Effect of multiple perfusion components on pseudo-diffusion coefficient in intravoxel incoherent motion imaging

The aim of this work was to investigate the effect of multiple perfusion components on the pseudo-diffusion coefficient D* in the bi-exponential intravoxel incoherent motion (IVIM) model. Simulations were first performed to examine how the presence of multiple perfusion components influences D*. The real data of livers (n = 31), spleens (n = 31) and kidneys (n = 31) of 31 volunteers was then acquired using DWI for in vivo study and the number of perfusion components in these tissues was determined together with their perfusion fraction and D*, using an adaptive multi-exponential IVIM model. Finally, the bi-exponential model was applied to the real data and the mean, standard variance and coefficient of variation of D* as well as the fitting residual were calculated over the 31 volunteers for each of the three tissues and compared between them. The results of both the simulations and the in vivo study showed that, for the bi-exponential IVIM model, both the variance of D* and the fitting residual tended to increase when the number of perfusion components was increased or when the difference between perfusion components became large. In addition, it was found that the kidney presented the fewest perfusion components among the three tissues. The present study demonstrated that multi-component perfusion is a main factor that causes high variance of D* and the bi-exponential model should be used only when the tissues under investigation have few perfusion components, for example the kidney.

本研究旨在探究多灌注成分对双指数体素内不相干运动（IVIM）模型中伪扩散系数D*的影响。首先进行模拟，以研究多灌注成分的存在如何影响D*。随后，通过弥散加权成像（DWI）采集31名志愿者肝脏（n = 31）、脾脏（n = 31）和肾脏（n = 31）的真实数据用于体内研究，并利用自适应多指数IVIM模型确定这些组织中灌注成分的数量、灌注分数以及D*。最后，将双指数模型应用于真实数据，计算31名志愿者三种组织各自的D*的均值、标准差、变异系数以及拟合残差，并进行组间比较。模拟和体内研究结果均表明，对于双指数IVIM模型，当灌注成分数量增加或灌注成分间差异增大时，D*的方差和拟合残差均趋于增大。此外，研究发现肾脏在三种组织中灌注成分最少。本研究表明，多成分灌注是导致D*高方差的主要因素，双指数模型仅适用于所研究组织灌注成分较少的情况，如肾脏。