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Hello and welcome to Noon Conferences hosted by MRI Online.

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In response to the changes happening around the world

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right now and the shutting down of in-person events,

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5 00:00:09,030 --> 00:00:10,830 we have decided to provide free daily noon

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conferences to all radiologists worldwide.

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Today we're joined by Dr. Daniel Margolis.

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He as director of Prostate MRI, he oversees all

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clinical aspects of prostate MR as they relate

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to detection, characterization, and prostate

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cancer for targeted biopsy, surgery, and radiation

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planning, treatment follow-up, and active surveillance.

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Reminder that there will be time at the

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end of this hour for a Q&A session.

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Please use the Q&A feature to ask all of your questions,

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and we'll get to as many as we can before our time is up.

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That being said, thank you so much

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for joining us today, Dr. Margolis.

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I'll let you take it from here.

0:41

Yes, thank you, uh, for your attention.

0:44

Um,

0:48

go back to the title slide.

0:50

Um, so I'll be talking today about the use

0:53

of prostate MRI for post-treatment imaging.

0:58

I should mention, uh, I am a former consultant for

1:01

Blue Earth Diagnostics, now a subsidiary of Bracco.

1:05

Uh, and Cornell, uh, receives a, uh,

1:08

research, uh, agreement from Siemens.

1:11

So we're going to talk first about PI-RADS version 2.1, and

1:16

then I'll talk about the use of MRI for evaluation of

1:20

recurrent disease after radiation therapy and surgery.

1:25

And I'll, uh, conclude by discussing the use of MRI

1:29

for focal therapy, uh, and especially follow-up.

1:34

Um, so as you, uh, all probably know, prostate MRI as

1:39

currently used is multiparametric, and this includes

1:43

T2-weighted imaging, dynamic contrast-enhanced imaging,

1:48

diffusion-weighted imaging, and spectroscopic imaging.

1:53

PI-RADS version 2.1 is designed to assess

1:59

primary significant cancer, PI-RADS being

2:03

Prostate Imaging Reporting and Data System.

2:07

More than 20 publications have proven PI-RADS

2:11

version 2.1 as the standard for prostate MRI.

2:16

Uh, it was published in European

2:18

Urology with an update last year.

2:22

And, uh, there, I'd like to point out that it

2:25

describes the normal appearance assessment and

2:29

reporting and staging in addition to the technique,

2:33

and we'll discuss this, uh, in a little bit of detail.

2:38

It's also available on the American

2:40

College of Radiology website.

2:43

Uh, there's a link to the PI-RADS document, uh, and I

2:47

should also point out there's a link to both a text

2:51

and a PDF file for report formatting.

2:57

Uh, I should also point out there was a related

3:01

article in the New England Journal of Medicine,

3:05

uh, last year describing the use of MRI compared

3:10

with the prior standard of systematic biopsy only.

3:15

Cancer diagnosis.

3:16

And I want to point out one of the

3:18

authors is Valeria Panebianco from Rome.

3:21

And, uh, I'll talk a little bit more about that later.

3:26

Um, and what we find is that, uh, although we find

3:31

the same amount of cancer, so about half of previously

3:37

biopsy-naïve men, uh, were found to have cancer.

3:42

Using the MRI biopsy technique, um, we

3:46

were able to avoid biopsies in, uh, almost,

3:50

uh, uh, a third of the men that presented.

3:55

Uh, and we find more significant cancer and significantly

4:01

less, uh, insignificant cancer and benign findings

4:05

in these men with far fewer biopsies overall.

4:09

And so this multicenter study, uh, established the

4:13

use of prostate MRI as the, uh, primary, uh, step

4:19

in the determination of who should go to biopsy.

4:24

Uh, and, uh, recently the RADS committee has

4:29

published the multiparametric MRI and MRI-directed

4:33

biopsy pathway, which provides a flow chart

4:37

for determining who should get a biopsy, uh, as well as the

4:43

breakdown of what we would expect to see in men that do and

4:49

do not get biopsies based on the, uh, PRECISION study, as

4:54

well as other multicenter, um, level one evidence studies.

5:01

But there are some aspects.

