Mastropietro Alfonso, Porcelli Simone, Cadioli Marcello, Rasica Letizia, Scalco Elisa, Gerevini Simonetta, Marzorati Mauro, Rizzo Giovanna
Istituto di Bioimmagini e Fisiologia Molecolare, Consiglio Nazionale delle Ricerche, Segrate, Italy.
Dipartimento di Neuroradiologia, Ospedale San Raffaele, Milan, Italy.
NMR Biomed. 2018 Jun;31(6):e3922. doi: 10.1002/nbm.3922. Epub 2018 Apr 10.
The main aim of this paper was to propose triggered intravoxel incoherent motion (IVIM) imaging sequences for the evaluation of perfusion changes in calf muscles before, during and after isometric intermittent exercise. Twelve healthy volunteers were involved in the study. The subjects were asked to perform intermittent isometric plantar flexions inside the MRI bore. MRI of the calf muscles was performed on a 3.0 T scanner and diffusion-weighted (DW) images were obtained using eight different b values (0 to 500 s/mm ). Acquisitions were performed at rest, during exercise and in the subsequent recovery phase. A motion-triggered echo-planar imaging DW sequence was implemented to avoid movement artifacts. Image quality was evaluated using the average edge strength (AES) as a quantitative metric to assess the motion artifact effect. IVIM parameters (diffusion D, perfusion fraction f and pseudo-diffusion D*) were estimated using a segmented fitting approach and evaluated in gastrocnemius and soleus muscles. No differences were observed in quality of IVIM images between resting state and triggered exercise, whereas the non-triggered images acquired during exercise had a significantly lower value of AES (reduction of more than 20%). The isometric intermittent plantar-flexion exercise induced an increase of all IVIM parameters (D by 10%; f by 90%; D* by 124%; fD* by 260%), in agreement with the increased muscle perfusion occurring during exercise. Finally, IVIM parameters reverted to the resting values within 3 min during the recovery phase. In conclusion, the IVIM approach, if properly adapted using motion-triggered sequences, seems to be a promising method to investigate muscle perfusion during isometric exercise.
本文的主要目的是提出触发式体素内不相干运动（IVIM）成像序列，用于评估等长间歇运动前后小腿肌肉的灌注变化。12名健康志愿者参与了该研究。受试者被要求在MRI检查孔内进行间歇性等长跖屈运动。在3.0 T扫描仪上对小腿肌肉进行MRI检查，并使用8个不同的b值（0至500 s/mm²）获得扩散加权（DW）图像。在静息状态、运动期间和随后的恢复阶段进行采集。实施了运动触发的回波平面成像DW序列以避免运动伪影。使用平均边缘强度（AES）作为定量指标评估图像质量，以评估运动伪影效应。使用分段拟合方法估计IVIM参数（扩散系数D、灌注分数f和伪扩散系数D*），并在腓肠肌和比目鱼肌中进行评估。静息状态和触发运动时IVIM图像质量无差异，而运动期间采集的非触发图像的AES值显著较低（降低超过20%）。等长间歇性跖屈运动导致所有IVIM参数增加（D增加10%；f增加90%；D增加124%；fD增加260%），这与运动期间肌肉灌注增加一致。最后，在恢复阶段，IVIM参数在3分钟内恢复到静息值。总之，如果使用运动触发序列进行适当调整，IVIM方法似乎是研究等长运动期间肌肉灌注的一种有前途的方法。
