A customizable, open-source Winston-Lutz system for multi-target, single isocentre radiotherapy.

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Quality Assurance

Background:

• Single-isocenter, multi-target radiotherapy requires precise targeting accuracy verification.
• Traditional Winston-Lutz tests are limited to single targets at the isocenter.
• Existing quality assurance methods may not adequately address multi-target scenarios.

Purpose of the Study:

• To present an open-source system for verifying targeting accuracy in linac-based, single-isocenter, multi-target radiotherapy.
• To extend the Winston-Lutz test for multi-target quality assurance.
• To provide a customizable phantom and software for quality assurance.

Main Methods:

• Development of a 3D-printed, customizable phantom for various target (BB) positions.
• Software generation of multi-leaf collimator positions for multi-target Winston-Lutz (MTWL) plan creation.
• Hough circle detection algorithm for locating BBs on MV images, with modifications for improved accuracy.
• Validation using synthetic data and comparison with a commercial system for real linac targeting errors.

Main Results:

• Synthetic data validation showed a mean absolute discrepancy of 0.11 mm (maximum 0.21 mm).
• Comparison with a commercial system yielded a mean absolute discrepancy of 0.13 mm (maximum 0.43 mm).
• Repeatability tests among three physicists on two linacs resulted in a mean absolute discrepancy of 0.14 mm (maximum 0.51 mm).

Conclusions:

• The open-source system successfully verifies targeting accuracy for multi-target, single-isocenter radiotherapy.
• The system demonstrates comparable accuracy to commercial solutions and good repeatability.
• This quality assurance tool enhances confidence in the geometric accuracy of complex radiotherapy treatments.