Prospective assessment of entrance skin dose and targets for radiation reduction during abdominal plain films in pediatric urology patients

Introduction

Abdominal radiographs are frequently used for evaluation of bowel and bladder dysfunction in pediatric urology. However, the dose of radiation delivered with each study is estimated from machine settings as opposed to measurement of the true entrance skin dose. In addition, the correlation of radiographic constipation with patient symptoms has been questioned.

Objective

To evaluate the practices for obtaining abdominal radiographs and the true entrance skin dose of radiation for each examination in order to identify targets for radiation reduction.

Study design

Pediatric urology patients were prospectively enrolled from June 2022 through June 2023. Dosimeters were attached to the navel to collect entrance skin doses from single view abdominal x-ray. Estimated doses were compared to measured entrance skin dose as well as patient characteristics. Exam parameters were evaluated to identify targets for radiation reduction.

Results

A total of 75 patients were recruited for this study with a median age of 10.0 years (IQR 6–14). Most evaluations were done to assess for bowel and bladder dysfunction (68 exams, 91%). The protocol for exams was not standardized resulting in 27% of patients undergoing a medium or high dose strength and 55% undergoing 1 or more image. The median estimated dose was 0.63 mGy (IQR 0.3–1.2 mGy). The median measured dose was 0.77 mGy (IQR 0.31–2.01 mGy) which was significantly different than the estimations (p < 0.001). The estimated dose, measured dose and estimate error were all found to be positively correlated with patient characteristics including age and body mass index (See Figure). Increasing age and body mass index also showed a higher likelihood of increased dose strength and image acquisition.

Discussion

The measured entrance skin dose of radiation is significantly higher than prior estimates. The measured dose but also the estimate error increased with patient age and size which is likely related to higher settings used for image acquisition as patients age. Standardized protocols using low dose settings and limiting image acquisition to the pelvis may reduce radiation exposure in children with bowel and bladder dysfunction while providing adequate diagnostic data.

Conclusion

Radiation dose for abdominal radiographs is higher than previously estimated. Older and larger children received higher doses which may be mediated by increased dose strength and image acquisition. Standardization of protocols could lower radiation exposure.