Comparing Linear and Volumetric Vestibular Schwannoma Measurements Between T1 and T2 Magnetic Resonance Imaging Sequences

Objective: To compare linear and volumetric vestibular schwannoma (VS) measurements between different magnetic resonance imaging (MRI) sequences. Study Design: Retrospective case series. Setting: Tertiary care university hospital. Patients: Those with VS that had at least two separate MRI studies containing both T1-weighted contrast (T1C) and high-resolution T2-weighted (HRT2) images. Intervention: Two neurotologists measured the greatest linear axial dimension and segmentation volumes of VS. Main Outcome Measure: 1) Correlation between T1C and HRT2 VS linear and volumetric measurements. 2) Comparing the interpretation of VS growth between T1C and HRT2 sequences and reviewers, defined as an increase in tumor diameter of more than or equal to 2mm or a volume increase of more than or equal to 20%. Results: Twenty-three patients met inclusion criteria. Imaging studies encompassed a median of 25.2 months. At the initial imaging study, inter-observer measurements between reviewers, analyzed with intraclass correlation coefficients, for T1C diameters, T1C volumes, HRT2 diameters, and HRT2 volumes were 0.983 (95% confidence interval [CI] 0.972-0.989), 0.989 (95% CI 0.982-0.993), 0.992 (95% CI 0.988-0.995), and 0.998 (95% CI 0.995-0.999), respectively. The Cohen's kappa for growth rates between T1C diameters, T1C volumes, HRT2 diameters, and HRT2 volumes was 0.564 (95% CI 0.284-0.844), 0.704 (95% CI 0.514-0.894), 0.605 (95% CI 0.319-0.891), and 0.475 (95% CI 0.242-0.708), respectively. Conclusions: There are significant differences in VS volume measurements when utilizing T1C versus HRT2 images. However, there is "excellent"interobserver agreement between T1C and HRT2 diameters and volumes. T1C VS volumes may be more reliable than HRT2 volumes to determine growth.