What is the function of a scattering foil in a clinical accelerator?

The function of a scattering foil in a clinical accelerator is to spread the accelerator's "pencil beam" into a larger field. In radiation therapy, particularly when using electron beams, the treatment area often requires a uniform dose distribution over a wider area than what the narrow pencil beam provides.

The scattering foil achieves this by introducing a layer of material that interacts with the beam, causing the charged particles—primarily electrons—to scatter. This scattering process expands the beam's width and makes it suitable for treating larger tumors or areas, ensuring that the entire treatment volume receives an adequate dose while maintaining a precise and controlled radiation delivery.

While the other functions mentioned—such as absorbing radiation, correcting beam quality, or reducing patient dose—are critical components in the overall design and safety of radiotherapy equipment, they do not encompass the primary purpose of the scattering foil, which is specifically to ensure an optimal treatment area is achieved by spreading out the pencil beam.