10-MV x-ray primary and scatter dose calculation using convolutions.

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Accurate dose calculation is crucial for effective radiation therapy.
• Heterogeneous media and electronic disequilibrium pose challenges in dose computation.
• Existing methods may lack precision in complex scenarios.

Purpose of the Study:

• To develop novel three-dimensional (3-D) forward and backward primary dose spread functions for 10-MV x-rays.
• To adapt these functions for use in heterogeneous media using the density scaling theorem.
• To evaluate the effectiveness of these functions in regions with electronic disequilibrium.

Main Methods:

• Development of 3-D primary dose spread functions in water for 10-MV x-rays.
• Construction of functions for heterogeneous media via density scaling.
• Convolution of primary water collision kerma distribution with dose spread functions for primary dose calculation.
• Separation and calculation of scatter dose components using differential scatter methods.

Main Results:

• Successfully developed and implemented 3-D forward and backward primary dose spread functions.
• Demonstrated the effectiveness of these functions in heterogeneous media.
• Validated the method using dose calculations and measurements in phantoms with cork and aluminum slabs.
• Confirmed efficacy in regions with loss of longitudinal and/or lateral electronic equilibrium.

Conclusions:

• The developed 3-D dose spread functions are effective for 10-MV x-rays, particularly in challenging heterogeneous environments.
• The density scaling theorem provides a robust method for adapting water-based functions to heterogeneous media.
• These advancements offer improved dose calculation accuracy, especially where electronic equilibrium is compromised, benefiting radiation therapy planning.