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Let's focus on, first, the sagittal projection.

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I've got three sagittal

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images up for your perusal.

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A T1, fat-weighted, anatomy image.

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Very strong for the skeleton.

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In the middle, I have a gradient

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echo 3D slab acquisition.

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Very strong for tendons and for

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articular surfaces and capsule.

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Also great to look for loose bodies.

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The beauty of this is that it's acquired

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with uber-thin sections that we'll see

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later on, allow for angled reconstructions.

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On the far right, you've got a choice.

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You could either produce a T2 with fat

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suppression, which gives you better edge detail,

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or a proton density with fat suppression,

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which gives you better sensitivity for the

0:59

detection of inflammation and injuries.

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So if you use the T2, this is more of a

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qualifier, this is more of a detector.

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If you use the proton density, this is more of a

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detector, and this becomes more of a qualifier.

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In other words, it tells you how severe things are.

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26 00:01:18,185 --> 00:01:20,085 The T1 is your overview,

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sort of introductory sequence.

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It's like the preface to a book or a novel.

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So let's look at our preface.

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We use the sagittal projection anytime

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we want to see things that are long.

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Like, what's long?

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The achilles is long.

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So we could open the field of view up

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and see the achilles all the way from

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the myotendinous junction through the

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watershed zone, down to the footprint.

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We didn't do that here.

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We focused on the ankle.

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But we also see another very long structure.

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Look at the plantar fascia.

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We see the plantar fascia almost all

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the way to the end of the metatarsals.

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Or, the posterior flexor tendons.

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You know, if we were going to look at the

2:01

posterior tibial tendon, or the flexor hallucis,

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or the flexor digitorum,

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we get those for a very, very long distance.

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Same thing is true for the peroneae.

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Peroneus brevis and longus. Let's follow the longus.

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Then we follow the longus all

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the way into the cuboid tunnel.

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There it is.

2:16

There it is.

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Looks a little swollen.

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In fact, it's abnormal.

2:20

That's not why I'm showing it.

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I'm showing it because sagittal

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imaging confers length.

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And one thing this series of sagittal images

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does is it illustrates a very obnoxious artifact.

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And that's called the magic angle artifact.

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Sounds very non-scientific.

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But if you like science, then we'll

2:43

call it the anisotropic artifact.

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If you like science even

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more, we'll call it the 55.6 degree angled artifact.

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69 00:02:54,300 --> 00:02:59,810 So when a tendon, any tendon, is 55.6 degrees to the

2:59

main magnetic field, the B0 field, it turns gray.

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So how do you know if that gray is really a

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tear, or whether it's really an abnormality?

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Well, first it's ill-defined and smudgy.

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Second, it comes on suddenly

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where the tendon changes course.

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And then it disappears when the

3:24

tendon changes course again.

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Very linearly, right there

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at that linear interface.

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Then it comes back again.

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Then it dissipates again.

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The tendon is of normal size.

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Yeah, the tendon looks a little fat

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because the ankle's plantar flexed and

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the tendon is a bit crinkled or accordion.

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But that's because of the foot positioning.

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Very important is the fact that the surrounding

3:50

fatty soft tissues are cold-stone normal.

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That can't happen if this is

3:56

tendinopathy or tendinosis.

3:58

And finally, as the TE becomes longer, got a TE

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of 10, a TE of 6, short TEs exacerbate magic

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angle effect, but long TEs start to take it away.

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The longer the TE,

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the more magic angle disappears.

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In fact, when you get into the short axis

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view with long TEs, it'll be completely gone.

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That's how you distinguish magic angle

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effect, the anisotropic artifact,

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the 55.6-degree artifact from real tendinopathy,

4:34

tendinosis, or interstitial swelling.