Geometric parameters of clinical electron beams

Area of Science:

• Medical Physics
• Radiation Oncology
• Particle Physics

Background:

• Therapy accelerators deliver electron beams for cancer treatment.
• The treatment head's components influence beam geometry.
• Understanding these geometric properties is crucial for accurate dosimetry.

Purpose of the Study:

• To analyze the influence of treatment head components on electron beam geometric properties.
• To develop an effective electron source model for simplifying beam analysis.

Main Methods:

• Analysis based on the theory of small angle multiple scattering.
• Computation of an effective electron source model.
• Numerical example to illustrate effective source properties.

Main Results:

• An effective electron source can be defined and computed.
• This source, placed in vacuum, replicates the real beam's electron fluence at the patient.
• The effective source is characterized by angular spread, radial width, and distance from the patient.

Conclusions:

• The effective electron source model simplifies the understanding of electron beam delivery.
• The model's parameters (angular spread, radial width, distance) are key for accurate treatment planning.
• Effective source width can be substantial, especially at lower electron energies.