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Image Interpretation: DWI Score 2 vs. 3

4 min.
Pomeranz, Stephen
Stephen J Pomeranz, MD
Chief Medical Officer, ProScan Imaging. Founder, MRI Online
CME Eligible

Dr. P here talking about diffusion weighted imaging PI-RADS 2.0 versus PI-RADS 2.1. Now some of you may be a little bit confused here because these scores that we see on the left, you see score one, two, three, four and five, two and three are in red. These are some of the clarifications, modifications, and changes that we've experienced are used to eventually come up with a final PI-RAD scores. So these are sub scores as they relate to diffusion only and they'll combine with some other scores like the T2 weighted image and maybe even DCE MRI to give you a final PI-RADS designation. Hopefully this clarifies what the score's purpose is for you.

So we're diving into just a fusion weighted MRI and now we're focusing on this one right here, score number three originally. And I'm going to make my prostate capsule nice and blue and pretty big. We've got BPH and then originally, 2.0 we had a focal mild to moderate hypointense area on the ADC map, so it wasn't black, it was kind of intermediate gray to dark gray. It if was black, that would mean that it was really diffusion restricted. So it has some diffusion restriction but not inordinately extreme.

And on the other hand, we're going to have on the diffusion weighted image, it's going to be light, but not as light as say a bright white light bulb, which would mean again, there would be extreme diffusion restriction. So these are kind of modicums of change in the diffusivity of the tissue in question, but nowhere does it specify anything about shape. Now we go to 2.1. So I'm going to use my eraser to get rid of these, but I'm going to keep my BPH in place in my prostate capsule. This time we have focal discrete lesions.

Now I drew them as nodules before. I probably should have drawn them as any shape. So if we go back to PI-RADS 2.0 right here, the shape could have been something that is like this. It could have been round, it could have been somewhat irregular. So we spoke nothing about shape, but now we're going to say that our abnormality is discrete, very different then the background tissue, and having a somewhat nodular kind of appearance.

It doesn't really specify anything other than focality and that it's different from the background. But this time we have hypointensity on the ADC map, hyperintensity the high B value of 1400 or greater diffusion weighted MRI, and it may be markedly hypointense on the ADC map, or it may be markedly hyperintense on the diffusion weighted image. Let's see if I get my white working here, I can, but not both. So one or the other.

So some focality where you can define the edges of it. Whereas our lesion in PI-RADS 2.0, could have been somewhat ill defined, not very sharp edged, whatever shape we have in PI-RADS 2.1, is going to be focal, different then the background. You can see where it starts, you can see where it stops. It's going to be dark on ADC, it's going to be really white on DWI, but not both. So that's a change in score number three, from PI-RADS 2.0 to PI-RADS 2.1.

LESSON 2, TOPIC 11

Mastery Series: PI-RADS 2.1 Update

Mastery Series

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Content reviewed: December 29, 2021

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