Voiding cystourethrography in children: value of digital fluoroscopy in reducing radiation dose.

Voiding cystourethrography is a commonly used fluoroscopic procedure in children that can directly irradiate the gonads. As a consequence, much attention has been given to reducing the dose of radiation received during the procedure. A digital fluoroscope, especially adapted for use in children, was evaluated for potential reduction of the dose of radiation during the procedure. Entrance and midplane doses were calculated on child-sized phantoms by using the digital fluoroscope, digital spot films, and 105-mm spot films. Subsequently, data were collected on 47 children, grouped by ages (neonate to 1 year, 1-5 years, and 5-7 years), in whom voiding cystourethrography was performed by using the same exposure factors as those for the phantoms. On the basis of the exposure doses for the phantoms and recorded clinical peak kilovoltages, milliamperes, milliseconds, and fluoroscopic time, average skin and ovarian doses were calculated for each group of children. These doses were compared with previously reported doses for fluoroscopic and radionuclide voiding cystourethrography. Results of line-pair resolution studies for the digital spot films and 105-mm spot films were similar. Images from the digital device and 105-mm images obtained on a conventional fluoroscope were considered equally adequate for clinical decision making. The average midplane and skin doses with digital spot films for children less than 5 years old were equal to or less than 0.66 and 2.37 mGy, respectively, as opposed to 1.37 and 5.32 mGy with the 105-mm spot films. Previously reported ovarian doses range from 2.52 to 10.0 mGy for fluoroscopic voiding cystourethrography and from 0.04 to 0.05 mGy for radionuclide voiding cystourethrography. The use of digital spot films reduced dose approximately 50% compared with 105-mm spot films; the ovarian dose was 0.62 mGy greater than that for radionuclide voiding cystourethrography.