Development of practical system for high-speed magnetic resonance elastography

磁共振弹性成像（MRE）可以通过可视化从身体表面施加的应变波来提供组织弹性的定量测量。虽然磁共振成像有望成为一种强大的诊断工具，用于组织定征，其长的采集时间限制了实际应用的区域，如大脑，四肢和乳房，呼吸运动不一定被考虑。为了实现人体腹部组织弹性的在体测量，我们提出了一种基于相位速度编码的高速磁共振成像方法，并将其与各种高速磁共振成像方法结合作为准备脉冲。该技术将速度编码相移转换为纵向磁化强度，并在图像采集后从信号强度中检索速度信息。在这项研究项目中，我们还设计了一个振荡系统，产生的应变波适当计算的弹性从收购images.Introduction我们原来的技术相速度编码的高速磁共振成像方法成功地获得磁共振成像图像在一个单一的屏气期间。本研究所提出的振荡系统是一种床型振荡器，病人可以躺在上面休息。我们建立了一个振动台的原型，从振动台上的弹性体模获得的MRE图像表明，产生了平坦的应变波。由于产生的纯横波与纵波分量无关，因此可以根据获得的MRE图像计算体模的剪切模量，而不会污染杨氏模量。在腹部器官组织弹性尚未获得的情况下，本研究建立了腹部磁共振弹性成像的基本方法。

Magnetic resonance elastography (MRE) can provide quantitative measurements of tissue elasticity by visualizing the strain waves applied from the body surface. Though MRE is expected to be a powerful diagnostic tool for tissue characterization, its long acquisition time limits the practical application to the area such as brain, extremities, and breast, where respiratory motion was not necessarily considered. To realize in vivo measurement of tissue elasticity in human abdomen, we aimed to develop a high speed MRE acquisition method by introducing our original technique of phase velocity encoding that could be combined with various high speed MR imaging methods as preparation pulses. The technique translated the velocity encoded phase shift into the longitudinal magnetization and the velocity information was retrieved from the signal intensity after the image acquisition. In this research project, we also designed an oscillation system that generates strain waves appropriate to calculate the elasticity from the acquired images.Introduction of our original technique of phase velocity encoding to a high speed MR imaging method successfully acquired MRE images during a single breath-hold period. The oscillation system we proposed in this research project was a bed-type oscillator on which patients rested. We constructed a prototype of table oscillator and MRE images obtained from an elastic phantom on the table oscillator demonstrated that flat strain waves were generated. Since pure transverse waves were generated independently from longitudinal wave components, shear modulus of the phantom could be calculated from the obtained MRE images without contamination of Young' s modulus. While tissue elasticity of abdominal organ has not been obtained yet, essential methodology for abdominal MRE was established in this research project.