Production and use of X-rays — practice question

Outline briefly the principles of computed tomography (CT scanning).

One part of a model created to demonstrate CT scanning is split into four voxels. The pixel numbers K, L, M and N of the voxels are shown in Fig. 10.1. The section is then viewed, in turn, from four different directions $D_1$, $D_2$, $D_3$ and $D_4$, as shown in Fig. 10.1. The detector readings for each direction are recorded and added to give the values shown in Fig. 10.2. The background reading is 24. Determine the pixel numbers K, L, M and N shown in Fig. 10.1.