Grading diffuse gliomas without intense contrast enhancement by amide proton transfer MR imaging: comparisons with diffusion- and perfusion-weighted imaging

Objectives: To investigate whether amide proton transfer (APT) MR imaging can differentiate high-grade gliomas (HGGs) from low-grade gliomas (LGGs) among gliomas without intense contrast enhancement (CE). Methods: This retrospective study evaluated 34 patients (22 males, 12 females; age 36.0 ± 11.3 years) including 20 with LGGs and 14 with HGGs, all scanned on a 3T MR scanner. Only tumours without intense CE were included. Two neuroradiologists independently performed histogram analyses to measure the 90th-percentile (APT₉₀) and mean (APT_mean) of the tumours’ APT signals. The apparent diffusion coefficient (ADC) and relative cerebral blood volume (rCBV) were also measured. The parameters were compared between the groups with Student’s t-test. Diagnostic performance was evaluated with receiver operating characteristic (ROC) analysis. Results: The APT₉₀ (2.80 ± 0.59 % in LGGs, 3.72 ± 0.89 in HGGs, P = 0.001) and APT_mean (1.87 ± 0.49 % in LGGs, 2.70 ± 0.58 in HGGs, P = 0.0001) were significantly larger in the HGGs compared to the LGGs. The ADC and rCBV values were not significantly different between the groups. Both the APT₉₀ and APT_mean showed medium diagnostic performance in this discrimination. Conclusions: APT imaging is useful in discriminating HGGs from LGGs among diffuse gliomas without intense CE. Key Points: • Amide proton transfer (APT) imaging helps in grading non-enhancing gliomas • High-grade gliomas showed higher APT signal than low-grade gliomas • APT imaging showed better diagnostic performance than diffusion- and perfusion-weighted imaging