Prospective evaluation of radiation dose with conventional fluoroscopic voiding cystourethrogram in pediatric patients.

Introduction: Skin entrance doses for voiding cystourethrogram (VCUG) have not been well characterized in the literature. Radiation exposure is measured as either dose area product (DAP) or air kerma, which estimates the effective dose, but does not accurately reflect absorbed dose at skin level.

Objective: The objective of this study was to measure the skin entrance dose during fluoroscopic VCUG study in pediatric patients using single point dosimeters.

Study Design: Pediatric patients undergoing fluoroscopic VCUG were prospectively enrolled in our study. Landauer NanoDot™OSLD dosimeters were affixed to the skin overlying the sacrum to measure skin entrance dose. The fluoroscopic unit was set to the following parameters: low dose setting, skin-to-source distance of 54 cm, pulsed fluoroscopy at 3 frames/sec.

Results: Forty-four patients with a median age of 13.6 months (IQR 3.7-42.3) were enrolled. Median fluoroscopic time was 54 s (IQR 36-72). The median values absorbed dose by dosimeter and air kerma were 0.32 mGy (IQR 0.13-0.56, range 0.01-2.9) and 0.24 mGy (IQR 0.14-0.37), respectively. There was a positive correlation between the air kerma and absorbed dose (r = 0.69, p < 0.001) and fluoroscopy time and absorbed dose mGy (r = 0.60, p < 0.001). Absorbed dose was independent of age, body mass index and body surface area (p = 0.19, p = 0.57 and p = 0.16, respectively). Median whole body effective dose was 0.04 mSv (IQR 0.02-0.7).

Discussion: Overall, the absorbed dose received by the dosimeter remained low at a median of 0.32 mGy (range 0.01-2.91). These values are remarkably low and well within the accepted radiation exposure norms. Our radiologists follow a strict protocol to reduce the overall radiation emitted during a VCUG. These measures include setting the x-ray source at a low dose mode, collimating to the smallest area possible, and using pulsed fluoroscopy at 3 frames/sec. Limitations to this study include a slight variability in technique of VCUG between different technicians and providers, for which we cannot control.

Conclusion: The radiation dose absorbed at the skin entrance and uniform whole body effective dose is low for a single VCUG when utilizing strict parameters. While newer non-ionizing technologies continue to emerge, our data is encouraging and will serve as a valuable tool when educating parents regarding radiation doses associated with a VCUG.