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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

In Situ Active Control of Noise in a 4-Tesla MRI Scanner  

PubMed Central

Purpose To evaluate the effectiveness of the proposed active noise control (ANC) system for the reduction of the acoustic noise emission generated by a 4 T MRI scanner during operation and to assess the feasibility of developing an ANC device that can be deployed in situ. Materials and Methods Three typical scanning sequences, namely EPI (echo planar imaging), GEMS (gradient echo multi-slice) and MDEFT (Modified Driven Equilibrium Fourier Transform), were used for evaluating the performance of the ANC system, which was composed of a magnetic compatible headset and a multiple reference feedforward filtered-x least mean square controller. Results The greatest reduction, about 55 dB, was achieved at the harmonic at a frequency of 1.3 kHz in the GEMS case. Approximately 21 dB and 30 dBA overall reduction was achieved for GEMS noise across the entire audible frequency range. For the MDEFT sequence, the control system achieved 14 dB and 14 dBA overall reduction in the audible frequency range, while 13 dB and 14 dBA reduction was obtained for the EPI case. Conclusion The result is highly encouraging because it shows great potential for treating MRI noise with an ANC application during real time scanning.

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

2011-01-01

3

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

4

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

5

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

6

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

7

Magnetic Field Interactions of Orthodontic Wires during Magnetic Resonance Imaging (MRI) at 1.5 Tesla  

Microsoft Academic Search

Background: Orthodontic appliances pose a potential risk during magnetic resonance imaging (MRI) due to forces on metallic objects within the static magnetic field of MRI systems. The aim of the present investigation was to measure forces on orthodontic wires caused by the static magnetic field of a 1.5-Tesla MRI system, and to assess the safety hazards associated with these forces.

Dirk Schulze; Gerhard Adam; Bärbel Kahl-Nieke

2005-01-01

8

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

9

Absolute Temperature Monitoring Using RF Radiometry in the MRI Scanner.  

PubMed

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. PMID:18026562

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

2006-11-01

10

Magnetic Forces on Orthodontic Wires in High Field Magnetic Resonance Imaging (MRI) at 3 Tesla  

Microsoft Academic Search

\\u000a Abstract\\u000a \\u000a \\u000a Background:\\u000a   In a previous investigation we reported on magnetic forces in the static magnetic field of a 1.5 Tesla MRI system. The aim\\u000a of the present investigation was to assess forces on orthodontic wires in a high field strength MRI system at 3 Tesla.\\u000a \\u000a \\u000a \\u000a \\u000a Materials and Methods:\\u000a   Thirty-two different orthodontic wires (21 archwires, eight ligature wires and three retainer

Arndt Klocke; Bärbel Kahl-Nieke; Gerhard Adam; Jörn Kemper

2006-01-01

11

MRI of the Wrist at 7 Tesla using an 8 Channel Array Coil Combined with Parallel Imaging: Preliminary Results  

PubMed Central

PURPOSE To determine the feasibility of performing MRI of the wrist at 7 Tesla with parallel imaging and to evaluate how acceleration factors(AF) affect signal-to-noise ratio(SNR), contrast-to-noise ratio(CNR), and image quality. MATERIALS AND METHODS This study had institutional review board approval. A 4-transmit 8-receive channel array coil was constructed in–house. Nine healthy subjects were scanned on a 7T whole-body MR scanner. Coronal and axial images of cartilage and trabecular bone micro-architecture(3D-Fast Low Angle Shot(FLASH) with and without fat suppression, TR/TE=20ms/4.5ms, flip angle=10°, 0.169–0.195×0.169–0.195 mm, 0.5–1 mm slice thickness) were obtained with AF 1, 2, 3, 4. T1-weighted fast spin-echo(FSE), proton density-weighted FSE, and multiple-echo data image combination(MEDIC) sequences were also performed. SNR and CNR were measured. Three musculoskeletal radiologists rated image quality. Linear correlation analysis and paired t-tests were performed. RESULTS At higher AF, SNR and CNR decreased linearly for cartilage, muscle, and trabecular bone(rTesla MRI of the wrist with parallel imaging. SNR and CNR decrease with higher AF, but image quality remains above-average.

Chang, Gregory; Friedrich, Klaus M.; Wang, Ligong; Vieira, Renata L.R.; Schweitzer, Mark E.; Recht, Michael P.; Wiggins, Graham C.; Regatte, Ravinder R.

2010-01-01

12

Clinical and technical considerations for high quality breast MRI at 3 Tesla.  

PubMed

The use of breast MRI at 3 tesla (T) has increased in use substantially in recent years. Potential benefits of moving to higher field strength MRI include improved morphologic and kinetic assessment of breast lesions through higher spatial and temporal resolution dynamic contrast-enhanced MR examinations. Furthermore, higher field strength holds promise for the development of superior advanced breast MRI techniques, such as diffusion weighted imaging and MR spectroscopy. To fully realize the benefits of moving to 3T, a thorough understanding of the technical and safety challenges of higher field strength imaging specific to breast MRI is paramount. Through the use of advanced coil technology, parallel imaging, dual-source parallel radiofrequency excitation, and image-based shimming techniques, many of these limiting technical factors can be overcome to achieve high quality breast MRI at 3T. PMID:23526757

Rahbar, Habib; Partridge, Savannah C; DeMartini, Wendy B; Thursten, Bonnie; Lehman, Constance D

2013-04-01

13

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

14

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

Microsoft Academic Search

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

Sami Kännälä; Tim Toivo; Tommi Alanko; Kari Jokela

2009-01-01

15

Design and development of a respiratory monitoring device to be used in conjuction with MRI scanners  

Microsoft Academic Search

The aim of this project was to design and manufacture a respiratory monitoring device that operates in conjunction with MRI scanners to produce higher quality images. The resultant quality of many MRI images depends on how well the patient can control their breathing activity. This research has been successful in designing and manufacturing a device that can be used to

Aidan McNally

2004-01-01

16

Effect of 1. 5 tesla nuclear magnetic resonance imaging scanner on implanted permanent pacemakers  

SciTech Connect

Patients with a permanent pacemaker are currently restricted from diagnostic nuclear magnetic resonance (NMR) imaging because of potential adverse effects on the pacemaker by the magnet. Previous work has shown that NMR imaging will result in asynchronous pacing of the pulse generator within a given distance of the magnet. The radiofrequency signal generated by the system may also result in rapid cardiac pacing, which may have deleterious effects. This study utilized a 1.5 tesla unit in an in vivo laboratory animal to evaluate the unit's effects on eight different pulse generators from two manufacturers. All pacemakers functioned in an asynchronous mode when placed within a certain distance of the magnet. In addition, transient reed switch inhibition was observed. Seven of the eight pulse generators paced rapidly when exposed to the radiofrequency signal and there was a dramatic decrease in arterial blood pressure. Whether effective rapid cardiac pacing would occur could not be predicted before exposure to the magnetic resonance unit. Nuclear magnetic resonance imaging with high magnetic fields in patients with a pacemaker should continue to be avoided until the mechanism of the rapid cardiac pacing can be further delineated and either predicted or prevented.

Hayes, D.L.; Holmes, D.R. Jr.; Gray, J.E.

1987-10-01

17

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

2013-02-12

18

Low-Cost, High Quality MRI Breast Scanner Using Prepolarization.  

National Technical Information Service (NTIS)

Magnetic Resonance Imaging (MRI) has been shown to be more sensitive and equally specific when compared to x-ray mammography for detecting breast cancer. MRI is non-invasive, completely non-toxic, and requires no uncomfortable breast compression. But an x...

A. Macvoski

2001-01-01

19

Liver iron quantification by 3 tesla MRI: Calibration on a rabbit model.  

PubMed

PURPOSE: To determine the feasibility of liver iron quantification by 3 Tesla (T) MRI using a novel iron overload rabbit model. MATERIALS AND METHODS: Forty-two rabbits underwent iron dextran loading from 1 to 15 weeks. MRI signal intensity ratio (SIR) was measured using a gradient-echo sequence, and R2(1/T2) measured using an eight-echo spin-echo sequence at 3T. Ex vivo hepatic pathology was obtained for all rabbits studied. Postmortem assessments of liver iron concentration (LIC) were conducted in an atomic absorption spectrophotometer. MRI measures were fitted against LIC using linear regression for 30 of the iron-loaded rabbits. The remaining 12 iron-loaded rabbits were used to test the prediction accuracy of the derived models. RESULTS: LIC was linearly correlated to both liver-to-muscle SIR (r = -0.845) and R2 (r = 0.965) in a range achieved in this study (LIC < 10 mg/g dry tissue) at 3T. By regression, the linear equations were determined as: () Y1 = 10.581-5.924X1 (Y1 : LIC, X1 :SIR); () Y2 = -1.273+0.103X2 (Y2 :LIC, X2 :R2). In the 12 test rabbits, the predicted LICs using the derived equations agreed well with the results obtained using the spectrophotometer. CONCLUSION: Both SIR and R2 are highly correlated with LIC in a novel rabbit model. MRI quantification of liver iron overload is feasible at 3T. J. Magn. Reson. Imaging 2013. © 2013 Wiley Periodicals, Inc. PMID:23704041

Peng, Peng; Huang, Zhongkui; Long, Liling; Zhao, Fanyu; Li, Chunyan; Li, Wenmei; He, Taigang

2013-05-23

20

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

21

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

2009-03-17

22

Transrectal Prostate Biopsy Inside Closed MRI Scanner with Remote Actuation, under Real-Time Image Guidance  

Microsoft Academic Search

We present the proof-of-concept prototype of a prostate biopsy robot to be used inside a conventional high -field MRI scanner. A three degree-of- freedom (DOF) mechanical device translates and rotates inside the rectum and enters a needle into the body, and steers th e needle to a target point pre-selected by the user. The device is guided by real -time

Gabor Fichtinger; Axel Krieger; Robert C. Susil; Attila Tanács; Louis L. Whitcomb; Ergin Atalar

2002-01-01

23

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

2010-12-08

24

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

25

Radiofrequency-induced Heating near Fixed Orthodontic Appliances in High Field MRI Systems at 3.0 Tesla  

Microsoft Academic Search

\\u000a Abstract\\u000a \\u000a \\u000a Objective:\\u000a   To assess radiofrequency (RF)-induced heating of\\u000a fixed orthodontic appliances during acquisition of three different\\u000a sequences in magnetic resonance imaging (MRI) at 3 Tesla.\\u000a \\u000a \\u000a \\u000a \\u000a Materials and Methods:\\u000a   Ten commonly used fixed orthodontic\\u000a appliances were investigated utilizing a phantom head and simulating\\u000a the in vivo intraoral situation. A 3 Tesla MRI system (Intera,\\u000a Philips Medical Systems, Best, The Netherlands) was

Marc Regier; Jörn Kemper; Michael G. Kaul; Markus Feddersen; Gerhard Adam; Bärbel Kahl-Nieke; Arndt Klocke

2009-01-01

26

Obese patients in an open MRI at 1.0 Tesla: image quality, diagnostic impact and feasibility  

Microsoft Academic Search

Objective  To investigate the performance of an open MRI system at its conceptual limits by examining excessively obese patients who\\u000a otherwise could not receive adequate imaging examinations.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Twenty-six excessively obese patients (BMI???35, average age 46) where CT, standard MR or ultrasound examinations were not\\u000a possible or not conclusive were referred to an open MRI system at 1.0 Tesla. Image quality was

Maximilian de Bucourt; Florian Streitparth; Uta Wonneberger; Jens Rump; Ulf Teichgräber

2011-01-01

27

The Interconnection of MRI Scanner and MR-Compatible Robotic Device: Synergistic Graphical User Interface to Form a Mechatronic System  

PubMed Central

MRI scanner and magnetic resonance (MR)-compatible robotic devices are mechatronic systems. Without an interconnecting component, these two devices cannot be operated synergetically for medical interventions. In this paper, the design and properties of a graphical user interface (GUI) that accomplishes the task is presented. The GUI interconnects the two devices to obtain a larger mechatronic system by providing command and control of the robotic device based on the visual information obtained from the MRI scanner. Ideally, the GUI should also control imaging parameters of the MRI scanner. Its main goal is to facilitate image-guided interventions by acting as the synergistic component between the physician, the robotic device, the scanner, and the patient.

Ozcan, Alpay; Tsekos, Nikolaos

2011-01-01

28

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

2013-06-13

29

Examining the McGurk illusion using high-field 7 Tesla functional MRI.  

PubMed

In natural communication speech perception is profoundly influenced by observable mouth movements. The additional visual information can greatly facilitate intelligibility but incongruent visual information may also lead to novel percepts that neither match the auditory nor the visual information as evidenced by the McGurk effect. Recent models of audiovisual (AV) speech perception accentuate the role of speech motor areas and the integrative brain sites in the vicinity of the superior temporal sulcus (STS) for speech perception. In this event-related 7 Tesla fMRI study we used three naturally spoken syllable pairs with matching AV information and one syllable pair designed to elicit the McGurk illusion. The data analysis focused on brain sites involved in processing and fusing of AV speech and engaged in the analysis of auditory and visual differences within AV presented speech. Successful fusion of AV speech is related to activity within the STS of both hemispheres. Our data supports and extends the audio-visual-motor model of speech perception by dissociating areas involved in perceptual fusion from areas more generally related to the processing of AV incongruence. PMID:22529797

Szycik, Gregor R; Stadler, Jörg; Tempelmann, Claus; Münte, Thomas F

2012-04-19

30

Evaluation of Artifacts and Distortions of Titanium Applicators on 3.0Tesla MRI: Feasibility of Titanium Applicators in MRI-Guided Brachytherapy for Gynecological Cancer  

Microsoft Academic Search

Purpose: The aim of this study was to characterize the levels of artifacts and distortions of titanium applicators on 3.0-Tesla magnetic resonance imaging (MRI). Methods and Materials: Fletcher-Suit-Delclos-style tandem and ovoids (T and O) and tandem and ring applicator (T and R) were examined. The quality assurance (QA) phantoms for each applicator were designed and filled with copper sulphate solution

Yusung Kim; Manickam Muruganandham; Joseph M. Modrick; John E. Bayouth

2011-01-01

31

Implementation of wavelet encoding spectroscopic imaging technique on a 3 Tesla whole body mr scanner: In vitro results  

Microsoft Academic Search

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

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

2009-01-01

32

The Spinal Curvature of Three Different Sitting Positions Analysed in an Open MRI Scanner  

PubMed Central

Sitting is the most frequently performed posture of everyday life. Biomechanical interactions with office chairs have therefore a long-term effect on our musculoskeletal system and ultimately on our health and wellbeing. This paper highlights the kinematic effect of office chairs on the spinal column and its single segments. Novel chair concepts with multiple degrees of freedom provide enhanced spinal mobility. The angular changes of the spinal column in the sagittal plane in three different sitting positions (forward inclined, reclined, and upright) for six healthy subjects (aged 23 to 45 years) were determined using an open magnetic resonance imaging (MRI) scanner. An MRI-compatible and commercially available office chair was adapted for use in the scanner. The midpoint coordinates of the vertebral bodies, the wedge angles of the intervertebral discs, and the lumbar lordotic angle were analysed. The mean lordotic angles were 16.0 ± 8.5° (mean ± standard deviation) in a forward inclined position, 24.7 ± 8.3° in an upright position, and 28.7 ± 8.1° in a reclined position. All segments from T10-T11 to L5-S1 were involved in movement during positional changes, whereas the range of motion in the lower lumbar segments was increased in comparison to the upper segments.

Baumgartner, Daniel; Zemp, Roland; List, Renate; Stoop, Mirjam; Naxera, Jaroslav; Elsig, Jean Pierre; Lorenzetti, Silvio

2012-01-01

33

Coupling scintillation light into optical fibre for use in a combined PET-MRI scanner  

NASA Astrophysics Data System (ADS)

We investigate the specific problem of efficient coupling and transmission of light from a small inorganic crystal into optical fibre. The long-term goal of our project is the construction of a dual Positron Emission Tomography (PET)-Magnetic Resonance Imaging (MRI) scanner. The technique discussed in this paper can efficiently transport the scintillator light out of the high magnetic field and constrained spatial volume of the MRI magnet bore to a convenient and low-field region meters away without affecting the homogeneity of the MRI field. Presented are measurements and calculations on the coupling and transmission of light created in a 2.45 × 2.45 × 10 mm crystal of LSO suitable for high-resolution PET. We find that a solution for transport of the light particular to our PET-MRI interests is via optical fibre bundles of 200 ?m core fibres butted against the end of the crystal. These small core fibres are better suited than their larger diameter counterparts as they permit a smaller bending radius and have a similar packing fraction. Our results indicate that the small LSO crystal butted to a hexagonally packed bundle of 176 fibres of 3 m length produces adequate scintillation light for PET applications.

Haak, Gerhard M.; Christensen, Nelson L.; Hammer, Bruce E.

1997-02-01

34

Ag/AgCl electrodes in the EEG/fMRI method in 3T MRI scanner  

NASA Astrophysics Data System (ADS)

This study focuses on the comparison of two different types of EEG electrodes (the first B10-S-150 Ag/AgCl sintered ring electrode with 1, 5 mm touch proof safety socket and 150 cm heavy-duty lead wire and the second, B12-LS-100 Ag/AgCl sintered FE-electrode with 100 cm light-duty lead wire and 1, 5 mm touch proof safety socket with 5 k? resistor near sensor) used in the EEG/fMRI method in 3T MRI scanner. We compared these electrodes by their specific absorption rate (SAR) simulation values and the temperature change calculated by PRF method. The experimental setup of the study is described as follows: a phantom is prepared and the electrodes are placed on it. Then, a simulation for SAR values is realized. The temperature change is calculated by MR thermometer. As a result of this study, Ag/AgCl pin electrode is better to be use in EEG/fMRI; because the measured temperature change is expected to be low.

Akay, Cengiz; Kepceo?lu, Abdullah

2013-10-01

35

High-resolution MRI of the wrist and finger joints in patients with rheumatoid arthritis: comparison of 1.5 Tesla and 3.0 Tesla.  

PubMed

The goal of this study was to compare magnetic resonance (MR) image quality at different field strengths for evaluating lesions in wrist and finger joints of patients with rheumatoid arthritis (RA) in order to determine whether the higher field strength provides diagnostic gain. The hand mainly affected in 17 RA patients was examined at 1.5 Tesla (T) and 3.0 T with comparable MR imaging (MRI) protocols. MR images were reviewed twice by two experienced radiologists using the Rheumatoid Arthritis MRI Scoring System (RAMRIS) of the OMERACT (Outcome Measures in Rheumatoid Arthritis Clinical Trials) group. Image quality was rated on a five-point scale using Friedmann's test and Kendall's W-test for statistical analysis. Image comparison revealed better image quality at higher field strength. Image quality of T1-weighted images was rated 14-22% better at 3.0 T compared with 1.5 T by both readers. Moreover, the rating for the T2-weighted-images acquired at 3.0 T was one point better in the five-point scale used. Inter-reader correlation for image quality, bone erosions/defects, edema and synovitis ranged between 0.6 and 0.9 at 3.0 T and between 0.6 and 0.8 at 1.5 T. Intra-reader correlation for these parameters was high at 0.8-1.0. MRI image quality of RA hands is superior at 3.0 T, while an acceptable image quality is achieved at 1.5 T, which improves the evaluation of extent of bone edema, synovitis and identification of small bone erosions. PMID:17219147

Wieners, Gero; Detert, Jacqueline; Streitparth, Florian; Pech, Maciej; Fischbach, Frank; Burmester, Gerd; Ricke, Jens; Backhaus, Marina; Bruhn, Harald

2007-01-12

36

Feasibility study using MRI and two optical CT scanners for readout of polymer gel and PresageTM  

NASA Astrophysics Data System (ADS)

The aim of this study was to compare the conventional combination of three-dimensional dosimeter (nPAG gel) and readout method (MRI) with other combinations of three-dimensional dosimeters (nPAG gel/PresageTM) and readout methods (optical CT scanners). In the first experiment, the dose readout of a gel irradiated with a four field-box technique was performed with both an Octopus IQ scanner and MRI. It was seen that the MRI readout agreed slightly better to the TPS. In another experiment, a gel and a PresageTM sample were irradiated with a VMAT field and read out using MRI and a fast laser scanner, respectively. A comparison between the TPS and the volumes revealed that the MRI/gel readout had closer resemblance to the TPS than the optical CT/PresageTM readout. There are clearly potential in the evaluated optical CT scanners, but more time has to be invested in the particular scanning scenario than was possible in this study.

Svensson, H.; Skyt, P. S.; Ceberg, S.; Doran, S.; Muren, L. P.; Balling, P.; Petersen, J. B. B.; Bäck, S. Å. J.

2013-06-01

37

Relationship of Clinical and Cognitive Variables with Brain Morphometric Abnormalities in Alzheimer's Disease: a Voxel Based Morphometric Study Using 3-Tesla MRI  

PubMed Central

Alzheimer’s disease (AD) is associated with widespread structural and functional brain alterations. The current study examined the gray matter (GM) voxel based morphometric (VBM) correlates of cognitive and clinical severity scores in patients with AD. The study included 34 patients with AD according to NINCDS/ADRDA AD criteria and 28 matched elderly controls. All subjects were clinically evaluated using Hindi Mental Status Examination (HMSE), Everyday Abilities Scale for India (EASI) and the Clinical Dementia Rating (CDR) scale. The structural Magnetic Resonance Imaging (MRI) data were acquired using a 3 Tesla MRI scanner and VBM analysis was performed using VBM5.1 toolbox. The patients with AD had significantly lower GM volume, white matter volume and total brain volume as compared to controls. The HMSE scores were positively correlated (p=0.009) and EASI (p=0.04) & CDR (p=0.0004) were negatively correlated with the total GM volumes in patients with AD. The VBM analysis revealed diffuse GM atrophy in patients with AD. Frontal& temporal GM volumes were positively correlated with the HMSE scores. Thus the results of the study replicate the previous observations of generalized GM atrophy, in an Indian sample with AD. The cognitive decline, clinical dementia severity and impairment in activities of daily living were correlated whole brain GM and WM volumes as well as with specific brain regional atrophy in AD. However further studies with larger samples & with more detailed cognitive evaluation are required for confirmation & validation of the relationship between regional morphometric abnormalities and cognitive deficits in AD.

Bagepally, Bhavani S.; John, John P.; Varghese, Mathew; Halahalli, Harsha N.; Kota, Lakshminarayanan; Sivakumar, Palanimuthu T.; Bharath, Srikala; Jain, Sanjeev

2013-01-01

38

Removal of ballistocardiogram artifact from EEG data acquired in the MRI scanner: selection of ICA components.  

PubMed

The removal of ballistocardiogram (BCG) artifact from the EEG recorded in the MRI scanner is challenging. Few studies have utilized independent component analysis (ICA) in this task. A drawback of ICA has been the proper selection of the BCG related components. The key idea in this work is to use the difference between the power spectrum of the artifact-processed data and the spectrum of data recorded outside the scanner as a cost function in the selection of the BCG related independent components. Forward floating selection algorithm was implemented to find the components to minimize this criterion. Also, the typical component selection criteria based on the correlation with electrocardiogram (ECG) signal and on explained variance were compared in this respect. The correlation criterion was least successful leaving considerable residual artifact in the signal. With the first few removed components the variance criterion performed as well as the minimum spectral difference criterion. With the variance criterion alone, however, the number of the components to be removed cannot be determined. The suggested methods may provide objective means to validate residual artifact or the possible loss of physiological signal due to artifact removal and to help selecting the proper artifact-related components. PMID:19163894

Koskinen, Miika; Vartiainen, Nuutti

2008-01-01

39

Functional MR imaging of visual and motor cortex stimulation at high temporal resolution using a FLASH technique on a standard 1.5 Tesla scanner.  

PubMed

Functional magnetic resonance imaging (fMRI) was performed on a conventional 1.5 T scanner by means of a modified FLASH-technique at temporal resolutions of 80 and 320 ms. The method's stability was assessed by phantom measurements and by investigation of three volunteers resulting in a low amplitude (3%) periodic (4 s) signal modulation for the in vivo measurements, which was not observable in the phantom experiments. fMRI activation studies of motor and visual cortices of four adjacent slices were carried out on 12 healthy right-handed volunteers. Stimulation was performed by a triggered single white light flash or single finger-to-thumb opposition movement, respectively. Event-related response of visual and motor activation was traced over 10.24 s with a temporal resolution of 320 ms for the four slice measurements. Brain activation maps were calculated by correlation of measured signal time course with a time-shifted boxcar function. Activation was quantified by calculation of percentual signal change in relation to the baseline. Observed signal magnitudes were about 5-7% in visual and about 8-12% in primary motor cortex. While photic response was delayed by about 2 s, motor stimulation showed an instantaneous increase of the MR signal. MR signal responses for both stimuli had decayed completely after about 5 s. Our results show that event-related fMRI enables mapping of brain function at sufficient spatial resolution with a temporal resolution of up to 80 ms on a conventional scanner. PMID:8843360

Wiener, E; Schad, L R; Baudendistel, K T; Essig, M; Müller, E; Lorenz, W J

1996-01-01

40

MRI-Guided Intervention for Breast Lesions Using the Freehand Technique in a 3.0-T Closed-Bore MRI Scanner: Feasibility and Initial Results  

PubMed Central

Objective To report the feasibility of magnetic resonance imaging (MRI)-guided intervention for diagnosing suspicious breast lesions detectable by MRI only, using the freehand technique with a 3.0-T closed-bore MRI scanner. Materials and Methods Five women with 5 consecutive MRI-only breast lesions underwent MRI-guided intervention: 3 underwent MRI-guided needle localization and 2, MRI-guided vacuum-assisted biopsy. The interventions were performed in a 3.0-T closed-bore MRI system using a dedicated phased-array breast coil with the patients in the prone position; the freehand technique was used. Technical success and histopathologic outcome were analyzed. Results MRI showed that four lesions were masses (mean size, 11.5 mm; range, 7-18 mm); and 1, a nonmass-like enhancement (maximum diameter, 21 mm). The locations of the lesions with respect to the breast with index cancer were as follows: different quadrant, same breast - 3 cases; same quadrant, same breast - 1 case; and contralateral breast - 1 case. Histopathologic evaluation of the lesions treated with needle localization disclosed perilobular hemangioma, fibrocystic change, and fibroadenomatous change. The lesions treated with vacuum-assisted biopsy demonstrated a radial scar and atypical apocrine hyperplasia. Follow-up MRI after 2-7 months (mean, 4.6 months) confirmed complete lesion removal in all cases. Conclusion MRI-guided intervention for breast lesions using the freehand technique with a 3.0-T closed-bore MRI scanner is feasible and accurate for diagnosing MRI-only lesions.

Choi, Hye Young; Jang, Mijung; Yun, Bo La; Kim, Sung-Won; Kang, Eunyoung; Park, So Yeon; Moon, Woo Kyung; Ko, Eun Sook

2013-01-01

41

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  

Microsoft Academic Search

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

Ivo L Partecke; André Kaeding; Matthias Sendler; Nele Albers; Jens-P Kühn; Sven Speerforck; Sebastian Roese; Florian Seubert; Stephan Diedrich; Sandra Kuehn; Ulrich F Weiss; Julia Mayerle; Markus M Lerch; Stefan Hadlich; Norbert Hosten; Claus-D Heidecke; Ralf Puls; Wolfram von Bernstorff

2011-01-01

42

Silicone made contractile dielectric elastomer actuators inside 3Tesla MRI environment  

Microsoft Academic Search

New actuators are greatly demanded today in order to develop magnetic resonance imaging (MRI)- compatible mechatronic systems capable of extended and improved capabilities. They are particularly needed for MRI- guided interventional or rehabilitation procedures. Actuators based on dielectric elastomers, a specific class of electroactive polymers, appear as suitable candidates for new MRI- compatible technologies, due to their intrinsic material properties

Federico Carpi; Azadeh Khanicheh; Constantinos Mavroidis; Danilo De Rossi

2008-01-01

43

Application of parallel imaging to fMRI at 7 Tesla utilizing a high 1D reduction factor.  

PubMed

Gradient-echo EPI, blood oxygenation level-dependent (BOLD) functional MRI (fMRI) using parallel imaging (PI) is demonstrated at 7 Tesla with 16 channels, a fourfold 1D reduction factor (R), and fourfold maximal aliasing. The resultant activation detection in finger-tapping fMRI studies was robust, in full agreement with expected activation patterns based on prior knowledge, and with functional maps generated from full field of view (FOV) coverage of k-space using segmented acquisition. In all aspects the functional maps acquired with PI outperformed segmented coverage of full k-space. With a 1D R of 4, fMRI activation based on PI had higher statistical significance, up to 1.6-fold in an individual case and 1.25+/-.25 (SD) fold when averaged over six studies, compared to four-segment/full-FOV data in which the square root R reduction in the image signal-to-noise ratio (SNR) due to k-space undersampling was compensated for by acquiring additional repetitions of the undersampled k-space. When this compensation for loss in SNR was not performed, the effect of PI was determined by the ratio of physiologically induced vs. intrinsic (thermal) noise in the fMRI time series and the extent to which physiological "noise" was amplified by the use of segmentation in the full-FOV data. The results demonstrate that PI is particularly beneficial at this ultrahigh field strength, where both the intrinsic image SNR and temporal signal fluctuations due to physiological processes are large. PMID:16767760

Moeller, Steen; Van de Moortele, Pierre-Francois; Goerke, Ute; Adriany, Gregor; Ugurbil, Kâmil

2006-07-01

44

A 4-channel 3 Tesla phased array receive coil for awake rhesus monkey fMRI and diffusion MRI experiments  

PubMed Central

Awake monkey fMRI and diffusion MRI combined with conventional neuroscience techniques has the potential to study the structural and functional neural network. The majority of monkey fMRI and diffusion MRI experiments are performed with single coils which suffer from severe EPI distortions which limit resolution. By constructing phased array coils for monkey MRI studies, gains in SNR and anatomical accuracy (i.e., reduction of EPI distortions) can be achieved using parallel imaging. The major challenges associated with constructing phased array coils for monkeys are the variation in head size and space constraints. Here, we apply phased array technology to a 4-channel phased array coil capable of improving the resolution and image quality of full brain awake monkey fMRI and diffusion MRI experiments. The phased array coil is that can adapt to different rhesus monkey head sizes (ages 4–8) and fits in the limited space provided by monkey stereotactic equipment and provides SNR gains in primary visual cortex and anatomical accuracy in conjunction with parallel imaging and improves resolution in fMRI experiments by a factor of 2 (1.25 mm to 1.0 mm isotropic) and diffusion MRI experiments by a factor of 4 (1.5 mm to 0.9 mm isotropic).

Khachaturian, Mark Haig

2010-01-01

45

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

Microsoft Academic Search

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.\\u000a \\u000a \\u000a \\u000a \\u000a 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,

Gregory Chang; Ligong Wang; Mark E. Schweitzer; Ravinder R. Regatte

2010-01-01

46

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

47

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

Microsoft Academic Search

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 the clinically useful contrasts they provide for assessing gross pathology. The practicality of measuring FSE-T2 relaxation properties has

Corinna M. Bauer; Hernán Jara; Ron Killiany

2010-01-01

48

Preattentive mechanisms of change detection in early auditory cortex: A 7Tesla fMRI study.  

PubMed

The auditory system continuously monitors the environment for irregularities in an automatic, preattentive fashion. This is presumably accomplished by two mechanisms: a sensory mechanism detects a deviant sound on the basis of differential refractoriness of neural populations sensitive to the standard and deviant sounds, whereas the cognitive mechanism reveals deviance by comparing incoming auditory information with a template derived from previous input. Using fast event-related high-resolution functional magnetic resonance imaging at 7Tesla we show that both mechanisms can be mapped to different parts of the auditory cortex both at the group level and the single-subject level. The sensory mechanism is supported by primary auditory areas in Heschl's gyrus whereas the cognitive mechanism is implemented in more anterior secondary auditory areas. Both mechanisms are equally engaged by simple sine-wave tones and speech-related phonemes indicating that streams of speech and non-speech stimuli are processed in a similar fashion. PMID:23994180

Szycik, G R; Stadler, J; Brechmann, A; Münte, T F

2013-08-30

49

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

50

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

51

Development of a geometrically accurate imaging protocol at 3 Tesla MRI for stereotactic radiosurgery treatment planning  

NASA Astrophysics Data System (ADS)

The purpose of this study is to develop a geometrically accurate imaging protocol at 3 T magnetic resonance imaging (MRI) for stereotactic radiosurgery (SRS) treatment planning. In order to achieve this purpose, a methodology is developed to investigate the geometric accuracy and stability of 3 T MRI for SRS in phantom and patient evaluations. Forty patients were enrolled on a prospective clinical trial. After frame placement prior to SRS, each patient underwent 3 T MRI after 1.5 T MRI and CT. MR imaging protocols included a T1-weighted gradient echo sequence and a T2-weighted spin echo sequence. Phantom imaging was performed on 3 T prior to patient imaging using the same set-up and imaging protocols. Geometric accuracy in patients and phantoms yielded comparable results for external fiducial reference deviations and internal landmarks between 3 T and 1.5 T MRI (mean <=0.6 mm; standard deviation <=0.3 mm). Mean stereotactic reference deviations between phantoms and patients correlated well (T1: R = 0.79; T2: R = 0.84). Statistical process control analysis on phantom QA data demonstrated the stability of our SRS imaging protocols, where the geometric accuracy of the 3 T SRS imaging protocol is operating within the appropriate tolerance. Our data provide evidence supporting the spatial validity of 3 T MRI for targeting SRS under imaging conditions investigated. We have developed a systematic approach to achieve confidence on the geometric integrity of a given imaging system/technique for clinical integration in SRS application.

Zhang, B.; MacFadden, D.; Damyanovich, A. Z.; Rieker, M.; Stainsby, J.; Bernstein, M.; Jaffray, D. A.; Mikulis, D.; Ménard, C.

2010-11-01

52

Combined MRI-PET scanner: a Monte Carlo evaluation of the improvements in PET resolution due to the effects of a static homogeneous magnetic field  

Microsoft Academic Search

Positron emission tomography (PET) relies upon the detection of photons resulting from the annihilation of positrons emitted by a radiopharmaceutical. The combination of images obtained with PET and magnetic resonance imaging (MRI) have begun to greatly enhance the study of many physiological processes. A combined MRI-PET scanner could alleviate much of the spatial and temporal coregistration difficulties currently encountered in

Raymond R. Raylman; Bruce E. Hammer; N. L. Christensen

1996-01-01

53

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

2013-04-03

54

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

55

Preliminary Experience Using Dynamic MRI at 3.0 Tesla for Evaluation of Soft Tissue Tumors  

PubMed Central

Objective We aimed to evaluate the use of dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) at 3.0 T for differentiating the benign from malignant soft tissue tumors. Also we aimed to assess whether the shorter length of DCE-MRI protocols are adequate, and to evaluate the effect of temporal resolution. Materials and Methods Dynamic contrast-enhanced magnetic resonance imaging, at 3.0 T with a 1 second temporal resolution in 13 patients with pathologically confirmed soft tissue tumors, was analyzed. Visual assessment of time-signal curves, subtraction images, maximal relative enhancement at the first (maximal peak enhancement [Emax]/1) and second (Emax/2) minutes, Emax, steepest slope calculated by using various time intervals (5, 30, 60 seconds), and the start of dynamic enhancement were analyzed. Results The 13 tumors were comprised of seven benign and six malignant soft tissue neoplasms. Washout on time-signal curves was seen on three (50%) malignant tumors and one (14%) benign one. The most discriminating DCE-MRI parameter was the steepest slope calculated, by using at 5-second intervals, followed by Emax/1 and Emax/2. All of the steepest slope values occurred within 2 minutes of the dynamic study. Start of dynamic enhancement did not show a significant difference, but no malignant tumor rendered a value greater than 14 seconds. Conclusion The steepest slope and early relative enhancement have the potential for differentiating benign from malignant soft tissue tumors. Short-length rather than long-length DCE-MRI protocol may be adequate for our purpose. The steepest slope parameters require a short temporal resolution, while maximal peak enhancement parameter may be more optimal for a longer temporal resolution.

Park, Michael Yong; Kim, Sun Ki; Lee, So-Yeon; Jung, Joon-Yong

2013-01-01

56

Pharmacokinetic parameters from 3-Tesla DCE-MRI as surrogate biomarkers of antitumor effects of bevacizumab plus FOLFIRI in colorectal cancer with liver metastasis.  

PubMed

Bevacizumab (BV) is an antivascular endothelial growth factor antibody. When administered with other chemotherapeutic drugs, BV-combined regimens prolong survival of colorectal cancer patients. We conducted a phase II trial to confirm the pharmacokinetic parameters from 3-Tesla dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) as surrogate biomarkers of BV + FOLFIRI regimen efficacy in colorectal cancer with liver metastases. DCE-MRI was performed before treatment, on the seventh day after first treatment and every 8 weeks thereafter using a 3-Tesla MRI system. DCE-MRI parameters-area under the contrast concentration versus time curve at 90 and 180 s (AUC90 and AUC180, respectively) after contrast injection, and volume transfer constant of contrast agents (K(trans) and K(ep) ) were calculated from liver metastases. Fifty-eight liver metastases were analyzed. Univariate analysis revealed that a decrease in K(trans) ratios (?K(trans) ), K(ep) ratios (?K(ep) ), AUC90 ratios (?AUC90) and AUC180 ratios (?AUC180) correlated with higher response (all p < 0.0001) and longer time to progression (TTP) (?K(trans) : p = 0.001; ?K(ep) : p = 0.004; ?AUC90: p = 0.006; ?AUC180: p < 0.0001). Multivariate analysis showed that ?AUC180 was correlated with higher response (p = 0.009), and ?K(trans) and ?AUC180 were correlated with longer TTP (?K(trans) : p = 0.001; ?AUC180: p = 0.024). ?K(trans) and ?AUC180 are pharmacodynamic biomarkers of the blood perfusion of BV + FOLFIRI. Our data suggest that ?K(trans) and ?K(ep) can predict response to chemotherapy at 1 week. Changes in 3-Tesla DCE-MRI parameters confirmed the potential of these biomarkers of blood perfusion as surrogate predictors of response and TTP. PMID:21780098

Hirashima, Yoshinori; Yamada, Yasuhide; Tateishi, Ukihide; Kato, Ken; Miyake, Mototaka; Horita, Yosuke; Akiyoshi, Kohei; Takashima, Atsuo; Okita, Natsuko; Takahari, Daisuke; Nakajima, Takako; Hamaguchi, Tetsuya; Shimada, Yasuhiro; Shirao, Kuniaki

2011-11-28

57

High-resolution MRI of the wrist and finger joints in patients with rheumatoid arthritis: comparison of 1.5 Tesla and 3.0 Tesla  

Microsoft Academic Search

The goal of this study was to compare magnetic resonance (MR) image quality at different field strengths for evaluating lesions\\u000a in wrist and finger joints of patients with rheumatoid arthritis (RA) in order to determine whether the higher field strength\\u000a provides diagnostic gain. The hand mainly affected in 17 RA patients was examined at 1.5 Tesla (T) and 3.0 T with comparable

Gero Wieners; Jacqueline Detert; Florian Streitparth; Maciej Pech; Frank Fischbach; Gerd Burmester; Jens Ricke; Marina Backhaus; Harald Bruhn

2007-01-01

58

A dichoptic projection system for visual psychophysics in fMRI scanners  

Microsoft Academic Search

Here we describe a projection system based on the combination of linear polarizing filters, designed to allow dichoptic presentation of visual stimuli during fMRI experiments. Currently available MRI compatible dichoptic presentation systems are either highly expensive, require degradation of the projected stimulus such as the removal of all but one color or are difficult to deploy in a range of

Benjamin Thompson; Reza Farivar; Bruce C. Hansen; Robert F. Hess

2008-01-01

59

First-Pass Contrast-Enhanced Myocardial Perfusion MRI in Mice on a 3-T Clinical MR Scanner  

PubMed Central

First-pass contrast-enhanced myocardial perfusion MRI in rodents has so far not been possible due to the temporal and spatial resolution requirements. We developed a new first-pass perfusion MR method for rodent imaging on a clinical 3.0-T scanner (Philips Healthcare, Best, The Netherlands) that employed 10-fold k-space and time domain undersampling with constrained image reconstruction, using temporal basis sets (k-t principle component analysis) to achieve a spatial resolution of 0.2 × 0.2 × 1.5mm3 and an acquisition window of 43 msec. The method was successfully tested in five healthy and four infarcted mice (C57BL/6J) at heart rates of 495.1 ± 45.8 beats/min. Signal-intensity-time profiles showed a percentage myocardial signal increase of 141.3 ± 38.9% in normal mice, compared with 44.7 ± 32.4% in infarcted segments. Mean myocardial blood flow by Fermi function for constrained deconvolution in control mice was 7.3 ± 1.5 mL/g/min, comparable to published literature, with no significant differences between three myocardial segments. In infarcted segments, myocardial blood flow was significantly reduced to 1.2 ± 0.8 mL/g/min (P < 0.01). This is the first report of first-pass myocardial perfusion MR in a mouse model on a clinical 3-T MR scanner and using a k-t undersampling method. Data were acquired on a 3-T scanner, using an approach similar to clinical acquisition protocols, thus facilitating translation of imaging findings between rodent and human studies. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.

