Comparing the Precision and Reliability Between Three Radiographic Techniques for Measuring Sporadic Vestibular Schwannomas

Abstract

Several methods exist for measuring vestibular schwannoma (VS) size radiographically. Our aim was to compare the precision and reproducibility of three different radiographic measurement techniques for assessing VS tumor size. Twenty patients with unilateral, sporadic VS previously untreated were identified. All patients had thin-slice T1 weighted, postcontrasted magnetization prepared rapid acquisition gradient echo images. Three measurement techniques were performed using within-subject and between-subject comparison. Experimental comparison of interobserver agreement between techniques was calculated. Interobserver intraclass correlation coefficients, repeatability coefficients, and relative smallest detectable difference were calculated and compared. Mean tumor measurements were: 10.3 mm (maximum linear dimension, [MLD]), 495.9 mm3 (orthogonal volumetric analysis, [OVA]), and 572.1 mm3 (segmented volumetric analysis, [SVA]). Interobserver correlation coefficient was excellent for all measurement techniques, but highest for segmented volumetric analysis. Repeatability coefficient was 1.44 mm for MLD, 298.9 mm3 for OVA, and 174.8 mm3 for SVA. The smallest detectable difference was 13.9% for MLD, 60.2% for OVA, and 30.6% for SVA. A subgroup analysis was performed for small tumors (<14 mm) and large tumors (>14 mm) and demonstrated increased precision of segmented volumetric analysis for larger tumors. Semi-automated segmented volumetric analysis appears more precise than either linear measurement or orthogonal volumetric analysis for reporting VS tumor size, and becomes increasingly precise for larger tumors. Tumor volume and tumor volume change over time using SVA may be more sensitive in surveilling VS than current measurement techniques.