Differentiation between glioblastomas and solid brain metastases using amide proton transfer-weighted (APTw) MRI with and without fluid suppression

OBJECT: Accurate differentiation between glioblastomas (GBM) and solitary brain metastases (MET) is crucial for treatment planning. This study evaluated the ability of amide proton transfer-weighted (APTw) MRI with and without fluid suppression (FS) to distinguish between GBM and MET. METHOD: Thirty-two patients with histopathologically confirmed GBM (n = 24) or MET (n = 8) were included. Post-processing included creation of APTw maps without FS, with patient-specific FS based on the patient's white matter values and with a fixed-factor FS. Regions of interest (ROIs) were segmented in the contrast-enhanced tumour, peritumoural oedema, necrosis and the normal-appearing white matter (NAWM). The min, max and mean signals were extracted for each ROI and normalised to NAWM, creating normalised APTw (nAPTw) values. Group differences were determined with t test and Mann-Whitney U test. Diagnostic performance was assessed using receiver operating characteristic (ROC) analysis. RESULTS: Both FS methods significantly reduced nAPTw values in tumour regions. Patient-specific FS showed highest performance in distinguishing GBM from MET in the necrotic (AUC 0.921) and oedematous regions (AUC 0.698). Fixed FS provided minor to intermediate improvements. CONCLUSION: Patient-specific fluid suppression increased the diagnostic performance of APTw imaging in differentiating GBM from MET, particularly in oedematous and necrotic regions.