The value of ultrasonic imaging and CT scanning in planning the radiotherapy for prostatic carcinoma.

Forty-four consecutive patients with potentially curable carcinoma of the prostate were localized with an Old Delft Simulator with the methods described by Bagshaw. The isocenter and the treatment portal were marked on the skin of the patient. Subsequently, the adequacy of the portal was checked by ultrasonography and/or CT scanning. Of 30 patients who underwent ultrasonography, five patients (17%) were found to have tumor extending beyond the initially simulated treatment portals. Using CT scanning, three of 22 patients were found to have tumor extending beyond the initially simulated portals. As a result, 1-2 cm were added to the initially simulated treatment portals for adequate coverage of the tumor volumes. Eight of our 44 patients underwent both studies and results were similar with ultrasonography and CT scanning. Only patients in the group presenting with clinical stage C disease had modifications of the initially simulated treatment portal. It is recommended that conventional simulation should be done first in order to establish the isocenter and treatment volume, which then should be confirmed by ultrasonography or CT scanning.