Quantitation of ellipsoid tumor areas using a circumferential measuring device.

A controlled trial of a new circumferential area measuring device, the Tumorimeter, was performed on a set of 30 radiographs of chest nodules ranging in size from 1.5 to 5.0 cm diameter. The Tumorimeter is a hand-held device with a sliding radiolucent loop used to circumferentially measure ellipsoid tumors. It is calibrated in cm2 of surface area. In a crossover comparison with standard Vernier-type calipers, the Tumorimeter was significantly more accurate than bidimensional caliper determinations (less than or equal to 5% surface area error vs a 21-28% overestimate error for calipers). It was also more rapid (an average of 10.5 sec for the Tumorimeter vs 22.3 sec for calipers for each measurement). Both results were statistically significant, P less than 0.0001 by analysis of variance. This trial demonstrates that enhanced speed and accuracy in tumor measurement are possible by using ellipsoid assessments of radiographs. A prospective clinical trial is planned to compare rectangular areas obtained using bidimensional tumor widths, with ellipsoid areas obtained by circumferential tumor measurements using the Tumorimeter.