Radiology Tech Physics Practice Test

Anode heel effect describes a gradient of x-ray intensity across the field caused by the angled target in the anode. Because the anode is tilted, photons emitted toward the anode side have to pass through more tungsten and are partly absorbed within the target, so fewer exit toward that side. In contrast, the cathode side has higher intensity because fewer photons are absorbed in the anode. This creates a brighter area on the image receptor toward the cathode side and a darker area toward the anode side. The effect is more noticeable with larger field sizes and steeper anode angles (and is less pronounced with small fields or longer distances). In practice you can use this to your advantage by placing the thicker part of the anatomy toward the cathode side so the higher exposure helps compensate for greater attenuation there, or by adjusting technique to achieve more uniform density if positioning cannot optimize the heel effect.