Measurement of microvascular cerebral blood volume changes over the cardiac cycle with ferumoxytol-enhanced T2* MRI

Purpose: This feasibility study investigates the non-invasive measurement of microvascular cerebral blood volume (BV) changes over the cardiac cycle using cardiac-gated, ferumoxytol-enhanced T-2(*) MRI. Methods: Institutional review board approval was obtained and all subjects provided written informed consent. Cardiac gated MR scans were prospectively acquired on a 3.0T scanner in 22 healthy subjects using T-2(*)-weighted sequences with 2D-EPI and 3D spiral trajectories. Images were collected before and after the intravenous administration of 2 doses of ferumoxytol (1 mg FE/kg and 4 mg FE/kg). Cardiac cycle-induced R-2* (1/T-2*) changes (Delta R-2(*)) and BV changes (Delta BV) throughout the cardiac cycle in gray matter (GM) and white matter (WM) were quantified and differences assessed using ANOVA followed by post hoc analysis. Results: Delta R-2(*) was found to increase in a dose -dependent fashion. A significantly larger increase was observed in GM compared to WM in both 2D and 3D acquisitions (P < 0.050). In addition, Delta R-2(*) increased significantly (P < 0.001) post versus pre-contrast injection in GM in both T-2(*) MRI acquisitions. Mean GM Delta R-2(*) derived from 2D-EPI images was 0.14 +/- 0.06 s(-1) pre-contrast and 0.33 +/- 0.13 s(-1) after 5 mg FE/kg. In WM, Delta R-2(*) was 0.19 +/- 0.06 s(-1) pre-contrast, and 0.23 +/- 0.06 s(-1) after 5 mg FE/kg. The fractional changes in BV throughout the cardiac cycle were 0.031 +/- 0.019% in GM and 0.011 +/- 0.008 in WM (P < 0.001) after 5 mg FE/kg. Conclusion: Cardiac-gated, ferumoxytol-enhanced T-2(*) MRI enables characterization of microvascular BV changes throughout the cardiac cycle in GM and WM tissue of healthy subjects.