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1.
Zhaoyang Fan MS Zhuoli Zhang MD PhD Yiu‐Cho Chung PhD Peter Weale BA DCR Sven Zuehlsdorff PhD James Carr MD Debiao Li PhD 《Journal of magnetic resonance imaging : JMRI》2010,31(3):645-654
Purpose:
To evaluate the effectiveness of flow‐sensitive dephasing (FSD) magnetization preparation in improving blood signal suppression of three‐dimensional (3D) turbo spin‐echo (TSE) sequence (SPACE) for isotropic high‐spatial‐resolution carotid arterial wall imaging at 3T.Materials and Methods:
The FSD‐prepared SPACE sequence (FSD‐SPACE) was implemented by adding two identical FSD gradient pulses right before and after the first refocusing 180°‐pulse of the SPACE sequence in all three orthogonal directions. Nine healthy volunteers were imaged at 3T with SPACE, FSD‐SPACE, and multislice T2‐weighted 2D TSE coupled with saturation band (SB‐TSE). Apparent carotid wall‐lumen contrast‐to‐noise ratio (aCNRw‐l) and apparent lumen area (aLA) at the locations with residual‐blood (rb) signal shown on SPACE images were compared between SPACE and FSD‐SPACE. Carotid aCNRw‐l and lumen (LA) and wall area (WA) measured from FSD‐SPACE were compared to those measured from SB‐TSE.Results:
Plaque‐mimicking flow artifacts identified in seven carotids on SPACE images were eliminated on FSD‐SPACE images. The FSD preparation resulted in slightly reduced aCNRw‐l (P = 0.025), but significantly improved aCNR between the wall and rb regions (P < 0.001) and larger aLA (P < 0.001). Compared to SB‐TSE, FSD‐SPACE offered comparable aCNRw‐l with much higher spatial resolution, shorter imaging time, and larger artery coverage. The LA and WA measurements from the two techniques were in good agreement based on intraclasss correlation coefficient (0.988 and 0.949, respectively; P < 0.001) and Bland‐Altman analyses.Conclusion:
FSD‐SPACE is a time‐efficient 3D imaging technique for carotid arterial wall with superior spatial resolution and blood signal suppression. J. Magn. Reson. Imaging 2010;31:645–654. © 2010 Wiley‐Liss, Inc. 相似文献2.
Mihai G Winner MW Raman SV Rajagopalan S Simonetti OP Chung YC 《Journal of magnetic resonance imaging : JMRI》2012,35(2):449-455
Purpose:
To evaluate the use of a T2‐weighted SPACE sequence (T2w‐SPACE) to assess carotid stenosis via several methods and compare its performance with contrast‐enhanced magnetic resonance angiography (ceMRA).Materials and Methods:
Fifteen patients with carotid atherosclerosis underwent dark blood (DB)‐MRI using a 3D turbo spin echo with variable flip angles sequence (T2w‐SPACE) and ceMRA. Images were coregistered and evaluated by two observers. Comparisons were made for luminal diameter, luminal area, degree of luminal stenosis (NASCET: North American Symptomatic Endarterectomy Trial; ECST: European Carotid Surgery Trial, and area stenosis), and vessel wall area. Degree of NASCET stenosis was clinically classified as mild (<50%), moderate (50%–69%), or severe (>69%).Results:
Excellent agreement was seen between ceMRA and T2w‐SPACE and between observers for assessment of lumen diameter, lumen area, vessel wall area, and degree of NASCET stenosis (r > 0.80, P < 0.001). ECST stenosis was consistently higher than NASCET stenosis (48 ± 14% vs. 24 ± 22%, P < 0.001). Area stenosis (72 ± 2%) was significantly higher (P < 0.001) than both ESCT and NASCET stenosis.Conclusion:
DB‐MRI of carotid arteries using T2w‐SPACE is clinically feasible. It provides accurate measurements of lumen size and degree of stenosis in comparison with ceMRA and offers a more reproducible measure of ECST stenosis than ceMRA. J. Magn. Reson. Imaging 2012;449‐455. © 2011 Wiley Periodicals, Inc. 相似文献3.
