Computer assisted determination of the dose-area product in retrograde urethrography

Retrograde urethrography (RUG) is a dynamic radiological procedure in which the cumulative dose-area product (DAP) comprises radiation doses derived from both fluoroscopy and radiography. In the present prospective study, digital retrograde urethrographs (Prestilix 1600X/DRS, General Electric) were obtained in 40 consecutive male patients (mean age 60.6 years; range 23-88 years) presenting for evaluation of urinary pathology. The radiation dose was recorded as the dose-area product. From these data, a computer program (Diasoft 2.0, PTW, Freiburg, Germany) then determined the respective proportions of the total radiation dose deriving from fluoroscopy and radiography, as well as the number of radiographic exposures. The average total radiation dose was 316 cGy cm2. In five of the 40 patients examined (12.5%), the number of radiographic exposures registered by the program and, hence, the calculated DAPs were erroneous. In the remaining 35 patients, the average proportion of the cumulative DAP resulting from fluoroscopy was 81%, while that deriving from radiography was 19%. The computer program utilized in this study makes possible an intelligent evaluation of the DAP in dynamic procedures such as RUG. Since fluoroscopy is responsible for 81% of the cumulative DAP at RUG, a significant decrease in applied radiation dose may be achieved by reducing fluoroscopy time or by using pulsed fluoroscopy.