Planar dose calculation of electron therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Accurate calculation of electron beam dose distribution is essential for effective radiation therapy.
• Irregular beam shapes pose challenges in precise dose determination at maximum depth (zmax).
• Existing methods require refinement for complex geometries in clinical practice.

Purpose of the Study:

• To determine the planar dose distribution of irregularly-shaped electron beams at zmax.
• To validate modified lateral build-up ratio (LBR) and curve-fitting methods for irregular electron beam dosimetry.
• To improve the accuracy of dose calculations in electron therapy for non-standard field shapes.

Main Methods:

• Utilized Cerrobend alloy for creating circular and irregular cutouts in a 14x14 cm2 applicator.
• Measured Percentage Depth Dose (PDD) and point doses at various Source-Surface Distances (SSD).
• Employed modified LBR and curve-fitting models, validated against EDR2 film measurements in solid water.

Main Results:

• Calculated planar dose distributions for irregular electron beams at zmax.
• Achieved agreement within 3% between calculated and measured dose profiles.
• Demonstrated a gamma passing rate exceeding 96% (3%/3 mm, 10% threshold).

Conclusions:

• The improved LBR method and curve-fitting model accurately predict electron beam planar dose distributions for irregular cutouts at zmax.
• This approach offers a reliable tool for enhancing dose calculation accuracy in electron therapy.
• The findings support the clinical implementation of these methods for precise treatment planning.