基于肺部血流MRI信号在心动周期内变化的灌注成像技术研究

目的探讨血流变化对肺部MRI信号的影响，并研究1种新的MR肺血流灌注成像方法。方法对健康志愿者15例，采用相位对比电影MRI技术测量大肺动脉血流速度和流量在心动周期内的变化；并选用单次激发半傅立叶变换超快速自旋回波序列观察肺实质MR信号的相应改变，评价其相关性；根据不同心动期相肺实质MR信号的差异进行图像减影。结果肺实质．MRI信号表现为心脏收缩期降低，舒张期升高。大肺动脉的瞬时速度、瞬时流量与其呈负相关(r=-0．878、-0．770，P=0，002、0．015)。经肺部MRI信号差异最大的舒张末期和收缩中期的MRI减影可获得肺灌注像。结论肺实质MRI信号的改变与肺血流模式和速度有关。该技术是1种简便易行的非对比剂性的MR肺灌注评价新方法。

MRI pulmonary perfusion imaging study based on the variety of signal intensity in lung parenchyma during a cardiac cycle

Objective To investigate a new MR pulmonary perfusion imaging technique according to the effect of blood flow on MR signal intensity (SI) of pulmonary parenchyma.Methods The instantaneous velocity and flow volume of main,left and right pulmonary arteries during a cardiac cycle were measured by phase-contrast cine MR imaging in 15 healthy volunteers.Moreover,the corresponding changes of MR SI in pulmonary parenchyma were detected by half-Fourier single-shot turbo spin echo sequence (SSTSE),and the correlations between them were analyzed.The subtraction of MRI in different cardiac phase was implemented.Results SI of lung parenchyma decreased during systole while it increased gradually in diastole,which negatively correlated with the instantaneous velocity and flow volume (r=-0.878,-0.770,P=0.002,0.015).The pulmonary perfusion MR imaging was acquired by subtracting SSTSE image between end diastole and middle systole phase.Conclusion The changes of SI in lung during a cardiac cycle are caused by flow velocity and pattern due to dephasing of blood proton spins.The technique can provide a new simple and facile method for assessing the pulmonary perfusion.