The dorsoplantar projection of the foot requires a CR direction of how much and in which direction?

• A. 10° anteriorly to the base of the third metatarsal
• B. 10° posteriorly to the base of the third metatarsal
• C. 5° laterally to the fifth metatarsal
• D. 5° medially to the first metatarsal

Answer: (B)

In the dorsoplantar projection of the foot, the central ray (CR) direction is essential for accurately capturing the anatomical structures without distortion. For this projection, the CR is angled 10° posteriorly toward the base of the third metatarsal.

This posterior angulation helps to compensate for the natural convolution of the foot and ensures that the image is focused correctly, providing a clearer view of the bones and articulations. This projection is particularly important for visualizing the tarsals, metatarsals, and phalanges in a way that best represents their spatial relationships. The choice of the third metatarsal as the reference point is also significant since it is centrally located and provides a consistent landmark for positioning.

The other options suggested different degrees or directions of angulation that would not provide the optimal view necessary for diagnostic purposes in a dorsoplantar projection. The posterior angulation is key to minimizing distortion and achieving an accurate representation of the foot's anatomy on the radiograph.