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Image Interpretation: DWI

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

Dr. P here and I want you to really bear down and concentrate on these subtle distinctions and changes regarding diffusion weighted imaging and MRI of the prostate. Let me make a couple of definitions for a few of you that are new to MRI or learning. When you perform a diffusion image, you're going to have pretty much a gray background prostate, looks something like this. And when you have diffusion restriction, you're going to see a bright area inside. On the other hand, when you do a calculated map of the range of diffusions using a series of B values, what looked bright on the diffusion weighted image now is going to look black on the ADC map and that is a basic understanding that you have to have before we dive into these subtle differences.

So now, let's talk about PI-RADS 2.0. A score of two, as it relates to diffusion in either area, whether it's peripheral zone or in transitional zone, was an indistinct area of hypointensity on the ADC map. So let's draw that. So I'm going to use, for the capsule, I'm going to use something blue. And for the background of the prostate, I'm going to use something that's kind of gray on the inside. Now the ADC map, remember, if there's diffusion restriction, the area is going to be dark, so we'll have something that's kind of ill defined, not black, but dark. Kind of has sort of a fuzzy character to it, but we don't say anything about the shape. Now let's go over to PI-RADS 2.1. And PI-RADS 2.1, we're going to have a linear wedge shape hypointensity on the ADC map or an area of linear wedge shape hyperintensity on the diffusion weighted image.

It's usually not going to be inordinately black on ADC or inordinately white, but I'm going to use for effect black and white. So we're going to have something that is wedge shaped for the ADC map that's dark, and we're going to have something that is wedge shaped that is white on the diffusion weighted image, usually B value of 1,400 or greater. So the major change between 2.0 and 2.1 is we're defining a specific shape for a score of two namely linear or wedge shaped and I think that's very self-explanatory. And it can either be low on ADC, or high on diffusion weighted imaging, or both. Let's move on to the next change in diffusion weighted imaging, which is score number three.

LESSON 2, TOPIC 10

Mastery Series: PI-RADS 2.1 Update

Mastery Series

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Content reviewed: December 29, 2021

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