Makowski, Marcus; Jansen, Christian; Webb, Ian; Chiribiri, Amedeo; Nagel, Eike; Botnar, Rene; Kozerke, Sebastian; Plein, Sven

2010-01-01

60

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

61

Performance Test of an LSO-APD Detector in a 7-T MRI Scanner for Simultaneous PET\\/MRI  

Microsoft Academic Search

PETcombined withCThasproventobe avaluablemultimodality imaging device revealing both functional and anatomic informa- tion. Although PET\\/CT has become completely integrated into routine clinical application and also has been used insmall-animal imaging, CT provides only limited soft-tissue contrast and, in preclinical studies, exposes the animal to a relatively high radia- tion dose. Unlike CT, MRI provides good soft-tissue contrast even without application of

Bernd J. Pichler; Martin S. Judenhofer; Ciprian Catana; Jeffrey H. Walton; Manfred Kneilling; Robert E. Nutt; Stefan B. Siegel; Claus D. Claussen; Simon R. Cherry

62

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

63

Wingspan stenting of symptomatic middle cerebral artery stenosis and perioperative evaluation using high-resolution 3 Tesla MRI  

Microsoft Academic Search

High-resolution MRI (HR MRI) was employed to study intracranial walls in a patient who underwent angioplasty and stenting for middle cerebral artery (MCA) stenosis using the Wingspan stent (Boston Scientific, Target). HR MRI clearly depicted the wall structure of the MCA. As a complementary method, HR MRI may improve intracranial atherosclerotic stenosis diagnosis and therapy.

MingChao Shi; ShouChun Wang; HongWei Zhou; YanHua Cheng; JiaChun Feng; Jiang Wu

64

Wingspan stenting of symptomatic middle cerebral artery stenosis and perioperative evaluation using high-resolution 3 Tesla MRI.  

PubMed

High-resolution MRI (HR MRI) was employed to study intracranial arterial walls in a patient who underwent angioplasty and stenting for middle cerebral artery (MCA) stenosis using the Wingspan stent (Boston Scientific, Natick, MA, USA). HR MRI clearly depicted the wall structure of the MCA. As a complementary method, HR MRI may improve intracranial atherosclerotic stenosis diagnosis and therapy. PMID:22341146

Shi, MingChao; Wang, ShouChun; Zhou, HongWei; Cheng, YanHua; Feng, JiaChun; Wu, Jiang

2012-02-15

65

Exposure, health complaints and cognitive performance among employees of an MRI scanners manufacturing department  

Microsoft Academic Search

Purpose: To assess sensory effects and other health com- plaints that are reported by system testers working near magnetic resonance imaging (MRI) magnets, realizing that it is believed that exposure up t o8Ti ssafe for humans. Materials and Methods: Levels of exposure to static mag- netic fields (SMFs), movement speed during exposure, health complaints, and cognitive performance among em- ployees

Frank de Vocht; Hinkelien van Drooge; Hans Engels; Hans Kromhout

2006-01-01

66

A combined solenoid-surface RF coil for high-resolution whole-brain rat imaging on a 3.0 Tesla clinical MR scanner.  

PubMed

Rat brain models effectively simulate a multitude of human neurological disorders. Improvements in coil design have facilitated the wider utilization of rat brain models by enabling the utilization of clinical MR scanners for image acquisition. In this study, a novel coil design, subsequently referred to as the rat brain coil, is described that exploits and combines the strengths of both solenoids and surface coils into a simple, multichannel, receive-only coil dedicated to whole-brain rat imaging on a 3.0 T clinical MR scanner. Compared with a multiturn solenoid mouse body coil, a 3-cm surface coil, a modified Helmholtz coil, and a phased-array surface coil, the rat brain coil improved signal-to-noise ratio by approximately 72, 61, 78, and 242%, respectively. Effects of the rat brain coil on amplitudes of static field and radiofrequency field uniformity were similar to each of the other coils. In vivo, whole-brain images of an adult male rat were acquired with a T(2)-weighted spin-echo sequence using an isotropic acquisition resolution of 0.25 x 0.25 x 0.25 mm(3) in 60.6 min. Multiplanar images of the in vivo rat brain with identification of anatomic structures are presented. Improvement in signal-to-noise ratio afforded by the rat brain coil may broaden experiments that utilize clinical MR scanners for in vivo image acquisition. PMID:20535812

Underhill, Hunter R; Yuan, Chun; Hayes, Cecil E

2010-09-01

67

Practice-induced changes of brain function during visual attention: a parametric fMRI study at 4 Tesla  

Microsoft Academic Search

A parametric functional MRI (fMRI) study with three levels of task difficulty was performed to determine the effect of practice and attentional load on brain activation during visual attention tasks. Brief practice during repeat fMRI scanning (20 min) did not change performance accuracy or reaction times (RT), but decreased activation bilaterally in the inferior, middle, and superior frontal gyri, superior

D. Tomasi; T. Ernst; E. C. Caparelli; L. Chang

2004-01-01

68

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

69

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

70

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

71

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

72

Evaluation of the partial flip angle spin echo method to improve non-uniformity in T1-weighted imaging with the 3-tesla MRI  

NASA Astrophysics Data System (ADS)

The higher signal-to-noise ratio (SNR) of 3-Tesla magnetic resonance imaging (3T MRI) contributes to an improvement in the spatial and temporal resolution. However, T1-weighted images of the brain obtained by the spin-echo (SE) method using 3T MRI are unsuitable for clinical use because of the inhomogeneity of the radio frequency (RF) field B1 non-uniformity. And it is clear by SE method. In addition, the prolongation of the longitudinal relaxation time (T1) of most tissues leads to a decrease in the T1 contrast. Therefore, many hospitals that utilize 3TMRI use the GRE method instead of the SE method in order to obtain an adequate T1 contrast, as can be obtained using FLASH (fast low angle shot), and high uniformity of images. Further, many studies have been performed to improve the non uniformity using techniques such as spatial presaturation. However, when filters are used, the high intensity of the influence in susceptible regions, signal deficits, and original contrast are lost, and a distortion can be clearly observed when the GRE method is used. Therefore, we obtained the T1-weighted images by using the partial flip angle SE method instead of the GRE method or SE method. We attempted to improve the image non-uniformity by using the partial flip angle SE method. Using this method, we could improve the image uniformity and also realize an adequate T1 contrast. As a result, the uniformity was found to improve by 6% and it became 82.6% at 110°. These results indicate that the use of the partial flip angle SE method is effective for obtaining adequate uniformity in the T1-weighted images of the brain.

Watanabe, Youhei; Tsuzaka, Masatoshi; Ishibashi, Kazuto; Sakurai, Yasuo

2008-04-01

73

Functional Magnetic Resonance Imaging of Eye Dominance at 4 Tesla  

Microsoft Academic Search

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

Atsushi Miki; Grant T. Liu; Sarah A. Englander; Theo G. M. van Erp; Gabrielle R. Bonhomme; David O. Aleman; Chia-Shang J. Liu; John C. Haselgrove

2001-01-01

74

In vivo detection of microscopic anisotropy using quadruple pulsed-field gradient (qPFG) diffusion MRI on a clinical scanner.  

PubMed

We report our design and implementation of a quadruple pulsed-field gradient (qPFG) diffusion MRI pulse sequence on a whole-body clinical scanner and demonstrate its ability to non-invasively detect restriction-induced microscopic anisotropy in human brain tissue. The microstructural information measured using qPFG diffusion MRI in white matter complements that provided by diffusion tensor imaging (DTI) and exclusively characterizes diffusion of water trapped in microscopic compartments with unique measures of average cell geometry. We describe the effect of white matter fiber orientation on the expected MR signal and highlight the importance of incorporating such information in the axon diameter measurement using a suitable mathematical framework. Integration of qPFG diffusion-weighted images (DWI) with fiber orientations measured using high-resolution DTI allows the estimation of average axon diameters in the corpus callosum of healthy human volunteers. Maps of inter-hemispheric average axon diameters reveal an anterior-posterior variation in good topographical agreement with anatomical measurements reported in previous post-mortem studies. With further technical refinements and additional clinical validation, qPFG diffusion MRI could provide a quantitative whole-brain histological assessment of white and gray matter, enabling a wide range of neuroimaging applications for improved diagnosis of neurodegenerative pathologies, monitoring neurodevelopmental processes, and mapping brain connectivity. PMID:22939872

Avram, Alexandru V; Özarslan, Evren; Sarlls, Joelle E; Basser, Peter J

2012-08-25

75

Patient-induced susceptibility effect on geometric distortion of clinical brain MRI for radiation treatment planning on a 3T scanner  

NASA Astrophysics Data System (ADS)

Concerns about the geometric accuracy of MRI in radiation therapy (RT) have been present since its invention. Although modern scanners typically have system levels of geometric accuracy that meet requirements of RT, subject-specific distortion is variable, and methods to in vivo assess and control patient-induced geometric distortion are not yet resolved. This study investigated the nature and magnitude of the subject-induced susceptibility effect on geometric distortions in clinical brain MRI, and tested the feasibility of in vivo quality control using field inhomogeneity mapping. For 19 consecutive patients scanned on a dedicated 3T MR scanner, B0 field inhomogeneity maps were acquired and analyzed to determine subject-induced distortions. For 3D T1 weighted images frequency-encoded with a bandwidth of 180 Hz/pixel, 86.9% of the estimated displacements were <0.5 mm, 97.4% <1 mm, and only 0.1% of displacements > 2 mm. The maximum displacement was <4 mm. The greatest distortions were observed at the interfaces with air at the sinuses. Displacements decayed to less than 1 mm over a distance of 8 mm. Metal surgical wires generated smaller distortions, with an averaged maximum displacement of 0.76 mm. Repeat acquisition of the field maps in 17 patients revealed a within-subject standard deviation of 0.25 ppm, equivalent to 0.22 mm displacement in the frequency-encoding direction in the 3D T1 weighted images. Susceptibility-induced voxel displacements in the brain are generally small, but should be monitored for precision RT. These effects are manageable at 3T and lower fields, and the methods applied can be used to monitor for potential local errors in individual patients, as well as to correct for local distortions as needed.

Wang, H.; Balter, J.; Cao, Y.

2013-02-01

76

Haptic fMRI: Combining functional neuroimaging with haptics for studying the brain's motor control representation.  

PubMed

A challenging problem in motor control neuroimaging studies is the inability to perform complex human motor tasks given the Magnetic Resonance Imaging (MRI) scanner's disruptive magnetic fields and confined workspace. In this paper, we propose a novel experimental platform that combines Functional MRI (fMRI) neuroimaging, haptic virtual simulation environments, and an fMRI-compatible haptic device for real-time haptic interaction across the scanner workspace (above torso ? .65×.40×.20m(3)). We implement this Haptic fMRI platform with a novel haptic device, the Haptic fMRI Interface (HFI), and demonstrate its suitability for motor neuroimaging studies. HFI has three degrees-of-freedom (DOF), uses electromagnetic motors to enable high-fidelity haptic rendering (>350Hz), integrates radio frequency (RF) shields to prevent electromagnetic interference with fMRI (temporal SNR >100), and is kinematically designed to minimize currents induced by the MRI scanner's magnetic field during motor displacement (<2cm). HFI possesses uniform inertial and force transmission properties across the workspace, and has low friction (.05-.30N). HFI's RF noise levels, in addition, are within a 3 Tesla fMRI scanner's baseline noise variation (?.85±.1%). Finally, HFI is haptically transparent and does not interfere with human motor tasks (tested for .4m reaches). By allowing fMRI experiments involving complex three-dimensional manipulation with haptic interaction, Haptic fMRI enables-for the first time-non-invasive neuroscience experiments involving interactive motor tasks, object manipulation, tactile perception, and visuo-motor integration. PMID:24110643

Menon, Samir; Brantner, Gerald; Aholt, Chris; Kay, Kendrick; Khatib, Oussama

2013-07-01

77

Tumor Volume Changes on 1.5 Tesla Endorectal MRI During Neoadjuvant Androgen Suppression Therapy for Higher-Risk Prostate Cancer and Recurrence in Men Treated Using Radiation Therapy Results of the Phase II CALGB 9682 Study  

SciTech Connect

Purpose: We prospectively determined whether the change in tumor volume (TV) during 2 months of neoadjuvant androgen suppression therapy (nAST) measured using conventional 1.5 Tesla endorectal magnetic resonance imaging (eMRI) was associated with the risk of recurrence after radiation (RT) and 6 months of AST. Patients and Methods: Between 1997 and 2001, 180 men with clinical stage T1c-T3cN0M0 adenocarcinoma of the prostate were registered. Fifteen were found to be ineligible and the institutional MR radiologist could not assess the TV in 32, leaving 133 for analysis. Multivariable Cox regression analysis was used to assess whether a significant association existed between eMRI-defined TV progression during nAST and time to recurrence adjusting for prostate-specific antigen (PSA) level, Gleason score (8 to 10 or 7 vs. 6 or less) and stage (T3 vs. T1-2). Results: After a median follow up of 6.7 years and adjusting for known prognostic factors, there was a significant increase in the risk of PSA failure (HR, 2.3 [95% CI, 1.1-4.5; p = 0.025) in men with eMRI-defined TV progression during nAST. Specifically, adjusted estimates of PSA failure were significantly higher (p = 0.032) in men with, compared with men without, eMRI-defined TV progression reaching 38% vs. 19%, respectively, by 5 years. Conclusion: Eradicating intraprostatic hormone refractory prostate cancer (HRPC) by maximizing local control and randomized trials assessing whether survival is improved when agents active against HRPC are combined with maximal local therapy are needed in men who progress based on eMRI during nAST.

D'Amico, Anthony V. [Brigham and Women's Hospital and Dana-Farber Cancer Institute, Boston, MA (United States)], E-mail: adamico@partners.org; Halabi, Susan [CALGB Statistical Center, Duke University Medical Center, Durham, NC (United States); Tempany, Clare; Titelbaum, David [Brigham and Women's Hospital and Dana-Farber Cancer Institute, Boston, MA (United States); Philips, George K. [University of Vermont Cancer Center, Burlington, VT (United States); Loffredo, Marian; McMahon, Elizabeth [Brigham and Women's Hospital and Dana-Farber Cancer Institute, Boston, MA (United States); Sanford, Ben [CALGB Statistical Center, Duke University Medical Center, Durham, NC (United States); Vogelzang, Nicholas J. [Las Vegas Cancer Center, Las Vegas, NV (United States); Small, Eric J. [University of California at San Francisco, San Francisco, CA (United States)

2008-05-01

78

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

79

Response competition and response inhibition during different choice-discrimination tasks: evidence from ERP measured inside MRI scanner.  

PubMed

We investigated the neural correlates underlying response inhibition and conflict detection processes using ERPs and source localization analyses simultaneously acquired during fMRI scanning. ERPs were elicited by a simple reaction time task (SRT), a Go/NoGo task, and a Stroop-like task (CST). The cognitive conflict was thus manipulated in order to probe the degree to which information processing is shared across cognitive systems. We proposed to dissociate inhibition and interference conflict effects on brain activity by using identical Stroop-like congruent/incongruent stimuli in all three task contexts and while varying the response required. NoGo-incongruent trials showed a larger N2 and enhanced activations of rostral anterior cingulate cortex (ACC) and pre-supplementary motor area, whereas Go-congruent trials showed a larger P3 and increased parietal activations. Congruent and incongruent conditions of the CST task also elicited similar N2, P3 and late negativity (LN) ERPs, though CST-incongruent trials revealed a larger LN and enhanced prefrontal and ACC activations. Considering the stimulus probability and experimental manipulation of our study, current findings suggest that NoGo N2 and frontal NoGo P3 appear to be more associated to response inhibition rather than a specific conflict monitoring, whereas occipito-parietal P3 of Go and CST conditions may be more linked to a planned response competition between the prepared and required response. LN, however, appears to be related to higher level conflict monitoring associated with response choice-discrimination but not when the presence of cognitive conflict is associated with response inhibition. PMID:23664841

Gonzalez-Rosa, Javier J; Inuggi, Alberto; Blasi, Valeria; Cursi, Marco; Annovazzi, Pietro; Comi, Giancarlo; Falini, Andrea; Leocani, Letizia

2013-05-09

80

Ultrashort Echo Time Magnetic Resonance Imaging of Cortical Bone at 7 Tesla Field Strength: A Feasibility Study  

PubMed Central

Purpose To implement and examine the feasibility of a 3D ultra-short TE (UTE) sequence on a 7T clinical MR scanner in comparison with 3T MRI at high isotropic resolution. Materials and Methods Using an in-house built saddle coil at both field strengths we have imaged mid-diaphysial sections of five fresh cadaveric specimen of the distal tibia. An additional in vivo scan was performed at 7 Tesla using a quadrature knee coil. Results Using the same type of saddle coil at both field strengths a significant increase in SNR at 7T compared to 3T (factor 1.7) was found. Significantly shorter T2* values were found at the higher field strength (T2*=552.2±126µs at 7T versus T2*=1163±391µs at 3T). Conclusions UHF MRI at 7T has great potential for imaging tissues with short T2.

Krug, Roland; Larson, Peder Eric Zufall; Wang, Chunsheng; Burghardt, Andrew J.; Kelley, Douglas A. C.; Link, Thomas M.; Zhang, Xiaoliang; Vigneron, Daniel B.; Majumdar, Sharmila

2011-01-01

81

An fMRI-compatible multi-configurable handheld response system using an intensity-modulated fiber-optic sensor.  

PubMed

Functional magnetic resonance imaging (fMRI) data should be interpreted in combination and in the context of relevant behavioral measurements. However, the strong magnetic environment of MRI scanner and the supine position of participants in the scanner significantly limit how participants' behavioral responses are recorded. This paper presents the design of a low-cost handheld response system (HRS) with a multi-configurable optomechanical design that utilizes a reflective-type intensity modulated fiber-optic sensor (FOS) and a programmable visual interface to accurately gather participants' behavioral responses during an fMRI experiment. Considering the effects of an input unit design on the participants' performance efficiency across age groups and physical and neurological (dis)ability, the optomechanical system is designed to provide flexibility in the range of an input module with easy change-out feature. Specifically, the input unit can be configured as a binary module such as push buttons or as an analog input device including a scrolling wheel, and one-dimensional joystick (lever arm). To achieve MRI-compatibility, all parts of the unit that are used inside the scanner bore are built from nonferromagnetic and off-the-shelf plastic materials. The MRI compatibility was evaluated on a 3.0 Tesla MRI scanner running echo planar imaging (EPI) and the average time-variant signal-to-noise ratio (tSNR) loss is limited to 2%. PMID:24111193

Jarrahi, Behnaz; Wanek, Johann; Mehnert, Ulrich; Kollias, Spyros

2013-07-01

82

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

83

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  

NASA Astrophysics Data System (ADS)

We report metabolic images of 13C, following injection of a bolus 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

2011-01-01

84

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

85

Ct scanner  

SciTech Connect

A ct scanner is described in which the data acquisition components, I.E. The radiation source and detectors, are mounted in an apertured housing which can be deployed generally vertically, for the examination of recumbent patients, or generally horizontally, for the examination of patients seated, or standing, with their torsos upright.

Bernardi, R.T.

1982-02-16

86

Relaxation time measurements of bone marrow protons in the calcaneus using a compact MRI system at 0.2 Tesla field strength  

Microsoft Academic Search

Relaxation times (T1 and T2) of the bone marrow protons and trabecular bone volume fraction (TBVF) in the calcaneus were measured for 100 female volunteers using a compact MRI sys- tem at 0.2 T field strength. The speed of sound (SOS) through the calcaneus was measured also for the same subjects using a quantitative ultrasound system. Both relaxation times were

Sadanori Tomiha; Nachiko Iita; Fumi Okada; Shinya Handa; Katsumi Kose

2008-01-01

87

Photon collider at TESLA  

Microsoft Academic Search

High energy photon colliders (??,?e) based on backward Compton scattering of laser light is a very natural addition to e+e? linear colliders. In this report, we consider this option for the TESLA project. Recent study has shown that the horizontal emittance in the TESLA damping ring can be further decreased by a factor of four. In this case, the ??

Valery Telnov

2001-01-01

88

The TESLA RF System  

NASA Astrophysics Data System (ADS)

The TESLA project proposed by the TESLA collaboration in 2001 is a 500 to 800GeV e+/e- linear collider with integrated free electron laser facility. The accelerator is based on superconducting cavity technology. Approximately 20000 superconducting cavities operated at 1.3GHz with a gradient of 23.4MV/m or 35MV/m will be required to achieve the energy of 500GeV or 800GeV respectively. For 500GeV ~600 RF stations each generating 10MW of RF power at 1.3GHz at a pulse duration of 1.37ms and a repetition rate of 5 or 10Hz are required. The original TESLA design was modified in 2002 and now includes a dedicated 20GeV electron accelerator in a separate tunnel for free electron laser application. The TESLA XFEL will provide XFEL radiation of unprecedented peak brilliance and full transverse coherence in the wavelength range of 0.1 to 6.4nm at a pulse duration of 100fs. The technology of both accelerators, the TESLA linear collider and the XFEL, will be identical, however the number of superconducting cavities and RF stations for the XFEL will be reduced to 936 and 26 respectively. This paper describes the layout of the entire RF system of the TESLA linear collider and the TESLA XFEL and gives an overview of its various subsystems and components.

Choroba, S.

2003-12-01

89

Assessing the Accuracy and Precision of Musculoskeletal Motion Tracking Using Cine-PC MRI on a 3.0 Tesla Platform  

PubMed Central

The rising cost of musculoskeletal pathology, disease, and injury creates a pressing need for accurate and reliable methods to quantify 3D musculoskeletal motion, fostering a renewed interest in this area over the past few years. To date, cine-phase contrast (PC) MRI remains the only technique capable of non-invasively tracking in vivo 3D musculoskeletal motion during volitional activity, but current scan times are long on the 1.5T MR platform (~2.5 minutes or 75 movement cycles). With the clinical availability of higher field strength magnets (3.0T) that have increased signal-to-noise ratios, it is likely that scan times can be reduced while improving accuracy. Therefore, the purpose of this study was to validate cine-PC MRI on a 3.0T platform, in terms of accuracy, precision and subject-repeatability, and to determine if scan time could be minimized. On the 3.0T platform it is possible to limit scan time to 2 minutes, with sub-millimeter accuracy (<0.33mm/0.97°), excellent technique precision (<0.18°), and strong subject-repeatability (<0.73 mm/1.10°). This represented a reduction in imaging time by 25% (42 seconds), a 50% improvement in accuracy, and a 72% improvement in technique precision over the original 1.5T platform. Scan time can be reduced to 1 minute (30 movement cycles), but the improvements in accuracy are not as large.

Behnam, Abrahm J.; Herzka, Daniel A.; Sheehan, Frances T.

2011-01-01

90

Superconducting TESLA cavities  

Microsoft Academic Search

The conceptional design of the proposed linear electron-positron collider TESLA is based on 9-cell 1.3 GHz superconducting niobium cavities with an accelerating gradient of Eacc>=25 MV\\/m at a quality factor Q0>=5×109. The design goal for the cavities of the TESLA Test Facility (TTF) linac was set to the more moderate value of Eacc>=15 MV\\/m. In a first series of 27

B. Aune; R. Bandelmann; D. Bloess; B. Bonin; A. Bosotti; M. Champion; C. Crawford; G. Deppe; B. Dwersteg; D. A. Edwards; H. T. Edwards; M. Ferrario; M. Fouaidy; P.-D. Gall; A. Gamp; A. Gössel; J. Graber; D. Hubert; M. Hüning; M. Juillard; T. Junquera; H. Kaiser; G. Kreps; M. Kuchnir; R. Lange; M. Leenen; M. Liepe; L. Lilje; A. Matheisen; W.-D. Möller; A. Mosnier; H. Padamsee; C. Pagani; M. Pekeler; H.-B. Peters; O. Peters; D. Proch; K. Rehlich; D. Reschke; H. Safa; T. Schilcher; P. Schmüser; J. Sekutowicz; S. Simrock; W. Singer; M. Tigner; D. Trines; K. Twarowski; G. Weichert; J. Weisend; J. Wojtkiewicz; S. Wolff; K. Zapfe

2000-01-01

91

Anatomical, BOLD, blood-flow MRI of non-human primate (baboon) retina  

PubMed Central

The goal of this study was to demonstrate high-resolution anatomical, BOLD (blood-oxygenation-level-dependent), and blood-flow (BF) MRI on large non-human primate (NHP) retinas using a 3-Tesla clinical scanner as a first step toward translation. Baboon was chosen because of its evolutionary similarity to human. Anesthetized preparation, free of eye-movement artifacts, was used to evaluate clinical scanner hardware feasibility. Anatomical MRI (0.1×0.2×2.0 mm) before contrast-agent injection detected three alternating bright-dark-bright layers. The hyperintense inner strip nearest to the vitreous was enhanced by an intravascular contrast agent, likely included the ganglion and bipolar cell layer and the embedded retinal vessels. The hypointense middle strip showed no contrast enhancement, likely included the avascular outer unclear layer and photoreceptor segments. The hyperintense outer strip showed contrast enhancement, likely corresponded to the choroid vascular layer. In the posterior retina, the total thickness including the choroid was 617±101µm (±SD, n=7). BOLD fMRI (0.3×0.6×2.0 mm) of oxygen inhalation relative to air increased 6.5±1.4%. Basal BF (2×2×2mm) was 83±30mL/100g/min (air), and hypercapnia increased BF by 25±9% (P<0.05). This study demonstrates multimodal MRI to image anatomy, physiology and function on large NHP retinas using a clinical scanner, offering encouraging data to explore human applications.

Zhang, Yi; Wey, Hsiao-Ying; Nateras, Oscar San Emeterio; Peng, Qi; De La Garza, Bryan H.; Duong, Timothy Q

2011-01-01

92

Feasibility of in vivo quantitative MRI with DWI, T2-relaxometry and DTI in a clinical 3T MR scanner for the acute traumatic spinal cord injury of rats: technical note.  

PubMed

Study Design: prospective longitudinal study.Objective: to verify the feasibility of performing in vivo quantitative MRI evaluation of moderate traumatic spinal cord injury in rats using a clinical 3T scanner.Summary of Background Data: animal models of human diseases are essential for translational medicine. Potential treatments for spinal cord injury (SCI) are evaluated in two ways: anatomical and functional. Advanced MR sequences allow a noninvasive assessment of the spinal cord depicting both. This study describes and validates a very reproducible, feasible, affordable and reliable method, designed to be applied in commercial 3T equipment, using a novel stereotactic device for spinal cord leading to a readily available assessment of the progression of damage generated after traumatic spinal cord injury in rats.Methods: four Long Evans female rats were injured with a NYU (New York University) weight-drop device in order to produce the SCI by contusion at thoracic level 10. All animals were placed in a fixation system, using a commercial wrist antenna in order to obtain MRI data of the relaxometry-time, apparent diffusion coefficient (ADC) and fractional anisotropy (FA). Three sets of data were compared taken before SCI, 1 week and 4 weeks after injury.Results: the data showed a progressive decline in FA measurements after SCI comparing baseline vs. the 1-week (p < 0.001) and baseline vs. the 4-weeks period p < 0.019); with a significant progressive increase in ADC values and T2 after SCI only in the baseline vs. the 4-weeks period (p < 0.045 and p < 0.024, respectively).Conclusion: our results helped us to validate a novel method to acquire highly reproducible and reliable quantitative biomarkers of traumatic SCI in vivo by using a 3T clinical MR scanner coupled with a novel stereotactic device for rats. PMID:24042725

Mondragon-Lozano, Rodrigo; Diaz-Ruiz, Araceli; Ríos, Camilo; Olayo Gonzalez, Roberto; Favila, Rafael; Salgado-Ceballos, Hermelinda; Roldan-Valadez, Ernesto

2013-09-15

93

The TESLA RF System  

Microsoft Academic Search

The TESLA project proposed by the TESLA collaboration in 2001 is a 500 to 800GeV e+\\/e- linear collider with integrated free electron laser facility. The accelerator is based on superconducting cavity technology. Approximately 20000 superconducting cavities operated at 1.3GHz with a gradient of 23.4MV\\/m or 35MV\\/m will be required to achieve the energy of 500GeV or 800GeV respectively. For 500GeV

S. Choroba

2003-01-01

94

The TESLA free electron laser  

Microsoft Academic Search

The TESLA free Electron Laser (FEL) makes use of the high electron beam quality that can be provided by the superconducting TESLA linac to drive a single pass FEL at wavelengths far below the visible. To reach a wavelength of 6 nanometers, the TESLA Test Facility (TTF) currently under construction at DESY is extended to 1 GeV beam energy. Because

Jörg Rossbach

1997-01-01

95

The TESLA free electron laser  

Microsoft Academic Search

The TESLA Free Electron Laser (FEL) makes use of the high electron beam quality that can be provided by the su- perconducting TESLA linac to drive a single pass FEL at wavelengths far below the visible. To reach a wavelength of 6 nanometers, the TESLA Test Facility (TTF) currently under construction at DESY will be extended to 1 GeV beam

J. Rossbach

1998-01-01

96

Photon collider at TESLA  

NASA Astrophysics Data System (ADS)

High energy photon colliders (??,?e) based on backward Compton scattering of laser light is a very natural addition to e+e- linear colliders. In this report, we consider this option for the TESLA project. Recent study has shown that the horizontal emittance in the TESLA damping ring can be further decreased by a factor of four. In this case, the /?? luminosity in the high energy part of spectrum can reach about (1/3)Le+e-. Typical cross-sections of interesting processes in /?? collisions are higher than those in e+e- collisions by about one order of magnitude, so the number of events in /?? collisions will be more than that in e+e- collisions. Photon colliders can, certainly, give additional information and they are the best for the study of many phenomena. The main question is now the technical feasibility. The key new element in photon colliders is a very powerful laser system. An external optical cavity is a promising approach for the TESLA project. A free electron laser is another option. However, a more straightforward solution is ``an optical storage ring (optical trap)'' with a diode pumped solid state laser injector which is today technically feasible. This paper briefly reviews the status of a photon collider based on the linear collider TESLA, its possible parameters and existing problems.

Telnov, Valery

2001-10-01

97

MRI  

NSDL National Science Digital Library

This patient education program explains Magnetic Resonance Imaging (MRI), the role of this imaging in diagnosis, the procedure itself, and associated benefits and risks. This is a MedlinePlus Interactive Health Tutorial from the National Library of Medicine, designed and developed by the Patient Education Institute. NOTE: The tutorial requires a special Flash plug-in, version 4 or above. If you do not have Flash, you will be prompted to obtain a free download of the software before you start the tutorial. You will also need an Acrobat Reader, available as a free download, in order to view the Reference Summary.

Institute, Patient E.

2008-09-10

98

Miniaturized fiber-optic transmission system for MRI signals.  

PubMed

Conventional MRI instruments transmit received MRI signals through electrical cables. Although this design has proved to be effective over the years, we report a fiber-optic system that addresses the needs of recent developments in MRI technology. One of these technologies is phased array coils with a high number of elements, where total size of interconnections is a primary problem, and other problem is internal MRI coils, where there is a need for improvements in safety. The Miniature Fiber-Optic Transmission (FOT) System was developed to address these issues. The system consists of a receiver coil with active detuning, a low-noise preamplifier, and a laser diode connected to a photodetector with fiber-optic cabling. The overall noise figure of the system is lower than 1 dB. Total power consumption is 50 mW, and the device is switchable with another fiber-optic line, which can also control active detuning. A prototype device was tested in a GE 1.5 Tesla MRI scanner, and several images were acquired with a signal to noise ratio similar to coaxial cabling. We believe that this design will reduce the cabling problems of arrays and enable placement of internal coils into body cavities with no safety hazard to the patient, such as electrical shock or burns. PMID:18098294

Memis, Omer Gokalp; Eryaman, Yigitcan; Aytur, Orhan; Atalar, Ergin

2008-01-01

99

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

SciTech Connect

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

Fischbach, Frank, E-mail: frank.fischbach@med.ovgu.de [Otto von Guericke University, Department of Radiology, Medical School (Germany); Bunke, Juergen [Philips Healthcare (Germany); Thormann, Markus; Gaffke, Gunnar; Jungnickel, Kerstin [Otto von Guericke University, Department of Radiology, Medical School (Germany); Smink, Jouke [Philips Healthcare (Germany); Ricke, Jens [Otto von Guericke University, Department of Radiology, Medical School (Germany)

2011-02-15

100

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

101

Pharmacological MRI of the choroid and retina: blood flow and BOLD responses during nitroprusside infusion  

PubMed Central

Nitroprusside, a vasodilatorynitric oxide donor, is clinically used during vascular surgery and to lower blood pressure in acute hypertension. This paper reports a novel application of blood flow (BF) and blood-oxygenation-level-dependent (BOLD) MRI on a 11.7 Tesla scanner to image the rat chorioretinal BF and BOLD changes associated with graded nitroprusside infusion. At low doses (1 or 2 ?g/kg/min), nitroprusside increased BF as expected but decreased BOLD signals, showing an intriguing BF-BOLD uncoupling. At high doses (3–5 ?g/kg/min) nitroprusside decreased BF and markedly decreased BOLD signals. To our knowledge, this is the first pharmacological MRI application of the retina. This approach has potential to open up new avenues to study the drug-related hemodynamic functions and evaluate the effects of novel therapeutic interventions on BOLD and BF in the normal and diseased retinas.

Shih, Yen-Yu I.; Li, Guang; Muir, Eric R; De La Garza, Bryan H; Kiel, Jeffrey W; Duong, Timothy Q.

2012-01-01

102

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

103

Artifacts and pitfalls in diffusion MRI  

Microsoft Academic Search

Although over the last 20 years diffusion MRI has become an established technique with a great impact on health care and neurosciences, like any other MRI technique it remains subject to artifacts and pitfalls. In addition to common MRI artifacts, there are specific problems that one may encounter when using MRI scanner gradient hard- ware for diffusion MRI, especially in

Denis Le Bihan; Cyril Poupon; Alexis Amadon; Franck Lethimonnier

2006-01-01

104

PBS: Tesla - Master of Lightning  

NSDL National Science Digital Library

This web site explores the life and legacy of Nikola Tesla, an important contributor to the field of electromagnetism. Although the significance of his work is often minimized, Tesla's work formed the basis of modern alternating current power systems and wireless transmission of energy. He was the first to receive a patent for the invention of the radio, though Marconi is more often given credit for the discovery. The web site includes interactive explorations of Tesla's key inventions and lesson plans for grades 6-12 on electric potential and conversion of electrical energy into mechanical energy. Users will also find selected articles on Tesla, timelines of electricity and radio, and a link to view selected Tesla patents.

2010-06-24

105

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

106

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

107

The TESLA Free Electron Laser  

Microsoft Academic Search

Abstract The TESLA Free Electron Laser [1] is an ultra-brilliant X-regime light source (XFEL). It adopts the lasing prin- ciple of self-amplified spontaneous,emission (SASE). To demonstrate the feasibility of the SASE principle at short wavelength, DESY is now pushing, in the frame of inter- national collaboration, to constructing an FEL test facility (TTF FEL) in parallel with the TESLA Test

M. Zhang

108

Synergistic Enhancement of Iron Oxide Nanoparticle and Gadolinium for Dual-Contrast MRI  

PubMed Central

Purpose The use of MR contrast agents allows accurate diagnosis by exerting an influence on the longitudinal (T1) or transverse (T2) 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 T2 weighted DC MRI with IO administered first, then followed by the injection of a bolus of gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). Results Quantified with 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 T2 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; Huang, Xinglu; Qian, Chunqi; Zhu, Lei; Hida, Naoki; Niu, Gang; Chen, Xiaoyuan

2012-01-01

109

Underwater Radiance Scanner.  

National Technical Information Service (NTIS)

The Underwater Radiance Scanner was developed to measure radiance distributions of natural light fields underwater. It was deployed in a series of experiments designed to validate a model describing propagation of optical energy from a satellite to an und...

R. D. Anderson

1976-01-01

110

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

111

Gd-EOB-DTPA-enhanced 3.0-Tesla MRI findings for the preoperative detection of focal liver lesions: Comparison with iodine-enhanced multi-detector computed tomography  

NASA Astrophysics Data System (ADS)

The safety of gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic-acid (Gd-EOB-DTPA) has been confirmed, but more study is needed to assess the diagnostic accuracy of Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) in patients with a hepatocellular carcinoma (HCC) for whom surgical treatment is considered or with a metastatic hepatoma. Research is also needed to examine the rate of detection of hepatic lesions compared to multi-detector computed tomography (MDCT), which is used most frequently to localize and characterize a HCC. Gd-EOB-DTPA-enhanced MRI and iodine-enhanced MDCT imaging were compared for the preoperative detection of focal liver lesions. The clinical usefulness of each method was examined. The current study enrolled 79 patients with focal liver lesions who preoperatively underwent MRI and MDCT. In these patients, there was less than one month between the two diagnostic modalities. Imaging data were taken before and after contrast enhancement in both methods. To evaluate the images, we analyzed the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) in the lesions and the liver parenchyma. To compare the sensitivity of the two methods, we performed a quantitative analysis of the percentage signal intensity of the liver (PSIL) on a high resolution picture archiving and communication system (PACS) monitor (paired-samples t-test, p < 0.05). The enhancement was evaluated based on a consensus of four observers. The enhancement pattern and the morphological features during the arterial and the delayed phases were correlated between the Gd-EOB-DTPA-enhanced MRI findings and the iodine-enhanced MDCT by using an adjusted x2 test. The SNRs, CNRs, and PSIL all had a greater detection rate in Gd-EOB-DTPA enhanced MRI than in iodine-enhanced MDCT. Hepatocyte-selective uptake was observed 20 minutes after the injection in the focal nodular hyperplasia (FNH, 9/9), adenoma (9/10), and highly-differentiated HCC (grade G1, 27/30). Rim enhancement was detected in all metastases (30/30). During the arterial and the delayed phases, good overall agreement between the gadoxetic-acid-enhanced MR and CT was observed (x2 test, p < 0.05). For the preoperative detection of focal liver lesions, Gd-EOB-DTPA-enhanced MRI had a higher diagnostic value and higher detection rate than iodine-enhanced MDCT. The arterial and the delayed dynamic enhancement patterns, and the gadoxetic-acid-enhanced MR imaging can provide information on the possible degree of cellular differentiation of a HCC, adenoma or metastatic tumor.

Park, Hyong-Hu; Goo, Eun-Hoe; Im, In-Chul; Lee, Jae-Seung; Kim, Moon-Jib; Kwak, Byung-Joon; Chung, Woon-Kwan; Dong, Kyung-Rae

2012-12-01

112

The TESLA Free Electron Laser  

NASA Astrophysics Data System (ADS)

The TESLA Free Electron Laser makes use of the high quality electron beam that can be provided by the superconducting TESLA linac to drive a single pass free electron laser (FEL) at wavelengths far below the visible. To reach a wavelength of 6 nanometers, the TESLA Test Facility (TTF) currently under construction at DESY will be extended to 1 GeV beam energy. Because there are no mirrors and seed-lasers in this wavelength regime, the principle of Self-Amplified-Spontaneous-Emission (SASE) will be employed. A first test of both the principle and technical components is foreseen at a photon wavelength larger than 42 nanometers. With respect to linac technology, the key prerequisite for such single-pass, high-gain FELs is a high intensity, diffraction limited, electron beam to be generated and accelerated without degradation. Key components are RF guns with photocathodes, bunch compressors, and related diagnostics. The status of design and construction as well as both electron and photon beam properties will be discussed. Once proven in the micrometer to nanometer regime, the SASE FEL scheme is considered applicable down to Angstrom wavelengths. It is pointed out that this latter option is particularly of interest in context with the construction of a linear collider, which requires very similar beam parameters. The status of conceptual design work on such a coherent X-ray user facility integrated into the TESLA linear collider design will be briefly sketched.

Rossbach, Jörg

1997-05-01

113

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

114

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

115

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

116

High gamma-aminobutyric acid level in cortical tubers in epileptic infants with tuberous sclerosis complex measured with the MEGA-editing J-difference method and a three-Tesla clinical MRI Instrument.  

