Figure 8.

(a) The left pane shows plots of the measured axial response of a point source centered in ξ=24. The right pane shows plots of the measured axial response of a point source centered in ξ=25. (b) (not to scale) A schematic representation of the cross section of the scanner with septa present. The dashed lines represent the geometric tubes of interaction for the individual detector pairs for ξ centered at crystal number 3. The point source located at the center of ξ−2 (the center of crystal 2) will not contribute to ξ when it is located at d=0, but will move into the volume that is sampled by ξ at larger d values.