The intensity of x-rays increases from the anode side toward the cathode side because of the

The intensity of x-rays increases from the anode side toward the cathode side because of the

• A. The line-focus principle
• B. Actual focal spot size
• C. The inverse square law
• D. The anode heel effect

Answer: (D)

The across-field intensity change is due to the anode heel effect. Because the anode target is angled, photons emitted toward the anode side pass through more of the anode material and are attenuated more, while photons toward the cathode side pass through less material and emerge with higher intensity. This geometry creates a brighter beam on the cathode side and a dimmer one on the anode side. The other options involve focal spot geometry or distance-based intensity, which don’t produce this lateral gradient across the beam.

The across-field intensity change is due to the anode heel effect. Because the anode target is angled, photons emitted toward the anode side pass through more of the anode material and are attenuated more, while photons toward the cathode side pass through less material and emerge with higher intensity. This geometry creates a brighter beam on the cathode side and a dimmer one on the anode side. The other options involve focal spot geometry or distance-based intensity, which don’t produce this lateral gradient across the beam.