PubMed

The purpose of this study was to estimate the gamma-aminobutyric acid (GABA) and glutamate plus glutamine (Glx) concentrations in the cortical tubers of patients with tuberous sclerosis complex (TSC) using the MEGA-editing J-difference method and a stimulated echo-acquisition mode with a short echo time, and to determine which abnormality was more dominant between GABA and Glx in patients with TSC with epilepsy. This study included six patients with TSC (mean age, 4.3 years) and seven control subjects (mean age, 4.8 years). Measurements were obtained with a three-Tesla apparatus and postprocessing was conducted with an LCModel. The GABA level in the cortical gray matter (cgGABA) was calculated as a result of segmentation in voxels and from the literature values for gray and white matter ratios for GABA. Increased GABA and myo-inositol (mI) concentrations and a decreased N-acetyl aspartate (NAA) concentration were observed in the cortical tubers. The cgGABA level, and cgGABA/NAA and cgGABA/Glx ratios were also higher in patients with TSC than in control subjects. No significant difference was found in Glx concentration between patients with TSC and control subjects. Although the number of patients with TSC in this study was small, the increase in GABA and no significant change in Glx were consistent with previous neurochemical studies and support the hypothesis that brain GABA plays a key role in the pathophysiology of epilepsy during the process of neuronal development. PMID:19481612

Taki, Masako Minato; Harada, Masafumi; Mori, Kenji; Kubo, Hitoshi; Nose, Ayumi; Matsuda, Tsuyoshi; Nishitani, Hiromu

2009-05-28

117

Accuracy of MRI patterns in evaluating anterior cruciate ligament tears  

Microsoft Academic Search

The purpose of this study was to determine the different patterns of anterior cruciate ligament (ACL) tears on MRI and the\\u000a prevalence and accuracy of these patterns. Images were obtained on high-tesla and low-tesla units and the results compared\\u000a to determine whether field strength affects the interpretation using the grading system. In 172 patients who underwent knee\\u000a MRI (109 knees

Kevin P. Barry; Mamed Mesgarzadeh; Joseph Triolo; Ray Moyer; Jamshid Tehranzadeh; Akbar Bonakdarpour

1996-01-01

118

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

119

Optical fuel pin scanner  

DOEpatents

An optical scanner for indicia arranged in a focal plane at a cylindrical outside surface by use of an optical system including a rotatable dove prism. The dove prism transmits a rotating image of an encircled cylindrical surface area to a stationary photodiode array.

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

1983-01-01

120

Interpreting scan data acquired from multiple scanners: a study with Alzheimer's disease.  

PubMed

Large, multi-site studies utilizing MRI-derived measures from multiple scanners present an opportunity to advance research by pooling data. On the other hand, it remains unclear whether or not the potential confound introduced by different scanners and upgrades will devalue the integrity of any results. Although there are studies of scanner differences for the purpose of calibration and quality control, the current literature is devoid of studies that describe the analysis of multi-scanner data with regard to the interaction of scanner(s) with effects of interest. We investigated a data-set of 136 subjects, 62 patients with mild to moderate Alzheimer's disease and 74 cognitively normal elderly controls, with MRI scans from one center that were acquired over 10 years with 6 different scanners and multiple upgrades over time. We used a whole-brain voxel-wise analysis to evaluate the effect of scanner, effect of disease, and the interaction of scanner and disease for the 6 different scanners. The effect of disease in patients showed the expected significant reduction of grey matter in the medial temporal lobe. Scanner differences were substantially less than the group differences and only significant in the thalamus. There was no significant interaction of scanner with disease group. We describe the rationale for concluding that our results were not confounded by scanner differences. Similar analyses in other multi-scanner data-sets could be used to justify the pooling of data when needed, such as in studies of rare disorders or in multi-center designs. PMID:18032068

Stonnington, Cynthia M; Tan, Geoffrey; Klöppel, Stefan; Chu, Carlton; Draganski, Bogdan; Jack, Clifford R; Chen, Kewei; Ashburner, John; Frackowiak, Richard S J

2007-10-13

121

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

122

THE TESLA CRYO-PLANTS  

Microsoft Academic Search

The Tera-eV Energy Superconducting Linear Accelerator (TESLA) is a 32 km long superconducting linear electron\\/positron collider of 500 GeV centre of mass energy (upgradeable to 800 GeV), presently in the planning phase at DESY (1,2). About 21000 superconducting RF 9-cell cavities have to be cooled with superfluid helium at 2 K. The cavities are assembled in groups of 12 into

H. Quack; M. Kauschke; C. Haberstroh; Germany H. Lierl; B. Petersen; S. Wolff

2001-01-01

123

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

124

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

2012-09-11

125

Analyzing for information, not activation, to exploit high-resolution fMRI  

PubMed Central

High-resolution functional magnetic resonance imaging (hi-res fMRI) promises to help bridge the gap between the macro- and the microview of brain function afforded by conventional neuroimaging and invasive cell recording, respectively. Hi-res fMRI (voxel volume ? (2 mm)3) is robustly achievable in human studies today using widely available clinical 3-Tesla scanners. However, the neuroscientific exploitation of the greater spatial detail poses four challenges: (1) Hi-res fMRI may give inaccurate (i.e. blurred, displaced and distorted) images of fine-scale neuronal activity patterns. (2) Single small voxels yield very noisy measurements. (3) The greater number of voxels complicates interpretation and poses a more severe multiple-comparisons problem. (4) The functional correspondency mapping between individual brains is unknown at the fine scale of millimeters. Here we argue that these challenges can be met by shifting the focus of brain mapping and visualizing, not the activity patterns themselves, but the amount of information they convey about the experimental conditions.

Kriegeskorte, Nikolaus; Bandettini, Peter

2007-01-01

126

Diffusion-weighted imaging of the abdomen at 3.0 Tesla: image quality and apparent diffusion coefficient reproducibility compared with 1.5 Tesla  

Microsoft Academic Search

PURPOSE: To compare single-shot echo-planar imaging (SS EPI) diffusion-weighted MRI (DWI) of abdominal organs between 1.5 Tesla (T) and 3.0T in healthy volunteers in terms of image quality, apparent diffusion coefficient (ADC) values, and ADC reproducibility. MATERIALS AND METHODS: Eight healthy volunteers were prospectively imaged in this HIPAA-compliant IRB-approved study. Each subject underwent two consecutive scans at both 1.5 and

A. B. Rosenkrantz; M. T. H. Oei; J. S. Babb; B. E. Niver; B. Taouli

2011-01-01

127

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

128

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

129

51. View of upper radar scanner switch in radar scanner ...  

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

51. View of upper radar scanner switch in radar scanner building 105 from upper catwalk level showing emanating waveguides from upper switch (upper one-fourth of photograph) and emanating waveguides from lower radar scanner switch in vertical runs. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

130

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

131

Optimal performance for Tesla transformers  

NASA Astrophysics Data System (ADS)

The previous work related to finding improved performance for Tesla transformers is shortly reviewed. The possibilities to reach the optimal working point by modifying the main components are discussed from a practical standpoint. A methodology for maximizing the secondary voltage by regulating the tuning ratio T and the coupling coefficient is examined in particular. It is shown that its results are valid only if primary and secondary inductor values remain unchanged, and the secondary capacitor value is decreased. All in all, the best improvement from the typical condition of T=1 increases the secondary voltage of only 18% and requires tide coupling. This, in turn, imposes severe engineering problems to avoid dielectric breakdown between the primary and secondary coils, and makes the practical utility of this result someway questionable. In a real Tesla transformer, the most practical mean to perform tuning is to move the tap feeding the primary coil, rather than rewinding the secondary coil or redesigning the secondary top terminal. The resonant circuits are not undamped and it is crucial to reach the maximum voltage at the secondary in the shortest time, to minimize losses. It is shown that, in order to achieve optimal performance, a better strategy is to tune the primary coil to achieve T=1 and then to increase the coupling coefficient as much as possible, aiming at one of the values selected from a given table.

Denicolai, Marco

2002-09-01

132

Imaging of the Wrist at 1.5 Tesla Using Isotropic Three-Dimensional Fast Spin Echo Cube  

PubMed Central

Purpose To compare three-dimensional fast spin echo Cube (3D-FSE-Cube) with conventional 2D-FSE in MR imaging of the wrist. Materials and Methods The wrists of 10 volunteers were imaged in a 1.5 Tesla MRI scanner using an eight-channel wrist coil. The 3D-FSE-Cube images were acquired in the coronal plane with 0.5-mm isotropic resolution. The 2D-FSE images were acquired in both coronal and axial planes for comparison. An ROI was placed in fluid, cartilage, and muscle for SNR analysis. Comparable coronal and axial images were selected for each sequence, and paired images were randomized and graded for blurring, artifact, anatomic details, and overall image quality by three blinded musculoskeletal radiologists. Results SNR of fluid, cartilage and muscle at prescribed locations were higher using 3D-FSE-Cube, without reaching statistical significance. Fluid–cartilage CNR was also higher with 3D-FSE-Cube, but not statistically significant. Blurring, artifact, anatomic details, and overall image quality were significantly better on coronal 3D-FSE-Cube images (P < 0.001), but significantly better on axial 2D-FSE images compared with axial 3D-FSE-Cube reformats (P < 0.01). Conclusion Isotropic data from 3D-FSE-Cube allows reformations in arbitrary scan planes, which may make multiple 2D acquisitions unnecessary, and improve depiction of complex wrist anatomy. However, axial reformations suffer from blurring, likely due to T2 decay during the long echo train, limiting overall image quality in this plane.

Stevens, Kathryn J.; Wallace, Charles G.; Chen, Weitian; Rosenberg, Jarrett K.; Gold, Garry E.

2012-01-01

133

Feasibility of Using Ultra-High Field (7 T) MRI for Clinical Surgical Targeting  

PubMed Central

The advantages of ultra-high magnetic field (7 Tesla) MRI for basic science research and neuroscience applications have proven invaluable. Structural and functional MR images of the human brain acquired at 7 T exhibit rich information content with potential utility for clinical applications. However, (1) substantial increases in susceptibility artifacts, and (2) geometrical distortions at 7 T would be detrimental for stereotactic surgeries such as deep brain stimulation (DBS), which typically use 1.5 T images for surgical planning. Here, we explore whether these issues can be addressed, making feasible the use of 7 T MRI to guide surgical planning. Twelve patients with Parkinson's disease, candidates for DBS, were scanned on a standard clinical 1.5 T MRI and a 7 T MRI scanner. Qualitative and quantitative assessments of global and regional distortion were evaluated based on anatomical landmarks and transformation matrix values. Our analyses show that distances between identical landmarks on 1.5 T vs. 7 T, in the mid-brain region, were less than one voxel, indicating a successful co-registration between the 1.5 T and 7 T images under these specific imaging parameter sets. On regional analysis, the central part of the brain showed minimal distortion, while inferior and frontal areas exhibited larger distortion due to proximity to air-filled cavities. We conclude that 7 T MR images of the central brain regions have comparable distortions to that observed on a 1.5 T MRI, and that clinical applications targeting structures such as the STN, are feasible with information-rich 7 T imaging.

Duchin, Yuval; Abosch, Aviva; Yacoub, Essa; Sapiro, Guillermo; Harel, Noam

2012-01-01

134

Dynamic B0 shimming at 7 Tesla  

PubMed Central

Dynamic slicewise shimming improves B0 field homogeneity by updating shim coil currents for every slice in a multi-slice acquisition, producing better field homogeneity over a volume than can be obtained by a single static global shim. The first aim of this work was to evaluate the performance of slice-wise field map based 2nd order dynamic shimming in a human high field 7 Tesla clinical scanner vis-à-vis image based 2nd order static global shimming. Another goal was to characterize eddy currents induced by 2nd and 3rd order shim switching. A final aim was to compare global and dynamic shimming through shim orders to elucidate the relative benefits of going to higher orders and to dynamic shim updating from a static shimming regime. An external hardware module was used to store and dynamically update slice-optimized shim values during multislice data acquisition. High bandwidth multislice gradient echo scans with B0 field mapping and low bandwidth single shot echo planar scans were performed on phantoms and humans using 2nd order dynamic and static global shims. For the measurement of 2nd and 3rd order shim induced eddy currents, step response temporal phase changes of individual shims were measured and fit to shim harmonics spatially and to multiexponential decay functions temporally. Finally, an order wise fieldmap based comparison was performed with 1st, 2nd and 3rd order global static shimming, 1st and 2nd order dynamic shimming, as well as combined 2nd or 3rd order global and 1st order dynamic shim. Dynamic shimming considerably improved B0 homogeneity compared to static global shimming, both in phantoms and in human subjects, reducing image distortion and signal drop-out. The unshielded 2nd and 3rd order shims generated strong B0, self- and cross-term eddy fields with multiple time constants ranging from milliseconds to seconds. Field homogeneity improved with increasing order of shim, with dynamic shimming performing better than global shimming. Hybrid global and dynamic shimming approach yielded field homogeneity better than global static shims but worse than dynamic shims.

Sengupta, Saikat; Welch, E. Brian; Zhao, Yansong; Foxall, David; Starewicz, Piotr; Anderson, Adam W.; Gore, John C.; Avison, Malcolm J.

2011-01-01

135

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

136

Blood Flow MRI of the Human Retina/Choroid during Rest and Isometric Exercise  

PubMed Central

Purpose. To investigate blood flow (BF) in the human retina/choroid during rest and handgrip isometric exercise using magnetic resonance imaging (MRI). Methods. Four healthy volunteers (25–36 years old) in multiple sessions (1–3) on different days. MRI studies were performed on a 3-Tesla scanner using a custom-made surface coil (7 × 5cm in diameter) at the spatial resolution of 0.5 × 0.8 × 6.0 mm. BF was measured using the pseudo-continuous arterial-spin-labeling technique with background suppression and turbo-spin-echo acquisition. During MRI, subjects rested for 1 minute followed by 1 minute of handgrip, repeating three times, while maintaining stable eye fixation on a target with cued eye blinks at the end of each data acquisition (every 4.6 seconds). Results. Robust BF of the unanesthetized human retina/choroid was detected. Basal BF in the posterior retina/choroid was 149 ± 48 mL/100 mL/min with a mean heart rate of 60 ± 5 beats per minute, mean arterial pressure of 78 ± 5 mm Hg, ocular perfusion pressure of 67 ± 4 mm Hg at rest (mean ± SD, n = 4 subjects). Handgrip significantly increased retina/choroid BF by 25% ± 7%, heart rate by 19% ± 8%, mean arterial pressure by 22% ± 5% (measured at the middle of the handgrip task), and ocular perfusion pressure by 25% ± 6% (averaged across the entire handgrip task) (P < 0.01), but did not change intraocular pressure, arterial oxygen saturation, end-tidal CO2, and respiration rate (P > 0.05). Conclusions. This study demonstrates a novel MRI application to image quantitative BF of the human retina/choroid during rest and isometric exercise. Retina/choroid BF increases during brief handgrip exercise, paralleling increases in mean arterial pressure. Handgrip exercise changes ocular perfusion pressure free of potential drug side effect and can be done in the MRI scanner. MRI offers quantitative BF with large field of view without depth limitation, potentially providing insights into retinal pathophysiology.

Zhang, Yi; Nateras, Oscar San Emeterio; Peng, Qi; Rosende, Carlos A.; Duong, Timothy Q.

2012-01-01

137

Detailed imaging of the normal anatomy and pathologic conditions of the cavernous region at 3 Tesla using a contrast-enhanced MR angiography  

Microsoft Academic Search

Introduction  The purpose of this study was to evaluate the potential of a high-resolution contrast-enhanced magnetic resonance angiography\\u000a (CE-MRA) at 3 Tesla for the delineation of the cavernous sinus (CS) anatomy both under normal and under pathological conditions.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Fifteen patients without pathologies in the CS and ten patients with pituitary adenomas were included. The CE-MRA was performed\\u000a on a 3-Tesla scanner

Jennifer Linn; Friederike Peters; Nina Lummel; Christoph Schankin; Walter Rachinger; Hartmut Brueckmann; Indra Yousry

138

Comparison of Pelvic Phased-Array versus Endorectal Coil Magnetic Resonance Imaging at 3 Tesla for Local Staging of Prostate Cancer  

PubMed Central

Purpose Several studies have demonstrated the superiority of endorectal coil magnetic resonance imaging (MRI) over pelvic phased-array coil MRI at 1.5 Tesla for local staging of prostate cancer. However, few have studied which evaluation is more accurate at 3 Tesla MRI. In this study, we compared the accuracy of local staging of prostate cancer using pelvic phased-array coil or endorectal coil MRI at 3 Tesla. Materials and Methods Between January 2005 and May 2010, 151 patients underwent radical prostatectomy. All patients were evaluated with either pelvic phased-array coil or endorectal coil prostate MRI prior to surgery (63 endorectal coils and 88 pelvic phased-array coils). Tumor stage based on MRI was compared with pathologic stage. We calculated the specificity, sensitivity and accuracy of each group in the evaluation of extracapsular extension and seminal vesicle invasion. Results Both endorectal coil and pelvic phased-array coil MRI achieved high specificity, low sensitivity and moderate accuracy for the detection of extracapsular extension and seminal vesicle invasion. There were statistically no differences in specificity, sensitivity and accuracy between the two groups. Conclusion Overall staging accuracy, sensitivity and specificity were not significantly different between endorectal coil and pelvic phased-array coil MRI.

Kim, Bum Soo; Kim, Tae-Hwan; Kwon, Tae Gyun

2012-01-01

139

TESLA: Large Signal Simulation Code for Klystrons  

NASA Astrophysics Data System (ADS)

TESLA (Telegraphist's Equations Solution for Linear Beam Amplifiers) is a new code designed to simulate linear beam vacuum electronic devices with cavities, such as klystrons, extended interaction klystrons, twistrons, and coupled cavity amplifiers. The model includes a self-consistent, nonlinear solution of the three-dimensional electron equations of motion and the solution of time-dependent field equations. The model differs from the conventional Particle in Cell approach in that the field spectrum is assumed to consist of a carrier frequency and its harmonics with slowly varying envelopes. Also, fields in the external cavities are modeled with circuit like equations and couple to fields in the beam region through boundary conditions on the beam tunnel wall. The model in TESLA is an extension of the model used in gyrotron code MAGY. The TESLA formulation has been extended to be capable to treat the multiple beam case, in which each beam is transported inside its own tunnel. The beams interact with each other as they pass through the gaps in their common cavities. The interaction is treated by modification of the boundary conditions on the wall of each tunnel to include the effect of adjacent beams as well as the fields excited in each cavity. The extended version of TESLA for the multiple beam case, TESLA-MB, has been developed for single processor machines, and can run on UNIX machines and on PC computers with a large memory (above 2GB). The TESLA-MB algorithm is currently being modified to simulate multiple beam klystrons on multiprocessor machines using the MPI (Message Passing Interface) environment. The code TESLA has been verified by comparison with MAGIC for single and multiple beam cases. The TESLA code and the MAGIC code predict the same power within 1% for a simple two cavity klystron design while the computational time for TESLA is orders of magnitude less than for MAGIC 2D. In addition, recently TESLA was used to model the L-6048 klystron, code predictions agree with measured data in saturated output power very well, while there is difference in gain, the predicted gain is slightly higher than measured. These discrepancies will be explored in future simulations on better-diagnosed devices.

Vlasov, Alexander N.; Antonsen, Thomas M.; Cooke, Simon J.; Nguyen, Khanh T.; Chernin, David P.; Levush, Baruch

2003-12-01

140

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

141

Usefulness assessment of preoperative MRI fistulography in patients with perianal fistulas  

PubMed Central

Summary Background: Accurate preoperative assessment of the perianal fistulous tract is the main purpose of the diagnostics and to a large extend determines surgery effectiveness. One of the useful diagnostic methods in perianal fistulas is magnetic resonance imaging. The authors presented experiences in the application of MRI fistulography for evaluation of cases of perianal fistulas difficult to diagnose and treat. Material/Methods: Own examination method was described; MRI fistulography findings were analyzed and compared with intraoperative conditions in 14 patients (11 men and 3 women) diagnosed in the years 2005– 2009. Eight patients had recurrent fistulas and 6 had primary fistulas. Imaging was performed with a GE SIGNA LX HS scanner with a 1.5-Tesla field strength and a dedicated surface coil placed at the level of hip joints. Contrast agent was a gadolinium-based solution. Results: Intraoperative findings were consistent with radiological descriptions of 13 MRI fistulographies. Only in one case, according to surgery findings, it was a transsphincteric fistula with an abscess in the ischioanal fossa, with an orifice in the posterior crypt; the radiologist described it as a transsphincteric, internal blind fistula. Conclusions: Due to its accuracy in the assessment of the perianal fistulous tracts in soft tissues, MRI fistulography becomes a useful and recommended diagnostic method in this pathology. It shows the location of the fistula regarding the system of anal sphincters, and identifies the internal orifice and branching of the fistula. It enables precise planning of surgical treatment. Authors suggest that this diagnostic method should be improved and applied more commonly.

Waniczek, Dariusz; Adamczyk, Tomasz; Arendt, Jerzy; Kluczewska, Ewa; Kozinska-Marek, Ewa

2011-01-01

142

Microfabrication of fiber optic scanners  

Microsoft Academic Search

A cantilevered optical fiber is micromachined to function as a miniature resonant opto-mechanical scanner. By driving the base of the cantilevered fiber at a resonance frequency using a piezoelectric actuator, the free end of the cantilever beam becomes a scanned light source. The fiber scanners are designed to achieve wide field-of-view (FOV) and high scan frequency. We employ a non-linearly

Mark Fauver; Janet L. Crossman-Bosworth; Eric J. Seibel

2002-01-01

143

In Vivo Real-Time Intravascular MRI  

Microsoft Academic Search

Purpose. The Magnetic resonance imaging (MRI) is an emerging technology for catheter-based imaging and interventions. Real-time MRI is a promising method for overcoming catheter and physiologic motion for intravascular imaging. Methods. All imaging was performed on a 1.5 T Signa MRI scanner with high- speed gradients. Multiple catheter coils were designed and constructed, including low-profile, stub-matched coils. Coil sensitivity patterns

Pedro A. Rivas; Krishna S. Nayak; Greig C. Scott; Michael V. McConnell; Adam B. Kerr; Dwight G. Nishimura; John M. Pauly; Bob S. Hu

2002-01-01

144

PS3-35: MRI Detection of Substantia Nigra Degeneration in Parkinson's Disease: Developing a Candidate Biomarker.  

PubMed

Background/Aims The substantia nigra (SN) selectively degenerates in Parkinson's disease (PD). Prior MRI studies of SN have used manual segmentation to make quantitative measurements, an approach with inherently limited accuracy. Here we used an in-house optimized neuromelanin MRI (NM-MRI) protocol, and a novel semi-automated segmentation method to investigate changes in SN associated with PD. The relationship between MRI measures and orthostatic hypotension, a phenotypic feature of PD, was also examined. Methods Eight controls and 10 PD patients were scanned on a 3.0 Tesla Siemens MRI scanner using our optimized NM-MRI sequence (2D gradient echo sequence with magnetization transfer contrast preparation pulse) and processing protocol. A contrast to noise ratio (CNR) binary map was generated, identifying voxels with intensity >3 SD above the mean intensity. SN ROIs were defined on the binary map based on the location of the high intensity voxels, which defined its borders discretely. Mean CNR and number of voxels (volume) were then obtained for the SN. Statistical analysis was performed with SPSS. Results Comparison of means revealed that both CNR and volume of the SN were significantly lower in the PD group than in controls (CNR: P = 0.044; volume: P = 0.028). Each of the two MRI measures were significantly correlated with the orthostatic blood pressure drop (Pearson's correlation, CNR: r = -0.725, P = 0.001; volume: r = -0.661, P = 0.003). Conclusions As hypothesized, both CNR and volume of SN were significantly lower in the PD group than in controls. Since SN degenerates in PD, this NM-MRI approach appears to detect PD-associated degeneration of SN in vivo. Also as hypothesized, the MRI measures had a significant negative association with orthostatic blood pressure drop, a phenotypic characteristic of PD. These results indicate that the MRI measures presented here represent promising candidate PD biomarkers. Longitudinal studies are warranted to test this approach as part of an early diagnosis strategy and as a potential clinical trial outcome measure. PMID:24085914

Huddleston, Daniel; Chen, Xiangchuan; Langley, Jason; Hu, Xiaoping

2013-09-01

145

TEST AND CALIBRATION PROCEDURES FOR IMAGE SCANNERS  

Microsoft Academic Search

The aim of this paper is to present general, possibly device independent, testing procedures for high precision, high resolution scanning. The tests refer mostly to flatbed scanners employing linear or area CCDs. Thus, they are applicable to photogrammetric scanners and flatbed DTP scanners. For drum scanners similar tests and test patterns on stable Estar thick base film could be used.

Emmanuel P. Baltsavias

1994-01-01

146

Identification of EEG Events in the MR Scanner: The Problem of Pulse Artifact and a Method for Its Subtraction  

Microsoft Academic Search

Triggering functional MRI (fMRI) image acquisition immediately after an EEG event can provide information on the location of the event generator. However, EEG artifact associated with pulsatile blood flow in a subject inside the scanner may obscure EEG events. This pulse artifact (PA) has been widely recognized as a significant problem, although its characteristics are unpredictable. We have investigated the

Philip J. Allen; Giovanni Polizzi; Karsten Krakow; David R. Fish; Louis Lemieux

1998-01-01

147

Pulmonary MR angiography with contrast agent at 4 Tesla: a preliminary result.  

PubMed

In this study, pulmonary MR angiography (MRA) using a tailored coil at 4 Tesla in conjunction with an intravenous injection of contrast agent is described. Three-dimensional gradient-echo images were obtained during the intravenous injection of 0.05, 0.1, and 0.2 mmol/kg body weight of gadodiamide to investigate the signal enhancement effect of the contrast agent in pulmonary arteries qualitatively and quantitatively. In the qualitative analysis, the subsegmental branches were visualized on every dose. In the quantitative analysis, the average contrast-to-noise ratios (CNRs) of the main pulmonary arteries increased in a dose-dependent manner. However, the CNRs of segmental arteries did not increase as the dose of contrast agent increased, as observed at 1.5 Tesla MRI. These observations demonstrate the feasibility of delineating the pulmonary vasculature using a contrast agent; however, our results also suggest possible high-field-related disabilities that need to be overcome before high-field (> or =4 Tesla) MRI can be used to full advantage. PMID:11675658

Uematsu, H; Dougherty, L; Takahashi, M; Ohno, Y; Nakatsu, M; Song, H K; Ferrari, V A; Gefter, W B; Schnall, M D; Hatabu, H

2001-11-01

148

THE TESLA FREE ELECTRON LASER - CONCEPT AND STATUS  

Microsoft Academic Search

The aim of the TESLA Free Electron Laser (FEL) is to develop and realize an Angstrom wavelength, high gain FEL in parallel with the TESLA superconducting e+\\/e- linear collider. As a first step, an FEL for the VUV wavelength regime is now under construction at DESY, making use of the TESLA Test Facility (TTF). The VUV FEL at the TTF

J. Rossbach

1998-01-01

149

[Investigation of radio frequency heating of dental implants made of titanium in 1.5 tesla and 3.0 tesla magnetic resonance procedure: measurement of the temperature by using tissue-equivalent phantom].  

PubMed

Titanium (Ti) implants are increasingly being used for dental parts. There is no problem with the attraction of a static magnetic field for Ti in magnetic resonance imaging (MRI), since Ti is paramagnetic. However, there is a risk of radio frequency (RF) heat generation within Ti. 3.0 T-MRI scanners are becoming increasingly common. The specific absorption rate (SAR) of 3.0 T-MRI is quadruple that of SAR compared with 1.5 T-MRI due to its being proportional to the square of the strength of a static magnetic field. The effect of heat generation in 3.0 T-MRI can thus be greater than in 1.5 T-MRI. So, using 1.5 T and 3.0 T-MRI scanners, we measured the temperature of several Ti implants using the same scanning parameters during MRI scanning. Our measurements showed the rise in temperature of the Ti implants to be a maximum of 0.4 degrees C. In this study, however, Ti in a human mouth was not directly measured, so we need to attempt to perform MRI carefully on patients with Ti implants. PMID:23964532

Ideta, Takahiro; Yamazaki, Masaru; Kudou, Sadahiro; Higashida, Mitsuji; Mori, Shintarou; Kaneda, Takashi; Nakazawa, Masami

2013-05-01

150

A 1MV Magnetically Insulated Tesla Transformer  

Microsoft Academic Search

This paper describes the successful development of a 1-MV magnetically insulated Tesla transformer. Full details of the construction are provided, together with the basis of the design procedure. Preliminary results for the prototype transformer are presented and discussed, and future paper is outlined.

M. Istenic; Bucur M. Novac; Jing Luo; Rajesh Kumar; Ivor R. Smith

2008-01-01

151

Thirteen Tesla magnet constructed with MJR wire  

SciTech Connect

The authors have constructed an insert booster superconducting magnet of 20 mm clear bore and outside diameter of 100 mm and height 130 mm, wound and reacted from the Teledyne patented foraminous layered foil (jelly roll) wire fabricated by low cost, non-rebundled reduction to wire. This magnet was placed inside the 101 mm bore of a NbTi wound solenoid which was operated at 8.5 Tesla. The total field achieved was 13.0 Tesla with no training quench observed; although training was initially observed when the magnet was first tested alone up to 4.6 Tesla at American Magnets, Inc. (AMI). The magnet winding techniques utilize Airco's fiberglass type wire insulation, an AMI proprietary cement, argon atmosphere 700/sup 0/C for 100 hour reaction, followed by a postreaction potting impregnation. The MJR wire lot used (M22) was short sample tested and the Ln (J /SUB c/ ) -vs-H line intersected the insert magnet operating curve at 13.5 Tesla. The wire lot used has a 34 volume % copper external sheath for quench protection. The wire was fabricated with 15.4 volume % niobium and bronze/niobium ratio of 3.0 with 13.% Sn bronze.

Siddall, M.; Efferson, K.; Mcdonald, W.

1983-05-01

152

Status of the TESLA Test Facility Linac  

Microsoft Academic Search

The TTF linac, a major effort of the TESLA Test Facility, is now in the installation phase. The components have been built by an international collaboration and are presently set up at DESY\\/Hamburg. A first injector has been installed and tested since the beginning of the year and can provide 8 mA beam current within 800 µs long macro pulses

H. Weise

153

Capability of Identifying Red Nuclei in Different Pulse Sequences of Regular 1.5Tesla Magnetic Resonance Images  

Microsoft Academic Search

Objective: To investigate the optimal pulse sequences of commonly used 1.5-tesla MRI for identifying the red nucleus (RN) to aid targeting of the subthalamic nucleus (STN). Methods: Forty-six healthy adults were enrolled for this prospective study. All subjects underwent MR studies of 5 sequences: diffusion-weighted imaging (DWI), T1-weighted fluid-attenuated inversion recovery (T1IR), fast spin echo T2-weighted imaging (FSE-T2WI), T2-weighted fluid-attenuated

Shang-Ming Chiou; Yu-Chien Lo; Hung-Lin Lin

2012-01-01

154

Miniaturized micro-optical scanners  

Microsoft Academic Search

Optical beam scanners are critical components for airborne and space-based laser radar, on- machine-inspection systems, factory automation systems, and optical communication systems. We describe here a laser beam steering system based on dithering two complementary (positive and negative) microlens arrays. When the two microlens arrays are translated relative to one another in the plane parallel to their surfaces, the transmitted

M. Edward Motamedi; Angus P. Andrews; William J. Gunning; Moshen Khoshnevisan

1994-01-01

155

Design considerations for PET scanners.  

PubMed

In 2-D PET scanners employing septa, scattered radiation is reduced by the septa, placing less importance on good energy resolution. Additionally, the reduced sensitivity in 2-D limits the maximum countrates encountered in clinical FDG studies. In contrast, 3-D PET scanners rely on good energy resolution to reduce the scattered radiation and also must deal with countrates, which are typically 5 times higher than in 2-D mode. To achieve good energy resolution, 3 factors must be considered: 1) choice of a scintillator with good intrinsic energy resolution, 2) choice of a crystal dimension which transmits a uniform amount of light to the PMT in order to avoid light loss along the length of the crystal and 3) choice of a crystal-to-PMT coupling which collects a uniform amount of light from all crystals. As PET scanners are being designed using new, faster scintillators for 3-D imaging, the appropriate trade-off between energy resolution and countrate capability must be found to give the best overall system performance. An example of a fully 3-D PET scanner is the Allegro (ADAC Laboratories), which uses GSO as the detector material. Given the right choice of material and design parameters, good quality, high contrast images can be obtained in 3-D in a relatively short time. PMID:12072842

Muehllrhner, G; Karp, J S; Surti, S

2002-03-01

156

Coronary Artery Flow Measurement Using Navigator Echo Gated Phase Contrast Magnetic Resonance Velocity Mapping at 3.0 Tesla  

PubMed Central

A validation study and early results for noninvasive, in vivo measurement of coronary artery blood flow using phase contrast magnetic resonance imaging (PC-MRI) at 3.0 Tesla is presented. Accuracy of coronary artery blood flow measurements by phase contrast MRI is limited by heart and respiratory motion as well as the small size of the coronary arteries. In this study, a navigator-echo gated, cine phase velocity mapping technique is described to obtain time-resolved velocity and flow waveforms of small diameter vessels at 3.0 Tesla. Phantom experiments using steady, laminar flow are presented to validate the technique and show flow rates measured by 3.0 Tesla phase contrast MRI to be accurate within 15% of true flow rates. Subsequently, in vivo scans on healthy volunteers yield velocity measurements for blood flow in the right, left anterior descending, and left circumflex arteries. Measurements of average, cross-sectional velocity were obtainable in 224/243 (92%) of the cardiac phases. Time-averaged, cross-sectional velocity of the blood flow was 6.8±4.3 cm/s in the LAD, 8.0±3.8 cm/s in the LCX, and 6.0±1.6 cm/s in the RCA.

Johnson, Kevin; Sharma, Puneet; Oshinski, John

2009-01-01

157

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

158

Minimally Invasive Magnetic Resonance Imaging-Guided FreeHand Aspiration of Symptomatic Nerve Route Compressing Lumbosacral Cysts Using a 1.0Tesla Open Magnetic Resonance Imaging System  

Microsoft Academic Search

Purpose  To evaluate the feasibility of minimally invasive magnetic resonance imaging (MRI)-guided free-hand aspiration of symptomatic\\u000a nerve route compressing lumbosacral cysts in a 1.0-Tesla (T) open MRI system using a tailored interactive sequence.\\u000a \\u000a \\u000a \\u000a \\u000a Materials and Methods  Eleven patients with MRI-evident symptomatic cysts in the lumbosacral region and possible nerve route compressing character\\u000a were referred to a 1.0-T open MRI system. For MRI

Maximilian de Bucourt; Florian Streitparth; Federico Collettini; Felix Guettler; Hendrik Rathke; Britta Lorenz; Jens Rump; Bernd Hamm; U. K. Teichgräber

159

Macroscopic static field inhomogeneity in the human brain during MRI examination  

NASA Astrophysics Data System (ADS)

The macroscopic static field inhomogeneity is not only the source of MR signal loss in gradient echo based imaging techniques, but also the source of geometrical image distortion as well as a limitation of spectral resolution. This piece of information is useful for both active shimming coil design and clinical imaging application. In order to further understand the spatial variation of the macroscopic background static field in human brain during MRI examination, this static field inhomogeneity was measured from the adult human volunteers with a volumetric imaging scheme, which was based on a 3D gradient echo technique with two consecutive gradient echoes. All the human volunteers were scanned in supine position using a birdcage headcoil on a 1.5 T clinical whole body scanner. We have constructed a high resolution 3D static field map over the brain volume. All experimental results have shown consistently that there are mainly two spots in the brain tissue volume exhibiting relatively severe static magnetic field inhomogeneity . They are normally located in the brain areas in the inferior frontal lobe immediately anterior to the nasal cavity and in the inferior temporal lobe above the ear canals, where air spaces exist in the vicinity. At those locations, the observed offset frequency in the proton resonance reached about 50 Hz over 5 mm distance along the z direction at 1.5 Tesla, corresponding to 1.5 ppm/cm locally.

Liu, Haiying; Michel, Edward; Casey, Sean O.; Hall, Walter A.; Truwit, Charles L.

2002-05-01

160

Nano-scanner for scanning probe microscopes  

NASA Astrophysics Data System (ADS)

A two-axes nano-scanner for a scanning probe microscope (SPMs) was developed. The flexure-guided nano-scanner can move SPM samples or the probe itself along the x and y axes. The theoretical stiffness and resonant frequency of the flexure guide were obtained by using Castigliano's theorem. An optimal nano-scanner that maximize the scanning speed under appropriate constraints was designed. The optimal results were compared with the results of a finite element analysis. The scanner performance was evaluated by using various experiments and was compared with the optimal design results. Finally, atomic force microscope images obtained by using the proposed nano-scanner are presented.

Park, Jae Hong; Lee, Dong-Yeon

2012-11-01

161

Large-area aircraft scanner  

NASA Astrophysics Data System (ADS)

A program to determine the feasibility of present state-of-the-art NDI technology to produce a large-area scanner and to identify commercial equipment available to construct the desired system is presented. Work performed to attain these objectives is described, along with suggested modifications to the existing commercial equipment in order to meet the design criteria as closely as possible. Techniques that show the most promise at present are: D-sight, shearography, and pulse IR thermography (PIRT). D-sight is argued to be inadequate alone, but may well help form a system in conjunction with another technique. Shearography requires additional development in the area of stress application along with interpretation and overall application. PIRT is argued to be satisfactory as a large-area scanner system, at least for thin composite and metal panels.

Iddings, Frank A.

162

Stereotactic Accuracy of a Compact Intraoperative MRI System  

Microsoft Academic Search

Objective: To analyze the stereotactic accuracy of the PoleStar N-20, a compact intraoperative magnetic resonance imaging (iMRI) system, based on a 0.15-Tesla (T) magnet. Methods: An MRI-compatible phantom was scanned after being positioned in both the center of the magnetic field (COF) and the periphery of the field (POF) of the PoleStar N-20 magnet. Scans were acquired at various slice

Sussan Salas; Michael Brimacombe; Michael Schulder

2007-01-01

163

The Conceptual Design of a 20 Tesla Pulsed Solenoid for a Laser Solenoid Fusion Reactor  

Microsoft Academic Search

Design considerations are described for a strip wound solenoid which is pulsed to 20 tesla while immersed in a 20 tesla bias field so as to achieve within the bore of the pulsed solenoid a net field sequence starting at 20 tesla and going first down to zero, then up to 40 tesla, and finally back to 20 tesla in

J. J. Nolan; R. J. Averill

1977-01-01

164

Microfabrication of fiber optic scanners  

NASA Astrophysics Data System (ADS)

A cantilevered optical fiber is micromachined to function as a miniature resonant opto-mechanical scanner. By driving the base of the cantilevered fiber at a resonance frequency using a piezoelectric actuator, the free end of the cantilever beam becomes a scanned light source. The fiber scanners are designed to achieve wide field-of-view (FOV) and high scan frequency. We employ a non-linearly tapered profile fiber to achieve scan amplitudes of 1 mm at scan frequencies above 20 KHz. Scan angles of over 120 degree(s) (full angle) have been achieved. Higher order modes are also employed for scanning applications that require compactness while maintaining large angular FOV. Etching techniques are used to create the non-linearly tapered sections in single mode optical fiber. Additionally, micro-lenses are fabricated on the tips of the etched fibers, with lens diameters as small as 15 microns. Such lenses are capable of reducing the divergence angle of the emitted light to 5 degree(s) (full angle), with greater reduction expected by employing novel lens shaping techniques. Microfabricated optical fiber scanners have display applications ranging from micro-optical displays to larger panoramic displays. Applications for micro-image acquisition include small barcode readers to medical endoscopes.

Fauver, Mark; Crossman-Bosworth, Janet L.; Seibel, Eric J.

