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Prostate Anatomy on MRI in the Sagittal Projection

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Let's take on the anatomy of the prostate

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in the sagittal projection, comparing

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it with the coronal projection and using

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the coronal projection for landmarks.

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Now you can see by my cross-reference line that

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I'm right smack dab in the middle of the prostate,

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and this little opening is the opening between the

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bladder and the prostate gland via the urethra.

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So if you can fantasize with me a little bit,

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since we don't have any fluid in the urethra,

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you can see the urethral opening right here.

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And it kind of comes down

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and then angulates forward.

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We're going to see that better

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on some other, uh, MR examples.

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Now since we're in the, the center of the

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gland, we're not far enough posterior,

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we only see the central gland portion.

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And yes, there is some hyperintensity

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on the coronal image, which just

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consists of secretory material.

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Uh, that's a good sign.

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That, that is a sign that most likely you do not

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have a prostate carcinoma in that, that locus.

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Now there is a mucinous adenocarcinoma of the

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prostate, but fortunately it's very unusual.

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In fact, it's very rare, and it will

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demonstrate bright signal intensity,

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but a much more aggressive character.

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And they're usually large

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at presentation.

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Let's take away our line for a moment.

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And I'd like to move towards the front.

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And the front of the gland is darker.

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And that's because the front of the gland

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consists of the anterior fibromuscular stroma.

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Remember the word fibro, which stands for fibrous.

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You should know that fibrous tissue on MR is dark.

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So this area is pretty dark.

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We can see an average volume with the base

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of the bladder. Here it is right here.

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It's pretty thin in this patient, and

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then posterior to that is going to be the

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central gland portion of the prostate.

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So what's in the central gland?

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The transitional zone and the central zone.

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Where do you find the central zone?

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Posterosuperiorly.

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So if I had to draw for you the position

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of the central zone, and if the central

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zone was big, where is it going to be big?

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Right here, in the posterosuperior quadrant.

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And when it gets really big, it can sometimes get

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kind of fluffy and look like a piece of broccoli.

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And it can stick up into the base of the bladder.

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Now staying right here for a moment, let's

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draw in the fibromuscular zone with a

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different color so we don't get confused.

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And then posterior to the fibromuscular

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zone, we've got the transitional zone

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which is part of the central gland.

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Let's make the transitional zone,

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oh, let's, let's make it green.

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So we've made it green and I'm coloring

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in the transitional zone for you.

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It's pretty big in this

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patient. He's 62 years old.

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But you've seen that I have left out

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an area that I haven't colored in.

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And what is that?

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That's the periurethral zone.

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And you can actually fantasize that it's there.

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This little white slit right here.

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That then curves forward, that's the urethra.

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So that gray tissue right around it that comes

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from this locus to that locus on a straight

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line and then bends, that's your urethra.

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Surrounding it is the periurethral tissue.

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So we'll give that another color.

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Oh, let's go with something, uh,

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let's go with something blue.

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So I'm gonna cover up the urethra now.

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I'm behind it.

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I'm in front of it.

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And now I'm covering it up, and

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then it makes an angle down.

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So that's your periurethral zone, which

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is located within the central gland, which

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is located within the transitional zone.

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So within the central gland, we've

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got the periurethral zone, the

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transitional zone, and the central zone.

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In front, the fibromuscular stroma.

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So you might ask, well, where,

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where's the peripheral zone?

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Well, we're right in the midline, so the

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peripheral zone is an envelope, right?

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It's around the outside, that's

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why it's called peripheral zone.

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So we've got to get more peripheral.

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If we go out to the side, to the extreme

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side, we run into the left peripheral zone.

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The left PZ.

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If we go the other way, we run into the right PZ.

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And look at how it makes a J shape,

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or a hook, as it faces anteriorly.

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It does that on both sides, but it's a

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little easier to see on the right side.

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And look at how it goes down towards the apex.

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And then curls inward.

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So these are areas that have

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to undergo careful inspection.

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Because now you're near, now you're

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near the anterior fibromuscular zone.

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And what's the signal of the fibromuscular zone?

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What's the signal of a cancer?

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Charcoal.

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Dark.

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So you could confuse the fibromuscular

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zone, anteriorly, and down low

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fibromuscular with a cancer and vice versa.

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So how are you going to tell?

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Diffusion imaging and the ADC

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map, which are going to help you.

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So let's keep going and still

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focus on the peripheral zone.

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We said the peripheral zone is an envelope.

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We see the separation of the peripheral

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zone on the sagittal from the central

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gland or peripheral gland from the

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central gland by the surgical capsule.

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We also see the anatomic capsule.

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We also see the right SV, right

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seminal vesicle, and ductus deferens.

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There it is.

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Ooh, that's pretty.

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And then on the other side,

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the left seminal vesicle.

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Ductus deferens a little harder to

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see on this side, but right there.

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That little white slit.

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Some other key structures.

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This black structure right here represents

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a combination of the volume averaged

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denom Ville a recto prostatic fascia

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and the peripheral anatomic capsule.

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In the front, we have the pre prostatic

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space of Reteus, or the puboprostatic space.

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Bladder up high, looking at thickness,

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cellulation, trabeculation,

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diverticulation, and degree of dilatation.

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We've already outlined for you the urethra.

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And just for giggles, let's go

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back to the coronal projection.

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And let's, let's go a little bit more posteriorly.

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So we can see the peripheral zone off to the side.

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And let's go to the area of the seminal vesicles.

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So that would be peripheral zone.

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Now let's work our way forward.

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And we're posterior, right?

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We're in the back, seminal vesicles.

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We're posterior.

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So what are we looking at posteriorly?

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We're looking at central gland.

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But posterosuperior, in the upper

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posterior quadrant, is the CZ.

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The central zone of the central gland.

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So where is that?

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Right here, and right here.

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Where is it sagittally?

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Right back here.

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And as you come forward, let's

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come forward a little bit.

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Still a little bit of CZ on each side.

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Let's draw it again.

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So you're gonna have CZ here, and here.

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Right in that spot, posterior superior quadrant.

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And the rest of it is gonna be transitional zone.

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As we drew in the sagittal projection.

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So let's color in the, the TZ.

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Here's some TZ.

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In the midline's gonna be your urethra.

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And so we have your urethra

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with your periurethral plexus.

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This time we'll make it, uh, purple.

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And there you have it.

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Now I could have colored in a little

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more in the transitional zone.

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So, back to the sagittal projection.

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Let's review one more time in the midline.

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Posterior superior at about

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maybe 1 o'clock, 2 o'clock.

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Central zone of the central gland.

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The rest of it, transitional

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zone of the central gland.

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The urethra comes down and forward.

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Let's see if we can spot

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it again, terrain spotting.

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Comes down and forward, not easy to see right now.

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And then, off to the side, we've got left PZ,

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off to the other side, right PZ, and you've

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seen the J hook shape of the peripheral

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zone in the sagittal projection with the

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denovillier fascia, the prostatopubic space,

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and the anterior preprostatic space of retzius.

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That's the anatomy of the sagittal projection.

Report

Editorial Note

Faculty

Stephen J Pomeranz, MD

Chief Medical Officer, ProScan Imaging. Founder, MRI Online

ProScan Imaging

John F. Feller, MD

Chief Medical Officer, HALO Diagnostics. Medical Director & Founder, Desert Medical Imaging. Chief of Radiology, American Medical Center, Shanghai, China.

HALO Diagnostics

Tags

Prostate/seminal vesicles

Neoplastic

MRI

Genitourinary (GU)

Body

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