Correlation of T1- to T2-weighted signal intensity ratio with T1- and T2-relaxation time and IDH mutation status in glioma

<jats:title>Abstract</jats:title><jats:p>The current study aimed to test whether the ratio of T1-weighted to T2-weighted signal intensity (T1W/T2W ratio: rT1/T2) derived from conventional MRI could act as a surrogate relaxation time predictive of <jats:italic>IDH</jats:italic> mutation status in histologically lower-grade gliomas. Strong exponential correlations were found between rT1/T2 and each of T1- and T2-relaxation times in eight subjects (rT1/T2 = 1.63exp<jats:sup>−0.0005T1-relax</jats:sup> + 0.30 and rT1/T2 = 1.27exp<jats:sup>−0.0081T2-relax</jats:sup> + 0.48; R<jats:sup>2</jats:sup> = 0.64 and 0.59, respectively). In a test cohort of 25 patients, mean rT1/T2 (mrT1/T2) was significantly higher in IDHwt tumors than in IDHmt tumors (<jats:italic>p</jats:italic> < 0.05) and the optimal cut-off of mrT1/T2 for discriminating IDHmt was 0.666–0.677, (AUC = 0.75, <jats:italic>p</jats:italic> < 0.05), which was validated in an external domestic cohort of 29 patients (AUC = 0.75, <jats:italic>p</jats:italic> = 0.02). However, this result was not validated in an external international cohort derived from TCIA/TCGA (AUC = 0.63, <jats:italic>p</jats:italic> = 0.08). The t-Distributed Stochastic Neighbor Embedding analysis revealed a greater diversity in image characteristics within the TCIA/TCGA cohort than in the two domestic cohorts. The failure of external validation in the TCIA/TCGA cohort could be attributed to its wider variety of original imaging characteristics.</jats:p>