American Registry of Radiologic Technologists (ARRT) Practice Exam

The anode heel effect is most noticeable when imaging with a large image receptor (IR) and a short source-to-image distance (SID). This phenomenon occurs due to the geometry of the x-ray tube and the way that x-rays are produced at the anode. As x-rays pass through the anode, they experience varying degrees of attenuation based on their angle of emission. X-rays emitted toward the cathode side tend to be more intense than those emitted toward the anode side.

When using a large IR, there is a greater area where the differences in exposure due to the anode heel effect can be detected. With a short SID, the x-ray beam diverges more quickly, enhancing the visibility of the exposure variation across the IR because the distance between the x-ray tube and the IR creates a larger gradient of x-ray intensity. This effect is particularly evident when imaging larger anatomical areas, as the differences in intensity can lead to uneven exposure across the IR, making the distinction more noticeable.

In contrast, options involving a small IR or long SID would result in a less pronounced impact of the anode heel effect, as the smaller area would not demonstrate the gradient as effectively, and the increased distance in the longer SID would allow for more uniform