0:00

All right, basic, basic ankle

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pulsing sequences, 3 Tesla.

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This time, the foot is not plantar flexed for

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the tendons, but rather dorsiflexed or neutral.

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In other words, the ankle and the foot

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are almost at right angles to each other.

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Why this positioning?

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Unfortunately, radiologists love this

0:24

because they're used to the angles.

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They're used to a right-angle orientation

0:29

for the ankle. It makes their perception

0:32

of the anatomy a little more comfortable.

0:36

On the other hand, it may ruin their MRI

0:40

perception of long structures like tendons, as

0:43

we've already alluded to in prior vignettes.

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So if you give me a choice, do

0:47

I want the ankle dorsiflexed or

0:49

plantarflexed, I'd say plantarflexed.

0:54

Now if you said beginner, new to MRI, I'd

0:58

say back to you, you know what, Okay, time.

1:01

is important, but for right now, let's do them

1:04

plantarflexed and dorsiflexed so the learner,

1:07

the viewer, the student gets a feel for the

1:10

anatomy of both, and then as time goes on we

1:13

move them towards the plantarflexed situation.

1:17

This is a very sophisticated practice.

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It's a 3 Tesla and there's no

1:22

more than five sequences here.

1:25

On the left is a T2 fat suppression,

1:29

excellent for ligaments. The quality of

1:34

ligaments, not necessarily the best detector

1:36

sequence, but a good qualifier sequence.

1:40

And we'll scroll through it.

1:42

We're not going for the anatomy so much.

1:44

Just to illustrate, one, the field of view

1:46

is a lot smaller than what you've seen

1:48

before, so we're going to see a little

1:50

more detail, even though prior studies that

1:53

you've seen were of also very high quality.

1:56

But look at the tendons.

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They're curving, because the foot

2:00

is dorsiflexed or not plantarflexed.

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Look at the peronei.

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They're curving.

2:07

So now we've introduced that extra variable that

2:11

has to be dealt with in the short-axis projection.

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People also like this, this sagittal

2:19

projection, uh, that is not plantar

2:22

flexed because the patients are often

2:24

more comfortable in this position.

2:26

You know, they don't like having their

2:27

foot taped into a plantar flexed position

2:30

or lying on their stomach all that much.

2:32

Still, that is the preferred position.

2:35

Now on the far right, this At 3 Tesla, we have

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superb fat suppression. The bones are very

2:43

dark, the soft tissues are also very dark.

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So for those of you that are new to

2:48

MRI, this is where you go to find

2:51

stuff, to look for the hot spots.

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This is your bone scan type sequence.

2:56

All I want to know is where's it hot?

2:58

It's a little hot over here, okay, the

2:59

deltoids a little swollen, big deal.

3:02

There's a little fluid over here,

3:03

nothing around it, no big deal.

3:06

But this takes you to the areas.

3:08

Where there could be a potential problem.

3:12

So, for my money, you're sitting alone in

3:14

your office, or you're sitting in the reading

3:16

room, you go right to this sequence first,

3:19

and then you work your way through the other

3:21

pulsing sequences, this being your detector.

3:25

Oh, look at those deep fibers of the deltoids.

3:27

They are gorgeous.

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Now let's move to the short-axis projection.

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I'll keep one sagittal up, the T1, and I'll

3:38

pull down my two short-axis projections.

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Now I've got a good look at the anterior

3:45

talofibular ligament, the most important

3:47

of all the collaterals to get torn.

3:50

It shows up better when the foot is dorsiflexed.

3:55

You might say, well, why not do that in everybody?

3:58

Because it still shows up pretty

3:59

good when the foot is plantarflexed.

4:02

Not as good.

4:03

But the tendons are not in the correct

4:08

profile if you do a straight axial.

4:11

Now, look at what we did with our axial.

4:12

We didn't do a straight axial.

4:14

We planned ahead.

4:16

We were interested in the tendons.

4:18

So instead of doing a straight

4:19

axial, we did an oblique axial.

4:22

And our oblique is perpendicular to

4:24

the long axis of the peroneus tendons.

4:29

So we've overcome that potential liability

4:33

by doing our axial in an oblique orientation.

4:38

And that is the proper way to do it.

4:40

Now, could you do a straight axial?

4:42

You could.

4:43

Would that make it even

4:44

easier to see the collaterals?

4:46

It would.

4:46

But we still see them.

4:49

We still see them very well.

4:50

I showed you the deltoid, coronally.

4:52

Now I'm showing you the most commonly

4:54

torn collateral ligament of the ankle,

4:57

the anterior talofibular ligament.

4:58

And if it's not torn, chances

5:00

are nothing else is torn.

5:04

And I now have all my tendons in

5:06

profile in the short-axis projection.

5:08

I got a T1, and I also have a T2 Spineca without

5:13

fat suppression, modifier, anatomy image.

5:18

I don't really have a detector.

5:19

You might say, well, where is my water

5:22

sensitive sequence to detect tendon injury?

5:25

Well, this is an expert group of radiologists.

5:28

They don't need more than four to five sequences.

5:31

This group of radiologists goes to

5:32

the water-weighted image, and they

5:34

follow the tendons in this projection.

5:37

Is it optimal?

5:38

No, but they're experts.

5:39

So they can look inside these tendons

5:41

and see that they're absolutely,

5:43

positively nice and black and just fine.

5:46

There's our lateral tendon group.

5:48

There is our medial tendon group.

5:49

There's Tom, there's Dick, there's Harry.

5:51

Never mind who they are.

5:52

They're nice and black.

5:53

They're normal.

5:54

So here, advanced radiologists have used

5:57

different projections and different pulsing

5:59

sequences to bring the scan down into a 20,

6:02

maximum 25-minute timeframe, usually 15-minute

6:06

timeframe. By using the right sequence for the

6:09

right job, even though the projection may not be

6:12

optimal for all the structures in every plane.

6:16

So this one is dorsiflexed, but we

6:19

have angled the axials for the tendons.

6:21

We've used a very high-quality water

6:24

suppressed image as the detector completed the

6:28

examination in a very reasonable timeframe.

6:31

If you're scanning the ankle in anything more

6:33

than 30 to 35 minutes, you're scanning too long.