The heel effect is more pronounced with which condition?

• A. Higher kVp
• B. Larger field size
• C. Smaller field size
• D. Shorter source-to-image distance

Answer: (B)

The heel effect is caused by self-absorption of photons within the anode as the target is angled. Because photons directed toward the anode side pass through more of the anode material, there’s less intensity on that side and more toward the cathode side. This variation across the field becomes more noticeable as the field size increases, since a larger field exposes a wider range of angles and path lengths through the anode, amplifying the difference in intensity from the cathode to the anode edge.

So, a larger field size increases the heel effect, making the intensity gradient across the image more pronounced. Higher kVp, shorter SOD, or smaller field sizes don’t enhance this gradient as effectively.