Extended Data Fig. 6: Some parameters in our data and the simulations in white, gray matter and CSF.
From: Assessing cerebral microvascular volumetric with high-resolution 4D cerebral blood volume MRI at 7 T
a, simulation progress. Details in Method. CBV0 was set to 3%~4% to simulate the conditions in white matter (b), and 5%~6% to simulate the conditions in gray matter and CSF (c), respectively. We found that when CBV0 was high (in gray matter or CSF), the PI value was calculated very accurately, and the RI value reached a plateau more quickly. However, when CBV0 was low (in white matter), the vPI value had to be above 0.05 to be accurately calculated. And when the PI value reached 0.1, the calculated RI value could be stable and significantly greater than 1, and it was difficult to reach a plateau. The simulation results explain why we can measure high PI and RI values in the elderly, but they are difficult to detect in young people because the true PI values are smaller. The tissue volume (d) and the average tSNR (e) were shown in each vascular territory and each laminar ROI, n = 23 (included 11 young and 12 older participants). Bars represent group means and dots represent individual participants.
