Dr. P here. What's new for prostate 2.1. The plane of the T2 weighted imaging be defined on a live case in a moment. Diffusion weighted imaging b-value uses and dynamic contrast enhanced temporal resolution should be equal to or less than 15 seconds per temporal slice. Diffusion weighted imaging and dynamic contrast enhanced interpretations including how we're going to use these in multi parametric MRI and a statement and some direction regarding by parametric MRI. Special considerations, we'll discuss include, the anterior fibromuscular stroma and central zone lesions. Which I tend to score now using transition zone criteria. We'll elaborate on this towards the end of our review. Transition zone assessments for category 2 lesions including background assessments. Let's table this one since the statement by itself is a little bit enigmatic. What I'd like to focus on right now or other changes. The sector map and especially prostate volume measurements.
Let's take a look at a live case. Let's use a live case to demonstrate prostate volume, angle of acquisition and the axial projection and maybe one or two other items. We have our axial, which is a T2 and you're going to use the T2 for volumetric measurement. Let's scroll a little bit our T2 and you'll notice on the far left that the angle of acquisition is straight across anterior to posterior or orthogonal. If I draw a line, it looks like this. On the other hand you are allowed to, and I don't mind, if you angle perpendicular to the long axis of the prostate. If we say this is the long axis using the bladder opening, then our axial acquisition could be absolutely perpendicular to this and that's fine. That's another way that you can then use your axial to make your measurement. You can make your measurement off the straight orthogonal or the angled axial.
Next, let's talk about volume. In order to measure the prostate volume, which is length, times width, times height, got to have a T2 weighted image. Again, I don't mind if it's orthogonal or angled. For my axial, I want to be at the level where the prostate is most plump. That is right about here at the mid level. By horizontal dimension, quite easy from capsule to capsule. I'm going to mark it with my yellow pen, right here, including the peripheral zone. My anteroposterior measurement, also quite easy for the fibromuscular stroma all the way back to the posterior midline aspect of the peripheral zone. The one that's most challenging is the longitudinal measurement. Now this patient really doesn't have much BPH or benign prostatic hypertrophy. Here's what I like to do.
There's this little dippity do where we have the urine entering the proximal aspect of the urethra. I'm going to draw a line right here and then I'm going to take a longitudinal measurement from that line and bring it all the way down. Most people will stop right here. That's incorrect. You want to go all the way down into the peripheral zone. Now you want your sagittal measurement to be in the mid line. In the mid line you may catch a little bit of the peripheral zone or all of the peripheral zone, but you've got to have a little bit of peripheral zone there to include it in the longitudinal measurement. The peripheral zone typically is going to be more hyperintense than the rest of the prostate. Here's your longitudinal measurement. What if the patient had benign prostatic hypertrophy? What if there was a little more prostate tissue up like that?
Then we would take our yellow pen once again, and we measure from the top of that upward convexity and then we draw a line straight down all the way to the inferior aspect of the peripheral zone. Sorry, I used an orange line instead of a yellow line, but I think you get the picture. Length times and poster dimension, times width, times PI, divided by six gives you your ellipsoid measurement for the prostate and thus prostate volume.
You've also seen that we can acquire orthogonally or obliquely. One last caveat, there is a new sector map designation called PZPM and we're going to spend a little bit of time, a few minutes talking about that later on.
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Content reviewed: December 29, 2021