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Case Review: PI-RADS 4/5 - Compare With Prior 3T

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Let's take a look at a 3 Tesla MRI using a

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pelvic array coil and compare it to the 1.5T

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comp vignette, which you'll

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see labeled on MRI online.

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This is an 81-year-old, and of course, as you

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get older, the incidence of low-grade cancers

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goes up, so it's really important to discriminate

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who has an aggressive cancer and who doesn't.

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And you're going to do that by size, by boundary

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crossing, by hypervascularity, But especially by the

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diffusion characteristics and the morphology of the

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lesion, whether it's crossing key boundaries or not.

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This patient had a negative biopsy,

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uh, two years prior to this study.

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And the PSA wasn't really elevated.

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It was hovering about, around 2.4.

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18 00:00:48,169 --> 00:00:50,380 But yet the clinician felt

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something on physical examination.

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And this is the perfect patient to have an MR.

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You know, the clinical exam's

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positive, the PSA, non-contributory.

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And the patient is 81 years of age.

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The patient also had a family history.

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So let's look at the axial T2-weighted image.

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And there is an area of ill-defined

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hypointensity in the PZL and PZP, or

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posterolateral and posterior aspect of the gland.

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And it's ill-defined with a

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fair amount of capsular contact.

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We lose to some degree the nice black line

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as it comes around, so we're, we're a little

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concerned about microcapsular invasion.

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We still do see the little dots of the neurovascular

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bundle in the 5 o'clock at 7 o'clock position,

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5 o'clock over here, 7 o'clock over here.

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And so we turn to our T1-weighted image.

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I'd prefer to have an axial T1, but I'm blessed

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at least with this coronal, and I'm looking at

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the neurovascular bundle right in the area of

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the tumor, so I'm scrolling backwards to that

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area of ill-defined character, and I really don't

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see any effacement of the fat on either side.

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I still see the veins and the neurovascular

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structures, that's a nerve right there.

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And so they're unencumbered by the tumor.

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So we're not going to give this patient gross invasion.

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There may be microcapsular invasion.

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Now let's turn our attention to the

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diffusion image, by the way, at 3 Tesla.

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And I'd like you to compare back and

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forth this 3 Tesla study with the 1.

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5 comp image that was a PI 5, like this

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one, to look at the Disparity and image

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quality of which there really isn't any.

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And here is your axial diffusion

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image at a higher B value.

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Here's the low B value, here's the higher B value.

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Not all that bright for this tumor.

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Let's go to another image at another locus.

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Not all that bright.

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I'm going to window it a little tighter.

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Let's go back to the one that I think

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is a little more impressive right there.

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So not as bright as I might like.

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Let's go to something with a slightly

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higher B value, a single image.

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And it's a little bit brighter.

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So, why on this image with the low B

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value and the high B value, low B value,

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high B value, why wasn't it as bright?

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Well, the main reason was that the B value

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for this particular image wasn't high enough.

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I want the B value to be 1200 or greater.

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But let's talk about, for a moment, the causes

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for false positive and false negative diffusion

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imaging because diffusion imaging is the

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major criteria for peripheral zone lesions.

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That's point one.

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Point two, causes of false positive and negative

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diffusion imaging, which we'll get to in a second.

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And point three, you have to know

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what causes diffusion restriction.

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And what does?

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Hypercellularity, cell packing, necrosis, as

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many of us see in the brain, say with heroin

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encephalopathy, infarcts, like we see in the

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brain, with destruction or breakdown of the cell

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membrane where the water gets trapped in the cell,

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hyperviscosity, as might occur with, say, a cerebral

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abscess or an epidermoid, and inciting desmoplasia,

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where the interstitium becomes very stiff and firm.

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So now let's talk about item number two of

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our three points, which is the causes for

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false positive and negative diffusion.

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One obvious cause, the spatial

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resolution just isn't good enough.

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Typically, you're not going to get great

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diffusion unless you've got a lesion that's at

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least five millimeters in cubic centimeters.

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Mucinous tumors, fortunately they're

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rare, but they don't restrict.

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But nine very cellular nodules In the TZ, and

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sometimes proliferating into the PZ, these can

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restrict, so this is a cause of a false positive.

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So in the central region, or TZ of the prostate,

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diffusion restriction is not a major criteria.

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It's a supplement.

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If it's positive, it helps with

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a suspicious morphologic lesion.

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If it's negative, it helps.

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It really doesn't help you all that much.

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But you can't use diffusion imaging on

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its own in the TZ or transitional zone.

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Abscesses.

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These are going to restrict inside

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where there's hyperviscosity.

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This is also known as the vanilla donut sign.

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Because you've got the white vanilla in the

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middle on the diffusion-weighted image and the

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solid portion of the donut around the outside.

