Figure 16.

Three of the many approaches for DOI detector modules. On the left, layers of crystals are offset so that each crystal is visible in a crystal map similar to that of figure 5. In the center, light is collected from each end of a crystal and the ratio of the light collected provides DOI information. On the right, light is shared between paired crystals by modifying the common interface such that light at one end is not shared between PMT elements while light at the other end is shared ~50%. The ratio of light from the paired crystals provides the DOI information.