2002-06-01

165

A physical Shepp-Logan head phantom for MRI  

Microsoft Academic Search

A head phantom which is compatible with magnetic resonance imaging (MRI) has been constructed from layers of polycarbonate. When imaged using the appropriate scanner parameters, the partial volume eect generates contrast values for each region which approximate to those of the well known Shepp- Logan computational phantom. MRI data measured from the physical phantom can be used to validate simulations

P. J. Bones; J. R. Maclaren

2007-01-01

166

TESLA Test Facility:status and results  

Microsoft Academic Search

The TESLA Test Facility (TTF), under construction at DESY by an international collaboration, is an R&D test bed for the superconducting option for future linear e+\\/e- colliders. It consists of an infrastructure to process and test the cavities and of a 500 MeV linac. The infrastructure has been installed and is fully operational. It includes a complex of clean rooms,

B. Aune

1996-01-01

167

TESLA: simulation code for multiple beam klystrons  

Microsoft Academic Search

TESLA (Telegraphist's Equations Solution Linear beam Amplifiers) is a new code designed to simulate linear beam vacuum electronic devices with cavities, such as klystrons, interaction klystrons, twistrons, and coupled cavity amplifiers. The model includes a self-consistent, nonlinear solution of the three-dimensional electron equations of motion and the solution of time-dependent field equations. Also, fields in the external cavities are modeled

A. N. Vlasov; D. P. Chernin; S. J. Cooke; B. Levush; K. T. Nguyen

2003-01-01

168

Undulator system for the VUV FEL at the TESLA test facility phase-2  

NASA Astrophysics Data System (ADS)

The Phase-1 of the VUV Free Electron Laser at the TESLA Test Facility finishes in fall 2002. Phase-2, an extension of Phase-1 towards shorter wavelengths is under construction and will be ready for operation in 2003. A radiation wavelength as low as 6nm will be obtained by raising the electron energy to 1GeV. There will be only minor changes to the undulator system. Compared to Phase-1, six instead of three undulator segments will be installed. The integrated focusing system will be replaced by an electromagnetic doublet structure. We report about the changes of the undulator, the undulator vacuum system, the separated quadrupoles including a stretched wire alignment systems and the modifications to the beam diagnostic system consisting of pick up monitors and wire scanners.

Pflüger, J.; Hahn, U.; Faatz, B.; Tischer, M.

2003-07-01

169

Absolute Temperature Monitoring Using RF Radiometry in the MRI Scanner  

Microsoft Academic Search

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

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

2006-01-01

170

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

171

3.0 Tesla imaging of the musculoskeletal system.  

PubMed

High-field MRI at 3.0T is rapidly gaining clinical acceptance and experiencing more widespread use. The superiority of high-field imaging has clearly been demonstrated for neurological imaging. The impact of 3.0T imaging of the musculoskeletal system has been less dramatic due to complex optimization issues. Areas under consideration include coil technology, protocol modification, artifact reduction, and patient safety. In this article we review these issues and describe our experience with 3.0T musculoskeletal MRI. Fundamentally, an increased signal-to-noise ratio (SNR) is responsible for improved imaging at higher field strength. Increased SNR allows more headroom to adjust parameters that affect image resolution and examination time. It has been established that T1 relaxation time increases at 3.0T, while T2 time decreases. Consequently, scanner parameters require adjustment for optimization of images. Chemical shift and magnetic susceptibility artifacts are more pronounced and require special techniques to minimize the effect on image quality. Spectral fat saturation techniques can take advantage of the increased chemical shift. The specific absorption rate (SAR) and acoustic noise thresholds must be kept in mind at these higher fields. We additionally present some of the clinical issues we have experienced at 3.0T. A decision must be made as to whether to trade higher resolution for reduced scanning time. In general, we believe that routine imaging at 3.0T increases diagnostic confidence, especially for evaluations of cartilaginous and ligamentous structures. PMID:17260407

Kuo, Raymond; Panchal, Mahendra; Tanenbaum, Larry; Crues, John V

2007-02-01

172

Simulation platform for self-assembly structures in MRI-guided nanorobotic drug delivery systems  

Microsoft Academic Search

Magnetic Resonance Imaging (MRI) guided nanorobotic systems that could perform diagnostic, curative and reconstructive treatments in the human body at the cellular and sub-cellular level in a controllable manner have recently been proposed. The concept of a MRI-guided nanorobotic system is based on the use of a MRI scanner to induce the required external driving forces to guide magnetic nanocapsules

Panagiotis Vartholomeos; Constantinos Mavroidis

2010-01-01

173

Magnetic Resonance Imaging (MRI) of the Kidney.  

National Technical Information Service (NTIS)

The thesis reflects experience with Magnetic Resonance Imaging (MRI) in the diagnosis of kidney disease. Initial results were obtained on a 0.15 T resistive and a 0.5 T superconducting prototype MR scanner (Philips, Best, the Netherlands). Further clinica...

L. Te Strake

1987-01-01

174

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

175

Systematic Evaluation of Hardware and Animal Stability for High-Resolution Layer-Specific MRI of the Retina  

Microsoft Academic Search

Purpose: To examine animal and hardware instability in phantoms and in vivo rat retinas, and to implement solu- tions to improve stability for structural and functional MRI of the retina. Materials and Methods: Anatomical (25 25 m) and perfusion-based functional (90 90 m) MRI protocols were evaluated on phantoms and in vivo rat retinas at 7 Tesla. Temporal phase drift

Timothy Q. Duong; Xiaodong Zhang; Yingxia Li

2009-01-01

176

Recent results from the TESLA Test Facility (TTF)  

Microsoft Academic Search

In this paper we present recent results of the TESLA Test Facility (TTF). The most important milestone was the operation with the TESLA design current, macropulses of 800 ?s with bunches of 4 nC at a rate of 2.25 MHz. Further studies include measurements of higher order modes (HOMs) in superconducting cavities, optimization of the TTF free electron laser at

M. Huning; RWTH Aachen

2001-01-01

177

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

178

Using Large Signal Code TESLA for Wide Band Klystron Simulations.  

National Technical Information Service (NTIS)

Large signal klystron simulation code TESLA has been developed to be suitable for simulations of wide band klystrons with two-gap two-mode resonators. The results of TESLA simulations for NRL S-bans MBK with extended bandwidth have been compared with pred...

A. N. Vlasov D. E. Pershing I. A. Chernyavskiy J. T. Antonsen K. T. Nguyen

2006-01-01

179

The globalization of Tesla Motors: a strategic marketing plan analysis  

Microsoft Academic Search

This case study provides analysis of the strategic marketing plan of electric vehicle manufacturer, Tesla Motors. It has profound marketing management implications, as it addresses this investigation from the unique perspective of Tesla's ‘new technology’-based approach to automobile marketing and relates it to the successful marketing model of Apple Computer. This marketing approach is counter to the traditional automobile industry's

Myles Edwin Mangram

2012-01-01

180

Neurodegenerative changes in Alzheimer's disease: a comparative study of manual, semi-automated, and fully automated assessment using MRI  

NASA Astrophysics Data System (ADS)

Objective quantification of disease specific neurodegenerative changes can facilitate diagnosis and therapeutic monitoring in several neuropsychiatric disorders. Reproducibility and easy-to-perform assessment are essential to ensure applicability in clinical environments. Aim of this comparative study is the evaluation of a fully automated approach that assesses atrophic changes in Alzheimer's disease (AD) and Mild Cognitive Impairment (MCI). 21 healthy volunteers (mean age 66.2), 21 patients with MCI (66.6), and 10 patients with AD (65.1) were enrolled. Subjects underwent extensive neuropsychological testing and MRI was conducted on a 1.5 Tesla clinical scanner. Atrophic changes were measured automatically by a series of image processing steps including state of the art brain mapping techniques. Results were compared with two reference approaches: a manual segmentation of the hippocampal formation and a semi-automated estimation of temporal horn volume, which is based upon interactive selection of two to six landmarks in the ventricular system. All approaches separated controls and AD patients significantly (10-5 < p < 10-4) and showed a slight but not significant increase of neurodegeneration for subjects with MCI compared to volunteers. The automated approach correlated significantly with the manual (r = -0.65, p < 10-6) and semi automated (r = -0.83, p < 10-13) measurements. It proved high accuracy and at the same time maximized observer independency, time reduction and thus usefulness for clinical routine.

Fritzsche, Klaus H.; Giesel, Frederik L.; Heimann, Tobias; Thomann, Philipp A.; Hahn, Horst K.; Pantel, Johannes; Schröder, Johannes; Essig, Marco; Meinzer, Hans-Peter

2008-04-01

181

Reduced striatal activation during reward anticipation due to appetite-provoking cues in chronic schizophrenia: a fMRI study.  

PubMed

The occurrence of weight gain in schizophrenia (SZ) has profound clinical impact and interacts with antipsychotic medication, life style and disease severity. The functional neuroanatomy underlying altered nutritional behavior is unraveled, but dysregulated reward anticipation might be one of the involved neuronal mechanisms. The striatum, a core region of the reward network and salience attribution, was previously shown to regulate appetite perception and eating behavior. We studied patients suffering from chronic schizophrenia with a stable medication in comparison to age and gender matched healthy adults. Every subject had to undergo a 6h fasting period before a newly developed, appetite-provoking fMRI task was applied. Subjects saw visual stimuli of appetitive food items in a 3Tesla scanner. In healthy controls food images elicited stronger activation in the striatum compared to SZ patients. When adjusting a ROI-based striatal activation for medication and weight, the group difference remained still significant. This points an effect of illness independent of antipsychotic medication. These data underscore the involvement of the striatum into salience attribution, reward anticipation and the neuronal pathways leading to altered eating behavior and weight gain in schizophrenia. PMID:22209236

Grimm, O; Vollstädt-Klein, S; Krebs, L; Zink, M; Smolka, M N

2011-12-29

182

Diffraction grating scanners using polysilicon micromotors  

Microsoft Academic Search

This paper describes polysilicon micromotors with diffraction gratings fabricated on the polished surface of the polysilicon rotor for optical scanning applications. Such micromotor optical scanners have high quality scan profiles, good efficiency, meter working distances, and multiple out of plane beam diffraction orders. Above all, the scanner design takes full advantage of planar processing. Chemical-mechanical polishing is used to reduce

A. A. Yasseen; S. W. Smith; M. Mehregany; F. L. Merat

1995-01-01

183

ID scanners in the night time economy  

Microsoft Academic Search

ID scanners are quickly emerging as a new technological fix to long-standing problems of security and safety within licensed venues. Yet at this point in time detailed research of this rapidly expanding security technology is remarkably limited. To address this analytical deficit we are currently examining the uptake of ID scanners in licensed venues operating in the nighttime economy. We

Darren Palmer; Ian Warren; Peter Miller

2010-01-01

184

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

185

Non-Destructive Testing Scanner  

NASA Astrophysics Data System (ADS)

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

186

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

187

21 CFR 892.1330 - Nuclear whole body scanner.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Nuclear whole body scanner. 892.1330 ...DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL...892.1330 Nuclear whole body scanner. (a) Identification. A nuclear whole body scanner is a device...

2013-04-01

188

21 CFR 882.1925 - Ultrasonic scanner calibration test block.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Ultrasonic scanner calibration test block. 882.1925 Section...882.1925 Ultrasonic scanner calibration test block. (a) Identification. An ultrasonic scanner calibration test block is a block of...

2013-04-01

189

Stereotactic Targeting of the Ventrointermediate Nucleus of the Thalamus by Direct Visualization with High-Field MRI  

Microsoft Academic Search

Objective: To evaluate the ability of high-field MRI to consistently produce high-resolution, anatomical images of the thalamic ventrointermediate nucleus (Vim) suitable for stereotactic targeting. Methods: MR images of the thalamus of patients treated for essential tremor were acquired prior to treatment using a 3-tesla MR system. Similar images were acquired in 6 volunteers using, for comparison, both a 1.5-tesla and

Roberto Spiegelmann; Ouzi Nissim; Diana Daniels; Aharon Ocherashvilli; Yael Mardor

2006-01-01

190

MRI Compatibility of Robot Actuation Techniques - A Comparative Study  

PubMed Central

This paper reports an experimental evaluation of the following three different MRI-compatible actuators: a Shinsei ultrasonic motor, a Nanomotion ultrasonic motor and a pneumatic cylinder actuator. We report the results of a study comparing the effect of these actuators on the signal to noise ratio (SNR) of MRI images under a variety of experimental conditions. Evaluation was performed with the controller inside and outside the scanner room and with both 1.5T and 3T MRI scanners. Pneumatic cylinders function with no loss of SNR with controller both inside and outside of the scanner room. The Nanomotion motor performs with moderate loss of SNR when moving during imaging. The Shinsei is unsuitable for motion during imaging. All may be used when motion is appropriately interleaved with imaging cycles.

Fischer, Gregory S.; Krieger, Axel; Iordachita, Iulian; Csoma, Csaba; Whitcomb, Louis L.; Fichtinger, Gabor

2010-01-01

191

"MRI Stealth" robot for prostate interventions  

PubMed Central

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.

STOIANOVICI, DAN; SONG, DANNY; PETRISOR, DORU; URSU, DANIEL; MAZILU, DUMITRU; MUTENER, MICHAEL; SCHAR, MICHAEL; PATRICIU, ALEXANDRU

2011-01-01

192

A novel optical scanner for laser radar  

NASA Astrophysics Data System (ADS)

Laser radar are ideally suitable for recognizing objects, detection, target tracking or obstacle avoidance, because of the high angular and range resolution. In recent years, scannerless ladar has developed rapidly. In contrast with traditional scanner ladar, scannerless ladar has distinct characteristics such as small, compact, high frame rate, wide field of view and high reliability. However, the scannerless ladar is still in the stage of laboratory and the performance cannot meet the demands of practical applications. Hence, traditional scanner laser radar is still mainly applied. In scanner ladar system, optical scanner is the key component which can deflect the direction of laser beam to the target. We investigated a novel scanner based on the characteristic of fiber's light-conductive. The fiber bundles are arranged in a special structure which connected to a motor. When motor working properly, the laser passes through the fibers on incident plane and the location of laser spot on output plane will move along with a straight line in a constant speed. The direction of light will be deflected by taking advantage of transmitting optics, then the linear sweeping of the target can be achieved. A laser radar scheme with high speed and large field of view can be realized. Some researches on scanner are simply introduced on section1. The structure of the optical scanner will be described and the practical applications of the scanner in transmitting and receiving optical paths are discussed in section2. Some characteristic of scanner is calculated in section3. In section4, we report the simulation and experiment of our prototype.

Yao, Shunyu; Peng, Renjun; Gao, Jianshuang

2013-09-01

193

[Investigation of radiofrequency heating for a closed conducting loop formed in a part of the patient's body in 1.5 Tesla magnetic resonance (MR) imaging and 3.0 Tesla MR imaging-measurement of temperature by use of human body-equivalent phantom].  

PubMed

Thermal injuries have been sometimes reported due to a closed conducting loop formed in a part of the patient's body during magnetic resonance imaging (MRI). In recent years, 3.0 T-MRI scanner has been widely used. However, it is considered that the specific absorption rate (SAR) of 3.0 T-MRI can affect the heat of the loop because its own SAR becomes approximately 4 times as much as that of the1.5 T-MRI scanner. With this, the change in temperature was measured with human body-equivalent loop phantom in both 1.5 T-MRI and 3.0 T-MRI. In the two scanners, the temperature during 20 min of scanning time was measured with three types of sequences such as field echo (FE), spin echo (SE), and turbo SE (TSE) set up with the same scanning condition. It was found from the result that rise in temperature depended on SAR of the scanning condition irrespective of static magnetic field intensity and any pulse sequences. Furthermore, the increase of SAR and rise in temperature were not only in proportion to each other but also were indicated to have good correlation. However, even low SAR can occasionally induce serious thermal injuries. It was found from result that we had to attempt not to form a closed conducting loop with in a part of the patient's body during MRI. PMID:23001271

Yamazaki, Masaru; Higashida, Mitsuji; Kudo, Sadahiro; Ideta, Takahiro; Nakazawa, Masami

2012-01-01

194

Pulsed Doppler lidar airborne scanner  

NASA Astrophysics Data System (ADS)

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.

1985-10-01

195

Comparative magnetic resonance imaging at 1.5 and 3 Tesla for the evaluation of traumatic microbleeds.  

PubMed

Traumatic microbleeds (TMBs) can be regarded as a radiological marker of diffuse axonal injury (DAI). We sought to investigate the impact of the field strengths on the depiction of TMBs by T2*-weighted gradient echo magnetic resonance imaging (MRI). By the use of comparative MRI of 14 patients (age range, 22-62 years) on 1.5- and a 3 T (Tesla) systems at a median time interval of 61 months after traumatic brain injury (TBI), we found 239 (range 0.5-48.5, median 7.5) TMBs at 1.5 T, and 470 (range 2-118, median 18.5) TMBs at 3 T, respectively (p=0.001). However, in all but one patients MRI at 1.5 T also clearly showed TMBs. A significant negative correlation between the number of TMBs and the time interval TBI-MRI was observed, which was weaker for the imaging at 3 T (r(s)=-0.798; p=0.001; and r(s)=-0.649; p=0.012, respectively). In conclusion, T2*-weighted gradient-echo MRI at 3 T is superior as compared to MRI at 1.5 T for the detection of TMBs. Nevertheless, in clinical practice, MRI at 1.5 T seems to be sufficient for this purpose. MRI at 3 T may be appropriate if there is a strong clinical suspicion of DAI, despite unremarkable routine MRI, and possibly also if evidence of DAI is sought after a long interval from trauma. PMID:18159992

Scheid, Rainer; Ott, Derek V; Roth, Henrik; Schroeter, Matthias L; von Cramon, D Yves

2007-12-01

196

Age-related changes in the somatosensory processing of tactile stimulation--an fMRI study.  

PubMed

Age-related changes in brain function are complex. Although ageing is associated with a reduction in cerebral blood flow and neuronal activity, task-related processing is often correlated with an enlargement of the corresponding and additionally recruited brain areas. This supplemental employment is considered an attempt to compensate for deficits in the ageing brain. Although there are contradictory reports regarding the role of the primary somatosensory cortex (SI), currently, there is little knowledge about age-related functional changes in other brain areas in the somatosensory network (secondary somatosensory cortex (SII), and insular, anterior (ACC) and posterior cingulate cortices (PCC)). We investigated 16 elderly (age range, 62-71 years) and 18 young subjects (age range, 21-28 years) by determining the current perception threshold (CPT) and applying functional magnetic resonance imaging (fMRI) using a 3.0 Tesla scanner under tactile stimulation of the right hand. CPT was positively correlated with age. fMRI analysis revealed significantly increased activation in the contralateral SI and ipsilateral motor cortex in elderly subjects. Furthermore, we demonstrated age-related reductions in the activity in the SII, ACC, PCC, and dorsal parts of the corpus callosum. Our study revealed dramatic age-related differences in the processing of a simple tactile stimulus in the somatosensory network. Specifically, we detected enhanced activation in the contralateral SI and ipsilateral motor cortex assumingly caused by deficient inhibition and decreased activation in later stages of somatosensory processing (SII, cingulate cortex) in elderly subjects. These results indicate that, in addition to over-activation to compensate for impaired brain functions, there are complex mechanisms of modified inhibition and excitability involved in somatosensory processing in the ageing brain. PMID:23123141

Brodoehl, Stefan; Klingner, Carsten; Stieglitz, Katharina; Witte, Otto W

2012-10-30

197

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

198

A modified protocol using half-dose gadolinium in dynamic 3-Tesla magnetic resonance imaging for detection of ACTH-secreting pituitary tumors.  

PubMed

ACTH-secreting tumors represent 10% of functioning pituitary adenomas, and most of them are microadenomas. It is generally accepted that only half of these tumors are correctly identified with current magnetic resonance imaging (MRI) techniques. The objective of the paper is to report a method for detecting suspected ACTH-secreting pituitary tumors undetectable by conventional dynamic MRI using dynamic 3-Tesla MRI (3T MRI) and half-dose gadopentetate dimeglumine (0.05 mmol/Kg). Eight patients were included (5 men and 3 women) with a mean age of 29.12 years. Each of them had a confirmed diagnosis of Cushing disease and a negative dynamic MRI for microadenoma using full-dose gadopentetate dimeglumine. A second MRI was then performed using only half the usual dose of contrast material. Images from the second MRI where compared with the first study. Microadenomas were detected in 100% of the patients using a half dose of the contrast. All were recognized on the basis of the presence of a hypointense nodular lesion surrounded by normal contrast-enhanced tissue. Six patients were submitted to surgery, and the results were confirmed by immunohistochemistry in all of them. The remaining subject had a sinus sample catheterization coincident with the MRI results. Conclusion: A half dose of dynamic resonance imaging contrast material increases the sensitivity of MRI detection of ACTH-secreting pituitary tumors. PMID:20182808

Portocarrero-Ortiz, Lesly; Bonifacio-Delgadillo, Dulce; Sotomayor-González, Arturo; Garcia-Marquez, Arturo; Lopez-Serna, Raul

2010-09-01

199

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

200

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

2012-08-25

201

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

202

Dobutamine stress cardiovascular magnetic resonance at 3 Tesla  

Microsoft Academic Search

PURPOSE: The assessment of inducible wall motion abnormalities during high-dose dobutamine-stress cardiovascular magnetic resonance (DCMR) is well established for the identification of myocardial ischemia at 1.5 Tesla. Its feasibility at higher field strengths has not been reported. The present study was performed to prospectively determine the feasibility and diagnostic accuracy of DCMR at 3 Tesla for depicting hemodynamically significant coronary

S Kelle; A Hamdan; B Schnackenburg; U Köhler; C Klein; E Nagel; E Fleck

2008-01-01

203

OPERATING EXPERIENCE WITH SUPERCONDUCTING CAVITIES AT THE TESLA TEST FACILITY  

Microsoft Academic Search

A description of the TESLA Test Facility (1), which has been set up at DESY by the T eV Energy Superconducting Accelerator (TESLA) (2) collaboration, will be given as it is now after five years of installation and operation. The experience with the first three modules, each containing 8 superconducting 9-cell cavities, installed and operated in the TTF-linac will be

Wolf-Dietrich Möller

204

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

205

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

206

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

207

The Cryogenics of a Thermosiphon-Cooled HTS MRI Magnet—Assembly and Component Testing  

Microsoft Academic Search

The team at GE Global Research presents cryo- assembly and component test results of a high-temperature super- conducting (HTS) limb size magnetic resonance imaging (MRI) scanner using Sumitomo's DI-BSCCO tape conductor, under an NIH research grant. The goal is to investigate the thermosiphon be- havior for different MRI operating modes, validating the cryogenic robustness of this cooling approach and its

W. Stautner; M. Xu; E. T. Laskaris; G. Conte; P. S. Thompson; C. van Epps; K. Amm

2011-01-01

208

[Mesial temporal sclerosis in temporal lobe epilepsy: quantitative magnetic resonance imaging assesment with 3.0 Tesla].  

PubMed

Recent studies show that up to 70% of patients with temporal lobe epilepsy (TLE) have a hippocampal deficit known as temporal mesial sclerosis (TME) characterized by neuron loss and gliosis, and considered the main epileptogenic focus among this type of patients. The magnetic resonance imaging (MRI) features of TME include atrophy and hippocampus hyperintensitY in the long TR sequences (Flair and T2). The 3.0 Tesla MRI allows the study of the brain's anatomy and physiology using different sequences and post processing mechanisms. Volumetry can determine the accurate volume and, together with spectroscopy, makes possible a quantitative assessment of the hyppocampus. Both techniques help to locate cerebral areas with epileptogenic activity. We describe the imaging findings from spectroscopy and volumetry in a patient with TLE and briefly review the related literature. PMID:18246939

Roldán-Valadez, Ernesto; Corona-Cedillo, Roberto; Cosme-Labarthe, Juan; Martínez-López, Manuel

209

Low field intraoperative MRI in glioma surgery.  

PubMed

The extent of resection marks one prognostic factor for patients with malignant gliomas. Among the methods used for the intraoperative control of the extent of resection, intraoperative magnetic resonance imaging (ioMRI) has become a very attractive method. It was introduced in the in the final decade of the last century. The first available system was a low magnetic field strength unit employing 0.5 Tesla (T). While currently high-field systems (1.5 T and above) are being developed, different low-field ioMRI systems (0.5 T and below) have been used for brain tumor resection in far more centers than high-field ioMRI, corresponding to a greater number of publications. Undoubtedly, high-field ioMRI systems offer superior image quality and faster acquisition times. Yet, low-field ioMRI has influenced intraoperative decision-making and improved brain tumor resection. With this article, we review the use of low-field ioMRI in glioma surgery. PMID:20960318

Seifert, Volker; Gasser, Thomas; Senft, Christian

2011-01-01

210

Portable MRI  

Microsoft Academic Search

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)

Espy; Michelle A

2012-01-01

211

Functional phantom for fMRI: a feasibility study.  

PubMed

Functional magnetic resonance imaging (fMRI) reveals changes in blood oxygen level-dependent (BOLD) signal after considerable processing. This paper describes the implementation and testing of an fMRI phantom where electric current applied to a thin wire within a proton-rich medium substituted BOLD distortion of the magnetic field; the scanner detects these two distortions as practically identical signal changes. The magnitude of the change depended on the current strength. The phantom has a number of possible applications. Signal changes across sessions, days, instruments and individuals could be monitored. Placing the phantom close to a subject during an fMRI experiment could allow differentiating sensitivity changes in the scanner due to instrumentation from changes in the subject's state and performance during the experiment. The spatial extent of brain activations and effects of various changes in the chain of image formation could be analyzed using current-induced "activations". Furthermore, the phantom could expedite fMRI sequence development by reducing the need to scan human subjects, who introduce uncertainty to the signal. Thus, this fMRI phantom could be useful for both cognitive fMRI studies and scanner calibration. PMID:16563961

Renvall, Ville; Joensuu, Raimo; Hari, Riitta

2006-02-20

212

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

213

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 in an open high-field magnetic resonance imaging (MRI) scanner at 1.0T with vertical field orientation. Five commercially available MRI-compatible puncture needles were assessed based on artefact characteristics in a CuSO4 phantom (0.1%) and in human cadaveric lumbar spines. First, six different interventional sequences

Uta Wonneberger; Bernhard Schnackenburg; Florian Streitparth; Thula Walter; Jens Rump; Ulf K. M. Teichgraeber

2010-01-01

214

Simplified MRI  

NSDL National Science Digital Library

Is it a tumor? Magnetic Resonance Imaging (MRI) can tell. Your head is full of tiny radio transmitters (the nuclear spins of the hydrogen nuclei of your water molecules). In an MRI unit, these little radios can be made to broadcast their positions, giving a detailed picture of the inside of your head.

Simulations, Phet I.; Dubson, Michael; Lemaster, Ron; Mckagan, Sam; Perkins, Kathy; Wieman, Carl

2006-07-01

215

Fully Automatic Segmentation of the Brain in MRI  

Microsoft Academic Search

A robust fully automatic method for segmenting the brain from head magnetic resonance (MR) images has been developed, which works even in the presence of radio frequency (RF) inhomogeneities. It has been successful in segmenting the brain in every slice from head images acquired from several different MRI scanners, using different-resolution images and different echo sequences. The method uses an

M. Stella Atkins; Blair T. Mackiewich

1998-01-01

216

Recognition and tracking of magnetic nanobots using MRI  

Microsoft Academic Search

By switching the gradient fields of a clinical magnetic resonance imaging (MRI) scanner, magnetic objects may be moved inside the cardiovascular system of the human body. The main field of application is seen in targeted drug therapy or embolization. A successful navigation of such devices requires continuous position determination. The occurrence of magnetic susceptibility artifacts can be exploited for this

Tim Wortmann; Christian Dahmen; Christian Geldmann; Sergej Fatikow

2010-01-01

217

A fully 3D small PET scanner.  

PubMed

A fully 3D small PET scanner based on a novel detection principle for gamma rays is described. It uses BaF2 scintillator and photosensitive wire chambers. Extensive tests with technical prototypes have shown that such a system will have a detection efficiency for gamma rays comparable with what can be obtained with the more traditional approach, and a spatial resolution determined by the size of the crystals. The expected performances of the scanner, based on our measurements and on simulations, are given. PMID:1565695

Tavernier, S; Bruyndonckx, P; Shuping, Z

1992-03-01

218

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

219

Evaluation of patellar alignment and tracking: comparison between kinematic MRI and “true” dynamic imaging by hyperscan MRI  

Microsoft Academic Search

Patellar malalignment and maltracking are primary causes of patellofemoral joint (PFJ) pain. Kinematic MRI has been demonstrated to be a sensitive method of assessing PFJ pathology. This technique, however, precludes the dynamic involvement of active muscles which may alter patellar tracking and alignment. Using the Instascan method (Advanced NMR Systems, Woburn, MA) on a modified General Electric (Milwaukee, WI) scanner,

FG Shellock; M. S. Cohen; T Brady; JH Mink; M Pfaff

220

The Usefulness of Fetal MRI for Prenatal Diagnosis  

PubMed Central

Purpose Fast MRI has provided detailed and reproducible fetal anatomy. This study was performed to evaluate the usefulness of fetal MRI for prenatal diagnosis. Materials and Methods Fifty-six fetuses with congenital abnormalities on ultrasonography were evaluated by fetal MRI from 2001 to 2004 in Severance Hospital. Final diagnosis was made by postnatal pathology, postnatal MRI, and other modalities (such as ultrasound, retrograde pyelogram). A 1.5-Tesla superconductive MR imaging unit was used to obtain half-Fourier acquisition single-shot turbo spin images. Results Of the 56 fetuses, intracranial abnormalities were found in 26 fetuses, intraabdominal abnormalities in 17 fetuses, intrathoracic in 6 fetuses, head and neck in 5 fetuses, and other sites in 2 fetuses. There were six cases in which the diagnoses of fetal MRI and ultrasonography differed. In such cases, fetal MRI provided more exact diagnosis than ultrasonography (5 vs. 0). Three fetuses with intracranial abnormalities on ultrasonography were diagnosed as normal by fetal MRI and in postnatal diagnosis. Conclusion Although ultrasonography is known as a screening modality of choice in the evaluation of fetus because of the cost-effectiveness and safety, the sonographic findings are occasionally inconclusive or insufficient for choosing the proper management. Thus, in this study, we suggest that fetal MRI is more useful than ultrasonography for the evaluation of intracranial abnormalities in some instances. For prenatal counseling and postnatal treatment planning, fetal MRI can be informative when prenatal ultrasonography is inadequate and doubtful.

Sohn, Yong-Seok; Kim, Myung-Joon; Kwon, Ja-Young; Kim, Young-Han

2007-01-01

221

Development of simulation tools for small animal SPECT\\/MRI reconstruction study  

Microsoft Academic Search

The goal of this study is to develop simulation tools for a proposed simultaneous SPECT\\/MRI system. The proposed SPECT\\/MRI system is based on a clinical 3T MRI scanner and a ring-type SPECT subsystem using cadmium zinc telluride (CZT) detectors and pinhole or multi-pinhole collimators. Geant4 applications for emission tomography (GATE) was used to simulate the gamma-ray photon transportation process in

Si Chen; Yuchuan Wang; Benjamin M. W. Tsui

2007-01-01

222

Inter-observer agreement and diagnostic accuracy of myocardial perfusion reserve quantification by cardiovascular magnetic resonance at 3 Tesla in comparison to quantitative coronary angiography  

PubMed Central

Background Quantification of cardiovascular magnetic resonance (CMR) myocardial perfusion reserve (MPR) at 1.5 Tesla has been shown to correlate to invasive evaluation of coronary artery disease (CAD) and to yield good inter-observer agreement. However, little is known about quantitative adenosine-perfusion CMR at 3 Tesla and no data about inter-observer agreement is available. Aim of our study was to evaluate inter-observer agreement and to assess the diagnostic accuracy in comparison to quantitative coronary angiography (QCA). Methods Fifty-three patients referred for coronary x-ray angiography were previously examined in a 3 Tesla whole-body scanner. Adenosine and rest perfusion CMR were acquired for the quantification of MPR in all segments. Two blinded and independent readers analyzed all images. QCA was performed in case of coronary stenosis. QCA data was used to assess diagnostic accuracy of the MPR measurements. Results Inter-observer agreement was high for all myocardial perfusion territories (??=?0.92 for LAD, ??=?0.93 for CX and RCA perfused segments). Compared to QCA receiver-operating characteristics yielded an area under the curve of 0.78 and 0.73 for RCA, 0.66 and 0.69 for LAD, and 0.52 and 0.53 for LCX perfused territories. Conclusions Inter-observer agreement of MPR quantification at 3 Tesla CMR is very high for all myocardial segments. Diagnostic accuracy in comparison to QCA yields good values for the RCA and LAD perfused territories, but moderate values for the posterior LCX perfused myocardial segments.

2013-01-01

223

Perivenular brain lesions in a primate multiple sclerosis model at 7-tesla magnetic resonance imaging.  

PubMed

BACKGROUND Magnetic resonance imaging (MRI) can provide in vivo assessment of tissue damage, allowing evaluation of multiple sclerosis (MS) lesion evolution over time - a perspective not obtainable with postmortem histopathology. Relapsing-remitting experimental autoimmune encephalomyelitis (EAE) is an experimental model of MS that can be induced in the common marmoset, a small new world primate, and that causes perivenular white matter (WM) lesions similar to those observed in MS. METHODS Brain lesion development and evolution were studied in vivo and postmortem in four marmosets with EAE through serial T2- and T2*-weighted scans at 7-tesla. Supratentorial WM lesions were identified and characterized. RESULTS Of 97 lesions observed, 86 (88%) were clearly perivenular, and 62 (72%) developed around veins that were visible even prior to EAE induction. The perivenular configuration was confirmed by postmortem histopathology. Most affected veins, and their related perivascular Virchow-Robin spaces, passed into the subarachnoid space rather than the ventricles. CONCLUSION As in human MS, the intimate association between small veins and EAE lesions in the marmoset can be studied with serial in vivo MRI. This further strengthens the usefulness of this model for understanding the process of perivenular lesion development and accompanying tissue destruction in MS. PMID:23773983

Gaitán, María I; Maggi, Pietro; Wohler, Jillian; Leibovitch, Emily; Sati, Pascal; Calandri, Ismael L; Merkle, Hellmut; Massacesi, Luca; Silva, Afonso C; Jacobson, Steven; Reich, Daniel S

2013-06-17

224

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

225

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

226

Comb Actuated resonant torsional scanner for microdisplays  

Microsoft Academic Search

A comb-actuated 1D torsional MEMS scanner is developed for high resolution projection display systems using mechanical coupling principle. 64deg TOSA (total optical scan angle) is achieved at 22.1 kHz with 170 V peak-to-peak excitation voltages.

Aslihan Arslan; Sven Holmstrom; S. Kutal Gokce; Hakan Urey

2009-01-01

227

Dedicated PET scanners for breast imaging  

NASA Astrophysics Data System (ADS)

We have used computer simulations to compare two designs for a PET scanner dedicated to breast imaging with a whole-body PET scanner. The new designs combine high spatial resolution, high sensitivity, and good energy resolution to detect small, low-contrast masses. The detectors are position sensitive NaI(Tl) scintillators. The first design is a ring scanner surrounding the breast and the second consists of two planar detectors placed on opposite sides of the breast. We have employed standard performance measures to compare the different designs: contrast, percentage standard deviation of the background, and signal-to-noise ratios of reconstructed images. The results of the simulations show that both of the proposed designs have better lesion detectability than a whole-body scanner. The results also show that contrast is higher in the ring breast system but that the noise is lower in the planar breast system. Overall, the ring system yields images with the best signal-to-noise ratios, although the planar system offers practical advantages for imaging the breast and axilla.

Freifelder, Richard; Karp, Joel S.

1997-12-01

228

Coastal Zone Color Scanner Studies. Abstract Only.  

National Technical Information Service (NTIS)

Activities over the past year have included cooperative work with a summer faculty fellow using the Coastal Zone Color Scanner (CZCS) imagery to study the effects of gradients in trophic resources on coral reefs in the Caribbean. Other research included c...

J. Elrod

1988-01-01

229

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

230

Holographic Three Dimensional Printer Using Galvanometer Scanners  

Microsoft Academic Search

To make holograms from computer graphic (CG) in a short time, a new holographic three dimensional (3D) printer is proposed here. This printer consists of galvanometer scanners, a micro computer and a laser, and uses a holographic contact duplicating method. Experiments have shown that a hologram of 39 × 41 mm can be obtained in 4 min.

Masahide Monde; Tsuyoshi Uematsu; Toshiki Toda; Kazuhiko Ohnuma; Yoshizumi Yasuda

1995-01-01

231

The ClearPEM breast imaging scanner  

NASA Astrophysics Data System (ADS)

We present results on the characterization of the ClearPEM breast imaging scanner. ClearPEM is a dual-head positron emission mammography scanner using APD-based detector modules that are capable of measuring the depth-of-interaction (DOI) with a resolution of 2 mm in LYSO:Ce crystals. The full system comprises 192 detector modules with a total of 6144 LYSO:Ce crystals and 384 32-pixel APD arrays read out by ASICs with 192 input channels. The scanner includes front-end and data acquisition electronics and a robotic gantry for detector placement and rotation. The software implements calibration (energy, time and DOI), normalization and image reconstruction algorithms. In this conference, the scanner main technical characteristics, the calibration strategies and the spectrometric performance in clinical environment were presented as well as the images obtained with point sources and with a microDerenzo phantom. The image resolution was found to be of the order of 1.3 mm FWHM (center of field-of-view) and the DOI capability has shown to have a strong impact on the image sharpness. An assessment of the first clinical experience was also presented at the conference.

Neves, Jorge A.; ClearPEM Collaboration

2011-02-01

232

Holographic Three Dimensional Printer Using Galvanometer Scanners  

NASA Astrophysics Data System (ADS)

To make holograms from computer graphic (CG) in a short time, a new holographic three dimensional (3D) printer is proposed here. This printer consists of galvanometer scanners, a micro computer and a laser, and uses a holographic contact duplicating method. Experiments have shown that a hologram of 39 × 41 mm can be obtained in 4 min.

Monde, Masahide; Uematsu, Tsuyoshi; Toda, Toshiki; Ohnuma, Kazuhiko; Yasuda, Yoshizumi

1995-05-01

233

Artifacts caused by cochlear implants with non-removable magnets in 3T MRI: phantom and cadaveric studies  

Microsoft Academic Search

The aim of this study was to evaluate artifacts produced by cochlear implants (CI) during 3.0 Tesla (T) magnetic resonance\\u000a imaging of the brain using different sequences on phantom and cadaveric specimens. A phantom and three cadaveric specimens\\u000a with CIs were imaged using a 3.0 T clinical scanner. Artifacts were analyzed quantitatively and according to the sequence\\u000a used. Different brain

Omid Majdani; Thomas S. Rau; Friedrich Götz; Martin Zimmerling; Minoo Lenarz; Thomas Lenarz; Robert Labadie; Martin Leinung

2009-01-01

234

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

235

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

236

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

237

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

238

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

239

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

240

21 CFR 892.1330 - Nuclear whole body scanner.  

Code of Federal Regulations, 2010 CFR

...Diagnostic Devices § 892.1330 Nuclear whole body scanner. (a) Identification. A nuclear whole body scanner is a device intended to measure and image the distribution of radionuclides in the body by means of a wide-aperture...

2009-04-01

241

21 CFR 892.1330 - Nuclear whole body scanner.  

Code of Federal Regulations, 2010 CFR

...Diagnostic Devices § 892.1330 Nuclear whole body scanner. (a) Identification. A nuclear whole body scanner is a device intended to measure and image the distribution of radionuclides in the body by means of a wide-aperture...

2010-04-01

242

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

243

Cardiac MRI  

MedlinePLUS

... Blogger. Share this page from the NHLBI on Buzz. Share this page from the NHLBI on Delicious. ... inserted into your body. MRI uses radio waves, magnets, and a computer to create pictures of your ...

244

Chest MRI  

MedlinePLUS

... Blogger. Share this page from the NHLBI on Buzz. Share this page from the NHLBI on Delicious. ... and blood vessels. Chest MRI uses radio waves, magnets, and a computer to create these pictures. The ...

