基于局部相关性的磁共振相位对比成像和计算流体力学的对比方法

Comparison method of phase contrast MRI and computational fluid dynamics based on regional correlation

目的磁共振相位对比成像方法(phase contrast magnetic resonance imaging,PC MRI)和计算流体力学方法(computational fluid dynamics,CFD)作为研究血管内流场的两种重要方法,它们之间的对比具有重要的意义。前人的研究多聚焦于两种方法所得的速度矢量大小的相对比较,而缺乏对二者结果中速度矢量的分布规律的比较。本文提出了一种基于局部相关性的对比方法,以实现定量比较PC MRI和CFD方法结果中速度矢量大小的分布规律。方法通过PC MRI扫描9名健康志愿者左右颈内动脉血管,并进行个性化的CFD计算,分别用这两种方法得到的速度数据重建颈内动脉虹吸弯处的血流速度矢量场。引入速度大小的局部相关性参数,计算出两种方法结果的相对误差和局部相关性来比较两种方法速度矢量大小和速度分布规律,以实现定量比较。结果相对误差在靠近血管壁和虹吸弯部较大,在靠近血管中心处较小;局部相关性和相对误差的分布大体相反,但在某些流速较小、相对误差较大的位置,相关性并不低。结论基于局部相关性的对比方法,可以定量比较PC MRI和CFD结果中的速度分布,反映速度分布的相似性或差异,可作为PC MRI和CFD对比研究中的一项重要指标。

Objective As two important methods for studying flow fields in blood vessels, comparison of phase contrast magnetic resonance imaging （ PC MRI） and computational fluid dynamics （ CFD） is of great significance, Previous studies have focused on the relative comparison of the velocity vector size in the results obtained from the two methods, being short of the distribution comparisons of the two. In this paper, a regional correlation method is proposed to quantitatively comparethe distribution of velocity vectors in PC MRI and CFD results. Methods The blood flow velocity field of left andright internal carotid arteries in 9 healthy volunteers was measured by PC MRI and compared with the velocity fieldcalculated by CFD. The relative error and regional correlation were calculated to quantitatively compare the velocity vector size and velocity distribution of the two methods respectively. Results Relative errors were larger near the vessel wall and the siphon bend, whilesmaller near the center of the blood vessel. The distribution of regional correlation and relative error was over allopposite, but in some positions where flow rate was small and relative errors were large, the correlation was not low. Conclusions The comparison method based on regional correlation can quantitatively compare the velocity distribution of PC MRI and CFD results, which reflects the similarity or difference of velocity distribution and can be used as an important indicator in comparative study of PC MRI and CFD.