Evaluating the Role of Amide Proton Transfer (APT)–Weighted Contrast, Optimized for Normalization and Region of Interest Selection, in Differentiation of Neoplastic and Infective Mass Lesions on 3T MRI

To evaluate the role of amide proton transfer–weighted (APT-w) magnetic resonance imaging (MRI) in differentiating neoplastic and infective mass lesions using different contrast normalizations, region of interest (ROI) selection, and histogram analysis.

Retrospective study included 32 treatment-naive patients having intracranial mass lesions (ICMLs): low-grade glioma (LGG) = 14, high-grade glioma (HGG) = 10, and infective mass lesions = 8. APT-w MRI images were acquired along with conventional MRI images at 3 T. APT-w contrast, corrected for B₀-field inhomogeneity, was computed and optimized with respect to different types of normalizations. Different ROIs on lesion region were selected followed by ROI analysis and histogram analysis. Statistical analysis was performed using Shapiro-Wilk’s test, t tests, ANOVA with Tukey’s post hoc test, and receiver operation characteristic (ROC) analysis.

ICMLs showed significantly (p < 0.01) higher APT-w contrast in lesion compared with contralateral side. There was a substantial overlap between mean APT-w contrast of neoplastic and infective mass lesions as well as among different groups of ICMLs irrespective of ROI selection and normalizations. APT-w contrast (using type 4 normalization: normalized with reference signal at negative offset frequency and APT-w contrast in normal-appearing white matter) reduced variability of APT-w contrast across different subjects, and overlap was less compared with other types of normalizations. There was a significant difference (p < 0.05) between neoplastic and infective mass lesions using t test for different histogram parameters of type 4 normalized APT-w contrast. ANOVA with post hoc showed significant difference (p < 0.05) for different histogram parameters of APT-w contrast (Type 4 normalization) between LGG and HGG, LGG, and infective mass lesion. Histogram parameters such as standard deviation, mean of top percentiles, and median provided improved differentiation between neoplastic and infective mass lesions compared with mean APT-w contrast. A greater number of histogram parameters of type 4 normalized APT-w contrast corresponding to active lesion region can significantly differentiate between ICMLs than other types of normalizations and ROIs.

APT-w contrast using type 4 normalization and active lesion region (ROI-2) should be used for studying APT. APT-MRI should be combined with other MRI techniques to further improve the differential diagnosis of ICMLs.