Quantitative Relaxometry using Synthetic MRI Could be Better than Qualitative T2-FLAIR Mismatch Sign: A Pilot Study

Abstract

Introduction The diagnostic utility of synthetic MRI (SyMRI) in patients with isocitrate dehydrogenase (IDH)-mutant lower-grade gliomas has not been investigated. The purpose of this study was to determine whether quantitative relaxometry using SyMRI could differentiate between lower-grade gliomas with an increased sensitivity when compared to the qualitative T2-FLAIR mismatch sign.Methods Between May 2019 and May 2020, thirteen patients with IDH-mutant diffuse gliomas including seven astrocytomas and six oligodendrogliomas were evaluated. Five neuroradiologists independently evaluated the presence of the T2-FLAIR mismatch sign qualitatively. Inter-rater agreement of T2-FLAIR mismatch sign was calculated using the Fleiss kappa coefficient. SyMRI parameters (T1, T2-relaxation times, proton density [PD]) were measured in the gliomas and compared by Mann–Whitney U-test. The receiver operating characteristic analysis was used to evaluate the diagnostic performance. The simulated T2-FLAIR mismatch sign (%change) was also evaluated.Results The sensitivity, specificity, and kappa coefficient were 57.1%, 83.3%, and 0.38, respectively in T2-FLAIR mismatch sign. There were differences between the gliomas in the 10–90th percentiles and the mean in T1, T2-relaxation times, and PD (all p < .05). The T2-relaxation time of the 10th and 50th percentiles, and the mean showed the highest diagnostic performance (area under the curve = 1.00). The %change of present/absent T2-FLAIR mismatch cases were –49.3 ± 6.5%, –43.4 ± 7.9%, respectively.Conclusion Quantitative relaxometry using SyMRI could differentiate astrocytomas from oligodendrogliomas with an increased sensitivity and objectivity compared to the qualitative T2-FLAIR mismatch sign.