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Zonal Anatomy

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Alright, let's talk about some prostate anatomy

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with these, uh, elegant series of diagrams.

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And we're going to layer on different portions

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of the, of the gland as we move forward.

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So we started out here in yellow with the urethra.

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And we'll break the urethra down later on into

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its individual sub-segments and show you the

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urogenital diaphragm, which would be here.

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So, in your mind's eye, this would be inferior

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or caudal, and this would be superior or cranial.

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So the urethra is yellow, we've got the

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expanded verumontanum and then the

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urethra continues on up into the bladder.

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We've also got these two purple structures,

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the ductus deferens, which leads to the seminal

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vesicles, and the seminal vesicles will be

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located posterior superior to the prostate gland.

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Uh, they're secreting organs so

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they contain secretory material.

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Although, after ejaculation, they will empty.

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So, some people suggest that you not do

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prostate MRI within one week after ejaculation.

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That's a lot to ask.

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Uh, however, as you get older, uh, these

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may desiccate or dry out and have

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less secretory material inside them.

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So there's a lot of variability regarding the

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signal in these glands, as we'll see later.

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And that could be a potential

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pitfall and source of confusion.

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Now let's move on to another section, the

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transitional zone, and the transitional

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zone is part of the central gland.

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So this is a little bit confusing.

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Let's really kind of drill down into

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this with a little more granularity.

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The central gland consists of the central

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zone and the transitional zone together.

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So, often, we don't make a

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distinction between the two.

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We'll often just call disease in these locations.

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Within the central gland, the central zone.

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Even though the central gland

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is composed of two components.

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The transitional zone, and one that's located

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more posterior and superior, the central zone.

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Now the central zone can be, can be pretty big.

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Varies in size, and both of these will

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increase in size with advancing age.

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And, in fact, they can get so big that

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they can push out on the remainder of the

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anatomy of the gland and, uh, in some ways

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obscure the peripheral aspect of the gland.

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Now, the peripheral aspect of the gland

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is extremely important because that's

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where 70 percent of all the cancers occur.

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They're easier to identify in this

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region, as we'll see later on.

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And the criteria for identifying disease in the

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central gland, which consists of the central

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zone and transitional zone, a bit tougher.

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Let's keep going, shall we?

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The next layer that we're going

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to put in is the peripheral zone,

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and it's kind of like an envelope.

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Now, notice that the peripheral zone

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has a very distal, apical component.

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So tumors that exist around here can have

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not only a big impact on the urethra, but

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they can also be hard to reach, hard to

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see, a little more challenging to biopsy.

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This envelope goes all the way around the right

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side and the left side of the central gland.

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It'll scoop around back of the central

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gland and you're going to get a much

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better appreciation for this when we

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look at it with cross-sectional anatomy.

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But I think this three-dimensional

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anatomic diagram does it justice.

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The next section is the

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anterior fibromuscular stroma.

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Which is fairly symmetric, it's

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thin, it's on the right and left

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side of the gland, and it's anterior.

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It has a fairly long apical extension, inferiorly.

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And because prostate carcinoma is dark,

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and the fibromuscular stroma is dark,

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this is where the diffusion-weighted image

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is really important and really shines.

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Because the cancer will diffusion restrict.

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And the anterior fibromuscular

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stroma will not restrict.

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Not only is it anterior, it's composed of fibrous

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tissue, and fibrous tissue is dark, cancer

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is dark, so this could be a little bit of a

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conundrum and a potential pitfall if you don't

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pay attention to the diffusion-weighted image.

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The fibromuscular stroma in the anterior

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portion of the gland, somewhat pancake-shaped

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and relatively symmetric from side to side.

Report

Text

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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