245

Endourethral MRI  

Microsoft Academic Search

Although high-resolution MRI with phased array pelvic, endo- rectal, and endovaginal coils has dramatically enhanced the ability to visualize abnormalities of the female urethra and peri- urethral tissues, controversy still remains about the anatomy of this region. This study introduces an endourethral approach for ultra-high-resolution MRI of the female urethra and the periure- thral tissues. To this end, two different

Harald H. Quick; Jean-Michel Serfaty; Harpreet K. Pannu; Rene Genadry; Christopher J. Yeung; Ergin Atalar

2001-01-01

246

NECR analysis of 3D brain PET scanner designs  

Microsoft Academic Search

A dedicated 3D brain PET scanner has several advantages, most notably increased sensitivity, over a whole body scanner for neurological studies. However, brain scanners have higher scatter fractions, random count-rates and deadtime for the same activity concentration. We have used noise effective count-rate (NECR) analysis to compare brain scanners of 53, 60, and 66 cm diameter with the GE ADVANCE

Charles W. Stearns; Simon R. Cherry; C. J. Thompson

1995-01-01

247

An ultra fast electron beam x-ray tomography scanner  

Microsoft Academic Search

This paper introduces the design of an ultra fast x-ray tomography scanner based on electron beam technology. The scanner has been developed for two-phase flow studies where frame rates of 1 kHz and higher are required. Its functional principle is similar to that of the electron beam x-ray CT scanners used in cardiac imaging. Thus, the scanner comprises an electron

248

Studying the effect of noise on the performance of 2D and 3D texture measures for quantifying the trabecular bone structure as obtained with high resolution MR imaging at 3 tesla  

NASA Astrophysics Data System (ADS)

3.0 Tesla MRI devices are becoming popular in clinical applications since they render images with a higher signal-tonoise ratio than the former 1.5 Tesla MRI devices. Here, we investigate if higher signal-to-noise ratio can be beneficial for a quantitative image analysis in the context of bone research. We performed a detailed analysis of the effect of noise on the performance of 2D morphometric linear measures and a 3D nonlinear measure with respect to their correlation with biomechanical properties of the bone expressed by the maximum compressive strength. The performance of both 2D and 3D texture measures was relatively insensitive to superimposed artificial noise. This finding suggests that MR sequences for visualizing bone structures at 3T should rather be optimized to spatial resolution (or scanning time) than to signal-to-noise ratio.

Monetti, Roberto; Bauer, Jan; Mueller, Dirk; Rummeny, Ernst J.; Link, Thomas M.; Majumdar, Sharmila; Matsuura, Maiko; Eckstein, Felix; Sidorenko, Irina; Raeth, Christoph W.

2008-04-01

249

NECR analysis of 3D brain PET scanner designs  

SciTech Connect

A dedicated 3D brain PET scanner has several advantages, most notably increased sensitivity, over a whole body scanner for neurological studies. However brain scanners have higher scatter fractions, random count-rates and deadtime for the same activity concentration. The authors have used noise effective count-rate (NECR) analysis to compare brain scanners of 53, 60, and 66 cm diameter with the GE Advance whole body scanner (93 cm diameter). Monte Carlo simulations of a brain-sized phantom (16 cm diameter, 13 cm length) in the Advance geometry were used to develop a model for NECR performance, which was reconciled to results from a decay series measurement. The model was then used to predict the performance of the brain scanner designs. The brain scanners have noise effective sensitivities (the slope of the NECR curve at zero activity) as much as 40% higher than the body scanner. However, their NECR advantage diminishes quickly as the activity concentration increases. The brain scanners` NECR equals the body scanner with about 0.7--0.8 mCi in the phantom; the body scanner has superior NECR performance at higher activity levels. An imaging center concentrating on only very low activity imaging tasks would find the efficiency advantage of a smaller detector diameter valuable, while a center performing higher activity studies such as bolus water injections or 5 mCi FDG injections might prefer the count rate performance of a whole body scanner.

Stearns, C.W. [GE Medical Systems, Milwaukee, WI (United States). Applied Science Lab.; Cherry, S.R. [Univ. of California, Los Angeles, CA (United States). School of Medicine; Thompson, C.J. [Montreal Neurological Inst., Quebec (Canada)

1995-08-01

250

Gadolinium Enhanced MR Coronary Vessel Wall Imaging at 3.0 Tesla  

PubMed Central

Purpose. We evaluated the influence of the time between low-dose gadolinium (Gd) contrast administration and coronary vessel wall enhancement (LGE) detected by 3T magnetic resonance imaging (MRI) in healthy subjects and patients with coronary artery disease (CAD). Materials and Methods. Four healthy subjects (4 men, mean age 29 ± 3 years and eleven CAD patients (6 women, mean age 61 ± 10 years) were studied on a commercial 3.0 Tesla (T) whole-body MR imaging system (Achieva 3.0 T; Philips, Best, The Netherlands). T1-weighted inversion-recovery coronary magnetic resonance imaging (MRI) was repeated up to 75 minutes after administration of low-dose Gadolinium (Gd) (0.1?mmol/kg Gd-DTPA). Results. LGE was seen in none of the healthy subjects, however in all of the CAD patients. In CAD patients, fifty-six of 62 (90.3%) segments showed LGE of the coronary artery vessel wall at time-interval 1 after contrast. At time-interval 2, 34 of 42 (81.0%) and at time-interval 3, 29 of 39 evaluable segments (74.4%) were enhanced. Conclusion. In this work, we demonstrate LGE of the coronary artery vessel wall using 3.0 T MRI after a single, low-dose Gd contrast injection in CAD patients but not in healthy subjects. In the majority of the evaluated coronary segments in CAD patients, LGE of the coronary vessel wall was already detectable 30–45 minutes after administration of the contrast agent.

Kelle, Sebastian; Schlendorf, Kelly; Hirsch, Glenn A.; Gerstenblith, Gary; Fleck, Eckart; Weiss, Robert G.; Stuber, Matthias

2010-01-01

251

Evaluation of intraorbital prosthetic pigmentation using 0.3 and 1.5 Tesla magnetic resonance imaging and computed tomography.  

PubMed

PURPOSE: To investigate the magnetic susceptibility artifact associated with pigmented intraorbital prosthetics when performing magnetic resonance imaging (MRI) and computed tomography (CT). Potential artifact reduction techniques were also investigated. STUDY DESIGN: Prospective study. METHODS: Five different-colored 20-millimeter small animal silicone intraorbital prosthetics and two equine prosthetics were evaluated using 0.3 and 1.5 Tesla (T) MRI and CT. MRI sequences included T1- (T1WI) and T2-weighted spin echo (T2WI), T2 gradient echo (T2*), short tau inversion recovery (STIR), and fluid-attenuated inversion recovery (FLAIR). When present, artifact size was measured using computerized software by three separate observers. Artifact reduction techniques included alterations in receiver bandwidth, field of view, slice thickness, and matrix size. RESULTS: The ferrous brown-pigmented prosthetic resulted in a magnetic susceptibility artifact with MRI. No artifact was observed on CT images. Interobserver variability was not statistically significant. For both the 0.3T and 1.5T MRI, the T2* sequence exhibited the largest artifact surface area followed by T2WI, T1WI, STIR, and FLAIR. Decreasing slice thickness showed a decrease in artifact size; however, this difference was not statistically significant. CONCLUSIONS: The ferrous substances in the brown intraorbital prosthetic resulted in a significant magnetic susceptibility artifact when performing MRI. Artifact reduction techniques did not significantly decrease artifact surface area. The use of ferrous brown-pigmented prosthetics and their potential to affect future MR imaging studies should be adequately discussed with pet owners. PMID:23738745

Dustin Dees, D; Maclaren, Nicole E; Fritz, Kevin J; Broome, Michael R; Esson, Douglas W

2013-06-01

252

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

253

Eye dominance in the visual cortex using functional MRI at 1.5 T: An alternative method  

Microsoft Academic Search

Purpose: To develop a functional MRI method for producing eye dominance histograms in humans at 1.5 Tesla (T). Methods: In the first set of experiments, 8 normal persons were tested. The eye dominance of each voxel within the person's visually activated primary visual cortex was determined with Student t statistics during a left eye versus right eye contrast. Eye dominance

Grant T. Liu; Atsushi Miki; Zachariah Goldsmith; Theo G. M. van Erp; Ellie Francis; Graham E. Quinn; Edward J. Modestino; Gabrielle R. Bonhomme; John C. Haselgrove

2002-01-01

254

Subpicosecond bunch length measurement at the TESLA test facility  

Microsoft Academic Search

Sub-picosecond electron bunches are required for the operation of future VUV and X-ray Free Electron Lasers. A streak camera, a Martin–Puplett interferometer and a longitudinal phase space rotation method have been applied at the TESLA Test Facility linac to measure electron bunch lengths.

M. Geitz; G. Schmidt; P. Schmüser; G. v. Walter

2000-01-01

255

The short-range transverse Wakefields in Tesla accelerating structure  

Microsoft Academic Search

The operation of a Free Electron Laser in TESLA project requires very short bunches. This results in a very long interaction length between the bunch and the wakefields. From this fact severe problems for computer simulations arise. The longitudinal case was recently studied intensively by Novokhatski et al.(1). In this paper we study mainly the transverse forces. Using a recently

I. Zagorodnov; Thomas Weiland

2003-01-01

256

Bunch compressor II at the TESLA Test Facility  

Microsoft Academic Search

In the TESLA Test Facility (TTF), short bunches with low emittance are needed for the operation of a free electron laser. Several stages of bunch compression by means of magnetic chicanes will be used to reach the required peak current. The second stage of the bunch compression system, bunch compressor II, has been taken into operation recently. We describe design

M. Geitz; A. Kabel; G. Schmidt; H. Weise

1999-01-01

257

Large-Signal Code TESLA: Current Status and Recent Development.  

National Technical Information Service (NTIS)

The optimization and design of new high-power, high-efficiency klystron amplifiers relies increasingly on effective nonlinear simulation tools. One such tool is the large-signal code TESLA, which was successfully applied for the modeling of single-beam an...

A. N. Vlasov B. Levush D. K. Abe I. A. Chernyavskiy S. J. Cooke

2008-01-01

258

FEASIBILITY STUDY OF A HOM IOT FOR TESLA  

Microsoft Academic Search

For the TESLA linear collider 1.3 GHz RF sources with 10 MW peak power and about 70% efficiency are needed. As an alternative to the development of a Multibeam-Klystron, we investigate the feasibility of an IOT (Inductive Output Tube). This is a very compact RF source: The time struc- ture of the beam is produced by a gated emission cathode

P. Sch; T. Weiland; A. Gamp

1998-01-01

259

Feasibility study of a HOM IOT for TESLA  

Microsoft Academic Search

For the TESLA linear collider 1.3 GHz RF sources with 10 MW peak power and about 70% efficiency are needed. As an alternative to the development of a multibeam-klystron, we investigate the feasibility of an IOT (inductive output tube). This is a very compact RF source: the time structure of the beam is produced by a gated emission cathode and

P. Schutt; Thomas Weiland; Alexander Gamp; Fuhai Lu

1997-01-01

260

TESLA FEL Gun simulations with PARMELA and MAFIA  

SciTech Connect

The most recent simulation results of the DESY TESLA FEL gun are presented. Two codes are used: PARMELA and MAFIA. Since the two use different schemes in particle simulations, we will address their differences and try to give an explanation for them.

Zhang Min; Schuett, Petra [Deutches Elektronen Synchrotron (DESY)-MPY-, Notkestr. 85, D-22603 Hamburg (Germany); FB 18, Fachgebiet Theorie Elektromagnetischer Felder, TH Darmstadt, Schlossgartenstr. 8, D-64289 Darmstadt (Germany)

1997-02-01

261

Radiation safety aspects of the TESLA test facility, phase 2  

Microsoft Academic Search

The commissioning of the TESLA test facility (TTF) in its second phase of the Deutsches Elektronen-Synchrotron (DESY) in Hamburg, Germany started by the end of 2004. It had been planned to test accelerator components in cold technology and to be operated for users as a vacuum ultraviolet free electron laser (VUV-FEL). The primary electron beam is accelerated to energies up

Albrecht Leuschner

2006-01-01

262

Tesla coil discharges guided by femtosecond laser filaments in air  

NASA Astrophysics Data System (ADS)

A Tesla coil generator was designed to produce high voltage pulses oscillating at 100 kHz synchronisable with a nanosecond temporal jitter. Using this compact high voltage generator, we demonstrate reproducible meter long discharges in air at a repetition rate of 1 Hz. Triggering and guiding of the discharges are performed in air by femtosecond laser filaments.

Brelet, Yohann; Houard, Aurélien; Arantchouk, Leonid; Forestier, Benjamin; Liu, Yi; Prade, Bernard; Carbonnel, Jérôme; André, Yves-Bernard; Mysyrowicz, André

2012-04-01

263

Improved T1 mapping by motion correction and template based B1 correction in 3T MRI brain studies  

Microsoft Academic Search

Accurate estimation of relaxation time T1 from MRI images is increasingly important for some clinical applications. Low noise, high resolution, fast and accurate T1 maps from MRI images of the brain can be performed using a dual flip angle method. However, accuracy is limited by the scanners ability to deliver the prescribed flip angle due to the B1 inhomogeneity, particularly

Marcelo A. Castro; Jianhua Yao; Christabel Lee; Yuxi Pang; Eva Baker; John Butman; David Thomasson

2009-01-01

264

In vivo MRI quantification of individual muscle and organ volumes for assessment of anabolic steroid growth effects  

Microsoft Academic Search

This study aimed to develop a quantitative and in vivo magnetic resonance imaging (MRI) approach to investigate the muscle growth effects of anabolic steroids. A protocol of MRI acquisition on a standard clinical 1.5T scanner and quantitative image analysis was established and employed to measure the individual muscle and organ volumes in the intact and castrated guinea pigs undergoing a

Ed X. Wu; Haiying Tang; Christopher Tong; Steve B. Heymsfield; Joseph R. Vasselli

2008-01-01

265

Development of a PET detector system compatible with MRI\\/NMR systems  

Microsoft Academic Search

We report the development of a prototype positron emission tomography (PET) scanner compatible with clinical magnetic resonance imaging (MRI) scanners and nuclear magnetic resonance (NMR) spectrometers. This single slice PET system consists of 72 2×2×5 mm lutetium oxyorthosilicate (LSO) crystals coupled by 2 mm diameter, 4 meter long double clad optical fibers to three multi-channel photomultiplier tubes (MC-PMTs) shielded inside

Y. Shao; S. R. Cherry; K. Farahani; R. Slates; R. W. Silverman; K. Meadors; A. Bowery; S. Siegel; P. K. Marsden; P. B. Garlick

1997-01-01

266

Simultaneous bilateral hip joint imaging at 7 Tesla using fast transmit B? shimming methods and multichannel transmission - a feasibility study.  

PubMed

The objective of this study was to demonstrate the feasibility of simultaneous bilateral hip imaging at 7 Tesla. Hip joint MRI becomes clinically critical since recent advances have made hip arthroscopy an efficacious approach to treat a variety of early hip diseases. The success of these treatments requires a reliable and accurate diagnosis of intraarticular abnormalities at an early stage. Articular cartilage assessment is especially important to guide surgical decisions but is difficult to achieve with current MR methods. Because of gains in tissue contrast and spatial resolution reported at ultra high magnetic fields, there are strong expectations that imaging the hip joint at 7 Tesla will improve diagnostic accuracy. Furthermore, there is growing evidence that the majority of these hip abnormalities occur bilaterally, emphasizing the need for bilateral imaging. However, obtaining high quality images in the human torso, in particular of both hips simultaneously, must overcome a major challenge arising from the damped traveling wave behaviour of RF waves at 7 Tesla that leads to severe inhomogeneities in transmit B1 (B(1) (+) ) phase and magnitude, typically resulting in areas of low signal and contrast, and consequently impairing use for clinical applications. To overcome this problem, a 16-channel stripline transceiver RF coil was used, together with a B1 shimming algorithm aiming at maximizing B(1) (+) in six regions of interest over the hips that were identified on axial scout images. Our successful results demonstrate that this approach effectively reduces inhomogeneities observed before B1 shimming and provides high joint tissue contrast in both hips while reducing the required RF power. Critical to this success was a fast small flip angle B(1) (+) calibration scan that permitted the computation of subject-specific B1 shimming solutions, a necessary step to account for large spatial variations in B(1) (+) phase observed in different subjects. PMID:22311346

Ellermann, J; Goerke, U; Morgan, P; Ugurbil, K; Tian, J; Schmitter, S; Vaughan, T; Van De Moortele, P-F

2012-02-07

267

Detector Position Estimation for PET Scanners  

PubMed Central

Physical positioning of scintillation crystal detector blocks in Positron Emission Tomography (PET) scanners is not always exact. We test a proof of concept methodology for the determination of the six degrees of freedom for detector block positioning errors by utilizing a rotating point source over stepped axial intervals. To test our method, we created computer simulations of seven Micro Crystal Element Scanner (MiCES) PET systems with randomized positioning errors. The computer simulations show that our positioning algorithm can estimate the positions of the block detectors to an average of one-seventh of the crystal pitch tangentially, and one-third of the crystal pitch axially. Virtual acquisitions of a point source grid and a distributed phantom show that our algorithm improves both the quantitative and qualitative accuracy of the reconstructed objects. We believe this estimation algorithm is a practical and accurate method for determining the spatial positions of scintillation detector blocks.

Pierce, Larry; Miyaoka, Robert; Lewellen, Tom; Alessio, Adam; Kinahan, Paul

2012-01-01

268

Ghost signals in Allison emittance scanners  

SciTech Connect

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.; /SNS Project, Oak Ridge /Tennessee U.; Leitner, M.; /LBL, Berkeley; Moehs, D.P.; /Fermilab; Keller, R.; /LBL, Berkeley; Welton, R.F.; /SNS Project, Oak Ridge /Tennessee U.

2004-12-01

269

The Galileo star scanner observations at Amalthea  

NASA Astrophysics Data System (ADS)

In November of 2002, the Galileo spacecraft passed within 250 km of Jupiter's moon Amalthea. An onboard telescope, the star scanner, observed a series of bright flashes near the moon. It is believed that these flashes represent sunlight reflected from 7 to 9 small moonlets located within about 3000 km of Amalthea. From star scanner geometry considerations and other arguments, we can constrain the diameter of the observed bodies to be between 0.5 m to several tens of kilometers. In September of 2003, while crossing Amalthea's orbit just prior to Galileo's destruction in the jovian atmosphere, a single additional body seems to have been observed. It is suspected that these bodies are part of a discrete rocky ring embedded within Jupiter's Gossamer ring system.

Fieseler, Paul D.; Adams, Olen W.; Vandermey, Nancy; Theilig, E. E.; Schimmels, Kathryn A.; Lewis, George D.; Ardalan, Shadan M.; Alexander, Claudia J.

2004-06-01

270

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

271

Microarray scanner calibration curves: characteristics and implications  

Microsoft Academic Search

BACKGROUND: Microarray-based measurement of mRNA abundance assumes a linear relationship between the fluorescence intensity and the dye concentration. In reality, however, the calibration curve can be nonlinear. RESULTS: By scanning a microarray scanner calibration slide containing known concentrations of fluorescent dyes under 18 PMT gains, we were able to evaluate the differences in calibration characteristics of Cy5 and Cy3. First,

Leming M. Shi; Weida Tong; Zhenqiang Su; Tao Han; Jing Han; Raj K. Puri; Hong Fang; Felix W. Frueh; Federico M. Goodsaid; Lei Guo; William S. Branham; James J. Chen; Z. Alex Xu; Stephen C. Harris; Huixiao Hong; Qian Xie; Roger G Perkins; James C. Fuscoe

2005-01-01

272

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

273

JAS: The Next Generation Digital Aerial Scanner  

Microsoft Academic Search

With the experience from the spaceborne multi-spectral camera MKF-6 and the airborne MSK-4, Jena-Optronik now returns with the advanced and reliable JAS-150 to the market. Based on Jena-Optronik developments in the area of multi-line CCD sensors and know-how from other camera and spectrometer projects, the company has developed the most capable pushbroom scanner for remote sensing and photogrammetry. With nine

CARSTEN GEORGI; RALF STOGNIENKO; SVEN KNUTH; GERALD ALBE

274

Full-Body Scanners: TSA's New \\  

Microsoft Academic Search

While the world of commercial air transportation has seen major improvements in many technologies over the last decade, nothing has caused a stir quite like the implementation of full-body scanners (FBS) as a one of the first lines of defense in aviation security at U.S. airports. FBS and “enhanced” pat-downs have been the source of much debate and scrutiny among

Stuart A. Hindman

2011-01-01

275

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

276

Value of PCA3 to Predict Biopsy Outcome and Its Potential Role in Selecting Patients for Multiparametric MRI  

PubMed Central

PCA3 (prostate cancer gene 3) and multiparametric 3 tesla MRI are new promising diagnostic tools in the detection of PCa. Our aim was to study the clinical value of the Progensa PCA3-test: its predictive value for biopsy outcome, Gleason score and MRI outcome. We evaluated, retrospectively, 591 patients who underwent a Progensa PCA3-test at the Radboud University Nijmegen Medical Centre between May 2006 and December 2009. Prostate biopsies were performed in 290 patients; a multiparametric 3 tesla MRI of the prostate was performed in 163/591 patients. The PCA3-score was correlated to biopsy results and MRI outcome. The results show that PCA3 was highly predictive for biopsy outcome (p < 0.001); there was no correlation with the Gleason score upon biopsy (p = 0.194). The PCA3-score of patients with a suspicious region for PCa on MRI was significantly higher (p < 0.001) than in patients with no suspicious region on MRI (52 vs. 21). In conclusion, PCA3 is a valuable diagnostic biomarker for PCa; it did not correlate with the Gleason score. Furthermore, multiparametric MRI outcome was significantly correlated with the PCA3-score. Thus, PCA3 could be used to select patients that require MRI. However, in patients with a negative PCA3 and high clinical suspicion of PCa, a multiparametric MRI should also be done.

Leyten, Gisele H. J. M.; Wierenga, Elisabeth A.; Michiel Sedelaar, J. P.; van Oort, Inge M.; Futterer, Jurgen J.; Barentsz, Jelle O.; Schalken, Jack A.; Mulders, Peter F. A.

2013-01-01

277

A Novel MRI Marker for Prostate Brachytherapy  

SciTech Connect

Purpose: Magnetic resonance imaging (MRI) is the optimal imaging modality for the prostate and surrounding critical organ structures. However, on MRI, the titanium radioactive seeds used for brachytherapy appear as black holes (negative contrast) and cannot be accurately localized. We sought to develop an encapsulated contrast agent marker (ECAM) with high-signal intensity on MRI to permit accurate localization of radioactive seeds with MRI during and after prostate brachytherapy. Methods and Materials: We investigated several agents with paramagnetic and superparamagnetic properties. The agents were injected into titanium, acrylic, and glass seeds, which were linked together in various combinations and imaged with MRI. The agent with the greatest T1-weighted signal was tested further in a canine prostate and agarose phantom. Studies were performed on a 1.5-T clinical MRI scanner. Results: The cobalt-chloride complex contrast (C4) agent with stoichiometry (CoCl{sub 2}){sub 0.8}(C{sub 2}H{sub 5}NO{sub 2}){sub 0.2} had the greatest T1-weighted signal (positive contrast) with a relaxivity ratio >1 (r{sub 2}/r{sub 1} = 1.21 {+-} 0.29). Acrylic-titanium and glass-titanium seed strands were clearly visualized with the encapsulated contrast agent marker. Conclusion: We have developed a novel ECAM that permits positive identification of the radioactive seeds used for prostate brachytherapy on MRI. Preclinical in vitro phantom studies and in vivo canine studies are needed to further optimize MRI sequencing techniques to facilitate MRI-based dosimetry.

Frank, Steven J. [Department of Radiation Oncology, University of Texas M.D. Anderson Cancer Center, Houston, TX (United States)], E-mail: sjfrank@mdanderson.org; Stafford, R. Jason; Bankson, James A. [Department of Imaging Physics, University of Texas M.D. Anderson Cancer Center, Houston, TX (United States); Li Chun [Department of Experimental Diagnostic Imaging, University of Texas M.D. Anderson Cancer Center, Houston, TX (United States); Swanson, David A. [Department of Urology, University of Texas M.D. Anderson Cancer Center, Houston, TX (United States); Kudchadker, Rajat J. [Department of Radiation Physics, University of Texas M.D. Anderson Cancer Center, Houston, TX (United States); Martirosyan, Karen S. [Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX (United States)

2008-05-01

278

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

279

Design of a Second Generation Firewire Based Data Acquisition System for Small Animal PET Scanners  

PubMed Central

The University of Washington developed a Firewire based data acquisition system for the MiCES small animal PET scanner. Development work has continued on new imaging scanners that require more data channels and need to be able to operate within a MRI imaging system. To support these scanners, we have designed a new version of our data acquisition system that leverages the capabilities of modern field programmable gate arrays (FPGA). The new design preserves the basic approach of the original system, but puts almost all functions into the FPGA, including the Firewire elements, the embedded processor, and pulse timing and pulse integration. The design has been extended to support implementation of the position estimation and DOl algorithms developed for the cMiCE detector module. The design is centered around an acquisition node board (ANB) that includes 65 ADC channels, Firewire 1394b support, the FPGA, a serial command bus and signal lines to support a rough coincidence window implementation to reject singles events from being sent on the Firewire bus. Adapter boards convert detector signals into differential paired signals to connect to the ANB.

Lewellen, T.K.; Miyaoka, R.S.; MacDonald, L.R.; Haselman, M.; DeWitt, D.; Hunter, William; Hauck, S.

2009-01-01

280

A Robust Method for the Estimation of 4D Pharmacokinetic Parameters in dceMRI Data in Colorectal Cancer Patients  

Microsoft Academic Search

To date, most clinical studies of colorectal cancer patients have used only one or, more recently, two image slices through a tumour. This has largely been due to technological limitations in MRI scanners and to practical computational limits. Using high-speed multi-coil MRI machines, we have been able to capture and analyze full 4D datasets acquired from dceMRI on 20 human

Darren Morofke; Fergus V. Gleeson

281

Towards automatic quantitative quality control for MRI  

NASA Astrophysics Data System (ADS)

Quality and consistency of clinical and research data collected from Magnetic Resonance Imaging (MRI) scanners may become suspect due to a wide variety of common factors including, experimental changes, hardware degradation, hardware replacement, software updates, personnel changes, and observed imaging artifacts. Standard practice limits quality analysis to visual assessment by a researcher/clinician or a quantitative quality control based upon phantoms which may not be timely, cannot account for differing experimental protocol (e.g. gradient timings and strengths), and may not be pertinent to the data or experimental question at hand. This paper presents a parallel processing pipeline developed towards experiment specific automatic quantitative quality control of MRI data using diffusion tensor imaging (DTI) as an experimental test case. The pipeline consists of automatic identification of DTI scans run on the MRI scanner, calculation of DTI contrasts from the data, implementation of modern statistical methods (wild bootstrap and SIMEX) to assess variance and bias in DTI contrasts, and quality assessment via power calculations and normative values. For this pipeline, a DTI specific power calculation analysis is developed as well as the first incorporation of bias estimates in DTI data to improve statistical analysis.

Lauzon, Carolyn B.; Caffo, Brian C.; Landman, Bennett A.

2012-02-01

282

Towards Automatic Quantitative Quality Control for MRI.  

PubMed

Quality and consistency of clinical and research data collected from Magnetic Resonance Imaging (MRI) scanners may become suspect due to a wide variety of common factors including, experimental changes, hardware degradation, hardware replacement, software updates, personnel changes, and observed imaging artifacts. Standard practice limits quality analysis to visual assessment by a researcher/clinician or a quantitative quality control based upon phantoms which may not be timely, cannot account for differing experimental protocol (e.g. gradient timings and strengths), and may not be pertinent to the data or experimental question at hand. This paper presents a parallel processing pipeline developed towards experiment specific automatic quantitative quality control of MRI data using diffusion tensor imaging (DTI) as an experimental test case. The pipeline consists of automatic identification of DTI scans run on the MRI scanner, calculation of DTI contrasts from the data, implementation of modern statistical methods (wild bootstrap and SIMEX) to assess variance and bias in DTI contrasts, and quality assessment via power calculations and normative values. For this pipeline, a DTI specific power calculation analysis is developed as well as the first incorporation of bias estimates in DTI data to improve statistical analysis. PMID:23087586

Lauzon, Carolyn B; Caffo, Brian C; Landman, Bennett A

2012-02-23

283

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

284

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

285

Tesla Turbine from Old Hard Drives and Minimal Tools  

NSDL National Science Digital Library

This page provides step by step instructions on building a Tesla turbine from two old computer hard disk drives using basic hand tools and a pillar drill. No metal lathe or other expensive fabrication machinery is required and you only need some basic craft skills. It's crude, but this thing can scream! Tesla Turbines promise up to 92% efficiency of converting air or fluid flow to rotational energy and its use can also be inverted for use as a pump with exceptionally high efficiency too. With compressed air becoming recognized as a feasible form of energy storage, we can see this device in everyday life soon as a source of locomotion. Factoring the simplicity, robustness and resilience to ingress of this design and you have something ideal for pumping heterogeneous fluids like sewerage or fluids with suspended particulate. As a pump, this device has an important role to play in the developing world. This is a good student project.

2008-10-27

286

Techniques for Fast Stereoscopic MRI  

PubMed Central

Stereoscopic MRI can impart 3D perception with only two image acquisitions. This economy over standard multiplanar 3D volume renderings allows faster frame rates, which are needed for real-time imaging applications. Real-time 3D perception may enhance the appreciation of complex anatomical structures, and may improve hand-eye coordination while manipulating a medical device during an image-guided interventional procedure. To this goal, a system is being developed to acquire and display stereoscopic MR images in real-time. A clinically used, fast gradient-recalled echo-train sequence has been modified to produce stereo image pairs. Features have been added for depth cueing, view sharing, and bulk signal suppression. A workstation was attached to a clinical MR scanner for fast data extraction, image reconstruction and stereoscopic image display.

Guttman, Michael A.; McVeigh, Elliot R.

2007-01-01

287

Tuning for the first 9-cell TESLA cavity of PKU  

NASA Astrophysics Data System (ADS)

A method based on circuit model is used to tune the first home-made 9-cell TESLA type superconducting niobium cavity at Peking University. After tuning, a flat field profile with a final ?-mode frequency within 3 kHz of target frequency is achieved. The field flatness is measured by a bead-pull method, and the relative electric field is calculated from the frequency shift perturbed by the bead stepping along the axis of the cavity.

Yang, Liu; He, Fei-Si; Xu, Wen-Can; Zhu, Feng; Lu, Xiang-Yang; Zhao, Kui

2010-04-01

288

Developments and achievements at the TESLA test facility (TTF)  

Microsoft Academic Search

The TESLA Test Facility (TTF), under construction and commissioning at DESY International Collaboration, is an R&D test bench for the superconducting option for future linear electron-position colliders. TTF consists of an infrastructure to process and test the SC cavities and of a 400 MeV linac (Phase I), to be upgraded up to 1.2 GeV (Phase II). The infrastructure is fully

Carlo Pagani

1999-01-01

289

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

290

Improved surface treatment of the superconducting TESLA cavities  

Microsoft Academic Search

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

L. Lilje; C Z Antoine; Cristoforo Benvenuti; D. Bloess; J.-P. Charrier; Enrico Chiaveri; L. Ferreira; R. Losito; A. Matheisen; H. Preis; D. Proch; D. Reschke; H. Safa; P. Schmueser; D. Trines; B. Visentin; Horst Wenninger

2004-01-01

291

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

292

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

293

Fabrication of Optical Micro Scanner Driven by PZT Actuators  

NASA Astrophysics Data System (ADS)

We have designed, simulated, fabricated and tested microelectromechanical system (MEMS) based one-dimensional (1D) optical micro scanners driven by piezoelectric actuators. The designed micro scanners have a micro mirror (1 mm × 1 mm) supported by rotation bars connected to hinges and piezoelectric cantilevers. Pt/Ti/PZT/Pt/Ti/SiO2/SOI multi-layered structure was subjected to MEMS fabrication to form the micro scanners. Through the fabrication, we have obtained 3 types of scanners with 5, 10 and 20 ?m-wide hinges. The resonant frequency corresponding to a torsional mode was measured to be 4100, 5563 and 6025 Hz, respectively. We also compared the optical scanning angle of the micro scanners actuated at the resonant frequency. The micro scanner with 10 ?m-wide hinge actuated at 5563 Hz showed the widest scanning angle. The scanning angle reaches 25 deg at the actuation voltage of 20 V.

Kobayashi, Takeshi; Tsaur, Jiunnjye; Maeda, Ryutaro

2005-09-01

294

52. View from ground level showing lower radar scanner switch ...  

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

52. View from ground level showing lower radar scanner switch with open port door in radar scanner building 105 showing emanating waveguides from lower switch in vertical run; photograph also shows catwalk to upper scanner switch in upper left side of photograph and structural supports. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

295

Performance Measurement of the microPET Focus 120 Scanner  

Microsoft Academic Search

The microPET Focus 120 scanner is a third-generation animal PET scanner dedicated to rodent imaging. Here, we report the results of scanner performance testing. Methods: A 68Ge point sourcewasusedtomeasureenergyresolution,whichwasdeter- mined for each crystal and averaged. Spatial resolution was measured using a 22Na point source with a nominal size of 0.25 mm at the system center and various off-center positions. Abso-

Jin Su Kim; Jae Sung Lee; Ki Chun Im; Su Jin Kim; Seog-Young Kim; Dong Soo Lee; Dae Hyuk Moon

2007-01-01

296

Novel micro-scanner for optical communications: architecture and performance  

Microsoft Academic Search

Two-dimensional (2D) scanners have a variety of applications in displays, barcode readers, optical data storage devices, and free-space optical interconnects. In this paper, we will describe the modeling and simulation of a novel MEMS-based cantilever micro-scanner design. The micro-scanner is actuated using electrostatic force. The cantilever beam connects to the top electrode. The bottom four electrodes on the substrate provide

Dong Yan; Bai Xu; James Castracane

2002-01-01

297

Monitoring and correcting spatio-temporal variations of the MR scanner’s static magnetic field  

Microsoft Academic Search

The homogeneity and stability of the static magnetic field are of paramount importance to the accuracy of MR procedures that are sensitive to phase errors and magnetic field inhomogeneity. It is shown that intense gradient utilization in clinical horizontal-bore superconducting MR scanners of three different vendors results in main magnetic fields that vary on a long time scale both spatially

AbdEl Monem El-Sharkawy; Michael Schär; Paul A. Bottomley; Ergin Atalar

2006-01-01

298

A study of artefacts in simultaneous PET and MR imaging using a prototype MR compatible PET scanner  

NASA Astrophysics Data System (ADS)

We have assessed the possibility of artefacts that can arise in attempting to perform simultaneous positron emission tomography (PET) and magnetic resonance imaging (MRI) using a small prototype MR compatible PET scanner (McPET). In these experiments, we examine MR images for any major artefacts or loss in image quality due to inhomogeneities in the magnetic field, radiofrequency interference or susceptibility effects caused by operation of the PET system inside the MR scanner. In addition, possible artefacts in the PET images caused by the static and time-varying magnetic fields or radiofrequency interference from the MR system were investigated. Biological tissue and a T2-weighted spin echo sequence were used to examine susceptibility artefacts due to components of the McPET scanner (scintillator, optical fibres) situated in the MR field of view. A range of commonly used MR pulse sequences was studied while acquiring PET data to look for possible artefacts in either the PET or MR images. Other than a small loss in signal-to-noise using gradient echo sequences, there was no significant interaction between the two imaging systems. Simultaneous PET and MR imaging of simple phantoms was also carried out in different MR systems with field strengths ranging from 0.2 to 4.7 T. The results of these studies demonstrate that it is possible to acquire PET and MR images simultaneously, without any significant artefacts or loss in image quality, using our prototype MR compatible PET scanner.

Slates, Randal B.; Farahani, Keyvan; Shao, Yiping; Marsden, Paul K.; Taylor, Joanne; Summers, Paul E.; Williams, Steve; Beech, John; Cherry, Simon R.

1999-08-01

299

Low-Intensity Focused Ultrasound Pulsation Device Used During Magnetic Resonance Imaging: Evaluation of Magnetic Resonance Imaging-Related Heating at 3?Tesla/128?MHz.  

PubMed

OBJECTIVE: The objective of this study was to determine magnetic resonance imaging (MRI)-related heating for a low-intensity focused ultrasound pulsation (LIFUP) device used during MRI performed at 3?T/128?MHz. MATERIALS AND METHODS: A special phantom was constructed to mimic the thermal properties of the human brain, and a piece of human temporal bone (skull) was embedded on top. Four fluoroptic thermometry probes, placed above and below the skull, were used to measure temperature changes during MRI (3?T/128?MHz; scanner-reported head average specific absorption rate 1.1-2?W/kg) with and without concurrent LIFUP sonication. LIFUP sonication was applied using a focused ultrasound device (BXPulsar 1001, Brainsonix, Inc., Los Angeles, CA, USA) at a derated spatial-peak temporal-average intensity of 3870?mW/cm(2) . RESULTS: MRI performed at relatively high specific absorption rate (SAR) caused a slight elevation in temperature (?0.6°C). Concurrent use of MRI at a medium-strength SAR and LIFUP sonication resulted in maximum temperature rise of 3.1°C after 8?min of continuous use. CONCLUSIONS: Under the specific conditions utilized for this investigation, LIFUP sonication does not appear to present significant heating risks when used concurrently with MRI. This information has important implications for the use of the LIFUP sonication in human subjects undergoing MRI at 3?T/128?MHz. PMID:23663228

Korb, Alexander S; Shellock, Frank G; Cohen, Mark S; Bystritsky, Alexander

2013-05-10

300

New holographic technology for a compact POS scanner.  

PubMed

A new holographic technique has been used to make a compact, accurate, and reliable point-of-sale scanner. Our holo-window technique is capable of changing the scan direction, collecting the signal light, and equalizing the scan velocity. At present, compact scanners tend to sacrifice read operation accuracy, speed, and reliability for size. Our technique permits the miniaturization of the optical system of a scanner while preserving performance. Using the holo-window, we have developed a new scanner that has a letter-size footprint and is only 8 cm high. PMID:20563059

Yamazaki, K; Ichikawa, T; Aritake, H; Yamagishi, F; Ikeda, H; Inagaki, T

1990-04-10

301

An Assessment of Current Brain Targets for Deep Brain Stimulation Surgery With Susceptibility-Weighted Imaging at 7 Tesla  

PubMed Central

Background Deep brain stimulation (DBS) surgery is used for treating movement disorders, including Parkinson disease, essential tremor, and dystonia. Successful DBS surgery is critically dependent on precise placement of DBS electrodes into target structures. Frequently, DBS surgery relies on normalized atlas-derived diagrams that are superimposed on patient brain magnetic resonance imaging (MRI) scans, followed by microelectrode recording and macrostimulation to refine the ultimate electrode position. Microelectrode recording carries a risk of hemorrhage and requires active patient participation during surgery. Objective To enhance anatomic imaging for DBS surgery using high-field MRI with the ultimate goal of improving the accuracy of anatomic target selection. Methods Using a 7-T MRI scanner combined with an array of acquisition schemes using multiple image contrasts, we obtained high-resolution images of human deep nuclei in healthy subjects. Results Superior image resolution and contrast obtained at 7 T in vivo using susceptibility-weighted imaging dramatically improved anatomic delineation of DBS targets and allowed the identification of internal architecture within these targets. A patient-specific, 3-dimensional model of each target area was generated on the basis of the acquired images. Conclusion Technical developments in MRI at 7 T have yielded improved anatomic resolution of deep brain structures, thereby holding the promise of improving anatomic-based targeting for DBS surgery. Future study is needed to validate this technique in improving the accuracy of targeting in DBS surgery.

Abosch, Aviva; Yacoub, Essa; Ugurbil, Kamil; Harel, Noam

2011-01-01

302

Evaluating scanner lens spherical aberration using scatterometer  

NASA Astrophysics Data System (ADS)

Lens spherical error is an important lens aberration used to characterize lens quality and also has a significant contribution to across chip line width variation (ACLV). It also impacts tool-to-tool matching efforts especially when the optical lithography approaches sub-half wavelength geometry. Traditionally, spherical error is measured by using CD SEM with known drawbacks of poor accuracy and long cycle time. At Texas Instruments, an in-house scatterometer-based lens fingerprinting technique (ScatterLith) performs this tedious job accurately and quickly. This paper presents across slit spherical aberration signatures for ArF scanners collected using this method. The technique can successfully correlate these signatures with Litel lens aberration data and Nikon OCD data for spherical aberration errors as small as 10m?. ACLV contributions from such small spherical errors can be quantified using this method. This provides the lithographer with an important tool to evaluate, qualify and match advanced scanners to improve across chip line width variation control.

Wang, Changan; Zhang, Gary; Tan, Colin L.; Atkinson, Chris; Boehm, Mark A.; Brown, Jay M.; Godfrey, David; Littau, Michael E.; Raymond, Christopher J.

2003-06-01

303

A circularly focused and scanned acoustic scanner.  

