What is the clinically acceptable limit of flatness over the central 80% of the x-ray beam used in radiotherapy?

In radiotherapy, flatness of the x-ray beam is critical for ensuring uniform dose distribution to the target tissue while minimizing dose to surrounding healthy tissue. The acceptable limit of beam flatness is defined to ensure that the radiation dose delivered is consistent across the treatment area.

The clinically acceptable limit of flatness over the central 80% of the x-ray beam is typically set at 2%. This means that the variation in dose should not exceed 2% within this region of the beam. Adhering to this standard is essential for maintaining treatment efficacy and safety, as significant deviations could lead to either underdosing or overdosing the target area, potentially compromising treatment outcomes and increasing the risk of side effects.

Limits tighter than 2%, such as 1% or lower, are desirable in certain specialized situations, but the standard acceptable range for routine clinical practice is recognized as 2% for beam flatness. This standard is established by professional organizations to guide the quality assurance processes in radiation therapy.