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How To Transcranial Doppler

[Music]

so today we're lucky enough to be

performing a transcranial duplex study

using the trans-temporal approach and

Scott is going to be actually performing

the exam and we'll be talking about what

we're visualizing on the screen we start

out with the grayscale display and then

we will use the intracranial landmarks

to then help us know what we're looking

at with the intracranial anatomy and the

vasculature so we'll begin by focusing

with the transducer positioned on the

temporal window and Scott is angling

ever so slightly to optimize the

grayscale display and to document the

intracranial bony landmarks and we will

be we're using the landmarks to help us

know sort of where we are and where to

position the the color box for

displaying flow of the vascular Anatomy

now Scott's going to talk as well and

tell us what he's looking at on our

perfect model and obviously in the

clinical setting your patients may not

always be this cooperative and they may

not be this young and have good temporal

bones but this really is a wonderful

demonstration of how well you can

visualize the intracranial anatomy it's

really quite remarkable so that even in

an optimal a suboptimal patient we can

probably get very good results and these

landmarks are where we're going to start

with the P tristin sphenoid bones and as

we angle as when I turn color on I'm

going to expect to see the crowded

siphon in this area and we'll do a

little adjusting with the transducer to

go ahead and get the siphon

that's beautiful

it certainly makes it easier to have

that color display when you're trying to

identify the vasculature or that just

blindly looking for a signal we'll go

ahead and throw pulse-doppler on here

now we are using a transducer this is

using a frequencies of between five and

one megahertz okay so we will go ahead

and sample this so this system has an

actual transcranial software package so

that the the main velocity is going to

automatically be calculated when you

place the envelope follower in place and

it will be optimizing the signal for TC

D come out of Doppler and we're just

going to angle a transducer and come up

into the Circle of Willis looking at the

MCA and the ACA just turn the color gain

up a little bit now as with non imaging

we can tell the difference in the

vasculature based on flow direction so

the color is very helpful in not only

demonstrating the course of the vessel

and the curves and the and the you know

the position of the vessel but also the

flow direction so we can clearly see the

middle cerebral artery which is the

larger and the more robust of the

vessels and then the anterior cerebral

artery moving towards the midline in

addition you can actually see the

contralateral acá at MCA as well as

Scott is positioned the sample volume

within the middle cerebral artery

you can see a nice envelope follower a

nice spectral display and

even a little bit of a reverse flow here

where he's picking up a probably a

branch vessel so the sample volume depth

is at about five centimeters that you

can see the display of the peak systolic

velocity as well as the end diastolic

which are also used in the overall

calculation of the data but the mean

velocity or the time averaged peak is 58

centimeters per second and as I walk

shallower with the sample volume we're

coming up in vm2 segment which is right

around here you can see it on great on

color Doppler very easily as far as

where the m1 and m2 segment that's

beautiful so now if you change the size

of the sample volume

you just show them so if I decrease it

came down to a sample volume size here

of four millimeters and we're up on the

M 270 but normally most of the

literature has used a fairly large

sample volume because it helps you find

the vessel and track the vessel more

easily I think if you make the sample

volume so small you're you're looking

for small vessels and having a small

sample volume is really just going to

make it much more difficult so a fairly

large sample volume is usually optimal

take that back to seven and a half and

we're going to come down we've sampled

the MCA all the way out already come

down and look at the MCA to a CA and

this should be bi-directional flow

showing both vessels and as I take my

sample volume slightly deeper we will

drop into the ACA so this is really the

most repeatable and reliable

inter-cranial landmark and it's what we

always go back to as really the the

resource for knowing where we are and

what we're evaluating this is the area

where we would expect to find increased

velocities and children with sickle cell

anemia or in patients with vascular

disease because as we know at

bifurcations that tends to be the point

at which we have higher velocities so

that's beautifully the distance so you

can really track that I see a quite a

distance yeah okay so that helps you

make sure that you know that you follow

the ACA and that you've tracked it to

the midline as far as we're going to go

okay now can you show me again the ICA

because that's really a critical vessel

and one that's very difficult to

