Dynamic lung phantom commissioning for 4D dose assessment in proton therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Anthropomorphic phantoms simulating patient motion are vital for testing ion beam therapy motion mitigation.
• The Advanced Radiation DOSimetry system (ARDOS) phantom was developed for this purpose.

Purpose of the Study:

• To present a commissioning procedure for the ARDOS phantom.
• To benchmark the phantom for 4D dose verification in proton therapy.
• To evaluate CT calibration, dose calculation accuracy, and detector performance within the phantom.

Main Methods:

• Characterized ARDOS materials using CT imaging and measured relative stopping powers (RSP).
• Benchmarked Monte Carlo (MC) dose calculations against Farmer chamber measurements.
• Assessed pinpoint ionization chambers, thermoluminescence dosimeters, and EBT3 film for dose verification.

Main Results:

• Overriding CT parameters improved RSP accuracy for rib and soft tissues; balsa wood accurately modeled lung tissue.
• MC dose calculations showed <3% difference with measurements; analytical algorithms differed >20% from MC.
• Detectors showed up to 5.5% difference from MC, detecting motion-induced dose distortions; EBT3 film suitable for 2D relative dose mapping.

Conclusions:

• The ARDOS phantom and presented commissioning methodology are suitable for 4D dose verification in proton therapy.
• Results support the development of general recommendations for dynamic phantom commissioning.
• This is essential for end-to-end evaluation of motion mitigation techniques in ion beam therapy.