Home About us Contact
|
Home About us Contact | ||
|
|
||
Turbo Spin Echo (turbo + spin_echo)
Selected Abstracts3D flow-independent peripheral vessel wall imaging using T2 -prepared phase-sensitive inversion-recovery steady-state free precessionJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2010Jingsi Xie BS Abstract Purpose: To develop a 3D flow-independent peripheral vessel wall imaging method using T2 -prepared phase-sensitive inversion-recovery (T2PSIR) steady-state free precession (SSFP). Materials and Methods: A 3D T2 -prepared and nonselective inversion-recovery SSFP sequence was designed to achieve flow-independent blood suppression for vessel wall imaging based on T1 and T2 properties of the vessel wall and blood. To maximize image contrast and reduce its dependence on the inversion time (TI), phase-sensitive reconstruction was used to restore the true signal difference between vessel wall and blood. The feasibility of this technique for peripheral artery wall imaging was tested in 13 healthy subjects. Image signal-to-noise ratio (SNR), wall/lumen contrast-to-noise ratio (CNR), and scan efficiency were compared between this technique and conventional 2D double inversion recovery , turbo spin echo (DIR-TSE) in eight subjects. Results: 3D T2PSIR SSFP provided more efficient data acquisition (32 slices and 64 mm in 4 minutes, 7.5 seconds per slice) than 2D DIR-TSE (2,3 minutes per slice). SNR of the vessel wall and CNR between vessel wall and lumen were significantly increased as compared to those of DIR-TSE (P < 0.001). Vessel wall and lumen areas of the two techniques are strongly correlated (intraclass correlation coefficients: 0.975 and 0.937, respectively; P < 0.001 for both). The lumen area of T2PSIR SSFP is slightly larger than that of DIR-TSE (P = 0.008). The difference in vessel wall area between the two techniques is not statistically significant. Conclusion: T2PSIR SSFP is a promising technique for peripheral vessel wall imaging. It provides excellent blood signal suppression and vessel wall/lumen contrast. It can cover a 3D volume efficiently and is flow- and TI-independent. J. Magn. Reson. Imaging 2010;32:399,408. © 2010 Wiley-Liss, Inc. [source] Initial feasibility of a multi-station high resolution three-dimensional dark blood angiography protocol for the assessment of peripheral arterial diseaseJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2009Georgeta Mihai PhD Abstract Purpose To evaluate the feasibility of a multi-station three dimensional (3D) T1-weighted turbo spin echo (TSE) dark-blood Sampling Perfection with Application optimized Contrasts using different flip angle Evolution sequence (T1w-SPACE), to assess aorta, iliac, and superficial femoral (SFA) arteries (inflow vessels) by comparing it with a multi-station contrast enhanced MR angiography (CE-MRA) with identical resolution. Materials and Methods A total of 6 volunteers and 14 peripheral arterial disease (PAD) patients were included in the study. Abdominal and thigh T1w-SPACE and lower leg time-resolved MRA (TR-MRA) with low dose contrast were followed by 3-station CE-MRA. Quantitative measurements of lumen area at 17 locations from T1w-SPACE and CE-MRA were obtained. Additionally, vessel wall areas at the same locations were obtained from the T1w-SPACE images. Results Quantitative comparison of lumen areas with T1w-SPACE and CE-MRA revealed strong correlation between the two techniques and strong inter-observer agreement for each of the two imaging methods (r > 0.9; P < 0.001). Localized vessel wall area measurements obtained in PAD patients were significantly greater compared with those obtained in normal volunteers (mean difference 43.75 ± 12.46 mm2; P < 0.001). Stenosis severity obtained from T1w-SPACE localized measurements showed significant arterial area stenosis in PAD patients. Conclusion T1w-SPACE imaging of inflow vessels is feasible, and in addition to CE-MRA has the ability to assess atherosclerotic plaque and vascular remodeling. J. Magn. Reson. Imaging 2009;30:785,793. © 2009 Wiley-Liss, Inc. [source] Conspicuity of zones of ablation after radiofrequency ablation in porcine livers: Comparison of an extracellular and an SPIO contrast agentJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2008Christopher Bangard MD Abstract Purpose To compare conspicuity of zones of ablation on nonenhanced, gadopentetate dimeglumine-(Gd-DTPA) and ferucarbotran-(SPIO)-enhanced magnetic resonance (MR) images. Materials and Methods In all, 33 radiofrequency ablations (RFA) were performed in 17 healthy porcine livers at 1.5T MR imaging 1 day and 2 and 4 weeks after RFA: T2-weighted (w) ultra turbo spin echo (UTSE), proton density (PD)-w UTSE, T1-w gradient echo (GRE) pre- and 5 minutes postcontrast administration, dynamic T1-w GRE during Gd-DTPA (Magnevist) or SPIO (Resovist) administration, T2-w UTSE, and PD-w UTSE sequences 10 minutes after SPIO administration. Regions of interest (ROIs) for contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) were drawn in consensus by two radiologists. Results PD-w SPIO-enhanced images (23.5 ± 5.5) showed higher liver-to-lesion CNR than T1-w GRE Gd-DTPA-enhanced images (13.5 ± 6.1) 1 day after RFA (P , 0.05). At all other timepoints, liver-to-lesion CNR of PD-w and T2-w SPIO-enhanced images did not differ significantly from T1-w GRE Gd-DTPA-enhanced images (P , 0.05). Nonenhanced T2-w images revealed lower liver-to-lesion CNR (7.0 ± 7.5/6.5 ± 5.9/6.8 ± 5.0, 1 day/2 weeks/4 weeks, respectively) than T2-w SPIO-enhanced (17.4 ± 4.8/15.3 ± 4.5/14.2 ± 5.7), PD-w SPIO-enhanced (23.5 ± 5.5/16.9 ± 3.6, 1 day/2 weeks), and T1-w Gd-DTPA-enhanced (15.3 ± 3.6/12.7 ± 3.5, 2/4 weeks) images (P , 0.05). Liver-to-lesion CNR of SPIO-enhanced dynamic T1-w GRE images after 30, 80, 150, and 240 seconds did not change significantly over time (P , 0.05). Conclusion One day after RFA lesion conspicuity on PD-w ferucarbotran-enhanced images is better than on T1-w GRE Gd-DTPA-enhanced images. At all other timepoints, ferucarbotran is not superior to gadolinium. Ferucarbotran- and gadolinium-enhanced images improve lesion conspicuity compared with nonenhanced T2-w images at all timepoints. J. Magn. Reson. Imaging 2008;28:263,270. © 2008 Wiley-Liss, Inc. [source] Improvement in B1-inhomogeneity artifacts in the abdomen at 3T MR imaging using a radiofrequency cushionJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2008Kendra M. Franklin MD Abstract Purpose To determine the impact of a radiofrequency (RF) cushion on abdominal image quality at 3T. Materials and Methods Twenty volunteers were scanned on a 3T system with and without the use of an RF cushion. T2-weighted HASTE and true-FISP sequences were used for coronal imaging, and each sequence was performed with and without integrated parallel acquisition techniques (iPAT). Additionally, axial T2-weighted HASTE and true-FISP imaging without iPAT was performed. The effect on image quality was assessed by subjectively evaluating the presence and severity of RF inhomogeneity artifacts by two independent readers in a side-by-side comparison with a 5-point differential receiver operating characteristics curve. Results Both readers considered the quality of HASTE images acquired with the RF cushion to be significantly better in all cases. The quality of true-FISP images did not benefit significantly from the use of the RF cushion in any case. Conclusion The RF cushion significantly improves image quality for abdominal imaging at 3T by reducing or eliminating B1-inhomogenity artifacts. This improved image quality is seen on turbo spin echo-based T2-weighted imaging such as HASTE but does not apply to gradient echo-based T2-weighted imaging such as the true-FISP sequence. J. Magn. Reson. Imaging 2008. © 2008 Wiley-Liss, Inc. [source] Methods and applications of diffusion imaging of vertebral bone marrowJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2006José G. Raya MSc Abstract Diffusion-weighted imaging (DWI) is an MRI technique that is sensitive to random water movements at spatial scales far below typical MRI voxel dimensions. DWI is a valuable tool for the diagnoses of diseases that involve alterations in water mobility. In the spine, DWI has proven to be a highly useful method for the differential diagnosis of benign and malignant compression fractures. In these pathologies, the microscopic structure of bone marrow is altered in a very different ways, leading to different water mobility, which can be depicted by DWI. Most of the pulse sequences developed for MRI can be adapted for DWI. However, these DWI-adapted sequences are frequently affected by artifacts, mostly caused by physiological motion. Therefore, the introduction of additional correction techniques, or even the development of new sequences is necessary. The first part of this article describes the principles of DWI and the sequences used for DWI of the spine: spin echo (SE), turbo spin echo (TSE), single-shot echo planar imaging (EPI), and steady-state free precession (SSFP) sequences. In the second part, clinical applications of DWI of the spinal bone marrow are extensively discussed. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [source] Routine clinical brain MRI sequences for use at 3.0 TeslaJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2005Hanzhang Lu PhD Abstract Purpose To establish image parameters for some routine clinical brain MRI pulse sequences at 3.0 T with the goal of maintaining, as much as possible, the well-characterized 1.5-T image contrast characteristics for daily clinical diagnosis, while benefiting from the increased signal to noise at higher field. Materials and Methods A total of 10 healthy subjects were scanned on 1.5-T and 3.0-T systems for T1 and T2 relaxation time measurements of major gray and white matter structures. The relaxation times were subsequently used to determine 3.0-T acquisition parameters for spin-echo (SE), T1 -weighted, fast spin echo (FSE) or turbo spin echo (TSE), T2 -weighted, and fluid-attenuated inversion recovery (FLAIR) pulse sequences that give image characteristics comparable to 1.5 T, to facilitate routine clinical diagnostics. Application of the routine clinical sequences was performed in 10 subjects, five normal subjects and five patients with various pathologies. Results T1 and T2 relaxation times were, respectively, 14% to 30% longer and 12% to 19% shorter at 3.0 T when compared to the values at 1.5 T, depending on the region evaluated. When using appropriate parameters, routine clinical images acquired at 3.0 T showed similar image characteristics to those obtained at 1.5 T, but with higher signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), which can be used to reduce the number of averages and scan times. Recommended imaging parameters for these sequences are provided. Conclusion When parameters are adjusted for changes in relaxation rates, routine clinical scans at 3.0 T can provide similar image appearance as 1.5 T, but with superior image quality and/or increased speed. J. Magn. Reson. Imaging 2005;22:13,22. © 2005 Wiley-Liss, Inc. [source] Comparison between three-dimensional volume-selective turbo spin-echo imaging and two-dimensional ultrasound for assessing carotid artery structure and functionJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2005Lindsey A. Crowe PhD Abstract Purpose To compare a volume-selective three-dimensional turbo spin echo (TSE) technique with ultrasound (US) for assessing carotid artery wall structure and function. Materials and Methods A three-dimensional volume-selective TSE technique was used to image the carotid artery in 10 healthy subjects and five hypertensive subjects (each of whom were scanned three times while they received different hypertension treatments). Lumen and wall area were measured on MR images. Two-dimensional US measurements of the intima-media thickness (IMT) and lumen diameter were taken in three orientations through a single cross section. The lumen area change over the cardiac cycle was used to determine distension. For validation, a Bland-Altman analysis was used to compare the vessel wall and lumen areas measured by three-dimensional MRI volumes with those obtained by US scans. Results Agreement between the two methods was found. The mean difference in distension between US and MRI was 1.2% (±5.1%). For the wall area measurements, good agreement was shown, but there was a systematic difference due to the visualization of the adventitia by MRI. Both techniques offer an easy way to objectively measure lumen indices. MRI can provide the complete circumference over the length of a vessel, while US is flexible and relatively inexpensive. The application of US is limited, however, when subjects are poorly echogenic. A difference between hypertensive and healthy subjects was found. Conclusion There was a good agreement between MRI and the clinically established two-dimensional US method. The MRI method has the advantage of providing increased vessel coverage, which permits one to assess localized abnormalities without assuming vessel uniformity. J. Magn. Reson. Imaging 2005;21:282,289. © 2005 Wiley-Liss, Inc. [source] In vivo detection of hemorrhage in human atherosclerotic plaques with magnetic resonance imaging,JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2004Vincent C. Cappendijk MD Abstract Purpose To investigate the performance of high-resolution T1-weighted (T1w) turbo field echo (TFE) magnetic resonance imaging (MRI) for the identification of the high-risk component intraplaque hemorrhage, which is described in the literature as a troublesome component to detect. Materials and Methods An MRI scan was performed preoperatively on 11 patients who underwent carotid endarterectomy because of symptomatic carotid disease with a stenosis larger than 70%. A commonly used double inversion recovery (DIR) T1w turbo spin echo (TSE) served as the T1w control for the T1w TFE pulse sequence. The MR images were matched slice by slice with histology, and the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the MR images were calculated. Additionally, two readers, who were blinded for the histological results, independently assessed the MR slices concerning the presence of intraplaque hemorrhage. Results More than 80% of the histological proven intraplaque hemorrhage could be detected using the TFE sequence with a high interobserver agreement (Kappa = 0.73). The TFE sequence proved to be superior to the TSE sequence concerning SNR and