Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.
College of Engineering, Peking University, Beijing, China.
Magn Reson Imaging. 2019 Sep;61:149-157. doi: 10.1016/j.mri.2019.05.030. Epub 2019 May 23.
To demonstrate the feasibility of using a susceptibility-based MRI technique with multi-echo gradient and spin echo (MEGSE) sequence to achieve simultaneous R2, R2' and R2* measurement and assess skeletal muscle oxygenation alternations in a rabbit model of unilateral artery embolization.
Approved by the local institutional review board for experimental animal studies, nine New Zealand White rabbits were included in this study. The MEGSE sequence consists of embedding a set of gradient echoes around the echo of a single spin-echo sequence using several gradient echoes to collect the magnetization intensity during the formation and attenuation of spin-echo simultaneously after 180° radio frequency pulse. Within-session and between-day tests were conducted to evaluate the reproducibility of this skeletal muscle oxygenation alternations measurement. Furthermore, all the MEGSE scans of skeletal muscle were conducted using a 3-T clinical MRI scanner during resting state (before unilateral artery embolization operation, pre), 1 h after unilateral artery embolization operation (post1) and 2 h after unilateral artery embolization operation (post2) model to verify the feasibility and sensitivity of this method.
The within-session coefficient of variations (CVs) of R2, R2' and R2* measurements were 1.57%, 3.33% and 2.57%, while the between-day CVs of were 1.42%, 5.85% and 2.85%. In all rabbits, the mean R2 decreased significantly from 36.46 ± 1.03 s (pre) to 30.58 ± 2.11 s (post1,**P < 0.01, relative to pre) and 28.62 ± 1.53 s (post2, **P < 0.01, relative to post1), and the mean R2' went up markedly from 9.88 ± 2.14 s (pre) to 16.10 ± 2.74 s (post1, **P < 0.01) and 17.33 ± 2.25 s (post2, *P < 0.05). The mean R2 increased from 43.27 ± 3.75 s (pre) to 47.90 ± 5.08 s (post1, *P < 0.05) and to 48.04 ± 4.42 s (post2, NS, P > 0.05).
This study demonstrates the feasibility of simultaneous R2, R2' and R2* measurement method for the evaluation of skeletal muscle ischemia. Besides, this study indicates the sensitivity of the R2 and R2' compared with R2* and especially the necessity of R2 and R2' measurement for the further evaluation of skeletal muscle ischemia which always causes both edema and hypoxia in a rabbit model of unilateral artery embolization.
利用基于磁化率的 MRI 技术与多回波梯度和自旋回波（MEGSE）序列，同时测量 R2、R2'和 R2*，并评估单侧动脉栓塞兔模型中的骨骼肌氧合变化，以验证该方法的可行性。
本研究经当地机构动物实验审查委员会批准，纳入 9 只新西兰白兔。MEGSE 序列由在单个自旋回波序列的回波周围嵌入一组梯度回波组成，使用多个梯度回波在 180°射频脉冲后同时收集自旋回波形成和衰减期间的磁化强度。进行了单次扫描内和每日间测试，以评估这种骨骼肌氧合变化测量的可重复性。此外，在休息状态（单侧动脉栓塞手术前，预）、单侧动脉栓塞手术后 1 小时（后 1）和 2 小时（后 2）时，使用 3T 临床 MRI 扫描仪对所有骨骼肌 MEGSE 扫描进行了操作，以验证该方法的可行性和灵敏度。
R2、R2'和 R2*测量的单次扫描内变异系数（CV）分别为 1.57%、3.33%和 2.57%，而每日间 CV 分别为 1.42%、5.85%和 2.85%。在所有兔子中，R2 的平均值从 36.46±1.03s（预）显著降低至 30.58±2.11s（后 1，**P<0.01，与预相比）和 28.62±1.53s（后 2，**P<0.01，与后 1 相比），R2' 的平均值从 9.88±2.14s（预）显著升高至 16.10±2.74s（后 1，**P<0.01）和 17.33±2.25s（后 2，*P<0.05）。R2 的平均值从 43.27±3.75s（预）升高至 47.90±5.08s（后 1，*P<0.05）和 48.04±4.42s（后 2，NS，P>0.05）。
本研究证明了用于评估骨骼肌缺血的同时测量 R2、R2'和 R2方法的可行性。此外，本研究表明 R2 和 R2'与 R2相比具有更高的灵敏度，特别是对于单侧动脉栓塞兔模型中经常引起水肿和缺氧的骨骼肌缺血的进一步评估，需要同时测量 R2 和 R2'。
