What tube angle is recommended for a radiograph of an anteroposterior (AP) projection of the fifth digit when focusing on joint spaces?

For an anteroposterior (AP) projection of the fifth digit, a tube angle of 15 degrees cephalic is recommended to optimize the visualization of the joint spaces. This slight angulation helps to project the joint spaces more clearly onto the imaging receptor, reducing the potential for superimposition of adjacent structures or bones that can obscure the details of the joint being examined.

In this context, the cephalic angle directs the X-ray beam toward the head (or toward the source of the body's upper structure) which helps to better delineate the anatomy of the digit's joints. This is particularly vital for the fifth digit, where the joint spaces can be very narrow and may easily be lost without proper angulation. The choice of 15 degrees is specifically intended to enhance the diagnostic quality of the radiograph while minimizing distortion.

The other tube angle options do not effectively serve the purpose of visualizing joint spaces for this specific projection. For instance, a 0-degree angle would result in a direct AP projection that might not adequately separate the joint spaces. An angle of 30 degrees caudal might be too steep for this area, and a 45 degrees cephalic angle could potentially distort the anatomy further than necessary, leading to