PubMed

This paper describes a new type of electronically scanned and focused acoustic imaging device called the cylindrical grating acoustic scanner. With this device, a new transducer called the circular-edge-bonded transducer (CEBT) is devised that is bonded on one end of a cylindrical substrate and can generate a surface acoustic wave propagating along the cylindrical surface of the substrate. An array of grooves is fabricated on the cylindrical surface of the substrate to serve as a scattering grating. The periodical grooves scatter a chirped surface-wave pulse coherently into a focused bulk-wave "ring" that scans at the surface-wave velocity. The focal length and resolution can be adjusted by changing the chirp rate and time-bandwidth product of the chirp, respectively. A 2.3-MHz circular scanner with 25-cm field of view and 2.6-mm resolution has been constructed and studied. Acoustic image of an artificial defect in an aluminum pipe is obtained. PMID:18244300

Chen, W H

1999-01-01

304

Retrieval, Monitoring, and Control Processes: A 7 Tesla fMRI Approach to Memory Accuracy  

PubMed Central

Memory research has been guided by two powerful metaphors: the storehouse (computer) and the correspondence metaphor. The latter emphasizes the dependability of retrieved mnemonic information and draws upon ideas about the state dependency and reconstructive character of episodic memory. We used a new movie to unveil the neural correlates connected with retrieval, monitoring, and control processes, and memory accuracy (MAC), according to the paradigm of Koriat and Goldsmith (1996a,b). During functional magnetic resonance imaging, subjects performed a memory task which required (after an initial learning phase) rating true and false statements [retrieval phase (RP)], making confidence judgments in the respective statement [monitoring phase (MP)], and deciding for either venturing (volunteering) the respective answer or withholding the response [control phase (CP)]. Imaging data pointed to common and unique neural correlates. Activations in brain regions related to RP and MAC were observed in the precuneus, middle temporal gyrus, and left hippocampus. MP was associated with activation in the left anterior and posterior cingulate cortex along with bilateral medial temporal regions. If an answer was volunteered (as opposed to being withheld) during the CP, temporal, and frontal as well as middle and posterior cingulate areas and the precuneus revealed activations. Increased bilateral hippocampal activity was found during withholding compared to volunteering answers. The left caudate activation detected during withholding compared to venturing an answer supports the involvement of the left caudate in inhibiting unwanted responses. Contrary to expectations, we did not evidence prefrontal activations during withholding (as opposed to volunteering) answers. This may reflect our design specifications, but alternative interpretations are put forth.

Risius, Uda-Mareke; Staniloiu, Angelica; Piefke, Martina; Maderwald, Stefan; Schulte, Frank P.; Brand, Matthias; Markowitsch, Hans J.

2012-01-01

305

A 128-Channel Receive-Only Cardiac Coil for Highly Accelerated Cardiac MRI at 3 Tesla  

PubMed Central

A 128-channel receive-only array coil is described and tested for cardiac imaging at 3T. The coil is closely contoured to the body with a “clam-shell” geometry with 68 posterior and 60 anterior elements, each 75 mm in diameter, and arranged in a continuous overlapped array of hexagonal symmetry to minimize nearest neighbor coupling. Signal-to-noise ratio (SNR) and noise amplification for parallel imaging (G-factor) were evaluated in phantom and volunteer experiments. These results were compared to those of commercially available 24-channel and 32-channel coils in routine use for cardiac imaging. The in vivo measurements with the 128-channel coil resulted in SNR gains compared to the 24-channel coil (up to 2.2-fold in the apex). The 128- and 32-channel coils showed similar SNR in the heart, likely dominated by the similar element diameters of these coils. The maximum G-factor values were up to seven times better for a seven-fold acceleration factor (R = 7) compared to the 24-channel coil and up to two-fold improved compared to the 32-channel coil. The ability of the 128-channel coil to facilitate highly accelerated cardiac imaging was demonstrated in four volunteers using acceleration factors up to seven-fold (R = 7) in a single spatial dimension.

Schmitt, Melanie; Potthast, Andreas; Sosnovik, David E.; Polimeni, Jonathan R.; Wiggins, Graham C.; Triantafyllou, Christina; Wald, Lawrence L.

2008-01-01

306

Asymptomatic choroid plexus cysts in the lateral ventricles: an incidental finding on diffusion-weighted MRI  

Microsoft Academic Search

We assessed the role of diffusion-weighted imaging (DWI) in the detection of choroid plexus cysts. We reviewed more than 1000 patients who had undergone MRI in a 1-year period. We reviewed echo-planar DWI with b=1000 s\\/mm2, acquired at 1.0 tesla, for any difference in signal intensity which might indicate choroid plexus cysts. On conventional images, all cystic lesions were isointense

B. Cakir; H. Karakas; E. Unlu; N. Tuncbilek

2002-01-01

307

Automatic Brachytherapy Seed Placement Under MRI Guidance  

PubMed Central

The paper presents a robotic method of performing low dose rate prostate brachytherapy under magnetic resonance imaging (MRI) guidance. The design and operation of a fully automated MR compatible seed injector is presented. This is used with the MrBot robot for transperineal percutaneous prostate access. A new image-registration marker and algorithms are also presented. The system is integrated and tested with a 3T MRI scanner. Tests compare three different registration methods, assess the precision of performing automated seed deployment, and use the seeds to assess the accuracy of needle targeting under image guidance. Under the ideal conditions of the in vitro experiments, results show outstanding image-guided needle and seed placement accuracy.

Patriciu, Alexandru; Petrisor, Doru; Muntener, Michael; Mazilu, Dumitru; Schar, Michael; Stoianovici, Dan

2011-01-01

308

Physics of MRI: a primer.  

PubMed

This article is based on an introductory lecture given for the past many years during the "MR Physics and Techniques for Clinicians" course at the Annual Meeting of the ISMRM. This introduction is not intended to be a comprehensive overview of the field, as the subject of magnetic resonance imaging (MRI) physics is large and complex. Rather, it is intended to lay a conceptual foundation by which magnetic resonance image formation can be understood from an intuitive perspective. The presentation is nonmathematical, relying on simple models that take the reader progressively from the basic spin physics of nuclei, through descriptions of how the magnetic resonance signal is generated and detected in an MRI scanner, the foundations of nuclear magnetic resonance (NMR) relaxation, and a discussion of the Fourier transform and its relation to MR image formation. The article continues with a discussion of how magnetic field gradients are used to facilitate spatial encoding and concludes with a development of basic pulse sequences and the factors defining image contrast. PMID:22499279

Plewes, Donald B; Kucharczyk, Walter

2012-05-01

309

Play the MRI Game  

MedlinePLUS

... about the Nobel Prize Alfred Nobel's Life and Work Teachers' Questionnaire MRI Play MRI the Magnetic Miracle Game About the game In the MRI imaging technique, strong magnets and radio waves are used for getting images of inner ...

310

Backscatter body scanners – A strip search by other means  

Microsoft Academic Search

Backscatter body scanners have only recently been deployed at airports across the US and used as an optional alternative to patdowns – the open hand form of body search. This paper will essentially outline the statutory law and case-law of special relevance in the US to backscatter body scanners and determine the deficiencies and dilemmas of the legal framework with

Demetrius Klitou

2008-01-01

311

Linearization of electrostatically actuated surface micromachined 2-D optical scanner  

Microsoft Academic Search

This paper presents an effective method of linearizing the electrostatic transfer characteristics of micromachined two-dimensional (2-D) scanners. The orthogonal scan angles of surface micromachined polysilicon scanner are controlled by using quadrant electrodes for electrostatic actuation. By using a pair of differential voltages over a bias voltage, we could improve the distortion of projected images from 72% to only 13%. A

Hiroshi Toshiyoshi; Wibool Piyawattanametha; Cheng-Ta Chan; Ming C. Wu

2001-01-01

312

Design of a compact 3D laser scanner  

Microsoft Academic Search

A design study for a compact 3D scanner, called Coplan, is presented. The Coplan is intended to be used for high speed, in-line coplanarity and shape measurement of electronic components, like Ball Grid Arrays and Surface Mount Devices. The scanner should have a scan length of at least 2 inches and a resolution of 5 micrometers in all 3 dimensions.

Mark Geusen; Willem D. van Amstel; Stefan M. Baeumer; Jef L. Horijon

1999-01-01

313

ENGINEERING AND ENVIRONMENTAL APPLICATIONS OF LASER SCANNER TECHNIQUES  

Microsoft Academic Search

ABSTRACTS: The recent introduction of laser scanning devices has led to a set of new surveying products for the field of civil engineering and environmental analysis. The laser scanner is an instrument that permits one to acquire irregular point clouds of land areas, rivers and infrastructures in a fast and cheap way. The use of raw laser scanner data requires

Leandro Bornaz; Andrea Lingua; Fulvio Rinaudo

314

21. SITE BUILDING 002 SCANNER BUILDING LOOKING AT ...  

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

21. SITE BUILDING 002 - SCANNER BUILDING - LOOKING AT DISC STORAGE SYSTEMS A AND B (A OR B ARE REDUNDANT SYSTEMS), ONE MAINFRAME COMPUTER ON LINE, ONE ON STANDBY WITH STORAGE TAPE, ONE ON STANDBY WITHOUT TAPE INSTALLED. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

315

20. SITE BUILDING 002 SCANNER BUILDING IN COMPUTER ...  

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

20. SITE BUILDING 002 - SCANNER BUILDING - IN COMPUTER ROOM LOOKING AT "CONSOLIDATED MAINTENANCE OPERATIONS CENTER" JOB AREA AND OPERATION WORK CENTER. TASKS INCLUDE RADAR MAINTENANCE, COMPUTER MAINTENANCE, CYBER COMPUTER MAINTENANCE AND RELATED ACTIVITIES. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

316

UV Scanner DOAS Data Retrieved Using A Modelled Reference Spectrum  

Microsoft Academic Search

The difficulty of applying a real-time measured reference spectrum represents the main issue while using automatic Differential Optical Absorption Spectroscopy (DOAS) UV-Scanner networks for monitoring active volcanoes. Here we present the performance of a DOAS retrieval using a modelled reference spectrum derived from a high- resolution solar spectrum. Data analyzed were collected by the five UV scanners installed on Mt.

G. G. Salerno; M. Burton; T. Caltabiano; D. Randazzo; N. Bruno; V. Longo; C. Oppenheimer

2007-01-01

317

Quantitative Assay for Starch by Colorimetry Using a Desktop Scanner  

ERIC Educational Resources Information Center

|The procedure to produce standard curve for starch concentration measurement by image analysis using a color scanner and computer for data acquisition and color analysis is described. Color analysis is performed by a Visual Basic program that measures red, green, and blue (RGB) color intensities for pixels within the scanner image.|

Matthews, Kurt R.; Landmark, James D.; Stickle, Douglas F.

2004-01-01

318

10. SITE BUILDING 002 SCANNER BUILDING LOOKING AT ...  

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

10. SITE BUILDING 002 - SCANNER BUILDING - LOOKING AT SOUTHWEST CORNER "B" FACE AND "C" FACE ON WEST AND EVAPORATIVE COOLING TOWER AT NORTH. VIEW IS LOOKING NORTH 45° EAST. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

319

5. SITE BUILDING 002 SCANNER BUILDING AT "A" ...  

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

5. SITE BUILDING 002 - SCANNER BUILDING - AT "A" FACE (ON SOUTH SIDE) LOOKING DIRECTLY UP RADAR SYSTEM EMITTER/ANTENNA ARRAY FACE WITH 90MM STANDARD LENS. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

320

12. SITE BUILDING 002 SCANNER BUILDING MAIN ENTRANCE ...  

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

12. SITE BUILDING 002 - SCANNER BUILDING - MAIN ENTRANCE LOOKING AT MAIN ENTRANCE TO TECHNICAL FACILITY, GROUND LEVEL. VIEW IS LOOKING SOUTH 20° EAST. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

321

6. SITE BUILDING 002 SCANNER BUILDING AT "A" ...  

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

6. SITE BUILDING 002 - SCANNER BUILDING - AT "A" FACE (ON SOUTH SIDE) LOOKING DIRECTLY UP RADAR SYSTEM EMITTER/ANTENNA ARRAY FACE WITH 65MM WIDE ANGLE LENS. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

322

Wire Scanner Beam Profile Measurements: LANSCE Facility Beam Development  

Microsoft Academic Search

The Los Alamos Neutron Science Center (LANSCE) is replacing Wire Scanner (WS) beam profile measurement systems. Three beam development tests have taken place to test the new wire scanners under beam conditions. These beam development tests have integrated the WS actuator, cable plant, electronics processors and associated software and have used H⁻ beams of different beam energy and current conditions.

John D. Gilpatrick; Yuri K. Batygin; Fermin Gonzales; Michael E. Gruchalla; Vincent G. Kutac; Derwin Martinez; James Daniel Sedillo; Chandra Pillai; Sergio Rodriguez Esparza; Brian G. Smith

2012-01-01

323

Development of Security Scanner with High Portability and Usability  

Microsoft Academic Search

In this paper, we propose and develop a security scanner with high portability and usability. Recently, illegal access has been increasing explosively. Not only experts but also beginners need to cope up with vulnerability of a system promptly and properly. In such cases, a security scanner is an efficient tool to point out the vulnerability. However, for general users, most

Michitaka Yoshimoto; Bhed Bahadur Bista; Toyoo Takata

2005-01-01

324

29. SITE BUILDING 002 SCANNER BUILDING FLOOR 3A ...  

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

29. SITE BUILDING 002 - SCANNER BUILDING - FLOOR 3A ("A" FACE) AT SYSTEM LAYOUT GRID 17. GENERAL OBLIQUE VIEW OF "A" FACE INTERIOR SHOWING RADAR EMITTER/ANTENNA INTERFACE ELECTRONICS. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

325

Emittance Scanner for Intense Low-Energy Ion BEAMS.  

National Technical Information Service (NTIS)

An emittance scanner has been developed for use with low-energy H exp - ion beams to satisfy the following requirements: (1) angular resolution of +-1/2 mrad, (2) small errors from beam space charge, and (3) compact and simple design. The scanner consists...

P. W. Allison J. D. Sherman D. B. Holtkamp

1983-01-01

326

Laser excited confocal microscope fluorescence scanner and method  

DOEpatents

A fluorescent scanner is designed for scanning the fluorescence from a fluorescence labeled separated sample on a sample carrier. The scanner includes a confocal microscope for illuminating a predetermined volume of the sample carrier and/or receiving and processing fluorescence emissions from the volume to provide a display of the separated sample. 8 figs.

Mathies, R.A.; Peck, K.

1992-02-25

327

27. SITE BUILDING 002 SCANNER BUILDING OPERATIONS CENTER ...  

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

27. SITE BUILDING 002 - SCANNER BUILDING - OPERATIONS CENTER - MWOC MONITOR NO. 4 IN OPERATION AT 2002 ZULU, OCTOBER 26, 1999 CAPE COD, AS PAVE PAWS. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

328

Thermally actuated micro scanner for barcode reader applications  

Microsoft Academic Search

This paper presents a low-cost 1D thermally actuated silicon micro scanner developed for our industrial partner. It was designed and optimised for mass production. With a really simple and standard fabrication process we obtained a high yield (> 95%) and good reproducibility of the scanner characteristics: low resonance frequency, good shock resistance, low power consumption, easy control, large mechanical sweep

F. Khechana; H. van Lintel; J. L. Massieu; S. Ackley; P. Renaud

2005-01-01

329

34. SITE BUILDING 002 SCANNER BUILDING ROOM 105 ...  

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

34. SITE BUILDING 002 - SCANNER BUILDING - ROOM 105 - CHILLER ROOM, SHOWING SINGLE COMPRESSOR, LIQUID CHILLERS AND "CHILLED WATER RETURN", COOLING TOWER 'TOWER WATER RETURN" AND 'TOWER WATER SUPPLY" LINES. - Cape Cod Air Station, Technical Facility-Scanner Building & Power Plant, Massachusetts Military Reservation, Sandwich, Barnstable County, MA

330

Flux profile scanners for scattered high-energy electrons  

SciTech Connect

The paper describes the design and performance of flux integrating Cherenkov scanners with air-core reflecting light guides used in a high-energy, high-flux electron scattering experiment at the Stanford Linear Accelerator Center. The scanners were highly radiation resistant and provided a good signal to background ratio leading to very good spatial resolution of the scattered electron flux profile scans.

R.S Hicks; P. Decowski; C. Arroyo; M. Breuer; J. Celli; E. Chudakov; K.S. Kumar; M. Olson; G.A. Peterson; K. Pope; J. Ricci; J. Savage; P.A. Souder

2005-11-01

331

Study of PET scanner designs using clinical metrics to optimize the scanner axial FOV and crystal thickness  

NASA Astrophysics Data System (ADS)

The aim of this study is to understand the trade-off between crystal thickness and scanner axial field-of-view FOV (AFOV) for clinical PET imaging. Clinical scanner design has evolved towards 20-25 mm thick crystals and 16-22 cm long scanner AFOV, as well as time-of-flight (TOF) imaging. While Monte Carlo studies demonstrate that longer AFOV and thicker crystals will lead to higher scanner sensitivity, cost has prohibited the building of commercial scanners with >22 cm AFOV. In this study, we performed a series of system simulations to optimize the use of a given amount of crystal material by evaluating the impact on system sensitivity and noise equivalent counts (NEC), as well as image quality in terms of lesion detectability. We evaluated two crystal types (LSO and LaBr3) and fixed the total crystal volume used for each type (8.2 L of LSO and 17.1 L of LaBr3) while varying the crystal thickness and scanner AFOV. In addition, all imaging times were normalized so that the total scan time needed to scan a 100 cm long object with multiple bed positions was kept constant. Our results show that the highest NEC cm-1 in a 35 cm diameter ×70 cm long line source cylinder is achieved for an LSO scanner with 10 mm long crystals and AFOV of 36 cm, while for LaBr3 scanners, the highest NEC cm-1 is obtained with 20 mm long crystals and an AFOV of 38 cm. Lesion phantom simulations show that the best lesion detection performance is achieved in scanners with long AFOV (?36 cm) and using thin crystals (?10 mm of LSO and ?20 mm of LaBr3). This is due to a combination of improved NEC, as well as improved lesion contrast estimation due to better spatial resolution in thinner crystals. Alternatively, for lesion detection performance similar to that achieved in standard clinical scanner designs, the long AFOV scanners can be used to reduce the total scan time without increasing the amount of crystal used in the scanner. In addition, for LaBr3 based scanners, the reduced lesion contrast relative to LSO based scanners requires improved timing resolution and longer scan times in order to achieve lesion detectability similar to that achieved in an LSO scanner with similar NEC cm-1.

Surti, S.; Werner, M. E.; Karp, J. S.

2013-06-01

332

New Control Software for CEBAF Wire Scanners  

SciTech Connect

Wire scanners (WS) are the most popular beam profile measurement devices at Jefferson Lab. The WS for the CEBAF accelerator and beam extraction lines were created and supported by different user groups. As a result, they are not only implemented in different hardware standards (CAMAC and VME) but until recently also had different control functions that made them very difficult to use for accelerator beam diagnostic applications. To integrate all WS into one homogeneous system that is very easy to support and use for accelerator operations, new WS control software has been created. The software is implemented as a library of WS control and status modules. The control modules handle the WS hardware components and make their data available for beam diagnostic applications. The status modules monitor data communication channels between WS components and control computers and generate alarms in case of hardware failures. The paper presents the functionality of the new WS control software a nd its positive impact on accelerator operations.

Pavel Chevtsov

2005-03-01

333

Quadrupole resonance scanner for narcotics detection  

NASA Astrophysics Data System (ADS)

Interest in non-invasive, non-hazardous, bulk detection technologies for narcotics interdiction has risen over the last few years. As part of our continuing research and development programs in detection of narcotics and explosives using sensitive magnetic measuring devices, we present the first commercially available prototype Quadrupole Resonance (QR) scanner for narcotics detection. The portable narcotics detection system was designed in modular form such that a single QR base system could be easily used with a variety of custom detection heads. The QR system presented in this paper is suitable for scanning items up to 61 X 35 X 13 cm in size, and was designed to scan mail packages and briefcase-sized items for the presence of narcotics. System tests have shown that detection sensitivity is comparable that obtained in laboratory systems.

Shaw, Julian D.; Moeller, C. R.; Magnuson, Erik E.; Sheldon, A. G.

1994-10-01

334

JOURNAL CLUB: Shoulder MRI Utilization: Relationship of Physician MRI Equipment Ownership to Negative Study Frequency.  

PubMed

OBJECTIVE. The purpose of this article is to determine whether ownership of MRI equipment by ordering physicians influences the frequency of negative shoulder MRI scans. MATERIALS AND METHODS. A retrospective review was performed of 1140 consecutive shoulder MRI scans ordered by two separate referring physician groups serving the same geographic community. The first group (financially incentivized) owned the scanners used and received technical fees for their use. The second group (non-financially incentivized) did not own the scanners used and had no direct financial interest. All examinations were performed with identical protocols and were interpreted by a single radiologist group without financial interest in the imaging equipment used. The frequency of negative examinations and the number of abnormalities in each positive study was tabulated for each group. RESULTS. A total of 1140 shoulder MRI scans met inclusion criteria; 255 were negative (142 for the financially incentivized group and 113 for the non-financially incentivized group). There were 25.6% more negative scans in the financially incentivized group (p = 0.047). There was no statistically significant difference in the average number of lesions per positive scan (1.67 for the financially incentivized group and 1.71 for the non-financially incentivized group; p = 0.34). No statistically significant difference was found in the frequency of 19 of 20 examined lesions. CONCLUSION. Shoulder MRI examinations referred by physicians with a financial interest in the imaging equipment used were significantly more likely to be negative. Positive examinations exhibited no statistically significant difference in the number of lesions per scan or in the frequency of 19 of 20 lesion subtypes. This finding suggests a highly similar distribution and severity of disease among the two patient groups. PMID:23971453

Amrhein, Timothy J; Lungren, Matthew P; Paxton, Ben E; Srinivasan, Ramesh; Jung, Sin-Ho; Yu, Miao; Eastwood, James D; Kilani, Ramsey K

2013-09-01

335

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

336

The wakefields and loss factors in superconducting accelerating cavities for TESLA collider  

Microsoft Academic Search

The first stage of TTF superconducting electron linac is a in its final state of assembling. Many of superconducting accelerating cavities attained already the planned for collider accelerating fields of 25 MV\\/m. However the problem of cost reduction of TESLA accelerating system is still actual. The propositions concerning modifications in accelerating cavities were signalled at several TESLA Meetings and reported

E. Plawski

1999-01-01

337

A Forced-Attention Dichotic Listening fMRI Study on 113 Subjects  

ERIC Educational Resources Information Center

|We report fMRI and behavioral data from 113 subjects on attention and cognitive control using a variant of the classic dichotic listening paradigm with pairwise presentations of consonant-vowel syllables. The syllable stimuli were presented in a block-design while subjects were in the MR scanner. The subjects were instructed to pay attention to…

Kompus, Kristiina; Specht, Karsten; Ersland, Lars; Juvodden, Hilde T.; van Wageningen, Heidi; Hugdahl, Kenneth; Westerhausen, Rene

2012-01-01

338

A Forced-Attention Dichotic Listening fMRI Study on 113 Subjects  

ERIC Educational Resources Information Center

We report fMRI and behavioral data from 113 subjects on attention and cognitive control using a variant of the classic dichotic listening paradigm with pairwise presentations of consonant-vowel syllables. The syllable stimuli were presented in a block-design while subjects were in the MR scanner. The subjects were instructed to pay attention to…

Kompus, Kristiina; Specht, Karsten; Ersland, Lars; Juvodden, Hilde T.; van Wageningen, Heidi; Hugdahl, Kenneth; Westerhausen, Rene

2012-01-01

339

An evaluation of the use of passive shimming to improve frontal sensitivity in fMRI  

Microsoft Academic Search

The presence of the head in an MRI scanner leads to inhomogeneities in the magnetic field. These cause the dsusceptibility artifactsT of image distortion and signal dropout. In this paper, we evaluate a technique called passive shimming, which has the potential to reduce field inhomogeneities and the resultant artifacts. A piece of a magnetically active material (pyrolytic graphite) is held

Rhodri Cusack; Benedict Russell; Sylvia M. L. Cox; Claudia De Panfilis; Christian Schwarzbauer; Richard Ansorge

2005-01-01

340

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

341

TESLA test cell cryostat support post thermal and structural analysis  

SciTech Connect

TeV Superconducting Linear Accelerator (TESLA) cryostats consist of eight, 1-meter-long radio frequency (RF) cavity modules cryogenically connected in series with one focusing quadrupole. Each module contains one, 9-cell superconducting RF cavity operating at 1.3 GHz in a 1.8K helium bath. Individual modules are self-contained in the that they have their own input couplers, high order mode couplers, and tuning mechanisms. Services common to the entire cryostat consist of 70K and 4.5K thermal radiation shields, shield supply and return lines, a 1.8K helium supply line, and a gas helium return pipe. All cavity modules, the quadrupole, and cryogenic seances are contained in a single 12-meter-long vacuum vessel. The goal of the present work on TESLA is the successful fabrication and test of four complete cryostat assemblies. These cryostats will be installed in a string cooled to operating temperature, and powered. This test will address problems which may arise when modules are installed in a tunnel environment It will also permit testing of the basic cooling concepts, measurement of static heat losses, and measurement of the RF performance of all cavities.

Nicol, T.H.

1992-08-15

342

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

343

Multiple-echo diffusion tensor acquisition technique (MEDITATE) on a 3T clinical scanner.  

PubMed

This article describes the concepts and implementation of an MRI method, the multiple-echo diffusion tensor acquisition technique (MEDITATE), which is capable of acquiring apparent diffusion tensor maps in two scans on a 3T clinical scanner. In each MEDITATE scan, a set of RF pulses generates multiple echoes, the amplitudes of which are diffusion weighted in both magnitude and direction by a pattern of diffusion gradients. As a result, two scans acquired with different diffusion weighting strengths suffice for accurate estimation of diffusion tensor imaging (DTI) parameters. The MEDITATE variation presented here expands previous MEDITATE approaches to adapt to the clinical scanner platform, such as exploiting longitudinal magnetization storage to reduce T2 weighting. Fully segmented multi-shot Cartesian encoding is used for image encoding. MEDITATE was tested on isotropic (agar gel), anisotropic diffusion phantoms (asparagus) and in vivo skeletal muscle in healthy volunteers with cardiac gating. Comparisons of accuracy were performed with standard twice-refocused spin echo (TRSE) DTI in each case and good quantitative agreement was found between diffusion eigenvalues, mean diffusivity and fractional anisotropy derived from TRSE DTI and from the MEDITATE sequence. Orientation patterns were correctly reproduced in both isotropic and anisotropic phantoms, and approximately for in vivo imaging. This illustrates that the MEDITATE method of compressed diffusion encoding is feasible on the clinical scanner platform. With future development and employment of appropriate view-sharing image encoding, this technique may be used in clinical applications requiring time-sensitive acquisition of DTI parameters such as dynamical DTI in muscle. Copyright © 2013 John Wiley & Sons, Ltd. PMID:23828606

Baete, Steven H; Cho, Gene; Sigmund, Eric E

2013-07-05

344

Model-based scanner tuning for process optimization  

NASA Astrophysics Data System (ADS)

Given the continually decreasing k1 factor and process latitude in advanced technology nodes, it is important to fully understand and control the variables that impact imaging behavior in the lithography process. In this joint work between TSMC and ASML, we use model-based simulations to characterize and predict the imaging effects of these variables and to fine-tune the scanner settings based on such information in order to achieve optimal printing results on a perreticle basis. The scanner modeling makes use of detailed scanner characteristics as well as wafer CD measurements for accurate model construction. Simulations based on the calibrated model are subsequently used to predict the wafer impact of changes in tunable scanner parameters for all critical patterns in the product. The critical patterns can be identified beforehand, either experimentally on wafer, mask or through model simulations. A set of optimized scanner setting offsets, known as a "scanner tuning recipe" is generated to improve the imaging behavior for the critical patterns. We have demonstrated the efficacy of this methodology for multiple-use cases with selected ASML scanners and TSMC processes and will share the achieved improvements on defect reduction and yield improvements.

Chien, Tsung-Chih; Shih, C. Y.; Peng, R. C.; Liu, H. H.; Chen, Y. C.; Lee, H. J.; Lin, John; Chang, K. W.; Wu, C. M.; Hung, W. H.; Lee, Tommy; Wu, H. C.; Xie, X.; Shao, W. J.; Chang, C. H.; Aldana, R.; Cao, Y.; Goossens, R. J. G.; Hsieh, Simon

2009-12-01

345

Clinical applications of 7 T MRI in the brain.  

PubMed

This review illustrates current applications and possible future directions of 7 Tesla (7 T) Magnetic Resonance Imaging (MRI) in the field of brain MRI, in clinical studies as well as clinical practice. With its higher signal-to-noise (SNR) and contrast-to-noise ratio (CNR) compared to lower field strengths, high resolution, contrast-rich images can be obtained of diverse pathologies, like multiple sclerosis (MS), brain tumours, aging-related changes and cerebrovascular diseases. In some of these diseases, additional pathophysiological information can be gained compared to lower field strengths. Because of clear depiction of small anatomical details, and higher lesion conspicuousness, earlier diagnosis and start of treatment of brain diseases may become possible. Furthermore, additional insight into the pathogenesis of brain diseases obtained with 7 T MRI could be the basis for new treatment developments. However, imaging at high field comes with several limitations, like inhomogeneous transmit fields, a higher specific absorption rate (SAR) and, currently, extensive contraindications for patient scanning. Future studies will be aimed at assessing the advantages and disadvantages of 7 T MRI over lower field strengths in light of clinical applications, specifically the additional diagnostic and prognostic value of 7 T MRI. PMID:21937178

van der Kolk, Anja G; Hendrikse, Jeroen; Zwanenburg, Jaco J M; Visser, Fredy; Luijten, Peter R

2011-09-19

346

Handheld laser scanner automatic registration based on random coding  

NASA Astrophysics Data System (ADS)

Current research on Laser Scanner often focuses mainly on the static measurement. Little use has been made of dynamic measurement, that are appropriate for more problems and situations. In particular, traditional Laser Scanner must Keep stable to scan and measure coordinate transformation parameters between different station. In order to make the scanning measurement intelligently and rapidly, in this paper ,we developed a new registration algorithm for handleheld laser scanner based on the positon of target, which realize the dynamic measurement of handheld laser scanner without any more complex work. the double camera on laser scanner can take photograph of the artificial target points to get the three-dimensional coordinates, this points is designed by random coding. And then, a set of matched points is found from control points to realize the orientation of scanner by the least-square common points transformation. After that the double camera can directly measure the laser point cloud in the surface of object and get the point cloud data in an unified coordinate system. There are three major contributions in the paper. Firstly, a laser scanner based on binocular vision is designed with double camera and one laser head. By those, the real-time orientation of laser scanner is realized and the efficiency is improved. Secondly, the coding marker is introduced to solve the data matching, a random coding method is proposed. Compared with other coding methods,the marker with this method is simple to match and can avoid the shading for the object. Finally, a recognition method of coding maker is proposed, with the use of the distance recognition, it is more efficient. The method present here can be used widely in any measurement from small to huge obiect, such as vehicle, airplane which strengthen its intelligence and efficiency. The results of experiments and theory analzing demonstrate that proposed method could realize the dynamic measurement of handheld laser scanner. Theory analysis and experiment shows the method is reasonable and efficient.

He, Lei; Yu, Chun-Ping; Wang, Li

2011-06-01

347

Small animal simultaneous PET/MRI: initial experiences in a 9.4T microMRI  

SciTech Connect

We developed a non-magnetic positron-emission tomography (PET) device based on the rat conscious animal PET that operates in a small-animal magnetic resonance imaging (MRI) scanner, thereby enabling us to carry out simultaneous PET/MRI studies. The PET detector comprises 12 detector blocks, each being a 4 x 8 array of lutetium oxyorthosilicate crystals (2.22 x 2.22 x 5 mm{sup 3}) coupled to a matching non-magnetic avalanche photodiode array. The detector blocks, housed in a plastic case, form a 38 mm inner diameter ring with an 18 mm axial extent. Custom-built MRI coils fit inside the positron-emission tomography (PET) device, operating in transceiver mode. The PET insert is integrated with a Bruker 9.4 T 210 mm clear-bore diameter MRI scanner. We acquired simultaneous PET/MR images of phantoms, of in vivo rat brain, and of cardiac-gated mouse heart using [{sup 11}C]raclopride and 2-deoxy-2-[{sup 18}F]fluoro-d-glucose PET radiotracers. There was minor interference between the PET electronics and the MRI during simultaneous operation, and small effects on the signal-to-noise ratio in the MR images in the presence of the PET, but no noticeable visual artifacts. Gradient echo and high-duty-cycle spin echo radio frequency (RF) pulses resulted in a 7% and a 28% loss in PET counts, respectively, due to high PET counts during the RF pulses that had to be gated out. The calibration of the activity concentration of PET data during MR pulsing is reproducible within less than 6%. Our initial results demonstrate the feasibility of performing simultaneous PET and MRI studies in adult rats and mice using the same PET insert in a small-bore 9.4 T MRI.

Maramraju, S.H.; Schlyer, D.; Maramraju, S.H.; Smith, S.D.; Junnarkar, S.S.; Schulz, D.; Stoll, S.; Ravindranath, B.; Purschke, M.L.; Rescia, S.; Southekal, S.; Pratte, J.-F.; Vaska, P.; Woody, C.L.; Schlyer, D.J.

2011-03-25

348

Small animal simultaneous PET/MRI: initial experiences in a 9.4 T microMRI  

NASA Astrophysics Data System (ADS)

We developed a non-magnetic positron-emission tomography (PET) device based on the rat conscious animal PET that operates in a small-animal magnetic resonance imaging (MRI) scanner, thereby enabling us to carry out simultaneous PET/MRI studies. The PET detector comprises 12 detector blocks, each being a 4 × 8 array of lutetium oxyorthosilicate crystals (2.22 × 2.22 × 5 mm3) coupled to a matching non-magnetic avalanche photodiode array. The detector blocks, housed in a plastic case, form a 38 mm inner diameter ring with an 18 mm axial extent. Custom-built MRI coils fit inside the positron-emission tomography (PET) device, operating in transceiver mode. The PET insert is integrated with a Bruker 9.4 T 210 mm clear-bore diameter MRI scanner. We acquired simultaneous PET/MR images of phantoms, of in vivo rat brain, and of cardiac-gated mouse heart using [11C]raclopride and 2-deoxy-2-[18F]fluoro-d-glucose PET radiotracers. There was minor interference between the PET electronics and the MRI during simultaneous operation, and small effects on the signal-to-noise ratio in the MR images in the presence of the PET, but no noticeable visual artifacts. Gradient echo and high-duty-cycle spin echo radio frequency (RF) pulses resulted in a 7% and a 28% loss in PET counts, respectively, due to high PET counts during the RF pulses that had to be gated out. The calibration of the activity concentration of PET data during MR pulsing is reproducible within less than 6%. Our initial results demonstrate the feasibility of performing simultaneous PET and MRI studies in adult rats and mice using the same PET insert in a small-bore 9.4 T MRI.

Harsha Maramraju, Sri; Smith, S. David; Junnarkar, Sachin S.; Schulz, Daniela; Stoll, Sean; Ravindranath, Bosky; Purschke, Martin L.; Rescia, Sergio; Southekal, Sudeepti; Pratte, Jean-François; Vaska, Paul; Woody, Craig L.; Schlyer, David J.

2011-04-01

349

Overlay breakdown methodology on immersion scanner  

NASA Astrophysics Data System (ADS)

In the last years a flourishing number of techniques such as High Order Control or mappers have been proposed to improve overlay control. However a sustainable improvement requires sometimes understanding the underlying causes of the overlay limiting factors in order to remove them when possible or at least to keep them under control. Root cause finding for overlay error is a tough task due the very high number of influencing parameters and the interaction of the usage conditions. This paper presents a breakdown methodology to deal with this complexity and to find the contributors of overlay error variation. We use a Partial Least Squares (PLS) algorithm to isolate the key contributors for correctable terms and a field-to-field linear regression technique to highlight the main causes of residuals. We present a study carried out on 45nm CMOS contact-gate overlay over 687 production wafers exposed in an ASML TWINSCAN XT:1700i Immersion scanner. We present the results of the correlations with the 180 process and equipment variables used for this study. For each isolated contributor we propose an explanation of the underlying physical phenomenon and solutions.

Lam, Auguste; Pasqualini, Francois; de Caunes, Jean; Gatefait, Maxime

2010-03-01

350

Hydraulic flood modeling using laser scanner data  

NASA Astrophysics Data System (ADS)

This work analyzes the altimetrical data and the effects of resolution on flood modeling. Two different terrain representations were considered: regular square cells (GRID) and Triangulated Irregular Network (TIN). Altimetry was obtained from a particular terrain representation called Model Key Point (MKP): this is a DTM obtained from the elaboration of laser scanner data, and it is characterized by high number of points in the areas with more elevation differences, and by few points in flat areas. The accuracy of GRID and TIN data, obtained from MKP, was checked comparing them to the ground surveyed data. As well known hydrodynamic simulations need to represent the terrain morphology as input. Bi-dimensional hydraulic simulations were realized using different software and terrain representations obtained from MKP; the different results were compared afterwards. The use of bi-dimensional models to study flooded areas was increased with large diffusion of the high resolution Digital Terrain Model (DTM). However several models are not able to work easily and with reasonable simulation times when the DTM has a great deal of points. So some modifications of initial DTM are necessary and, in this work, the elaborations to reduce GID and TIN errors realized with Arcmap GIS are described too. The studied area is the Ionian coastal plane of the Basilicata region (Southern Italy): here anthropic elements such as levees, roads and channels strongly influence the water motion of the floodplain; thus a careful description of these elements is necessary in order to obtain the hydraulic risk evaluation.

Giosa, L.; Sole, A.; Nolè, L.

2009-04-01

351

Coronary imaging techniques with emphasis on CT and MRI.  

PubMed

Coronary artery imaging in children is challenging, with high demands both on temporal and spatial resolution due to high heart rates and smaller anatomy. Although invasive conventional coronary angiography remains the benchmark technique, over the past 10 years, CT and MRI have emerged in the field of coronary imaging. The choice of hardware is important. For CT, the minimum requirement is a 64-channel scanner. The temporal resolution of the scanner is most important for optimising image quality and minimising radiation dose. Manufacturers have developed several modes of electrocardiographic (ECG) triggering to facilitate dose reduction. Recent technical advances have opened new possibilities in MRI coronary imaging. As a non-ionising radiation technique, MRI is of great interest in paediatric imaging. It is currently recommended in centres with appropriate expertise for the screening of patients with suspected congenital coronary anomalies. However, MRI is still not feasible in infants. This review describes and discusses the technical requirements and the pros and cons of all three techniques. PMID:22127683

Lederlin, Mathieu; Thambo, Jean-Benoit; Latrabe, Valérie; Corneloup, Olivier; Cochet, Hubert; Montaudon, Michel; Laurent, François

2011-11-30

352

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

353

Design and Preliminary Accuracy Studies of an MRI-Guided Transrectal Prostate Intervention System  

PubMed Central

This paper reports a novel system for magnetic resonance imaging (MRI) guided transrectal prostate interventions, such as needle biopsy, fiducial marker placement, and therapy delivery. The system utilizes a hybrid tracking method, comprised of passive fiducial tracking for initial registration and subsequent incremental motion measurement along the degrees of freedom using fiber-optical encoders and mechanical scales. Targeting accuracy of the system is evaluated in prostate phantom experiments. Achieved targeting accuracy and procedure times were found to compare favorably with existing systems using passive and active tracking methods. Moreover, the portable design of the system using only standard MRI image sequences and minimal custom scanner interfacing allows the system to be easily used on different MRI scanners.

Krieger, Axel; Csoma, Csaba; Iordachita, Iulian I.; Guion, Peter; Singh, Anurag K.; Fichtinger, Gabor; Whitcomb, Louis L.

2012-01-01

354

Imaging for deep brain stimulation: The zona incerta at 7 Tesla  

PubMed Central

AIM: To evaluate different promising magnetic resonance imaging (MRI) methods at 7.0 Tesla (T) for the pre-stereotactic visualization of the zona incerta (ZI). METHODS: Two neuroradiologists qualitatively and quantitatively examined T2-turbo spin-echo (T2-TSE), T1-weighted gradient-echo, as well as FLASH2D-T2Star and susceptibility-weighted imaging (SWI) for the visualization of the ZI at 7.0 T MRI. Delineation and image quality for the ZI were independently examined using a 6-scale grading system. Inter-rater reliability using Cohen’s kappa coefficient (?) were assessed. Contrast-to-noise ratios (CNR), and signal-to-noise ratios (SNR) for the ZI were calculated for all sequences. Differences in delineation, SNR, and CNR between the sequences were statistically assessed using a paired t-test. For the anatomic validation the coronal FLASH2D-T2Star images were co-registered with a stereotactic atlas (Schaltenbrand-Wahren). RESULTS: The rostral part of the ZI (rZI) could easily be identified and was best and reliably visualized in the coronal FLASH2D-T2Star images. The caudal part was not definable in any of the sequences. No major artifacts in the rZI were observed in any of the scans. FLASH2D-T2Star and SWI imaging offered significant higher CNR values for the rZI compared to T2-TSE images (P > 0.05). The co-registration of the coronal FLASH2D-T2Star images with the stereotactic atlas schema (Schaltenbrand-Wahren) confirmed the correct localization of the ZI in all cases. CONCLUSION: FLASH2D-T2Star imaging (particularly coronal view) provides the reliable and currently optimal visualization of the rZI at 7.0 T. These results can facilitate a better and more precise targeting of the caudal part of the ZI than ever before.

