Fig. 4
White matter (WM) fiber tractography and DTI changes ex vivo in young versus old C57BL/6J mouse brains. a WM fiber tractography in representative 3 mo (Young) and 24 mo (Old) male mice from high resolution ex vivo diffusion MRI scans with B = 2000 s/mm2, voxel size of 175 μm3, and 91 gradient directions. Whole brain DTI with tractography is shown where FA value is mapped to location. Tractography in the thalamus is displayed in the insets. b Measurements of the diffusion properties in the thalamus and parietal–temporal cortex ex vivo. DTI measurements taken from the respective ROI’s included FA, MD, and RD (in units of 10−3 mm2/s). The FA values in the thalamus/cortex decreased by 68%/67%, MD increased by 140%/134%, and RD increased by 151/139%, respectively, when comparing the 3 mo young mouse brains to old-aged mice (*p value is less than 0.05 when comparing the young mice to the old aged mice group). c Anomalous diffusion in diffusion MRI in relation to a CMB site observed with T2*W imaging. The CMB location is marked with an arrow. Radial diffusion (RD) was elevated in brain tissue surrounding the CMB. Local tractography was performed using three regions of interest (ROI) either on the same side (green), contralateral (orange), or through the site of the CMB (red). A region of elevated RD around the CMB region (indicated by the arrow) was found by mapping tractography to RD value (zero is blue and 0.5*10−3 mm2/s red, scale shown as inset). The white matter tracts passing through the CMBs site were lost. Whole brain tractography in relation to tractography through the ROI sites is shown in inset