Impact of Inversion Time for FLAIR Acquisition on the T2-FLAIR Mismatch Detectability for IDH-Mutant, Non-CODEL Astrocytomas

Abstract

The current research tested the hypothesis that inversion time (TI) shorter than 2,400 ms under 3T for FLAIR can improve the diagnostic accuracy of the T2-FLAIR mismatch sign for identifying IDHmt, non-CODEL astrocytomas. We prepared three different cohorts; 94 MRI from 76 IDHmt, non-CODEL Lower-grade gliomas (LrGGs), 33 MRI from 31 LrGG under the restriction of FLAIR being acquired with TI < 2,400 ms for 3T or 2,016 ms for 1.5T, and 112 MRI from 112 patients from the TCIA/TCGA dataset for LrGG. The presence or absence of the “T2-FLAIR mismatch sign” was evaluated, and we compared diagnostic accuracies according to TI used for FLAIR acquisition. The T2-FLAIR mismatch sign was more frequently positive when TI was shorter than 2,400 ms under 3T for FLAIR acquisition (p = 0.0009, Fisher’s exact test). The T2-FLAIR mismatch sign was positive only for IDHmt, non-CODEL astrocytomas even if we confined the cohort with FLAIR acquired with shorter TI (p = 0.0001, Fisher’s exact test). TCIA/TCGA dataset validated that the sensitivity, specificity, PPV, and NPV of the T2-FLAIR mismatch sign to identify IDHmt, non-CODEL astrocytomas improved from 31, 90, 79, and 51% to 67, 94, 92, and 74%, respectively and the area under the curve of ROC improved from 0.63 to 0.87 when FLAIR was acquired with shorter TI. We revealed that TI for FLAIR impacts the T2-FLAIR mismatch sign’s diagnostic accuracy and that FLAIR scanned with TI < 2,400 ms in 3T is necessary for LrGG imaging.

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

“…There have been great efforts within the research community to develop noninvasive imaging techniques that can predict IDH mutation status in gliomas, including magnetic resonance spectroscopy (MRS) 6 – 8 , perfusion- and diffusion-weighted magnetic resonance imaging (MRI) 9 , 10 , and machine learning with conventional MRI 5 , 11 , 12 . Whereas these techniques rely mainly on quantitative or semi-quantitative MRI measurement, qualitative imaging features such as the “T2 fluid-attenuated inversion recovery (FLAIR) mismatch sign” have proven to be powerful imaging surrogate markers for predicting IDH mutation status in tumors that appear to be histologically LrGGs 13 – 15 . These qualitative imaging features are derived from radiologically quantitative measurements such as the T1- and T2-relaxation time 15 , 16 .…”

“…Whereas these techniques rely mainly on quantitative or semi-quantitative MRI measurement, qualitative imaging features such as the “T2 fluid-attenuated inversion recovery (FLAIR) mismatch sign” have proven to be powerful imaging surrogate markers for predicting IDH mutation status in tumors that appear to be histologically LrGGs 13 – 15 . These qualitative imaging features are derived from radiologically quantitative measurements such as the T1- and T2-relaxation time 15 , 16 . Ideally, tissue relaxation time should be directly measured by MR relaxometry; however, this has not yet been incorporated into routine imaging protocols as it requires additional scan time.…”

The T2-FLAIR mismatch sign in glioblastoma, isocitrate dehydrogenase wild-type A case report

“… 8 Kinoshita et al suggested that IDH -mutant, non-codeleted astrocytomas often contain tumors that exhibit long T1 and T2 effects, which phenomenon could be the leading cause of the T2-FLAIR mismatch sign. 9 In our case, histological features include the diffuse proliferation of glioma cells with no microcystic changes but edematous changes in the background. Taken together, the T2-FLAIR mismatch sign would represent histological features themselves than genetic profiles.…”

Reverse Engineering Glioma Radiomics to Conventional Neuroimaging

“…We tested this hypothesis by investigating the image acquisition parameters of the TCIA dataset and found that differences in inversion time played a critical role in the presence or absence of the T2-FLAIR mismatch sign for astrocytoma with IDH mutation. 91) AUROC increased from 0.63 to 0.87 if the inversion time was correctly adjusted for FLAIR acquisition aiming at glioma imaging ( Fig. 5 ).…”

“…Both cases highlight the importance of TI for FLAIR acquisition in terms of visualization of the T2-FLAIR mismatch sign. The figure was cited from Kinoshita et al 91) with minor modification under the terms of the Creative Commons Attribution License (CC BY).…”