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CT Physics - what is the correct single measure for the scanner radiation output?

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I'm interested in having a single numeric measure for the scanner's radiation output in a single scan.

The motivation is to use this measure to look at the corellation between radiation output and problems in image quality (It's clear that the corellation will not be full, but I want to find the single measure that makes most sense for this goal).

For this reason, there are a few requirements from this measure:

  1. The measure should be (as much as possible) standardized for all scanner manufacturers and models.

I'll explain what I mean with this using a hypothetic example - if this measure is kVp (it's not, but just as a hypothetic example) - I want 80 kVp to have a very similar meaning between different manufacturers and models (which to my understanding, it does. Unfortunately - KVP doesn't provide the full information of radiation output because it lacks the information of the current).

  1. Should be able to calculate it from DICOM metadata fields that are reliable and appear in all scanner models (e.g. tube current, rotation time, pitch, [effective exposure, calculated from the previous], kvp, etc.)

​

My questions:

For simplification - let's assume tube current modulation is not used (I'm trying to understand the physics in a very controlled scenario, to begin with).

  1. Please keep me honest that the motivation makes sense (find corellation between radiation output and problems in image quality using a single measure).
  2. From what I understand, CTDIvol is the closest to what I'm looking for. Please let me know if you agree, and where it deviates from my requirements.

Specifically, does it answer requirement #1 (standartization)? For example - for all scans with KVP 80 and 50 mAs effective exposure, should I expect the CTDIvol to be very similar/identical in all of these scans (across different manufacturers)? If not - why not and how different will it be?

  1. In parallel, CTDIvol doesn't appear in the DICOMs produced by many scanner models. Could you explain why that is the case?

  2. Which measure best answers my requirements in your opinion?

submitted by /u/louis_imad
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source https://www.reddit.com/r/Radiology/comments/hbd82c/ct_physics_what_is_the_correct_single_measure_for/
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