Ferrando A A, Stuart C A, Brunder D G, Hillman G R
NASA, Johnson Space Center, Houston TX, USA.
Aviat Space Environ Med. 1995 Oct;66(10):976-81.
Prolonged bed rest results in a loss of leg lean body mass. Previous studies using bed rest as a model for microgravity have shown decreases in leg mass after 12 and 14 d, 5 and 17 wk.
As magnetic resonance imaging (MRI) can provide a precise and non-invasive means of determining muscle volume, we sought to determine if changes in leg muscle volume could be detected in bed rest periods as short as 7 d.
Five young, healthy, male volunteers were subjected to 7 d of absolute bed rest. Each subject underwent MRI quantitation of segmental muscle volumes of the calves and thighs before and after bed rest. Eleven (calf) and nine (thigh) contiguous 1-cm thick transaxial images were generated over prescribed regions using a Technicare MRI imager with a 0.6T superconducting magnet and body coil. Image processing was performed using a generalized 8-bit medical image analysis package developed at University of Texas Medical Branch. Images were analyzed for muscle and non-muscle volumes (including fat, blood vessel, and bone marrow volumes).
The MRI quantitation demonstrated bed rest-induced significant decreases in segmental thigh muscle (approximately 3.0%, p < 0.05) volume.
We conclude that computerized image analysis of MRI images provides a sensitive tool capable of detecting leg volume changes of as little as 3.0% over a 7-d period of strict bed rest.
长期卧床休息会导致腿部去脂体重减少。以往使用卧床休息作为微重力模型的研究表明，在12天和14天、5周和17周后腿部重量会下降。
由于磁共振成像（MRI）能够提供一种精确且非侵入性的确定肌肉体积的方法，我们试图确定在仅7天的卧床休息期间是否能检测到腿部肌肉体积的变化。
五名年轻、健康的男性志愿者接受了7天的绝对卧床休息。每位受试者在卧床休息前后均接受了小腿和大腿节段性肌肉体积的MRI定量分析。使用配备0.6T超导磁体和体线圈的Technicare MRI成像仪，在规定区域生成11张（小腿）和9张（大腿）连续的1厘米厚的横断面图像。使用德克萨斯大学医学分校开发的通用8位医学图像分析软件包进行图像处理。对图像进行肌肉和非肌肉体积（包括脂肪、血管和骨髓体积）分析。
MRI定量分析表明，卧床休息导致大腿节段性肌肉体积显著减少（约3.0%，p<0.05）。
我们得出结论，MRI图像的计算机化分析提供了一种灵敏的工具，能够在7天严格卧床休息期间检测到低至3.0%的腿部体积变化。
