Evaluation of Vestibular Schwannoma Size across Time: How Well Do the Experts Perform and What Can Be Improved?

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Abstract
BACKGROUND AND PURPOSE: 2D linear measurements are often used in routine clinical practice during vestibular schwannoma (VS) follow-up, primarily due to wider availability and ease of use. We sought to determine radiologist performance compared to 3D-volumetry, along with the impact of number of linear measurements, slice thickness and tumor volumes on these parameters. MATERIALS AND METHODS: Single center retrospective study with 97 patients (592 MRI studies). Overall agreement, sensitivity, specificity and accuracy estimates and 95% confidence intervals were calculated for the entire cohort, and subgroups based on volumes (800 mm3), slice thickness (≤ 1.5 mm or > 1.5 mm) and number of linear dimensions measured in the radiology report (0-1 or 2-3). RESULTS: There was weak agreement between radiologist inference and VS volumetry (0.45, 95% CI [0.41, 0.53]). Agreement was lower when 0-1 tumor dimension was measured (0.29, 95% CI [0.21, 0.42]), for smaller tumors < 400 mm3 (0.37, 95% CI [0.28, 0.45]), and for thick section imaging > 1.5 mm (0.36, 95% CI [0.25, 0.46]). The reader sensitivity was modest (0.49-0.54), while the accuracy for detecting ≤ ±25% interval change was weak (0.32-0.38). Reader performance trended towards improvement with thin-section imaging, measurement of 2-3 VS dimensions and for larger tumors. CONCLUSIONS: In routine practice, radiologists show poor agreement with volumetric results and sensitivity to detect interval change and overall poor accuracy for volumetric changes ≤ ± 25% in volume. In the absence of volumetric measurements, radiologists need to be more diligent when evaluating for interval changes in VS.

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