使用MR DIXON成像观察模拟微重力状态下人体下肢脂肪体积的变化

发布时间：2018-01-07 20:42

本文关键词：使用MR DIXON成像观察模拟微重力状态下人体下肢脂肪体积的变化　出处：《安徽医科大学》2013年硕士论文　论文类型：学位论文

【摘要】：背景:航天员在太空飞行时，由于失重时作用在运动器官上的重力负荷消失，人在太空中维持姿势和进行运动不再需要对抗重力的作用，这对机体各生理系统会产生较大影响，包括体液丢失、体重下降、立位耐力下降、肌肉萎缩、骨质进行性流失等。以往关于模拟微重力时人体脂肪体积变化的研究较少，并且研究结果并不一致，脂肪体积增加[1,2]与不变[3]的报道皆有。脂肪作为人体重要储能组织，在维持人体生理功能中起到十分重要作用，因此要深入地研究微重力对脂肪代谢的影响，必须首先了解微重力对人体内脂肪体积及其分布的影响。以往实验中测量方法大多是用双能X线吸收法，此检查虽然能较准确的测量人体各部位的脂肪体积，但有放射性，对人体有害。磁共振成像(magnetic resonance imaging MRI)技术的不断进步为准确测量人体脂肪体积提供了新的技术手段。磁共振成像技术无创、无放射、易重复、多参数成像、具有良好的空间和时间分辨率，可定量地测量人体脂肪体积的变化。磁共振水脂分离(Dixon)技术就是其中一种特殊的成像方法，，它利用水和脂肪两种物质的质子共振频率上的差异，一次扫描能分别得到纯脂和纯水的质子图像，已在临床工作中得到广泛运用。Dixon的水与脂的分别成像技术能减少肌肉与脂肪间的相互影响从而提高图像质量，能更准确的反映失重状态下人体下肢脂肪体积的变化，减小测量结果的误差。还可以用来分别测量肌肉和脂肪的体积，为研究微重力对人体的影响提供高质量的影像数据。目的：使用无放射性的先进MR成像技术，观察微重力环境时人体下肢脂肪体积的变化，为微重力环境中脂肪代谢的研究和航天员康复计划的制定提供科学依据。方法:由航天员科研训练中心招募18名健康志愿者，进行为期30天的-6°头低位模拟微重力的卧床实验，所有志愿者于卧床实验开始前一天和实验结束当日均接受下肢磁共振扫描。使用仪器为Siemens Verio3.0T磁共振扫描仪，扫描所用线圈为体表线圈。采用GRE T1WI水脂分离成像技术进行下肢无间隔横轴位扫描，扫描范围自双侧股骨头下缘至踝关节上缘。使用北京师范大学信息科学与技术学院编写的专用体积测量软件分别测量卧床前后下肢总脂肪体积、大腿段及小腿段脂肪体积。用SPSS16.0软件中配对t检验方法进行统计学分析，检验志愿者卧床实验前后的下肢脂肪体积变化的显著性。结果：与卧床实验前相比，卧床实验后所有志愿者下肢总脂肪体积及大腿段脂肪体积明显增加，分别增加15.67±11.19%(P 0.001)和20.05±13.61%(P0.001)；小腿段脂肪体积呈增加趋势，增加7.91±10.30%，统计学检验无显著性(P0.05)。结论：本实验组数据提示： (1)30天头低位卧床可以引起人体下肢总脂肪体积和大腿段总脂肪体积的增加；小腿段脂肪体积有增加趋势，但与卧床前相比，差异无显著性。 (2) MRI水脂分离技术可以用于测量人体下肢的脂肪体积，图像对比度高，无放射，操作简单易重复，有良好的应用前景，是动态观察脂肪体积变化的理想工具。
[Abstract]:Background: the astronauts in space flight, due to gravity load loss in motion organs disappear, maintain posture and motion in space is no longer needed against gravity, this will have a greater impact on the body of the physiological systems, including the loss of body fluid, body weight loss, orthostatic intolerance, muscle atrophy. Bone loss. Previous studies on the changes of the human body fat volume of simulated microgravity when less, and the results are not consistent, fat volume increased [1,2] [3] and constant both are reported.
As an important body fat storage tissue, plays an important role in maintaining the physiological function of human body, thus thoroughly study the effects of microgravity on fat metabolism, we must first understand the effects of microgravity on the human body fat volume and distribution. The method is mostly in the previous experimental measurement by dual energy X-ray absorptiometry, although this check each part can accurately measure body fat volume, but radioactive, harmful to the human body.
Magnetic resonance imaging (magnetic resonance imaging MRI) technology advances for the accurate measurement of human body fat volume provides a new technical means. Magnetic resonance imaging is non-invasive, no radiation, easy to repeat, multi parameter imaging, with good spatial and temporal resolution, can quantitatively measure the human body fat volume magnetic resonance. Water fat separation (Dixon) technology is one kind of special imaging method, it uses different proton resonance frequency of the water and fat two substances on the scanning of a proton image of pure lipids and pure water respectively, has been widely used in water and lipid.Dixon respectively imaging technology can reduce the mutual influence of muscle and the fat so as to improve the image quality in clinical work, we can more accurately reflect the changes of the lower limb of the human body fat volume loss condition, reduce the error of the measurement result. Also can be measured respectively by The volume of muscle and fat provides high quality image data for the study of the impact of microgravity on the human body.
Objective: To observe the changes of human lower extremity fat volume in the microgravity environment by using advanced radioactivity free MR imaging technology, and provide a scientific basis for the research of fat metabolism and the rehabilitation plan of astronauts in microgravity environment.
Methods: the astronaut research and training center recruited 18 healthy volunteers, bed rest for 30 days -6 degrees head down tilt simulated microgravity, all the volunteers began in bed one day before the end of the experiment and experimental day received lower extremity MRI. The instrument was Siemens Verio3.0T magnetic resonance scanner, scanning the surface coil using GRE. T1WI water fat separation of lower extremity nonseptate axial scanning imaging, scanning from the lower margin of bilateral femoral head to ankle joint on the edge. The special volume measurement software using the College of information science and technology Beijing Normal University prepared were measured before and after the total fat volume in lower limbs, thigh and leg fat volume were statistically analyzed. Using SPSS16.0 software paired t test, significant lower limb fat volume changes before and after the test bed volunteer experiments.
Results: compared with the bed before the experiment, all the total fat and thigh fat volume of volunteers lower limb segment volume increased significantly in the experiment, increased 15.67 + 11.19% respectively (P 0.001) and 20.05 + 13.61% (P0.001); lower leg fat volume increased, increased by 7.91 + 10.30%, statistically no significant (P0.05).
Conclusion: the data of the experimental group suggest that:
(1) 30 days of head down bed can cause total body fat and thigh fat volume lower extremity total volume increased; lower leg fat volume increased, but compared with before bed, there was no significant difference.
(2) MRI water fat separation technology can be used to measure the fat volume of human lower extremities, with high image contrast, no radiation, simple operation and easy repetition. It has good application prospects and is an ideal tool for dynamically observing fat volume changes.

【学位授予单位】：安徽医科大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：R85

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