According to the line-focus principle, using a small effective focal spot is associated with high anode heating, and as the target angle decreases, what happens to the effective focal spot?

• A. Increased Anode Heating; The Effective Focal Spot Increases
• B. High-Anode Heating; The Effective Focal Spot Increases
• C. High-Anode Heating; The Effective Focal Spot Decreases
• D. Increased Anode Cooling; The Effective Focal Spot Decreases

Answer: (C)

Line-focus principle tells us that you can heat-dissipate with a larger actual focal spot while presenting a smaller effective focal spot to the image receptor. The effective focal spot is the projection of the actual focal spot onto the imaging plane. When the target angle is reduced, this projection becomes smaller, so the effective focal spot decreases. The trade-off is that heat is deposited over a longer path on the angled target, increasing the anode heat load. So, as the target angle decreases, the effective focal spot gets smaller while anode heating rises.