Introduction

A voiding cystourethrogram (VCUG) is a source of ionizing radiation exposure to pediatric patients. The actual radiation dose absorbed by the patient has not been accurately reported, and concerns for radiation exposure using this conventional imaging modality has spurred the development of less accurate means to diagnose and characterize vesicoureteral reflux (VUR). We prospectively measure radiation dose during VCUG using a single point dosimeter in pediatric patients.

Methods

Pediatric patients undergoing conventional VCUG were prospectively enrolled in the study. Dosimeters (nanoDot®OSL) were affixed to the skin overlying the sacrum. Siemens® Axiom Luminos TF fluoroscopic machine was used, and skin-to-source distance was fixed at 60 cm, beam collimated to the smallest area possible, low dose setting applied, and fluoroscopy pulsed at 3 frames/sec. Dose area product (mGy*m2) and fluoroscopic time (sec) was determined by the xray source. Air kerma (mGy), which is the radiation dose delivered by the source to a single point in air, was calculated. The absorbed dose received by dosimeter (mGy) was measured.

Results

Thirty-eight patients were prospectively enrolled in our study with a median age of 12.5 months (IQR 4-39), median body mass index (BMI) of 17 (IQR 16.4-18.6), and predominantly female (68%). Median fluoroscopic time was 54 seconds (IQR 36-72). The median dose area product (mGy*m2) was 4.4 (IQR 2.6-7.5) and median radiation dose absorbed at the skin entrance per dosimeter (mGy) was 0.33 (IQR 0.13-0.5, range .01-2.9) (p=0.01). There was a positive correlation between the air kerma, 0.2 mGy (IQR 0.17-0.39) and absorbed dose measured by dosimeter, 0.33 mGy (IQR 0.13-0.5) (r = 0.67, p < 0.001). There was no correlation between absorbed dose and BMI (r = 0.14, p = 0.4), and fluoroscopy time and BMI (r = 0.24, p = 0.15). There was a positive correlation between fluoroscopy time and absorbed dose (r = 0.64, p < 0.001).

Conclusions

The radiation dose absorbed at skin entrance is low for a single VCUG when employing tight collimation, low dose settings and pulsed fluoroscopy without compromising the quality of the image. As newer non-ionizing technologies to diagnoses VUR continue to emerge, this study provides reassurance that a single VCUG is still safe with low radiation doses.

Funding

None