Reducing patient dose in voiding cystourethrography

Abstract

Patient entrance exposures and gonadal doses were measured in 50 children during voiding cystourethrography. Entrance exposures ranged from 287 mR to 5.7 R. Gonad doses ranged from 70 mrad to 1.1 rad in males; 27 to 125 mrad in females. The presence of contrast agent in certain locations in the field can result in a 10-fold increase in dose compared to the dose with no contrast. The difference in dose when using 100 mm films relative to cassette spot films (with rare earth screens) depends on the view, but in no case did 100 mm films offer more than 11% dose reduction, and they frequently were associated with a higher dose than cassette spot films. The automatic brightness control circuits of our generator have been modified, and pre-void films are now routinely taken on cassettes to reduce patient dose. Other modifications under consideration to reduce patient dose include further changes in the automatic brightness control circuit and mechanical modifications to prevent excessive patient-image intensifier distances.