Post-Surgical Depositions of Blood Products Are No Major Confounder for the Diagnostic and Prognostic Performance of CEST MRI in Patients with Glioma

Amide proton transfer (APT) and semi-solid magnetization transfer (ssMT) imaging can predict clinical outcomes in patients with glioma. However, the treatment of brain tumors is accompanied by the deposition of blood products within the tumor area in most cases. For this reason, the objective was to assess whether the diagnostic interpretation of the APT and ssMT is affected by methemoglobin (mHb) and hemosiderin (Hs) depositions at the first follow-up MRI 4 to 6 weeks after the completion of radiotherapy. A total of 34 participants underwent APT and ssMT imaging by applying reconstruction methods described by Zhou et al. (APTw_asym), Goerke et al. (MTR_RexAPT and MTR_RexMT) and Mehrabian et al. (MT_const). Contrast-enhancing tumor (CE), whole tumor (WT), mHb and Hs were segmented on contrast-enhanced T₁w_CE, T₂w-FLAIR, T₁w and T₂*w images. ROC-analysis, Kaplan-Meier analysis and the log rank test were used to test for the association of mean contrast values with therapy response and overall survival (OS) before (WT and CE) and after correcting tumor volumes for mHb and Hs (CE_C and WT_C). CE_C showed higher associations of the MTR_RexMT with therapy response (CE: AUC = 0.677, p = 0.081; CE_C: AUC = 0.705, p = 0.044) and of the APTw_asym with OS (CE: HR = 2.634, p = 0.040; CE_C: HR = 2.240, p = 0.095). In contrast, WT_C showed a lower association of the APTw_asym with survival (WT: HR = 2.304, p = 0.0849; WT_C: HR = 2.990, p = 0.020). Overall, a sophisticated correction for blood products did not substantially influence the clinical performance of APT and ssMT imaging in patients with glioma early after radiotherapy.