What is the recommended collimation for the tangential projection of the sesamoids?

• A. 2-3 inches on either side
• B. 4-6 inches on either side
• C. 0-1 inch on either side
• D. 1-2 inches (3-5 cm) on either side of the foot

Answer: (D)

Precision in collimation is key when you’re imaging the tiny sesamoid bones. You want a field that covers the sesamoids and a small margin of surrounding tissue, but not the entire foot, to keep the image high in contrast and minimize unnecessary exposure. For the tangential projection of the sesamoids, a width of about 1–2 inches (3–5 cm) on either side of the foot provides just enough room to visualize the sesamoids and the base of the first metatarsal while avoiding excess tissue that would add scatter and radiation dose. Too little space risks clipping the sesamoids; too much space exposes more of the foot and degrades image quality with extra scatter. This range strikes the right balance for accurate visualization and patient safety.