Fig. 1.

a PMMA phantoms placed around the ionization chamber for measuring doses relative to a mouse and rat. b Front view of dose measurement set-up in low magnification mode showing the system geometry listed in Table 1. c Side view of dose measurement set-up in normal mode. The total x-ray beam width at rotation axis is defined as N × T × SOD/SDD, where the parameters are defined in Table 1. For the low magnification mode shown here this equates to 0.0495 × 2352 × 108/203 = 61.94 mm. For the high magnification mode (not shown) this equates to 0.0495 × 2352 × 55/203 = 31.543 mm.