5:04

Not addressed by PI-RADS.

5:06

It does not address the use of PET or

5:09

prostate cancer, nor the use of ultrasound.

5:12

It does not specifically recommend treatment

5:16

planning, and as we'll see today, it does not provide

5:21

recommendations for reporting after treatment.

5:25

So it is for primary untreated prostate

5:29

cancer detection and characterization.

5:35

To go over the components of prostate MRI, it's

5:39

useful to compare how they function in the primary

5:43

detection setting, uh, as well as, uh, after treatment.

5:48

So, as you probably know, T2-weighted images are primarily

5:52

used for evaluation of the transition zone and for staging.

5:58

While diffusion-weighted imaging with the apparent diffusion

6:00

coefficient map are the most specific, uh, pulse sequences

6:06

and are used for characterization of the peripheral zone, and

6:11

dynamic contrast-enhanced perfusion imaging, uh, has been

6:15

found to be the most sensitive for the detection of cancer.

6:20

Uh, and I'll go into a little more detail on

6:22

uh, DCE in a moment for recurrent disease.

6:28

T2-weighted images are very difficult to

6:30

interpret because treatment effects decrease both

6:34

sensitivity and specificity on T2-weighted imaging.

6:37

So they play a much smaller role.

6:41

Diffusion-weighted imaging and the apparent diffusion

6:43

coefficient map are both useful, but the diffusion-weighted

6:48

images become far more useful than the, uh, uh, ADC map.

6:57

And dynamic contrast-enhanced perfusion

7:00

imaging becomes the mainstay of reevaluation.

7:06

So considering dynamic contrast enhancement,

7:10

um, we know that DCE is the best estimate

7:15

to evaluate the size of tumor, tumor.

7:18

Uh, this was shown by the group, uh, out of

7:21

University of Chicago, led by Ida and Odo.

7:24

But it still underestimates the total size of tumor

7:28

compared with, uh, surgical specimen histopathology.

7:33

It's important to acquire a dynamic acquisition, uh,

7:39

because the early enhancement images are the most useful

7:45

for identifying, uh, both primary and recurrent cancer.

7:50

And you can see here in this example.

7:52

This early enhancement image, uh, image identifies

7:55

a tumor that's actually in the transition zone,

7:58

where this would not be used to evaluate the

8:00

suspicion, um, but that even eight seconds later

8:05

we begin to lose the conspicuity of the lesion.

8:10

Whereas with pharmacokinetic maps,

8:12

such as Ktrans, it remains conspicuous.

8:15

So the main utility of pharmacokinetic maps is that it's,

8:19

uh, an easy way to find that early enhancement time point.

8:24

Um, the quantitative components may be useful in evaluating

8:29

treatment, um, but are generally still used qualitatively.

8:35

High b-value DWI is also crucial.

8:38

So here's a patient at two different time points

8:41

where we can, again, see that in the transition zone.

8:43

Uh, there's this hypo-, uh, intense lesion on the ADC,

8:49

uh, with the b equals 800 seconds per millimeter squared.

8:53

We don't really see any abnormal signal.

8:56

Now the fact that it's not dark, um, but is dark

9:00

on the ADC should suggest that this is abnormal.

9:03

With both the natively acquired b 1400

9:07

image and also a calculated b 1400 image,

9:10

we can see that there's very subtle but

9:13

real hyperintensity, uh, of this lesion.

9:18

Uh, and as we will see, this becomes crucial

9:21

for the evaluation of patients after treatment.

9:26

So how do we use PI-RADS?

9:29

Uh, it's based on a flow chart.

9:31

This is the flow chart that I use.

9:33

The first thing to determine is, is the lesion

9:36

in the peripheral zone or the transition zone.

9:39

If it's in the peripheral zone, you primarily

9:42

look at the diffusion-weighted imaging, uh, and

9:45

categories 1, 2, 4, and 5, uh, are basically

9:49

the same as the final overall PI-RADS category.

9:53

For category three lesions, we can upgrade to

9:57

category four if there is focal early enhancement.

10:02

For transition zone lesions, it's a little more complicated.

