Optimization of parallel acquisition technique in 3D TOF MRA of head with 8-receiving channels phased-array coil in 1.5T MR system: A phantom study / 中国医学影像技术

Objective: To explore the application value of array spatial sensitivity encoding technique (ASSET) in 3D TOF MRA of head with 8-receiving channels phased-array coil in 1.5T MR system and the methods to eliminate image artifact, in order to optimize the scanning protocol of 3D TOF MRA. Methods Using the standard model of head for MRI, scanning of 3D TOF MRA was performed combining with different ASSET reduce factor (R value), phase FOV (FOVp), scanning FOV (FOVs) and calibration FOV (FOVc; 30 cm×30 cm in group A, 35 cm×35 cm in group B and 40 cm×40 cm in group C). Then the shortest distance between bilateral wrapped artifacts (D) and SNR was measured, and the acquisition time (TA) of each group and resolution on phase direction (Rp) were recorded. Then the optimized parameters were estimated. Results ASSET artifact became serious as FOVc increased, the distance between wrapped artifact broadened to disappear as FOVs and FOVp increased and R value decreased. TA unchanged as R value and FOVp unchanged. When R value fixed, SNR increased as FOVs and FOVp increased. SNR decreased as R value increased when FOVs and FOVp fixed. Rp decreased as FOVs and FOVp increased. Conclusion ASSET scanning needs right R value matching with corresponding FOVc, FOVs and FOVp. The optimization parameters under the above mentioned condition for 3D TOF MRA of head are FOVc with 35 cm×35 cm, FOVs with 28 cm×28 cm, FOVp with 0.75 and R value with 1.25.

Preliminary application of optimized temporal parallel acquisition technique real-time cine sequence in cardiac MRI in arrhythmia patients / 中国医学影像技术

Objective To observe the value of optimized temporal parallel acquisition technique (TPAT) sequence in evaluating cardiac structure and function in arrhythmia patients.Methods Totally 33 arrhythmia patients (arrhythmia group) and 48 normal rhythm subjects (normal group) underwent cardiac MRI with conventional cine (balanced steadystate free-precession [bSSFP]) sequence and optimized TPAT sequence.Myocardial thickness,cardiac function,myocardial strain parameters of left ventricle and image quality of 2 sequences were compared in the two groups,respectively.Results In arrhythmia group,there was statistical difference of myocardial thickness in 12 myocardial segments between the 2 sequences (all P ＜ 0.05),as well as peak and average values of myocardial radial and circumferential strain (all P＜0.05).In normal group,there was no statistical difference of myocardial thickness and stain parameters between the 2 sequences (all P＞0.05).Additionally,no statistical difference of cardiac function was found between the 2 sequences in two groups (all P＞0.05).In arrhythmia group,the image quality of optimized TPAT sequence was better than that of bSSFP sequence (P＜0.05).Conclusion For arrhythmia patients,optimized TPAT cine sequence could improve image quality of cardiac MRI.

Assessment of Left Ventricular Function with Single Breath-Hold Magnetic Resonance Cine Imaging in Patients with Arrhythmia

PURPOSE: To evaluate quantification results of single breath-hold (SBH) magnetic resonance (MR) cine imaging compared to results of conventional multiple breath-hold (MBH) technique for left ventricular (LV) function in patients with cardiac arrhythmia. MATERIALS AND METHODS: MR images of patients with arrhythmia who underwent MBH and SBH cine imaging at the same time on a 1.5T MR scanner were retrospectively reviewed. Both SBH and MBH cine imaging were performed with balanced steady state free precession. SBH scans were acquired using temporal parallel acquisition technique (TPAT). Fifty patients (65.4 ± 12.3 years, 72% men) were included. End-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), myocardial mass, and LV regional wall motion were evaluated. RESULTS: EF, myocardial mass, and regional wall motion were not significantly different between SBH and MBH acquisition techniques (all P-values > 0.05). EDV, ESV, and SV were significant difference between the two techniques. These parameters for SBH cine imaging with TPAT tended to lower than those in MBH. EF and myocardial mass of SBH cine imaging with TPAT showed good correlation with values of MBH cine imaging in Passing-Bablok regression charts and Bland-Altman plots. However, SBH imaging required significantly shorter acquisition time than MBH cine imaging (15 ± 7 sec vs. 293 ± 104 sec, P < 0.001). CONCLUSION: SBH cine imaging with TPAT permits shorter acquisition time with assessment results of global and regional LV function comparable to those with MBH cine imaging in patients with arrhythmia.

Peripheral contrast-enhanced MRA at open-bore 3 T, with low dose contrast agent / 安徽医科大学学报

Objective To investigate the feasibility with low dose contrast agent in patients undergoing peripheral magnetic resonance angiography with high spatial resolution at open-bore 3 T scanner. Methods Images of MRA were assessed separately by two radiologists. And the images of DSA were assessed by one radiologist. The degree of the two interobservers' consensus for detection of arterial stenosis was determined by calculating the Kappa coef-ficient. Spearman rank correlation coefficient was used for revealing the relationship between contrast-enhanced MR angiography and DSA,in terms of categories of stenosis. Results For the degree of vessel stenosis, Cohen' s statis-tics revealed excellent agreement between the two observers. There was a significant correlation between DSA and MRA(P<0. 05). Conclusion At this open-bore 3 T scanner, high spatial resolution peripheral magnetic reso-nance angiography is achieved with low dose contrast agent.