A-LevelPhysicsMedical physics9702/41 · Oct/Nov 2017 · Q97 Marks
In computed tomography (CT scanning), it is necessary to take a series of many X-ray images. Outline briefly the principles of CT scanning.
- (a)In computed tomography (CT scanning), it is necessary to take a series of many X-ray images. Outline briefly the principles of CT scanning.[4]
- (b)A student creates a model for CT scanning. A section is divided into four voxels, with pixel numbers A, B, C and D, as shown in Fig. 9.1. [Figure 9.1] The section is viewed from four different directions V₁, V₂, V₃ and V₄, as shown in Fig. 9.1. The detector readings for each direction are noted and then summed. The result is shown in Fig. 9.2. [Figure 9.2] The background count is 26. Determine the pixel numbers A, B, C and D as shown in Fig. 9.1.[3]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2017). The mark or mark type is shown in brackets.
- [B1] image of one slice/section
- [M1] images (of one slice) taken from different angles
- [A1] to give 2D image (of one slice)
- [M1] (repeated for) many slices
- [A1] to build up 3D image (of whole body/structure)
- [C1] evidence of subtraction of background (-26)
- [C1] evidence of division by three
- [A1] A=7
- [A1] B=11
- [A1] C=6
- [A1] D=2
Write your answer and get it marked
On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.
Sign up free →