New compensator design options for charged-particle radiotherapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Physics

Background:

• Proton therapy requires precise dose delivery to maximize tumor control and minimize normal tissue toxicity.
• Compensators are crucial for shaping the proton beam's dose distribution.
• Existing compensator designs may not adequately address challenges like patient motion and critical structure sparing.

Purpose of the Study:

• To develop and evaluate novel compensator design strategies for proton and heavier particle therapy.
• To utilize pencil-beam (PB) dose calculations for improved compensator design.
• To reduce dose to tissues downstream from the target while ensuring acceptable target coverage during patient motion.

Main Methods:

• Proposed new compensator design strategies based on pencil-beam (PB) dose calculations.
• Incorporated averaging and expansion operations for improved target coverage with patient motion.
• Included a structure-sparing option to protect downstream critical structures.
• Evaluated designs on two patients with skull-base tumors.

Main Results:

• New PB compensator designs achieved target coverage comparable to or better than standard designs in aligned conditions.
• Averaged PB compensators reduced the volume of normal tissue receiving >95% of the prescription dose by approximately half compared to standard designs.
• In cases of patient motion, averaged PB compensators showed only a modest 3% decrease in target volume coverage compared to expanded standard compensators.

Conclusions:

• The novel compensator design strategies offer superior protection for normal tissues distal to the target volume.
• These PB-based designs provide a favorable balance between normal tissue sparing and target coverage, even with patient motion.
• The proposed methods represent an advancement in radiotherapy planning for proton and heavier particle treatments.