Multi-collimator proton minibeam radiotherapy with joint dose and PVDR optimization

Area of Science:

• Medical Physics
• Radiation Oncology
• Biomedical Engineering

Background:

• Clinical translation of proton minibeam radiation therapy (pMBRT) faces challenges in treatment planning for optimal anti-tumor efficacy and normal tissue sparing.
• Achieving uniform target dose and high peak-to-valley dose ratio (PVDR) in organs-at-risk (OAR) is critical but difficult, especially for distal OARs or when patient-specific collimators are needed.

Purpose of the Study:

• To propose a novel pMBRT treatment planning method, multi-collimator pMBRT (MC-pMBRT), that simultaneously achieves high PVDR in OARs and uniform dose in the target.
• To introduce a joint dose and PVDR optimization (JDPO) algorithm for MC-pMBRT to balance these competing objectives.

Main Methods:

• MC-pMBRT employs a set of generic, premade multi-slit collimators, eliminating the need for patient-specific devices.
• Collimator selection is OAR-specific to maximize PVDR while maintaining target dose uniformity.
• The JDPO method jointly optimizes target dose uniformity, OAR PVDR, and other dose-volume histogram objectives using iterative convex relaxation and alternating direction method of multipliers.

Main Results:

• MC-pMBRT demonstrated a superior balance between OAR PVDR and target dose uniformity compared to single-collimator approaches.
• Compared to conventional proton RT, MC-pMBRT (both JDPO and dose-only optimization) preserved target dose uniformity and plan quality while achieving unique OAR PVDR.
• The JDPO method further enhanced PVDR in OARs compared to dose-only optimization within the MC-pMBRT framework.

Conclusions:

• The proposed MC-pMBRT method, utilizing generic collimators and JDPO, effectively optimizes OAR-specific PVDR and target dose uniformity simultaneously.
• This approach offers a promising solution for advancing pMBRT clinical translation by improving normal tissue sparing without compromising therapeutic efficacy.