Diagnostic performance between contrast enhancement, proton MR spectroscopy, and amide proton transfer imaging in patients with brain tumors

Purpose: To explore the relationship among parameters of magnetic resonance spectroscopy (MRS) and amide proton transfer (APT) imaging, and to assess the diagnostic performance of MRS and APT imaging for grading brain tumors in comparison with contrast enhancement of conventional MRI for preoperative grading in patients with brain tumor. Materials and Methods: Institutional Review Board approval and written informed consent were obtained. Forty-one patients with suspected brain tumors were enrolled in the study. Single-voxel MRS and 2D APT imaging of the same slice level were conducted using a 3T MRI scanner. Positive or negative contrast enhancement on T₁-weighted images was assessed by two neuroradiologists. Correlations among metabolite concentrations, metabolite ratios, and calculated histogram parameters, including mean APT (APT_mean) and the 90th percentile of APT (APT₉₀) were assessed using Spearman's correlation coefficient. Diagnostic performance was evaluated with receiver operating characteristic (ROC) curve analysis for contrast enhancement and MRS and APT imaging. Values of P < 0.05 were considered statistically significant. Results: Positive correlations with statistical significance were found between total concentration of choline (Cho) and APT₉₀ (r = 0.49), and between Cho/creatine (Cr) and APT_mean (r = 0.65) as well as APT₉₀ (r = 0.49). A negative correlation with statistical significance was observed between NAA/Cr and APT_mean (r = −0.52). According to ROC curves, Cho/Cr, APT_mean, APT₉₀, demonstrated higher area under the curve (AUC) values than that of contrast enhancement in grading gliomas. Conclusion: Significant correlations were observed between metabolite concentrations and ratios on MRS and APT values. MRS and APT imaging showed comparable diagnostic capability for grading brain tumors, suggesting that both MRS and APT imaging offer potential for quantitatively assessing similar biological characteristics in brain tumors on noncontrast MRI. Level of Evidence: 2. Technical Efficacy: Stage 2. J. MAGN. RESON. IMAGING 2017;46:732–739.