We have designed, fabricated, and evaluated a micromachined optical scanner intended for optical measurement systems. It consists of a micromachined Si resonator, a Si spacer and a permalloy piece for electromagnetic actuation. An FEM-based simulator was used to design both a scanner structure and a magnetic circuit. We replaced a tuning fork scanner with the micromachined scanner in a commercial

Yoshifumi Takahashi; Yuji Takeuchi; Hiroyuki Fujita

2003-01-01

216

Temperature mapping for ultrasound scanner using backscattered changes  

NASA Astrophysics Data System (ADS)

MRI and ultrasound scanner are the two main methods used to guide thermal ablation. The superiority of MRI over ultrasound scanner comes from its ability to provide temperature mapping during thermal ablation. This paper describes the relationship between the changes in ultrasound backscattering and the temperature changes during HIFU treatments. Data was acquired during a 120s total treatment time with a duty cycle of 90% (1s HIFU on followed by a 0.1s ultrasound scanner acquisition). A thermocouple was placed at the focal point of the ablated area for correlation measurements. Twenty-three ablations were performed in in vitro livers. An increase in ultrasound backscattering as the tissue temperature increase was noted and correlates well with thermocouple measurements. Radiofrequency signals were used to estimate ultrasound backscattering changes in real-time. A linear relationship between changes in the radiofrequency signal and temperature was observed up to 90°C. These temperature measurements also correlate with the dimensions of ablations produced. This report describes the basics of processing that may be used to provide essential feedback to operators of the state of the tissue during treatment.

Chenot, Jérémy; Melodelima, David; Chapelon, Jean-Yves

2012-10-01

217

A multichannel, real-time MRI RF power monitor for independent SAR determination  

PubMed Central

Purpose: Accurate measurements of the RF power delivered during clinical MRI are essential for safety and regulatory compliance, avoiding inappropriate restrictions on clinical MRI sequences, and for testing the MRI safety of peripheral and interventional devices at known RF exposure levels. The goal is to make independent RF power measurements to test the accuracy of scanner-reported specific absorption rate (SAR) over the extraordinary range of operating conditions routinely encountered in MRI. Methods: A six channel, high dynamic range, real-time power profiling system was designed and built for monitoring power delivery during MRI up to 440 MHz. The system was calibrated and used in two 3 T scanners to measure power applied to human subjects during MRI scans. The results were compared with the scanner-reported SAR. Results: The new power measurement system has highly linear performance over a 90 dB dynamic range and a wide range of MRI duty cycles. It has about 0.1 dB insertion loss that does not interfere with scanner operation. The measurements of whole-body SAR in volunteers showed that scanner-reported SAR was significantly overestimated by up to about 2.2 fold. Conclusions: The new power monitor system can accurately and independently measure RF power deposition over the wide range of conditions routinely encountered during MRI. Scanner-reported SAR values are not appropriate for setting exposure limits during device or pulse sequence testing.

El-Sharkawy, AbdEl-Monem M.; Qian, Di; Bottomley, Paul A.; Edelstein, William A.

2012-01-01

218

A multichannel, real-time MRI RF power monitor for independent SAR determination  

SciTech Connect

Purpose: Accurate measurements of the RF power delivered during clinical MRI are essential for safety and regulatory compliance, avoiding inappropriate restrictions on clinical MRI sequences, and for testing the MRI safety of peripheral and interventional devices at known RF exposure levels. The goal is to make independent RF power measurements to test the accuracy of scanner-reported specific absorption rate (SAR) over the extraordinary range of operating conditions routinely encountered in MRI. Methods: A six channel, high dynamic range, real-time power profiling system was designed and built for monitoring power delivery during MRI up to 440 MHz. The system was calibrated and used in two 3 T scanners to measure power applied to human subjects during MRI scans. The results were compared with the scanner-reported SAR. Results: The new power measurement system has highly linear performance over a 90 dB dynamic range and a wide range of MRI duty cycles. It has about 0.1 dB insertion loss that does not interfere with scanner operation. The measurements of whole-body SAR in volunteers showed that scanner-reported SAR was significantly overestimated by up to about 2.2 fold. Conclusions: The new power monitor system can accurately and independently measure RF power deposition over the wide range of conditions routinely encountered during MRI. Scanner-reported SAR values are not appropriate for setting exposure limits during device or pulse sequence testing.

El-Sharkawy, AbdEl-Monem M.; Qian Di; Bottomley, Paul A.; Edelstein, William A. [Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins, University School of Medicine, Baltimore, Maryland 21287 (United States); Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins, University School of Medicine, Baltimore, Maryland 21287 (United States) and Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21287 (United States); Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins, University School of Medicine, Baltimore, Maryland 21287 (United States)

2012-05-15

219

GPU-based real-time structured light 3D scanner at 500 fps  

NASA Astrophysics Data System (ADS)

In this study, we develop a real-time, structured light 3D scanner that can output 3D video of 512×512 pixels at 500 fps using a GPU-based, high-speed vision system synchronized with a high-speed DLP projector. Our 3D scanner projects eight pairs of positive and negative image patterns with 8-bit gray code on the measurement objects at 1000 fps. Synchronized with the high-speed vision platform, these images are simultaneously captured at 1000 fps and processed in real time for 3D image generation at 500 fps by introducing parallel pixel processing on a NVIDIA Tesla 1060 GPU board. Several experiments are performed for high-speed 3D objects that undergo sudden 3D shape deformation.

Gao, Hao; Takaki, Takeshi; Ishii, Idaku

2012-05-01

220

Post-mortem magnetic resonance microscopy (MRM) of the murine brain at 7 Tesla results in a gain of resolution as compared to in vivo MRM  

PubMed Central

Small-animal MRI with high field strength allows imaging of the living animal. However, spatial resolution in in vivo brain imaging is limited by the scanning time. Measurements of fixated mouse brains allow longer measurement time, but fixation procedures are time consuming, since the process of fixation may take several weeks. We here present a quick and simple post-mortem approach without fixation that allows high-resolution MRI even at 7 Tesla (T2-weighted MRI). This method was compared to in vivo scans with optimized spatial resolution for the investigation of anesthetized mice (T1-weighted MRI) as well as to ex situ scans of fixed brains (T1- and T2-weighted scans) by using standard MRI-sequences, along with anatomic descriptions of areas observable in the MRI, analysis of tissue shrinkage and post-processing procedures (intensity inhomogeneity correction, PCNN3D brain extract, SPMMouse segmentation, and volumetric measurement). Post-mortem imaging quality was sufficient to determine small brain substructures on the morphological level, provided fast possibilities for volumetric acquisition and for automatized processing without manual correction. Moreover, since no fixation was used, tissue shrinkage due to fixation does not occur as it is, e.g., the case by using ex vivo brains that have been kept in fixatives for several days. Thus, the introduced method is well suited for comparative investigations, since it allows determining small structural alterations in the murine brain at a reasonable high resolution even by MRI performed at 7 Tesla.

von Bohlen und Halbach, Oliver; Lotze, Martin; Pfannmoller, Jorg P.

2014-01-01

221

fMRI evidence of improved visual function in patients with progressive retinitis pigmentosa by eye-movement training  

PubMed Central

To evaluate changes in the visual processing of patients with progressive retinitis pigmentosa (RP) who acquired improved reading capability by eye-movement training (EMT), we performed functional magnetic resonance imaging (fMRI) before and after EMT. Six patients with bilateral concentric contraction caused by pigmentary degeneration of the retina and 6 normal volunteers were recruited. Patients were given EMT for 5 min every day for 8–10 months. fMRI data were acquired on a 3.0-Tesla scanner while subjects were performing reading tasks. In separate experiments (before fMRI scanning), visual performances for readings were measured by the number of letters read correctly in 5 min. Before EMT, activation areas of the primary visual cortex of patients were 48.8% of those of the controls. The number of letters read correctly in 5 min was 36.6% of those by the normal volunteers. After EMT, the activation areas of patients were not changed or slightly decreased; however, reading performance increased in 5 of 6 patients, which was 46.6% of that of the normal volunteers (p< 0.05). After EMT, increased activity was observed in the frontal eye fields (FEFs) of all patients; however, increases in the activity of the parietal eye fields (PEFs) were observed only in patients who showed greater improvement in reading capability. The improvement in reading ability of the patients after EMT is regarded as an effect of the increased activity of FEF and PEF, which play important roles in attention and working memory as well as the regulation of eye movements.

Yoshida, Masako; Origuchi, Maki; Urayama, Shin-ichi; Takatsuki, Akira; Kan, Shigeyuki; Aso, Toshihiko; Shiose, Takayuki; Sawamoto, Nobukatsu; Miyauchi, Satoru; Fukuyama, Hidenao; Seiyama, Akitoshi

2014-01-01

222

Multispectral Scanner for Monitoring Plants  

NASA Technical Reports Server (NTRS)

A multispectral scanner has been adapted to capture spectral images of living plants under various types of illumination for purposes of monitoring the health of, or monitoring the transfer of genes into, the plants. In a health-monitoring application, the plants are illuminated with full-spectrum visible and near infrared light and the scanner is used to acquire a reflected-light spectral signature known to be indicative of the health of the plants. In a gene-transfer- monitoring application, the plants are illuminated with blue or ultraviolet light and the scanner is used to capture fluorescence images from a green fluorescent protein (GFP) that is expressed as result of the gene transfer. The choice of wavelength of the illumination and the wavelength of the fluorescence to be monitored depends on the specific GFP.

Gat, Nahum

2004-01-01

223

A study of quantification of aortic compliance in mice using radial acquisition phase contrast MRI  

NASA Astrophysics Data System (ADS)

Spatiotemporal changes in blood flow velocity measured using Phase contrast Magnetic Resonance Imaging (MRI) can be used to quantify Pulse Wave Velocity (PWV) and Wall Shear Stress (WSS), well known indices of vessel compliance. A study was conducted to measure the PWV in the aortic arch in young healthy children using conventional phase contrast MRI and a post processing algorithm that automatically track the peak velocity in phase contrast images. It is shown that the PWV calculated using peak velocity-time data has less variability compared to that using mean velocity and flow. Conventional MR data acquisition techniques lack both the spatial and temporal resolution needed to accurately calculate PWV and WSS in in vivo studies using transgenic animal models of arterial diseases. Radial k-space acquisition can improve both spatial and temporal resolution. A major part of this thesis was devoted to developing technology for Radial Phase Contrast Magnetic Resonance (RPCMR) cine imaging on a 7 Tesla Animal scanner. A pulse sequence with asymmetric radial k-space acquisition was designed and implemented. Software developed to reconstruct the RPCMR images include gridding, density compensation and centering of k-Space that corrects the image ghosting introduced by hardware response time. Image processing software was developed to automatically segment the vessel lumen and correct for phase offset due to eddy currents. Finally, in vivo and ex vivo aortic compliance measurements were conducted in a well-established mouse model for atherosclerosis: Apolipoprotein E-knockout (ApoE-KO). Using RPCMR technique, a significantly higher PWV value as well as a higher average WSS was detected among 9 months old ApoE-KO mice compare to in wild type mice. A follow up ex-vivo test of tissue elasticity confirmed the impaired distensibility of aortic arteries among ApoE-KO mice.

Zhao, Xuandong

224

Choosing a Scanner: Points To Consider before Buying a Scanner.  

ERIC Educational Resources Information Center

Outlines ten factors to consider before buying a scanner: size of document; type of document; color; speed and volume; resolution; image enhancement; image compression; optical character recognition; scanning subsystem; and the option to use a commercial bureau service. The importance of careful analysis of requirements is emphasized. (AEF)

Raby, Chris

1998-01-01

225

MRI Scans  

MedlinePLUS

Magnetic resonance imaging (MRI) uses a large magnet and radio waves to look at organs and structures inside your body. Health care professionals use MRI scans to diagnose a variety of conditions, from ...

226

Scanner as a Fine Art  

ERIC Educational Resources Information Center

Not every art department is fortunate enough to have access to digital cameras and image-editing software, but if a scanner, computer, and printer are available, students can create some imaginative and surreal work. This high-school level lesson begins with a discussion of self-portraits, and then moves to students creating images by scanning…

Fontes, Kris

2008-01-01

227

Multispectral scanner (MSS), ERTS-1  

NASA Technical Reports Server (NTRS)

The multispectral scanner onboard ERTS-A spacecraft provides simultaneous images in three visible bands and one near infrared band. The instrument employs fiber optics to transfer optical images to the detectors and photomultiplier tubes. Detector outputs are digitized and multiplexed for transmission from the spacecraft by analog to digital processor.

Arlauskas, J.

1973-01-01

228

TIMS (Thermal Infrared Multispectral Scanner) Investigator's Guide.  

National Technical Information Service (NTIS)

The Thermal Infrared Multispectral Scanner (TIMS) is a NASA aircraft scanner providing six-channel spectral capability in the thermal infrared region of the electromagnetic spectrum. Operating in the thermal infrared atmospheric window region (8 to 12 mic...

F. D. Palluconi

1986-01-01

229

Extreme Material Physical Properties and Measurements above 100 tesla  

Microsoft Academic Search

The National High Magnetic Field Laboratory (NHMFL) Pulsed Field Facility (PFF) at Los Alamos National Laboratory (LANL) offers extreme environments of ultra high magnetic fields above 100 tesla by use of the Single Turn method as well as fields approaching 100 tesla with more complex methods. The challenge of metrology in the extreme magnetic field generating devices is complicated by

Charles Mielke

2011-01-01

230

HOM BEAM COUPLING MEASUREMENTS AT THE TESLA TEST FACILITY (TTF)  

Microsoft Academic Search

The proper damping of the higher order modes (HOM) of the TESLA superconducting accelerating cavities is a crucial requirement for the emittance preservation in the TESLA linacs. Experiments of HOM beam excitation have been performed on the accelerating modules of the TTF linac, with a recent emphasis on the measurement of the beam coupling and HOM polarization, in contrast to

G. Devanz; M. Jablonka; C. Magne; O. Napoly; Gif-sur-Yvette M. Huening; M. Wendt

231

Experience with superconducting cavity operation in the TESLA Test Facility  

Microsoft Academic Search

A description of the TESLA Test Facility, which has been set up at DESY by the TESLA Collaboration, is given. Measurements of the superconducting 9-cell cavities in vertical and horizontal test cryostats are presented, as well as the experience with the first two accelerator modules in the TTF linac. Future cavity R&D efforts are described

M. Pekeler

1999-01-01

232

Nikola Tesla and the Wireless Transmission of Energy  

Microsoft Academic Search

Nikola Tesla, the inventor of the polyphase-current system, is best known for his contribution regarding induction and other types of alternating-current machines. His patents and his published and unpublished notes about wireless transmission of energy are less known and, if known to some extent, they are usually wrongly interpreted. For many years the author studied Tesla's works on wireless transmission

A. S. Marincic

1982-01-01

233

Simulation of LANDSAT multispectral scanner spatial resolution with airborne scanner data  

NASA Technical Reports Server (NTRS)

A technique for simulation of low spatial resolution satellite imagery by using high resolution scanner data is described. The scanner data is convolved with the approximate point spread function of the low resolution data and then resampled to emulate low resolution imagery. The technique was successfully applied to Daedalus airborne scanner data to simulate a portion of a LANDSAT multispectra scanner scene.

Hlavka, C. A.

1986-01-01

234

A Simple X-Y Scanner.  

ERIC Educational Resources Information Center

Describes an X-Y scanner used to create acoustic holograms. Scanner is computer controlled and can be adapted to digitize pictures. Scanner geometry is discussed. An appendix gives equipment details. The control program in ATOM BASIC and 6502 machine code is available from the authors. (JM)

Halse, M. R.; Hudson, W. J.

1986-01-01

235

Nikola Tesla: the man behind the magnetic field unit.  

PubMed

The magnetic field strength of both the magnet and gradient coils used in MR imaging equipment is measured in Tesla units, which are named for Nikola Tesla. This article presents the life and achievements of this Serbian-American inventor and researcher who discovered the rotating magnetic field, the basis of most alternating-current machinery. Nikola Tesla had 700 patents in the United States and Europe that covered every aspect of science and technology. Tesla's discoveries include the Tesla coil, AC electrical conduction, improved lighting, newer forms of turbine engines, robotics, fluorescent light, wireless transmission of electrical energy, radio, remote control, discovery of cosmic radio waves, and the use of the ionosphere for scientific purposes. He was a genius whose discoveries had a pivotal role in advancing us into the modern era. PMID:14994307

Roguin, Ariel

2004-03-01

236

MRI-guided prostate brachytherapy with single needle method—a planning study  

Microsoft Academic Search

Background and purposeMagnetic resonance image (MRI)-guided prostate brachytherapy with a conventional closed MR scanner is hampered by the limited access to the prostate. To handle this problem, we have designed a new implantation method, based on a patient lying in a closed MR scanner, a robotic device to be placed between patient's legs, and one needle with one insertion point.

Marion P. R Van Gellekom; Marinus A Moerland; Jan J Battermann; Jan J. W Lagendijk

2004-01-01

237

"MRI Stealth" robot for prostate interventions.  

PubMed

The paper reports an important achievement in MRI instrumentation, a pneumatic, fully actuated robot located within the scanner alongside the patient and operating under remote control based on the images. Previous MRI robots commonly used piezoelectric actuation limiting their compatibility. Pneumatics is an ideal choice for MRI compatibility because it is decoupled from electromagnetism, but pneumatic actuators were hardly controllable. This achievement was possible due to a recent technology breakthrough, the invention of a new type of pneumatic motor, PneuStep 1, designed for the robot reported here with uncompromised MRI compatibility, high-precision, and medical safety. MrBot is one of the "MRI stealth" robots today (the second is described in this issue by Zangos et al.). Both of these systems are also multi-imager compatible, being able to operate with the imager of choice or cross-imaging modalities. For MRI compatibility the robot is exclusively constructed of nonmagnetic and dielectric materials such as plastics, ceramics, crystals, rubbers and is electricity free. Light-based encoding is used for feedback, so that all electric components are distally located outside the imager's room. MRI robots are modern, digital medical instruments in line with advanced imaging equipment and methods. These allow for accessing patients within closed bore scanners and performing interventions under direct (in scanner) imaging feedback. MRI robots could allow e.g. to biopsy small lesions imaged with cutting edge cancer imaging methods, or precisely deploy localized therapy at cancer foci. Our robot is the first to show the feasibility of fully automated in-scanner interventions. It is customized for the prostate and operates transperineally for needle interventions. It can accommodate various needle drivers for different percutaneous procedures such as biopsy, thermal ablations, or brachytherapy. The first needle driver is customized for fully automated low-dose radiation seed brachytherapy. This paper gives an introduction to the challenges of MRI robot compatibility and presents the solutions adopted in making the MrBot. Its multi-imager compatibility and other preclinical tests are included. The robot shows the technical feasibility of MRI-guided prostate interventions, yet its clinical utility is still to be determined. PMID:17763098

Stoianovici, Dan; Song, Danny; Petrisor, Doru; Ursu, Daniel; Mazilu, Dumitru; Muntener, Michael; Mutener, Michael; Schar, Michael; Patriciu, Alexandru

2007-01-01

238

Optical scanner. [laser doppler velocimeters  

NASA Technical Reports Server (NTRS)

An optical scanner that sequentially focuses optical energy (light) at selected points in space is described. The essential component is a scanning wheel including several glass windows with each window having a different thickness. Due to this difference in thickness, the displacement of the emerging light from the incident light is different for each window. The scanner transmits optical energy to a point in space while at the same time receiving any optical energy generated at that point and then moves on to the next selected point and repeats this transmit and receive operation. It fills the need for a system that permits a laser velocimeter to rapidly scan across a constantly changing flow field in an aerodynamic test facility.

Rhodes, D. B. (inventor)

1977-01-01

239

Vacuum Attachment for XRF Scanner  

NASA Technical Reports Server (NTRS)

Vacuum apparatuses have been developed for increasing the range of elements that can be identified by use of x-ray fluorescent (XRF) scanners of the type mentioned in the two immediately preceding articles. As a consequence of the underlying physical principles, in the presence of air, such an XRF scanner is limited to analysis of chlorine and elements of greater atomic number. When the XRF scanner is operated in a vacuum, it extends the range of analysis to lower atomic numbers - even as far as aluminum and sodium. Hence, more elements will be available for use in XRF labeling of objects as discussed in the two preceding articles. The added benefits of the extended capabilities also have other uses for NASA. Detection of elements of low atomic number is of high interest to the aerospace community. High-strength aluminum alloys will be easily analyzed for composition. Silicon, a major contaminant in certain processes, will be detectable before the process is begun, possibly eliminating weld or adhesion problems. Exotic alloys will be evaluated for composition prior to being placed in service where lives depend on them. And in the less glamorous applications, such as bolts and fasteners, substandard products and counterfeit items will be evaluated at the receiving function and never allowed to enter the operation

Schramm, Harry F.; Kaiser, Bruce

2005-01-01

240

PET/MRI: challenges, solutions and perspectives.  

