Estimation of Mean Radius, Length and Density of Microvasculature Using Diffusion and Perfusion MRI

In theory, diffusion and perfusion information in MRI maps can be combined to yield morphological information, such as capillary density, volume and possibly capillary plasma velocity. This paper suggests a new method for determination of mean radius, length and capillary density in normal regions using diffusion and perfusion MRI. Mean Transit Time (MTT), Cerebral Blood Volume (CBV), Apparent Diffusion Coefficient (ADC), pseudo-diffusion coefficient (D*) and Ai?2 and Ai?| values were utilized to calculate mean radius, length and capillary density. To verify the proposed theory, a special protocol was designed and tested on normal regions of a male Wistar rat using obtained functions. Mean radius, length and capillary density in the normal regions were calculated to be 2.48 ± 0.35 (mean ± SD), 234 ± 12 microns and 11897 db 219/mm3, respectively. With respect to the values 0.01 through 0.1 for the CBV/Vol(voxei) parameter and 1 through 1000 sec for AR£2/AR%, the mean radius of the capillary, using the proposed method, varied from 0.076 to 7.58 microns.