evaluate with the non-imaging there we

go so it it almost is circular

elliptical and because you've angled a

little inferior inferior and I did a

small clockwise rotation of the

transducer very slightly okay okay and

you can hear a little harshness there in

the ICA which is what we normally expect

a little bit of baseline disturbed flow

there as well and that's beautiful we'll

go back to our landmark and now we will

angle posterior with my color box and

look at the posterior branch posterior

segments

so the reason this is important is that

in the days before we had the beautiful

images we would sometimes follow the PCA

if it was carrying a lot of collateral

flow and miss collet is the middle

cerebral artery so we found that it was

very helpful to know that we had

documented the the anterior and the

posterior circulation separately so that

shows the top of the basilar where the

basilar artery has bifurcated into the P

1 section segments of the PCA and then

there you can see the color

differentiation and then as the vessels

wrap around the brainstem you can see

that they actually appear to change

direction - because of their angling

so once again at the midline we have a

almost a bi-directional signal again

because we if we increase the size of

the sample volume you actually can get

both PCs at that point so that you can

see the PC a mean flow velocity is much

lower than we saw in the middle cerebral

artery and that's another hallmark sign

that you have actually separated the

entry in the posterior circulations very

nice just angling

so that will be the p2 SEC segment

that's really nice so if we could just

go back and show them sort of the the

course of the MCA and changing the color

box and showing how that impacts the

quality

so if we were doing a full clinical exam

we would track through the entire course

and take samples at each it what do you

usually do four millimeters to four four

milliliters because with the nine image

you couldn't see so we did it too but

with the imaging because you can

visualize the vessel I think four is

probably adequate also very easier to

with visualization of the vessel you can

walk it right through the sample volume

exactly pinpoint the exact area where

you have the highest velocity we narrow

our color box here we will see better

frame rates and you're actually

increasing your color sensitivity so if

you had a patient who had vasospasm or

very tight stenosis this might help you

optimize the signal better I'm just

going to increase my colour prf slightly

to reduce some of the aliasing at the

peaks this to leak in the MCA actually

see some of the branches in the MCA out

there

distal portion that's very nice

so should we go closer yes we'll try

posterior so when you want to evaluate

the posterior circulation and look at

the vertebral basilar system you just

have the patient we were turned to their

side and tilt their chin to their to

their chest so that you can actually

open up this area and have them relaxed

so that it doesn't get the muscles don't

get too tight so you're actually shining

the trends the the ultrasound through

the opening of the foramen magnum

and just searching around looking for

the best window and once you have your

vessels you can just turn on your

transducer to be able to follow those

into the skull

that's beautiful

very nice

so the sample volume isn't it about 5.5

so you can see this the peak systole in

the posterior circulation is quite a bit

lower than the anterior circulation

which is what you would expect then you

can just track the vessels and depending

on the patient presentation whether

they're a vascular disease patient you

may want to look at the vertebral

advisor or whether it's just documenting

flow with the TCD study for as a

baseline roll to just not really seeing

me

there was

very nice okay so when we're doing that

the orbital exam particularly in

children if you find it necessary to do

it it's good to put the the gel over the

on the transducer you know I do have an

orbital preset on the system that I can

go into that will automatically reduce

my power levels okay so we're using a

mechanical index of 0.1 all right and if

we need B we can't go lower oh wow

that's beautiful

so we're positioning the transducer over

the eye the closed eyelid and angling so

that we can evaluate the flow in the up

thalmic artery wow it's beautiful

so normally when the flow is coming up

the the ophthalmic artery is the first

branch of the internal carotid so the

flow would be towards the transducer

coming out of the orbit if the

ophthalmic is serving is a collateral

and we would see actually a reversal in

this signal this can also be used to

track the ophthalmic into the siphon and

evaluate the crowd siphon particularly

if you have an older patient who has a

very thick skull and you can't get a

good signal you can actually evaluate

the siphon but I would imagine with the

with the imaging systems that you really

don't encounter that problem too much

anymore you can generally assess the

temporal window very nice so that would

be a complete transcranial imaging exam

thank you Scott thank you