Sharafi Azadeh, Medina Katherine, Zibetti Marcelo W V, Rao Smita, Cloos Martijn A, Brown Ryan, Regatte Ravinder R
Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, New York, New York, USA.
Department of Physical Therapy, New York University, New York, New York, USA.
Magn Reson Med. 2021 Jul;86(1):372-381. doi: 10.1002/mrm.28704. Epub 2021 Feb 8.
To develop a novel MR-fingerprinting (MRF) pulse sequence that is insensitive to and B imperfections for simultaneous T , T , and T relaxation mapping.
We implemented a totally balanced spin-lock (TB-SL) module to encode T relaxation into an existing MRF framework that encoded T and T . The spin-lock module used two 180° pulses with compensatory phases to reduce T sensitivity to B and B inhomogeneities. We compared T measured using TB-SL MRF in Bloch simulations, model agar phantoms, and in vivo experiments to those with a self-compensated spin-lock preparation module (SC-SL). The TB-SL MRF repeatability was evaluated in maps acquired in the lower leg skeletal muscle of 12 diabetic peripheral neuropathy patients, scanned two times each during visits separated by about 30 days.
The phantom relaxation times measured with TB-SL and SC-SL MRF were in good agreement with reference values in regions with low B inhomogeneities. Compared with SC-SL, TB-SL MRF showed in experiments greater robustness against severe B inhomogeneities and in Bloch simulations greater robustness against B and B . We measured with TB-SL MRF an average T = 950.1 ± 28.7 ms, T = 26.0 ± 1.2 ms, and T = 31.7 ± 3.2 ms in skeletal muscle across patients. Bland-Altman analysis demonstrated low bias between TB-SL and SC-SL MRF and between TB-SL MRF maps acquired in two visits. The coefficient of variation was less than 3% for all measurements.
The proposed TB-SL MRF sequence is fast and insensitive to and B imperfections. It can simultaneously map T , T , T , and in a single scan and can potentially be used to study muscle composition.
开发一种新型的磁共振指纹（MRF）脉冲序列，该序列对B0和B1不完善不敏感，用于同时进行T1、T2和T2*弛豫映射。
我们实施了一个完全平衡的自旋锁定（TB-SL）模块，将T1弛豫编码到现有的编码T2和T2*的MRF框架中。自旋锁定模块使用两个具有补偿相位的180°脉冲，以降低T1对B0和B1不均匀性的敏感性。我们在Bloch模拟、模型琼脂体模和体内实验中，将使用TB-SL MRF测量的T1与使用自补偿自旋锁定准备模块（SC-SL）测量的T1进行比较。在12名糖尿病周围神经病变患者的小腿骨骼肌中采集的图谱中评估TB-SL MRF的重复性，在相隔约30天的两次就诊期间分别进行两次扫描。
在B0不均匀性较低的区域，用TB-SL和SC-SL MRF测量的体模弛豫时间与参考值高度一致。与SC-SL相比，TB-SL MRF在实验中对严重的B0不均匀性表现出更高的稳健性，在Bloch模拟中对B0和B1表现出更高的稳健性。我们用TB-SL MRF在患者的骨骼肌中测量的平均T1 = 950.1 ± 28.7 ms，T2 = 26.0 ± 1.2 ms，T2* = 31.7 ± 3.2 ms。Bland-Altman分析表明，TB-SL和SC-SL MRF之间以及两次就诊时采集的TB-SL MRF图谱之间的偏差较低。所有测量的变异系数均小于3%。
所提出的TB-SL MRF序列速度快，对B0和B1不完善不敏感。它可以在单次扫描中同时映射T1、T2、T2*和，并且有可能用于研究肌肉组成。
