Slide 15 of 16
Notes:
In order to obtain a true picture of the noise-dose relationship on each of the scanners, we have applied a correction factor to the noise values to compensate for the measured variations in z-sensitivity.
And when we plot out these corrected noise values for the single-slice and multi-slice scanners together, a number of points become apparent.
Firstly, there is a remarkable similarity between the results for the three multi-slice scanners. At pitches above about 1.25, they have a noise-dose relationship close to that of the single-slice scanner, but, by maintaining this relationship for all pitches, they achieve a progressively better noise-dose relationship than the single-slice scanner at pitches below 1.25.
This is perhaps of most relevance around a pitch of 1, since a single-slice scanner would not normally be used clinically below pitch 1. Whilst on the single-slice scanner there is about 15% more noise in helical mode than axial at pitch 1, on the multi-slice scanners the noise-dose relationship in helical mode is roughly equal to that in axial mode.
The second observation is that, on the Volume Zoom and the Mx8000, there do not appear to be any special pitches where the noise-dose relationship is significantly better than at other pitches. This fits in best with Siemens’ claim.