0:00

Focusing on the sagittal projection for

0:02

the ankle, T1 on the left, gradient echo

0:05

in the middle, 3D gradient echo, and on

0:07

the far right, T2 with fat suppression.

0:12

Now, you've got to have a practical

0:14

approach to ankle imaging.

0:15

So you can't have all these

0:17

sequences plus more in every plane.

0:20

You've got to choose, and

0:21

you've got to choose wisely.

0:23

So here I have three sequences, which

0:25

I normally wouldn't get in every ankle.

0:28

But if I am interested in a tendon, or a

0:31

structure that's very long, like the plantar

0:33

fascia, then I might focus all my effort, all

0:37

my energy, into a specific plane of acquisition.

0:42

For instance, in the Achilles, I'm focusing

0:45

most of my energy and my pulsing sequences in

0:49

the sagittal, and I will get three different

0:53

sequences in that plane, and maybe one in

0:55

the other two planes, for a maximum of five.

0:59

If you're doing more than five planes of

1:01

acquisition in an ankle, then you're either

1:06

insecure, you're doing too many pulsing

1:08

sequences, and you're taking up too much time.

1:11

Now I'm talking in practical, everyday radiology.

1:16

Not talking research.

1:18

Another decision that you have to

1:20

make in the sagittal projection is

1:22

how much do you really want to see?

1:24

For instance, if the Achilles

1:26

was my interest, it's not in this

1:28

case, then I need to see up higher.

1:32

I should have moved my coil up higher

1:34

to see the myotendinous junction and

1:36

the watershed zone of the Achilles.

1:38

Peace.

1:39

I didn't because I'm interested

1:40

in the ankle, not the Achilles.

1:42

If I was interested in the

1:43

plantar fascia, terrific.

1:45

Let's scroll.

1:46

I've got the entire plantar fascia on here.

1:48

It's gorgeous.

1:49

There it is.

1:50

There it is.

1:51

There it is.

1:52

If I was interested in the medial flexor

1:55

group, the posterior tibial tendon, the

1:57

flexor hallucis, and the digitorum, fantastic.

2:01

Then the field of view is great.

2:03

But if you said to me, you know, ankle sprain,

2:06

rule out osteochondral defect of the talar dome,

2:09

I'm really interested in the talar dome and

2:13

the collaterals that surround the ankle joint.

2:15

I don't need all this midfoot anatomy.

2:19

I need spatial detail.

2:21

I'm bringing the field of view down to

2:23

something on the order of 12 centimeters.

2:27

This is more on the order of 16 to 18 centimeters.

2:30

So, you control the horizontal, you control

2:34

the vertical, you control the spatial detail.

2:38

What about slice thickness?

2:41

Slice thickness should be in the foot.

2:44

I like four and under.

2:47

Here you can see I've done

2:48

three millimeters for the T1.

2:51

Seven millimeters for the 3D, and

2:57

three millimeters for the PD spur.

2:59

And for each of these, there's

3:01

a little bit of overlap.

3:02

In fact, for this one, there's 50 percent overlap.

3:06

There's a reason for this.

3:08

I'm going to reconstruct this to look

3:10

at the tendons in greater detail.

3:14

What about the matrix?

3:17

Well, there you've got a decision

3:19

to make based on your scanner.

3:22

Lower field systems, somewhere

3:25

around 192 by 256 to 256 squared.

3:29

Higher field systems, you can go up pretty easily

3:32

to 512 by 512, which has been done here on this 1.

3:39

5 Tesla scanner.

3:42

So, that kind of gives you a rough

3:44

overview of the sagittal projection.

3:47

Its real strength is when you want to see

3:49

length, but you have to know where that length is.

3:52

If you're interested in length down here, then you

3:54

want to have your field of view extend this way.

3:58

If you're interested in length up here,

3:59

for instance, an extensor tendon tear up

4:01

higher, or an Achilles tear, then you've

4:04

got to center up more proximally.

4:07

And that is part of your job, part of

4:10

training your technologist, and hopefully

4:12

you don't have to go in there for every case.

4:14

Your technologist is educated enough

4:16

to make that judgment for you.

4:18

Let's move on, shall we?