Use of IAEA's phase-space files for virtual source model implementation: Extension to large fields.

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Dosimetry

Background:

• The hybrid virtual source model (VSM) accurately simulated clinical photon beams for field sizes up to 15x15 cm² using IAEA phase-space data.
• Limitations existed for larger field sizes due to the unavailability of phase-space data.

Purpose of the Study:

• To extend the virtual source model (VSM) for clinical photon beams to accommodate larger field sizes.
• To develop a comprehensive VSM applicable to any field size by integrating a virtual flattening filter.

Main Methods:

• Incorporated a virtual flattening filter into the existing VSM framework.
• Determined the virtual flattening filter parameters using standard dose measurements for larger fields.
• Utilized publicly available IAEA phase-space data (phsp) and dose measurements.

Main Results:

• The extended VSM, incorporating the virtual flattening filter, accurately models clinical photon beams for field sizes beyond 15x15 cm².
• The model demonstrates good agreement with dosimetric measurements for a wider range of field sizes.
• A fully functional VSM tailored to specific linear accelerators can be constructed.

Conclusions:

• The enhanced virtual source model (VSM) provides accurate dosimetric predictions for clinical photon beams across all field sizes.
• This approach enables the creation of personalized VSMs using IAEA data and standard measurements, improving treatment planning.
• The method overcomes limitations of phase-space data availability for large fields in radiation therapy.