Georgeta Mihai PhD Yiu‐Cho Chung PhD Ali Merchant MD Orlando P. Simonetti PhD Sanjay Rajagopalan MD 《Journal of magnetic resonance imaging : JMRI》2010,31(2):502-509
Purpose:
To evaluate the feasibility of the dark blood fast spin echo (FSE) T1‐weighted–Sampling Perfection with Application of optimized Contrasts using different flip angle Evolution (T1w‐SPACE) sequence in assessing whole body arterial wall information from the extracranial carotids to the popliteal artery.Materials and Methods:
Twenty‐eight subjects were subjected to noncontrast, dark blood whole body magnetic resonance angiography (DB‐WBMRA) using a T1w‐SPACE sequence optimized for each of the individual stations: carotid artery, thoracic aorta, abdominal aorta, and thigh/superficial femoral artery (SFA). Image quality/vessel wall visualization and the time required to image the four stations were evaluated. Two observers checked the reproducibility of vessel wall depiction by performing quantitative measurements in registered initial and repeat studies (six subjects) of vessel wall and lumen area at 17 locations along the arterial tree.Results:
In 25 of the 28 scanned subjects, dark blood arterial images acquired in approximately 1 hour total imaging time allowed whole body arterial vessel wall visualization. Quantitative measurements showed high correlation between the initial and repeat studies for each of the observers as well as high interobserver reproducibility (r > 0.95; P < 0.01).Conclusion:
DB‐WBMRA using T1w‐SPACE is feasible and can be performed with a high degree of reliability. J. Magn. Reson. Imaging 2010; 31: 502–509. © 2010 Wiley‐Liss, Inc. 相似文献4.
Welsch GH Zak L Mamisch TC Paul D Lauer L Mauerer A Marlovits S Trattnig S 《Journal of magnetic resonance imaging : JMRI》2011,33(1):180-188
Purpose
To evaluate a new isotropic 3D proton‐density, turbo‐spin‐echo sequence with variable flip‐angle distribution (PD‐SPACE) sequence compared to an isotropic 3D true‐fast‐imaging with steady‐state‐precession (True‐FISP) sequence and 2D standard MR sequences with regard to the new 3D magnetic resonance observation of cartilage repair tissue (MOCART) score.Materials and Methods
Sixty consecutive MR scans on 37 patients (age: 32.8 ± 7.9 years) after matrix‐associated autologous chondrocyte transplantation (MACT) of the knee were prospectively included. The 3D MOCART score was assessed using the standard 2D sequences and the multiplanar‐reconstruction (MPR) of both isotropic sequences. Statistical, Bonferroni‐corrected correlation as well as subjective quality analysis were performed.Results
The correlation of the different sequences was significant for the variables defect fill, cartilage interface, bone interface, surface, subchondral lamina, chondral osteophytes, and effusion (Pearson coefficients 0.514–0.865). Especially between the standard sequences and the 3D True‐FISP sequence, the variables structure, signal intensity, subchondral bone, and bone marrow edema revealed lower, not significant, correlation values (0.242–0.383). Subjective quality was good for all sequences (P ≥ 0.05). Artifacts were most often visible on the 3D True‐FISP sequence (P < 0.05).Conclusion
Different isotropic sequences can be used for the 3D evaluation of cartilage repair with the benefits of isotropic 3D MRI, MPR, and a significantly reduced scan time, where the 3D PD‐SPACE sequence reveals the best results. J. Magn. Reson. Imaging 2011;33:180–188. © 2010 Wiley‐Liss, Inc. 相似文献5.
Thomas Henzler MD Olaf Dietrich PhD Radko Krissak MD Tobias Wichmann MSc Titus Lanz PhD Maximilian F. Reiser MD Stefan O. Schoenberg MD Christian Fink MD 《Journal of magnetic resonance imaging : JMRI》2009,30(3):541-546
Purpose
To assess the feasibility of half‐Fourier‐acquisition single‐shot turbo spin‐echo (HASTE) of the lung at 3 Tesla (T) using parallel imaging with a prototype of a 32‐channel torso array coil, and to determine the optimum acceleration factor for the delineation of intrapulmonary anatomy.Materials and Methods
Nine volunteers were examined on a 32‐channel 3T MRI system using a prototype 32‐channel‐torso‐array‐coil. HASTE‐MRI of the lung was acquired at both, end‐inspiratory and end‐expiratory breathhold with parallel imaging (Generalized autocalibrating partially parallel acquisitions = GRAPPA) using acceleration factors ranging between R = 1 (TE = 42 ms) and R = 6 (TE = 16 ms). The image quality of intrapulmonary anatomy and subjectively perceived noise level was analyzed by two radiologists in consensus. In addition quantitative measurements of the signal‐to‐noise ratio (SNR) of HASTE with different acceleration factors were assessed in phantom measurements.Results
Using an acceleration factor of R = 4 image blurring was substantially reduced compared with lower acceleration factors resulting in sharp delineation of intrapulmonary structures in expiratory scans. For inspiratory scans an acceleration factor of 2 provided the best image quality. Expiratory scans had a higher subjectively perceived SNR than inspiratory scans.Conclusion
Using optimized multi‐element coil geometry HASTE‐MRI of the lung is feasible at 3T with acceleration factors up to 4. Compared with nonaccelerated acquisitions, shorter echo times and reduced image blurring are achieved. Expiratory scanning may be favorable to compensate for susceptibility associated signal loss at 3T. J. Magn. Reson. Imaging 2009;30:541–546. © 2009 Wiley‐Liss, Inc. 相似文献6.
