This study developed a technique for magnetic resonance imaging (MRI)-
based volume calculation and defined the specific volume-diameter rela
tionship in acoustic neuromas (AN). Computer-assisted measurement calc
ulated the area of tumor in each MRI slice. Volume was determined by m
ultiplying area by slice interval. The technique was validated by imag
ing known volumes of gadolinium. The precision was greater than 95%. O
ur volume calculations revealed a specific volume-diameter relationshi
p in ANs. The following conclusions can be drawn: 1. our technique can
accurately determine AN tumor volume; 2. the AN volume-diameter relat
ionship 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 in
crements of diameter produce significant clinical sequelae.