Characterizing pre- and post-operative cerebral blood flow and transit time in pediatric moyamoya patients using multi-delay ASL and DSC MRI

Abstract

Cerebral blood flow (CBF) and transit time are essential biomarkers for assessing brain health. While dynamic susceptibility contrast (DSC) MRI has been widely applied to measure these metrics, it is limited in the pediatric population due to the need for contrast agents. Arterial spin labeling is a non-invasive and quantitative MR modality, and multi-delay ASL can measure CBF and transit time simultaneously. Although multi-delay ASL has been used in adult neuroimaging studies, its application in children requires investigation. Moyamoya disease, a progressive steno-occlusive cerebrovascular disorder, often manifests in childhood. In this work, we present a cohort study that examines multi-delay ASL and DSC MRI to characterize vascular hemodynamics in 22 pediatric patients. We evaluate CBF and transit time in different brain regions before and after revascularization surgeries. Results show that revascularization significantly increased CBF by 24% and 7.6%, respectively, as measured by ASL and DSC; it also significantly decreased transit time by 12% and 15%, indicating improved hemodynamics and metabolism. ASL and DSC results also showed significantly positive correlations in all brain regions. Thus, revascularization improved hemodynamics in pediatric moyamoya patients and shows that multi-delay ASL can effectively characterize CBF and transit time in the pediatric population.

Keywords: Cerebral blood flow; arterial spin labeling; arterial transit time; dynamic susceptibility contrast; moyamoya disease.

Figure 1.

Pre- and post-surgery hemodynamic maps of a pediatric moyamoya patient with left MCA occlusion. (a) The pre-surgery MRA shows occlusion at the left MCA with lenticulostriate collateral vessels, and the post-surgery MRA displays the STA-MCA graft. (b) The pre-surgery ASL shows decreased CBF in the left MCA territory; CBF improved post-surgery. A similar trend can be seen in the CBF maps obtained by DSC MRI and (c) in the transit time maps, the pre-surgery ASL map shows delayed ATT in the left MCA region; ATT decreased (improved) post-surgery. Similar observations can be found in Tmax maps obtained by DSC MRI.

Figure 2.

Box plots showing CBF changes before and after surgery. (a) CBF results measured by ASL MRI and (b) CBF results measured by DSC MRI. For both ASL and DSC results, mean CBF increased significantly after revascularization in both affected and healthy regions. Each box plot indicates, from top to bottom, the maximum, 75th, 50th, 25th percentiles, and minimum.

Figure 3.

Correlation between CBF measured by ASL and DSC before and after surgery. (a) Results in regions affected by vasculopathy and (b) results in healthy or unaffected regions. Overall, significantly positive correlations can be found between ASL and DSC in both conditions. The correlation was higher in affected regions than healthy regions. The shaded area represents the 95% confidence interval.

Figure 4.

Box plots showing transit time changes before and after bypass surgery. (a) Mean ATT in regions affected by vasculopathy reduced significantly after bypass and (b) mean Tmax reduced significantly after bypass in regions affected by moyamoya vasculopathy. No significant transit time changes are found in healthy brain regions. Each box plot indicates, from top to bottom, the maximum, 75^th, 50^th, 25^th percentiles, and minimum.

Figure 5.

Correlation between mean ATT and Tmax measured by ASL and DSC MRI. Overall, significantly positive correlations between ATT and Tmax can be found in all conditions before and after surgery. (a) The correlation slightly increased after surgery in regions affected by vasculopathy and (b) the correlation decreased marginally after surgery in healthy regions. The shaded area represents the 95% confidence interval.