Shinya Kojima PhD RT Kazufumi Suzuki MD PhD Masami Hirata RT Hiroyuki Shinohara PhD MD Eiko Ueno PhD MD 《Journal of magnetic resonance imaging : JMRI》2013,37(3):652-659
Purpose:
To assess the ability of magnetic resonance imaging (MRI) to depict the semicircular canals of the inner ear by comparing results from the sampling perfection with application‐optimized contrasts by using different flip angle evolutions (SPACE) sequence with those from the true free induction with steady precession (TrueFISP) sequence.Materials and Methods:
A 1.5‐T MRI system was used to perform an in vivo study of 10 healthy volunteers and 17 patients. A three‐point visual score was employed for assessing the depiction of the semicircular canals and facial and vestibulocochlear nerves and the contrast‐to‐noise ratio (CNR) was computed for the vestibule and pons on images with the SPACE and TrueFIPS sequences.Results:
There were no susceptibility artifact‐related filling defects with the SPACE sequence. However, the TrueFISP sequence showed filling defects for at least one semicircular canal on both sides in seven cases for healthy subjects and in 10 cases for patients. The CNR with the SPACE sequence was significantly higher than with the TrueFISP sequence (P < 0.05). There was no statistically significant difference in depicting the facial and the vestibulocochlear nerves (P = 0.32).Conclusion:
For the depiction of the semicircular canal, the SPACE sequence is superior to the TrueFISP sequence. J. Magn. Reson. Imaging 2013;37:652–659. © 2012 Wiley Periodicals, Inc. 相似文献7.
Hua Guo PhD Wing‐Yan Au MD Jerry S. Cheung BEng Daniel Kim PhD Jens H. Jensen PhD Pek‐Lan Khong MD Queenie Chan PhD Kevin C. Chan BEng Christina Tosti PhD Haiying Tang PhD Truman R. Brown PhD Wynnie W.M. Lam MD Shau‐Yin Ha MD Gary M. Brittenham MD Ed X. Wu PhD 《Journal of magnetic resonance imaging : JMRI》2009,30(2):394-400
Purpose
To investigate the feasibility of measuring myocardial T2 at 3 Tesla for assessment of tissue iron in thalassemia major and other iron overloaded patients.Materials and Methods
A single‐breathhold electrocardiogram‐triggered black‐blood multi‐echo spin‐echo (MESE) sequence with a turbo factor of 2 was implemented at 3 Tesla (T). Myocardial and liver T2 values were measured with three repeated breathholds in 8 normal subjects and 24 patients. Their values, together with the T2* values measured using a breathhold multi‐echo gradient‐echo sequence, were compared with those at 1.5T in the same patients.Results
At 3T, myocardial T2 was found to be 39.6 ± 7.4 ms in normal subjects. In patients, it ranged from 12.9 to 50.1 ms. T2 and T2* were observed to correlate in heart (ρ = 0.93, ρ < 0.0001) and liver (P = 0.95, P < 0.0001). Myocardial T2 and T2* at 3T were also highly correlated with the 1.5T measurements. Preliminary results indicated that myocardial T2 quantitation was relatively insensitive to B1 variation, and reproducible with 3.2% intra‐exam and 3.8% inter‐exam variations.Conclusion
Myocardial T2 quantitation is feasible at 3T. Given the substantially decreased T2* and increased B0 inhomogeneity, the rapid myocardial T2 measurement protocol demonstrated here may present a robust alternative to study cardiac iron overload at 3T. J. Magn. Reson. Imaging 2009;30:394–400. © 2009 Wiley‐Liss, Inc. 相似文献8.