Kerl, Hans U; Gerigk, Lars; Brockmann, Marc A; Huck, Sonia; Al-Zghloul, Mansour; Groden, Christoph; Hauser, Thomas; Nagel, Armin M; Nolte, Ingo S

2013-01-01

355

Superwide-angle coverage code-multiplexed optical scanner.  

PubMed

A superwide-angle coverage code-multiplexed optical scanner is presented that has the potential to provide 4 pi-sr coverage. As a proof-of-concept experiment, an angular scan range of 288 degrees for six randomly distributed beams is demonstrated. The proposed scanner achieves its superwide coverage by exploiting a combination of phase-encoded transmission and reflection holography within an in-line hologram recording-retrieval geometry. The basic scanner unit consists of one phase-only digital mode spatial light modulator for code entry (i.e., beam scan control) and a holographic material from which we obtained what we believe is the first-of-a-kind extremely wide coverage, low component count, high speed (e.g., microsecond domain), and large aperture (e.g., > 1-cm diameter) scanner. PMID:15143655

Riza, Nabeel A; Arain, Muzammil A

2004-05-01

356

21 CFR 892.1300 - Nuclear rectilinear 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 § 892.1300 Nuclear rectilinear scanner. (a) Identification. A nuclear...

2013-04-01

357

Towards MRI-guided linear accelerator control: gating on an MRI accelerator  

NASA Astrophysics Data System (ADS)

To boost the possibilities of image guidance in radiotherapy by providing images with superior soft-tissue contrast during treatment, we pursue diagnostic quality MRI functionality integrated with a linear accelerator. Large respiration-induced semi-periodic target excursions hamper treatment of cancer of the abdominal organs. Methods to compensate in real time for such motion are gating and tracking. These strategies are most effective in cases where anatomic motion can be visualized directly, which supports the use of an integrated MRI accelerator. We establish here an infrastructure needed to realize gated radiation delivery based on MR feedback and demonstrate its potential as a first step towards more advanced image guidance techniques. The position of a phantom subjected to one-dimensional periodic translation is tracked with the MR scanner. Real-time communication with the MR scanner and control of the radiation beam are established. Based on the time-resolved position of the phantom, gated radiation delivery to the phantom is realized. Dose distributions for dynamic delivery conditions with varying gating windows are recorded on gafchromic film. The similarity between dynamically and statically obtained dose profiles gradually increases as the gating window is decreased. With gating windows of 5 mm, we obtain sharp dose profiles. We validate our gating implementation by comparing measured dose profiles to theoretical profiles calculated using the knowledge of the imposed motion pattern. Excellent correspondence is observed. At the same time, we show that real-time on-line reconstruction of the accumulated dose can be performed using time-resolved target position information. This facilitates plan adaptation not only on a fraction-to-fraction scale but also during one fraction, which is especially valuable in highly accelerated treatment strategies. With the currently established framework and upcoming improvements to our prototype-integrated MRI accelerator, we will realize more intricate MRI-guided linear accelerator control in the near future.

Crijns, S. P. M.; Kok, J. G. M.; Lagendijk, J. J. W.; Raaymakers, B. W.

2011-08-01

358

Hepatic Iron Quantification on 3 Tesla (3 T) Magnetic Resonance (MR): Technical Challenges and Solutions  

PubMed Central

MR has become a reliable and noninvasive method of hepatic iron quantification. Currently, most of the hepatic iron quantification is performed on 1.5?T MR, and the biopsy measurements have been paired with R2 and R2* values for 1.5?T MR. As the use of 3?T MR scanners is steadily increasing in clinical practice, it has become important to evaluate the practicality of calculating iron burden at 3?T MR. Hepatic iron quantification on 3?T MR requires a better understanding of the process and more stringent technical considerations. The purpose of this work is to focus on the technical challenges in establishing a relationship between T2* values at 1.5?T MR and 3?T MR for hepatic iron concentration (HIC) and to develop an appropriately optimized MR protocol for the evaluation of T2* values in the liver at 3?T magnetic field strength. We studied 22 sickle cell patients using multiecho fast gradient-echo sequence (MFGRE) 3?T MR and compared the results with serum ferritin and liver biopsy results. Our study showed that the quantification of hepatic iron on 3?T MRI in sickle cell disease patients correlates well with clinical blood test results and biopsy results. 3?T MR liver iron quantification based on MFGRE can be used for hepatic iron quantification in transfused patients.

Anwar, Muhammad; Wood, John; Manwani, Deepa; Oyeku, Suzette O.; Peng, Qi

2013-01-01

359

Simultaneous Bilateral Hip Joint Imaging at 7 Tesla using Fast Transmit B1 Shimming Methods and Multichannel Transmission - A Feasibility Study  

PubMed Central

The objective of this study was to demonstrate the feasibility of simultaneous bilateral hip imaging at 7 Tesla. Hip joint MRI becomes clinically critical since recent advances have made hip arthroscopy an efficacious approach to treat a variety of early hip diseases. The success of these treatments requires a reliable and accurate diagnosis of intra-articular abnormalities at an early stage. Articular cartilage assessment is especially important to guide surgical decisions but is difficult to achieve with current MR methods. Because of gains in tissue contrast and spatial resolution reported at ultra high magnetic fields, there are strong expectations that imaging the hip joint at 7 Tesla will improve diagnostic accuracy. Furthermore, there is growing evidence that the majority of these hip abnormalities occur bilaterally, emphasizing the need for bilateral imaging. However, obtaining high quality images in the human torso, in particular of both hips simultaneously, must overcome a major challenge arising from the damped traveling wave behavior of radio-frequency waves at 7 Tesla that leads to severe inhomogeneities in transmit B1 (B1+) phase and magnitude, typically resulting in areas of low signal and low contrast, and consequently impairing use for clinical applications. In order to overcome this problem, a 16 channel stripline transceiver RF coil was used, together with a B1 shimming algorithm aiming at maximizing B1+ in six regions of interest over the hips which were identified on axial scout images. Our successful results demonstrate that this approach effectively reduces inhomogeneities observed before B1 shimming and provides high joint tissue contrast in both hips, while reducing the required RF power. Critical to this success was a fast, small flip angle B1+ calibration scan that permitted the computation of subject specific B1 shimming solutions, a necessary step to account for large spatial variations in B1+ phase observed in different subjects.

Ellermann, Jutta; Goerke, Ute; Morgan, Patrick; Ugurbil, Kamil; Tian, Jinfeng; Schmitter, Sebastian; Vaughan, Thomas; Van De Moortele, Pierre-Francois

2012-01-01

360

MSDS: An Experimental 24Channel Multispectral Scanner System  

Microsoft Academic Search

One of the more promising remote-sensing instruments that will be used in earth-resources survey programs is the multispectral scanner. It will collect both spectral and spatial information on the terrain scanned in a spatially registered manner. This paper describes one such scanner, which is being developed for a NASA C-130 earth-resources survey aircraft. It will be capable of simultaneously viewing

Eugene Zaitzeff; C. L. Korb; Charles Wilson

1971-01-01

361

47. View of "dry air inlets" to waveguides entering scanner ...  

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

47. View of "dry air inlets" to waveguides entering scanner building 105. Dried air is generated under pressure by Ingersoll-Rand dehumidified/dessicator and compressor system. View is at entrance from passageway that links into corner of scanner building. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

362

Commercial Use of UPC Scanner Data: Industry and Academic Perspectives  

Microsoft Academic Search

The authors report the findings from an exploratory investigation of the use of UPC scanner data in the consumer packaged goods industry in the U.S. The study examines the practitioner community's view of the use of scanner data and compares these views with academic research. Forty-one executives from ten data suppliers, packaged goods manufacturers, and consulting firms participated in wide-ranging,

Randolph E. Bucklin; Sunil Gupta

1999-01-01

363

Optical Scanner for Immunoassays With Up-Converting Phosphorescent Labels  

Microsoft Academic Search

A 2-D optical scanner was developed for the imaging and quantification of up-converting phosphor (UCP) labels in immunoassays. With resolution better than 500 mum, a scan rate of 0.4 mm\\/s, and a 1-2% coefficient of variation for repeatability, this scanner achieved a detection limit of fewer than 100 UCP particles in an 8.8 times 104 mum2 area and a dynamic

Janice J. Li; Amy L. Ouellette; Laurent Giovangrandi; David E. Cooper; Antonio J. Ricco; Gregory T. A. Kovacs

2008-01-01

364

Design, performance and production of the Fermilab TESLA RF input couplers  

SciTech Connect

The TeV Energy Superconducting Linear Accelerator (TESLA) requires as one of its technical components a radiofrequency (rf) input coupler that transfers 1.3 GHz rf energy from the rf distribution system to a nine-cell superconducting accelerating cavity operating at a temperature of 1.8 K. The input coupler design is driven by numerous design criteria, which result in a rather complicated implementation. The production of twelve input couplers for the TESLA Test Facility (TTF) is underway at Fermilab, with the first two couplers having been delivered late in 1995. This paper discusses the Fermilab TESLA rf input coupler design, recent test results, and production issues.

Champion, M.

1996-10-01

365

Operating nanoliter scale NMR microcoils in a 1 tesla field  

NASA Astrophysics Data System (ADS)

Microcoil probes enclosing sample volumes of 1.2, 3.3, 7.0, and 81 nanoliters are constructed as nuclear magnetic resonance (NMR) detectors for operation in a 1 tesla permanent magnet. The probes for the three smallest volumes utilize a novel auxiliary tuning inductor for which the design criteria are given. The signal-to-noise ratio (SNR) and line width of water samples are measured. Based on the measured DC resistance of the microcoils, together with the calculated radio frequency (RF) resistance of the tuning inductor, the SNR is calculated and shown to agree with the measured values. The details of the calculations indicate that the auxiliary inductor does not degrade the NMR probe performance. The diameter of the wire used to construct the microcoils is shown to affect the signal line widths.

McDowell, Andrew F.; Adolphi, Natalie L.

2007-09-01

366

Comparison of the TESLA, NLC and CLIC beam collimation performance  

SciTech Connect

This note describes studies performed in the framework of the Collimation Task Force organized to support the work of the International Linear Collider Technical Review Committee. The post-linac beam-collimation systems in the TESLA, JLC/NLC and CLIC linear-collider designs are compared using the same computer code under the same assumptions. Their performance is quantified in terms of beam-halo and synchrotron-radiation collimation efficiency. The performance of the current designs varies across projects, and does not always meet the original design goals. But these comparisons suggest that achieving the required performance in a future linear collider is feasible. The post-TRC plans of the Collimation Task Force are briefly outlined in closing.

Alexandr I Drozhdin et al.

2003-03-27

367

Report on the TESLA engineering study/review  

SciTech Connect

A team from Argonne National Lab, Cornell, Fermilab, Jefferson Lab, and SLAC has studied the TESLA TDR and its associated cost and manpower estimates, concentrating on the five largest cost sub-systems (Main Linac Modules, Main Linac RF Systems, Civil Engineering, Machine Infrastructure, and XFEL Incremental). These elements were concerned mainly with providing energy reach. We did not study the lower cost, but still technically challenging elements providing luminosity and physics capability, namely damping rings, beam delivery system, beam injection system, positron production, polarized beams, etc. The study did not attempt to validate the TDR cost estimates, but rather its purpose was to understand the technology and status of the large cost items, and the methodology by which their estimated cost was determined. In addition, topics of project oversight were studied.

C. Boffo et al.

2002-07-18

368

Towards a Hall effect magnetic tracking device for MRI.  

PubMed

This paper presents the first prototype of a magnetic tracking device for Magnetic Resonance Imaging. The unique relationship between the space coordinates of a MRI scanner bore and the magnetic field gradients used in MRI allows building a localization system based on an accurate measurement of these gradients. These gradients are measured thanks to a 3D Hall device with a footprint of only 50µm(2), integrated with its specific conditioning circuit in a low cost, low voltage 0.35µm CMOS process. The first experimental results show that a sub-millimeter localization is possible. It opens the way to the development of MRI compatible magnetic tracking systems integrable in a surgical tool. PMID:24110349

Schell, J-B; Kammerer, J-B; Hebrard, L; Breton, E; Gounot, D; Cuvillon, L; de Mathelin, M

2013-07-01

369

Voxel-based cortical thickness measurements in MRI  

PubMed Central

The thickness of the cerebral cortex can provide valuable information about normal and abnormal neuroanatomy. High resolution MRI together with powerful image processing techniques has made it possible to perform these measurements automatically over the whole brain. Here we present a method for automatically generating voxel-based cortical thickness (VBCT) maps. This technique results in maps where each voxel in the grey matter is assigned a thickness value. Sub-voxel measurements of thickness are possible using sub-sampling and interpolation of the image information. The method is applied to repeated MRI scans of a single subject from two MRI scanners to demonstrate its robustness and reproducibility. A simulated data set is used to show that small focal differences in thickness between two groups of subjects can be detected. We propose that the analysis of VBCT maps can provide results that are complementary to other anatomical analyses such as voxel-based morphometry.

Hutton, Chloe; De Vita, Enrico; Ashburner, John; Deichmann, Ralf; Turner, Robert

2008-01-01

370

Functional organization of activation patterns in children: Whole brain fMRI imaging during three different cognitive tasks  

Microsoft Academic Search

1.1. Patterns of brain activation were measured with whole brain echo-planar functional magnetic resonance imaging (fMRI) at 3.0 Tesla in healthy children (N = 6) and in one child with a left- hemisphere encephalomalacic lesion as sequellae from early stroke.2.2. Three cognitive tasks were used: auditory sentence comprehension, verb generation to line drawings, and mental rotation of alphanumeric stimuli.3.3. There

James R. Booth; Brian Macwhinney; Keith R. Thulborn; Kelley Sacco; James Voyvodic; Heidi M. Feldman

1999-01-01

371

Design and evaluation of a prototype volume CT scanner  

NASA Astrophysics Data System (ADS)

We designed, assembled and evaluated a prototype volume CT scanner (VCT) for the purpose of investigating various calibration methods and cone beam reconstruction algorithms as well as the potential clinical benefits of a high-resolution volume CT scanner. The new VCT is based on SIEMENS Sensation4 CT scanner. To achieve larger volume coverage and higher spatial resolution we replaced the prior 4-slices detector with a flat-panel detector. We also modified the prior x-ray tube to achieve a very small focus size by a smaller emitter and wider axial coverage by a larger anode angle. In addition the high-voltage generator was enhanced to support pulsed operation. Special measurement methods were elaborated and applied to measure the focus size, shape and position as well as the uniformity of the flat field x-ray exposure. The accuracy and stability of gantry rotation speed has been evaluated to decide for the most appropriate exposure trigger. New methods are applied to measure and calibrate the resulted x-ray geometry. One prototype VCT scanner is installed at a pre-clinical site to evaluate the application potential of the new VCT technology. The new volume scanner achieves unprecedented spatial resolution, slice sensitivity and spatial coverage. In a complementary paper we present the image quality, contrast resolution and dose issues associated with this scanner.

Popescu, Stefan; Stierstorfer, Karl; Flohr, Thomas; Suess, Christoph; Grasruck, Michael

2005-04-01

372

A stationary digital breast tomosynthesis scanner  

NASA Astrophysics Data System (ADS)

A prototype stationary digital breast tomosynthesis (s-DBT) system has been developed by retrofitting a Hologic Selenia Dimension rotating gantry tomosynthesis scanner with a spatially distributed carbon nanotube (CNT) x-ray source array. The goal is to improve the system spatial resolution by removing the x-ray tube motion induced focal spot blurring. The CNT x-ray source array comprises 31 individually addressable x-ray beams covering 30° angular span. Each x-ray beam has a minimum focal spot size of 0.64×0.61mm (full-width-at-half-maximum), a stationary W anode operating up to 50kVp, and 1mm thick Al filter. The flux from each beam is regulated and varied using dedicated control electronics. The maximum tube current is determined by the heat load of the stationary anode and depends on the energy, pulse width and the focal spot size used. Stable operation at 28kVp, 27mA tube current, 250msec pulse width and 38mA tube current, 183msec pulse width per exposure was achieved with extended lifetime. The standard ACR phantom was imaged and analyzed to evaluate the image quality. The actual scanning speed depends on the number of views and the readout time of the x-ray detector. With the present detector, 6 second scanning time at either 15 views or 31 views can be achieved at 100mAs total imaging dose with a detector readout time of 240msec.

Qian, Xin; Tucker, Andrew; Gidcumb, Emily; Lu, Jianping; Zhou, Otto; Spronk, Derrek; Sprenger, Frank; Zhang, Yiheng; Kennedy, Don; Farbizio, Tom; Jing, Zhenxue

2012-02-01

373

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

374

Fusion in fingerprint authentication: two finger types vs. two scanner types  

Microsoft Academic Search

This paper presents our study on fingerprint fusion in particular in three scenario sets: a) two fingers captured by the same scanner; b) the same finger captured by two different scanners; and c) two fingers both captured by two different scanners. As a test data set we use GUC100 multi-scanner fingerprint database which contains fingerprint images of all ten fingers

Davrondzhon Gafurov; Christoph Busch; Patrick Bours; Bian Yang

2011-01-01

375

MRI atlas of the human hypothalamus.  

PubMed

Gaining new insights into the anatomy of the human hypothalamus is crucial for the development of new treatment strategies involving functional stereotactic neurosurgery. Here, using anatomical comparisons between histology and magnetic resonance images of the human hypothalamus in the coronal plane, we show that discrete gray and white hypothalamic structures are consistently identifiable by MRI. Macroscopic and microscopic images were used to precisely annotate the MRI sequences realized in the coronal plane in twenty healthy volunteers. MRI was performed on a 1.5 T scanner, using a protocol including T1-weighted 3D fast field echo, T1-weighted inversion-recovery, turbo spin echo and T2-weighted 2D fast field echo imaging. For each gray matter structure as well as for white matter bundles, the different MRI sequences were analyzed in comparison to each other. The anterior commissure and the fornix were often identifiable, while the mammillothalamic tract was more difficult to spot. Qualitative analyses showed that MRI could also highlight finer structures such as the paraventricular nucleus, the ventromedial nucleus of the hypothalamus and the infundibular (arcuate) nucleus, brain nuclei that play key roles in the regulation of food intake and energy homeostasis. The posterior hypothalamic area, a target for deep brain stimulation in the treatment of cluster headaches, was readily identified, as was the lateral hypothalamic area, which similar to the aforementioned hypothalamic nuclei, could be a putative target for deep brain stimulation in the treatment of obesity. Finally, each of the identified structures was mapped to Montreal Neurological Institute (MNI) space. PMID:21777680

Baroncini, Marc; Jissendi, Patrice; Balland, Eglantine; Besson, Pierre; Pruvo, Jean-Pierre; Francke, Jean-Paul; Dewailly, Didier; Blond, Serge; Prevot, Vincent

2011-07-14

376

fMRI Brain-Computer Interface: A Tool for Neuroscientific Research and Treatment  

PubMed Central

Brain-computer interfaces based on functional magnetic resonance imaging (fMRI-BCI) allow volitional control of anatomically specific regions of the brain. Technological advancement in higher field MRI scanners, fast data acquisition sequences, preprocessing algorithms, and robust statistical analysis are anticipated to make fMRI-BCI more widely available and applicable. This noninvasive technique could potentially complement the traditional neuroscientific experimental methods by varying the activity of the neural substrates of a region of interest as an independent variable to study its effects on behavior. If the neurobiological basis of a disorder (e.g., chronic pain, motor diseases, psychopathy, social phobia, depression) is known in terms of abnormal activity in certain regions of the brain, fMRI-BCI can be targeted to modify activity in those regions with high specificity for treatment. In this paper, we review recent results of the application of fMRI-BCI to neuroscientific research and psychophysiological treatment.

Sitaram, Ranganatha; Caria, Andrea; Veit, Ralf; Gaber, Tilman; Rota, Giuseppina; Kuebler, Andrea; Birbaumer, Niels

2007-01-01

377

Experimental System Setup for HIFU under MRI for mouse experiments  

NASA Astrophysics Data System (ADS)

We describe an integrated system setup for HIFU and MRI thermometry for mouse experiments. The applications of such a system include MRI imaging and thermometry for evaluation and feedback during HIFU applications on mouse models of various diseases; and validation of temperature estimated by other methods, such as RF data. A 5 MHz geometrically focused (diameter of 16.1 mm, focal length 35 mm), MRI-compatible HIFU transducer is used, driven by a programmable signal generator and a power amplifier. The small animal MRI scanner has been programmed to acquire sequential phase information, which is used to determine frequency shift. Relative temperature rise is then calculated by proton resonance frequency (RPF) method. The current software development is done in C++ and Matlab. An integrated software is being developed to streamline the acquisition, analysis and visualization during HIFU delivery. Preliminary experiments have been performed using different phantoms. Performing HIFU (less than 100 watts) under MRI has had minimal interference for MRI data acquisition. The development is continuing for further characterizing and understanding the interference at the higher power level and accelerate data acquisition rate to achieve thermometry for a few frames per second. Further tissue experiments are under way with target of live mouse experiments. We present the overall design and discuss challenges encountered in the development of such system for experiments on mouse.

Long, Tao; Amin, Viren; Boska, Michael

2009-04-01

378

Multi-site characterization of an fMRI working memory paradigm: reliability of activation indices.  

PubMed

Neuroimaging studies are facilitated significantly when it is possible to recruit subjects and acquire data at multiple sites. However, the use of different scanners and acquisition protocols is a potential source of variability in multi-site data. In this work we present a multi-site study of the reliability of fMRI activation indices, where 10 healthy volunteers were scanned at 4 different sites while performing a working memory paradigm. Our results indicate that, even with different scanner manufacturers and field strengths, activation variability due to site differences is small compared to variability due to subject differences in this cognitive task, provided we choose an appropriate activation measure. PMID:20451631

Yendiki, Anastasia; Greve, Douglas N; Wallace, Stuart; Vangel, Mark; Bockholt, Jeremy; Mueller, Bryon A; Magnotta, Vince; Andreasen, Nancy; Manoach, Dara S; Gollub, Randy L

2010-05-05

379

Diagnostic benefits of presurgical fMRI in patients with brain tumours in the primary sensorimotor cortex  

Microsoft Academic Search

Objectives  Reliable imaging of eloquent tumour-adjacent brain areas is necessary for planning function-preserving neurosurgery. This\\u000a study evaluates the potential diagnostic benefits of presurgical functional magnetic resonance imaging (fMRI) in comparison\\u000a to a detailed analysis of morphological MRI data.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Standardised preoperative functional and structural neuroimaging was performed on 77 patients with rolandic mass lesions at\\u000a 1.5 Tesla. The central region of both

Martina Wengenroth; M. Blatow; J. Guenther; M. Akbar; V. M. Tronnier; C. Stippich

2011-01-01

380

Improved spatial resolution in PET scanners using sampling techniques  

PubMed Central

Increased focus towards improved detector spatial resolution in PET has led to the use of smaller crystals in some form of light sharing detector design. In this work we evaluate two sampling techniques that can be applied during calibrations for pixelated detector designs in order to improve the reconstructed spatial resolution. The inter-crystal positioning technique utilizes sub-sampling in the crystal flood map to better sample the Compton scatter events in the detector. The Compton scatter rejection technique, on the other hand, rejects those events that are located further from individual crystal centers in the flood map. We performed Monte Carlo simulations followed by measurements on two whole-body scanners for point source data. The simulations and measurements were performed for scanners using scintillators with Zeff ranging from 46.9 to 63 for LaBr3 and LYSO, respectively. Our results show that near the center of the scanner, inter-crystal positioning technique leads to a gain of about 0.5-mm in reconstructed spatial resolution (FWHM) for both scanner designs. In a small animal LYSO scanner the resolution improves from 1.9-mm to 1.6-mm with the inter-crystal technique. The Compton scatter rejection technique shows higher gains in spatial resolution but at the cost of reduction in scanner sensitivity. The inter-crystal positioning technique represents a modest acquisition software modification for an improvement in spatial resolution, but at a cost of potentially longer data correction and reconstruction times. The Compton scatter rejection technique, while also requiring a modest acquisition software change with no increased data correction and reconstruction times, will be useful in applications where the scanner sensitivity is very high and larger improvements in spatial resolution are desirable.

Surti, Suleman; Scheuermann, Ryan; Werner, Matthew E.; Karp, Joel S.

2009-01-01

381

Improved spatial resolution in PET scanners using sampling techniques.  

PubMed

Increased focus towards improved detector spatial resolution in PET has led to the use of smaller crystals in some form of light sharing detector design. In this work we evaluate two sampling techniques that can be applied during calibrations for pixelated detector designs in order to improve the reconstructed spatial resolution. The inter-crystal positioning technique utilizes sub-sampling in the crystal flood map to better sample the Compton scatter events in the detector. The Compton scatter rejection technique, on the other hand, rejects those events that are located further from individual crystal centers in the flood map. We performed Monte Carlo simulations followed by measurements on two whole-body scanners for point source data. The simulations and measurements were performed for scanners using scintillators with Z(eff) ranging from 46.9 to 63 for LaBr(3) and LYSO, respectively. Our results show that near the center of the scanner, inter-crystal positioning technique leads to a gain of about 0.5-mm in reconstructed spatial resolution (FWHM) for both scanner designs. In a small animal LYSO scanner the resolution improves from 1.9-mm to 1.6-mm with the inter-crystal technique. The Compton scatter rejection technique shows higher gains in spatial resolution but at the cost of reduction in scanner sensitivity. The inter-crystal positioning technique represents a modest acquisition software modification for an improvement in spatial resolution, but at a cost of potentially longer data correction and reconstruction times. The Compton scatter rejection technique, while also requiring a modest acquisition software change with no increased data correction and reconstruction times, will be useful in applications where the scanner sensitivity is very high and larger improvements in spatial resolution are desirable. PMID:19779586

Surti, Suleman; Scheuermann, Ryan; Werner, Matthew E; Karp, Joel S

2009-06-01

382

Development of Free-Electron x-Ray Lasers on the TESLA Test Accelerator (DESY, Germany)  

Microsoft Academic Search

The program for developing free-electron x-ray lasers at TESLA started in 1994. The plan is to use the TESLA test accelerator to develop an x-ray laser with minimum wavelength 0.1–6 nm. The first phase of the project was successfully completed in 2001. At saturation, the laser produces ultrashort 30–100 fsec, gigawatt, radiation pulses. The wavelength can be tuned smoothly over

M. V. Yurkov

2003-01-01

383

Low frequency AC losses in multi filamentary superconductors up to 15 Tesla  

Microsoft Academic Search

Low frequency (1 Hz) ac losses were measured in a variety of A15 superconducting wires having different fiber geometries. Field modulations ofless than or equal to 1 tesla were superimposed on a fixed background field up to 15 tesla. Losses were measured for NbâSn in continuous fiber, modified jelly-roll, In Situ, and powder metallurgy processed materials, and for NbâAl powder

T. Orlando; C. Braun; S. Foner; B. Schwartz; A. Zieba

1983-01-01

384

Automatic hippocampus segmentation of 7.0Tesla MR images by combining multiple atlases and auto-context models.  

PubMed

In many neuroscience and clinical studies, accurate measurement of hippocampus is very important to reveal the inter-subject anatomical differences or the subtle intra-subject longitudinal changes due to aging or dementia. Although many automatic segmentation methods have been developed, their performances are still challenged by the poor image contrast of hippocampus in the MR images acquired especially from 1.5 or 3.0Tesla (T) scanners. With the recent advance of imaging technology, 7.0T scanner provides much higher image contrast and resolution for hippocampus study. However, the previous methods developed for segmentation of hippocampus from 1.5T or 3.0T images do not work for the 7.0T images, due to different levels of imaging contrast and texture information. In this paper, we present a learning-based algorithm for automatic segmentation of hippocampi from 7.0T images, by taking advantages of the state-of-the-art multi-atlas framework and also the auto-context model (ACM). Specifically, ACM is performed in each atlas domain to iteratively construct sequences of location-adaptive classifiers by integrating both image appearance and local context features. Due to the plenty texture information in 7.0T images, more advanced texture features are also extracted and incorporated into the ACM during the training stage. Then, under the multi-atlas segmentation framework, multiple sequences of ACM-based classifiers are trained for all atlases to incorporate the anatomical variability. In the application stage, for a new image, its hippocampus segmentation can be achieved by fusing the labeling results from all atlases, each of which is obtained by applying the atlas-specific ACM-based classifiers. Experimental results on twenty 7.0T images with the voxel size of 0.35×0.35×0.35mm(3) show very promising hippocampus segmentations (in terms of Dice overlap ratio 89.1±0.020), indicating high applicability for the future clinical and neuroscience studies. PMID:23769921

Kim, Minjeong; Wu, Guorong; Li, Wei; Wang, Li; Son, Young-Don; Cho, Zang-Hee; Shen, Dinggang

2013-06-11

385

Canalis basilaris medianus: MRI  

Microsoft Academic Search

We report the MRI appearances of an developmental anatomical variant of the basiocciput, with neuroimaging findings (CT and\\u000a MRI). Such variants are commonly asymptomatic, but may be associated with episodes of meningitis.

C. Jacquemin; T. M. Bosley; M. al Saleh; P. Mullaney

2000-01-01

386

Event related fMRI studies of voluntary and inhibited eye blinking using a time marker of EOG  

Microsoft Academic Search

Electrooculogram (EOG) measurements, along with infrared measurements, are commonly used to record eye blinking during functional magnetic resonance imaging (fMRI). We report herein, on the use of EOG in measuring voluntary and inhibited eye blinking during echo planar imaging (EPI) in an MR scanner. The inhibited eye blinking occurred during the period, in which subjects were requested not to blink

Jun-Young Chung; Hyo Woon Yoon; Myung-Sung Song

2006-01-01

387

A comprehensive testing protocol for MRI neuroanatomical segmentation techniques: Evaluation of a novel lateral ventricle segmentation method  

Microsoft Academic Search

Although a wide range of approaches have been developed to automatically assess the volume of brain regions from MRI, the reproducibility of these algorithms across different scanners and pulse sequences, their accuracy in different clinical populations and sensitivity to real changes in brain volume have not always been comprehensively examined. Firstly we present a comprehensive testing protocol which comprises 312

Matthew J. Kempton; Tracy S. A. Underwood; Simon Brunton; Floris Stylios; Anne Schmechtig; Ulrich Ettinger; Marcus S. Smith; Simon Lovestone; William R. Crum; Sophia Frangou; Steven C. R. Williams; Andrew Simmons

2011-01-01

388

Team one (GA/MCA) effort of the DOE 12 Tesla Coil Development Program. 12 Tesla ETF toroidal field coil helium bath cooled NbTi alloy concept  

SciTech Connect

This report presents the conceptual design of an ETF compatible toroidal field coil, employing helium bath cooled NbTi alloy conductor. The ten TF-coil array generates a peak field of 11-1/2 tesla at 2.87 m radius, corresponding to a major axis field of 6.1 tesla. The 10 kA conductor is an uninsulated, unsoldered Rutherford cable, employing NbTiTa ally as developed in Phase I of this effort. The conductor is encased within a four element frame of stainless steel strips to provide hoop and bearing load support.

Not Available

1980-07-01

389

Evaluation of medial meniscus tears and meniscal stability: weight-bearing MRI vs arthroscopy.  

PubMed

To assess the role of dedicated low-field standard and weight-bearing MRI in the evaluation of stable or unstable tears of medial meniscus in comparison with arthroscopy. Our series included 1750 knee MRI scans performed with a high-field MRI scanner from July 2010 to August 2011. We retrospectively reviewed and analyzed 20 MRI exams of normal knee and 57 MRI exams of knee with clinical evidence of tears of the medial meniscus. In the same session, after conventional 1.5T and "dedicated" 0.25T supine MRI exam, the patients underwent weight-bearing examination with the same dedicated MRI unit. In all cases sagittal and coronal PD-W were used. All patients underwent arthroscopy 18-25 days after the weight-bearing MRI. In the first group, no statistically significant anatomical modifications of shape, intensity and position of the medial meniscus between standard 1.5T, dedicated supine and upright MRI were observed. In group A, the images acquired in the supine position (dedicated and 1.5T MRI) documented in 21 cases a traumatic tear (group 2A) and in 36 cases a degenerative tear (group 2B). In group 2A, weight-bearing MRI showed presence of unstable tear a degenerative unstable meniscal tear only in 19 out of 36 cases. In group 2B, weight-bearing MRI showed only in 9 out 21 cases. Arthroscopy confirmed weight-bearing MRI diagnosis in all cases. This new approach to meniscus pathology gives an important contribution to a better management of a diagnostic-therapeutic approach in which standard MRI has not played a key role, so far. PMID:23199751

Barile, Antonio; Conti, Laura; Lanni, Giuseppe; Calvisi, Vittorio; Masciocchi, Carlo

2012-11-28

390

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

391

Dobutamine stress cardiovascular magnetic resonance at 3 Tesla  

PubMed Central

Purpose The assessment of inducible wall motion abnormalities during high-dose dobutamine-stress cardiovascular magnetic resonance (DCMR) is well established for the identification of myocardial ischemia at 1.5 Tesla. Its feasibility at higher field strengths has not been reported. The present study was performed to prospectively determine the feasibility and diagnostic accuracy of DCMR at 3 Tesla for depicting hemodynamically significant coronary artery stenosis (? 50% diameter stenosis) in patients with suspected or known coronary artery disease (CAD). Materials and methods Thirty consecutive patients (6 women) (66 ± 9.3 years) were scheduled for DCMR between January and May 2007 for detection of coronary artery disease. Patients were examined with a Philips Achieva 3 Tesla system (Philips Healthcare, Best, The Netherlands), using a spoiled gradient echo cine sequence. Technical parameters were: spatial resolution 2 × 2 × 8 mm3, 30 heart phases, spoiled gradient echo TR/TE: 4.5/2.6 msec, flip angle 15°. Images were acquired at rest and stress in accordance with a standardized high-dose dobutamine-atropine protocol during short breath-holds in three short and three long-axis views. Dobutamine was administered using a standard protocol (10 ?g increments every 3 minutes up to 40 ?g dobutamine/kg body weight/minute plus atropine if required to reach target heart rate). The study protocol included administration of 0.1 mmol/kg/body weight Gd-DTPA before the cine images at rest were acquired to improve the image quality. The examination was terminated if new or worsening wall-motion abnormalities or chest pain occurred or when > 85% of age-predicted maximum heart rate was reached. Myocardial ischemia was defined as new onset of wall-motion abnormality in at least one segment. In addition, late gadolinium enhancement (LGE) was performed. Images were evaluated by two blinded readers. Diagnostic accuracy was determined with coronary angiography as the reference standard. Image quality and wall-motion at rest and maximum stress level were evaluated using a four-point scale. Results In 27 patients DCMR was performed successfully, no patient had to be excluded due to insufficient image quality. Twenty-two patients were examined by coronary angiography, which depicted significant stenosis in 68.2% of the patients. Patient-based sensitivity and specificity were 80.0% and 85.7% respectively and accuracy was 81.8%. Interobserver variability for assessment of wall motion abnormalities was 88% (? = 0.760; p < 0.0001). Negative and positive predictive values were 66.7% and 92.3%, respectively. No significant differences in average image quality at rest versus stress for short or long-axis cine images were found. Conclusion High-dose DCMR at 3T is feasible and an accurate method to depict significant coronary artery stenosis in patients with suspected or known CAD.

Kelle, S; Hamdan, A; Schnackenburg, B; Kohler, U; Klein, C; Nagel, E; Fleck, E

2008-01-01

392

An ultra fast electron beam x-ray tomography scanner  

NASA Astrophysics Data System (ADS)

This paper introduces the design of an ultra fast x-ray tomography scanner based on electron beam technology. The scanner has been developed for two-phase flow studies where frame rates of 1 kHz and higher are required. Its functional principle is similar to that of the electron beam x-ray CT scanners used in cardiac imaging. Thus, the scanner comprises an electron beam generator with a fast beam deflection unit, a semicircular x-ray production target made of tungsten alloy and a circular x-ray detector consisting of 240 CZT elements with 1.5 mm × 1.5 mm × 1.5 mm size each. The design is optimized with respect to ultra fast imaging of smaller flow vessels, such as pipes or laboratory-scale chemical reactors. In that way, the scanner is capable of scanning flow cross-sections at a speed of a few thousand frames per second which is sufficient to capture flows of a few meters per second velocity.

Fischer, F.; Hoppe, D.; Schleicher, E.; Mattausch, G.; Flaske, H.; Bartel, R.; Hampel, U.

2008-09-01

393

Characterization of the functional MRI response temporal linearity via optical control of neocortical pyramidal neurons.  

PubMed

The blood oxygenation level-dependent (BOLD) signal serves as the basis for human functional MRI (fMRI). Knowledge of the properties of the BOLD signal, such as how linear its response is to sensory stimuli, is essential for the design and interpretation of fMRI experiments. Here, we combined the cell-type and site-specific causal control provided by optogenetics and fMRI (opto-fMRI) in mice to test the linearity of BOLD signals driven by locally induced excitatory activity. We employed high-resolution mouse fMRI at 9.4 tesla to measure the BOLD response, and extracellular electrophysiological recordings to measure the effects of stimulation on single unit, multiunit, and local field potential activity. Optically driven stimulation of layer V neocortical pyramidal neurons resulted in a positive local BOLD response at the stimulated site. Consistent with a linear transform model, this locally driven BOLD response summated in response to closely spaced trains of stimulation. These properties were equivalent to responses generated through the multisynaptic method of driving neocortical activity by tactile sensory stimulation, and paralleled changes in electrophysiological measures. These results illustrate the potential of the opto-fMRI method and reinforce the critical assumption of human functional neuroimaging that--to first approximation--the BOLD response tracks local neural activity levels. PMID:22016542

Kahn, Itamar; Desai, Mitul; Knoblich, Ulf; Bernstein, Jacob; Henninger, Michael; Graybiel, Ann M; Boyden, Edward S; Buckner, Randy L; Moore, Christopher I

2011-10-19

394

Characterization of the Functional MRI Response Temporal Linearity via Optical Control of Neocortical Pyramidal Neurons  

PubMed Central

The blood oxygenation level-dependent (BOLD) signal serves as the basis for human functional MRI (fMRI). Knowledge of the properties of the BOLD signal, such as how linear its response is to sensory stimuli, is essential to the design and interpretation of fMRI experiments. Here, we combined the cell-type and site-specific causal control provided by optogenetics and fMRI (opto-fMRI) in mice to test the linearity of BOLD signals driven by locally induced excitatory activity. We employed high-resolution mouse fMRI at 9.4 Tesla to measure the BOLD response, and extracellular electrophysiological recordings to measure the effects of stimulation on single-unit, multi-unit, and local field potential activity. Optically driven stimulation of layer V neocortical pyramidal neurons resulted in a positive local BOLD response at the stimulated site. Consistent with a linear transform model, this locally driven BOLD response summated in response to closely spaced trains of stimulation. These properties were equivalent to responses generated through the multi-synaptic method of driving neocortical activity by tactile sensory stimulation, and paralleled changes in electrophysiological measures. These results illustrate the potential of the opto-fMRI method and reinforce the critical assumption of human functional neuroimaging that – to first approximation – the BOLD response tracks local neural activity levels.

Kahn, I.; Desai, M.; Knoblich, U.; Bernstein, J.; Henninger, M.; Graybiel, A. M.; Boyden, E. S.; Buckner, R. L.; Moore, C. I.

