Tumor Volume Measurements of Acoustic Neuromas with MR Imaging

Abstract

Although clinical decisions are based on the measurement of diameter, tumor volume is a more clinically relevant parameter in the management of patients with acoustic neuromas. On the basis of the voxel-count method and three-dimensional (3D) constructive interference in steady state (CISS) MR imaging, we evaluated ellipsoid formulas in conventional spinecho (SE) magnetic resonance (MR) imaging in tumor volume measurements of acoustic neuromas. Twenty-two patients with acoustic neuromas were examined using high-resolution 3D-CISS and SE imaging with a 1.5-T system. Tumor volume determined by SE imaging with ellipsoid formulas was overestimated when compared with volumes obtained by 3D-CISS with the voxelcount method (the standard reference method). However, tumor volume obtained using SE imaging with ellipsoid formulas showed a high correlation with volumes determined by the reference standard (P < 0.0001). The use of regression equations allowed a more accurate evaluation of the tumor volume determined on the basis of tumor diameters observed in SE images. Thus, we recommend the use of regression equations for more accurate evaluation of the tumor volume of acoustic neuromas when determined on the basis of tumor diameters.