(a)[6]
Briefly explain the principles behind CT scanning.
(b(i))[1]
A simple body section is made up of four voxels, as shown in Fig. 10.1. An X-ray image of the section is produced by looking along each of the directions shown in Fig. 10.1. The detector readings for each viewing direction are added to produce the pattern of readings shown in Fig. 10.2. For any one direction, the total of the detector readings is $16$. For the pattern of readings of Fig. 10.2, state the size of the background reading.
(b(ii))[2]
On Fig. 10.1, mark the pixel pattern for the four-voxel section.