Fig. 10.

Parallax effect. (a) Lateral radiographs of the upper lumbar spine in a 12 year-old girl treated with glucocorticoids for mixed connective tissue disease shows non-overlapping endplates, especially at L2 (arrows), due to parallax. (b) A follow-up image obtained 3 years later shows overlapping endplates without parallax effect (arrow). (c) Diagram of parallax effect. The side of the object closest to the X-ray source is magnified and eccentrically positioned compared to the other side. For vertebrae, this gives an appearance of bone-in-bone, or endplate interruption. This is minimized by using a source as far away as possible, and centering the beam appropriately