Interactive Transcript
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Cardiac CT, there are generic artifacts
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and some special to the procedure.
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There are multiple ways of
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categorizing these artifacts.
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The way I think about them is motion,
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ECG synchronization, and acquisition.
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They have different solutions.
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Some have no solutions, and
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some have immediate solutions.
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So here's an example of an artifact
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that's kind of there, not much you can do
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about, and that's poor contrast bolus.
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There's nothing you can do about it at
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that time except for maybe scan the patient
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again if you're not happy with the quality.
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But it's obviously worthwhile
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thinking why there was poor contrast.
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And it could be patient factors or it could be
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technical factors such as timing of the bolus,
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where the tracker was placed, what the patient's
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injection fraction is, so on and so forth.
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Here's another artifact that is a consequence of the
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scan duration, which is known as the banding artifact.
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Thank you. And it happens because from the start
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of the study to the bottom of the study, that
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is, the start of the field of view to the bottom
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of the field of view, contrast density changes.
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It generally happens when you
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take a long time to, um, acquire.
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And these slabs are like these kind of,
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you know, boundaries between the two time
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zones of contrast and classification.
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So really not much you can do about
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these, just be aware of why they occur.
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And, um, just.
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Be careful not to call stenosis at
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a point where the band goes through.
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There are others that may have some solutions.
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One is the imaging noise.
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You can deal with that by increasing the MAS,
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although that would be in a subsequent study.
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So something to kind of put in the report
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so that future CT operators would be aware.
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At the time, you can increase the slice thickness.
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That will come with some
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degradation of spatial resolution.
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And the third is iterative reconstruction.
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Which is offered on certain scanners, not all
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scanners, and that simply is post-processing.
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So it's a post-processing solution, which is very neat.
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The example I'm giving you is quite dramatic,
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no doubt, but there are grainy images that have
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been improved with the iterative reconstruction.
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An easy one to resolve is motion artifact,
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if you have more than one phase.
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This typically occurs in the RCA, which, by virtue of
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where it lives in the anterior AV groove, moves a lot.
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It moves one of the most out of all of the arteries.
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So you could reconstruct a diastolic phase,
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like 75%, and find that it works for everything.
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The LAD, the distal RCA, the circumflex, and find that
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the mid RCA is stubborn and doesn't respond to it.
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And to deal with that, you just have to go
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back, if you've done retrospective gating, and
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find a different phase, maybe a systolic phase.
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If you have prospective gating, then clearly,
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you only have one shot at it and therefore
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you can't correct for such artifacts.
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It's important first and foremost when
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you see motion artifacts to decide
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whether it's respiratory or cardiac.
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Because if it's cardiac, it could
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be from ECG synchronization.
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If it's respiratory, then there's not a whole
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lot you can do except for making sure that
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your future breath hold instructions are good.
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So the way to distinguish the two
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is that if you have a respiratory
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motion, then look at the sternum and you'll
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get a stair-step artifact in the sternum.
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Cardiac pulsation is just
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restricted to the heart and the things
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that connect with the heart, like
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the pulmonary arteries and the aorta.
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The sternum is not affected by cardiac motion.
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