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Case Review: PI-RADS 4 – Making Use of the ADC Map

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This is a 51-year-old.

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He actually had a prostate MRI at

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another institution north of here,

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an esteemed and respected institution.

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But for some reason, they were not

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able to get a B value on the diffusion

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image of greater than 1,000.

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So the diffusion image on this

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case was non-complementary and not

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supportive of the diagnosis of cancer.

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So the patient had a rescan a week later.

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His PSA is

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8.5 nanograms per mL.

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Let's look at his axial T2.

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There is a nodule in the left,

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PZP and PZM towards the midline.

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It's bulging the capsule a little bit.

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The peripheral zone on the right is

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fairly dark but non-mass-like, very ill.

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Ill-defined.

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The one on the left is more nodular and mass-like.

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So let's turn our attention to the

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diffusion image performed at 1.5 T.

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The original study a week

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earlier was performed at

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27 00:01:02,800 --> 00:01:04,360 5 Tesla.

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And there is an area of diffusion restriction.

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It's bright.

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We could window it very tightly.

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But it's not all that impressive.

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This is a B value of 1200.

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So what I want to illustrate in

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this case, and let's go back a little

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bit to see the lower B values.

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Here's a lower B value.

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This is a B0, actually.

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And here is the B1200.

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So there is diffusion restriction in the PZM.

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But look at the ADC map.

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The ADC map is so much clearer.

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So when, when you have a situation where your

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diffusion images are either inconsequential,

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or not complementary, or not supportive,

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or there's a potential technical issue, or

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your B value isn't as high. The parametric

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images are actually the most sensitive for

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picking up areas of confluent, mass-like

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diffusion restriction, these parametric maps.

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And this one does so just beautifully.

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Now, what are some other causes

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for diffusion restriction failure?

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We've talked about them in other

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vignettes, but it's worth revisiting.

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If your spatial resolution isn't good enough,

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you're gonna, you're not gonna pick up

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any tumors that are below 5, and if

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your spatial resolution is really

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poor, you're not going to pick up any

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diffusion restriction under a centimeter.

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Remember that mucinous tumors don't

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restrict, but they're rare, but benign.

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Very hypercellular, benign abnormalities

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in the central portion of the prostate,

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in the TZ, these will diffusion restrict.

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So this is going to give you a false positive

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if you rely on diffusion in the central gland.

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But you are going to rely on diffusion

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very heavily in the peripheral gland.

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We've talked about abscesses.

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They can give you a false positive and a

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vanilla donut sign, as opposed to tumor,

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which gives you the chocolate donut sign,

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and that's discussed in another vignette.

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And then low-grade tumors, non-aggressive

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tumors, Gleason 6s and 5s, may not give

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you much diffusion restriction at all.

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And there are some technical factors like

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hyperinflation of balloon and air in the

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rectum that may affect your diffusion.

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This case illustrates just how

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valuable the ADC map can be.

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Clearly, a left PZM, PZP lesion, well under 1.

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5 centimeters in size, illustrating a

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classic PI-RADS 4 with diffusion restriction,

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major criteria, and supportive abnormality

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on the T2-weighted images of mass.

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By the way, there is absolutely no

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diffusion restriction on the right.

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Where we saw that charcoal-like, dark,

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crescent eric area in the peripheral zone.

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There it is again.

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In fact, it's white on the ADC map, whereas it

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should be black on the ADC map if it's a tumor.

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So the ADC map really is complementary

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and supportive in giving you a concrete

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non-diagnosis in the right gland and a

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positive diagnosis in the left gland.

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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