Contamination during a brachytherapy procedure.

Area of Science:

• Medical Physics
• Radiation Safety
• Nuclear Medicine

Background:

• Brachytherapy using Iodine-125 (125I) seeds is a common treatment for prostate cancer.
• Radiation safety protocols are crucial to prevent unintended exposure during medical procedures.
• Contamination incidents, though rare, necessitate thorough investigation and protocol review.

Purpose of the Study:

• To describe an unusual contamination incident involving 125I seeds during prostate cancer treatment.
• To analyze the response errors resulting from inappropriate radiation safety procedures.
• To evaluate the effectiveness of thyroid screening methods for staff potentially exposed to 125I.

Main Methods:

• Patient treatment with 108 125I seeds (1.61 GBq total activity).
• Radiation surveys to detect external radiation levels.
• Urine analysis to detect internal contamination.
• Thyroid screening of staff using thyroid uptake measurements and background thigh counts.
• Patient thyroid uptake measurements 10 days post-incident.

Main Results:

• Radiation levels up to 15 microR/h detected near implantation needles.
• Patient urine sample positive for 125I, indicating leaking seeds.
• Initial staff thyroid screening suggested potential contamination, but subsequent analysis indicated no staff contamination.
• Patient exhibited significant 125I uptake in the thyroid (estimated 58 kBq initial burden).
• Initial screening methods for staff thyroid contamination were found to be unreliable.

Conclusions:

• The incident highlighted the critical need for radiation safety procedures tailored to specific procedures and potential failure modes.
• Leaking 125I seeds can lead to significant internal contamination in patients.
• Existing thyroid screening methods may require re-evaluation to accurately detect low-level 125I contamination in staff.