Amide Proton Transfer Imaging for Differentiating Gliomas and Meningiomas and Assessing Tumor Infiltration

Differentiating gliomas from meningiomas and assessing imaging features related to glioma infiltration remain challenging with conventional magnetic resonance imaging (MRI). Amide Proton Transfer (APT) imaging, a chemical exchange saturation transfer technique, can detect changes in tissue protein content and pH, offering potential functional insights into brain tumors. This retrospective study evaluated APT imaging combined with conventional MRI in 105 patients with pathologically confirmed brain tumors (55 meningiomas, 20 low-grade gliomas [LGGs], and 30 high-grade gliomas [HGGs]). APT-derived mean signal intensity (APTmean) and the ratios of APT abnormal area to T2 hyperintense area (RAPT/T2) and to contrast-enhancing area (RAPT/E) were measured and compared among groups. APTmean was significantly higher in HGGs (median 4.60%) than in LGGs (2.95%) and meningiomas (2.70%, P < 0.001). RAPT/T2 and RAPT/E were also markedly elevated in HGGs. For distinguishing HGGs from meningiomas, APTmean achieved excellent diagnostic performance (area under the curve [AUC] = 0.969), compared with RAPT/E (0.836) and RAPT/T2 (0.800). For differentiating LGGs from meningiomas, RAPT/E (AUC = 0.781) and RAPT/T2 (AUC = 0.734) showed good performance, whereas APTmean did not differ significantly. For glioma grading (HGG vs. LGG), APTmean yielded an AUC of 0.916, superior to contrast enhancement degree (0.823). These findings indicate that APT imaging effectively distinguishes meningiomas from gliomas of different grades and provides valuable imaging-based information for inferring the extent of tumor infiltration. The combination of APTmean and spatial extent ratios provides a practical imaging tool for improving preoperative diagnosis and supporting surgical planning, particularly in challenging atypical cases.