Jun‐Cheng Weng PhD Sheng‐Kai Wu MS Feng‐Yi Yang PhD Win‐Li Lin PhD Wen‐Yih Isaac Tseng MD PhD 《Journal of magnetic resonance imaging : JMRI》2010,31(6):1323-1330
Purpose:
To optimize the timing of contrast‐enhanced magnetic resonance imaging (MRI) that best indicates blood–brain barrier (BBB) disruption induced by focused ultrasound (FUS) along with an ultrasound contrast agent (UCA) and to verify that the contrast‐enhanced spin‐echo MRI sequence can indicate the degree and location of BBB disruption in the presence of hemorrhage better than a gradient‐echo sequence.Materials and Methods:
Sonication was applied to 12 rat brains with four different doses of UCA to cause variable degrees of hemorrhage. Two imaging sequences were performed to acquire T1‐weighted (T1W) images at two time‐points after the administration of a T1‐shortening contrast agent. The contrast enhancement at the sonicated regions was quantified and correlated against Evans blue (EB) staining.Results:
The spin‐echo T1W images at 10 minutes post–contrast enhancement showed the best correlation with EB staining in both quantity of EB extravasation (r = 0.812; P < 0.01) and spatial distribution (r = 0.528, P < 0.01). This capability was more robust than the gradient‐echo sequence.Conclusion:
Our results suggest that contrast‐enhanced T1W spin‐echo sequence acquired in the early phase post–contrast enhancement should be considered to monitor the degree and location of BBB disruption under the possibility of hemorrhage induced by FUS. J. Magn. Reson. Imaging 2010;31:1323–1330. © 2010 Wiley‐Liss, Inc. 相似文献9.
Mürtz P Kaschner M Träber F Kukuk G Skowasch D Gieseke J Schild HH Willinek WA 《Journal of magnetic resonance imaging : JMRI》2012,35(2):456-461
Purpose:
To improve image quality of diffusion‐weighted body magnetic resonance imaging (MRI) with background body signal suppression (DWIBS) at 3.0 T.Materials and Methods:
In 30 patients and eight volunteers, a diffusion‐weighted spin‐echo echo‐planar imaging sequence with short TI inversion recovery (STIR) fat suppression was applied and repeated using slice‐selective gradient reversal (SSGR) and/or dual‐source parallel radiofrequency (RF) transmission (TX). The quality of diffusion‐weighted images and gray scale inverted maximum intensity projections (MIP) were visually assessed by intraindividual comparison with respect to the level of fat suppression and signal homogeneity. Moreover, the contrast between lesions/lymph nodes and background (Clb) was analyzed in the MIP reconstructions.Results:
By combining STIR with SSGR, fat suppression was significantly improved (P < 0.001) and Clb was increased two times. The use of TX allowed the reduction of acquisition time and improved image quality with regard to signal homogeneity (P < 0.001) and fat suppression (P = 0.005).Conclusion:
DWIBS at 3.0 T can be improved by using SSGR and TX. J. Magn. Reson. Imaging 2012;456‐461. © 2011 Wiley Periodicals, Inc. 相似文献10.
Jérôme Hodel Jonathan Silvera Olivier Bekaert Alain Rahmouni Sylvie Bastuji-Garin Alexandre Vignaud Eric Petit Bruno Durning Philippe Decq 《European radiology》2011,21(2):402-410
Objective
To assess the three-dimensional turbo spin echo with variable flip-angle distribution magnetic resonance sequence (SPACE: Sampling Perfection with Application optimised Contrast using different flip-angle Evolution) for the imaging of intracranial cerebrospinal fluid (CSF) spaces. 相似文献11.
