What question did this study set out to answer?

To evaluate if refined imaging definitions improve pre-surgical differentiation between IDH-mutant astrocytomas and oligodendrogliomas.

March 29, 2026Japanese Journal of Radiology1 citationsOpen Access

Conventional MRI/CT for differentiation of IDH-mutant adult-type diffuse gliomas: revisited with a new imaging feature “scFLAIR-D”

YOYuji OhizumiThe University of Tokyo RKRyo KurokawaThe University of Tokyo YWYusuke WatanabeThe University of Tokyo

Key Points

To evaluate if refined imaging definitions improve pre-surgical differentiation between IDH-mutant astrocytomas and oligodendrogliomas.
Single-center retrospective study involving adults with IDH-mutant gliomas
Blinded readers scored MRI features like redefined T2-Mismatch and scFLAIR-D
Analysis of features included comparing sensitivity and specificity for IDH-mutant tumor types.
AST exhibited redefined T2FM in 87.5% of cases, while ODG showed it in 20% (p < 0.001)
ODG exhibited scFLAIR-D in 44% of cases, while AST showed it in 6.3% (p = 0.013)
Combining features allowed for 100% specificity in identifying ODG; redefined T2FM yielded 96% specificity for AST.

Abstract

Abstract Purpose To test whether a refined definition of the T2–FLAIR mismatch sign (redefined T2FM) and a newly defined subcortical FLAIR signal drop (scFLAIR-D) on conventional MRI improve presurgical discrimination between astrocytoma, IDH-mutant (AST) and oligodendroglioma, IDH-mutant and 1p/19q-codeleted (ODG). Materials and methods In this single-center retrospective study (January 2021–July 2025), adults with IDH-mutant adult-type diffuse glioma and preoperative T2-weighted and FLAIR MRI were included. Two blinded readers (with senior adjudication) scored five features: redefined T2FM (includes partial but excludes subcortical-only mismatch), scFLAIR-D (focal FLAIR hypointensity confined to subcortical white matter within T2-hyperintensity), multiple necrotic/cystic foci (≥ 2 cavities), cortical predominance (> 50% cortical volume), and calcification (CT). Results Forty-one patients were included (median age 42 years; 24 men; 16 AST, 25 ODG). AST significantly more often showed redefined T2FM (AST: 87.5% 14/16 vs. ODG: 20.0% 5/25; p < 0.001) than ODG. ODG significantly more often showed scFLAIR-D (AST: 6.3% 1/16 vs. ODG: 44.0% 11/25; p = 0.013), multiple necrotic/cystic foci (12.5% 2/16 vs. 56.0% 14/25; p = 0.008), and calcification (0% 0/16 vs. 50.0% 12/24 patients with preoperative CT; p < 0.001); cortical predominance trended higher (31.3% 5/16 vs. 64.0% 16/25; p = 0.058). For predicting AST, redefined T2FM achieved 87.5% sensitivity and 80.0% specificity. For predicting ODG, scFLAIR-D achieved 44.0% sensitivity and 93.8% specificity. Two or more ODG-favored features (scFLAIR-D, multiple necrotic/cystic foci, calcification) identified ODG with 100% specificity, whereas redefined T2FM without ODG-favored features identified AST with 96.0% specificity. Conclusion A refined T2FM definition improves sensitivity for AST while preserving high specificity. scFLAIR-D serves as a simple, specific marker of ODG; in combination, these routine features yield high rule-in specificity to support presurgical planning and early therapeutic counseling. Secondary abstract Refining T2FM to include partial but exclude subcortical-only mismatch increased sensitivity for astrocytoma, IDH-mutant (87.5%) while preserving specificity (80.0%). Newly defined scFLAIR-D was highly specific for oligodendroglioma, IDH-mutant and 1p/19q-codeleted (93.8%). Combining these qualitative MRI/CT features yielded high rule-in specificities for lineage discrimination.

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