SU-E-T-24: Development and Implementation of an Automated Algorithm to Determine Radiation Isocenter, Radiation vs....

Area of Science:

• Medical Physics
• Radiation Oncology
• Imaging Technology

Background:

• Accurate radiation isocenter localization is critical for precise radiotherapy delivery.
• Current methods for isocenter verification can be time-consuming and subjective.
• Need for a standardized, objective tool for routine quality assurance in radiation therapy.

Purpose of the Study:

• To develop a novel phantom and analysis software for rapid and accurate radiation isocenter determination using EPID.
• To enable the phantom for additional quality assurance tests, including radiation-light field coincidence, MLC/jaw tests, and OGP calibration.

Main Methods:

• A phantom constructed from LEGO® blocks was imaged using EPID at various gantry and collimator angles.
• Custom software analyzed EPID images to determine jaw positions and phantom center.
• Isocenter accuracy was verified against independent measurements, achieving accuracy comparable to detector pitch.

Main Results:

• The developed algorithm demonstrated objective repeatability in reproducibility tests.
• The phantom and software are linac vendor-independent, with successful validation on two major manufacturers' machines.
• Integrated OGP calibration array allowed for reduced setup uncertainty during OGP calibration at the radiation isocenter.

Conclusions:

• The proposed solution provides a swift and objective method for isocenter localization.
• Facilitates routine monthly quality assurance, including laser alignment and OGP calibration.
• Enhances overall efficiency and accuracy in radiation therapy quality assurance procedures.