PubMed

Already from the start of PET/CT integrating positron emission tomography (PET) and computed tomography (CT) in one instrument, there have been considerations how to combine PET and magnetic resonance imaging (MRI) so that their complementary abilities can be utilized in a single investigation. Since classical PET electronics fail in an even weak magnetic field and PET signal processing might disturb high-frequency signals of MRI, it soon became clear that new solutions had to be found to avoid mutual interferences. During the last fifteen years a number of different approaches towards PET/MRI for small animal imaging have been developed by research groups which together with their specific features are summarized in this review. Recently, PET/MRI for human imaging became available as well - this time by industrial initiatives. First some prototypes of BrainPET/MRI were developed followed by commercial products for simultaneous and non-simultaneous whole-body PET/MRI. Although only PET/MRI integrated in one scanner offers the full diversity of complementary multiparametric imaging, there are also promising applications of non-simultaneous sequential PET/MRI. While describing the present instrumentation for human PET/MRI, this review discusses the challenges and promises related to this new imaging technology. PMID:22925652

Herzog, Hans

2012-12-01

241

The Transeurope Footrace Project: longitudinal data acquisition in a cluster randomized mobile MRI observational cohort study on 44 endurance runners at a 64-stage 4,486km transcontinental ultramarathon  

PubMed Central

Background The TransEurope FootRace 2009 (TEFR09) was one of the longest transcontinental ultramarathons with an extreme endurance physical load of running nearly 4,500 km in 64 days. The aim of this study was to assess the wide spectrum of adaptive responses in humans regarding the different tissues, organs and functional systems being exposed to such chronic physical endurance load with limited time for regeneration and resulting negative energy balance. A detailed description of the TEFR project and its implemented measuring methods in relation to the hypotheses are presented. Methods The most important research tool was a 1.5 Tesla magnetic resonance imaging (MRI) scanner mounted on a mobile unit following the ultra runners from stage to stage each day. Forty-four study volunteers (67% of the participants) were cluster randomized into two groups for MRI measurements (22 subjects each) according to the project protocol with its different research modules: musculoskeletal system, brain and pain perception, cardiovascular system, body composition, and oxidative stress and inflammation. Complementary to the diverse daily mobile MR-measurements on different topics (muscle and joint MRI, T2*-mapping of cartilage, MR-spectroscopy of muscles, functional MRI of the brain, cardiac and vascular cine MRI, whole body MRI) other methods were also used: ice-water pain test, psychometric questionnaires, bioelectrical impedance analysis (BIA), skinfold thickness and limb circumference measurements, daily urine samples, periodic blood samples and electrocardiograms (ECG). Results Thirty volunteers (68%) reached the finish line at North Cape. The mean total race speed was 8.35 km/hour. Finishers invested 552 hours in total. The completion rate for planned MRI investigations was more than 95%: 741 MR-examinations with 2,637 MRI sequences (more than 200,000 picture data), 5,720 urine samples, 244 blood samples, 205 ECG, 1,018 BIA, 539 anthropological measurements and 150 psychological questionnaires. Conclusions This study demonstrates the feasibility of conducting a trial based centrally on mobile MR-measurements which were performed during ten weeks while crossing an entire continent. This article is the reference for contemporary result reports on the different scientific topics of the TEFR project, which may reveal additional new knowledge on the physiological and pathological processes of the functional systems on the organ, cellular and sub-cellular level at the limits of stress and strain of the human body. Please see related articles: http://www.biomedcentral.com/1741-7015/10/76 and http://www.biomedcentral.com/1741-7015/10/77

2012-01-01

242

A 3.5 Tesla Laboratory Electromagnet  

NASA Astrophysics Data System (ADS)

We report the design and construction of a laboratory electromagnet utilizing HTS coils in an iron yoke with a magnetic flux density of 3.5 Tesla in a 50-mm air-gap. With continuing improvement in the performance of HTS ``BSCCO'' wire, several niche HTS magnet applications have become viable at current wire prices. In this instance, the HTS conductor confers the advantages of high field strength combined with compact size and energy efficiency, in an electromagnet of a format suitable for many materials' characterization techniques, such as vibrating-sample magnetometry, for which the current magnet will be employed. The magnet employs four HTS coils, with a total of 1.6 km of BSCCO wire, which are conduction cooled using a single-stage Gifford-McMahon cryocooler, delivering approximately 25 W of cooling power at the target 35 K operating temperature; HTS current leads are utilized to minimize heat leak to the cryogenic environment.

Pooke, D. M.; Chamritski, V.; Gibson, S.; Fee, M.; King, T.; Staines, M. P.; Flower, N. E.; Buckley, R. G.

2004-06-01

243

Theory and Performance of Tesla Turbines  

NASA Astrophysics Data System (ADS)

This document summarizes the development of an integral perturbation solution of the equations governing momentum transport in microchannels between disks of multiple-disk drag turbines such as the Tesla turbine. This analysis allows a parametric study of turbine performance based on several nondimensional parameters. The results of this analysis are then compared to two sets of test data published in previous work and by other projects. The results are further compared to Computational Fluid Dynamics (CFD) simulations. Finally, expected performance and potential applications of these devices are discussed in light of the results developed. Analysis of this type of flow problem is a key element in the optimal design of Tesla drag-type turbines for geothermal, waste heat, energy harvesting, or solar alternative energy applications. In multiple-disk turbines, high speed flow enters tangentially at the outer radius of cylindrical microchannels formed by closely spaced parallel disks, spiraling through the channel to an exhaust at a small radius or at the center of the disk. Previous investigations have generally developed models based on simplifying idealizations of the flow in these circumstances. Here, beginning with the momentum and continuity equations for incompressible and steady flow in cylindrical coordinates, an integral solution scheme is developed that leads to a dimensionless perturbation series solution that retains the full complement of momentum and viscous effects to consistent levels of approximation in the series solution. This more rigorous approach indicates all dimensionless parameters that affect flow and transport, and allows a direct assessment of the relative importance of viscous, pressure, and momentum effects in different directions in the flow. The resulting lowest-order equations are solved explicitly and higher order terms in the series solutions are determined numerically. Enhancement of rotor drag in this type of turbine enhances energy conversion efficiency. A modified version of the integral perturbation analysis is presented that incorporates the effects of enhanced drag due to surface microstructuring. Results of the model analysis for smooth disk walls are shown to agree well with experimental performance data for two prototype Tesla turbines, and predictions of performance models developed in earlier investigations. Specifically, experimental efficiencies corelate well with those predicted by the integral perturbation solution, deviating by an average of 29% and a maximum of 52%. Model predictions indicate that enhancement of disk drag by strategic microstructuring of the disk surfaces can significantly increase turbine efficiency. Exploratory calculations with the model indicate that turbine efficiencies exceeding 75% can be achieved by designing for optimal ranges of the governing dimensionless parameters. The same parametric trends in performance are compared to test data for a micro-scale Tesla turbine with water as a working fluid. Experimental efficiencies again correlate well with those predicted by the integral perturbation solution. Exerimental efficiencies show a mean deviation of 52% with efficiencies predicted by the model, and a max deviation of 65%. A Computational Fluid Dynamics (CFD) model is then compared to both the analytical and experimental turbine efficiencies. The CFD solutions of the flow field are then used to help reconcile areas where the analytical predictions do not match experimental data. CFD predicted efficiencies match the efficiencies predicted by the integral perturbation solution very closely, deviating by an average of only 18%. Based on the results of the CFD simulations and experimental data, conclusions are made about the validity of the integral perturbation solution. The model accurately predicts the flow inside the rotor, but a better treatment of the flow in the inlet to the turbine is necessary. Despite this, the integral perturbation solution is shown to be capable of directing high efficiency turbine design, and design strategies and param

Romanin, Vincent Domenic

244

Structural Modeling of Tesla TDR Positron Target  

SciTech Connect

The Tesla positron target is a 0.4 radiation length thick titanium target that is rotating with a speed of 50 m/s at its periphery. Energy deposition from one pulse occurs over 1 millisecond and results in heating of the target over a 5 cm arc of material. The 22.2 MeV photon beam has a spot size of 0.75 mm and results in a maximum temperature jump of 440 C. Stresses are induced in the material from thermal expansion of the hotter material. Peak effective stresses reach 38 Ksi (2.7 x 10{sup 8} Pa), which is lower than the typical yield strength of a titanium alloy by a factor of about 3.

Stein, W; Sheppard, J C

2002-03-04

245

Accuracy of MRI technique in measuring tendon cross-sectional area.  

PubMed

Magnetic resonance imaging (MRI) has commonly been applied to determine tendon cross-sectional area (CSA) and length either to measure structural changes or to normalize mechanical measurements to stress and strain. The ability to reproduce CSA measurements on MRI images has been reported, but the accuracy in relation to actual tendon dimensions has never been investigated. The purpose of this study was to compare tendon CSA measured by MRI with that measured in vitro with the mould casting technique. The knee of a horse was MRI-scanned with 1.5 and 3 tesla, and two examiners measured the patellar tendon CSA. Thereafter, the patellar tendon of the horse was completely dissected and embedded in an alginate cast. The CSA of the embedded tendon was measured directly by optical imaging of the cast impression. 1.5 tesla grey tendon CSA and 3 tesla grey tendon CSA were 16.5% and 13.2% lower than the mould tendon CSA, respectively. Also, 3 tesla tendon CSA, based on the red-green border on the National Institute of Health (NIH) colour scale, was lower than the mould tendon CSA by 2.8%. The typical error between examiners was below 2% for all the measured CSA. The typical error between examiners was below 2% for all the measured CSA. These data show that measuring tendon CSA on the grey-scale MRI images is associated with an underestimation, but by optimizing the measurement using a 3 tesla MRI and the appropriate NIH colour scale, this underestimation could be reduced to 2.8% compared with the direct measurements on the mould. PMID:24119143

Couppé, C; Svensson, R B; Sødring-Elbrønd, V; Hansen, P; Kjaer, M; Magnusson, S P

2014-05-01

246

3 tesla magnetic resonance imaging of the occipitoatlantoaxial region in the normal horse.  

PubMed

The aim of this study was to describe the appearance of the ligamentous structures of the occipitoatlantoaxial (OAA) region in the normal horse by 3 tesla (3T) magnetic resonance imaging (MRI). The MRI images of the longitudinal odontoid ligament, tectorial membrane, dorsal and ventral atlantoaxial ligaments, dorsal atlantooccipital membrane with its reinforcing ligaments, and the lateral atlantooccipital ligaments of 10 horse cadavers were evaluated. All ligaments and membranes were identified in all planes, except for the lateral atlantooccipital ligament in the sagittal plane due to its cranioventrolateral course. All were iso to mildly hypointense to musculature of the neck in T1W with the exception of the tectorial membrane that was moderately hypointense; moderately hypointense in PD-SPIR, and markedly hypointense (isointense to cortical bone) in T2W. The PD-SPIR was the best sequence to identify all ligaments and membranes from their cranial and caudal attachments. The longitudinal odontoid ligament, ventral atlantoaxial ligament, and reinforcing bands of the dorsal atlantooccipital membrane presented a characteristic striped heterogeneous signal behavior thought to be due to fibrocartilaginous content. The remaining ligaments and membranes showed homogeneous signal intensity. Special anatomical features in this species such as the fan-shaped longitudinal odontoid ligament, absence of the transverse ligament and presence of the ventral atlantoaxial ligament were documented. Ligamentous structures that stabilize the equine OAA region were described with MRI in this study and these findings could serve as an anatomic reference for those cases where instability of this region is suspected. PMID:24219352

Gutiérrez-Crespo, Beatriz; Kircher, Patrick R; Carrera, Ines

2014-05-01

247

MRI: update on technology diffusion and acquisition.  

PubMed

Over the past three years, magnetic resonance imaging (MRI) has become accepted as a valuable diagnostic tool, and its applications continue to expand. During this time, the number of units installed in the United States doubled. By 1990 about 2,000 MRI units were in place in the United States and nearly 20 percent of the MRI-installed base was mobile, according to a research study conducted by the Hadley Hart Group (Chicago) and Drew Consultants, Inc. (Concord, MA). With the introduction of the prospective payment system, many hospitals were hesitant to spend limited capital on new technology, such as MRI. At the same time, freestanding diagnostic imaging centers were on the rise. Some hospitals and entrepreneurs who foresaw the potential of MRI in health care pioneered its use in the clinical setting. Hospitals began to examine new partnership arrangements and alternative forms of financing, so that they too could offer MRI services. By the end of 1988, the majority of hospitals offering MRI services did not own their own unit and about 40 percent of the hospitals offering MRI services were in a mobile configuration according to the Hadley Hart Group. While the technology has been diffused into 100-bed hospitals via mobile service vendors in some parts of the country, many medium-sized and large hospitals also have entered the MRI services market in this fashion. In the larger hospitals, the patient demand or need for the service often would justify acquisition of MRI, but the expense of the technology, and in many areas restrictive state health planning policies, modified purchase of MRI systems by hospitals. Mobile service vendors offered hospitals a way to startup MRI services in a limited fashion without a major capital expenditure and its associated risk. As hospitals gain experience with mobile MRI and achieve or exceed their early utilization projections, administrators are reevaluating the need to expand services to a full-time fixed site. Early fixed-site MRI providers have been constantly upgrading their MRI capability while planning on adding more units. The technology itself has continued to improve, primarily through the implementation of new software that permits new techniques such as MR angiography (MRA) to be performed. Units are available in a wide price range, price usually reflecting both the field strength (0.5 tesla units cost less) as well as the additional capabilities beyond routine imaging (MRA, spectroscopy).(ABSTRACT TRUNCATED AT 400 WORDS) PMID:10110923

Hoppszallern, S; Hughes, C; Zimmerman, R A

1991-04-01

248

Reproducibility of subregional trabecular bone micro-architectural measures derived from 7-Tesla magnetic resonance images  

PubMed Central

High-resolution magnetic resonance imaging (MRI) of trabecular bone combined with quantitative image analysis represents a powerful technique to gain insight into trabecular bone micro-architectural derangements in osteoporosis and osteoarthritis. The increased signal-to-noise ratio of ultra high-field MR (?7 Tesla) permits images to be obtained with higher resolution and/or decreased scan time compared to scanning at 1.5/3T. In this small feasibility study, we show high measurement precision for subregional trabecular bone micro-architectural analysis performed on 7T knee MR images. The results provide further support for the use of trabecular bone measures as biomarkers in clinical studies of bone disorders.

Wang, Ligong; Liang, Guoyuan; Babb, James S.; Saha, Punam K.; Regatte, Ravinder R.

2013-01-01

249

Nikola Tesla and the wireless transmission of energy  

SciTech Connect

Nikola Tesla, the inventor of the polyphase-current system, is best known for his contribution regarding induction and other types of alternating-current machines. His patents and his published and unpublished notes about wireless transmission of energy are less known and, if known to some extent, they are usually wrongly interpreted. For many years the author studied Tesla's works on wireless transmission of energy and that what is given here is a review of relevant documents, unpublished notes and letters from the archives of the Nikola Tesla Museum in Belgrade. An attempt is made to explain Tesla's physical model on the basis of which he concluded that the wireless transmission of energy on a global scale is possible. His model is critically examined in view of the present day knowledge of extremely low frequency propagation phenomena.

Marincic, A.S.

1982-10-01

250

Single Crystal Niobium RF Cavity of the TESLA Shape.  

National Technical Information Service (NTIS)

A fabrication method for single crystal niobium cavities of the TESLA shape was proposed on the basis of metallographic investigations and electron beam welding tests on niobium single crystals. These tests showed that a cavity can be produced without gra...

P. Kneisel W. Singer X. Singer

2007-01-01

251

Scanner-dependent optical proximity effects  

NASA Astrophysics Data System (ADS)

Optical imaging of IC critical designs is impacted by optical proximity effects, OPEs, originating from finite numerical aperture of projection lenses used in modern projectors. The OPE's are caused by filtering of pattern diffraction orders falling outside of the lens band pass. Controlling OPEs is so critical to IC performance, that IC design community implemented optical proximity correction, OPC, modifying the IC mask patterns to provide wafer images matching the IC design intent. The mainstream OPC uses optical models representing fundamental imaging setup and it does not capture the impacts of engineering scanner tool constraints. The OPEs are impacted by scanner lens and illuminator signatures causing CD excursions large in comparison to the CD error budgets(1). The magnitude of the scanner impacts on OPEs necessitated new optical modeling paradigm involving imaging models imbedding scanner signatures representing population of scanners of a given type. These scanner-type based models represent quantum leap in accuracy of lithography simulation technology, resulting in OPE and OPC representing a broad range of realistic scanner characteristics(2). In this context, a relevant question is: to what degree, the signatures of individual scanners impact the accuracy of imaging models and OPE predictions? To answer this question, we analyzed optical proximity responses of hyper-NA scanners represented by their signatures. We first studied a set of OPEs impacted by the scanner-type signatures. We then generated a set of corresponding OPEs impacted by the signatures of individual scanners. We compared the two kinds of OPEs and highlighted the scanner-specific image formation responses.

Tyminski, Jacek K.; Matsuyama, Tomoyuki; Nakashima, Toshiharu; Inoue, Ryuichi

2009-03-01

252

RHQT Nb3Al 15Tesla magnet design study  

Microsoft Academic Search

Feasibility study of 15-Tesla dipole magnets wound with a new copper stabilized RHQT NbâAl Rutherford cable is presented. A new practical long copper stabilized RHQT NbâAl strand is presented, which is being developed and manufactured at the National Institute of Material Science (NIMS) in Japan. It has achieved a non-copper J{sub c} of 1000A\\/mm² at 15 Tesla at 4.2K, with

R. Yamada; G. Ambrosio; E. Barzi; V. Kashikin; A. Kikuchi; I. Novitski; T. Takeuchi; M. Wake; A. Zlobin

2005-01-01

253

Nikola Tesla and the Wireless Transmission of Energy  

Microsoft Academic Search

Nikola Tesla, the inventorof the poly- phase-current system, is best known for his contribution regarding induction and other types of alternating-current machines. His patents and his published and unpublished notes about wireless transmission of energy are less known and, if known to some extent, they are usually wrongly interpreted. rFor many years the author studied Tesla's works on wireless transmission

A. S. Marincic

1982-01-01

254

Functional imaging of the thoracic outlet syndrome in an open MR scanner  

Microsoft Academic Search

.   Symptoms due to thoracic outlet syndrome may present only in abduction, a position that cannot be investigated in conventional\\u000a MR scanners. Therefore, this study was initiated to test MRI in an open magnet as a method for diagnosis of thoracic outlet\\u000a syndrome. Ten volunteers and 7 patients with a clinical suspicion of thoracic outlet syndrome were investigated at 0.5

Ö. Smedby; H. Rostad; Ø. Klaastad; F. Lilleås; T. Tillung; E. Fosse

2000-01-01

255

Mapping of cerebral oxidative metabolism with MRI  

PubMed Central

Using a T1? MRI based indirect detection method, we demonstrate the detection of cerebral oxidative metabolism and its modulation by administration of the mitochondrial uncoupling agent 2,4-dinitrophenol (DNP) in a large animal model with minimum utilization of gas. The study was performed by inhalation in swine during imaging on clinical MRI scanners. Metabolic changes in swine were determined by two methods. First, in a series of animals, increased metabolism caused by DNP injection was measured by exhaled gas analysis. The average whole-body metabolic increase in seven swine was 11.9%+/-2.5% per mg/kg, stable over three hours. Secondly, hemispheric brain measurements of oxygen consumption stimulated by DNP injection were made in five swine using T1? MRI following administration of gas. Metabolism was calculated from the change in the T1? weighted MRI signal due to H217O generated from inhalation before and after doubling of metabolism by DNP. These results were confirmed by direct oxygen-17 MR spectroscopy, a gold standard for in vivo H217O measurement. Overall, this work underscores the ability of indirect oxygen-17 imaging to detect oxygen metabolism in an animal model with a lung capacity comparable to the human with minimal utilization of expensive gas. Given the demonstrated high efficiency in use of and the proven feasibility of performing such measurements on standard clinical MRI scanners, this work enables the adaption of this technique for human studies dealing with a broad array of metabolic derangements.

Mellon, Eric A.; Beesam, R. Shashank; Elliott, Mark A.; Reddy, Ravinder

2010-01-01

256

Magnetic resonance imaging (MRI): effects of electro-magnetic radiation and safety aspects  

Microsoft Academic Search

Magnetic resonance imaging (MRI) is a widely used noninvasive imaging modality for obtaining diagnostic radiological images. An MRI scanner consists of several diverse technological components such as powerful static magnetic field, rapidly varying local gradient magnetic fields, pulsed radiofrequency (RF) field and liquid helium and\\/or liquid nitrogen. At present, there is no conclusive evidence for adverse biological effects in patients

N. R JAGANNATECAN

1999-01-01

257

Quality of EEG in simultaneous EEG-fMRI for epilepsy  

Microsoft Academic Search

It is now possible to record the EEG continuously during fMRI studies. This is a very promising methodology that combines knowledge about neuronal activity and its metabolic response. The EEG recorded inside the fMRI scanner is, however, heavily contaminated by artifacts caused by the high intensity magnetic field and rapidly changing field gradients. Methods have been reported in the literature

Christian-G Bénar; Yahya Aghakhani; Yunhua Wang; Aaron Izenberg; Abdullah Al-Asmi; François Dubeau; Jean Gotman

2003-01-01

258

Proposed applications with implementation techniques of the upcoming renewable energy resource, The Tesla Turbine  

NASA Astrophysics Data System (ADS)

Recent research has shown that tesla turbine can be one of the future efficient sources of renewable energy. Modern techniques used for designing of tesla turbine have given optimum results regarding efficiency and applications. In this paper we have suggested fully coordinated applications of tesla turbine in different fields particularly in power generation at both low level and high level generation. In Energy deficient countries the tesla turbine has wide range of applications and it can play an important role in energy management system. Our proposed applications includes, the use of tesla turbine as renewable energy resource using tesla turbine in distributed generation system use of tesla turbine at home for power generation use of tesla turbine in irrigation channels using tesla turbine in hybrid electric vehicles All applications are explained with the help of flow charts and block diagrams and their implementation techniques are also explained in details. The results of physical experiments and simulations are also included for some applications.

