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These are images of a 72-year-old male

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with a facial droop and right sided weakness,

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and slurred speech.

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This is the non-contrast CT,

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and you can see that there's some hyperdensity

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in the left MCA.

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There is some subtle hypodensity

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in the left basal ganglia and

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maybe some white matter hypodensity.

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Hard to tell on the non-contrast head CT.

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He also has a small subdural collection

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along the falx.

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So, we're going to take a look at our

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CTA source images,

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and

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you can see on the left,

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we'll just follow the left common carotid artery,

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internal carotid artery.

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You can see there's a severe stenosis,

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just distal to the origin,

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and then there's a string sign in the left

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internal carotid artery compared

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to the right internal carotid artery,

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and

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follow that vessel all the way up.

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And basically,

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there's some clot at the top of the ICA

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going into the A1,

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and then going into the MCA stem,

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and goes into the bifurcation.

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And when you look at the CTA source images,

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again, there's some subtle hypodensity in

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the pure basal ganglia.

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A little...

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pretty hard to judge the white matter.

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Maybe it's getting a little bit of frontal cortex.

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Hard to be sure exactly.

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We're going to look at our MIP images,

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and we can see there's an MCA stem embolus.

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There's some good collaterals distally and...

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So now, we're going to look at the CT perfusion images.

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This is a summary of what you get

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from the CT perfusion images.

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And this is the CBF,

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thresholded CBF,

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and you can see what was calculated as core

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is the top of the basal ganglia

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and some deep white matter on the left.

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Obviously,

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there's some spurious signal on the right side,

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which you have to ignore.

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So probably, this is overestimating

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the core a little bit.

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And then, the T max greater than 6 seconds is 136 cc.

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So, there's a large area of tissue at risk,

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and the mismatch ratio is much greater than 1.8.

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So, there is tissue at risk.

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In the appropriate clinical setting,

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this could be a candidate for thrombolysis.

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And then,

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what they'll also send you are these maps

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where it shows T max greater than 6 seconds,

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so it's green,

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but they show you what happens

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if you do T max greater than 4,

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which is going to be...

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it's going to be a larger area.

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It's tissue that's not that ischemic.

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It's just that mild delay in the transit time.

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And then sometimes they just...

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they show higher up, like 10 seconds.

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That's probably going to be estimating

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the core a little bit more.

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But basically,

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the cut-off we use is 6 seconds.

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And then, this also shows the RCBF.

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Again, the cutoff is 30%

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so you're going to look at the yellow,

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but they say,

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what if we just look at, you know,

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20% compared to the contralateral side?

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So that would be a smaller area.

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I don't see any of that here.

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Or if we look at it higher, 38%,

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it's going to be a larger area

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and you start to get some spurious measurements.

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So, they'll just show you that.

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But basically, you will kind of want to stick to

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the 30% cut-off for RCBF

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and the T max of six cut-off for the penumbra.

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And then,

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you have to look at,

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make sure that the arterial and input function, AIF,

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and the venous output function, VOF,

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are accurate.

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And so, this is a good curve.

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It should have a sharp peak and it should return

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to baseline.

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If it doesn't do that,

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then it probably wasn't measured correctly.

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And then,

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this is the venous output function.

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Same thing.

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It should start a little bit later than arterial function,

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you go up a little bit higher in Hounsfield units

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and go back to baseline.

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So, those are normal curves.

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If you don't see a normal curve,

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you're going to get spurious measurements.

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You want to take a look at that.

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And then they also give you motion detection

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on the x, y, and z-axis

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to show you how much your images are being

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affected by motion.

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There is an automatic motion correction algorithm,

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which they use to try to make sure

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you're getting accurate information.

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And then, these are the actual maps.

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Again, we're given CBV and mean transit time,

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but the measure of transit time we actually

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use is T max and we're using our CBF.

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And these are just the raw data maps,

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and you can see the lower signal in the superior

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aspect of the basal ganglia and in the

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white matter on the left side.

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And on the T max maps,

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we can see the cut-off of six is approximately green,

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but most of this is even higher.

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It's going up to ten.

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So, large area of tissue at risk.

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This just shows all the images.

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And then, this will show you the arterial input function.

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You know,

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it's usually the top of the ICA or the proximal

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MCA, where you've got robust enhancement.

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The venous output function is typically in the

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superior sagittal sinus or in the torcula

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where you can get a clean ROI.

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So, this patient had some risk factors,

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did not go to thrombolysis.

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Here's the infarct on MR.

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Again, showing lateral and superior aspect

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of the basal ganglia.

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Probably not quite as much white matter

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as you saw on the CTP,

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but pretty close.

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But what happened is that this patient

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spontaneously reperfused,

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and the follow-up CT really doesn't show

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infarct extension.

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So, spontaneously reperfused,

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vessel opened up.

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The tissue at risk did not infarct.

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This is a subacute infarction.

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There's some swelling and mass effect

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on the left lateral ventricle.