The central ray entrance point for a medial oblique foot radiograph is at the base of which metatarsal?

• A. Base of the first metatarsal
• B. Base of the second metatarsal
• C. Base of the fifth metatarsal
• D. Base of the third metatarsal

Answer: (D)

Centering the beam at the base of the third metatarsal is standard for a medial oblique foot projection because this location lines up with the foot’s midline when the foot is rotated medially about 30 degrees. This placement places the midfoot and forefoot joints—including the tarsometatarsal and surrounding joints—near the center of the image, producing a more uniform magnification and reducing distortion. The oblique angle helps separate overlapped bones, making the joints more visible.

If the central ray were placed at the base of the first or fifth metatarsal, the image would shift off the foot’s center, leading to uneven magnification, potential clipping of important joints, and poorer visualization of the midfoot structures.