Usman Saeed Khan, M.; Maqsood, M. Irfan; Ali, Ehsan; Jamal, Shah; Javed, M.

2013-06-01

259

[Ultrahigh field MRI in context of neurological diseases].  

PubMed

Ultrahigh field magnetic resonance imaging (UHF-MRI) has recently gained substantial scientific interest. At field strengths of 7 Tesla (T) and higher UHF-MRI provides unprecedented spatial resolution due to an increased signal-to-noise ratio (SNR). The UHF-MRI method has been successfully applied in various neurological disorders. In neuroinflammatory diseases UHF-MRI has already provided a detailed insight into individual pathological disease processes and elucidated differential diagnoses of several disease entities, e.g. multiple sclerosis (MS), neuromyelitis optica (NMO) and Susac's syndrome. The excellent depiction of normal blood vessels, vessel abnormalities and infarct morphology by UHF-MRI can be utilized in vascular diseases. Detailed imaging of the hippocampus in Alzheimer's disease and the substantia nigra in Parkinson's disease as well as sensitivity to iron depositions could be valuable in neurodegenerative diseases. Current UHF-MRI studies still suffer from small sample sizes, selection bias or propensity to image artefacts. In addition, the increasing clinical relevance of 3T-MRI has not been sufficiently appreciated in previous studies. Although UHF-MRI is only available at a small number of medical research centers it could provide a high-end diagnostic tool for healthcare optimization in the foreseeable future. The potential of UHF-MRI still has to be carefully validated by profound prospective research to define its place in future medicine. PMID:24549692

Kuchling, J; Sinnecker, T; Bozin, I; Dörr, J; Madai, V I; Sobesky, J; Niendorf, T; Paul, F; Wuerfel, J

2014-04-01

260

Functional lateralization of human gustatory cortex related to handedness disclosed by fMRI study.  

PubMed

Ten healthy subjects aged 20-25 including five right-handed and five left-handed according to the Dellatolas test participated in this functional magnetic resonance imaging (fMRI) study. A 3 Tesla whole-body MR scanner allowed echo planar imaging (EPI)-64 x 64 pixels, repetition time (TR) = 6 s, field of view (FOV) = 20 x 20 cm2--associated to acute anatomical localization of activated foci (256 x 256 pixels). Subjects were bilaterally stimulated with NaCl 85 mM, aspartame 2 mM, quinine hydrochloride 1 mM, glycyrrhizic acid 0.5 mM, guanosine monophosphate 1 mM and D-threonine 250 mM alternating with water. Stimuli and rinse were continuously pushed as bolus of 50 microliters every 3 s to the subject's mouth through microsyringes. We detected brain activated areas by correlation of the MR signal to an on-line perception profile recorded for each experiment and each subject with the finger-span method. We found most activations in the insula and the perisylvian region in agreement with previous electrophysiological studies on monkeys and clinical reports in humans. The superior part of the insula was bilaterally activated, in accordance with a whole-mouth stimulation. A striking lateralization related to handedness was found in a lower part of the insula. This projection in the dominant hemisphere, located in the same coronal plane as the upper insular activation, is the first evidence of a functional lateralization of brain processing involved in taste perception. PMID:9929653

Cerf, B; Lebihan, D; Van de Moortele, P F; Mac Leod, P; Faurion, A

1998-11-30

261

Progress toward 10 tesla accelerator dipoles  

SciTech Connect

A 9.1 T central field has been achieved in a Nb-Ti dipole operating in pressurized helium II at 1.8 K. Three different Nb-Ti dipoles, without iron yokes, have achieved central fields of 8.0, 8.6, and 9.1 T - all short sample performance for the conductors at 1.8 K. In helium I, at 4.3 K, the maximum central fields are from 1.5 to 2.0 T lower. Ten-tesla magnets have been designed for both Nb-Ti operating at 1.8 K and Nb/sub 3/Sn operating at 4.2 K. They are based on a very small beam aperture, (40 to 45 mm), very high current density in the superconductors (over 1000 A/mm/sup 2/), and a very low ratio of stabilizing copper to superconductor (about 1). Both layer and block designs have been developed that utilize Rutherford Cable. Magnet cycling from 0 to 6 T has been carried out for field change rate up to 1 T/s; the cyclic heating at 1 T/s is 36 W per meter. At a more representative rate of 0.2 T/s the heating rate is only 2 W/m. Progress in the program to use Nb/sub 3/Sn and NbTi superconductor, in 10 T accelerator magnets is also discussed.

Hassenzahl, W.; Gilbert, G.; Taylor, C.; Meuser, R.

1983-08-01

262

Capture Andevaluation of Airborne Laser Scanner Data  

Microsoft Academic Search

The development of laser sensors for the direct measurement of the terrain surface resulted in airborne systems allowing an area covering 3D data capture which are already in commercial use. By the integration of the laser scanner with sensors for the absolute orientation of the laser scanner at the time of measurement, like the NAVSTAR Global Positioning System (GPS) for

Johannes Kilian; Norbert Haala; Markus Englich

1996-01-01

263

FR4 Laser Scanner With Dynamic Focus  

Microsoft Academic Search

An electromagnetically actuated optical scanner made using standard printed circuit board technology with integrated dynamic focusing feature is presented. Dynamic focus is achieved with an independently controlled plunger machined on the flame retardant-4 (FR4) platform. Integration of a laser diode and lens, torsional scanner, and the plunger for dynamic focus adjustment on FR4 platform greatly improves the form factor of

Serhan O. Isikman; Randy B. Sprague; Hakan Urey

2009-01-01

264

Spatial Calibration Procedure for Infrared Line Scanners  

Microsoft Academic Search

Thermographic devices which are able to acquire images, such as infrared line scanners, are becoming increasingly popular. One of the major issues when working with this kind of devices is accurate spatial calibration, necessary in order to extract metric information from images. In this work, a spatial calibration procedure for infrared line scanners is proposed. The proposed procedure is based

Rubén Usamentiaga; Daniel F. García; Diego González; Julio Molleda

2006-01-01

265

Academic and Career Advising of Scanners  

ERIC Educational Resources Information Center

"Scanners" has become a common term for a recently identified category of people who find choosing just one interest or career path difficult (Sher, 2006). Academic and career advisors who work with scanners will likely find that these students have difficulty selecting an academic major or career path and that they seem to suffer anxiety and a…

Bloom, Arvid J.; Tripp, Philip R.; Shaffer, Leigh S.

2011-01-01

266

Single Voxel Proton Spectroscopy for Neurofeedback at 7 Tesla  

PubMed Central

Echo-planar imaging (EPI) in fMRI is regularly used to reveal BOLD activation in presubscribed regions of interest (ROI). The response is mediated by relative changes in T2* which appear as changes in the image pixel intensities. We have proposed an application of functional single-voxel proton spectroscopy (fSVPS) for real-time studies at ultra-high MR field which can be comparable to the EPI BOLD fMRI technique. A spin-echo SVPS protocol without water suppression was acquired with 310 repetitions on a 7T Siemens MR scanner (TE/TR = 20/1000 ms, flip angle ? = 90°, voxel size 10 × 10 × 10 mm3). Transmitter reference voltage was optimized for the voxel location. Spectral processing of the water signal free induction decay (FID) using log-linear regression was used to estimate the T2* change between rest and activation of a functional task. The FID spectrum was filtered with a Gaussian window around the water peak, and log-linear regression was optimized for the particular ROI by adoption of the linearization length. The spectroscopic voxel was positioned on an ROI defined from a real-time fMRI EPI BOLD localizer. Additional online signal processing algorithms performed signal drift removal (exponential moving average), despiking and low-pass filtering (modified Kalman filter) and, finally, the dynamic feedback signal normalization. Two functional tasks were used to estimate the sensitivity of the SVPS method compared to BOLD signal changes, namely the primary motor cortex (PMC, left hand finger tapping) and visual cortex (VC, blinking checkerboard). Four healthy volunteers performed these tasks and an additional session using real-time signal feedback modulating their activation level of the PMC. Results show that single voxel spectroscopy is able to provide a good and reliable estimation of the BOLD signal changes. Small data size and FID signal processing instead of processing entire brain volumes as well as more information revealed from the acquired total water spectrum, i.e., direct estimation of the T2* values and B0 changes, make SVPS proton spectroscopy suitable and advantageous for real-time neurofeedback studies. Particular challenges of ultra-high field spectroscopy due to the non-linearity in the spectral information, e.g., poor main magnetic field homogeneity and the absence of motion correction for the SVPS sequence may lead to the special artifacts in the control signal which still need to be addressed. The contrast to noise ratio (CNR), experimental statistic (t-values) and percent signal change were used as quality parameters to estimate the method performance. The potential and challenges of the spectroscopic approach for fMRI studies needs to be further investigated.

Koush, Yury; Elliott, Mark A.; Mathiak, Klaus

2013-01-01

267

[Basic study on MRI guided stereotaxic surgery].  

PubMed

In 1987, we started MRI guided stereotaxic surgery using BRW-MRI apparatus. As distortion of image had been noted around the periphery of MRI due to the characteristic static magnetic field, we examined accuracy of data before clinical application. The MRI machine was a MRT-15A, 0.15 Tesla resistive type made by Toshiba. The stereotaxic apparatus consisted of a head ring, which was fixed to the patient's head, a cubical localizer frame which was attached to the head ring for the scanning phase, and a programmed computer. The localizer frame had multitubular channels, which could be fixed and drained easily with whatever paramagnetic fluid was desired. Since the beginning of our use of the instrument, we have used petroleum jelly. This material produced sufficient localizer image for us to fully determine any MRI scan plane. Once the MRI scan target had been identified, it could be approached stereotaxically in a same way as was done in the CT-related one. In the examination, at first, we studied the MRI image of a grid phantom, or the localizer frame placed on the center of the magnetic field. In the MRI, distortion of the image was seen only at the periphery of the Z axis. Secondly, we calculated the three-dimensional coordinates of the center of tumors in axial, coronal and sagittal images for correlation. But, the target values did not differ by over 5.1 mm. Therefore we concluded that the distortion of the image had minimum effect on surgery. Thirteen surgical operations were performed for brain tumors. Among these surgical interventions biopsy alone was performed in 8 cases, and biopsy combined with brachytherapy was performed in 5 cases.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2674757

Kyuma, Y; Hayashi, A; Odakiri, K; Nakamae, H

1989-05-01

268

Hyperemic stress myocardial perfusion cardiovascular magnetic resonance in mice at 3 Tesla: initial experience and validation against microspheres  

PubMed Central

Background Dynamic first pass contrast-enhanced myocardial perfusion is the standard CMR method for the estimation of myocardial blood flow (MBF) and MBF reserve in man, but it is challenging in rodents because of the high temporal and spatial resolution requirements. Hyperemic first pass myocardial perfusion CMR during vasodilator stress in mice has not been reported. Methods Five C57BL/6 J mice were scanned on a clinical 3.0 Tesla Achieva system (Philips Healthcare, Netherlands). Vasodilator stress was induced via a tail vein catheter with an injection of dipyridamole. Dynamic contrast-enhanced perfusion imaging (Gadobutrol 0.1 mmol/kg) was based on a saturation recovery spoiled gradient echo method with 10-fold k-space and time domain undersampling (k-t PCA). One week later the mice underwent repeat anaesthesia and LV injections of fluorescent microspheres at rest and at stress. Microspheres were analysed using confocal microscopy and fluorescence-activated cell sorting. Results Mean MBF at rest measured by Fermi-function constrained deconvolution was 4.1?±?0.5 ml/g/min and increased to 9.6?±?2.5 ml/g/min during dipyridamole stress (P?=?0.005). The myocardial perfusion reserve was 2.4 ±?0.54. The mean count ratio of stress to rest microspheres was 2.4 ±?0.51 using confocal microscopy and 2.6?±?0.46 using fluorescence. There was good agreement between cardiovascular magnetic resonance CMR and microspheres with no significant difference (P?=?0.84). Conclusion First-pass myocardial stress perfusion CMR in a mouse model is feasible at 3 Tesla. Rest and stress MBF values were consistent with existing literature and perfusion reserve correlated closely to microsphere analysis. Data were acquired on a 3 Tesla scanner using an approach similar to clinical acquisition protocols, potentially facilitating translation of imaging findings between rodent and human studies.

2013-01-01

269

21 CFR 892.1300 - Nuclear rectilinear scanner.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 false Nuclear rectilinear scanner. 892.1300 Section 892.1300 Food...Devices § 892.1300 Nuclear rectilinear scanner. (a) Identification. A nuclear rectilinear scanner is a device intended to image...

2009-04-01

270

21 CFR 882.1925 - Ultrasonic scanner calibration test block.  

Code of Federal Regulations, 2010 CFR

... 2010-04-01 false Ultrasonic scanner calibration test block. 882.1925...Devices § 882.1925 Ultrasonic scanner calibration test block. (a) Identification. An ultrasonic scanner calibration test block is a...

2010-04-01

271

21 CFR 892.1330 - Nuclear whole body scanner.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Nuclear whole body scanner. 892.1330 Section 892.1330 Food...Devices § 892.1330 Nuclear whole body scanner. (a) Identification. A nuclear whole body scanner is a device intended to...

2010-04-01

272

21 CFR 882.1925 - Ultrasonic scanner calibration test block.  

Code of Federal Regulations, 2010 CFR

... 2009-04-01 false Ultrasonic scanner calibration test block. 882.1925...Devices § 882.1925 Ultrasonic scanner calibration test block. (a) Identification. An ultrasonic scanner calibration test block is a...

2009-04-01

273

21 CFR 882.1925 - Ultrasonic scanner calibration test block.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Ultrasonic scanner calibration test block...Diagnostic Devices § 882.1925 Ultrasonic scanner calibration test block. (a) Identification. An ultrasonic scanner calibration test...

2013-04-01

274

Non-Destructive Testing Scanner  

NASA Technical Reports Server (NTRS)

Bio-Imaging Research's technology that originated in an aerospace program has come full circle with a new aerospace adaptation called the Advanced Computed Tomography Inspection System, or ACTIS. The medical version of CT scans the human body for tumors or other abnormalities, the ACTIS system finds imperfections in aerospace structures and components, such as castings, assemblies, rocket motors and nozzles. ACTIS is described by its developer as the most versatile CT scanner available for non-destructive testing applications. ACTIS is a variable geometry system. ACTIS source and detectors can be moved closer together or farther apart to optimize the geometry for different sizes of test objects. The combination of variable geometry, three sources, and focusing detectors makes ACTIS cost effective for a broad range of applications. System can scan anything from very small turbine blades to large rocket assemblies.

1990-01-01

275

Comparison of Detrending Methods for Optimal fMRI Preprocessing  

Microsoft Academic Search

Because of the inherently low signal to noise ratio (SNR) of fMRI data, removal of low frequency signal intensity drift is an important preprocessing step, particularly in those brain regions that weakly activate. Two known sources of drift are noise from the MR scanner and aliasing of physiological pulsations. However, the amount and direction of drift is difficult to predict,

Jody Tanabe; David Miller; Jason Tregellas; Robert Freedman; Francois G. Meyer

2002-01-01

276

Cardiac MRI  

MedlinePLUS

... hearing aids, all of which can be damaged pins, hairpins, metal zippers and similar metallic items, which can distort MRI images removable dental work pens, pocket knives and eyeglasses body piercings ...

277

Knee MRI  

MedlinePLUS

... hearing aids, all of which can be damaged pins, hairpins, metal zippers and similar metallic items, which can distort MRI images removable dental work pens, pocket knives and eyeglasses body piercings ...

278

Shoulder MRI  

MedlinePLUS

... hearing aids, all of which can be damaged pins, hairpins, metal zippers and similar metallic items, which can distort MRI images removable dental work pens, pocket knives and eyeglasses body piercings ...

279

Use of scatterometry for scanner matching  

NASA Astrophysics Data System (ADS)

For the high volume manufacturing at the 45nm node and beyond it is crucial to match the OPC behaviour of all scanners used at a given process step. For this task the ASML LithoTuner PatternMatcher software was used. LithoTuner PatternMatcher is a tool to improve the proximity differences between a reference scanner and one or more so called 'to be matched' scanners. The optimization uses the concept of sensitivities of CDs of critical features towards adjustable scanner parameters in combination with the delta CD's of those critical features. To perform the scanner matching it is very important to have accurate and repeatable CD data. Therefore we investigated the use of scatterometry as a replacement for the traditional CDSEM measurement. Scatterometry significantly enhances the measurement precision while simultaneously reduces the measurement time. In a first step we determined the sensitivities of the structures by measuring the CD response to small perturbations of the individual scanner parameter settings. CD through pitch and repeating 2 dimensional line end structures were measured using the ASML YieldStar tool and a Hitachi CDSEM. The scatterometry- and CDSEM based sensitivities of the scanner parameter settings are compared. Finally a scanner matching based on both sets of sensitivities has been performed. In this article we will show that both methods are suited to perform the scanner matching. We will also present the differences between the two sets of sensitivities obtained with scatterometry and CDSEM. At the end we will present the results of the tool matching and show the results of a cross check. In the cross check sensitivities obtained with the use of scatterometry were used for the scanner matching next to SEM metrology used for verification.

Bald, Holger; Seltmann, Rolf; Bubke, Karsten; Ruhm, Matthias; Noot, Marc; Woischke, Dieter; van Adrichem, Paul; Luehrmann, Paul

2011-02-01

280

17. SITE BUILDING 002 SCANNER BUILDING COMMANDER'S OFFICE ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

17. SITE BUILDING 002 - SCANNER BUILDING - COMMANDER'S OFFICE VIEW. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

281

16. SITE BUILDING 002 SCANNER BUILDING FRONT LOBBY ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

16. SITE BUILDING 002 - SCANNER BUILDING - FRONT LOBBY VIEW. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

282

Function biomedical informatics research network recommendations for prospective multicenter functional MRI studies.  

PubMed

This report provides practical recommendations for the design and execution of multicenter functional MRI (MC-fMRI) studies based on the collective experience of the Function Biomedical Informatics Research Network (FBIRN). The study was inspired by many requests from the fMRI community to FBIRN group members for advice on how to conduct MC-fMRI studies. The introduction briefly discusses the advantages and complexities of MC-fMRI studies. Prerequisites for MC-fMRI studies are addressed before delving into the practical aspects of carefully and efficiently setting up a MC-fMRI study. Practical multisite aspects include: (i) establishing and verifying scan parameters including scanner types and magnetic fields, (ii) establishing and monitoring of a scanner quality program, (iii) developing task paradigms and scan session documentation, (iv) establishing clinical and scanner training to ensure consistency over time, (v) developing means for uploading, storing, and monitoring of imaging and other data, (vi) the use of a traveling fMRI expert, and (vii) collectively analyzing imaging data and disseminating results. We conclude that when MC-fMRI studies are organized well with careful attention to unification of hardware, software and procedural aspects, the process can be a highly effective means for accessing a desired participant demographics while accelerating scientific discovery. PMID:22314879

Glover, Gary H; Mueller, Bryon A; Turner, Jessica A; van Erp, Theo G M; Liu, Thomas T; Greve, Douglas N; Voyvodic, James T; Rasmussen, Jerod; Brown, Gregory G; Keator, David B; Calhoun, Vince D; Lee, Hyo Jong; Ford, Judith M; Mathalon, Daniel H; Diaz, Michele; O'Leary, Daniel S; Gadde, Syam; Preda, Adrian; Lim, Kelvin O; Wible, Cynthia G; Stern, Hal S; Belger, Aysenil; McCarthy, Gregory; Ozyurt, Burak; Potkin, Steven G

2012-07-01

283

Assessment of safety and interference issues of radio frequency identification devices in 0.3 Tesla magnetic resonance imaging and computed tomography.  