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In a tumor, the diffusion restriction

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is more peripherally oriented.

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So the brighter signal is going to be on the

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outside, the darker signal on the diffusion.

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Not the ADC map, on the diffusion.

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The brighter signal will be on the outside,

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the darker signal will be on the inside,

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so we call this the chocolate donut sign.

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And then, as we said, any cytotoxic or

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necrotic edema can diffusion restrict, and

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this can rarely occur in the prostate gland.

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Now, some other critical causes of,

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of failure to diffusion restrict.

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Well, one is low-grade tumor, you know, Gleason 5 or 6.

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The B value, as we said, not high enough.

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Gotta have that B value 1,200 or more.

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And then another one, perhaps the reason why this

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B value did not at 1,000 show the tumor as well.

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One, the B value wasn't high enough,

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and two, there's air in the rectum.

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So air in the rectum may inhibit your ability

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to get a nice, crisp diffusion restriction.

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So let's draw these donut signs.

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So in abscess, we're gonna have lower signal intensity.

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around the outside on the DWI, say

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B1600, and on the inside where there's

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hyperviscosity, it's going to be bright.

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That's our vanilla donut sign.

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If we've got a tumor, it's going to be the opposite.

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We're going to have diffusion

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restriction on the outside.

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We're probably going to have less

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diffusion restriction on the inside.

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The so-called chocolate doughnut sign.

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And if you want to be a purist, maybe

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I should make the chocolate brown.

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Because chocolate is brown.

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So this would be the tumor chocolate doughnut sign.

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And in the middle, this would be

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the abscess vanilla doughnut sign.

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Now I want to share one other thing

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with you on this 3 Tesla study.

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So let's get out of our drawing tool for

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a minute, and let's go to the DCE MRI.

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The Dynamic Contrast-Enhanced MRI.

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So let's match it up with our Axial T2.

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Let's go right to that spot, and here's our mask.

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Now immediately, right after the contrast arrives.

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Mask, contrast arrival, boom.

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Yes, these nodules in the middle

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are enhancing, very common.

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So, you really can't use Dynamic Contrast-Enhanced MRI

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unless you have a big charcoal-like smearing mass with

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very intense enhancement and very obvious washout.

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In the periphery, we do see, as an isolated

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phenomenon, first 10 seconds, enhancement,

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In the PZL, lateral, and PZP, posterior.

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Let's keep going.

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It's getting brighter.

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It's getting brighter.

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It's getting brighter.

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And now it's getting a little less

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bright compared to the rest of the gland.

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So it's starting to wash out.

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So the curve in this one is

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looking something like this.

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Came up pretty quick.

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And it takes a little while and then

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it starts to drop off towards the end.

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Now you can quantify this with a CAD, with a color map.

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Let's see what the color map said about it.

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Let's see if it picked it up.

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And indeed it did.

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Right there.

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It also picked up these innumerable TZ

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central region of the gland areas of

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hypervascularity which are extremely common.

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So our DCE MRI said that the lesion was hypervascular,

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fire engine red, and that had a pretty decent washout.

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So, I don't rely on the hue very

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much in CAD for the prostate.

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I do rely it, rely on it in the breast, so I'm gonna

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ignore the hue or shade of red 'cause I don't think

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it's reliable And all I'm doing is looking for hyper

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vascularity in the PZ to see if that corroborates my

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tumor, but also helps me decide how vascular it is.

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For the more vascular it is earlier on,

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the more likely it is to be aggressive.

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The more intense the signal intensity on diffusion

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weighted imaging, the quicker the rise from low

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B values to high B values, the more aggressive

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the tumor, and the more hypo dense, or hypo

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intense, the signal is on the ADC parametric

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map, the more likely the tumor is aggressive.

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Let's take a look at our ADC map, and here it is.

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Not quite as black as I would have

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expected, but it is present, it is there.

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And again, the blacker it is, the more

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aggressive it's going to be on the ADC map.

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3 Tesla study, posterolateral tumor.

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This would be a PI-RADS 4/5.

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Depending upon whether we

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measure it out at less than 1.5 or

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greater than 1.5.

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228 00:11:18,599 --> 00:11:20,440 The reader said slightly greater than 1.5.ss

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230 00:11:21,000 --> 00:11:23,640 I measured it, I got slightly less than 1.5.

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232 00:11:24,030 --> 00:11:26,289 So I'd be reading it as a PI-RADS 4.

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The reader read it as a PI-RADS 5.

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This looks like a moderately aggressive lesion.

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Diffusion image, not that bright.

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ADC map, not that dark.

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Hypervascularity, some.

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In fact, moderate.

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Compare this to our 1.5

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comp vignette.

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That concludes this one.

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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