0:01

Perfusion evaluation can be accomplished

0:04

both with CT CTP as well as MR MRP.

0:09

This is an example of a patient who had a diffusion

0:13

weighted MRI scan, in which the volume of tissue that

0:18

was abnormal on the threshold ADC value and the

0:24

Tmax value greater than six seconds was calculated.

0:28

And what one found on this example was that

0:32

there was 21 ccs of brain tissue, which had an ADC

0:37

value less than 600 seen on these ADC maps.

0:42

But the perfusion volume with a Tmax

0:45

greater than six seconds was 43 ccs.

0:50

This implies that there is tissue that is salvageable

0:54

that can be determined on the perfusion volume.

0:58

That was not infarcted already on the ADC map.

1:04

So we have 22 ccs of brain tissue, which

1:09

is still salvageable through thrombolysis

1:12

or thrombectomy or medical therapy.

1:16

So in this case, if you put the 43 over the

1:19

21, we have A-P-W-I-D-W-I mismatch ratio of.

1:22

2.0, as I said on the CT profusion, usually

1:27

the number that they're looking at is 1.2 or

1:29

higher, which means that it would be an eligible

1:32

candidate for thrombolysis and intervention.

1:36

The Xtend one A was one of the

1:39

multi-institutional trials of intra-arterial.

1:45

Thrombectomy and their target mismatch of values that

1:49

they looked at was a core volume of stroke of 70 ccs.

1:53

Now, that may be measured on the D-W-I-A-D-C map,

1:57

or it may be measured on the cerebral blood flow

2:00

less than 30% map, a mismatch ratio of greater

2:04

than 1.2 compared to the Tmax, either on the MR.

2:10

Perfusion or the CT perfusion and a

2:12

mismatch volume of greater than 10 ccs.

2:15

So once there's a mismatch volume of greater than 10

2:18

ccs, it seems like it's worthwhile to intervene because

2:22

the patient's prognosis improves through thrombectomy.

2:27

Alternatively, you may just use, see the

2:29

numbers, 1.2, mismatch ratio and volume greater

2:32

than 10, and not looking at the core volume

2:35

of greater than 70 ccs in some of the other.

2:39

Multi-institutional trials.

2:41

Here are the results from the mismatch profile on

2:46

mechanical thrombectomy, and this was from 2020,

2:50

and it shows that when you have the mismatch

2:55

volume of 1.2 or greater and a higher

2:58

reperfusion rate occurs, you have a better response

3:02

to that thrombectomy or intravenous thrombolysis.

3:05

In this case, it was mostly a

3:06

mechanical thrombectomy trial.

3:09

Whereas those that don't have a mismatch, of which there

3:12

were only about 20% of the cases, these patients did

3:15

not do as well from the standpoint of their prognosis.

3:19

So again, out of all the patients that

3:21

they looked at, 80% had a mismatch volume.

3:24

You can see the difference

3:25

between the pink versus the green.

3:27

So there's tissue to be salvaged here.

3:31

When they looked at these patients, 90% were

3:33

reperfused and they had a better prognosis.

3:36

Those patients who had a matched volume, no

3:39

mismatch, and these were only 20% of all

3:42

the patients presenting, they reperfused at 70%.

3:45

But even with the reperfusion, even

3:47

with the mechanical thrombectomy, their

3:49

prognosis did not improve significantly.

3:53

I wanna make sure that, although I've

3:55

emphasized the rapid analysis software and

3:59

the other packaging of computer-assisted.

4:02

Assessment of perfusion that you understand that

4:06

you shouldn't have a blind reliance on the software.

4:09

It's not as if, oh, you know, there's no problem here

4:12

at six seconds and therefore I don't have to worry.

4:15

For example, in this patient here, there was

4:18

zero ccs of Tmax greater than six seconds, but

4:22

the Tmax greater than four seconds, which is

4:24

below the threshold that neurology is using.

4:27

You can see all this blue area.

4:30

Of abnormality, and this corresponded to the

4:33

posterior cerebral artery distribution in

4:35

this patient where the patient had a stenosis.

4:39

So although it didn't meet the threshold for

4:42

analysis based on a Tmax of six seconds, there

4:46

was a large area of tissue which was showing

4:51

a difference from right to left, and therefore

4:54

you might still point that out as part of your.

4:58

Reporting.

4:59

This patient had zero ccs of the CBF

5:03

less than 30%, so we say no stroke.

5:07

But as you noticed at CBF, less than 38%,

5:10

there was an area here of blue representing the

5:14

diminished cerebral blood flow, which corresponded

5:17

to that area of Tmax greater than four seconds.

5:22

Wanna, again, emphasize that while we do report

5:25

those values that the neurologists are using, use

5:28

your common sense in commenting on areas where

5:33

you see perfusion deficit from right to left.

5:36

Here, for example, was a patient.

5:38

Who again, did not have threshold that

5:41

showed stroke, but I called this, I said,

5:44

you know, this is the cerebral blood flow.

5:46

There is an area where it's blue, darker area here on

5:50

the right side along the medial paramedian frontal lobe,

5:55

and when I look at the Tmax, I see an area of perfusion

5:59

deficit, which does not meet the six second qualifier.

6:03

But still I'm concerned that this patient has

6:07

potentially ischemic tissue, and here correspondingly.

6:13

Also within the posterior cerebral artery distribution

6:16

is an area in the occipital lobe, which shows

6:19

asymmetry from right to left, so appropriate

6:22

to report it even though it does not meet the

6:26

numerical threshold for a perfusion deficit.