Abstract
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(Rex)APT and MTR(Rex)MT) and Mehrabian et al. (MT(const)). Contrast-enhancing tumor (CE), whole tumor (WT), mHb and Hs were segmented on contrast-enhanced T(1)w(CE), T(2)w-FLAIR, T(1)w and T(2)*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(Rex)MT 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.