For my research on Coronary Artery Calcium Scoring I want to calculate the CAC mass score. Therefore I need a calibration factor for 100 kV CT scans. Does a standardized calibration factor exist for 100 kV Coronary Artery Calcium scans?
I found a log summary through google in which such calibration factors where considered. See the attached document.
As far as I know there is no calibration factor. The increased noise at 100kV is a severe limitation for calcium score quantification. Basically, you could have more false positives and increased values as compared to standard 120kV scans.
You are right about the image noise.
I found articles published on Agatston, Mass and Volume scoring in 100 and 80 kV scans. With an increased HU threshold it is possible to get similar results as with 120 kV calcium scoring for Volume and Agatston calcium scoring.*
For mass scoring I also need the calibration factor. After I read the Log Summary I added to my original post, I was hoping these calibration factors existed for different CT scanners and scanner settings.
* 2009 Nakazato et al.: 'Coronary artery calcium scoring using a reduced tube voltage and radiation dose protocol with dual-source computed tomography'
I think your decision to measure mass scores is a great decision. You can do machine specific calibration or patient and scanner specific calibration, I prefer the latter. I have done a great deal of work in this area. You have access to a strong group there but if I can help please contact me ([email protected]). I don't see the increased noise as a factor but would encourage you to use small voxels ( increases the noise but increases the signal even more) and to calibrated with simultaneous scans of a calibration phantom. If you want to dig deeper, you might want to read this paper: Peak SNR in automated coronary calcium scoring: Selecting CT scan parameters and statistically defined scoring thresholds. Medical Physics, Vol. 37, No. 7, July 2010
Good luck, Ben Arnold
I agree with the above comment. You probably need to do your own calibration. Mass scores seem to be attactive to the Ph.D.'s as they can accurately quantitate the amount of calcium. They may not however be the best measurement depending upon what you are trying to look at. My own feeling is that a mass score is not the best way to look prognosis or risk of an event. Lower density calcified plaques are probably more likely to rupture and cause events, even though they contribute little to the mass score. You can email me ([email protected]) if you want to discuss this further.
Interesting discussion.
I think some form of calibration would be most welcome. Nowadays, in thin patients where we perform CCTA with prospective triggering and 100kV, the radiation dose of calcium scoring (at 120kV) almost equals the radiation dose of CCTA...
You can use 100 and 80 kV scans with specific calibration , the result are similar to 120 kv, every one must make the own machine calibration, own stratification according results.
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