Introducing a New Definition Towards Clinical Detection of Microvascular Changes Using Diffusion and Perfusion MRI

Based on MRI diffusion and perfusion, a new criterion for detection and the healing progress of damaged tissue is suggested. The study is based on the ratio of capillary radii in symmetrical damaged and normal tissue neighboring spaces. The Apparent Diffusion Coefficient (ADC) and Cerebral Blood Flow (CBF) were measured in the brain tissues of six male Wistar rats utilizing suggested MRI measurement techniques. The ADC values of damaged and normal regions were (392\pm34.1)\times10^{-6} mm^2s^{-1} and (659\pm40.7)\times10^{-6} mm^2s^{-1}, respectively. The CBF values of damaged and normal regions were 14.5\pm10.13 ml/min/100 g and 125\pm41.03 ml/min/100 g, respectively. The geometrical parameters of the capillary for damaged and normal regions, \overline{r}/\sqrt{\overline{l}}, where \overline{r} is the mean radius and \overline{l} is the mean capillary segment length, were calculated to be 5.45\pm2.01 mm^{0.5}g^{-0.5} (mean \pm SD) and 12.8\pm2.04 mm^{0.5}g^{-0.5}, respectively. Furthermore, based on constant \overline{l}, the damaged, versus normal region, mean radius, was shown to follow the ``criterion'': \overline{r}_{Damaged}\cong0.43\times\overline{r}_{Normal}. A further analysis was conducted through suitable theoretical modeling and assumptions for the above-mentioned criterion. The analysis showed a distinct difference between normal and damaged tissues in various healing progress conditions. Moreover, a new image, namely, Diffusion/Flow map (DF map), which is a mere division of the ADC map to the CBF map, was introduced and utilized to contrast between normal and damaged tissue.