CT Determination of Parameters for Inhomogeneity Corrections in Radiation Therapy of the Esophagus

Accurate dose prediction for megavoltage photon therapy of carcinoma of the esophagus requires information on tumor depth, lung thickness, and lung density. The authors found that CT localization of internal and external contours is accurate within +/- 1 mm. Lung density can be measured with an error of less than 0.02 g/cm3 in the range 0.25-1.00 g/cm3. Variance between predicted and measured dosage was less than 3% in all patients and in most RANDO phantom measurements. Accurate radiation therapy planning is possible with CT information from a commercial scanner.