What is the proper central ray angle and direction for the axial projection of the calcaneus when the ankle is dorsiflexed?

For the axial projection of the calcaneus with the ankle in dorsiflexion, the central ray needs to be angled correctly to obtain the best visualization of the heel bone. A central ray angle of 40 degrees cephalad is appropriate in this case.

Dorsiflexing the ankle allows the foot to be positioned so that the long axis of the calcaneus is aligned for optimal imaging. The cephalad angle directs the x-ray beam toward the heel and helps demonstrate the subtalar joint and the overall anatomy of the calcaneus more clearly. This angulation also minimizes superimposition from adjacent structures, providing a clearer view of the calcaneus itself.

Using a 40-degree cephalad angle specifically is optimal as it has been established through practice and anatomical understanding that this allows for the best visualization of the calcaneus in a standard positioning technique for this projection. The other angles listed would not position the beam effectively for clear imaging of the calcaneus and its surrounding structures.