Measuring foetal dose from tomotherapy treatments
Samuel C Peet1, Tanya Kairn1, Craig M Lancaster2
1Cancer Care Services, Royal Brisbane and Women's Hospital, Butterfield Street, Herston, Queensland 4029, Australia; School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
Summary
Helical tomotherapy during pregnancy delivers low fetal radiation doses, generally below the 100 mGy high-risk threshold. Doses decrease with distance, offering comparable or lower exposure than other radiotherapy methods.
Area of Science:
- Radiation Oncology
- Medical Physics
Background:
- Radiotherapy for pregnant patients is rare but requires precise fetal dose assessment.
- Understanding fetal radiation exposure is critical for risk evaluation.
Purpose of the Study:
- To investigate fetal doses during helical tomotherapy treatments.
- To compare helical tomotherapy fetal doses with other radiotherapy techniques.
Main Methods:
- Six helical tomotherapy plans were simulated on an anthropomorphic phantom.
- Ionization chambers measured fetal doses at various longitudinal positions.
- Simulated treatments included brain, head-and-neck, chest wall, and upper lung.
Main Results:
- All measured fetal doses were below the 100 mGy high-risk threshold for the first trimester.
- The maximum fetal dose recorded was 75 mGy.
- Fetal doses were categorized by risk: <50 mGy (low risk) beyond 30 cm, 50-100 mGy (uncertain risk) within 30 cm.
Conclusions:
- Helical tomotherapy yields fetal doses comparable to or lower than 3D conformal or IMRT treatments.
- Recommendations for estimating tomotherapy fetal doses were developed.