Hussain T Clough RE Cecelja M Makowski M Peel S Chowienczyk P Schaeffter T Greil G Botnar R 《Journal of magnetic resonance imaging : JMRI》2011,34(2):279-285
Purpose:
To demonstrate the utility of a “reduced field‐of‐view” (zoom imaging) technique to accelerate free‐breathing, ECG‐triggered, turbo‐spin‐echo black‐blood sequences, which have been previously described to detect subclinical aortic atherosclerosis.Materials and Methods:
Fifteen healthy volunteers underwent MRI of the thoracic and abdominal aorta. Imaging with the conventional full field‐of‐view sequence was compared with zoom imaging. Total scan time, image quality (i.e., contrast‐to‐noise ratio and vessel wall sharpness) and vessel wall thickness were analyzed. A subgroup of 10 volunteers also underwent acceleration of imaging using sensitivity encoding (SENSE) for comparison.Results:
Zoom imaging significantly reduced imaging time from a mean of 41 ± 9 min (conventional imaging) to 15 ± 0.5 min (P < 0.01). There was no difference in image quality between conventional and zoom imaging with respect to CNR (10.1 ± 6 versus 10.1 ± 6) or vessel wall sharpness (38 ± 4% versus 39 ± 4%). Furthermore, Bland Altman plots showed excellent agreement in vessel wall thickness measurements using the two methods. In comparison, SENSE not only reduced CNR but also resulted in underestimation of vessel wall thickness compared with the conventional sequence.Conclusion:
Zoom imaging allows accurate and time‐efficient imaging of the abdominal and thoracic aorta for cardiovascular risk prediction. In this application, it is preferable to SENSE. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc. 相似文献12.
En‐hao Jin MD PhD Tomoaki Ichikawa MD PhD Sukru Mehmet Erturk MD Utaroh Motosugi MD PhD Masaya Hirano MD PhD Tsutomu Araki MD PhD 《Journal of magnetic resonance imaging : JMRI》2009,29(1):217-220
Purpose
To investigate the effectiveness of the calibrated MR hydrometry (CMRH) method for accurately measuring pancreatic secretion.Materials and Methods
All studies were performed on a 1.5‐T MR system using a fat‐suppressed, single‐shot half‐Fourier fast spin‐echo sequence with a standard body coil. A certain volume (20 mL) of saline solution was employed as an extrabody calibrator. The validity of the CMRH method was tested both in vitro and in vivo, and actual and calculated volumes were compared.Results
The in vitro study yielded a high correlation (r = 0.99; P < 0.0001) between the actual volume of saline solution in the imaging field and the calculated volume. In the in vivo study, for all volunteers, there was a very strong and significant positive correlation between the measured signal intensities or calculated volumes and actual volumes (correlation coefficient range: 0.94–0.99; P < 0.0001).Conclusion
This preliminary study shows that CMRH is an effective tool to measure the amount of pancreatic fluid secretion. J. Magn. Reson. Imaging 2009;29:217–220. © 2008 Wiley‐Liss, Inc. 相似文献13.
Ye Qiao PhD David A. Steinman PhD Maryam Etesami MD Alex Martinez‐Marquese BASc Edward G. Lakatta MD Bruce A. Wasserman MD 《Journal of magnetic resonance imaging : JMRI》2013,37(6):1493-1498
Purpose:
To investigate the impact of T2 relaxation of the carotid wall on measurements of its thickness.Materials and Methods:
The common carotid artery wall was imaged using a spin echo sequence acquired at four echo times (17 ms to 68 ms) in 65 participants as part of VALIDATE study. Images were acquired transverse to the artery 1.5 cm proximal to the flow divider. Mean wall thickness, mean wall signal intensity, lumen area, and outer wall area were measured for each echo. Contours were also traced on the image from the fourth echo and then propagated to the images from the preceding echoes. This was repeated using the image from the first echo. Mean wall signal intensity measurements at the four echo times were fit to a mono‐exponential decay curve to derive the mean T2 relaxation time for each set of contours.Results:
Mean wall thickness decreased with increasing echo time, with an average thickness reduction of 8.6% between images acquired at the first and last echo times (TE) (0.93 mm at TE 17 ms versus 0.85 mm at TE 68 ms, P < 0.001). Average T2 relaxation time of the carotid wall decreased by 3% when the smaller contours from the last echo were used, which excluded the outer‐most layer (54.3 ± 7.6 ms versus 52.7 ± 6.6 ms, P = 0.03).Conclusion:
Carotid wall thickness measurements decrease with echo time as expected by the fast T2 relaxation time of the outer‐most layer, namely the adventitia. A short echo time is needed for thickness measurements to include adventitia, which plays an important role in plaque development. J. Magn. Reson. Imaging 2013;37:1493–1498. © 2012 Wiley Periodicals, Inc. 相似文献14.
