 Let's take this 62-year-old man with a PSA of 6.4 who's had a prior negative biopsy and elucidate the mysteries of pyrads 2. The patient has type 2 form of low bar hyperplasia or BPH because it's the central zone that's enlarged pushing the urethra for it and that's discussed in another vignette. We could use our ellipsoid volume calculator and give a length, a length would be anteroposterior, times width, times height and multiply that by pi over 6 and get a volume. This volume is clearly going to be over 25 cc so we have BPH. But we are here to discuss the pyrads designation. So let's scroll up and down in the axial projection. The peripheral zone is the wider area around the outside separated from the TZ or transitional zone by the surgical capsule. So let's start with the TZ. The TZ, we'll use it synonymously with the central region of the prostate. It contains the pyrurethral region and then posterior superior we have the central zone which we're going to lump together with the TZ as part of the central zone and we're going to say, okay, in the central region of the prostate what is the major criteria for a pyrads 2? And the answer is multiple circumscribed or slightly heterogeneous nodules but none that deform the anatomic structures or architecture of the central region or TZ of the prostate. So for instance, we've got round and bright right here, very well circumscribed with a capsule. Round and dark right here, slightly irregular perhaps right here. Let's draw over this one because it's not perfectly round but it does have a sharp edge to it like that as opposed to say some charcoal smearing that wipes away this glandular nodular repetitive redundant appearance of the TZ. And that's going to be the same in the central region in the midline here and we're in the back of the prostate I believe right here. Let's see, yep, we're posterior and the same appearance is also seen here with very little peripheral zone visualized. So again, repetitive alternating areas of hyperintensity, hyperintensity, well encapsulated, nodular, not crossing any boundaries. These are the central region criteria or TZ criteria for a score of 2 which will leave us with a pyrads 2 as long as our peripheral zone is okay. So how do we check our peripheral zone? Pretty easy. We look for diffusion restriction. So rather than pull down all the diffusion weighted images, I'm just going to pull one down, the one with the highest B value. And let's look at the anatomy from apex to base and what we're looking for is something really bright that corresponds to an ugly nodular or aggressive mass with mass effect in the peripheral zone. Here's our peripheral zone. Patients had a biopsy and you can see the heterogeneity here. From that biopsy, there's some very faint hyperintensity on the diffusion weighted image but not much. It should be really bright and I'll put up a B value that's a bit lower. I'll blow it up and you can see there was something a little bit brighter there that faded away and that's exactly what benign lesions do. Pregnant lesions will get brighter as you go to higher B values. So this is a B value of around 50 and in the middle you have a B value that is 1600. So nothing getting brighter. Let's look at the ADC map also at the high B value number and we do have an area of low signal that implies decreased velocity but that is the site where our biopsy occurred. Yes, there is some hyperintensity there corresponding to those low psi on the B1600 image but it's not bright enough and there isn't a mass there. If we go back to the T2, let's go back and see the anatomic correlate of that. Right there, nothing there, right there, nothing there. So what are the things that can produce some diffusion restriction? Well, changes in viscosity like in an abscess. That's clearly not the case. Firmness, well that could be the case. Firmness or desmoplasia from scar tissue from a biopsy, hypercellularity with a paucity of cytoplasm. That is not the case here but that occurs with very solid tumors like prostate cancer like lymphoma and then necrotization, cell death, necrosis in the brain is another cause of diffusion restriction that can occur with say heroin toxicity in the brain. So this is an example of a prior biopsy site giving us a little bit of desmoplasia, a little bit of high signal on the diffusion weighted image in the peripheral zone but not enough as you saw it was a little bright on the B50 image it's about the same brightness on the B1600 image. Yes, it is picked up on the ADC map. This was the site of the prior biopsy. There's no anatomic correlate abnormality in that locus on the axial T2 weighted image. This is a Pyrad's 2.