Technical note: TERMA scaling as an effective heterogeneity correction model for convolution-based external-beam...

Area of Science:

• Medical Physics
• Radiotherapy
• Computational Dosimetry

Background:

• Conventional convolution methods overestimate radiation dose in heterogeneous media (e.g., lung tissue, air cavities).
• This overestimation is particularly pronounced in low-density regions or downstream from them.
• Accurate dose calculation is critical for effective radiotherapy.

Purpose of the Study:

• To develop a method for correcting overestimated radiation dose calculations in heterogeneous media.
• To introduce a scaling method for total energy released per mass (TERMA) to improve dose accuracy.
• To enhance the reliability of dose calculations in complex anatomical sites.

Main Methods:

• Proposed a novel method involving scaling the total energy released per mass (TERMA).
• The scaling factor is determined by the density distribution and the effective lateral beam size.
• Implemented and evaluated the corrected convolution method.

Main Results:

• The corrected convolution method significantly improved dose calculation accuracy in lung-like tissue.
• Enhanced accuracy was also observed in water-like regions following air cavities.
• The TERMA correction added only approximately 10% to the overall computational cost.

Conclusions:

• The proposed dose calculation method demonstrates improved accuracy in heterogeneous media.
• The method preserves computational efficiency, making it suitable for clinical applications.
• This approach is valuable for enhancing inverse treatment planning accuracy and effectiveness.