Jeong-Sik Yu Ki Whang Kim Young Hwan Kim Eun-Kee Jeong Daisy Chien 《Journal of magnetic resonance imaging : JMRI》1998,8(5):1079-1084
The purpose of this study was to compare the relative usefulness of multishot turbo spin echo (TSE) and half-Fourier single-shot turbo spin echo (HASTE) for determination of optimal breath-hold fast T2-weighted technique in terms of lesion detection, lesion-to-liver contrast-to-noise ratio (CNR), and image quality. The images of TSE with and without fat suppression (FS) and of HASTE with and without FS were retrospectively reviewed for 49 patients with 128 lesions. Without FS, TSE and HASTE images allowed depiction of focal hepatic masses (112 of 128, sensitivity = 87.5%) at the same rate. TSE with FS depicted more focal lesions (115 of 128, 89.8%) than HASTE with FS (109 of 128, 85.2%), but the difference was not statistically significant (P > .05). The CNR of each lesion on HASTE sequences was greater (P < .01) than that on TSE sequences. The CNR of hemangioma was distinct from that of solid tumors and cystic lesions in all sequences, and the range of CNR in each group of pathologies overlapped less and were well separated in the HASTE sequences. HASTE sequences produced better image quality with fewer artifacts (P < .0001). The results of this study suggest that HASTE sequences allow differentiation between solid tumors, hemangiomas, and cystic lesions in terms of CNR, producing fewer image artifacts, with acceptable sensitivity in lesion detection. 相似文献
15.
Victor Cuvinciuc Magalie Viallon Isabelle Momjian-Mayor Roman Sztajzel Vitor Mendes Pereira Karl-Olof Lovblad Maria Isabel Vargas 《Neuroradiology》2013,55(5):595-602
Introduction
This study aims to demonstrate the added value of a 3D fat-saturated (FS) T1 sampling perfection with application-optimised contrast using different flip angle evolutions (SPACE) sequence compared to 2D FS T1 spin echo (SE) for the diagnosis of cervical artery dissection.Methods
Thirty-one patients were prospectively evaluated on a 1.5-T MR system for a clinical suspicion of acute or subacute cervical artery dissection with 3D T1 SPACE sequence. In 23 cases, the axial 2D FS T1 SE sequence was also used; only these cases were subsequently analysed. Two neuroradiologists independently and blindly assessed the 2D and 3D T1 sequences. The presence of recent dissection (defined as a T1 hyperintensity in the vessel wall) and the quality of fat suppression were assessed. The final diagnosis was established in consensus, after reviewing all the imaging and clinical data.Results
Overall sensitivity and specificity were 0.929 and 1 for axial T1 SE, and 0.965 and 0.945 for T1 SPACE (P?>?0.05), respectively. The two readers had excellent agreement for both sequences (k?=?1 and 0.8175 for T1 SE and T1 SPACE, respectively; P?>?0.05). The quality of the fat saturation was similar. Very good fat saturation was obtained in the upper neck. Multiplanar reconstructions were very useful in tortuous regions, such as the atlas loop of the vertebral artery or the carotid petrous entry. 3D T1 SPACE sequence has a shorter acquisition time (3 min 25 s versus 5 min 32 s for one T1 SE sequence) and a larger coverage area.Conclusion
3D T1 SPACE sequence offers similar information with its 2D counterpart, in a shorter acquisition time and larger coverage area. 相似文献16.
Kataoka M Kido A Koyama T Isoda H Umeoka S Tamai K Nakamoto Y Maetani Y Morisawa N Saga T Togashi K 《Journal of magnetic resonance imaging : JMRI》2007,25(3):527-534
Purpose
To evaluate the feasibility of MRI of the female pelvis using high‐resolution T2‐weighted imaging (T2WI) and the half‐Fourier acquisition single‐shot turbo spin‐echo (HASTE) technique at 3 Tesla (T) compared to 1.5T, while focusing on the uterine body and cervical anatomy.Materials and Methods
A total of 19 healthy women underwent pelvic MR scans on 3T and 1.5T scanners. Axial and sagittal T2W (voxel size of 0.6 × 0.8 × 2 mm) and sagittal HASTE images were obtained. The images were evaluated qualitatively for overall image quality, contrast in the uterine zonal appearance and cervical structure, image inhomogeneity, and artifacts. A quantitative evaluation was performed regarding zonal contrast and image inhomogeneity.Results
On T2WI, the image contrast in the uterine cervix and vagina were significantly higher at 3T than at 1.5T, although there was no significant difference in the overall image quality or contrast in the uterine zonal appearance. Image inhomogeneity was more prominent at 3T, and motion artifact was more severe at 1.5T.Conclusion
Our results suggest that MRI of the female pelvis at 3T may potentially provide excellent images of the uterine cervix on high‐resolution T2WI. New techniques to reduce inhomogeneity are thus called for. J. Magn. Reson. Imaging 2007;25:527–534. © 2007 Wiley‐Liss, Inc. 相似文献17.
