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Fast Imaging (fast + imaging)
Kinds of Fast Imaging Selected AbstractsMR temperature measurement in liver tissue at 0.23 T with a steady-state free precession sequenceMAGNETIC RESONANCE IN MEDICINE, Issue 5 2002D. Germain Abstract MRI can be used for monitoring temperature during a thermocoagulation treatment of tumors. The aim of this study was to demonstrate the suitability of a 3D steady-state free precession sequence (3D Fast Imaging with Steady-State Precession, 3D TrueFISP) for MR temperature measurement at 0.23 T, and to compare it to the spin-echo (SE) and spoiled 3D gradient-echo (3D GRE) sequences. The optimal flip angle for the TrueFISP sequence was calculated for the best temperature sensitivity in the image signal from liver tissue, and verified from the images acquired during the thermocoagulation of excised pig liver. Factors influencing the accuracy of the measured temperatures are discussed. The TrueFISP results are compared to the calculated values of optimized SE and 3D GRE sequences. The accuracy of TrueFISP in the liver at 0.23 T, in imaging conditions used during thermocoagulation procedures, is estimated to be ±3.3°C for a voxel of 2.5 × 2.5 × 6 mm3 and acquisition time of 18 s. For the SE and GRE sequences, with similar resolution and somewhat longer imaging time, the uncertainty in the temperature is estimated to be larger by a factor of 2 and 1.2, respectively. Magn Reson Med 47:940,947, 2002. © 2002 Wiley-Liss, Inc. [source] Quantitative contrast-enhanced perfusion measurements of the human lung using the prebolus approachJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2009Markus Oechsner MS Abstract Purpose To investigate dynamic contrast-enhanced MRI (DCE-MRI) for quantification of pulmonary blood flow (PBF) and blood volume (PBV) using the prebolus approach and to compare the results to the global lung perfusion (GLP). Materials and Methods Eleven volunteers were examined by applying different contrast agent doses (0.5, 1.0, 2.0, and 3.0 mL gadolinium diethylene triamine pentaacetic acid [Gd-DTPA]), using a saturation-recovery (SR) true fast imaging with steady precession (TrueFISP) sequence. PBF and PBV were determined for single bolus and prebolus. Region of interest (ROI) evaluation was performed and parameter maps were calculated. Additionally, cardiac output (CO) and lung volume were determined and GLP was calculated as a contrast agent,independent reference value. Results The prebolus results showed good agreement with low-dose single-bolus and GLP: PBF (mean ± SD in units of mL/minute/100 mL) = single bolus 190 ± 73 (0.5-mL dose) and 193 ± 63 (1.0-mL dose); prebolus 192 ± 70 (1.0,2.0-mL dose) and 165 ± 52 (1.0,3.0-mL dose); GLP (mL/minute/100 mL) = 187 ± 34. Higher single-bolus resulted in overestimated values due to arterial input function (AIF) saturation. Conclusion The prebolus approach enables independent determination of appropriate doses for AIF and tissue signal. Using this technique, the signal-to-noise ratio (SNR) from lung parenchyma can be increased, resulting in improved PBF and PBV quantification, which is especially useful for the generation of parameter maps. J. Magn. Reson. Imaging 2009;30:104,111. © 2009 Wiley-Liss, Inc. [source] Measurement of deep gray matter perfusion using a segmented true,fast imaging with steady-state precession (True-FISP) arterial spin-labeling (ASL) method at 3TJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2009Elan J. Grossman MS Abstract Purpose To study the feasibility of using the MRI technique of segmented true,fast imaging with steady-state precession arterial spin-labeling (True-FISP ASL) for the noninvasive measurement and quantification of local perfusion in cerebral deep gray matter at 3T. Materials and Methods A flow-sensitive alternating inversion-recovery (FAIR) ASL perfusion preparation was used in which the echo-planar imaging (EPI) readout was replaced with a segmented True-FISP data acquisition strategy. The absolute perfusion for six selected regions of deep gray matter (left and right thalamus, putamen, and caudate) were calculated in 11 healthy human subjects (six male, five female; mean age = 35.5 years ± 9.9). Results Preliminary measurements of the average absolute perfusion values at the six selected regions of deep gray matter are in agreement with published values for mean absolute cerebral blood flow (CBF) baselines acquired from healthy volunteers using positron emission tomography (PET). Conclusion Segmented True-FISP ASL is a practical and quantitative technique suitable to measure local tissue perfusion in cerebral deep gray matter at a high spatial resolution without the susceptibility artifacts commonly associated with EPI-based methods of ASL. J. Magn. Reson. Imaging 2009;29:1425,1431. © 2009 Wiley-Liss, Inc. [source] Comparison of relative forced expiratory volume of one second with dynamic magnetic resonance imaging parameters in healthy subjects and patients with lung cancer,JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2005Christian Plathow MD Abstract Purpose To assess relative forced expiratory volume in one second (FEV1/vital capacity (VC)) in healthy subjects and patients with a lung tumor using dynamic magnetic resonance imaging (dMRI) parameters. Materials and Methods In 15 healthy volunteers and 31 patients with a non-small-cell lung carcinoma stage I (NSCLC I), diaphragmatic length change (LE1) and craniocaudal (CC) intrathoracic distance change within one second from maximal inspiration (DE1) were divided by total length change (LEtotal, DEtotal) as a surrogate of spirometric FEV1/VC using a true fast imaging with steady-state precession (trueFISP) sequence (TE/TR = 1.7/37.3 msec, temporal resolution = 3 images/second). Influence of tumor localization was examined. Results In healthy volunteers FEV1/VC showed a highly significant correlation with LE1/LEtotal and DE1/DEtotal (r > 0.9, P < 0.01). In stage IB tumor patients, comparing tumor-bearing with the non-tumor-bearing hemithorax, there was a significant difference in tumors of the middle (LE1/LEtotal = 0.63 ± 0.05 vs. 0.73 ± 0.04, DE1/DEtotal = 0.66 ± 0.05 vs. 0.72 ± 0.04; P < 0.05) and lower (P < 0.05) lung region. Stage IA tumor patients showed no significant differences with regard to healthy subjects. Conclusion dMRI is a simple noninvasive method to locally determine LE1/LEtotal and DE1/DEtotal as a surrogate of FEV1/VC in volunteers and patients. Tumors of the middle and lower lung regions have a significant influence on these MRI parameters. J. Magn. Reson. Imaging 2005;21:212,218. © 2005 Wiley-Liss, Inc. [source] Real-time MRI of joint movement with trueFISPJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2002Harald H. Quick MSc Abstract Purpose To develop a technique for dynamic magnetic resonance imaging (MRI) of joint motion based on a combination of real-time TrueFISP (fast imaging with steady state precession) imaging with surface radiofrequency (RF) coils. Materials and Methods The metacarpal, elbow, tarsal, and knee joint of five volunteers and the knees of four patients were examined with a real-time TrueFISP sequence during movement of the joints. Results All examined joints could be assessed under dynamic conditions with high image contrast and high temporal resolution. Conclusion Dynamic MRI of joints with TrueFISP is feasible and can provide information supplemental to static joint examinations. J. Magn. Reson. Imaging 2002;15:710,715. © 2002 Wiley-Liss, Inc. [source] 4D retrospective black blood trueFISP imaging of mouse heartMAGNETIC RESONANCE IN MEDICINE, Issue 5 2009Sylvain Miraux Abstract The purpose of this study was to demonstrate the feasibility of steady-state True fast imaging with steady precession (TrueFISP) four-dimensional imaging of mouse heart at high resolution and its efficiency for cardiac volumetry. Three-dimensional cine-imaging of control and hypoxic mice was carried out at 4.7 T without magnetization preparation or ECG-triggering. The k -space lines were acquired with the TrueFISP sequence (pulse repetition time/echo time = 4/2 ms) in a repeated sequential manner. Retrospective reordering of raw data allowed the reconstruction of 10 three-dimensional images per cardiac cycle. The acquisition scheme used an alternating radiofrequency phase and sum-of-square reconstruction method. Black-blood three-dimensional images at around 200 ,m resolution were produced without banding artifact throughout the cardiac cycle. High contrast to noise made it possible to estimate cavity volumes during diastole and systole. Right and left ventricular stroke volume was significantly higher in hypoxic mice vs controls (20.2 ± 2 vs 15.1 ± 2; P < 0.05, 24.9 ± 2 vs 20.4 ± 2; P < 0.05, respectively). In conclusion, four-dimensional black-blood TrueFISP imaging in living mice is a method of choice to investigate cardiac abnormalities in mouse models. