Which of the following projections would NOT take advantage of the "heel effect" if the cathode end was aimed toward the head?

The "heel effect" refers to the phenomenon where the intensity of the X-ray beam is greater on the cathode side (where the X-ray tube's cathode is located) than on the anode side. This uneven distribution can be advantageous in certain imaging scenarios to ensure that the denser parts of the anatomy are better visualized.

In this case, when the cathode end is aimed toward the head, the radiation intensity on the head side will be greater than on the opposite side. Among the choices, the anatomic structures featured in the AP Thoracic Spine projection are horizontally aligned along the axis of the X-ray beam, and the thoracic spine itself has varying densities. Therefore, the increased intensity on the cathode side is less beneficial here. The primary focus of the AP projection would be to obtain an even exposure across the thoracic vertebrae rather than selectively enhancing the image density of one side, making this projection not utilize the heel effect effectively.

In the other projections listed, alignment and positioning make them better suited to take advantage of the heel effect. For example, the Lateral Femur and Lateral Thoracic Spine projections are oriented such that the denser portions of the anatomy are captured on the more intense side of the