Purpose: Pediatric patients with hydronephrosis commonly undergo renal scintigraphy. During exams especially after furosemide administration, excreted urine containing radiotracer may retain in the diapers of non-toilet trained children. These diapers introduce additional dose to patient’s gonads. The purpose of this study is to calculate the gonadal absorbed dose caused by urine contaminated diaper.
Methods: New-born computational male/female phantoms with diapers were created based on the NCI (National Cancer Institute) phantoms. Absorbed dose per unit activity (mGy/MBq) to gonads from diapers containing Tc-99m MAG3 were calculated using GAMOS 6.1.0 Monte Carlo algorithm package. 10 patients (5 male and 5 female infant patients with ages 2-3 months) who underwent renal scintigraphy exams on two Siemens Gamma Camera systems were retrospectively enrolled into the study. Bases on calibration factors of gamma camera systems which were acquired experimentally in phantom with diapers, the activity-time curve of contaminated diaper for each exam was generated from the acquired renal scan images. By combining the absorbed dose per unit activity and the cumulative activity, the absorbed doses to the gonads from the contaminated diaper were finally calculated.
Results: Calibration factors of two gamma camera systems were measured to be 32.43 and 39.25 cps/MBq respectively. Cumulative activities on diapers of these 10 patient studies were in the range of [571, 27710] MBq·s. Radiation doses to testicles in male patients were in the range of [0.02, 0.74] mGy and to ovaries in female patients were [0.01, 0.08] mGy. The absorbed dose per unit activity to testicles was 2.67 *10-5 mGy/MBq, which is approximately 10 times higher than that to ovaries(2.34 *10-6 mGy/MBq).
Conclusion: Gonadal absorbed dose from urine contaminated diapers by Tc-99m MAG3 during a renal scintigraphy exam can be calculated. The absorbed dose per unit activity to testicles is approximately 10 times higher than that to ovaries.
Absolute Dosimetry, Gamma Cameras