A small anode angle results in which two of the following?

A small anode angle results in which two of the following?

• A. Decreased focal spot size and Decreased heat capacity
• B. Increased focal spot size and Increased heat capacity
• C. Decreased focal spot size and Increased heat capacity
• D. Increased focal spot size and Decreased heat capacity

Answer: (A)

Smaller anode angles reduce the size of the X-ray source as it appears in the image and also limit how much heat the anode surface can safely absorb per exposure. When the bevel is shallow, the projection of the actual focal spot onto the image plane becomes smaller, so the focal spot size is decreased. At the same time, heat is deposited over a smaller area of the anode, which lowers the heat-dissipation capacity (heat capacity). In other words, a small anode angle tightens the focal spot and reduces the area available to spread heat, increasing thermal stress and lowering the tube’s heat capacity. If the angle were increased, the focal spot would appear larger and the heat capacity would increase, which is why the given option reflects both decreased focal spot size and decreased heat capacity.