Evaluation of tumor measurements in oncology: Use of film-based and electronic techniques

Purpose: To evaluate the variability in bidimensional computed tomography ( CT) measurements obtained of actual tumors and of tumor phantoms by use of three measurement techniques: hand-held calipers on film, electronic calipe rs on a workstation, and an autocontour technique on a workstation. Materials and Methods: Three radiologists measured 45 actual tumors (in the lung, liver, and lymph nodes) on CT images, using each of the three techni ques. Bidimensional measurements were recorded, and their cross-products ca lculated. The coefficient of variation was calculated to assess interobserv er variability. CT images of 48 phantoms were measured by three radiologist s with each of the techniques, In addition to the coefficient of variation, the differences between the cross-product measurements of tumor phantoms t hemselves and the measurements obtained with each of the techniques were ca lculated. Results: The differences between the coefficients of variation were statist ically significantly different for the autocontour technique, compared with the other techniques, both for actual tumors and for tumor phantoms, There was no statistically significant difference in the coefficient of variatio n between measurements obtained with hand-held calipers and electronic cali pers. The cross-products for tumor phantoms were 12% less than the actual c ross-product when calipers on film were used, 11% less using electronic cal ipers, and 1% greater using the autocontour technique. Conclusion: Tumor size is obtained more accurately and consistently between readers using an automated autocontour technique than between those using handheld or electronic calipers. This finding has substantial implications for monitoring tumor therapy in an individual patient, as well as for evalu ating the effectiveness of new therapies under development. J Clin Oncol 18 :2179-2184. (C) 2000 by American Society of Clinical Oncology.