Electron dose rate and photon contamination in electron arc therapy

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Understanding electron beam dosimetry is crucial for precise radiation therapy.
• Rotational electron beams offer potential advantages but require careful dosimetric characterization.

Purpose of the Study:

• To investigate the electron dose rate at the depth of dose maximum (dmax) and photon contamination for rotational electron beams.
• To determine the functional relationships between dose rates and beam parameters like field width and isocenter depth.

Main Methods:

• Utilized a pseudoarc technique with 10-degree angular increments and constant monitor units per field.
• Defined electron dose rate as dose at a point divided by monitor units for a stationary beam.
• Analyzed dose rate dependencies on nominal field width (w) and isocenter depth (di).

Main Results:

• Electron dose rates at dmax showed a linear dependence on field width (w) for a fixed isocenter depth (di).
• Dose rates were inversely proportional to isocenter depth (di) for a fixed field width (w).
• Photon dose at the isocenter was found to be proportional to arc angle (alpha) and isocenter depth (di), and inversely proportional to field width (w).

Conclusions:

• Electron dose rate at dmax is predictable based on field width and isocenter depth.
• Photon contamination at the isocenter is dependent on multiple rotational beam parameters.
• Photon dose at the isocenter is inversely related to the electron dose rate at dmax, offering insights for treatment planning.