Where is the intensity of the x-ray spectrum produced by a linear accelerator maximum?

The intensity of the x-ray spectrum produced by a linear accelerator is maximized at the central axis. This phenomenon occurs due to the geometric and physical principles governing radiation distribution.

In linear accelerators, the imaging and therapeutic beams diverge from their source, following the law of inverse square distance, which means that as the distance from the source increases, the intensity decreases. At the central axis, the beam is more collimated, providing a higher and more uniform dose to the target area. The intensity is highest here because the beam’s intensity profile is typically designed to be most effective for treatment at this point, ensuring the dose is delivered optimally to the tumor while sparing surrounding healthy tissues as much as possible.

As such, the central axis is essential in treatment planning, as dosimetrists use this information to achieve precise dose distributions that are critical for successful patient outcomes.