Monte Carlo Commissioning of Low Energy Electron Radiotherapy Beams using NXEGS Software

Area of Science:

• Medical Physics
• Radiation Oncology
• Computational Dosimetry

Background:

• Accurate dose calculation is crucial for radiotherapy.
• Monte Carlo methods offer high precision but require robust beam modeling.
• Automated commissioning tools can streamline this process.

Purpose of the Study:

• To report on the commissioning of low-energy electron beams using NXEGS software.
• To evaluate the accuracy of NXEGS-generated beam models for Monte Carlo dose calculations.
• To assess the impact of commissioning data parameters on NXEGS performance.

Main Methods:

• Commissioning of 6, 9, and 12 MeV electron beams from a Varian Clinac 2100C using NXEGS software.
• Automated commissioning process combining analytic and Monte Carlo methods.
• Collection of dosimetric data including central axis depth-dose, beam profiles, and output factors in a water phantom.

Main Results:

• NXEGS successfully commissioned the electron beams, generating dose distributions comparable to measurements.
• Confidence limits for error measures were typically below 3% or 3 mm.
• Accuracy showed a slight decrease at increased source-to-surface distance (SSD) and depth beyond R(50).
• NXEGS performance demonstrated weak dependence on the number of dose profiles but required data from only two SSDs.

Conclusions:

• NXEGS software provides accurate beam models for Monte Carlo dose calculations of low-energy electron beams.
• The automated commissioning process is efficient and reliable.
• Further optimization of commissioning data acquisition is possible, reducing measurement requirements.