Amide proton transfer-weighted (APTw) imaging and derived quantitative metrics in evaluating gliomas: Improved performance compared to magnetization transfer ratio asymmetry (MTR).

Rationale And Objectives: Isocitrate dehydrogenase (IDH) status, glioma subtypes and tumor proliferation are important for glioma evaluation. We comprehensively compare the diagnostic performance of amide proton transfer-weighted (APTw) MRI and its related metrics in glioma diagnosis, in the context of the latest classification.

Materials And Methods: Totally 110 patients with adult-type diffuse gliomas underwent APTw imaging. The magnetization transfer ratio asymmetry (MTR), magnetization transfer ratio normalized by reference signal (MTR), and spillover-corrected magnetization transfer ratio yielding R (MTR), and metrics based on Lorentzian fitting (Fit-amide, Fit-MTR, and Fit-MTR) were calculated. Group differences were compared between IDH genotypes, and among three glioma subtypes. The diagnostic performances were assessed using the receiver operating characteristic (ROC) analysis and compared. The correlations with Ki-67 expression were also analyzed.

Results: All APTw-related metrics exhibited significantly higher values in IDH-wildtype gliomas than in IDH-mutant gliomas (all p < 0.001). Fit-MTR had the best area under the curve (AUC) of 0.858. All APTw-related metrics in glioblastomas were significantly higher than oligodendrogliomas (all p < 0.01) and astrocytomas (all p < 0.001). No metrics had significant difference between oligodendrogliomas and astrocytomas. The highest AUCs was 0.870 for Fit-MTR in distinguishing astrocytomas from glioblastomas, and 0.867 for Fit-MTR in distinguishing oligodendrogliomas from glioblastomas. Besides, Fit-MTR had the highest correlation coefficient with Ki-67 expression of 0.578.

Conclusion: APTw-related metrics can effectively evaluate glioma IDH status, tumor subtypes and proliferation. The combination of Lorentzian fitting and the reference signal normalization could further improve the diagnostic performance, and perform better than MTR.