PubMed

The objective of this study was to evaluate two issues regarding magnetic resonance imaging (MRI) including device functionality and image artifacts for the presence of radio frequency identification devices (RFID) in association with 0.3 Tesla at 12.7 MHz MRI and computed tomography (CT) scanning. Fifteen samples of RFID tags with two different sizes (wristband and ID card types) were tested. The tags were exposed to several MR-imaging conditions during MRI examination and X-rays of CT scan. Throughout the test, the tags were oriented in three different directions (axial, coronal, and sagittal) relative to MRI system in order to cover all possible situations with respect to the patient undergoing MRI and CT scanning, wearing a RFID tag on wrist. We observed that the tags did not sustain physical damage with their functionality remaining unaffected even after MRI and CT scanning, and there was no alternation in previously stored data as well. In addition, no evidence of either signal loss or artifact was seen in the acquired MR and CT images. Therefore, we can conclude that the use of this passive RFID tag is safe for a patient undergoing MRI at 0.3 T/12.7 MHz and CT Scanning. PMID:24701187

Periyasamy, M; Dhanasekaran, R

2014-01-01

284

Assessment of Safety and Interference Issues of Radio Frequency Identification Devices in 0.3 Tesla Magnetic Resonance Imaging and Computed Tomography  

PubMed Central

The objective of this study was to evaluate two issues regarding magnetic resonance imaging (MRI) including device functionality and image artifacts for the presence of radio frequency identification devices (RFID) in association with 0.3?Tesla at 12.7?MHz MRI and computed tomography (CT) scanning. Fifteen samples of RFID tags with two different sizes (wristband and ID card types) were tested. The tags were exposed to several MR-imaging conditions during MRI examination and X-rays of CT scan. Throughout the test, the tags were oriented in three different directions (axial, coronal, and sagittal) relative to MRI system in order to cover all possible situations with respect to the patient undergoing MRI and CT scanning, wearing a RFID tag on wrist. We observed that the tags did not sustain physical damage with their functionality remaining unaffected even after MRI and CT scanning, and there was no alternation in previously stored data as well. In addition, no evidence of either signal loss or artifact was seen in the acquired MR and CT images. Therefore, we can conclude that the use of this passive RFID tag is safe for a patient undergoing MRI at 0.3 T/12.7?MHz and CT Scanning.

Periyasamy, M.; Dhanasekaran, R.

2014-01-01

285

Magnetic resonance imaging systems: evaluation of 1.5-Tesla systems.  

PubMed

Magnetic resonance imaging (MRI) systems manipulate magnetic fields and radio-frequency signals to create diagnostic images of human anatomy. An MR system is an essential clinical tool, but the cost of buying and installing one is high, so it's crucial that hospitals choose a model carefully. The selection process is made more complex by the numerous options available: different field strengths, gradient systems, coils, and channels, to name just a few. Also, some systems are better than others at facilitating specialized imaging, such as breast and cardiac studies. Our Evaluation is intended to help clarify the choices. We tested three 1.5-tesla systems from three suppliers--GE, Siemens, and Toshiba. We rate the systems for two different uses: inpatient imaging (performed in hospitals) and outpatient imaging (most often performed in imaging centers). For inpatient facilities, which are likely to have less responsive patients and to treat more complex medical problems, the most important purchase considerations will be patient positioning features, advanced imaging capabilities, and system integration. For outpatient facilities, the ability to perform routine exams efficiently and comfortably will be most important. We also provide separate ratings for each system's ability to meet the needs of three specialized applications--breast imaging, cardiac imaging, and functional MRI. PMID:16893049

2006-06-01

286

A comparison of film and phosphor scanners  

SciTech Connect

Signal-to-noise ratios (SNRs) and spatial distortions have been measured for three types of scanners: the Molecular Dynamics (MD) and DuPont film scanners and the MD phosphor scanner. The MD film scanner is a deployable and compact scanner that gives a peak SNR of 110 for low (< 2.0) optical densities (ODs), but the spatial distortions across the digitized film plane are significant. The authors compare this with the DuPont film scanner, which has equally good SNRs at low ODs, but very low spatial distortions. The DuPont also allows the user to define an OD range and contains a prescan function to find the suitable range if the user cannot input such a value; its scan times are quick, and the hardware allows for internal data averaging before being stored to disk. The MD phosphor imager has excellent low-dose capability, producing usable images at a 10-{mu}rad dose (from a 150-pkeV source) but its SNRs are low compared to the film scanner, but they can be increased by adjusting the photomultiplier tube voltage and laser radius across the scan arc.

Chancellor, T.; Morris, R.A.

1993-10-01

287

Joint Assessment of Structural, Perfusion, and Diffusion MRI in Alzheimer's Disease and Frontotemporal Dementia  

PubMed Central

Most MRI studies of Alzheimer's disease (AD) and frontotemporal dementia (FTD) have assessed structural, perfusion and diffusion abnormalities separately while ignoring the relationships across imaging modalities. This paper aimed to assess brain gray (GM) and white matter (WM) abnormalities jointly to elucidate differences in abnormal MRI patterns between the diseases. Twenty AD, 20 FTD patients, and 21 healthy control subjects were imaged using a 4?Tesla MRI. GM loss and GM hypoperfusion were measured using high-resolution T1 and arterial spin labeling MRI (ASL-MRI). WM degradation was measured with diffusion tensor imaging (DTI). Using a new analytical approach, the study found greater WM degenerations in FTD than AD at mild abnormality levels. Furthermore, the GM loss and WM degeneration exceeded the reduced perfusion in FTD whereas, in AD, structural and functional damages were similar. Joint assessments of multimodal MRI have potential value to provide new imaging markers for improved differential diagnoses between FTD and AD.

Zhang, Yu; Schuff, Norbert; Ching, Christopher; Tosun, Duygu; Zhan, Wang; Nezamzadeh, Marzieh; Rosen, Howard J.; Kramer, Joel H.; Gorno-Tempini, Maria Luisa; Miller, Bruce L.; Weiner, Michael W.

2011-01-01

288

Image intensity settings for dual tomographic scanner  

SciTech Connect

The Siemens Gammasonics Pho/Con dual tomographic scanner is well established for multiplane imaging in several routine nuclear medicine procedures. The system is designed to produce tomographic images directly on film, without data storage for replay or image processing. Difficulty can arise when selecting the best film-exposure intensity settings because of count rate variations among patients. A method to translate the tomographic scanner's count density meter readings into optimal film exposure intensity settings is described. This technique is easily adapted to individual choices of film, film processing, and image density. It can be used for the entire sequence of scanner operating parameters.

Summers, P.L.; Drown, D.A.; Blondeau, K.L.; Logan, K.W.

1981-06-01

289

An MRI-Compatible Robotic System With Hybrid Tracking for MRI-Guided Prostate Intervention  

Microsoft Academic Search

This paper reports the development, evaluation, and first clinical trials of the access to the prostate tissue (APT) II system—a scanner independent system for magnetic resonance imaging (MRI)-guided transrectal prostate interventions. The sys- tem utilizes novel manipulator mechanics employing a steerable needle channel and a novel six degree-of-freedom hybrid tracking method, comprising passive fiducial tracking for initial registra- tion and

Axel Krieger; Iulian I. Iordachita; Peter Guion; Anurag K. Singh; Aradhana Kaushal; Cynthia Menard; Peter A. Pinto; Kevin Camphausen; Gabor Fichtinger; Louis L. Whitcomb

2011-01-01

290

Simultaneous MRI and PET imaging of a rat brain  

NASA Astrophysics Data System (ADS)

Multi-modality imaging is rapidly becoming a valuable tool in the diagnosis of disease and in the development of new drugs. Functional images produced with PET fused with anatomical structure images created by MRI will allow the correlation of form with function. Our group is developing a system to acquire MRI and PET images contemporaneously. The prototype device consists of two opposed detector heads, operating in coincidence mode. Each MRI-PET detector module consists of an array of LSO detector elements coupled through a long fibre optic light guide to a single Hamamatsu flat panel position-sensitive photomultiplier tube (PSPMT). The use of light guides allows the PSPMTs to be positioned outside the bore of a 3T MRI scanner where the magnetic field is relatively small. To test the device, simultaneous MRI and PET images of the brain of a male Sprague Dawley rat injected with FDG were successfully obtained. The images revealed no noticeable artefacts in either image set. Future work includes the construction of a full ring PET scanner, improved light guides and construction of a specialized MRI coil to permit higher quality MRI imaging.

Raylman, Raymond R.; Majewski, Stan; Lemieux, Susan K.; Sendhil Velan, S.; Kross, Brian; Popov, Vladimir; Smith, Mark F.; Weisenberger, Andrew G.; Zorn, Carl; Marano, Gary D.

2006-12-01

291

Portable MRI  

SciTech Connect

This project proposes to: (1) provide the power of MRI to situations where it presently isn't available; (2) perform the engineering required to move from lab to a functional prototype; and (3) leverage significant existing infrastructure and capability in ultra-low field MRI. The reasons for doing this: (1) MRI is the most powerful tool for imaging soft-tissue (e.g. brain); (2) Billions don't have access due to cost or safety issues; (3) metal will heat/move in high magnetic fields; (4) Millions of cases of traumatic brain injury in US alone; (5) even more of non-traumatic brain injury; (6) (e.g. stroke, infection, chemical exposure); (7) Need for early diagnostic; (8) 'Signature' wound of recent conflicts; (9) 22% of injuries; (10) Implications for post-traumatic stress disorder; and (11) chronic traumatic encephalopathy.

Espy, Michelle A. [Los Alamos National Laboratory

2012-06-29

292

Pulsed Doppler lidar airborne scanner  

NASA Technical Reports Server (NTRS)

This report covers the work accomplished during the reporting period on Pulsed Doppler Lidar Airborne Scanner and describes plans for the next reporting period. The objectives during the current phase of the contract are divided into four phases. Phase 1 includes ground testing of the system and analysis of data from the 1981 Severe Storms Test Flights. Phase 2 consists of preflight preparation and planning for the 1983 flight series. The flight test itself will be performed during Phase 3, and Phase 4 consists of post-flight analysis and operation of the system after that flight test. The range profile from five samples taken during Flight 10, around 1700 Z is given. The lowest curve is taken from data collected upwind of Mt. Shasta at about 10,000 feet of altitude, in a clear atmosphere, where no signals were observed. It thus is a good representation of the noise level as a function of range. The next curve was taken downwind of the mountain, and shows evidence of atmospheric returns. There is some question as to whether the data are valid at all ranges, or some ranges are contaminated by the others.

Dimarzio, C. A.; Mcvicker, D. B.; Morrow, C. E.; Negus, C. C.

1985-01-01

293

A 10 tesla table-top controlled waveform magnet  

NASA Astrophysics Data System (ADS)

Controlled Waveform Magnets (CWMs) are a special class of pulsed magnets which provide semi-continuous, shape-controlled high magnetic field pulses. In this work we report a table-top CWM, driven by a capacitor bank, capable of producing virtually any user-shaped magnetic field waveform up to 10 Tesla. Insulated Gate Bipolar Transistor (IGBT) chips were paralleled to form the high current switch. Specimen pulse shapes including flat-tops up to 10 Tesla, and linear as well as some sinusoidal-top magnetic field waveforms have been successfully generated.

Roy Choudhury, Aditya N.; Venkataraman, V.

2012-06-01

294

Problem analysis and new design of TESLA coupler  

SciTech Connect

Problem analysis of tested TESLA coupler shows that the microwave discharge is a possible problem. Two new designs are presented. During previous tests of TESLA input coupler (doorknob with cylindrical ceramic window) it was unable to continuously operate above 300--400 kW and a small area of the coupler (area A in Figure 1) where the metal doorknob and ceramic window are only 2 mm apart was coated with metal by unidentified mechanism. In order to understand the problem and help the following designs, it is necessary to analyze possible mechanisms for the problem.

Sun, Ding

1994-06-01

295

High voltage battery cell scanner development  

NASA Technical Reports Server (NTRS)

Battery cell voltage scanners have been previously used in low voltage spacecraft applications. In connection with future missions involving an employment of high-power high voltage power subsystems and/or autonomous power subsystem management for unattended operation, it will be necessary to utilize battery cell voltage scanners to provide battery cell voltage information for early detection of impending battery cell degradation/failures. In preparation for such missions, a novel battery cell voltage scanner design has been developed. The novel design makes use of low voltage circuit modules which can be applied to high voltage batteries in a building block fashion. A description is presented of the design concept and test results of the high voltage battery cell scanner, and its operation with an autonomously managed power subsystem is discussed.

Lepisto, J. W.; Decker, D. K.; Graves, J.

1983-01-01

296

21 CFR 892.1220 - Fluorescent scanner.  

Code of Federal Regulations, 2012 CFR

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1220 Fluorescent scanner. (a) Identification. A fluorescent...

2012-04-01

297

21 CFR 892.1220 - Fluorescent scanner.  

Code of Federal Regulations, 2011 CFR

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1220 Fluorescent scanner. (a) Identification. A fluorescent...

2011-04-01

298

21 CFR 892.1220 - Fluorescent scanner.  

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1220 Fluorescent scanner. (a) Identification. A fluorescent...

2014-04-01

299

Hand-held optical fuel pin scanner  

DOEpatents

An optical scanner for indicia arranged in a focal plane perpendicular to an optical system including a rotatable dove prism. The dove prism transmits a rotating image to a stationary photodiode array.

Kirchner, Tommy L. (Richland, WA); Powers, Hurshal G. (Richland, WA)

1987-01-01

300

Information extraction techniques for multispectral scanner data  

NASA Technical Reports Server (NTRS)

The applicability of recognition-processing procedures for multispectral scanner data from areas and conditions used for programming the recognition computers to other data from different areas viewed under different measurement conditions was studied. The reflective spectral region approximately 0.3 to 3.0 micrometers is considered. A potential application of such techniques is in conducting area surveys. Work in three general areas is reported: (1) Nature of sources of systematic variation in multispectral scanner radiation signals, (2) An investigation of various techniques for overcoming systematic variations in scanner data; (3) The use of decision rules based upon empirical distributions of scanner signals rather than upon the usually assumed multivariate normal (Gaussian) signal distributions.

Malila, W. A.; Crane, R. B.; Turner, R. E.

1972-01-01

301

21 CFR 892.1220 - Fluorescent scanner.  

Code of Federal Regulations, 2013 CFR

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1220 Fluorescent scanner. (a) Identification. A fluorescent...

2013-04-01

302

Introduction to Dynamic Effects and Intercomparison in the MR (Magnetic Resonance) Imaging Process: Four Short Reports on MRI Dynamical and Intercomparitive Phenomena.  

National Technical Information Service (NTIS)

The report provides a brief history of early measurement methods for blood flow, using nuclear magnetic resonance, prior to successful implementation on magnetic resonance imaging (MRI) scanners in 1983; it gives also a description of principles and perfo...

P. R. Moran

1986-01-01

303

Spectrometer and scanner with optofluidic configuration.  

PubMed

We present a spectrometer and scanner based on optofluidic configurations. The main optical component of the spectrometer is a compound optical element consisting of an optofluidic lens and standard blazed diffraction grating. The spectrum size can be changed by filling the lens cavity with different liquids. The scanner comprises two hollow 45° angle prisms oriented at 90° to each other. By changing the liquid inside the prisms, two-dimensional light beam scanning can be performed. PMID:23338199

Calixto, Sergio; Rosete-Aguilar, Martha; Sanchez-Morales, Maria Eugenia; Calixto-Solano, Margarita

2013-01-20

304

Optimization of Tesla turbine using Computational Fluid Dynamics approach  

Microsoft Academic Search

A Tesla turbine is developed in order to utilize the potential energy within household water supply and convert to electricity energy without significant head loss. Pressure within the water supply having higher potential energy compared to the energy needed to reach the reservoir tank. This extra potential energy can be utilized and convert to useful energy before it being waste

Tan Wee Choon; Foo Shy Jer; Lim Eng Aik

2011-01-01

305

A polarized electron-nucleon scattering experiment at TESLA  

Microsoft Academic Search

Longitudinally polarized electrons, accelerated as a small fraction of the total current in the e+ arm of the TESLA collider, can be directed onto a solid state target that may be either longitudinally or transversely polarized. In this way, polarized electron-nucleon scattering measurements can be realized with projected luminosities that are about two orders of magnitude higher than those of

2000-01-01

306

A Single Crystal Niobium RF Cavity of the TESLA Shape  

Microsoft Academic Search

A fabrication method for single crystal niobium cavities of the TESLA shape was proposed on the basis of metallographic investigations and electron beam welding tests on niobium single crystals. These tests showed that a cavity can be produced without grain boundaries even in the welding area. An appropriate annealing allows the outgassing of hydrogen and stress relaxation of the material

W. Singer; X. Singer; P. Kneisel

2007-01-01

307

A solid-state low-voltage Tesla coil demonstrator  

Microsoft Academic Search

A low-voltage demonstration Tesla coil using a solid-state photovoltaic relay to replace the conventional spark gap has been analyzed and then built. This relay incorporates an isolated LED to illuminate a silicon photovoltaic stack which drives a bidirectional FET. Component values for the inductances and capacitances have been determined theoretically from measured parameters. Computer simulation by integrating the coupled circuit

Donald G. Bruns

1992-01-01

308

Nikola Tesla — The creator of the electric age  

Microsoft Academic Search

Nikola Tesla was one of the greatest inventors of all times. He can be placed along with Faraday and Edison as a prolific\\u000a inventor who touched on almost every aspect of electricity. In fact he invented electricity as we know it today and hence\\u000a ushered in the modern age.

Anil K Rajvanshi

2007-01-01

309

Searchers for a new energy source: Tesla, Moray, and Bearden  

Microsoft Academic Search

The work of three leaders in the search for a new energy source, spanning a full century, is examined. Nikola Tesla, T. Henry Moray, and Thomas E. Bearden, among others, have claimed the existence of another source of energy besides those presently in use. This source is the energy contained in apparently empty space. The concepts of each of the

Gary L. Johnson

1992-01-01

310

Nikola Tesla: why was he so much resisted and forgotten?  

Microsoft Academic Search

The amount of published material about Tesla is enormous (thus, he is less forgotten than I thought). The number, importance, and transcendence of his inventions and doings are overwhelming, yet current recognition does not seem to abound, although during his lifetime he did indeed receive many honors. Why then this state of oblivion? What happened? Can history be so blatantly

M. E. Valentinuzzi

1998-01-01

311

Gadoxetic Acid (Gd-EOB-DTPA)-Enhanced MRI versus Gadobenate Dimeglumine (Gd-BOPTA)-Enhanced MRI for Preoperatively Detecting Hepatocellular Carcinoma: an Initial Experience  

PubMed Central

Objective This study was designed to compare the diagnostic performance of gadoxetic acid-enhanced magnetic resonance imaging (MRI) with gadobenate dimeglumine-enhanced MRI for preoperatively detecting hepatocellular carcinoma (HCC). Materials and Methods Eighteen consecutive patients (17 men and one woman, age range: 31-73 years) with 22 HCCs underwent examinations with gadoxetic acid enhanced MRI and gadobenate dimeglumine-enhanced MRI on a 3.0-Tesla unit. The diagnosis of HCC was established after surgical resection and pathological conformation. Three observers independently reviewed each MR image in a random order on a tumor-by-tumor basis. The diagnostic accuracy of these techniques for the detection of HCC was assessed by performing an alternative free-response receiver operating characteristic (ROC) analysis. The sensitivity and positive predictive values were evaluated. Results The average value of the area under the ROC curve (Az) for gadoxetic acid enhanced MRI (0.887) was not significantly different from the Az (0.899) for gadobenate dimeglumine-enhanced MRI (p > 0.05). The overall sensitivities of gadoxetic acid enhanced MRI and gadobenate dimeglumine-enhanced MRI were 80% and 83%, respectively, with no significant difference (p > 0.05). The differences of the positive predictive values for the two contrast agents for each observer were not statistically significant (p > 0.05). Conclusion The diagnostic performance of gadoxetic acid-enhanced MRI and gadobenate dimeglumine-enhanced MRI for preoperatively detecting HCC is quite similar.

Park, Yulri; Kim, Seung Hoon; Jeon, Yong Hwan; Lee, Jongmee; Kim, Min Ju; Choi, Dongil; Lee, Won Jae; Kim, Heejung; Koo, Ji Hyun; Lim, Hyo Keun

2010-01-01

312

Scanner matching using pupil intensity control between scanners in 30nm DRAM device  

NASA Astrophysics Data System (ADS)

Scanner mismatch has become one of the critical issues in high volume memory production. There are several components that contribute to the scanner CD mismatch. One of the major components is illumination pupil difference between scanners. Because of acceleration of dimensional shrinking in memory devices, the CD mismatch became more critical in electrical performance and process window. In this work, we demonstrated computational lithography model based scanner matching for sub 3x nm memory devices. We used ASML XT:1900Gi as a reference scanner and ASML NXT:1950i as the to-be-matched scanner. Wafer metrology data and scanner specific parameters are used to build a computational model, and determine the optimal settings by model simulation to minimize the CD difference between scanners. Nano Geometry Research (NGR) was used as a wafer CD metrology tool for both model calibration and matching result verification. The extracted pupil parameters from measured source map from both before and after matching are inspected and analyzed. Simulated and measured process window changes by applying the matching sub-recipe are also evaluated.

