# Tutor Hunt Questions

I’m attempting to plot how image noise varies as a function of gantry position for a CT scanner, and the effect of changing table height on noise signal. I think it can be solved by trigonometry but struggling to visualise and model the scenario – any help would be much appreciated!
7 years ago

Physics Question asked by Grace

Please enter your response to the question below. The student will get a notification as soon your response has been approved by our moderation team.

You must be doing something at PhD level? I know that this is a question and not an answer.
Answered by [Deleted Member]

The noise (Quantum Mottle) received from CT scanners relates to the intensity of the X-rays. If the intensity is too low, there will be a limited number of photons detected that will appear as random fluctuations on the screen. Attenuation of the output is important.
You will need to consider the geometry of a cone, from the X Ray source to the detectors. The lower the source the broader the field, etc., I assume you are ignoring radial effects? You will need to review the Radon Transform and how this relates to your experiment - this will give you the geometric outline.
Answered by [Deleted Member]
- 1

Well you have to look at it as if it`s a signal:noise ratio. So as we`re looking at how the noise changes as a function we have to plot the data of noise in a graph with curves. This can be done in excel to make things easier to visualise. Using excel you can then work out the gradients at points of the graph and see it as more of a function. No trigonometry involved haha.
Answered by [Deleted Member]
- 1