Collimation must be accurate within what percentage of the SID?

Collimation accuracy in radiography is crucial because it affects both patient safety and image quality. Proper collimation ensures that only the area of interest is irradiated, minimizing the exposure of surrounding tissues to unnecessary radiation. The standard for collimation accuracy is set to ensure optimal imaging while adhering to safety guidelines.

The requirement for collimation to be accurate within 2% of the source-to-image distance (SID) is based on established radiographic practices. For example, if you have an SID of 100 cm, the acceptable level of collimation must be within 2 cm of the light field, meaning the x-ray beam should closely conform to the area that will be exposed. This level of precision helps maintain image quality and reduces the risk of radiation exposure to the patient.

The other percentages mentioned in the options do not align with the established standards in radiology. A tolerance of 1% would be overly restrictive and impractical in most clinical settings, while tolerances of 3% and 4% could compromise image quality and increase patient exposure unnecessarily. Thus, the 2% requirement represents a balance between quality assurance and practical application in radiographic practice.