Lateral electron transport in FFT photon dose calculations

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Dosimetry

Background:

• Fast Fourier Transform (FFT) dose calculations are established for larger field sizes (>10 cm x 10 cm) and photon energies up to 18 MV.
• Lateral electronic disequilibrium in low-density inhomogeneities at smaller field sizes and megavoltage energies is not accurately handled by standard FFT calculations.

Purpose of the Study:

• To extend FFT dose calculations to accurately address lateral electronic disequilibrium in inhomogeneous media.
• To improve 3D FFT dose calculations without significant increases in computational time.

Main Methods:

• Implementation of lateral scaling of field size at each depth.
• Application of inverse scaling of the resultant dose distribution.
• Introduction of the concept of effective density for scaling adjustments.

Main Results:

• Demonstrated adequate capture of electron transport in the presence of inhomogeneities.
• Achieved improved accuracy in 3D FFT dose calculations within inhomogeneous media.
• Maintained computational efficiency compared to previous methods.

Conclusions:

• The enhanced FFT method effectively improves dose calculation accuracy in complex, inhomogeneous environments.
• This advancement is crucial for precise radiation therapy planning and delivery.
• The technique offers a computationally efficient solution for challenging dosimetry problems.