Objectives
Assess the feasibility of using an optimised ultra-high-field high-spatial-resolution low-distortion ASL MRI acquisition to measure focal haemodynamic pathology in cortical lesions (CLs) in Multiple Sclerosis (MS).
Methods
Twelve MS patients (8 female, mean age=50; range=35-64 years) gave informed consent and were scanned on a 7 Tesla Philips Achieva scanner. Perfusion data were collected at multiple post-labeling delay times using a single-slice flow-sensitive alternating inversion recovery ASL protocol with a balanced steady-state free precession readout scheme. CLs were identified using a high-resolution Phase-Sensitive Inversion Recovery (PSIR) scan. Significant differences in perfusion within CLs compared to immediately surrounding normal appearing grey matter (NAGMlocal) and total cortical normal appearing grey matter (NAGMcortical) were assessed using paired t-tests.
Results
40 CLs were identified in PSIR scans that overlapped with the ASL acquisition coverage. After excluding lesions due to size or intravascular contamination, 27 lesions were eligible for analysis. Mean perfusion was 40 ± 25 ml/100g/min in CLs, 53 ± 12 ml/100g/min in NAGMlocal, and 53±8 ml/100g/min in NAGMcortical. CL perfusion was significantly reduced by 23 ± 9% (mean±SE, p=0.013) and 26 ± 9% (mean±SE, p=0.006) relative to NAGMlocal and NAGMcortical perfusion, respectively.
Conclusion
This is the first ASL MRI study quantifying CL perfusion in MS at 7T, demonstrating that an optimised ASL acquisition is sensitive to focal haemodynamic pathology previously observed using Dynamic Susceptibility Contrast MRI. ASL requires no exogenous contrast agent, making it a more appropriate tool to monitor longitudinal perfusion changes in MS, providing a new window to study lesion development
