Figure 10.

The optimal swale-depth $s_d^{*}$ can be reduced by decreasing magnification and by choosing x-ray tube and detector that minimize x_t and x_d, respectively. Assuming a 5 mm mechanical clearance for the x-ray tube, x_t = 52.5 mm and 37 mm, were obtained from Boone (Boone, 2004) and from specifications of M-1500 x-ray tube (Varian Medical Systems), respectively. Assuming a similar clearance for the detector, x_d = 39.2 mm and 23.6 mm, were obtained from specifications of the PaxScan® 4030CB and PaxScan® 4030MCT, respectively (Varian Medical Systems). Computations were performed assuming L^M =5 mm. The arrow labeled A indicates $s_d^{*}$ for the system geometry in (Boone, 2004) and the arrow labeled B indicates $s_d^{*}$ for a recently installed system at our institution.