Jang, Jongwon; Park, Daejin; Choi, Jeaseung; Jung, Areum; Yoo, Gyun; Kim, Jungchan; Kim, Cheol-Kyun; Yim, Donggyu; Lu, Junwei; Park, Seunghoon; Yu, Zongchang; Vellanki, Venu; Shao, Wenkin; Park, Chris

2011-03-01

313

Tracking iron in multiple sclerosis: a combined imaging and histopathological study at 7 Tesla  

PubMed Central

Previous authors have shown that the transverse relaxivity R2* and frequency shifts that characterize gradient echo signal decay in magnetic resonance imaging are closely associated with the distribution of iron and myelin in the brain's white matter. In multiple sclerosis, iron accumulation in brain tissue may reflect a multiplicity of pathological processes. Hence, iron may have the unique potential to serve as an in vivo magnetic resonance imaging tracer of disease pathology. To investigate the ability of iron in tracking multiple sclerosis-induced pathology by magnetic resonance imaging, we performed qualitative histopathological analysis of white matter lesions and normal-appearing white matter regions with variable appearance on gradient echo magnetic resonance imaging at 7 Tesla. The samples used for this study derive from two patients with multiple sclerosis and one non-multiple sclerosis donor. Magnetic resonance images were acquired using a whole body 7 Tesla magnetic resonance imaging scanner equipped with a 24-channel receive-only array designed for tissue imaging. A 3D multi-gradient echo sequence was obtained and quantitative R2* and phase maps were reconstructed. Immunohistochemical stainings for myelin and oligodendrocytes, microglia and macrophages, ferritin and ferritin light polypeptide were performed on 3- to 5-µm thick paraffin sections. Iron was detected with Perl's staining and 3,3?-diaminobenzidine-tetrahydrochloride enhanced Turnbull blue staining. In multiple sclerosis tissue, iron presence invariably matched with an increase in R2*. Conversely, R2* increase was not always associated with the presence of iron on histochemical staining. We interpret this finding as the effect of embedding, sectioning and staining procedures. These processes likely affected the histopathological analysis results but not the magnetic resonance imaging that was obtained before tissue manipulations. Several cellular sources of iron were identified. These sources included oligodendrocytes in normal-appearing white matter and activated macrophages/microglia at the edges of white matter lesions. Additionally, in white matter lesions, iron precipitation in aggregates typical of microbleeds was shown by the Perl's staining. Our combined imaging and pathological study shows that multi-gradient echo magnetic resonance imaging is a sensitive technique for the identification of iron in the brain tissue of patients with multiple sclerosis. However, magnetic resonance imaging-identified iron does not necessarily reflect pathology and may also be seen in apparently normal tissue. Iron identification by multi-gradient echo magnetic resonance imaging in diseased tissues can shed light on the pathological processes when coupled with topographical information and patient disease history.

Hametner, Simon; Yao, Bing; van Gelderen, Peter; Merkle, Hellmut; Cantor, Fredric K.; Lassmann, Hans; Duyn, Jeff H.

2011-01-01

314

LANSCE-R WIRE-SCANNER SYSTEM  

SciTech Connect

The National Instruments cRIO platform is used for the new LANSCE-R wire-scanner systems. All wire-scanner electronics are integrated into a single BiRa BiRIO 4U cRIO chassis specifically designed for the cRIO crate and all interface electronics. The BiRIO chassis, actuator and LabVIEW VIs provide a complete wire-scanner system integrated with EPICS. The new wire-scanner chassis includes an 8-slot cRIO crate with Virtex-5 LX 110 FPGA and Power-PC real-time controller, the LANL-developed cRIO 2-axis wire-sensor analog interface module (AFE), NI9222 cRIO 4-channel 16-bit digitizer, cRIO resolver demodulator, cRIO event receiver, front-panel touch panel display, motor driver, and all necessary software, interface wiring, connectors and ancillary components. This wirescanner system provides a complete, turn-key, 2-axis wire-scanner system including 2-channel low-noise sensewire interface with variable DC wire bias and wireintegrity monitor, 16-bit signal digitizers, actuator motor drive and control, actuator position sensing, limit-switch interfaces, event receiver, LabVIEW and EPICS interface, and both remote operation and full stand-alone operation using the touch panel.

Gruchalla, Michael E. [Los Alamos National Laboratory

2011-01-01

315

Cognition for robot scanner based remote welding  

NASA Astrophysics Data System (ADS)

The effort for reduced cycle times in manufacturing has supported the development of remote welding systems which use a combination of scanners for beam delivery and robots for scanner positioning. Herein, close coupling of both motions requires a precise command of the robot trajectory and the scanner positioning to end up with a combined beam delivery. Especially the path precision of the robot plays a vital role in this kinematic chain. In this paper, a sensor system is being presented which allows tracking the motion of the laser beam against the work piece. It is based on a camera system which is coaxially connected to the scanner thus observing the relative motion of the laser beam relative to the work piece. The acquired images are processed with computer vision algorithms from the field of motion detection. The suitability of the algorithms is being demonstrated with a motion tracking tool which visualizes the homogeneity of the tracking result. The reported solution adds cognitive capabilities to manufacturing systems for robot scanner based materials processing. It allows evaluation of the relative motion between work piece and the laser beam. Moreover, the system can be used to adapt system programming during set-up of a manufacturing task or to evaluate the functionality of a manufacturing system during production. The presented sensor system will assist in optimizing manufacturing processes.

Thombansen, U.; Ungers, Michael

2014-02-01

316

Calorimetric calibration of head coil SAR estimates displayed on a clinical MR scanner  

NASA Astrophysics Data System (ADS)

Calorimetric measurements were performed to determine the average specific absorption rates (SAR) resulting from MRI head examinations. The data were compared with average head coil SAR estimates displayed by the MR scanner in order to refine the imaging protocols used in imaging patients with implanted deep brain stimulators (DBS). The experiments were performed using transmit-receive (TR) head coil on clinical 1.5 T General Electric MR scanners running 11.0 M4 revision software. The average applied SAR was derived from temperature increases measured inside a head phantom, due to deposition of RF energy during MRI scanning with a spin echo imaging sequence. The measurements were repeated for varied levels of RF transmit gain (TG) and analyzed with a range of entered patient weights. The measurements demonstrate that the ratio of the actual average head SAR to the scanner-displayed value (coil correction factor) decreases for decreasing TG or for increasing patient weight and may vary between 0.3 and 2.1. An additional retrospective patient study, however, shows that not all combinations of TG and patient weight are encountered clinically and, instead, TG generally increases with the patient weight. As a result, a much narrower range of coil correction factors (e.g., typically 0.5-1.0) will be encountered in practice. The calorimetric method described in this work could aid the physicians and technologists in refinement of the model-dependent SAR estimates displayed by the MR scanner, and in selection of imaging parameters for MR head examinations within allowable SAR safety levels.

Gorny, Krzysztof R.; Bernstein, Matt A.; Felmlee, Joel P.; Ward, Heidi A.; McGee, Kiaran P.; Lanners, Diana M.; Lee, Kendall H.

2008-05-01

317

PET and MRI: The Odd Couple or a Match Made in Heaven?  

PubMed Central

Positron emission tomography (PET) and magnetic resonance imaging (MRI) are imaging modalities routinely used for clinical and research applications. Integrated scanners capable of acquiring PET and MRI data in the same imaging session, sequentially or simultaneously, have recently become available for human use. In this manuscript, we describe some of the technical advances that allowed the development of human PET/MR scanners, briefly discuss methodological challenges and opportunities provided by this novel technology and present potential oncologic, cardiac, and neuro-psychiatric applications. These examples range from studies that might immediately benefit from PET/MR to more advanced applications where future development might have an even broader impact.

Catana, Ciprian; Guimaraes, Alexander R.; Rosen, Bruce R.

2013-01-01

318

CT densitometry of the lungs: Scanner performance  

SciTech Connect

Our goal was to establish the reproducibility and accuracy of the CT scanner in densitometry of the lungs. Scanner stability was assessed by analysis of daily quality checks. Studies using a humanoid phantom and polyethylene foams for lung were performed to measure reproducibility and accuracy. The dependence of the CT-estimated density on reconstruction filter, zoom factor, slice thickness, table height, data truncation, and objects outside the scan field was determined. Stability of the system at air density was within {approx}1 HU and at water density within {approx}2 HU. Reproducibility and accuracy for densities found for lung were within 2-3%. Dependence on the acquisition and reconstruction parameters was neglible, with the exceptions of the ultra high resolution reconstruction algorithm in the case of emphysema, and objects outside the scan field. The performance of the CT scanner tested is quite adequate for densitometry of the lungs. 26 refs., 5 figs., 4 tabs.

Kemerink, G.J.; Lamers, R.J.S.; Thelissen, G.R.P.; Engelshoven, J.M.A. van [University Hospital, Maastricht (Netherlands)] [University Hospital, Maastricht (Netherlands)

1996-01-01

319

Sonography and MRI of experimental muscle injuries.  

PubMed

After sonographical examination with a 7.5-MHz linear array scanner, we created an experimental muscle injury of known site and location on 28 New Zealand white rabbits by stabbing them with a scalpel in the supraspinatus muscle. The changes in the healing process were followed and documented by sonography and magnetic resonance imaging (MRI) before and 2, 5, 11, 14, 36 and 64 days after injury. The changes in sonography and MRI followed a regular course. Ultrasound revealed an echo-poor area after injury with ever increasing echogenicity from the 14th day. Strong reflexes were found after 2 months. MRI showed few changes, only a slight increase of signal intensity, but a characteristic curve of calculated T2-times (a program of the MRI software). The interpretation of the sonographical picture in histopathological terms remained limited. The development of a hematoma and of fibrous scars can be followed up by sonography, but it is not possible to determine the point of time after injury very accurately. Nevertheless, sonography is a method of great value in the diagnosis of muscle injuries and, given certain limits, in the follow-up of the healing process, too. The significance of MRI can be increased by calculations with the implemented software, as in our study calculated T2-times produced a characteristic curve reflecting the shift of fluids after muscle injury. PMID:9266041

Küllmer, K; Sievers, K W; Rompe, J D; Nägele, M; Harland, U

1997-01-01

320

A versatile thermostatted glass tube MRI rheometer  

NASA Astrophysics Data System (ADS)

A glass tube rheometer optimized for use with a magnetic resonance imaging (MRI) scanner has been developed. Mounted on a trolley, its `plug-and-play' design allows flow- and temperature-equilibria to be attained before the rheometer is inserted in the magnet without disruption of the flow of fluids. Design principles, construction details and rheological test results for water, and aqueous solutions of sucrose (50% w/w) and xanthan gum (0.5% w/w) are presented. Results for water and aqueous sucrose in the temperature range 10-60 °C, which showed that measured shear viscosity was independent of the radial position, demonstrate that the temperature control is reliable. The good agreement of MRI measured viscosities with those produced by classical rheometry indicates the accuracy of the MRI rheometer. Results for 0.5% w/w aqueous xanthan gum reveal an initial time dependency before the flow reached a steady state. The initial time dependency was predominant for the fluid flowing in the central region of the tube; in contrast, the flow in the region near the wall showed the time-independent characteristic of power law fluid. Comparisons with data from cone-and-plate rheometry demonstrate the complementary power of MRI for studies of rheologically complex fluids; importantly, the MRI method can be used to measure the effects of `shear history' on the flow rheology.

Sun, Li; Gao Amin, M. H.; Hall, Laurie D.; Wolf, Bettina; Frith, William J.; Ablett, Steve

1999-12-01

321

High precision kinematic surveying with laser scanners  

NASA Astrophysics Data System (ADS)

The kinematic survey of roads and railways is becoming a much more common data acquisition method. The development of the Mobile Road Mapping System (MoSES) has reached a level that allows the use of kinematic survey technology for high precision applications. The system is equipped with cameras and laser scanners. For high accuracy requirements, the scanners become the main sensor group because of their geometric precision and reliability. To guarantee reliable survey results, specific calibration procedures have to be applied, which can be divided into the scanner sensor calibration as step 1, and the geometric transformation parameter estimation with respect to the vehicle coordinate system as step 2. Both calibration steps include new methods for sensor behavior modeling and multisensor system integration. To verify laser scanner quality of the MoSES system, the results are regularly checked along different test routes. It can be proved that a standard deviation of 0.004 m for height of the scanner points will be obtained, if the specific calibrations and data processing methods are applied. This level of accuracy opens new possibilities to serve engineering survey applications using kinematic measurement techniques. The key feature of scanner technology is the full digital coverage of the road area. Three application examples illustrate the capabilities. Digital road surface models generated from MoSES data are used, especially for road surface reconstruction tasks along highways. Compared to static surveys, the method offers comparable accuracy at higher speed, lower costs, much higher grid resolution and with greater safety. The system's capability of gaining 360 profiles leads to other complex applications like kinematic tunnel surveys or the precise analysis of bridge clearances.

Gräfe, Gunnar

2007-12-01

322

LANSCE Wire Scanner System Prototype: Switchyard Test  

SciTech Connect

On November 19, 2011, the beam diagnostics team of Los Alamos National Laboratory's LANSCE accelerator facility conducted a test of a prototype wire scanner system for future deployment within the accelerator's switchyard area. The primary focus of this test was to demonstrate the wire scanner control system's ability to extend its functionality beyond acquiring lower energy linac beam profile measurements to acquiring data in the switchyard. This study summarizes the features and performance characteristics of the electronic and mechanical implementation of this system with details focusing on the test results.

Sedillo, James D [Los Alamos National Laboratory

2012-04-11

323

The conical scanner evaluation system design  

NASA Technical Reports Server (NTRS)

The software design for the conical scanner evaluation system is presented. The purpose of this system is to support the performance analysis of the LANDSAT-D conical scanners, which are infrared horizon detection attitude sensors designed for improved accuracy. The system consists of six functionally independent subsystems and five interface data bases. The system structure and interfaces of each of the subsystems is described and the content, format, and file structure of each of the data bases is specified. For each subsystem, the functional logic, the control parameters, the baseline structure, and each of the subroutines are described. The subroutine descriptions include a procedure definition and the input and output parameters.

Cumella, K. E.; Bilanow, S.; Kulikov, I. B.

1982-01-01

324

Bone mineral computation with a rectilinear scanner  

NASA Technical Reports Server (NTRS)

A portable rectilinear transmission scanner and associated computerized data reduction techniques for estimating bone mineral content are described. This unit can be easily disassembled for transport to various measurement sites and has been used to estimate the bone mineral content of the os calcis, radius, and ulna in the Apollo and Skylab astronauts. The scanner is used to obtain multiple rows of data from which a bone profile is derived. Bone edges are determined with the aid of a digital computer program which employs an algorithm that determines the greatest rate of change of the counting rate.

Ullman, J.; Brown, S.; Silverstein, A.; Vogel, J. M.

1974-01-01

325

Miniature rotating transmissive optical drum scanner  

NASA Technical Reports Server (NTRS)

A miniature rotating transmissive optical scanner system employs a drum of small size having an interior defined by a circumferential wall rotatable on a drum axis, an optical element positioned within the interior of the drum, and a light-transmissive lens aperture provided at an angular position in the circumferential wall of the drum for scanning a light beam to or from the optical element in the drum along a beam azimuth angle as the drum is rotated. The miniature optical drum scanner configuration obtains a wide scanning field-of-view (FOV) and large effective aperture is achieved within a physically small size.

Lewis, Robert (Inventor); Parrington, Lawrence (Inventor); Rutberg, Michael (Inventor)

2013-01-01

326

Play the MRI Game  

MedlinePLUS

... Teachers' Questionnaire MRI Play MRI the Magnetic Miracle Game About the game In the MRI imaging technique, strong magnets and ... last will in Paris. Play the Blood Typing Game Try to save some patients and learn about ...

327

MRI in France: the French paradox.  

PubMed

Although France is a modern, developed country, which spends nearly 10% of the gross national product on healthcare and has a highly praised level of medicine, the number of modern imaging scanners, such as CT (595), MRI (182), and PET (5), is quite low when compared to other European countries. Politics and a long-standing tradition of centralization are prominent among reasons for such an underdevelopment. This situation has resulted in another French paradox not linked to wine consumption. The French life expectancy is very high, but the number of imaging equipment is very low. PMID:11276096

Lavayssière, R; Cabée, A E

2001-04-01

328

A 10 tesla table-top controlled waveform magnet.  

PubMed

Controlled waveform magnets (CWMs) are a class of pulsed magnets whose pulse shape with time can be programmed by the user. With a CWM, the user gains control not only over the magnitude of the field but also over its rate of change. In this work we present a table-top CWM, driven by a capacitor bank, capable of producing virtually any user-shaped magnetic field waveform up to 10 tesla. Insulated gate bipolar transistor chips have been paralleled to form the high current switch and paralleled chips of SiC Schottky diodes form the crowbar diode module. Sample controlled waveforms including flat-tops up to 10 tesla and some triangular magnetic field pulses have been successfully generated for 10-20 ms with a ripple <1%. PMID:22559572

Roy Choudhury, Aditya N; Venkataraman, V

2012-04-01

329

A 10 tesla table-top controlled waveform magnet  

NASA Astrophysics Data System (ADS)

Controlled waveform magnets (CWMs) are a class of pulsed magnets whose pulse shape with time can be programmed by the user. With a CWM, the user gains control not only over the magnitude of the field but also over its rate of change. In this work we present a table-top CWM, driven by a capacitor bank, capable of producing virtually any user-shaped magnetic field waveform up to 10 tesla. Insulated gate bipolar transistor chips have been paralleled to form the high current switch and paralleled chips of SiC Schottky diodes form the crowbar diode module. Sample controlled waveforms including flat-tops up to 10 tesla and some triangular magnetic field pulses have been successfully generated for 10-20 ms with a ripple <1%.

Roy Choudhury, Aditya N.; Venkataraman, V.

2012-04-01

330

The TESLA test facility FEL: Specifications, status and time schedule  

SciTech Connect

The TESLA Test Facility (TTF) FEL is a user facility under construction at DESY in Hamburg. The radiation wavelength will reach 6 nm, not including the planned higher harmonic radiation generated in a 1 to 1.5 meter long radiator, at a power level of several GW. Specific to the FEL are the low emittance photo injector gun, the bunch compressors, and the undulator with integrated FODO lattice.

Faatz, B. [Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, 22603 Hamburg (Germany)

1997-06-01

331

A Proposal for a TESLA Accelerator Module Test Facility  

Microsoft Academic Search

The Tera-eV Energy Superconducting Linear Accelerator (TESLA), a 32 km long superconducting linear electron\\/positron collider of 500 GeV (upgradeable to 800 GeV) centre of mass energy, presently in the planning phase at DESY, will consist of about 21000 superconducting RF-9-cell cavities of pure Niobium, cooled in a 2.0 K helium bath. The cavities will be assembled in groups of 12

W. D. Moeller; B. Petersen; B. Sparr; Elektronen Synchrotron

332

Field Quality Measurements of a 2Tesla Transmission Line Magnet  

Microsoft Academic Search

A prototype 2-Tesla superconducting transmission line magnet for future hadron colliders was designed, built and tested at Fermilab. The 1.5 m long, combined-function gradient-dipole magnet has a vertical pole aperture of 20 mm. To measure the magnetic field quality in such a small magnet aperture, a specialized rotating coil of 15.2 mm diameter, 0.69 m long was fabricated. Using this

G. V. Velev; W. Foster; V. Kashikhin; P. Mazur; A. Oleck; H. Piekarz; P. Schlabach; C. Sylvester; M. Wake

2006-01-01

333

Performance of external and internal coil configurations for prostate investigations at 7 Tesla  

PubMed Central

Three different coil configurations were evaluated through simulation and experimentally to determine safe operating limits and evaluate subject size dependent performance for prostate imaging at 7 Tesla. The coils included a transceiver endorectal coil (trERC), a 16 channel transceiver external surface array (trESA) and a trESA combined with a receive-only ERC (trESA+roERC). While the transmit B1 (B1+) homogeneity was far superior for the trESA, the maximum achievable B1+ is subject size dependent and limited by transmit chain losses and amplifier performance. For the trERC, limitations in transmit homogeneity greatly compromised image quality and limited coverage of the prostate. Despite these challenges, the high peak B1+ close to the trERC and subject size independent performance provides potential advantages especially for spectroscopic localization where high bandwidth RF pulses are required. On the receive side, the combined trESA+roERC provided the highest SNR and improved homogeneity over the trERC resulting in better visualization of the prostate and surrounding anatomy. In addition, the parallel imaging performance of the trESA+roERC holds strong promise for diffusion weighted imaging and dynamic contrast enhanced MRI.

Metzger, Gregory J.; van de Moortele, Pierre-Francois; Akgun, Can; Snyder, Carl J.; Moeller, Steen; Strupp, John; Andersen, Peter; Shrivastava, Devashish; Vaughan, Tommy; Ugurbil, Kamil; Adriany, Gregor

2010-01-01

334

RHQT Nb3Al 15-Tesla magnet design study  

SciTech Connect

Feasibility study of 15-Tesla dipole magnets wound with a new copper stabilized RHQT Nb{sub 3}Al Rutherford cable is presented. A new practical long copper stabilized RHQT Nb{sub 3}Al strand is presented, which is being developed and manufactured at the National Institute of Material Science (NIMS) in Japan. It has achieved a non-copper J{sub c} of 1000A/mm{sup 2} at 15 Tesla at 4.2K, with a copper over non-copper ratio of 1.04, and a filament size less than 50 microns. For this design study a short Rutherford cable with 28 Nb{sub 3}Al strands of 1 mm diameter will be fabricated late this year. The cosine theta magnet cross section is designed using ROXIE, and the stress and strain in the coil is estimated and studied with the characteristics of the Nb{sub 3}Al strand. The advantages and disadvantages of the Nb{sub 3}Al cable are compared with the prevailing Nb{sub 3}Sn cable from the point of view of stress-strain, J{sub c}, and possible degradation of stabilizer due to cabling. The Nb{sub 3}Al coil of the magnet, which will be made by wind and react method, has to be heat treated at 800 degree C for 10 hours. As preparation for the 15 Tesla magnet, a series of tests on strand and Rutherford cables are considered.