CNR, but also in the qualitative detection of intraplaque hemorrhage. The false positive TFE results contained fibrous tissue and were all located outside the main plaque area. Conclusion The present study shows that in vivo high-resolution T1w TFE MRI can identify the high-risk component intraplaque hemorrhage with a high detection rate in patients with symptomatic carotid disease. Larger clinical trials are warranted to investigate whether this technique can identify patients at risk for an ischemic attack. J. Magn. Reson. Imaging 2004;20:105,110. © 2004 Wiley-Liss, Inc. [source] Magnetic Resonance Imaging in Patients Diagnosed With Papilledema: A Comparison of 6 Different High-Resolution T1- and T2(*)-Weighted 3-Dimensional and 2-Dimensional SequencesJOURNAL OF NEUROIMAGING, Issue 2 2002Johannes Seitz MD ABSTRACT Purpose. To evaluate visualization and signal characteristics of macroscopic changes in patients with ophthalmologically stated papilledema and to find a suitable high-resolution magnetic resonance imaging (MRI) protocol. Method. Nine consecutive patients with 12 ophthalmologically stated papilledemas underwent MRI of the head and orbits, which consisted of the following high-resolution sequences: 3-dimensional (3D), T2*-weighted (T2*w) constructive interference in steady-state sequence (CISS); 3D, T1-weighted (T1w) magnetization prepared-rapid gradient echo sequence (MP-RAGE) (with and without intravenous contrast medium); transverse 3D and 2-dimensional (2D) (2mm), T2-weighted (T2w) turbo spin echo (TSE); transverse 2D (2mm), contrast-enhanced T1w TSE with fat-suppression technique; and transverse 2D (5mm), T2w TSE. A quantitative and qualitative evaluation of the papilla, optic nerve, optic nerve sheath, optic chiasm, and the brain was performed. The 6 high-resolution sequences were compared. Results. The elevation of the optic disc into the optic globe in ophthalmologically stated papilledema was best visualized in T2w, 3D CISS sequence. The pathological contrast enhancement was best seen in T1w contrast-enhanced 2D TSE sequence with fat-suppression technique. The mean width of the optic nerve sheath directly behind the globe was 7.54 mm (± 1.05 mm) in the pathological eyes, compared to 5.52 mm (± 1.11 mm) in the normal eyes. In all patients, the cerebral indices calculated showed no signs of increased intracranial pressure or other abnormalities changing the volume of the brain or ventricles. The contrast of the orbital fat versus the optic nerve sheath, the optic nerve sheath versus the surrounding cerebrospinal fluid (CSF), the surrounding CSF versus the optic nerve, the optic chiasm versus the CSF, and the optic papilla versus the optic globe were best visualized in the 3D, T2*w CISS sequence. An enhancement of the swollen optic nerve head was best seen in all 12 cases in the T1w contrast-enhanced 2D TSE sequence with fat-suppression technique. Conclusion. An MRI protocol consisting of a 5-mm transverse T2w TSE sequence; a T2*w, 3D CISS sequence; a T1w, 3D MP-RAGE sequence with and without contrast medium; and a transverse T1w, (2-mm) 2D TSE sequence with fat-suppression technique with intravenous contrast medium is suitable to visualize the macroscopic changes in papilledema. In addition, this combination is an excellent technique for the examination of the orbits and the brain. [source] Imaging the changes in renal T1 induced by the inhalation of pure oxygen: A feasibility studyMAGNETIC RESONANCE IN MEDICINE, Issue 4 2002Richard A. Jones Abstract The effect of the inhalation of pure oxygen on the kidney was evaluated by measuring monoexponential T1 and T relaxation times in nine volunteers using a multiple-shot turbo spin echo and multiple echo gradient echo sequences, respectively. The T1 of the renal cortex decreased significantly when breathing pure oxygen as compared to normoxia (from 882 ± 59 to 829 ± 70 msec, P < 0.05), while that of the renal medulla was unchanged. No significant changes were seen in the T of either compartment. Dynamic imaging using an inversion recovery sequence with an optimized inversion time typically produced signal changes of 20% in the renal cortex. Studies to assess if oxygen-induced changes in flow contributed to this effect showed that the flow contribution was not significant. Although longer inversion times (880 ms) produced optimal contrast, acceptable contrast was also obtained at shorter inversion times (450 msec) in the renal cortex, spleen, and lung, with the latter being of opposite polarity to the other two tissues, implying a shorter parenchymal T1 than previously reported in the literature. The results are consistent with oxygen acting as an intravascular contrast agent which induces a shortening of T1 in the arterial blood volume. Magn Reson Med 47:728,735, 2002. © 2002 Wiley-Liss, Inc. [source] | ||||||||||