2011-01-01

395

Fluoroscopic M Imaging At 0.064 TESLA  

Microsoft Academic Search

We have developed a system for ultra-fast MRI protocols at low field. The system design permits us to acquire the raw data in the background while the reconstruction and display steps repeat as fast as they can in the foreground. The performance speed that one can achieve depends partly on the desired use. One of the more attractive applications is

D. M. Kramer; C. Hawryszko; D. A. Ortendahl; M. Minaise

1990-01-01

396

Central Gland and Peripheral Zone Prostate Tumors have Significantly Different Quantitative Imaging Signatures on 3 Tesla Endorectal, In Vivo T2-Weighted Magnetic Resonance Imagery  

PubMed Central

Purpose To identify and evaluate textural quantitative imaging signatures (QISes) for tumors occurring within the central gland (CG) and peripheral zone (PZ) of the prostate, respectively, as seen on in vivo 3 Tesla endorectal T2-weighted (T2w) Magnetic Resonance Imaging (MRI). Materials and Methods This study utilized 22 pre-operative prostate MRI datasets (16 PZ, 6 CG) acquired from men with confirmed prostate cancer (CaP) and scheduled for radical prostatectomy (RP). The prostate region-of-interest (ROI) was automatically delineated on T2w MRI, following which it was corrected for intensity-based acquisition artifacts. An expert pathologist manually delineated the dominant tumor regions on ex vivo sectioned and stained RP specimens as well as identified each of the studies as either a CG or PZ CaP. A non-linear registration scheme was employed to spatially align and then map CaP extent from the ex vivo RP sections onto the corresponding MRI slices. 110 texture features were then extracted on a per-voxel basis from all T2w MRI datasets. An information theoretic feature selection procedure was then applied to identify QISes comprising T2w MRI textural features specific to CG and PZ CaP, respectively. The QISes for CG and PZ CaP were evaluated via Quadratic Discriminant Analysis (QDA) on a per-voxel basis against the ground truth for CaP on T2w MRI, mapped from corresponding histology. Results The QDA classifier yielded an area under the Receiver Operating characteristic curve of 0.86 for the CG CaP studies, and 0.73 for the PZ CaP studies over 25 runs of randomized 3-fold cross-validation. By comparison, the accuracy of the QDA classifier was significantly lower when (a) using all 110 texture features (with no feature selection applied), as well as (b) a randomly selected combination of texture features. Conclusion CG and PZ prostate cancers have significantly differing textural quantitative imaging signatures on T2w endorectal in vivo MRI.

Viswanath, Satish E.; Bloch, Nicolas B.; Chappelow, Jonathan C.; Toth, Robert; Rofsky, Neil M.; Genega, Elizabeth M.; Lenkinski, Robert E.; Madabhushi, Anant

2012-01-01

397

Magnetization Transfer and adiabatic R1? MRI in the brainstem of Parkinson's disease  

PubMed Central

Background In addition to classic midbrain pathology, Parkinson’s disease (PD) is accompanied by changes in pontine and medullary brainstem structures. These additional abnormalities may underlie non-motor features as well as play a role in motor disability. Methods Using novel magnetic resonance imaging (MRI) methods rotating frame adiabatic R1? (i.e., measurements of longitudinal relaxation during adiabatic full passage pulses) and modified magnetization transfer (MT) MRI mapping, we sought to identify brainstem alterations in nine individuals with mild-moderate PD (off medication) and ten age-matched controls at 4 Tesla. Results We discovered significant differences in MRI parameters between midbrain and medullary brainstem structures in control subjects as compared to PD patients. Conclusions These findings support the presence of underlying functional/structural brainstem changes in mild-moderate PD.

Tuite, Paul J; Mangia, Silvia; Tyan, Andrew E; Lee, Michael K.; Garwood, Michael; Michaeli, Shalom

2012-01-01

398

High-Performance 3D Compressive Sensing MRI Reconstruction Using Many-Core Architectures  

PubMed Central

Compressive sensing (CS) describes how sparse signals can be accurately reconstructed from many fewer samples than required by the Nyquist criterion. Since MRI scan duration is proportional to the number of acquired samples, CS has been gaining significant attention in MRI. However, the computationally intensive nature of CS reconstructions has precluded their use in routine clinical practice. In this work, we investigate how different throughput-oriented architectures can benefit one CS algorithm and what levels of acceleration are feasible on different modern platforms. We demonstrate that a CUDA-based code running on an NVIDIA Tesla C2050 GPU can reconstruct a 256 × 160 × 80 volume from an 8-channel acquisition in 19 seconds, which is in itself a significant improvement over the state of the art. We then show that Intel's Knights Ferry can perform the same 3D MRI reconstruction in only 12 seconds, bringing CS methods even closer to clinical viability.

Kim, Daehyun; Trzasko, Joshua; Smelyanskiy, Mikhail; Haider, Clifton; Dubey, Pradeep; Manduca, Armando

2011-01-01

399

[Influence of mechanical effect due to MRI-magnet on tattoo seal and eye makeup].  

PubMed

The purpose of our study was to assess the mechanical effect on tattoo seals and eye makeup caused by a spatial magnetic gradient in the magnetic resonance imaging (MRI) system. Seven kinds of tattoo seals and three kinds of eye makeup, i.e., mascara, eye shadow, and eyeliner were used. On a 3.0-Tesla MRI, we determined these deflection angles according to a method established by the American Society for Testing and Materials (ASTM) at the position that produced the greatest magnetically induced deflection. Eighty-five percent of the tattoo seals showed deflection angles greater than 45 degrees of the ASTM guidelines, and the mascara and eye shadow showed over 40 degrees. This was because these contained ferromagnetic pigments such as an iron oxide, but those translational forces were very small owing to slight mass. However, it is desirable that these should be removed before MRI examination to prevent secondary problems. PMID:18509220

Morishita, Yuta; Miyati, Tosiaki; Ueda, Jousei; Shimizu, Mitsuru; Hamaguchi, Takashi; Fujiwara, Yasuhiro; Hayashi, Hiroyuki

2008-05-20

400

Cortical phase changes in Alzheimer's disease at 7T MRI: A novel imaging marker.  

PubMed

BACKGROUND: Postmortem studies have indicated the potential of high-field magnetic resonance imaging (MRI) to visualize amyloid depositions in the cerebral cortex. The aim of this study is to test this hypothesis in patients with Alzheimer's disease (AD). METHODS: T2*-weighted MRI was performed in 16 AD patients and 15 control subjects. All magnetic resonance images were scored qualitatively by visual assessment, and quantitatively by measuring phase shifts in the cortical gray matter and hippocampus. Statistical analysis was performed to assess differences between groups. RESULTS: Patients with AD demonstrated an increased phase shift in the cortex in the temporoparietal, frontal, and parietal regions (P < .005), and this was associated with individual Mini-Mental State Examination scores (r = -0.54, P < .05). CONCLUSION: Increased cortical phase shift in AD patients demonstrated on 7-tesla T2*-weighted MRI is a potential new biomarker for AD, which may reflect amyloid pathology in the early stages. PMID:23712002

van Rooden, Sanneke; Versluis, Maarten J; Liem, Michael K; Milles, Julien; Maier, Andrea B; Oleksik, Ania M; Webb, Andrew G; van Buchem, Mark A; van der Grond, Jeroen

2013-05-25

401

Quantitative T2* imaging of metastatic human breast cancer to brain in the nude rat at 3-Tesla  

PubMed Central

This study uses quantitative T2* imaging to track ferumoxides-protamine sulfate (FEPro) labeled MDA-MB-231BRL human breast cancer cells (231BRL) that metastasize to the nude rat brain. Four cohorts of nude rats were intracardiac (IC) injected with either FEPro labeled, unlabeled, TRIAL treated (to induce apoptosis) 231BRL cells or saline in order to develop metastatic breast cancer in the brain. The rat heads were imaged serially over 3-4 weeks using a gradient multi-echo and turbo spin echo pulse sequences at 3 Tesla with a solenoid receive only 4cm diameter coil. Quantitative T2* maps of whole brain were obtained by applying single exponential fitting to the signal intensity of T2* images and the distribution of T2* values in brain voxels were calculated. MRI findings were correlated with Prussian blue (PB) stain and immunohistochemical stain for iron in breast cancer and macrophages. Quantiative analysis of T2* from the brain voxels demonstrated a significant shift to lower values following IC injection of FEPro labeled 231BRL cells as compared to animals that received unlabeled cells or apoptotic cells or saline. Quartile analysis based on the T2* distribution obtained from brain voxels demonstrated significant differences (p<0.0083) in number of voxels with T2* values between 10-35 (Q1), 36-60 (Q2) and 61-86 (Q3) milliseconds from day 1 to 3 weeks post infusion of labeled 231BRL cells compared to baseline scans. There was no significant differences in the distribution of T2* obtained from serial MRI in rats receiving unlabeled or TRIAL treated cells or saline. Histological analysis demonstrated isolated PB positive breast cancer cells scattered in brains of rats that received labeled cells compared to animals that received unlabeled or apoptotic cells. Quantitative T2* analysis of FEPro labeled metastasized cancer cells was possible even after the hypointense voxels are no longer visible on T2*-weighted images.

Song, Ho-Taek; Jordan, Elaine K.; Lewis, Bobbi K.; Gold, Eric; Liu, Wei; Frank, Joseph A.

2010-01-01

402

In vivo high-resolution localized 1H MR spectroscopy in the awake rat brain at 7 Tesla  

PubMed Central

In vivo localized high-resolution 1H MR spectroscopy was performed in multiple brain regions without the use of anesthetic or paralytic agents in awake head-restrained rats that were previously trained in a simulated MRI environment using a 7 Tesla MR system. Spectra were obtained using a short echo time single-voxel point-resolved spectroscopy technique with voxel size ranging from 27–32.4 mm3 in the regions of anterior cingulate cortex, somatosensory cortex, hippocampus, and thalamus. Quantifiable spectra, without the need for any additional post-processing to correct for possible motion were reliably detected including the metabolites of interest such as ?-aminobutyric acid, glutamine, glutamate, myo-inositol, N-acetylaspartate, taurine, glycerophosphorylcholine/phosphorylcholine, creatine/phosphocreatine, and N-acetylaspartate/N-acetylaspartylglutamate. The spectral quality was comparable to spectra from anesthetized animals with sufficient spectral dispersion to separate metabolites such as glutamine and glutamate. Results from this study suggest that reliable information on major metabolites can be obtained without the confounding effects of anesthesia or paralytic agents in rodents.

Xu, Su; Ji, Yadong; Chen, Xi; Yang, Yihong; Gullapalli, Rao; Masri, Radi

2012-01-01

403

The effect of fMRI (noise) on cognitive control.  

PubMed

Stressful situations, the aversiveness of events, or increases in task difficulty (e.g., conflict) have repeatedly been shown to be capable of triggering attentional control adjustments. In the present study we tested whether the particularity of an fMRI testing environment (i.e., EPI noise) might result in such increases of the cognitive control exerted. We found that participants were more effective in controlling episodic retrieval of previous stimulus-response bindings (Experiment 1), in switching to a new task (Experiment 2), and shielding a current goal from distracting response tendencies (Experiment 3) if they were exposed to challenging task situations, such as 70 dB echo planar imaging noise sampled from an fMRI scanner. These findings have considerable theoretical implications in questioning the widespread assumption that people are equally devoted to easy and more challenging tasks, and methodological implications in raising the possibility that experiments carried out in fMRI scanners or under otherwise challenging conditions systematically overestimate contributions from cognitive control processes. PMID:22201469

Hommel, Bernhard; Fischer, Rico; Colzato, Lorenza S; van den Wildenberg, Wery P M; Cellini, Cristiano

2011-12-26

404

The Basics of MRI  

NSDL National Science Digital Library

The Basics of MRI is a hypertextbook by Dr. Joseph Hornak of the Rochester Institute of Technology that focuses on the mathematics and physics of magnetic resonance imaging. "Exponential Functions," "Differentials and Integrals," and "Coordinate Transformation" are just a few of the mathematical topics discussed. The physics behind MRI is broken down into the following chapters: "Spin Physics," "NMR Spectroscopy," "Fourier Transforms," "Imaging Principles," and "Fourier Transform Imaging Principles." Hornak has also included a multitude of information on imaging techniques, presentation, and hardware. Those concerned with what occurs during a MRI exam, rather than the math and physics of MRI, will want to consult the chapter entitled "Your MRI Exam."

Hornak, Joseph P.

1996-01-01

405

In-line digital holographic microscopy using a consumer scanner.  

PubMed

We demonstrate an in-line digital holographic microscopy using a consumer scanner. The consumer scanner can scan an image with 4,800?dpi. The pixel pitch is approximately 5.29??m. The system using a consumer scanner has a simple structure, compared with synthetic aperture digital holography using a camera mounted on a two-dimensional moving stage. In this demonstration, we captured an in-line hologram with 23, 602 × 18, 023 pixels (?0.43 gigapixels). The physical size of the scanned hologram is approximately 124?mm × 95?mm. In addition, to accelerate the reconstruction time of the gigapixel hologram and decrease the amount of memory for the reconstruction, we applied the band-limited double-step Fresnel diffraction to the reconstruction. PMID:24036588

Shimobaba, Tomoyoshi; Yamanashi, Hiroya; Kakue, Takashi; Oikawa, Minoru; Okada, Naohisa; Endo, Yutaka; Hirayama, Ryuji; Masuda, Nobuyuki; Ito, Tomoyoshi

2013-09-16

406

High Bandwidth Electro-optic Scanner for Optical Data Storage  

NASA Astrophysics Data System (ADS)

Beam deflectors can be used as fine tracking actuators to improve track access time and data rate in future high performance optical disk drives. In this paper we report on the use of an electro-optic (EO) scanner for optical data storage. Track following has been accomplished using this EO actuator with a servo bandwidth of 200 kHz, and single-stage high-speed track switching/following has been demonstrated in a new optical head tracking system with reduced offset. A fine tracking experiment has also been demonstrated using an EO actuator with a voice coil motor (VCM) actuator to extend the fine tracking range. A new compensator design method, the PQ method, has been used for this scanner/VCM compound actuator system. Significant improvements in track switching/following speed are demonstrated with the scanner/VCM compound actuator as compared to tracking with the VCM actuator alone.

Zhai, Jinhui; Huang, Yuhong; Schroeck, Steve; Messner, W.; Stancil, Daniel D.; Schlesinger, T. E.

2000-02-01

407

Trade-offs in rotary mirror scanner design  

NASA Astrophysics Data System (ADS)

The design of rotary mirror scanners is a complex process involving many trade-offs. This paper explores these issues emphasizing how the design can be optimized for a particular application. Examples range from thermal imagers to prepress equipment, and the trade-offs covered include scan accuracy vs cost, efficiency vs performance. The topics covered include polygons, motors, bearings and housings. The configuration of these parts and their interactions are considered. Particular emphasis is placed on reducing the power consumption of the scanner through careful consideration of windage - the drag on the polygon due to its movement through the surrounding gas. The main conclusion is that by careful design the effect of trade-offs can be minimized; this allows the design of low cost high accuracy scanners.

Colquhoun, A. B.; Cowan, D. W.; Shepherd, J.

1991-02-01

408

CT Coronary Angiography: 256-Slice and 320-Detector Row Scanners  

PubMed Central

Multidetector computed tomography (MDCT) has rapidly evolved from 4-detector row systems in 1998 to 256-slice and 320-detector row CT systems. With smaller detector element size and faster gantry rotation speed, spatial and temporal resolution of the 64-detector MDCT scanners have made coronary artery imaging a reliable clinical test. Wide-area coverage MDCT, such as the 256-slice and 320-detector row MDCT scanners, has enabled volumetric imaging of the entire heart free of stair-step artifacts at a single time point within one cardiac cycle. It is hoped that these improvements will be realized with greater diagnostic accuracy of CT coronary angiography. Such scanners hold promise in performing a rapid high quality “triple rule-out” test without high contrast load, improved myocardial perfusion imaging, and even four-dimensional CT subtraction angiography. These emerging technical advances and novel applications will continue to change the way we study coronary artery disease beyond detecting luminal stenosis.

Hsiao, Edward M.; Rybicki, Frank J.; Steigner, Michael

2010-01-01

409

Automated pipe scanner for ultrasonic inspection. Final report  

SciTech Connect

The need for reliable, accurate, and repeatable examination of piping welds in boiling-water-reactor (BWR) systems has received considerable attention in recent years because of increasing occurrences of intergranular stress-corrosion cracking (IGSCC) in the austenitic stainless steel piping used in these systems. This report describes the results of a program designed to develop automated, remotely controlled scanner mechanisms and booted ultrasonic search units for pipe weld examinations. The principal scanner development goals have been achieved. These goals include scanners of low profile, easy portability, rapid installation and removal and accurate and repeatable scan capabilities over a wide range of pipe diameters. Additional accomplishments are booted search unit designs that provide universal adaptability to pipe inspection surface geometries and a multi-refracted-angle inspection capability within a single search unit.

Fleming, M.; Mitchell, R.; Humphries, J.; De La Torre, D.; Levin, S.; Jacobs, B.; Beller, L.; Mikesell, C.

1984-01-01

410

A Passively-Suspended Tesla Pump Left Ventricular Assist Device  

PubMed Central

The design and initial test results of a new passively suspended Tesla type LAVD blood pump are described. CFD analysis was used in the design of the pump. Overall size of the prototype device is 50 mm in diameter and 75 mm in length. The pump rotor has a density lower than that of blood and when spinning inside the stator in blood it creates a buoyant centering force that suspends the rotor in the radial direction. The axial magnetic force between the rotor and stator restrain the rotor in the axial direction. The pump is capable of pumping up to 10 liters/min at a 70 mmHg head rise at 8000 RPM. The pump has demonstrated a normalized index of hemolysis level below .02 mg/dL for flows between 2 and 9.7 L/min. An inlet pressure sensor has also been incorporated into the inlet cannula wall and will be used for control purposes. One initial in vivo study showed an encouraging result. Further CFD modeling refinements are planned as well as endurance testing of the device.

Izraelev, Valentin; Weiss, William J.; Fritz, Bryan; Newswanger, Raymond K.; Paterson, Eric G.; Snyder, Alan; Medvitz, Richard B.; Cysyk, Joshua; Pae, Walter E.; Hicks, Dennis; Lukic, Branka; Rosenberg, Gerson

2009-01-01

411

Feasibility Study of a HOM IOT for TESLA  

NASA Astrophysics Data System (ADS)

For the TESLA linear collider 1.3 GHz RF sources with 10 MW peak power and about 70% efficiency are needed. As an alternative to the development of a Multibeam-Klystron, we investigate the feasibility of an IOT (Inductive Output Tube). This is a very compact RF source: The time structure of the beam is produced by a gated emission cathode and the output cavity is directly adjacent to the anode. Unlike IOTs, conventional klystrons lose some of their design efficiency when they are operated below saturation, because only the RF component of the beam is reduced and not the DC beam current. In contrast to this the cathode current of an IOT is controlled by the drive power. In order to keep the gun voltage low, we investigate a device with a hollow beam where the output cavity is excited in a higher order mode (HOM), as was recently suggested by CPI(E.Lien, H.Bohlen, US Patent Application Serial No. 08/413,034). Computer simulations are carried out with the CAD-system MAFIA. First, an existing Klystrode TM IOT built by CPI is analysed. Simulation results will be shown and compared to experimental data. Based upon this experience, a design strategy is discussed for the HOM IOT.

Schütt, Petra; Weiland, Thomas; Gamp, Alexander; Lu, Fuhai

1997-05-01

412

MRI of ovarian masses.  

PubMed

MRI provides exquisite views of the pelvic anatomy through its high spatial resolution and tissue contrast, and as such plays a key role in the work up of ovarian lesions, identifying features that distinguish benign and malignant lesions. In the case of primary tumors it enables local staging and detection of metastatic disease to help guide management options such as complex surgery or the consideration of neoadjuvant chemotherapy. Functional MRI techniques such as diffusion-weighted MRI (DW-MRI), dynamic contrast-enhanced MRI (DCE-MRI) and tumor-selective molecular imaging are currently being evaluated as possible predictive and prognostic biomarkers in the context of ovarian malignancy, and may play a larger role in routine clinical practice in the future. Herein we provide an overview of the conventional and advanced MRI techniques used to characterize ovarian masses and of the role that MR plays in the staging, treatment selection and follow up of patients with ovarian cancer. PMID:23355430

Vargas, Hebert Alberto; Barrett, Tristan; Sala, Evis

2013-02-01

413

Novel scanner characterization method for color measurement and diagnostics applications  

NASA Astrophysics Data System (ADS)

We propose a novel scanner characterization approach for applications requiring color measurement of hardcopy output in printer calibration, characterization, and diagnostic applications. It is assumed that a typical printed medium comprises the three basic colorants C, M, Y. The proposed method is particularly advantageous when additional colorants are used in the print (e.g. black (K)). A family of scanner characterization targets is constructed, each varying in C, M, Y and at a fixed level of K. A corresponding family of 3-D scanner characterizations is derived, one for each level of K. Each characterization maps scanner RGB to a colorimetric representation such as CIELAB, using standard characterization techniques. These are then combined into a single 4-D characterization mapping RGBK to CIELAB. A refinement of the technique improves performance significantly by using a function of the scanned values for K (e.g. the scanner's green channel response to printed K) instead of the digital K value directly. This makes this new approach more robust with respect to variations in printed K over time. Secondly it enables, with a single scanner characterization, accurate color measurement of prints from different printers within the same family. Results show that the 4-D characterization technique can significantly outperform standard 3-D approaches especially in cases where the image being scanned is a patch target made up of unconstrained CMYK combinations. Thus the algorithm finds particular use in printer characterization and diagnostic applications. The method readily generalizes to printed media containing other (e.g "hi-fi") colorants, and also to other image capture devices such as digital cameras.

Lee, Bong-Sun; Bala, Raja; Sharma, Gaurav

2006-02-01

414

Magnetic Particle Imaging (MPI) for NMR and MRI researchers  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

415

An Open-Source Hardware and Software System for Acquisition and Real-Time Processing of Electrophysiology during High Field MRI  

PubMed Central

Simultaneous recording of electrophysiology and functional magnetic resonance imaging (fMRI) is a technique of growing importance in neuroscience. Rapidly evolving clinical and scientific requirements have created a need for hardware and software that can be customized for specific applications. Hardware may require customization to enable a variety of recording types (e.g., electroencephalogram, local field potentials, or multi-unit activity) while meeting the stringent and costly requirements of MRI safety and compatibility. Real-time signal processing tools are an enabling technology for studies of learning, attention, sleep, epilepsy, neurofeedback, and neuropharmacology, yet real-time signal processing tools are difficult to develop. We describe an open source system for simultaneous electrophysiology and fMRI featuring low-noise (< 0.6 uV p-p input noise), electromagnetic compatibility for MRI (tested up to 7 Tesla), and user-programmable real-time signal processing. The hardware distribution provides the complete specifications required to build an MRI-compatible electrophysiological data acquisition system, including circuit schematics, print circuit board (PCB) layouts, Gerber files for PCB fabrication and robotic assembly, a bill of materials with part numbers, data sheets, and vendor information, and test procedures. The software facilitates rapid implementation of real-time signal processing algorithms. This system has used in human EEG/fMRI studies at 3 and 7 Tesla examining the auditory system, visual system, sleep physiology, and anesthesia, as well as in intracranial electrophysiological studies of the non-human primate visual system during 3 Tesla fMRI, and in human hyperbaric physiology studies at depths of up to 300 feet below sea level.

Purdon, Patrick L.; Millan, Hernan; Fuller, Peter L.; Bonmassar, Giorgio

2008-01-01

416

Relationship among fMRI, contrast sensitivity and visual acuity.  

PubMed

The purpose of this study was to ascertain whether visual acuity or contrast sensitivity function (CSF) is proportional to visual cortical function based on fMRI volume and level of activation or Z-score. Forced choice procedures were utilized to measure the monocular log minimal angle of resolution (logMAR) visual acuity and CSF. The CSF data were collapsed into a single index by the use of weighted mean contrast sensitivity (WMCS), being defined as the mean of the products of each spatial frequency multiplied by its corresponding contrast sensitivity. fMRI data had been obtained with a 1.5 T GE Signa scanner with visual stimuli including 1.0 and 2.0 c/deg vertical sinusoidal gratings. Subjects consisted of eight normal adults and five amblyopic patients, with the amblyopic subjects added to gauge whether the outcome was due to a restricted range of scores or the small number of study participants. In normal subjects, the fMRI volume and level of activation exhibited no statistically significant correlation with visual acuity at P<0.05. Statistically significant correlations were obtained between WMCS and fMRI volume (R=0.765, P=0.027) and fMRI level of activation (R=0.645, P=0.007), with right eye stimulation using the 1.0 c/deg grating. On the whole, statistically significant correlations between WMCS and fMRI parameters were maintained when subject age was held constant and when data from the five amblyopic subjects were included to expand the range of values and increase the number of data sets for analysis. fMRI volume and Z-score were more closely associated with the CSF, as defined by WMCS, than visual acuity. The results suggest that the CSF reflects the underlying visual cortical cells responsible for fMRI volume and the level of activation. PMID:21035430

Leguire, L E; Algaze, A; Kashou, N H; Lewis, J; Rogers, G L; Roberts, C

2010-10-28

417

A novel, general-purpose, MR-compatible, manually actuated robotic manipulation system for minimally invasive interventions under direct MRI guidance.  

PubMed

BACKGROUND: Performing minimally invasive interventions under direct MRI guidance offers significant advantages. Required accessibility to the patient inside the MRI scanner is fairly limited, and employment of robotic assistance has been proposed. The development of MR-compatible robotic systems entails engineering challenges related to geometric constraints and the magnetic nature of the scanning environment. METHODS: A novel, general-purpose, MR-compatible robotic manipulation system has been developed for the performance of minimally invasive interventions inside a cylindrical scanner under direct MRI guidance. The system is endowed with five degrees of freedom (DOF), is characterized by a unique kinematics structure and is manually actuated. RESULTS: The prototype system was shown to exhibit the required MR-compatibility characteristics and a task-space positioning ability of approximately 5 mm. Needle targeting testing demonstrated a 93% success rate in acquiring a 5 mm spherical target. Phantom testing was performed inside a 3 T scanner and results are reported for an experimental study simulating MRI-guided, manipulator-assisted, MR arthrography. CONCLUSIONS: Robotic assistance provided by the developed manipulator may effectively facilitate the performance of various MRI-guided, minimally invasive interventions inside a cylindrical scanner. Copyright © 2013 John Wiley & Sons, Ltd. PMID:23625884

Christoforou, Eftychios G; Seimenis, Ioannis; Andreou, Eleni; Eracleous, Eleni; Tsekos, Nikolaos V

2013-04-29

418

Ferrofluid Film Bearing for enhancement of rotary scanner performance  

NASA Astrophysics Data System (ADS)

Hydrodynamic bearings utilizing ferrofluids are a new class of high performance bearings. These bearings are self-contained with ferrofluid acting both as a hydrodynamic pressure film and a sealant. Although relatively unknown in the laser scanner industry, ferrofluids have been widely used over the last two decades for applications in the semiconductor, computer and audio marketplaces. In this paper, performance features of Ferrofluid Film Bearings are also discussed, and experimental data such as power consumption, rotational accuracy and audible noise are presented to show that Ferrofluid Film Bearings enhance the performance of high resolution scanners and in this application are superior to ball bearing and gas bearing performance.

Cheever, Charles; Li, Zhixin; Raj, Kuldip

1991-02-01

419

Cyclone: A laser scanner for mobile robot navigation  

NASA Astrophysics Data System (ADS)

Researchers at Carnegie Mellon's Field Robotics Center have designed and implemented a scanning laser rangefinder. The device uses a commercially available time-of-flight ranging instrument that is capable of making up to 7200 measurements per second. The laser beam is reflected by a rotating mirror, producing up to a 360 degree view. Mounted on a robot vehicle, the scanner can be used to detect obstacles in the vehicle's path or to locate the robot on a map. This report discusses the motivation, design, and some applications of the scanner.

Singh, Sanjiv; West, Jay

1991-09-01

420

Evaluation of Images for Computed Tomography Scanners by Entropy  

NASA Astrophysics Data System (ADS)

The precision of images for computed tomography (CT) scanners is synthetically evaluated by a single entropy number. The results obtained from four CT scanners show that the maximum and minimum transmitted information quantities are 1.83 bits and 1.23 bits per image on average, respectively (ideal transmitted information quantities are 2.32 bits). Assuming that only the standard deviation of CT numbers and the contrast scale affect the precision of CT images, the transmitted information quantities are calculated theoretically and are compared with the measured ones.

Uchida, Suguru; Katsuragawa, Shigehiko; Sueyoshi, Takehiro

1980-11-01

421

Shift variant linear system modeling for multispectral scanners  

NASA Astrophysics Data System (ADS)

Multispectral scanner data are affected both by the spatial impulse response of the sensor and the spectral response of each channel. To achieve a realistic representation for the output data for a given scene spectral input, both of these effects must be incorporated into a forward model. Each channel can have a different spatial response and each has its characteristic spectral response. A forward model is built which includes the shift invariant spatial broadening of the input for the channels and the shift variant spectral response across channels. The model is applied to the calibrated airborne multispectral scanner as well as the airborne terrestrial applications sensor developed at NASA Stennis Space Center.

Amini, Abolfazl M.; Ioup, George E.; Ioup, Juliette W.

1995-07-01

422

A prototype quantitative film scanner for radiochromic film dosimetry  

SciTech Connect

We have developed a high resolution, quantitative, two-dimensional optical film scanner for use with a commercial high sensitivity radiochromic film (RCF) for measuring single fraction external-beam radiotherapy dose distributions. The film scanner was designed to eliminate artifacts commonly observed in RCF dosimetry. The scanner employed a stationary light source and detector with a moving antireflective glass film platen attached to a high precision computerized X-Y translation stage. An ultrabright red light emitting diode (LED) with a peak output at 633 nm and full width at half maximum (FWHM) of 16 nm was selected as the scanner light source to match the RCF absorption peak. A dual detector system was created using two silicon photodiode detectors to simultaneously measure incident and transmitted light. The LED light output was focused to a submillimeter (FWHM 0.67 mm) spot size, which was determined from a scanning knife-edge technique for measuring Gaussian optical beams. Data acquisition was performed with a 16-bit A/D card in conjunction with commercial software. The linearity of the measured densities on the scanner was tested using a calibrated neutral-density step filter. Sensitometric curves and three IMRT field scans were acquired with a spatial resolution of 1 mm for both radiographic film and RCF. The results were compared with measurements taken with a commercial diode array under identical delivery conditions. The RCF was rotated by 90 deg. and rescanned to study orientation effects. Comparison between the RCF and the diode array measurements using percent dose difference and distance-to-agreement criteria produced average passing rates of 99.0% using 3%/3 mm criteria and 96.7% using 2%/2 mm criteria. The same comparison between the radiographic film and diode array measurements resulted in average passing rates 96.6% and 91.6% for the above two criteria, respectively. No measurable light-scatter or interference scanner artifacts were observed. The RCF rotated by 90 deg. showed no measurable orientation effect. A scan of a 15x15 cm{sup 2} area with 1 mm resolution required 22 min to acquire. The LED densitometer provides an accurate film dosimetry system with 1 mm or better resolution. The scanner eliminates the orientation dependence of RCF dosimetry that was previously reported with commercial flatbed scanners.

Ranade, Manisha K.; Li, Jonathan G.; Dubose, Ryan S.; Kozelka, Jakub; Simon, William E.; Dempsey, James F. [Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610 (United States); Spartanburg Regional Hospital Gibbs Cancer Center, Spartanburg, South Carolina 29303 (United States); Sun Nuclear Corporation, Melbourne, Florida 32940 (United States); Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610 (United States)

2008-02-15

423

Satellite orientation and position for geometric correction of scanner imagery.  

USGS Publications Warehouse

The USGS Mini Image Processing System currently relies on a polynomial method for geometric correction of Landsat multispectral scanner (MSS) data. A large number of ground control points are required because polynomials do not model the sources of error. In order to reduce the number of necessary points, a set of mathematical equations modeling the Landsat satellite motions and MSS scanner has been derived and programmed. A best fit to the equations is obtained by using a least-squares technique that permits computation of the satellite orientation and position parameters based on only a few control points.-from Author

Salamonowicz, P. H.

1986-01-01

424

Initial performance evaluation of a high resolution Albira small animal positron emission tomography scanner with monolithic crystals and depth-of-interaction encoding from a user's perspective  

NASA Astrophysics Data System (ADS)

The user evaluation of the Albira small animal positron emission tomography scanner is presented. The system has a \\varnothing80 mm × 40 mm field of view. In the center of the field of view, it has 2.49% sensitivity, with 33% solid angle coverage, and 0.88% sensitivity for a mouse phantom. The maximum of noise equivalent counts is 14.6 kcps at 6.0 MBq for a mouse phantom. The scanner employs an innovative crystal design of eight 40(50) × 40(50) × 9.8 mm3 LYSO tapered monolithic crystals forming detector modules read by position-sensitive photomultipliers. This design allows for easy depth-of-interaction readout. The system saturates at 6.7 MBq for the mouse phantom. As an example of the application of the Albira system, some preliminary results from a study of ischemic stroke on animal models with 18-FDG co-registered with MRI images are shown.

Balcerzyk, Marcin; Kontaxakis, George; Delgado, Mercedes; Garcia-Garcia, Luis; Correcher, Carlos; Gonzalez, Antonio J.; Gonzalez, Aurora; Rubio, Jose L.; Benlloch, Jose M.; Pozo, Miguel A.

2009-10-01

425

Seizure-induced brain lesions: A wide spectrum of variably reversible MRI abnormalities.  

PubMed

Introduction MRI abnormalities in the postictal period might represent the effect of the seizure activity, rather than its structural cause. Material and Methods Retrospective review of clinical and neuroimaging charts of 26 patients diagnosed with seizure-related MR-signal changes. All patients underwent brain-MRI (1.5-Tesla, standard pre- and post-contrast brain imaging, including DWI-ADC in 19/26) within 7 days from a seizure and at least one follow-up MRI, showing partial or complete reversibility of the MR-signal changes. Extensive clinical work-up and follow-up, ranging from 3 months to 5 years, ruled out infection or other possible causes of brain damage. Seizure-induced brain-MRI abnormalities remained a diagnosis of exclusion. Site, characteristics and reversibility of MRI changes, and association with characteristics of seizures were determined. Results MRI showed unilateral (13/26) and bilateral abnormalities, with high (24/26) and low (2/26) T2-signal, leptomeningeal contrast-enhancement (2/26), restricted diffusion (9/19). Location of abnormality was cortical/subcortical, basal ganglia, white matter, corpus callosum, cerebellum. Hippocampus was involved in 10/26 patients. Reversibility of MRI changes was complete in 15, and with residual gliosis or focal atrophy in 11 patients. Reversibility was noted between 15 and 150 days (average, 62 days). Partial simple and complex seizures were associated with hippocampal involvement (p=0.015), status epilepticus with incomplete reversibility of MRI abnormalities (p=0.041). Conclusions Seizure or epileptic status can induce transient, variably reversible MRI brain abnormalities. Partial seizures are frequently associated with hippocampal involvement and status epilepticus with incompletely reversible lesions. These seizure-induced MRI abnormalities pose a broad differential diagnosis; increased awareness may reduce the risk of misdiagnosis and unnecessary intervention. PMID:23787273

Cianfoni, A; Caulo, M; Cerase, A; Della Marca, G; Falcone, C; Di Lella, G M; Gaudino, S; Edwards, J; Colosimo, C

2013-06-17

426

The Influence of Head Motion on Intrinsic Functional Connectivity MRI  

PubMed Central

Functional connectivity MRI (fcMRI) has been widely applied to explore group and individual differences. A confounding factor is head motion. Children move more than adults, older adults more than younger adults, and patients more than controls. Head motion varies considerably among individuals within the same population. Here we explored the influence of head motion on fcMRI estimates. Mean head displacement, maximum head displacement, the number of micro movements (> 0.1 mm), and head rotation were estimated in 1000 healthy, young adult subjects each scanned for two resting-state runs on matched 3T scanners. The majority of fcMRI variation across subjects was not linked to estimated head motion. However, head motion had significant, systematic effects on fcMRI network measures. Head motion was associated with decreased functional coupling in the default and frontoparietal control networks – two networks characterized by coupling among distributed regions of association cortex. Other network measures increased with motion including estimates of local functional coupling and coupling between left and right motor regions – a region pair sometimes used as a control in studies to establish specificity. Comparisons between groups of individuals with subtly different levels of head motion yielded difference maps that could be mistaken for neuronal effects in other contexts. These effects are important to consider when interpreting variation between groups and across individuals.

Van Dijk, Koene R.A.; Sabuncu, Mert R.; Buckner, Randy L.

2011-01-01

427

MRI-Compatible Pneumatic Robot for Transperineal Prostate Needle Placement  

PubMed Central

Magnetic resonance imaging (MRI) can provide high-quality 3-D visualization of prostate and surrounding tissue, thus granting potential to be a superior medical imaging modality for guiding and monitoring prostatic interventions. However, the benefits cannot be readily harnessed for interventional procedures due to difficulties that surround the use of high-field (1.5T or greater) MRI. The inability to use conventional mechatronics and the confined physical space makes it extremely challenging to access the patient. We have designed a robotic assistant system that overcomes these difficulties and promises safe and reliable intraprostatic needle placement inside closed high-field MRI scanners. MRI compatibility of the robot has been evaluated under 3T MRI using standard prostate imaging sequences and average SNR loss is limited to 5%. Needle alignment accuracy of the robot under servo pneumatic control is better than 0.94 mm rms per axis. The complete system workflow has been evaluated in phantom studies with accurate visualization and targeting of five out of five 1 cm targets. The paper explains the robot mechanism and controller design, the system integration, and presents results of preliminary evaluation of the system.

Fischer, Gregory S.; Iordachita, Iulian; Csoma, Csaba; Tokuda, Junichi; DiMaio, Simon P.; Tempany, Clare M.; Hata, Nobuhiko; Fichtinger, Gabor

2010-01-01

428

Multibeam two-dimensional binary optics laser scanner  

NASA Astrophysics Data System (ADS)

We have developed a two-dimensional, multibeam, binary optic based scanner for transmission/receiver functions for LADAR and other applications under a Small Business Innovation Research (SBIR) contract from Eglin Air Force Base. Multibeam scan provides many unique advantages including: increased data rate for pulsed lasers; increased scan coverage; and programmable broadcasting for optical interconnect applications.

Jain, Anil K.

1994-06-01

429

Counting Rates Modeling for PET Scanners With GATE  

Microsoft Academic Search

Several developments were made in the GATE simulation platform to allow accurate modeling of the count rate performances of PET scanners over a wide range of activity concentrations. A background noise module, a dead time and limited bandwidth modeling for the coincidences, and a delayed coincidence builder were added in the code. The results obtained for the modeling of the

David Guez; Frédéric Bataille; Claude Comtat; Pierre-Francois Honore; Sébastien Jan; Sophie Kerhoas

2008-01-01

430

Testing PEPT Algorithm on a Medical PET Scanner  

NASA Astrophysics Data System (ADS)

The basis of Positron Emission Tomography (PET) is the detection of the photons produced, when a positron annihilates with an electron. Conservation of energy and momentum then require that two 511 keV gamma rays are emitted almost back to back (180° apart). This method is used to determine the spatial distribution of a positron emitting fluid. Verifying the position of a single emitting particle in an object instead of determining the distribution of a positron emitting fluid is the basis of another technique, which has been named positron emitting particle tracking PEPT and has been developed in Birmingham University. Birmingham University has recently obtained the PET scanner from Hammersmith Hospital which was installed there in 1987. This scanner consists of 32 detector buckets, each includes 128 bismuth germanate detection elements, which are configured in 8 rings. This scanner has been rebuilt in a flexible geometry and will be used for PEPT studies. Testing the PEPT algorithm on ECAT scanner gives a high data rate, can track approximately accurate at high speed and also has the possibility of making measurements on large vessels.

Sadrmomtaz, Alireza

431

X- and ?-rays computerized minitomograph scanner for soil science  

Microsoft Academic Search

A computerized tomograph scanner system that uses X- and ?-rays for applications in soil science is described. Use of the apparatus in measuring volumetric water content to an accuracy of ±3% and soil bulk density to ±2% (in grams per cubic centimeters) is discussed. The system features translation and rotation scanning modes, a 200-mm effective field of view, signal processing

PAULO ESTEVAO CRUVINEL; ROBERTO CESAREO; SILVIO CRESTANA; SERGIO MASCARENHAS

1990-01-01

432

Optical beam scanner with phase-variable semiconductor waveguides  

NASA Astrophysics Data System (ADS)

This paper describes the design and the principle of operation of an opitcal beam scanner with two phase-variable semiconductor waveguides, which has the possibility of high-speed steering. The maximum deflection angle achieved with the device was 0.67 under 9.5 V reverse bias. A schematic diagram of the fabricated device is presented.

Moriki, Kazunori; Ohnishi, Yoshihumi; Uchida, Hiroshi; Hattori, Takeo; Iga, Kenichi

1990-07-01

433