A method to select aperture margin in collimated spot scanning proton therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Particle Therapy

Background:

• Collimators and apertures sharpen lateral dose gradients in spot scanning proton therapy.
• A standardized method for determining aperture margins in proton therapy is currently lacking.

Purpose of the Study:

• To develop a theoretical framework for selecting optimal aperture margins in single-field collimated spot scanning proton therapy.
• To establish the spot spacing limit necessary for the existence of an optimal aperture margin.

Main Methods:

• Proposed an optimal margin equal to the maximum pencil beam center shift.
• Determined the required spot spacing limit based on beam modeling data.
• Validated the method with a test case.

Main Results:

• The theoretical framework provides a method for optimal aperture margin selection.
• A specific spot spacing limit was identified for the existence of the optimal margin.
• The test case demonstrated agreement with the proposed method's predictions.

Conclusions:

• The proposed method offers a way to determine optimal aperture margins in proton therapy.
• This approach can be implemented in commercial treatment planning systems for improved precision.