Qualitative and Quantitative Analysis of MR Imaging Findings in Patients with Middle Cerebral Artery Stroke Implanted with Mesenchymal Stem Cells

Calculation of percentage brain volume change and growth-to-loss ratio. A, Brain and skull images are initially each extracted from whole-head input data from the 2 separate time points for each individual subject. The 2 images (1 at each time point) are aligned to each other by using the skull images to constrain registration scaling at each time point. Red demonstrates the common FOV. Green shows the intersection of the 2 standard space brain masks. B, Tissue-type segmentation is used to define the brain/nonbrain boundary. The perpendicular edge displacement at the brain/nonbrain boundary between the 2 time points is estimated, and the mean edge displacement is converted in the estimate of the percentage brain volume change between the 2 points. C and D, The growth-to-loss ratio is calculated in 2 different patients with mesenchymal stem cell implants from the color-rendered image of edge motion superimposed on a half-way image, created by aligning the 2 brain images from the 2 time points to each other by using the skull images to constrain the registration scaling. Red-yellow indicates brain volume increase (white arrowhead), while blue–light blue indicates brain volume decrease (“atrophy”) (white arrow). Regions of growth (red-yellow) are seen to be predominantly at the medial margin of the infarct, where the stem cells are implanted. E and F, Comparable periventricular and cortical regions are shown in healthy controls, demonstrating more red-yellow voxels in similar areas in healthy controls compared with the infarcted regions in patients with MSC implants. The GLR is calculated by tabulating the ratio of the total number of red-yellow voxels (growth areas) to the total number of blue–light blue voxels (areas of volume loss) in the region of the infarct.