Masoud Shiehmorteza MD Claude B. Sirlin MD Tanya Wolfson MA Anthony Gamst PhD Andre E. Soumekh BS Shay P. Heaton BS Chad A. Kohl MD Nicholas Pinto RT Mark Bydder PhD 《Journal of magnetic resonance imaging : JMRI》2009,30(3):547-553
Purpose
To show the signal intensity varies with shot number in diffusion‐weighted (DW) echo‐planar imaging (EPI) and affects apparent diffusion coefficient (ADC) calculation.Materials and Methods
This prospective study was performed on 35 adult patients and 20 volunteers. Measurements were made on a 3T scanner using a breathhold DW spin‐echo EPI (SE EPI) sequence. Three protocols were used: A) eight consecutive shots at a fixed b‐value of 0 seconds/mm2 with TR = 1000 and 3000 msec; B) seven consecutive shots at b‐values = 0, 1000, 750, 500, 250, 100, 0 seconds/mm2 (in that order) with TR = 3500 msec; and C) seven consecutive shots (as in B) with TR = 1000, 1750, and 7000 msec.Results
For protocol A, signal intensity decreased significantly from the first to second shot (P<0.0001) and thereafter remained constant. For protocol B, the ADC depended on which b = 0 seconds/mm2 image was used. Using the first b = 0 seconds/mm2, the mean ADC was 15% higher than using the second b = 0 seconds/mm2 (P<0.0001). For protocol C, the difference between ADC using the first b = 0 seconds/mm2 and the second b = 0 seconds/mm2 decreased as the TR increased.Conclusion
The signal intensity can vary with shot number in SE EPI. For TR ≥ 3000 msec, steady‐state is attained after one shot. Using data acquired prior to steady‐state confounds the calculation of ADC values. J. Magn. Reson. Imaging 2009;30:547–553. © 2009 Wiley‐Liss, Inc. 相似文献18.
Kim KA Herigault G Kim MJ Chung YE Hong HS Choi SY 《Journal of magnetic resonance imaging : JMRI》2011,33(1):160-166
Purpose
To compare the image quality of two variants of a three‐dimensional (3D) gradient echo sequence (GRE) for hepatic MRI.Materials and Methods
Thirty‐nine patients underwent hepatic MRI on a 3.0 Tesla (T) magnet (Intera Achieva; Philips Medical Systems). The clinical protocol included two variants of a 3D GRE with fat suppression: (i) a “centric” approach, with elliptical centric k‐space ordering and (ii) an “enhanced” approach using linear sampling and partial Fourier in both the slice and phase encoding direction. “Centric” and “Enhanced” 3D GRE images were obtained both precontrast (n = 32) and after gadoxetic acid injection (n = 39). Two reviewers jointly reviewed MR images for anatomic sharpness, overall contrast, homogeneity, and absence of artifacts. The liver‐to‐lesion signal difference ratio (SDR) was measured. Paired sample Wilcoxon test and paired t‐tests were used.Results
Enhanced 3D GRE images performed better than centric 3D GRE images with respect to anatomic sharpness (P = 0.0156), overall contrast (P = 0.0195), homogeneity (P < 0.0001), and absence of artifacts (P = 0.0003) on precontrast images. For postcontrast MRI, enhanced 3D GRE images showed better quality in terms of overall contrast (P = 0.0195), homogeneity (P < 0.0001), and absence of artifacts (P = 0.009). Liver‐to‐lesion SDR on enhanced 3D GRE images (0.48 ± 0.13) was significantly higher than that of conventional 3D GRE images (0.40 ± 0.19, P = 0.0004) on postcontrast images, but not on precontrast images.Conclusion
The enhanced 3D GRE sequence available on our scanner provided better hepatic image quality than the centric variant, without compromising lesion contrast. J. Magn. Reson. Imaging 2011;33:160–166. © 2010 Wiley‐Liss, Inc. 相似文献19.
Stevens KJ Wallace CG Chen W Rosenberg JK Gold GE 《Journal of magnetic resonance imaging : JMRI》2011,33(4):908-915
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. J. Magn. Reson. Imaging 2011;33:908–915. © 2011 Wiley‐Liss, Inc. 相似文献20.