A generalized extension to the Hounsell-Wilkinson head scatter model

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Physics

Background:

• The scatter-plane source model accurately describes head scatter for irregularly shaped fields from Elekta linear accelerators.
• Elekta linac head design, with the solid jaw below the multileaf collimator (MLC), simplifies head scatter source definition.
• More complex linac head designs, like the Siemens Primus, feature an upper jaw pair with MLC jaws positioned further from the source, complicating scatter modeling.

Purpose of the Study:

• To generalize the scatter-plane source model for accurate head scatter description in complex linear accelerator head designs.
• To evaluate the applicability of the Hounsell and Wilkinson model to Siemens Primus linear accelerators.
• To present results of the generalized model for typical treatment field shapes on a Siemens Primus.

Main Methods:

• Extension of the Hounsell and Wilkinson scatter-plane source model.
• Application and validation of the generalized model on a Siemens Primus linear accelerator.
• Analysis of head scatter for irregularly shaped fields relevant to clinical radiotherapy.

Main Results:

• The original Hounsell and Wilkinson model shows limitations in accuracy for Siemens Primus linac head designs.
• The generalized scatter-plane source model demonstrates improved accuracy for head scatter in irregularly shaped fields on the Siemens Primus.
• The study provides validated results for typical treatment field shapes, enhancing radiotherapy planning accuracy.

Conclusions:

• A generalized scatter-plane source model is necessary for accurate head scatter calculations in complex linear accelerator head designs.
• The developed model provides a more accurate description of head scatter for Siemens Primus linacs compared to previous methods.
• This advancement contributes to improved precision in radiotherapy treatment planning for irregularly shaped fields.