Comparison of analytic source models for head scatter factor calculation and planar dose calculation for IMRT

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Accurate dose calculation is critical for intensity-modulated radiation therapy (IMRT).
• Head scatter modeling is essential for precise planar dose calculations in IMRT.

Purpose of the Study:

• To identify the optimal head scatter source model for fast and accurate planar dose calculation in IMRT.
• To evaluate the performance of single, two-, and three-source models for head scatter modeling.

Main Methods:

• Compared three head scatter source models (single, two-, and three-source) for IMRT dose calculation.
• Incorporated fluence perturbations (tongue-and-groove, rounded leaf end, leaf transmission).
• Validated dose calculations against diode array measurements using 2%/2 mm and 3%/3 mm criteria.

Main Results:

• The two-source model demonstrated the best agreement for head scatter factor calculation.
• All models achieved comparable average passing rates (>97%) with the 3%/3 mm criterion.
• Single and two-source models offered faster calculation times compared to the three-source model.

Conclusions:

• The two-source head scatter model is recommended for fast and accurate IMRT dose calculations.
• Model selection impacts accuracy and computational speed, with the two-source model providing a favorable balance.
• Further investigation may be needed for specific field configurations and inclusion of backscatter effects.