Which statement correctly describes the relationship between SID and size distortion?

Which statement correctly describes the relationship between SID and size distortion?

• A. Size distortion increases with a longer SID
• B. Size distortion decreases with a longer SID
• C. SID has no effect on magnification
• D. Size distortion cannot be predicted from SID

Answer: (B)

Size distortion, or magnification, comes from how the X-ray beam projects the object onto the receptor. When the Source-to-Image Distance is longer, the beam reaches the object and the receptor with less angular divergence, so the image of the object on the receptor is closer to its true size. In other words, a longer SID reduces the magnification of the projection, decreasing size distortion. This is why increasing SID is a common way to minimize distortion. The other statements conflict with this geometric relationship: SID does affect magnification, magnification isn’t unpredictable from SID, and enlarging SID does not increase magnification.

Size distortion, or magnification, comes from how the X-ray beam projects the object onto the receptor. When the Source-to-Image Distance is longer, the beam reaches the object and the receptor with less angular divergence, so the image of the object on the receptor is closer to its true size. In other words, a longer SID reduces the magnification of the projection, decreasing size distortion. This is why increasing SID is a common way to minimize distortion. The other statements conflict with this geometric relationship: SID does affect magnification, magnification isn’t unpredictable from SID, and enlarging SID does not increase magnification.