What occurs when the anode angle decreases?

When the anode angle of an x-ray tube decreases, it results in a smaller effective focal spot size (FSS). This smaller effective FSS is beneficial in improving image detail and sharpness because it allows for better resolution. Additionally, a decrease in the anode angle leads to an increase in the heel effect. The heel effect refers to the variation in x-ray intensity across the radiation beam, where the intensity is greater on the cathode side (where the x-rays are emitted) and weaker on the anode side.

This phenomenon occurs due to the geometry of the x-ray beam and how x-rays are produced; as the angle of the anode decreases, the path length through the target material increases for the x-rays emitted toward the anode side, resulting in additional attenuation of the beam on that side. Thus, the distribution of x-ray intensity becomes more pronounced, exacerbating the heel effect.

Therefore, as the anode angle decreases, the effective focal spot size decreases while the heel effect increases. This relationship is critical for radiographers to understand in order to optimize image quality and manage exposure levels effectively in clinical practice.