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source] Non-contrast-enhanced perfusion and ventilation assessment of the human lung by means of fourier decomposition in proton MRIMAGNETIC RESONANCE IN MEDICINE, Issue 3 2009Grzegorz Bauman Abstract Assessment of regional lung perfusion and ventilation has significant clinical value for the diagnosis and follow-up of pulmonary diseases. In this work a new method of non-contrast-enhanced functional lung MRI (not dependent on intravenous or inhalative contrast agents) is proposed. A two-dimensional (2D) true fast imaging with steady precession (TrueFISP) pulse sequence (TR/TE = 1.9 ms/0.8 ms, acquisition time [TA] = 112 ms/image) was implemented on a 1.5T whole-body MR scanner. The imaging protocol comprised sets of 198 lung images acquired with an imaging rate of 3.33 images/s in coronal and sagittal view. No electrocardiogram (ECG) or respiratory triggering was used. A nonrigid image registration algorithm was applied to compensate for respiratory motion. Rapid data acquisition allowed observing intensity changes in corresponding lung areas with respect to the cardiac and respiratory frequencies. After a Fourier analysis along the time domain, two spectral lines corresponding to both frequencies were used to calculate the perfusion- and ventilation-weighted images. The described method was applied in preliminary studies on volunteers and patients showing clinical relevance to obtain non-contrast-enhanced perfusion and ventilation data. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source] Quantitative lung perfusion mapping at 0.2 T using FAIR True-FISP MRIMAGNETIC RESONANCE IN MEDICINE, Issue 5 2006Petros Martirosian Abstract Perfusion measurements in lung tissue using arterial spin labeling (ASL) techniques are hampered by strong microscopic field gradients induced by susceptibility differences between the alveolar air and the lung parenchyma. A true fast imaging with steady precession (True-FISP) sequence was adapted for applications in flow-sensitive alternating inversion recovery (FAIR) lung perfusion imaging at 0.2 Tesla and 1.5 Tesla. Conditions of microscopic static field distribution were assessed in four healthy volunteers at both field strengths using multiecho gradient-echo sequences. The full width at half maximum (FWHM) values of the frequency distribution for 180,277 Hz at 1.5 Tesla were more than threefold higher compared to 39,109 Hz at 0.2 Tesla. The influence of microscopic field inhomogeneities on the True-FISP signal yield was simulated numerically. Conditions allowed for the development of a FAIR True-FISP sequence for lung perfusion measurement at 0.2 Tesla, whereas at 1.5 Tesla microscopic field inhomogeneities appeared too distinct. Perfusion measurements of lung tissue were performed on eight healthy volunteers and two patients at 0.2 Tesla using the optimized FAIR True-FISP sequence. The average perfusion rates in peripheral lung regions in transverse, sagittal, and coronal slices of the left/right lung were 418/400, 398/416, and 370/368 ml/100 g/min, respectively. This work suggests that FAIR True-FISP sequences can be considered appropriate for noninvasive lung perfusion examinations at low field strength. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source] Feasibility and performance of breath-hold 3D true-FISP coronary MRA using self-calibrating parallel acquisitionMAGNETIC RESONANCE IN MEDICINE, Issue 1 2004Jaeseok Park Abstract Spatial resolution in 3D breath-hold coronary MR angiography (MRA) is limited by imaging time. The purpose of this work was to investigate the feasibility of improving the spatial resolution of coronary MRA using generalized autocalibrating partially parallel acquisition (GRAPPA) and fast imaging with steady state precession (True-FISP) data acquisition. Coronary data were acquired in 10 healthy volunteers. In five volunteers, the data were fully acquired in k -space and decimated for GRAPPA with an outer reduction factor (ORF) of 2. The coil calibration in GRAPPA was improved by segmented least-squares fitting along the frequency-encoding direction. More than 5% of the total k -space lines were required for the calibration to achieve acceptable artifact suppression despite slightly lower signal-to-noise ratio (SNR). In another five volunteers, coronary data were