Fig 4

X-ray positioning jig with radiograph.

A, X-ray positioning jig in an upright position. To obtain a lateral radiograph, we placed a euthanized rat in the jig with its spine toward the convex curve, and radiolucent filler was packed into the cylinder to force the spine into mild extension. The cylinder was placed on its side (note, “this side down”) on an x-ray cassette, and the exposure was made.

B, Lateral radiograph of a rat within the x-ray positioning jig. The PBA (*) is formed by the intersection of lines drawn along the posterior body margins of L4 (arrowhead) and L6 (arrow).