Diffuse glioma perfusion quantification with ASL and DSC: a head-to-head comparison with ¹⁵O-H₂O PET

Arterial spin labeling (ASL) is a non-invasive alternative to dynamic susceptibility contrast (DSC) for measuring cerebral blood flow (CBF), even though both methods measure slightly different contrast. This study compares ASL and DSC MRI with the gold-standard measurement ¹⁵O-H₂O PET in gliomas.

Eight patients (age 40.5 ± 17.0 years, 3 women) with grade 2-4 gliomas were scanned at 3T MRI with ASL and DSC, and at PET using a ¹⁵O-H₂O PET tracer. Quantitative comparison was performed in contralateral normal-appearing tissue, and in tumors with and without normalization to contralateral tissue. The mean voxel-wise relative error (MRE) was calculated for PET-ASL and PET-DSC. The MRE difference between ASL and DSC was evaluated using a t-test (p < 0.05 after Bonferroni correction).

ASL showed superior (p<0.001) voxel-wise agreement with PET (MRE 26.8%) in the normal-appearing tissue compared with DSC (MRE 33.8%). While the tumor maximum CBF normalized to contralateral gray matter comparison with PET did not differ between (p=0.5) ASL (MRE 23.2%) and DSC (MRE 22.0%), voxel-wise agreement was better (p<0.001) for ASL (MRE 27.2%) than for DSC (MRE 35.0%). Visually, ASL overestimated CBF near larger arteries, and DSC underestimated CBF in non-enhancing tumors with tiny capillaries.

While neither ASL nor DSC is fully comparable to ¹⁵O-H₂O PET in all tumors, ASL presents a viable non-invasive alternative to DSC for glioma imaging. These findings encourage future studies to investigate the extent to which the combination of ASL and DSC can measure complementary tumor hemodynamics.