obtained with both conventional and accelerated data acquisitions in the same imaging time. GRAPPA allowed a submillimeter in-plane resolution, and improved coronary artery definition with an acceptable loss of SNR. In conclusion, 3D breath-hold coronary MRA by GRAPPA and True-FISP is highly feasible. Magn Reson Med 52:7,13, 2004. © 2004 Wiley-Liss, Inc. [source] Rapid cine MRI of the human heart using reconstruction by estimation of lines and inhibition of fold-inMAGNETIC RESONANCE IN MEDICINE, Issue 5 2002Wolfgang G. Rehwald Abstract A fast imaging method is described that yields an approximately six-fold acquisition time reduction relative to conventional techniques. The method involves: 1) acquisition of every sixth k -space line; 2) shifting of acquired k -space lines between odd and even frames; and 3) a single-frame correction image. Reconstruction is achieved by temporal interpolation for k -space lines not acquired combined with subtraction of stationary fold-in artifacts. Seven patients with heart disease and one volunteer were evaluated. SNR was measured in myocardium and the ventricular cavity for both the conventional and new technique. The method is best suited for fast imaging of moving objects confined to a small region within a larger stationary object, such as the heart within the thoracic cavity. It can be implemented in cine and functional imaging sequences and, in principle, in perfusion sequences. Magn Reson Med 47:844,849, 2002. © 2002 Wiley-Liss, Inc. [source] 3D magnetization-prepared true-FISP: A new technique for imaging coronary arteriesMAGNETIC RESONANCE IN MEDICINE, Issue 3 2001Vibhas S. Deshpande Abstract The purpose of this work was to develop an ECG-triggered, segmented 3D true-FISP (fast imaging with steady-state precession) technique to improve the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of breath-hold coronary artery imaging. The major task was to optimize an appropriate magnetization preparation scheme to permit saturation of the epicardial fat signal. An ,/2 preparation pulse was used to speed up the approach to steady-state following a frequency-selective fat-saturation pulse in each heartbeat. The application of dummy cycles was found to reduce the oscillation of the magnetization during data acquisition. The fat saturation and magnetization preparation scheme was validated with simulations and phantom studies. Volunteer studies demonstrated substantially increased SNR (55%) and CNR (178%) for coronary arteries compared to FLASH (fast low-angle shot) with the same imaging time. In conclusion, true-FISP is a promising technique for coronary artery imaging. Magn Reson Med 46:494,502, 2001. © 2001 Wiley-Liss, Inc. [source] Rat lung MRI using low-temperature prepolarized helium-3MAGNETIC RESONANCE IN MEDICINE, Issue 6 2001Frank Kober Abstract The purpose of this study was to evaluate the recently proposed technique of 3He prepolarization at low temperature and high field (Kober et al. Magn Reson Med 1999; 41:1084,1087) for fast imaging of the lung. Helium-3 was cooled to 2.4 K in a magnetic field of 8 Tesla to obtain a polarization of 0.26%. The polarized 3He was warmed up to room temperature and transferred to a rat, with a final polarization of about 0.1%, large enough for acquiring a 3D image of the rat lung in 30 s. Magn Reson Med 45:1130,1133, 2001. © 2001 Wiley-Liss, Inc. [source] Diffuse liver diseases in neonatal and pediatric liver transplant candidates: a pictorial essayCLINICAL TRANSPLANTATION, Issue 4 2010Settimo Caruso Caruso S, Mamone G, Marrone G, Milazzo M, Carollo V, Miraglia R, Maruzzelli L, Minervini MI, Spada M, Riva S, Luca A, Gridelli B. Diffuse liver diseases in neonatal and pediatric liver transplant candidates: a pictorial essay. Clin Transplant 2010: 24: 450,458. © 2009 John Wiley & Sons A/S. Abstract:, A wide spectrum of common and uncommon diffuse liver diseases affecting neonatal and pediatric liver transplant candidates is presented and analyzed using 16 and 64 multi-detector row helical CT (MDCT) and 1.5 T MRI fast imaging. Correlation of imaging findings and explanted liver or histology is illustrated in representative cases. Associated uncommon congenital anomalies are shown. In conclusion, in pediatric liver transplant candidates, 16-MDCT and 1.5 T fast MRI are useful for diagnosis and staging of liver disease, as well as for the evaluation of associated congenital anomalies. [source] | ||||||||||