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

In theory, diusion 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 diusion and perfusion MRI. Mean Transit Time (MTT), Cerebral
Blood Volume (CBV), Apparent Diusion Coecient (ADC), pseudo-diusion coecient (D)
and
R2 and
R
2 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  219=mm3, respectively. With respect to the values 0.01 through 0.1 for the
CBV/Vol(voxel) parameter and 1 through 1000 sec for
R2
2 =
R3
2, the mean radius of the
capillary, using the proposed method, varied from 0.076 to 7.58 microns.