Acoustic neuroma volume: MRI-based calculations and clinical implications.

This study developed a technique for magnetic resonance imaging (MRI)-based volume calculation and defined the specific volume-diameter relationship in acoustic neuromas (AN). Computer-assisted measurement calculated the area of tumor in each MRI slice. Volume was determined by multiplying area by slice interval. The technique was validated by imaging known volumes of gadolinium. The precision was greater than 95%. Our volume calculations revealed a specific volume-diameter relationship in ANs. The following conclusions can be drawn: 1. our technique can accurately determine AN tumor volume; 2. the AN volume-diameter relationship is a specific function and cannot be predicted by assumptions of tumor shape; 3. the volume-diameter relationship should be combined with clinical data to determine the "break point" at which small increments of diameter produce significant clinical sequelae.