Dosimetric intercomparison for two Australasian clinical trials using an anthropomorphic phantom

Area of Science:

• Medical Physics
• Radiation Oncology
• Quality Assurance

Background:

• Accurate radiotherapy dose delivery is crucial, especially in multicenter trials with varying equipment and techniques.
• Dosimetric intercomparisons using anthropomorphic phantoms (Level III) simulate patient treatment to assess dose delivery factors.

Purpose of the Study:

• To evaluate the feasibility and effectiveness of a Level III dosimetric intercomparison service in Australasia.
• To assess dose delivery accuracy and identify factors influencing dose distribution in radiotherapy centers.

Main Methods:

• An anthropomorphic phantom (ART) was treated at 18 centers for two clinical trial scenarios (tonsil and prostate cancer).
• Thermoluminescence dosimeters (TLDs) measured dose distribution in target volumes and critical organs.
• A Level I intercomparison (slab phantom) checked absolute dose calibration.

Main Results:

• All centers delivered the correct dose to the ICRU reference point (within +/- 5% action levels).
• Absolute dose calibration and mean target dose were within specified action levels.
• Treatment technique and energy influenced critical organ doses; other parameters showed no significant impact on target dose homogeneity.

Conclusions:

• A Level III dosimetric intercomparison service is feasible and cost-effective (~$1000 US per center).
• The study confirmed accurate dose delivery in chosen scenarios, providing reassurance for the oncology community.
• Recommendations include extending the service, incorporating complementary scenarios, and improving phantom design for future quality assurance.