ESTRO 2024 - Abstract Book

S4841

Physics - Quality assurance and auditing

ESTRO 2024

The film is analyzed with Fortran code to find the maximums and minimums at 6.5 cm (+/- 1.5 cm averaging) distance from the defined isocenter. The gantry angles and isocenter radius are determined from the maximum intensity points found, using an iterative algorithm to minimize the isocenter radius.

Results:

The average gantry angle difference across all machines and angles was 0.12 +/- 0.11 degrees, and the maximum average difference for a specific angle and machine was 0.26 degrees. The gantry angle difference was not found to be significantly machine or angle dependent on our measurements. These results fit within the department’s QA protocol limit of 0.5 degrees. The average isocenter radius across all machines and angles was 0.14 +/- 0.11 mm, and the maximum average radius for a specific angle and machine was 0.36 mm. The isocenter radius was not found to be significantly machine or angle dependent on our measurements. These results are well within the average MPC isocenter size of 0.57 mm and the department’s QA protocol limit of 1.5 mm.

Conclusion:

We have demonstrated that the Star Shot film analysis can accurately determine the gantry angles and isocenter radius of a Halcyon treatment unit. The Star Shot film analysis can be used to determine both the gantry angles and the isocenter radius simultaneously.

Keywords: Star Shot, Halcyon, SRS

References: