NIMG-53. RATIO OF T1-WEIGHTED TO T2-WEIGHTED SIGNAL INTENSITY AND IDH MUTATION IN GLIOMA

Abstract

Abstract INTRODUCTION Identifying IDH mutation status before treatment is essential for Lower-grade glioma (LrGG) treatment. We have previously revealed that IDH mutated LrGG consists of tumor tissues with significantly longer T1 and T2 relaxation time and is a useful radiological feature to identify IDH mutation status. The ratio of T1-weighted to T2-weighted signal intensity (rT1/T2) is a way to retrieve semi-quantitative relaxation time information of the tissue bypassing the need to perform relaxometry. This investigation aimed to elucidate the correlation between rT1/T2 and T1-, T2-relaxation time (-relax) in glioma tissue and to explore the possibility of rT1/T2 as a radiological surrogate marker to identify IDH mutation status in LrGG. MATERIALS AND METHODS We analyzed 8 LrGGs (IDHwt:4, IDHmt:2, IDHmt&1p19q-CODEL:2) in which relaxometry was performed. rT1/T2 maps were reconstructed as described in previous literature. Regions-of-interest were designed based on T2WI and FLAIR. The correlations between rT1/T2 and T1- and T2-relax were analyzed. Furthermore, We also investigated the correlation of IDH mutation status and rT1/T2. RESULTS 106,488 voxels were analyzed. The correlation between rT1/T2 and T1- and T2-relax were rT1/T2=1.6e-0.0003T1-relax and rT1/T2=1.2e-0.002T2-relax (R=0.77 and 0.70). rT1/T2 of IDH-wildtype tumor was significantly higher than that of IDH-mutant tumor (1.0 vs. 0.75, p< 0.0001). Voxel-wise analysis of rT1/T2 map was able to discriminate IDH-wildtype tumor from the mutant tumor with an AUC of 0.82. CONCLUSIONS rT1/T2, which can be calculated from MRI acquired during routine clinical practice, is a promising radiological surrogate marker to identify IDH mutation status in LrGG.