Validation of a technique of computer-aided tumor volume determination.

Tumor volume at diagnosis is an important prognostic factor and volume change may predict therapeutic response. However, the accuracy of in vivo tumor volume measurement has not been established. The purpose of this study was validation of a personal computer-based technique of in vivo volume determination. CT scans of 8 radiological phantoms and 25 neuroblastoma patients were digitized using three-dimensional reconstruction and volume determination software. Phantom volumes were calculated from known dimensions or direct measurement while tumor volumes were determined by water displacement at the time of complete gross resection. Comparison to tumor volume determination was performed using an ellipsoid geometric model. The standard deviation for computer-generated triplicate volume determinations varied from 0.1 to 5.6 cc (median = 0.6 cc). Linear regression analysis demonstrated a close correlation between computer-derived volumes and the volume measured at surgery (r = 0.99) with small variability. In contrast, the correlation coefficient between ellipsoid formula-derived and water displacement volumes was 0.93. Computer-generated tumor volume determination is reproducible, accurate, and easily obtained from hard copy scans. This technique provides a quantitative in vivo measurement for use as a prognostic or therapeutic response variable.