Where does the heel effect distribute more radiation intensity on the image receptor?

• A. at the cathode side of the image receptor
• B. at the anode heel
• C. at the anode toe
• D. at the anode side of the image receptor

Answer: (A)

Intensity along the X-ray beam is not uniform because of the anode heel effect. The anode target is angled, and photons emitted toward the anode side must pass through more of the target material and are more likely to be absorbed by the anode. This absorption reduces the number of photons that reach the image receptor on that side. Photons emitted toward the cathode side encounter less material and are less attenuated, so more of them reach the receptor there. As a result, the image receptor shows greater radiation intensity on the cathode side. This effect becomes more noticeable with steeper anode angles and higher kVp, and is often used to optimize exposure by positioning the thicker part of the anatomy toward the cathode side.