What reduces exposure to ionising radiation during a radiograph?

Collimation of the beam effectively reduces exposure to ionising radiation during a radiograph by limiting the size and shape of the x-ray beam to the area of interest. By accurately targeting the beam, collimation minimizes the amount of surrounding tissue that is exposed to radiation, thus decreasing the overall dose received by the patient and reducing scattering, which can degrade image quality.

The use of fast film can decrease the amount of radiation needed to produce a diagnostic image, but it doesn't limit exposure like collimation does. Reducing the kilovoltage (Kvp) also may lead to increased exposure times, as lower Kvp can reduce penetration and require more radiation to achieve an adequate image. The use of an open and lead-lined cone is designed to direct and shield the x-ray beam but doesn’t optimize the beam coverage like collimation. In contrast, collimation is a direct method for focusing the radiation and safeguarding non-target areas, making it the most effective choice in this context.