Yamada, R.; Ambrosio, G.; Barzi, E.; Kashikin, V.; Kikuchi, A.; Novitski, I.; Takeuchi, T.; Wake, M.; Zlobin, A.; /Fermilab /NIMC, Tsukuba /KEK, Tsukuba

2005-09-01

335

MRI and Localized Proton Spectroscopy in Human Leg Muscle at 7 Tesla Using Longitudinal Traveling Waves  

PubMed Central

Using a small resonant loop to produce a longitudinal traveling wave on a human 7-T system allows MR to be performed over the entire volume of the human leg. We have used this capability to perform localized proton MR spectroscopy of the lipid composition of muscle in volunteers with a coil placed ~30 cm away from the region of interest. Spectra with a reasonable signal-to-noise ratio can be acquired in a clinically relevant data acquisition time of less than 5 min using the loop in transmit/receive mode, maintaining the full flexibility to acquire spectra from any part of the calf and/or thigh. If a local receive coil is used in combination with the remote transmit coil, then the signal-to-noise improves significantly, as expected.

Webb, Andrew G.; Collins, Christopher M.; Versluis, Maarten J.; Kan, Hermien E.; Smith, Nadine B.

2010-01-01

336

Brain MRI in fetuses with cardiac tumours.  

PubMed

Tuberous sclerosis complex (TSC) is an autosomal dominant multisystem disorder which affects the skin, brain, heart and other organs. It is caused by mutations of two genes: TSC1 (on chromosome 9q34) or TSC2 (on 16p13.3). 70% of cases are sporadic with new mutations. This study aimed to highlight the utility of prenatal MRI as an adjunct imaging modality in the diagnosis and prognosis of tuberous sclerosis complex. Prenatal ultrasound and magnetic resonance imaging were performed in seven fetuses at a gestational age of 30, 32, 34 and 35 weeks using a 1.5 T MRI scanner. SSFSE,T2- and FGRE/T1-weighted images were obtained in axial, coronal and sagittal planes. Postnatal MRI was performed in two cases. Intracardiac tumors (rhabdomyomas) were revealed on ultrasound in all fetuses. On sonographic examination the brain tissue appeared normal in all cases. Brain MRI revealed focal low-signal-intensity lesions, localized along the walls of the lateral ventricles of five fetuses. Another hypointense lesion was seen at the grey/white matter junction in one case. Brain MRI of two fetuses was normal. The diagnosis of TSC was established in five cases. Postnatal MRI in two cases confirmed prenatal findings. MRI allows more complete evaluation of the fetus and helps to determine the diagnosis and prognosis in cases of TSC. The use of prenatal MR imaging in addition to prenatal sonography has the potential to improve genetic counseling and prenatal diagnosis of patients with tuberous sclerosis. PMID:24299935

Jurkiewicz, E; Bekiesi?ska-Figatowska, M; Romaniuk-Doroszewska, A; Dangel, J

2007-10-31

337

Calibration of ocean color temperature scanner (OCTS)  

Microsoft Academic Search

The calibration results of the Ocean Color Temperature Scanner (OCTS) onboard the Japanese Advanced Earth Observing Satellite (ADEOS) are presented in this paper. The goal of OCTS is to measure the geophysical quantities of the ocean (Chlorophyll?a concentration, pigment concentration, etc.). They are calculated from the measured radiance by correcting molecular and aerosol scattering components, so the highly accurate calibration

Hiromi Oaku; Masanobu Shimada; Yasushi Mitomi; Yuji Miyachi; Robert O. Green

1997-01-01

338

Characterization of color scanners based on SVR  

NASA Astrophysics Data System (ADS)

By researching the principle of colorimetric characterization method and Support Vector Regression (SVR), we analyze the feasibility of nonlinear transformation from scanner RGB color space to CIELAB color space based on SVR and built a new characterization model. Then we use the MATLABR2009a software to make a data simulation experiment to verify the accuracy of this model and figure out the color differences by CIEDE2000 color difference formula. Based on CIEDE2000 color difference formula, the average, the maximum and the minimum color differences of the training set are 1.2376, 2.5593 and 0.2182, the average, the maximum and the minimum color differences of the text set are 1.9318, 4.1421 and 0.4228. From the experimental results, we can make a conclusion that SVR can realize the nonlinear transformation from scanner RGB color space to CIELAB color space and the model satisfies the accuracy of scanner characterization. Therefore, SVR can be used into the color scanner characterization management.

Li, Bin; Zhang, Yi-Xin

2012-01-01

339

Miniature 'Wearable' PET Scanner Ready for Use  

ScienceCinema

Scientists from BNL, Stony Brook University, and collaborators have demonstrated the efficacy of a "wearable," portable PET scanner they've developed for rats. The device will give neuroscientists a new tool for simultaneously studying brain function and behavior in fully awake, moving animals.

340

Wire scanner software and firmware issues  

SciTech Connect

The Los Alamos Neutron Science Center facility presently has 110 slow wire scanning profile measurement instruments located along its various beam lines. These wire scanners were developed and have been operating for at least 30 years. While the wire scanners solved many problems to operate and have served the facility well they have increasingly suffered from several problems or limitations, such as maintenance and reliability problems, antiquated components, slow data acquisition, and etc. In order to refurbish these devices, these wire scanners will be replaced with newer versions. The replacement will consist of a completely new beam line actuator, new cables, new electronics and brand new software and firmware. This note describes the functions and modes of operation that LabVIEW VI software on the real time controller and FPGA LabVIEW firmware will be required. It will be especially interesting to understand the overall architecture of these LabVIEW VIs. While this note will endeavor to describe all of the requirements and issues for the wire scanners, undoubtedly, there will be missing details that will be added as time progresses.

Gilpatrick, John Doug [Los Alamos National Laboratory

2008-01-01

341

TIMS (Thermal Infrared Multispectral Scanner) Instrument.  

National Technical Information Service (NTIS)

The scan head and spectrometer of the Thermal Infrared Multispectral Scanner (TIMS) are mounted in the unpressurized tail cone of a NASA/NSTL Learjet and operated through a hole cut through the skin. Design criteria are discussed. The digitized field of v...

C. Stanich

1986-01-01

342

Current segmented gamma-ray scanner technology  

SciTech Connect

A new generation of segmented gamma-ray scanners has been developed at Los Alamos for scrap and waste measurements at the Savannah River Plant and the Los Alamos Plutonium Facility. The new designs are highly automated and exhibit special features such as good segmentation and thorough shielding to improve performance.

Bjork, C.W.

1987-01-01

343

A Microprocessor-Based Control Event Scanner.  

National Technical Information Service (NTIS)

The Control Event Scanner (CES) is a microprocessor-based device which will control and sense relay contract closures via the IEEE Standard 488-1975 Interface Bus, hereafter known as the General Purpose Interface Bus (GPIB). Through the use of a microcomp...

J. R. Hammer M. D. Verstegen

1979-01-01

344

Miniature 'Wearable' PET Scanner Ready for Use  

SciTech Connect

Scientists from BNL, Stony Brook University, and collaborators have demonstrated the efficacy of a "wearable," portable PET scanner they've developed for rats. The device will give neuroscientists a new tool for simultaneously studying brain function and behavior in fully awake, moving animals.

Paul Vaska

2011-03-09

345

A Slide Scanner Input for Paramatrix.  

National Technical Information Service (NTIS)

A special purpose flying-spot slide scanner was designed to provide an efficient and flexible means for transmitting an input pattern to Paramatrix, a pattern processing computer. The light spot of a CRT is positioned by the 'horizontal' and 'vertical' ou...

L. D. Ryan

1967-01-01

346

Miniature 'Wearable' PET Scanner Ready for Use  

ScienceCinema

Scientists from BNL, Stony Brook University, and collaborators have demonstrated the efficacy of a "wearable," portable PET scanner they've developed for rats. The device will give neuroscientists a new tool for simultaneously studying brain function and behavior in fully awake, moving animals.

Paul Vaska

2013-07-22

347

23. SITE BUILDING 002 SCANNER BUILDING RADAR CONTROL ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

23. SITE BUILDING 002 - SCANNER BUILDING - RADAR CONTROL INTERFACE "RCL NO. 2" WITH COMPUTER CONTROL DISC DRIVE UNITS IN FOREGROUND. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

348

2. SITE BUILDING 002 SCANNER BUILDING VIEW IS ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. SITE BUILDING 002 - SCANNER BUILDING - VIEW IS LOOKING NORTH 80° WEST "B" FACE ALONG BUILDING "A" FACE. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

349

1. SITE BUILDING 022 SCANNER BUILDING VIEW IS LOOKING ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. SITE BUILDING 022- SCANNER BUILDING - VIEW IS LOOKING NORTH 70°WEST AT "B" AND "A" FACES. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

350

4. SITE BUILDING 002 SCANNER BUILDING SOUTH 30° ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

4. SITE BUILDING 002 - SCANNER BUILDING - SOUTH 30° WEST - VIEW IS LOOKING AT "B" FACE. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

351

3. SITE BUILDING 002 SCANNER BUILDING VIEW IS ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

3. SITE BUILDING 002 - SCANNER BUILDING - VIEW IS LOOKING NORTH 30° WEST AT "A" FACE. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

352

11. SITE BUILDING 002 SCANNER BUILDING EVAPORATIVE COOLING ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

11. SITE BUILDING 002 - SCANNER BUILDING - EVAPORATIVE COOLING TOWER SYSTEM IN FOREGROUND. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

353

18. SITE BUILDING 002 SCANNER BUILDING VIEW OF ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

18. SITE BUILDING 002 - SCANNER BUILDING - VIEW OF SITE SECURITY OFFICE ACCESS DOOR FROM EXTERIOR OF OFFICE. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

354

22. SITE BUILDING 002 SCANNER BUILDING RADAR CONTROL ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

22. SITE BUILDING 002 - SCANNER BUILDING - RADAR CONTROL ROOM. RECEIVER EQUIPMENT ON RIGHT WITH RF RADIATION MONITOR CABINET. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

355

31. SITE BUILDING 002 SCANNER BUILDING AT INTERIOR ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

31. SITE BUILDING 002 - SCANNER BUILDING AT INTERIOR - BACK OF POWER SUPPLY UNITS 3045-17 AND 3046-29. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

356

28. SITE BUILDING 002 SCANNER BUILDING AT INTERIOR ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

28. SITE BUILDING 002 - SCANNER BUILDING - AT INTERIOR OF LEVEL 5, FACE A - SHOWS ANTENNA RECEIVERS, EMITTERS/RECEIVERS, IN GENERAL ARRANGEMENT. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

357

13. SITE BUILDING 002 SCANNER BUILDING "B" FACE ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

13. SITE BUILDING 002 - SCANNER BUILDING - "B" FACE LOADING DOCK AND PERSONNEL ACCESS RAMP TO FALLOUT SHELTER. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

358

33. SITE BUILDING 002 SCANNER BUILDING MECHANICAL ROOM ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

33. SITE BUILDING 002 - SCANNER BUILDING - MECHANICAL ROOM 105, VIEW OF CHILLER ROOM MOTOR CONTROL CENTER. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

359

32. SITE BUILDING 002 SCANNER BUILDING MECHANICAL ROOM ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

32. SITE BUILDING 002 - SCANNER BUILDING - MECHANICAL ROOM 105, VIEW OF OPERATIONAL SCHEMATIC OF COOLING SYSTEM LOOPS. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

360

24. SITE BUILDING 002 SCANNER BUILDING OPERATIONS CENTER ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

24. SITE BUILDING 002 - SCANNER BUILDING - OPERATIONS CENTER -- MWOC IN OPEARATION AT 1924 ZULU TIME. 26 OCTOBER, 1999. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

361

Respective interest of T2 mapping and diffusion tensor imaging in assessing porcine knee cartilage with MR at 3 Teslas.  

PubMed

Non-invasive quantitative assessment of articular cartilage integrity is essential for early detection and evaluation of osteoarthritis (OA) and for the follow-up of stem-cell-driven cartilage engineering. In this study, we investigated the feasibility of exploiting diffusion tensor imaging (DTI) on porcine knee joints with a clinical magnetic resonance (MR) scanner to extract micro-structural information in order to complement biochemical information quantified by T2 maps. We propose an MR protocol for quantifying T2 and cartilage microstructure with diffusion MR on a clinical scanner. Preliminary results were obtained on four pig knee joints using a 3 T GE clinical MRI scanner and an 8-channel knee coil array. The measured cartilage volume, T2 values, apparent diffusion coefficient and fractional anisotropy (FA) of femoral and tibial cartilage were respectively 9.8/2.3 mm2, 67.0/56.1 ms, 1.3/1.3×10-3 mm2/s and 0.4/0.3. This new protocol has the potential to be combined in vivo with quantitative assessment of both cartilage degradation and restoration in osteoarthritis. PMID:23798647

Chen, Bailiang; Roeder, Emilie; Vuissoz, Pierre-André; Gillet, Pierre; Felblinger, Jacques; Beaumont, Marine; Pinzano, Astrid

2013-01-01

362

Ratiometric MRI sensors based on core-shell nanoparticles for quantitative pH imaging.  

PubMed

Ratiometric MRI sensors consist of paramagnetic cores and pH-sensitive polymer shells. The core-shell nanostructure enables the coexistence of two incompatible NMR relaxation properties in one particle. The sensors show pH sensitivity in transverse relaxivity (r2 ), but not in longitudinal relaxivity (r1 ). Quantitative pH imaging is achieved by measuring the r2 /r1 value with a clinical 3 T MRI scanner. PMID:24453039

Okada, Satoshi; Mizukami, Shin; Sakata, Takao; Matsumura, Yutaka; Yoshioka, Yoshichika; Kikuchi, Kazuya

2014-05-21

363

BOLD fMRI activation induced by vagus nerve stimulation in seizure patients  

Microsoft Academic Search

Objective: To identify the cerebral activated regions associated with the vagus nerve stimulation in epilepsy patients.Design: Blood oxygenation level dependent functional magnetic resonance imaging (BOLD fMRI) was employed to detect areas of the brain activated by vagus nerve stimulation in five patients with documented complex partial seizures.Methods: Functional MRI was done on a GE 1.5T Echospeed horizon scanner. Before each

W-C Liu; K Mosier; A J Kalnin; D Marks

2003-01-01

364

MRI-Directed Subthalamic Nucleus Surgery for Parkinson’s Disease  

Microsoft Academic Search

The subthalamic nucleus (STN) is now regarded as the optimal surgical target for the treatment of medically refractory idiopathic Parkinson’s disease. In our center, a predominantly MRI-directed method has been developed for targeting the STN. The STN is localized on T2-weighted images from a 1.5-T MRI scanner. Long acquisition, high-resolution images are acquired in both the axial and coronal planes

Nikunj K. Patel; Peter Heywood; Karen O’Sullivan; Seth Love; Steven S. Gill

2002-01-01

365

Convenient synthesis of (68)Ga-labeled gadolinium(III) complexes: towards bimodal responsive probes for functional imaging with PET/MRI.  

PubMed

A killer application? Recently, fully integrated full-body positron-emission tomography (PET) and magnetic-resonance imaging (MRI) scanners were brought to market, allowing simultaneous recording of complementary 3D data sets. By using bimodal PET/MRI probes (see figure), in vivo 3D mapping of various parameters with medical relevance could become feasible. PMID:24175335

Notni, Johannes; Hermann, Petr; Dregely, Isabel; Wester, Hans-Jürgen

2013-09-16

366

Semiconductor Measurement Technology: A Laser Scanner for Semiconductor Devices.  

National Technical Information Service (NTIS)

The report is a construction guide and operators manual for a laser scanner built for semiconductor device studies. A very brief discussion of the theory of operation of the scanner is given. The scanner's operation from a systems point of view is describ...

D. E. Sawyer D. W. Berning

1977-01-01

367

Applications of Optical Scanners in an Academic Center.  

ERIC Educational Resources Information Center

Describes optical scanners, including how the technology works; applications in data management and research; development of instructional materials; and providing community services. Discussion includes the three basic types of optical scanners: optical character recognition (OCR), optical mark readers (OMR), and graphic scanners. A sidebar…

Molinari, Carol; Tannenbaum, Robert S.

1995-01-01

368

Scanner show-through reduction using reflective optics  

NASA Astrophysics Data System (ADS)

Document scanners are used to convert paper documents to digital format for document distribution or archiving. Scanners are also used in copier and fax machine to convert document to electrical signal in analog and digital format. Most document scanners use white backing to avoid black border or black hole in scanned images. One problem with white backing is that show-through from the backside is visible for duplex printed (two sided) documents. This paper describes an optical method to eliminate show-through without reverting back to the black border or black hole. The scanner cover is made into a saw-tooth shaped mirror surface. The surface is oriented so that it reflects the light from the scanner lamp to the scanner lens. When scanning the scanner cover as in the case of a hole in the paper, it reflects light (specular reflection) from the scanner lamp directly to the scanner lens. Because the scanner lamp is much brighter than the reflected light from the document, only a small portion of the reflected light is needed to have the same output as scanning a piece of white paper. Radiometric calculation shows that this new approach can reduce the overall reflection from the scanner cover to 8% when scanning a document, and yet, appear to be white when no document is in between the cover and scan bar. The show-through is greatly reduced due to this reduced overall reflection from the scanner cover.

Feng, Xiao-fan

2003-12-01

369

Comparison of plane extraction performance using laser scanner and Kinect  

Microsoft Academic Search

This paper compares the performance of laser scanner and Kinect when extracting the plane from 3D depth map measured by both sensors. By tilting laser scanner, 3D depth map around robot is generated in this paper and another 3D depth map using Kinect is also generated. To compare the 3D depth map of laser scanner and Kinect, staircases are measured

Chan-Soo Park; Sung-Wan Kim; Doik Kim; Sang-Rok Oh

2011-01-01

370

A new generation of scanners for DNA chips  

Microsoft Academic Search

Today, most of the DNA chips are used with fluorescent markers. Associated with fluorescence confocal scanners, this technology achieves remarkable performances in terms of sensitivity and accuracy. The main technical issues related to these scanners have already been reviewed. However, these scanners are costly, especially when high density chips are used. In this case, a mechanical precision of 1 ?m

François Perraut; Alexandre Lagrange; Patrick Pouteau; O Peyssonneaux; Pierre Puget; G McGall; Lionel Menou; Richard Gonzalez; Pierre Labeye; Frédéric Ginot

2002-01-01

371

Real-time 3D image registration for functional MRI.  

PubMed

Subject head movements are one of the main practical difficulties with brain functional MRI. A fast, accurate method for rotating and shifting a three-dimensional (3D) image using a shear factorization of the rotation matrix is described. Combined with gradient descent (repeated linearization) on a least squares objective function, 3D image realignment for small movements can be computed as rapidly as whole brain images can be acquired on current scanners. Magn Reson Med 42:1014-1018, 1999. PMID:10571921

Cox, R W; Jesmanowicz, A

1999-12-01

372

Prospective screening study of 0.5 Tesla dedicated magnetic resonance imaging for the detection of breast cancer in young, high-risk women  

PubMed Central

Background Evidence-based screening guidelines are needed for women under 40 with a family history of breast cancer, a BRCA1 or BRCA2 mutation, or other risk factors. An accurate assessment of breast cancer risk is required to balance the benefits and risks of surveillance, yet published studies have used narrow risk assessment schemata for enrollment. Breast density limits the sensitivity of film-screen mammography but is not thought to pose a limitation to MRI, however the utility of MRI surveillance has not been specifically examined before in women with dense breasts. Also, all MRI surveillance studies yet reported have used high strength magnets that may not be practical for dedicated imaging in many breast centers. Medium strength 0.5 Tesla MRI may provide an alternative economic option for surveillance. Methods We conducted a prospective, nonrandomized pilot study of 30 women age 25–49 years with dense breasts evaluating the addition of 0.5 Tesla MRI to conventional screening. All participants had a high quantitative breast cancer risk, defined as ? 3.5% over the next 5 years per the Gail or BRCAPRO models, and/or a known BRCA1 or BRCA2 germline mutation. Results The average age at enrollment was 41.4 years and the average 5-year risk was 4.8%. Twenty-two subjects had BIRADS category 1 or 2 breast MRIs (negative or probably benign), whereas no category 4 or 5 MRIs (possibly or probably malignant) were observed. Eight subjects had BIRADS 3 results, identifying lesions that were "probably benign", yet prompting further evaluation. One of these subjects was diagnosed with a stage T1aN0M0 invasive ductal carcinoma, and later determined to be a BRCA1 mutation carrier. Conclusion Using medium-strength MRI we were able to detect 1 early breast tumor that was mammographically undetectable among 30 young high-risk women with dense breasts. These results support the concept that breast MRI can enhance surveillance for young high-risk women with dense breasts, and further suggest that a medium-strength instrument is sufficient for this application. For the first time, we demonstrate the use of quantitative breast cancer risk assessment via a combination of the Gail and BRCAPRO models for enrollment in a screening trial.

