MRI Signs for the Preoperative Diagnosis of Intracranial Solitary Fibrous Tumors

BACKGROUND: Intracranial solitary fibrous tumors (ISFTs) are frequently misdiagnosed as meningiomas on MRI. Existing MRI signs have been evaluated individually, without a standardized and externally validated diagnostic framework. PURPOSE: To develop and validate an MRI-based diagnostic score for intracranial solitary fibrous tumors (ISFT-DS) for the preoperative identification of ISFTs. STUDY TYPE: Retrospective multicenter diagnostic accuracy study. POPULATION: Five hundred with ISFTs (mean age, 46.4 ± 11.7 years; 269 men), 250 with low-grade meningiomas (mean age, 57.0 ± 11.1 years; 51 men), and 250 with high-grade meningiomas (mean age, 49.6 ± 14.3 years; 108 men). The development and external validation cohorts included 840 (84%) and 160 (16%) patients, respectively. FIELDSTRENGTH/SEQUENCE: Spin-echo T1-weighted imaging (T1WI), fast or turbo spin-echo T2-weighted imaging, and contrast-enhanced spin-echo T1-weighted imaging. ASSESSMENT: Three potential MRI features-T1WI hyperintensity, honeycomb-like cystic change, and trans-compartmental growth pattern-were assessed by three neuroradiologists and combined into the 0-3-point ISFT-DS. Diagnostic performance and the effects of standardized training in six readers were evaluated. STATISTICAL TESTS: and Fisher exact tests, analysis of variance, McNemar test, Kruskal-Wallis tests. p < 0.05 indicated statistical significance. RESULTS: At an ISFT-DS cutoff of ≥ 1, sensitivity/specificity were 81.4%/83.3% in the development cohort and 76.3%/86.3% in the external validation cohort, respectively. Specificity reached 98.3%/98.8% at ≥ 2 and 100%/100% at 3. Interreader agreement was good to excellent for the three MRI features and the ISFT-DS (κ = 0.80-0.87). Standardized reader training on the ISFT-DS increased the overall AUC from 0.67 to 0.80 (ΔAUC = 0.13), with larger gains for Readers 1 and 2 (ΔAUC = 0.21 and 0.15, respectively). DATA CONCLUSION: The ISFT-DS provides a reproducible and teachable MRI-based scoring system for standardized preoperative identification of ISFTs. EVIDENCE LEVEL: 3. TECHNICAL EFFICACY: Stage 2.