P03.27.B FLUID-SUPPRESSED APTW IMAGING BEFORE AND AFTER SURGERY IN GLIOBLASTOMA: A PROOF-OF-CONCEPT FOR DETECTING INFILTRATIVE AND RESIDUAL TUMOR BEYOND CONTRAST ENHANCEMENT

Abstract BACKGROUND In glioblastoma (GBM), the presence of residual tumor on postoperative imaging is strongly associated with patient survival. Thus, the standard of care involves maximal safe resection of contrast-enhancing tumor tissue. However, tumor infiltration often extends beyond these margins into non-enhancing peritumoral brain regions that are not visible on conventional MRI. Amide Proton Transfer-weighted (APTw) imaging has demonstrated potential for visualizing tumor-related metabolic activity beyond the contrast-enhancing zone. However, conventional APT imaging might be limited due to fluid-related artifacts following surgery, particularly from the resection cavity. In this study, we employ fluid-suppressed APTw imaging to improve both pre- and postoperative visualization and to offer a novel approach for more specific identification of residual tumor volume. METHODS In this prospective study 10 patients with histologically confirmed glioblastoma underwent fluid-suppressed APT imaging at 3T, both before and after surgical resection. APT maps were co-registered with conventional anatomical and contrast-enhanced MRI sequences. We evaluated peritumoral and postoperative regions for APT signal abnormalities and compared the findings with those from standard imaging. RESULTS Preoperatively, fluid-suppressed APTw imaging consistently revealed elevated signals extending beyond the gadolinium-enhancing tumor margins, consistent with suspected infiltrative tumor. Postoperatively, the technique effectively reduced fluid-related signal contamination within and around the resection cavity, thereby improving image interpretability. Additionally, APTw imaging identified residual areas of high signal intensity in non-enhancing regions, suggesting the presence of metabolically active tumor tissue not detectable by conventional MRI. CONCLUSION Fluid-suppressed APTw imaging enhances the detection of infiltrative tumor beyond contrast-enhancing margins in preoperative scans and reveals residual disease not visible on conventional MRI postoperatively. These findings support further investigation of this technique’s potential role in surgical planning and treatment monitoring.