Rubinstein, Wendy S; Latimer, Jean J; Sumkin, Jules H; Huerbin, Michelle; Grant, Stephen G; Vogel, Victor G

2006-01-01

373

Fetal Electrocardiogram (fECG) Gated MRI  

PubMed Central

We have developed a Magnetic Resonance Imaging (MRI)-compatible system to enable gating of a scanner to the heartbeat of a foetus for cardiac, umbilical cord flow and other possible imaging applications. We performed radiofrequency safety testing prior to a fetal electrocardiogram (fECG) gated imaging study in pregnant volunteers (n = 3). A compact monitoring device with advanced software capable of reliably detecting both the maternal electrocardiogram (mECG) and fECG simultaneously was modified by the manufacturer (Monica Healthcare, Nottingham, UK) to provide an external TTL trigger signal from the detected fECG which could be used to trigger a standard 1.5 T MR (GE Healthcare, Milwaukee, WI, USA) gating system with suitable attenuation. The MR scanner was tested by triggering rapidly during image acquisition at a typical fetal heart rate (123 beats per minute) using a simulated fECG waveform fed into the gating system. Gated MR images were also acquired from volunteers who were attending for a repeat fetal Central Nervous System (CNS) examination using an additional rapid cardiac imaging sequence triggered from the measured fECG. No adverse safety effects were encountered. This is the first time fECG gating has been used with MRI and opens up a range of new possibilities to study a developing foetus.

Paley, Martyn N.J.; Morris, Janet E.; Jarvis, Debbie; Griffiths, Paul D.

2013-01-01

374

Biomedical applications of a real-time terahertz color scanner  

PubMed Central

A real-time THz color scanner has the potential to further expand the application scope of THz spectral imaging based on its rapid image acquisition rate. We demonstrated three possible applications of a THz color scanner in the biomedical field: imaging of pharmaceutical tablets, human teeth, and human hair. The first application showed the scanner’s potential in total inspection for rapid quality control of pharmaceutical tablets moving on a conveyor belt. The second application demonstrated that the scanner can be used to identify a potential indicator for crystallinity of dental tissue. In the third application, the scanner was successfully used to visualize the drying process of wet hairs. These demonstrations indicated the high potential of the THz color scanner for practical applications in the biomedical field.

Schirmer, Markus; Fujio, Makoto; Minami, Masaaki; Miura, Jiro; Araki, Tsutomu; Yasui, Takeshi

2010-01-01

375

Telescope with a wide field of view internal optical scanner  

NASA Technical Reports Server (NTRS)

A telescope with internal scanner utilizing either a single optical wedge scanner or a dual optical wedge scanner and a controller arranged to control a synchronous rotation of the first and/or second optical wedges, the wedges constructed and arranged to scan light redirected by topological surfaces and/or volumetric scatterers. The telescope with internal scanner further incorporates a first converging optical element that receives the redirected light and transmits the redirected light to the scanner, and a second converging optical element within the light path between the first optical element and the scanner arranged to reduce an area of impact on the scanner of the beam collected by the first optical element.

Degnan, III, John James (Inventor); Zheng, Yunhui (Inventor)

2012-01-01

376

Ghost Signals In Allison Emittance Scanners  

NASA Astrophysics Data System (ADS)

For over 20 years, Allison scanners have been used to measure emittances of low-energy ion beams. We show that scanning large trajectory angles produces ghost signals caused by the sampled beamlet impacting on an electric deflection plate. The ghost signal strength is proportional to the amount of beam entering the scanner. Depending on the ions, and their velocity, the ghost signals can have the opposite or the same polarity as the main beam signals. The ghost signals cause significant errors in the emittance estimates because they appear at large trajectory angles. These ghost signals often go undetected because they partly overlap with the real signals, are mostly below the 1% level, and often hide in the noise. A simple deflection plate modification is shown to reduce the ghost signal strength by over 99%.

Stockli, Martin P.; Leitner, M.; Moehs, D. P.; Keller, R.; Welton, R. F.

2005-03-01

377

Compact conscious animal positron emission tomography scanner  

DOEpatents

A method of serially transferring annihilation information in a compact positron emission tomography (PET) scanner includes generating a time signal for an event, generating an address signal representing a detecting channel, generating a detector channel signal including the time and address signals, and generating a composite signal including the channel signal and similarly generated signals. The composite signal includes events from detectors in a block and is serially output. An apparatus that serially transfers annihilation information from a block includes time signal generators for detectors in a block and an address and channel signal generator. The PET scanner includes a ring tomograph that mounts onto a portion of an animal, which includes opposing block pairs. Each of the blocks in a block pair includes a scintillator layer, detection array, front-end array, and a serial encoder. The serial encoder includes time signal generators and an address signal and channel signal generator.

Schyler, David J. (Bellport, NY); O'Connor, Paul (Bellport, NY); Woody, Craig (Setauket, NY); Junnarkar, Sachin Shrirang (Sound Beach, NY); Radeka, Veljko (Bellport, NY); Vaska, Paul (Sound Beach, NY); Pratte, Jean-Francois (Stony Brook, NY); Volkow, Nora (Chevy Chase, MD)

2006-10-24

378

Viewing One's Own Face Being Touched Modulates Tactile Perception: An fMRI Study  

Microsoft Academic Search

The perception of tactile stimuli on the face is modulated if subjects concurrently observe a face being touched; this effect, termed visual remapping of touch (VRT), is maximum for observing one's own face. In the present fMRI study, we investigated the neural basis of the VRT effect. Participants in the scanner received tactile stimuli, near the perceptual threshold, on their

Flavia Cardini; Marcello Costantini; Gaspare Galati; Gian Luca Romani; Elisabetta Làdavas; Andrea Serino

2011-01-01

379

Automated quality assurance routines for fMRI data applied to a multicenter study  

Microsoft Academic Search

Standard procedures to achieve quality assessment (QA) of functional magnetic resonance imaging (fMRI) data are of great importance. A standardized and fully automated procedure for QA is presented that allows for classification of data quality and the detection of artifacts by inspecting temporal variations. The application of the procedure on phantom measurements was used to check scanner and stimulation hardware

Tony Stöcker; Frank Schneider; Martina Klein; Ute Habel; Thilo Kellermann; Karl Zilles; N. Jon Shah

2005-01-01

380

Characterization of transceive surface element designs for 7 tesla magnetic resonance imaging of the prostate: radiative antenna and microstrip  

NASA Astrophysics Data System (ADS)

Ultra-high field magnetic resonance (?7 tesla) imaging (MRI) faces challenges with respect to efficient spin excitation and signal reception from deeply situated organs. Traditional radio frequency surface coil designs relying on near-field coupling are suboptimal at high field strengths. Better signal penetration can be obtained by designing a radiative antenna in which the energy flux is directed to the target location. In this paper, two different radiative antenna designs are investigated to be used as transceive elements, which employ different dielectric permittivities for the antenna substrate. Their transmit and receive performances in terms of B+1, local SAR (specific absorption rate) and SNR (signal-to-noise ratio) were compared using extensive electromagnetic simulations and MRI measurements with traditional surface microstrip coils. Both simulations and measurements demonstrated that the radiative element shows twofold gain in B+1 and SNR at 10 cm depth, and additionally a comparable SAR peak value. In terms of transmit performance, the radiative antenna with a dielectric permittivity of 37 showed a 24% more favorable local SAR10g?avg/(B+1)2 ratio than the radiative antenna with a dielectric permittivity of 90. In receive, the radiative element with a dielectric permittivity of 90 resulted in a 20% higher SNR for shallow depths, but for larger depths this difference diminished compared to the radiative element with a dielectric permittivity of 37. Therefore, to image deep anatomical regions effectively, the radiative antenna with a dielectric permittivity of 37 is favorable.

Ipek, Ö.; Raaijmakers, A. J. E.; Klomp, D. W. J.; Lagendijk, J. J. W.; Luijten, P. R.; van den Berg, C. A. T.

2012-01-01

381

Point Relay Scanner Utilizing Ellipsoidal Mirrors  

NASA Technical Reports Server (NTRS)

A scanning system uses a polygonal mirror assembly with each facet of the polygon having an ellipsoidal mirror located thereon. One focal point of each ellipsoidal mirror is located at a common point on the axis of rotation of the polygonal mirror assembly. As the mirror assembly rotates. a second focal point of the ellipsoidal mirrors traces out a scan line. The scanner can be utilized for scanned output display of information or for scanning information to be detected.

Manhart, Paul K. (Inventor); Pagano, Robert J. (Inventor)

1997-01-01

382

Piezoelectric Transducer Based 3D Intraoral Scanner  

Microsoft Academic Search

There are not so many 3D profile tools specially designed for specifically narrow space, for example, to scan the tooth shape of a human jaw. In this paper, a real-time 3D intraoral scanner based on piezoelectric transducer is presented for the measurement of tooth profile in the mouth cavity. The proposed system comprises a laser diode beam, a micro charge-coupled

Furqan Ullah; Gun Soo Lee; Kang Park

2012-01-01

383

Dynamic Shimming of the Human Brain at 7 Tesla  

PubMed Central

Dynamic shim updating (DSU) of the zero- to second-order spherical harmonic field terms has previously been shown to improve the magnetic field homogeneity in the human brain at 4 Tesla. The increased magnetic field inhomogeneity at 7 Tesla can benefit from inclusion of third-order shims during DSU. However, pulsed higher-order shims can generate a multitude of temporally varying magnetic fields arising from eddy-currents that can strongly degrade the magnetic field homogeneity. The first realization of zero- to third-order DSU with full preemphasis and B0 compensation enabled improved shimming of the human brain at 7 Tesla not only in comparison with global (i.e. static) shimming, but also when compared to state-of-the-art zero- to second-order DSU. Temporal shim-to-shim interactions were measured for each of the 16 zero- to third-order shim coils along 1D column projections on a spherical phantom. The decomposition into up to 3 exponentials allowed full preemphasis and B0 compensation of all 16 shims covering 67 potential shim-to-shim interactions. Despite the significant improvements achievable with DSU, the magnetic field homogeneity is still not perfect even when updating all zero- through third-order shims. This is because DSU is still inherently limited by the shallowness of the low order spherical harmonic fields and their inability to compensate the higher-order inhomogeneities encountered in vivo. However, DSU maximizes the usefulness of conventional shim coil systems and provides magnetic field homogeneity that is adequate for a wide range of applications.

Juchem, Christoph; Nixon, Terence W.; Diduch, Piotr; Rothman, Douglas L.; Starewicz, Piotr; de Graaf, Robin A.

2010-01-01

384

MR imaging of the neonatal brain at 3 Tesla  

Microsoft Academic Search

Summary 3 Telsa MR scanners are now becoming more widely available and 3 Telsa is likely to become the filed strength of choice for clinical imaging of the brain. The neonatal brain can be safely and successfully imaged at 3 Telsa. The improved signal to noise afforded by a higher field strength may be used to improve image quality or

Mary Rutherford; Christina Malamateniou; Julie Zeka; Serena Counsell

2004-01-01

385

A near-infrared confocal scanner  

NASA Astrophysics Data System (ADS)

In the semiconductor industry, manufacturing of three-dimensional (3D) packages or 3D integrated circuits is a high-performance technique that requires combining several functions in a small volume. Through-silicon vias, which are vertical electrical connections extending through a wafer, can be used to direct signals between stacked chips, thus increasing areal density by stacking and connecting multiple patterned chips. While defect detection is essential in the semiconductor manufacturing process, it is difficult to identify defects within a wafer or to monitor the bonding results between bonded surfaces because silicon and many other semiconductor materials are opaque to visible wavelengths. In this context, near-infrared (NIR) imaging is a promising non-destructive method to detect defects within silicon chips, to inspect bonding between chips and to monitor the chip alignment since NIR transmits through silicon. In addition, a confocal scanner provides high-contrast, optically-sectioned images of the specimen due to its ability to reject out-of-focus noise. In this study, we report an NIR confocal scanner that rapidly acquires high-resolution images with a large field of view through silicon. Two orthogonal line-scanning images can be acquired without rotating the system or the specimen by utilizing two orthogonally configured resonant scanning mirrors. This NIR confocal scanner can be efficiently used as an in-line inspection system when manufacturing semiconductor devices by rapidly detecting defects on and beneath the surface.

Lee, Seungwoo; Yoo, Hongki

2014-06-01

386

Radiofrequency artefacts in echoplanar imaging induced by two 1.5?T MR scanners in close proximity.  

PubMed

Objective: The purpose of this study was to assess radio frequency (RF) artefacts in echoplanar imaging (EPI) induced by two 1.5?T MR scanners in close proximity and to find an effective method to correct them. Methods: Based on the intact shielding of rooms, experiments were performed by two MR scanners with similar centre frequencies. Phantom A (PA) was scanned in one scanner by EPI at different bandwidths (BWs). Simultaneously, phantom B was scanned in a fixed sequence for scanning with the other scanner. RF artefact gaps of PA, scanning time and the image signal-noise ratio (SNR) were measured and recorded. Statistical analysis was performed with the repeated-measures analysis of variance test. Based on findings obtained from PA, three healthy volunteers were studied at a conventional BW and a lower BW to observe the artefact variance. Results: EPI RF artefacts were symmetrically situated in both sides of the image following the phase-encoding direction. The gap size of the artefact became larger and the SNR was significantly improved with a narrower BW. RF artefacts with a lower BW in volunteers presented the same characteristic as PA. Conclusion: For EPI RF artefacts produced by two 1.5?T MR scanners with approximately similar centre frequencies, we can reduce BWs in a suitable range to minimize the effect on MRI. Advances in knowledge: MR scanners with the same field strength installed in the same vicinity might produce RF artefacts in the sequence at larger BWs. Reducing BWs properly is effective to control the position of artefacts and improve the image quality. PMID:24712321

Li, X; Cui, J; Christopasak, S P; Kumar, A; Peng, Z-G

2014-06-01

387

Improved surface treatment of the superconducting TESLA cavities  

NASA Astrophysics Data System (ADS)

The proposed linear electron-positron collider TESLA is based on 1.3 GHz superconducting niobium cavities for particle acceleration. For a centre-of-mass energy of 500 GeV, an accelerating field of 23.4 MV/m is required which is reliably achieved with a niobium surface preparation by chemical etching. An upgrade of the collider to 800 GeV requires an improved cavity preparation technique. In this paper, results are presented on single-cell cavities which demonstrate that fields of up to 40 MV/m are accessible by electrolytic polishing of the inner surface of the cavity.

Lilje, L.; Antoine, C.; Benvenuti, C.; Bloess, D.; Charrier, J.-P.; Chiaveri, E.; Ferreira, L.; Losito, R.; Matheisen, A.; Preis, H.; Proch, D.; Reschke, D.; Safa, H.; Schmüser, P.; Trines, D.; Visentin, B.; Wenninger, H.

388

Status of the NHMFL 60 tesla quasi-continuous magnet  

NASA Astrophysics Data System (ADS)

All components of the National High Magnetic Field Laboratory's (NHMFL) 60 T quasi-continuous magnet are now under construction, with complete delivery and installation expected in early 1996. This research magnet has a cold bore of 32 mm and will produce a constant 60 tesla for 100 ms plus a wide variety of other pulse shapes such as linear ramps, steps, crowbar decays, and longer flat-tops at lower fields. Fabrication and testing of prototype coils are described along with the layout, construction status, and protection philosophy of the 400 MW power supply. Examples of simulated pulse shapes are shown.

Campbell, L. J.; Boenig, H. J.; Rickel, D. G.; Schilig, J. B.; Sims, J. R.; Schneider-Muntau, H. J.

389

Diffusion-weighted MRI in a liver protocol: Its role in focal lesion detection  

PubMed Central

AIM: To evaluate the role of diffusion-weighted imaging (DWI) in the detection of focal liver lesions (FLLs), using a conventional magnetic resonance imaging (MRI) protocol. METHODS: Fifty-two patients (22 males, average age 55.6 years, range: 25-82 years), studied using a 1.5 Tesla magnetic resonance scanner, were retrospectively analyzed; detection of FLLs was evaluated by considering the number of lesions observed with the following sequences: (1) respiratory-triggered diffusion-weighted single-shot echo-planar (DW SS-EP) sequences; (2) fat-suppressed fast spin-echo (fs-FSE) T2 weighted sequences; (3) steady-state free precession (SSFP) images; and (4) dynamic triphasic gadolinium-enhanced images, acquired with three-dimensional fast spoiled gradient-echo (3D FSPGR). Two radiologists independently reviewed the images: they were blinded to their respective reports. DW SS-EP sequences were compared to fs-FSE, SSFP and dynamic gadolinium-enhanced acquisitions using a t-test. Pairs were compared for the detection of: (1) all FLLs; (2) benign FLLs; (3) malignant FLLs; (4) metastases; and (5) hepatocellular carcinoma (HCC). RESULTS: Interobserver agreement was very good (weighted ? = 0.926, CI = 0.880-0.971); on the consensus reading, 277 FLLs were detected. In the comparison with fs-FSE, DW SS-EP sequences had a significantly higher score in the detection of all FLLs, benign FLLs, malignant FLLs and metastases; no statistical difference was observed in the detection of hepatocellular carcinoma (HCCs). In the comparison with SSFP sequences, DW SS-EP had significantly higher scores (P < 0.05) in the detection of all lesions, benign lesions, malignant lesions, metastases and HCC. All FLLs were better detected by dynamic 3D FSGR enhanced acquisition, with P = 0.0023 for reader 1 and P = 0.0086 for reader 2 in the comparison with DW SS-EP sequences; with reference to benign FLLs, DW SS-EP showed lower values than 3D FSPGR enhanced acquisition (P < 0.05). No statistical differences were observed in the detection of malignant lesions and metastases; considering HCCs, a very slight difference was reported by reader 1 (P = 0.049), whereas no difference was found by reader 2 (P = 0.06). CONCLUSION: In lesion detection, DWI had higher scores than T2 sequences; considering malignant FLLs, no statistical difference was observed between DWI and dynamic gadolinium images.

Palmucci, Stefano; Mauro, Letizia Antonella; Messina, Martina; Russo, Brunella; Failla, Giovanni; Milone, Pietro; Berretta, Massimiliano; Ettorre, Giovanni Carlo

2012-01-01

390

Cryogenic current comparator for absolute measurements of the dark current of superconducting cavities for TESLA  

Microsoft Academic Search

A new SQUID based measurement system for detecting dark currents, generated by the TESLA (Tera Electron Volt Energy Superconducting Linear Accelerator) cavities is proposed. It makes use of the Cryogenic Current Comparator principle and senses dark currents in the nA range. To reach the maximum possible energy in the TESLA project is a strong motivation to push the gradients of

W. Vodel; R. Neubert; S. Nietzsche; K. Knaack; M. Wendt; K. Wittenburg; A. Peters

2003-01-01

391

A micro Tesla turbine for power generation from low pressure heads and evaporation driven flows  

Microsoft Academic Search

We report on the design, fabrication and testing of a low pressure head Tesla microturbine. We began developing this technology as a means of scavenging energy from fluids flows induced in plant-like evaporative systems. Unlike traditional inertial turbines, Tesla turbines have high efficiency when driven with low pressure flows, are relatively simple to manufacture and scale down very favorably. The

Vedavalli G. Krishnan; Zohora Iqbal; Michel M. Maharbiz

2011-01-01

392

SIXTH INTERNATIONAL SYMPOSIUM NIKOLA TESLA October 18 - 20, 2006, Belgrade, SASA, Serbia  

Microsoft Academic Search

Tesla made several of the most significant discover- ies in electric power systems and wireless signal transmission. These contributions were crucial in enabling economic and tech- nological progress leading to our modern world. In his long crea- tive life, he also impacted many other areas in engineering, sci- ences, medicine, and art. This paper discusses examples of Tesla's work as

D. Ercegovac

393

The TESLA 500 cryogenic system and He II two-phase flow: issues and planned experiments  

Microsoft Academic Search

The cooling system of the proposed TESLA 500 superconducting linac makes extensive use of He II two-phase flow. However, there remain a number of open questions about the expected performance of this unique two-phase flow system. One of the purposes of the TESLA Test Facility (TTF) currently under construction at DESY, is to test the planned cryogenic cooling system for

G. Horlitz; B. Petersen; D. Sellmann; S. W. Van Sciver; J. G. Weisend; S. Wolff

1997-01-01

394

Some aspects of data processing for an optical absorption experiment in a pulsed 1000-Tesla magnet  

SciTech Connect

A procedure is given for the analysis of optical absorption data acquired in the hostile environment of a pulsed 1000-Tesla magnet. The 1000-Tesla magnetic field is achieved with an explosive charge which generates a shock wave that travels toward the sample of octachlorodirhenate.

Butler, L.G.; Maverick, A.W. [Louisiana State Univ., Baton Rouge, LA (United States). Dept. of Chemistry] [Louisiana State Univ., Baton Rouge, LA (United States). Dept. of Chemistry; Gallegos, C.H. [Bechtel-Nevada, Los Alamos, NM (United States)] [Bechtel-Nevada, Los Alamos, NM (United States); Goettee, J.D.; Fowler, C.M.; Rickel, D.G.; Gonzales, J.M.; Tabaka, L.J. [Los Alamos National Lab., NM (United States). National High Magnetic Field Lab.] [Los Alamos National Lab., NM (United States). National High Magnetic Field Lab.; Marshall, B.R. [Bechtel-Nevada, Santa Barbara, CA (United States). Special Technologies Lab.] [Bechtel-Nevada, Santa Barbara, CA (United States). Special Technologies Lab.

1998-11-01

395

A low cost approach to design the Tesla transformer for testing of insulating materials  

Microsoft Academic Search

A high voltage with high frequency oscillation waveshape is used as a standard test for electrical power equipment. A Tesla transformer is one of the sources that can generate such a waveshape. This paper presents a design and a construction of a Tesla transformer used in insulator tests. The output of the transformer has a rate of 200 kV and

C. Boonseng; P. Apiratikul

2001-01-01

396

76 FR 60124 - Tesla Motors, Inc.; Grant of Petition for Temporary Exemption From the Electronic Stability...  

Federal Register 2010, 2011, 2012, 2013

...49 CFR Part 555, Tesla Motors, Inc. (Tesla) submitted...solutions for the Toyota Motor Corporation RAV 4 sport...three phase, four pole AC induction motor. The Roadster has a combined...cites its inclusion of a traction control system...

