Evaluating radiation exposure risks from patient urine in a PET-CT center: should concerns arise?

Mpumelelo Nyathi; Autherlia Dimpho Rinkie Mosiame; Mpumelelo Nyathi; Autherlia Dimpho Rinkie Mosiame

doi:10.3934/medsci.2025016

AIMS Medical Science

2025, Volume 12, Issue 2: 238-246. doi: 10.3934/medsci.2025016

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Research article

Evaluating radiation exposure risks from patient urine in a PET-CT center: should concerns arise?

Department of Medical Physics, School of Medicine, Sefako Makgatho Health Sciences University, South Africa

Received: 12 October 2024 Revised: 28 April 2025 Accepted: 23 May 2025 Published: 18 June 2025

Introduction and Objectives
Fluorine-18 fluorodeoxyglucose (¹⁸F-FDG) is used to stage various malignancies, with approximately 30% of non-metabolized ¹⁸F-FDG being excreted through urine. Patients are advised to drink 500 mL–1 L of water to increase urine production so that they can empty their bladder whilst still at the facility to reduce the radiation dose to the bladder wall; this makes their urine radioactive. This study aims to assess the radiation dose rates from a toilet at a positron emission tomography/computed tomography (PET/CT) center.
Methods
Radiation dose measurements were conducted using a portable digital rate meter (6150AD-6 Automess) with a measuring range of 1 µSv/h to 10 mSv/h (energy range 60 keV to 1.2 MeV). The measurements were carried out over a 5-day period. The background radiation was recorded between 8:00–8:30 am. Dose rate measurements were taken daily at 9 am at several places in the toilet: on the seat, on the cistern lid, and approximately 1 m to the left and right of the chamber. Additional daily measurements carried out at 10 am, 11 am, and 12 pm. The annual cumulative dose was estimated based on a five-day working week for 42 working weeks, 8 hours per day.
Results
The measured weekly dose rate from the toilet was 14.40 ± 0.020 µSv/h. The approximate annual dose over 42 working weeks was 0.63 ± 0.001 mSv/year.
Conclusions
The estimated annual radiation dose from the toilet (0.63 mSv/year) is well below the recommended dose limits for members of the public (1 mSv/year) and radiation workers (20 mSv/year) by the International Commission on Radiological Protection (ICRP). Therefore, there is no significant concern regarding an exposure from patient urine in this setting.
- radioactive urine,
- radiation,
- cumulative dose,
- fluorine-18 fluorodeoxyglucose,
- photons
Citation: Mpumelelo Nyathi, Autherlia Dimpho Rinkie Mosiame. Evaluating radiation exposure risks from patient urine in a PET-CT center: should concerns arise?[J]. AIMS Medical Science, 2025, 12(2): 238-246. doi: 10.3934/medsci.2025016

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Abstract

Introduction and Objectives

Fluorine-18 fluorodeoxyglucose (¹⁸F-FDG) is used to stage various malignancies, with approximately 30% of non-metabolized ¹⁸F-FDG being excreted through urine. Patients are advised to drink 500 mL–1 L of water to increase urine production so that they can empty their bladder whilst still at the facility to reduce the radiation dose to the bladder wall; this makes their urine radioactive. This study aims to assess the radiation dose rates from a toilet at a positron emission tomography/computed tomography (PET/CT) center.

Methods

Radiation dose measurements were conducted using a portable digital rate meter (6150AD-6 Automess) with a measuring range of 1 µSv/h to 10 mSv/h (energy range 60 keV to 1.2 MeV). The measurements were carried out over a 5-day period. The background radiation was recorded between 8:00–8:30 am. Dose rate measurements were taken daily at 9 am at several places in the toilet: on the seat, on the cistern lid, and approximately 1 m to the left and right of the chamber. Additional daily measurements carried out at 10 am, 11 am, and 12 pm. The annual cumulative dose was estimated based on a five-day working week for 42 working weeks, 8 hours per day.

Results

The measured weekly dose rate from the toilet was 14.40 ± 0.020 µSv/h. The approximate annual dose over 42 working weeks was 0.63 ± 0.001 mSv/year.

Conclusions

The estimated annual radiation dose from the toilet (0.63 mSv/year) is well below the recommended dose limits for members of the public (1 mSv/year) and radiation workers (20 mSv/year) by the International Commission on Radiological Protection (ICRP). Therefore, there is no significant concern regarding an exposure from patient urine in this setting.

Ethical approval of the research and informed consent

The study was approved by the Research Ethics Committee of a Health Sciences University under clearance (SMUREC/M/184/2021: PG). No direct patients' data was used in this study. Only demographic information (age and gender) was used gathered from patient records kept confidential by the researchers in line with the act on protection of personal information.

Conflict of interest

The authors declare no conflict of interest.

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