What is the recommended source-to-image distance (SID) for tangential sesamoid radiographs?

• A. 60 inches (152 cm)
• B. 20 inches (50 cm)
• C. 1 inch
• D. 40 inches (102 cm)

Answer: (D)

For tangential views of the sesamoid bones, the goal is a projection that shows the small structures clearly with minimal distortion. The recommended source-to-image distance is 40 inches (102 cm) because this distance provides the right balance between magnification and sharpness for the tiny sesamoids while allowing the beam to strike tangentially to outline them well. Using this SID helps the sesamoids appear in proper profile without overlapping adjacent anatomy. If a much shorter distance were used, the bones would appear larger and less sharp; a much longer distance would reduce exposure efficiency and isn’t the standard setup for this view. So, 40 inches is the standard SID for tangential sesamoid radiographs.