2011-09-28

397

76 FR 47639 - Tesla Motors, Inc.; Receipt of Petition for Temporary Exemption From the Electronic Stability...  

Federal Register 2010, 2011, 2012, 2013

...evaluation of a low- emission motor vehicle easier and would...49 CFR part 555, Tesla Motors, Inc. (Tesla) submitted...three phase, four pole AC induction motor. The Roadster has a combined...cites its inclusion of a traction control system...

2011-08-05

398

SIXTH INTERNATIONAL SYMPOSIUM NIKOLA TESLA October 18 - 20, 2006, Belgrade, SASA, Serbia  

Microsoft Academic Search

At Electricity Hall, Professor Tesla announces he will send a current of 100,000 volts through his own body without injury to life, an experiment which seems all the more wonderful when we recall the fact that the currents made use of for executing murderers at Sing Sing, N.Y., have never exceeded 2000 volts. Mr. Tesla also shows a number of

Nikola Tesla; John Jacob Astor; Marc J. Seifer

399

Spectral characterization of the LANDSAT-D multispectral scanner subsystems  

NASA Technical Reports Server (NTRS)

Relative spectral response data for the multispectral scanner subsystems (MSS) to be flown on LANDSAT-D and LANDSAT-D backup, the protoflight and flight models, respectively, are presented and compared to similar data for the Landsat 1,2, and 3 subsystems. Channel-bychannel (six channels per band) outputs for soil and soybean targets were simulated and compared within each band and between scanners. The two LANDSAT-D scanners proved to be nearly identical in mean spectral response, but they exhibited some differences from the previous MSS's. Principal differences between the spectral responses of the D-scanners and previous scanners were: (1) a mean upper-band edge in the green band of 606 nm compared to previous means of 593 to 598 nm; (2) an average upper-band edge of 697 nm in the red band compared to previous averages of 701 to 710 nm; and (3) an average bandpass for the first near-IR band of 702-814 nm compared to a range of 693-793 to 697-802 nm for previous scanners. These differences caused the simulated D-scanner outputs to be 3 to 10 percent lower in the red band and 3 to 11 percent higher in the first near-IR band than previous scanners for the soybeans target. Otherwise, outputs from soil and soybean targets were only slightly affected. The D-scanners were generally more uniform from channel to channel within bands than previous scanners.

Markham, B. L. (principal investigator); Barker, J. L.

1982-01-01

400

Recent micro-CT scanner developments at UGCT  

NASA Astrophysics Data System (ADS)

This paper describes two X-ray micro-CT scanners which were recently developed to extend the experimental possibilities of microtomography research at the Centre for X-ray Tomography (www.ugct.ugent.be) of the Ghent University (Belgium). The first scanner, called Nanowood, is a wide-range CT scanner with two X-ray sources (160 kVmax) and two detectors, resolving features down to 0.4 ?m in small samples, but allowing samples up to 35 cm to be scanned. This is a sample size range of 3 orders of magnitude, making this scanner well suited for imaging multi-scale materials such as wood, stone, etc. Besides the traditional cone-beam acquisition, Nanowood supports helical acquisition, and it can generate images with significant phase-contrast contributions. The second scanner, known as the Environmental micro-CT scanner (EMCT), is a gantry based micro-CT scanner with variable magnification for scanning objects which are not easy to rotate in a standard micro-CT scanner, for example because they are physically connected to external experimental hardware such as sensor wiring, tubing or others. This scanner resolves 5 ?m features, covers a field-of-view of about 12 cm wide with an 80 cm vertical travel range. Both scanners will be extensively described and characterized, and their potential will be demonstrated with some key application results.

Dierick, Manuel; Van Loo, Denis; Masschaele, Bert; Van den Bulcke, Jan; Van Acker, Joris; Cnudde, Veerle; Van Hoorebeke, Luc

2014-04-01

401

MRI-guided percutaneous transhepatic cholangiodrainage: feasibility study in a porcine model.  

PubMed

Abstract Background and study aims. MRI-guided procedures combine high-quality imaging with lack of radiation. Percutaneous transhepatic cholangiodrainage under real-time MRI guidance (MRI-PTCD) seems promising, allowing targeted puncture and avoiding multiple blind passes and use of contrast, which are associated with standard PTCD's heaviest complications. Patients and methods. Aim of this study was to investigate the feasibility of MRI-PTCD in three outbred piglets. Obstructive cholestasis was induced by common bile duct ligation. Two days later, MRI-PTCD was performed (open MRI, 1.0 Tesla) with prototype MRI-compatible accessories. Visualization was achieved with a balanced steady-state free precession real-time sequence (bSSFP: 0.75 frames/s, TR/TE [ms]: 7.2/3.6; flip angle: 45°; 200 × 200 matrix size; resolution: 1.3 × 1.3 mm(2), slice thickness: 7 mm). Cannulation of the bile ducts was followed by placement of Yamakawa drainages. Results. Twelve punctures were performed (four per animal, 10/12 successful); in 2/10 the bile ducts could not be cannulated. Animal survival was 100% and no significant complications occurred. Conclusions. Initial data show that MRI-PTCD can be successfully performed. This may lead to establishment of a new optimized PTCD technique compared to the standard approach under fluoroscopy. PMID:24694300

Papanikolaou, Ioannis S; van der Voort, Ivo R; Chopra, Sascha S; Seebauer, Christian J; Rump, Jens; Papas, Maria G; Triantafyllou, Konstantinos; Baumgart, Daniel C; Teichgräber, Ulf K; Wiedenmann, Bertram; Rösch, Thomas

2014-06-01

402

B > 1 Tesla low mass magnetic field sweep assembly  

NASA Astrophysics Data System (ADS)

We have designed, modeled and tested a variable magnetic field sweep unit over a wide temperature range, from cryogenic to 100 C. The unit provides a sweepable uniform magnetic field, independent of temperature, over an air gap of 2 mm and spatial extent of 4 mm x 4 mm. It consists of a small magnet yoke structure and a spur gear driven rotatable magnet to vary the gap field in a nearly sinusoidal manner as a function of the magnet rotation angle. In the present design a 20 g SmCo magnet has been used, which allows for low temperature operation to 15 K when attached to a cryogenic refrigerator cold finger. The shape of the magnetic yoke structure has been modeled and optimized using 3-D magnetic field software. The gap field uniformity can thus be modeled and tested experimentally. In a present working model (2 mm gap) the field B(?) = 1.0 sin(?) (Tesla) where ? is the magnet rotation angle. With 0.25 mm thick permunder pole tips the field amplitude has been increased to 1.2 Tesla over a gap of 1.5 mm.

Cadieu, F. J.; Heremans, J. J.; Griffin, J.; Caldwell, C.; von Molnar, S.

1997-03-01

403

Extreme Material Physical Properties and Measurements above 100 tesla  

NASA Astrophysics Data System (ADS)

The National High Magnetic Field Laboratory (NHMFL) Pulsed Field Facility (PFF) at Los Alamos National Laboratory (LANL) offers extreme environments of ultra high magnetic fields above 100 tesla by use of the Single Turn method as well as fields approaching 100 tesla with more complex methods. The challenge of metrology in the extreme magnetic field generating devices is complicated by the millions of amperes of current and tens of thousands of volts that are required to deliver the pulsed power needed for field generation. Methods of detecting physical properties of materials are essential parts of the science that seeks to understand and eventually control the fundamental functionality of materials in extreme environments. De-coupling the signal of the sample from the electro-magnetic interference associated with the magnet system is required to make these state-of-the-art magnetic fields useful to scientists studying materials in high magnetic fields. The cutting edge methods that are being used as well as methods in development will be presented with recent results in Graphene and High-Tc superconductors along with the methods and challenges.

Mielke, Charles

2011-03-01

404

Evaluating joint-space narrowing and cartilage loss in rheumatoid arthritis by using MRI  

PubMed Central

Introduction Magnetic resonance imaging (MRI) has been shown to be superior to radiography (XR) for assessing synovitis, osteitis, and bone erosion in rheumatoid arthritis (RA), particularly in clinical trials. However, relatively little has been reported on the ability of MRI to evaluate articular cartilage loss, or joint-space narrowing (JSN), in the hands and wrists. In a previous study, we adapted the nine-point Genant-modified Sharp XR-JSN score for use with MRI (MRI-JSN). In this study, we compare MRI-JSN with XR-JSN by using images from two multicenter clinical trials. Methods Baseline XR and 1.5-Tesla MR images of one hand and wrist from each of 47 subjects with RA enrolled in one of two multicenter clinical trials were evaluated by using the XR-JSN and MRI-JSN methods by a single radiologist experienced in the two methods. Radiographs and MR images were read independently on different occasions. Results In total, 575 of 611 joints were compared (one metacarpophalangeal joint of the thumb and 35 proximal interphalangeal joints were outside the MRI field of view and could not be assessed). The 22 (47%) subjects showed JSN with both XR and MRI, and 25 (53%) subjects showed no JSN with either method. No subject showed JSN with only one or the other method. MRI showed high agreement with XR (intraclass correlation coefficient = 0.83). Sensitivity of MRI for JSN, by using XR as the gold standard, was 0.94; specificity was 0.91; accuracy was 0.91; positive predictive value was 0.64; and negative predictive value was 0.99. Conclusions This validation exercise suggests that MRI JSN scoring may offer a viable alternative to XR JSN scoring in multicenter clinical trials of RA. However, the relative longitudinal sensitivity of MRI to change and the ability to discriminate therapeutic effect on JSN were not evaluated in this study.

2012-01-01

405

Thermal ablation system using high intensity focused ultrasound (HIFU) and guided by MRI  

NASA Astrophysics Data System (ADS)

In this paper magnetic resonance imaging (MRI) is investigated for monitoring lesions created by high intensity focused ultrasound (HIFU) in kidney, liver and brain in vitro and in vivo. Spherically focused transducers of 4 cm diameter, focusing at 10 cm and operating at 1 and 4 MHz were used. An MRI compatible positioning device was developed in order to scan the HIFU transducer. The MRI compatibility of the system was successfully demonstrated in a clinical high-field MRI scanner. The ability of the positioning device to accurately move the transducer thus creating discrete and overlapping lesions in biological tissue was tested successfully. A simple, cost effective, portable positioning device has been developed which can be used in virtually any clinical MRI scanner since it can be sited on the scanner's table. The propagation of HIFU can use either a lateral or superior-inferior approach. Both T1-w FSE and T2-w FSE imaged successfully lesions in kidney and liver. T1-w FSE and T2-w FSE and FLAIR shows better anatomical details in brain than T1-w FSE, but with T1-w FSE the contrast between lesion and brain is higher for both thermal and bubbly lesion. With this system we were able to create large lesions (by producing overlapping lesions). The length of the lesions in vivo brain was much higher than the length in vitro, proving that the penetration in the in vitro brain is limited by reflection due to trapped bubbles in the blood vessels.

Damianou, C.; Ioannides, K.; Hadjisavas, V.; Milonas, N.; Couppis, A.; Iosif, D.; Komodromos, M.; Vrionides, F.

2009-04-01

406

Optimization of Brain T2 Mapping Using Standard CPMG Sequence In A Clinical Scanner  

NASA Astrophysics Data System (ADS)

In magnetic resonance imaging, transverse relaxation time (T2) mapping is a useful quantitative tool enabling enhanced diagnostics of many brain pathologies. The aim of our study was to test the influence of different sequence parameters on calculated T2 values, including multi-slice measurements, slice position, interslice gap, echo spacing, and pulse duration. Measurements were performed using standard multi-slice multi-echo CPMG imaging sequence on a 1.5 Tesla routine whole body MR scanner. We used multiple phantoms with different agarose concentrations (0 % to 4 %) and verified the results on a healthy volunteer. It appeared that neither the pulse duration, the size of interslice gap nor the slice shift had any impact on the T2. The measurement accuracy was increased with shorter echo spacing. Standard multi-slice multi-echo CPMG protocol with the shortest echo spacing, also the smallest available interslice gap (100 % of slice thickness) and shorter pulse duration was found to be optimal and reliable for calculating T2 maps in the human brain.

Hnilicová, P.; Bittšanský, M.; Dobrota, D.

2014-04-01

407

Enhanced cortical reperfusion protects coagulation factor XII-deficient mice from ischemic stroke as revealed by high-field MRI  

Microsoft Academic Search

Intrinsic coagulation factor XII deficient (FXII?\\/?) mice are protected from ischemic stroke. To elucidate underlying mechanisms we investigated the early ischemic period in vivo by multimodal magnetic resonance imaging (MRI) at 17.6 Tesla.Cerebral ischemia was induced by either transient (60 min) or permanent occlusion of the middle cerebral artery (t\\/pMCAO). 10 FXII?\\/? mice underwent t- , 10 FXII?\\/? mice p- and 10

M. Pham; C. Kleinschnitz; X. Helluy; A. J. Bartsch; M. Austinat; V. C. Behr; T. Renné; B. Nieswandt; G. Stoll; M. Bendszus

2010-01-01

408

Arm MRI scan  

MedlinePLUS

... arm MRI (magnetic resonance imaging) scan uses strong magnets to create pictures of the the upper and ... in your eyes) Because the MRI contains strong magnets, metal objects are not allowed into the room ...

409

Sinus MRI scan  

MedlinePLUS

... are turned into images. Different types of tissues send back different signals. Single MRI images are called ... Different types of tissues send back different MRI signals. For ... different signal than cancerous tissue. Abnormal results may ...

410

Recent advances in segmented gamma scanner analysis  

SciTech Connect

The segmented gamma scanner (SGS) is used in many facilities to assay low-density scrap and waste generated in the facilities. The procedures for using the SGS can cause a negative bias if the sample does not satisfy the assumptions made in the method. Some process samples do not comply with the assumptions. This paper discusses the effect of the presence of lumps on the SGS assay results, describes a method to detect the presence of lumps, and describes an approach to correct for the lumps. Other recent advances in SGS analysis are also discussed.

Sprinkle, J.K. Jr.; Hsue, S.T.

1987-01-01

411

Fast wire scanner for intense electron beams  

NASA Astrophysics Data System (ADS)

We have developed a cost-effective, fast rotating wire scanner for use in accelerators where high beam currents would otherwise melt even carbon wires. This new design uses a simple planetary gear setup to rotate a carbon wire, fixed at one end, through the beam at speeds in excess of 20 m/s. We present results from bench tests, as well as transverse beam profile measurements taken at Cornell's high-brightness energy recovery linac photoinjector, for beam currents up to 35 mA.

Moore, T.; Agladze, N. I.; Bazarov, I. V.; Bartnik, A.; Dobbins, J.; Dunham, B.; Full, S.; Li, Y.; Liu, X.; Savino, J.; Smolenski, K.

2014-02-01

412

Principali componenti di uno scanner TC  

Microsoft Academic Search

\\u000a I requisiti strutturali di una sala in cui si svolge attività diagnostica mediante tomografia computerizzata variano in funzione\\u000a del tipo di apparecchiatura prevista e della tipologia di esami che saranno effettuati. In linea generale, una diagnostica\\u000a TC prevede tre aree distinte.\\u000a \\u000a \\u000a \\u000a 1. \\u000a \\u000a Sala diagnostica: è il locale nel quale sono posizionati lo scanner TC (gantry e lettino porta-paziente), il generatore,

Simona Corona; Silvia Cavaliere; Cristiana Baggiani

413

A laser scanner for 35mm film  

NASA Technical Reports Server (NTRS)

The design, construction, and testing of a laser scanning system is described. The scanner was designed to deliver a scanned beam over a 2.54 cm by 2.54 cm or a 5.08 cm by 5.08 cm format. In order to achieve a scan resolution and rate comparable to that of standard television, an acousto-optic deflector was used for one axis of the scan, and a light deflecting galvanometer for deflection along the other axis. The acoustic optic deflector has the capability of random access scan controlled by a digital computer.

Callen, W. R.; Weaver, J. E.

1977-01-01

414

LAPR: An experimental aircraft pushbroom scanner  

NASA Technical Reports Server (NTRS)

A three band Linear Array Pushbroom Radiometer (LAPR) was built and flown on an experimental basis by NASA at the Goddard Space Flight Center. The functional characteristics of the instrument and the methods used to preprocess the data, including radiometric correction, are described. The radiometric sensitivity of the instrument was tested and compared to that of the Thematic Mapper and the Multispectral Scanner. The radiometric correction procedure was evaluated quantitatively, using laboratory testing, and qualitatively, via visual examination of the LAPR test flight imagery. Although effective radiometric correction could not yet be demonstrated via laboratory testing, radiometric distortion did not preclude the visual interpretation or parallel piped classification of the test imagery.

Wharton, S. W.; Irons, J. I.; Heugel, F.

1980-01-01

415

Integrated Electro-optical Laser-Beam Scanners  

NASA Technical Reports Server (NTRS)

Scanners using solid-state devices compact, consume little power, and have no moving parts. Integrated electro-optical laser scanner, in conjunction with external lens, points outgoing beam of light in any number of different directions, depending on number of upper electrodes. Offers beam-deflection angles larger than those of acousto-optic scanners. Proposed for such diverse applications as nonimpact laser printing, color imaging, ranging, barcode reading, and robotic vision.

Boord, Warren T.

1990-01-01

416

Scanners for visualizing activity of analog VLSI circuitry  

Microsoft Academic Search

This paper tutorially describes mixed digital-analog serial multiplexers (scanners) that we use to visualize the activity of one- and two-dimensional arrays of analog VLSI elements. These scanners range from simple one-dimensional devices designed to scan a one-dimensional array onto an oscilloscope, to complete video scanners with integrated sync and blank computation and on-chip video amplifiers. We discuss practical details of

Carver A. Mead; Tobias Delbrück

1991-01-01

417

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

Microsoft Academic Search

In this article, we study in vitro evaluation of needle artefacts and image quality for musculoskeletal laser-interventions\\u000a in an open high-field magnetic resonance imaging (MRI) scanner at 1.0T with vertical field orientation. Five commercially\\u000a available MRI-compatible puncture needles were assessed based on artefact characteristics in a CuSO4 phantom (0.1%) and in\\u000a human cadaveric lumbar spines. First, six different interventional sequences

Uta Wonneberger; Bernhard Schnackenburg; Florian Streitparth; Thula Walter; Jens Rump; Ulf K. M. Teichgräber

2010-01-01

418

Right Coronary Artery Flow Velocity and Volume Assessment with Spiral K-Space Sampled Breath-Hold Velocity-Encoded Magnetic Resonance Imaging at 3Tesla: Accuracy and Reproducibility  

PubMed Central

Purpose To evaluate accuracy and reproducibility of flow velocity and volume measurements in a phantom and in human coronary arteries using breath-hold velocity-encoded (VE) MRI with spiral k-space sampling at 3Tesla. Materials and Methods Flow velocity assessment was performed using VE MRI with spiral k-space sampling. Accuracy of VE MRI was tested in vitro at five constant flow rates. Reproducibility was investigated in 19 healthy subjects (mean age 25.4± 1.2 years, 11 men,) by repeated acquisition in the right coronary artery (RCA). Results MRI-measured flow rates correlated strongly with volumetric collection (Pearson correlation r=0.99; p<0.01). Due to limited sample resolution, VE MRI overestimated the flow rate by 47% on average when non-constricted region-of-interest segmentation was used. Using constricted region-of-interest segmentation with lumen size equal to ground-truth luminal size, less than 13% error in flow rate was found. In vivo RCA flow velocity assessment was successful in 82% of the applied studies. High interscan, intra- and inter-observer agreement was found for almost all indices describing coronary flow velocity. Reproducibility for repeated acquisitions varied by less than 16% for peak velocity values and by less than 24% for flow volumes. Conclusion 3T breath-hold VE MRI with spiral k-space sampling enables accurate and reproducible assessment of RCA flow velocity.

Brandts, Anne; Roes, Stijntje D.; Doornbos, Joost; Weiss, Robert G.; de Roos, Albert; Stuber, Matthias; Westenberg, Jos J.M.

2010-01-01

419

Scanner effects on directed self-assembly patterning  

NASA Astrophysics Data System (ADS)

Directed self-assembly (DSA) of various polymers is a potential next-generation lithography component. Lithographers can use an ArF scanner to print guide structures with pitches accessible with current technology. The DSA materials, in a non-exposure step, perform pitch multiplication of 1-D and 2-D guide structures. While research has investigated defects inherent to the DSA material, ArF scanner effects have received little attention. This work uses DSA models and scanner models to assess requirements for ArF immersion scanners for DSA complimentary lithography.

Renwick, Stephen P.

2014-03-01

420

MRI of the shoulder  

Microsoft Academic Search

This book reports on the use of magnetic resonance imaging (MRI) in evaluating shoulder disorders. The book gives detailed information on MRI techniques and shoulder anatomy, describes and illustrates MRI findings for a wide range of shoulder disorders, and explains how abnormalities seen on MIR images relate to pathophysiology and clinical signs. Special attention is given to imaging of rotator

M. B. Zlatkin; J. P. Iannotti; M. D. Schnall

1991-01-01