General Core of Radiography – Limited Scope Practice Test

When the automatic exposure control is used, the exposure stops once the detectors under the patient reach a preset signal. If the beam is not tightly collimated, a larger portion of the patient is irradiated, which means more tissue for the X-rays to pass through and more scatter produced. To achieve the required detector signal with this extra tissue and scatter, the system often delivers more radiation (increasing mA/seconds or duration). That extra radiation raises the patient dose and tends to produce a brighter image, i.e., overexposure. Tight collimation minimizes unnecessary tissue and scatter, helping the AEC reach the target signal with less dose.