Minimizing clearance issues with prone breast patients on Varian linear accelerators through isocenter placement

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Prone positioning in breast irradiation minimizes normal tissue dose and skin toxicities.
• Immobilization devices for prone breast treatments can cause linear accelerator (LINAC) collisions, impacting patient experience and treatment delivery.

Purpose of the Study:

• To develop an isocenter location guideline to prevent collisions between prone breast immobilization devices and LINAC gantry heads.
• To ensure that adherence to these guidelines results in clinically acceptable treatment plans.

Main Methods:

• Retrospective analysis of 14 patients with pre-existing collision issues.
• Re-planning treatments using newly established clearance isocenter guidelines.
• Comparison of collision-prone plans with plans created within clearance thresholds based on RTOG 1005 recommendations.

Main Results:

• Established clearance isocenter guidelines by measuring physical space between immobilization devices and LINACs.
• Demonstrated that re-planning with these guidelines successfully prevented collisions.
• Confirmed that clearance plans remained clinically acceptable.

Conclusions:

• A clearance isocenter location guideline is feasible for prone breast irradiation.
• These guidelines effectively prevent LINAC collisions with immobilization devices.
• Clinically acceptable treatment plans can be achieved while ensuring collision-free delivery.