10:07

We look at the T2-weighted images to get the T2-weighted

10:11

imaging category, but if it's category two,

10:16

we can bump that up to an overall category three.

10:19

If the diffusion is category four or five, and for

10:23

category three, we can bump it up to overall category

10:27

four if the diffusion is also category five.

10:32

And so thinking about how to categorize

10:36

lesions, um, for the peripheral zone,

10:39

and similarly for the transition zone, if you see

10:42

something that's bright on the DWI, um, and dark on

10:47

the ADC, um, then that's at least a category three.

10:53

The exception is if it's a linear or wedge-shaped lesion.

10:58

So this is sort of, um, wedge-shaped,

11:01

and linear here.

11:02

And I'll show you another example.

11:05

Um, that would be category two if it's the

11:09

brightest thing on the DWI and the darkest thing

11:12

on the ADC, that's at least category four.

11:16

And if it's the brightest and darkest thing and

11:19

it's either invasive on T2-weighted imaging or at least

11:23

1.5 centimeters, then that's overall category five.

11:27

And I'll show you some examples in just a moment.

11:30

But first, what do we mean by wedge shape?

11:33

Well, the orientation should be radial, so

11:36

pointed toward the center of the prostate.

11:40

Um, and as you can see, there's this, uh,

11:43

radial linear structure on T2-weighted imaging.

11:46

Um, on DCE,

11:48

it's kind of patchy, it's hard to identify, but on both the

11:52

high b-value DWI and on the ADC, we see that these lesions

11:58

are radial, linear, or wedge-shaped,

12:01

and are therefore category two.

12:04

For the assessment of T2-weighted imaging,

12:07

um, it's important to determine if transition zone lesions

12:11

are encapsulated, meaning that there is a dark rim all

12:15

the way around, or if they're just circumscribed, meaning

12:19

that they have a sharp zone of transition, but not an

12:22

actual capsule, or if they're partially encapsulated.

12:27

Um, if they're, uh, irregular or they have

12:31

a blurred margin, that's category four.

12:35

And if you can't tell what the margin really

12:39

is because of artifacts such as motion or

12:44

because of adjacent prostatic hyperplasia.

12:47

Then that's category three.

12:49

And then similar to DWI, if it's at least 1.5

12:53

centimeters or there's, uh, invasive, uh, behavior,

12:57

then we would upgrade a category four to category five.

13:01

Um, and here's a cartoon that shows how we

13:04

think about nodules in the transition zone.

13:08

Uh, if it has this black line all the way around,

13:11

that's category one, and it stays category one overall.

13:15

If it's, uh, simply circumscribed, or if

13:19

there's a capsule that does not go all the

13:21

way around, then we have to consider the DWI.

13:26

And if it's the brightest thing on the DWI and the

13:29

darkest thing on the ADC, meaning category four

13:32

or five, then it would be overall category three.

13:38

And so here's some examples.

13:40

Um, so this is circumscribed.

13:43

We can see that there's.

13:44

A sharp margin, but we don't really see, maybe, yeah,

13:49

we don't really see a dark rim all the way around, but

13:53

it is the darkest thing on the ADC and the brightest

13:56

thing on the DWI, and therefore, although it's T2

14:01

category two circumscribed, it's overall category three.

14:07

Here's another example.

14:09

Where we can see that there's this lesion

14:13

in the transition zone, but we can make

14:16

out, uh, a, uh, rim all the way around.

14:21

Um, and it's large, but again, that only applies

14:26

to lesions that are category four or five.

14:29

Now, I also want to point out, you can see there's a bone

14:31

lesion, and we acquire a fat-sat T2 along with our.

14:37

Uh, dedicated prostate imaging.

14:40

This is not part of PI-RADS recommendation, uh, but is

14:43

something you can do to evaluate the rest of the pelvis.

14:47

And as you can see, there's no T2 hyperintensity.

14:50

So while this may have been a metastasis, it's dead.

14:53

It has no, uh, edema, uh, and therefore is likely benign.

14:58

Uh, but getting back to, uh, this

15:00

lesion, it's, um, uh, homogeneous.

15:05

And maybe you can see part of a capsule here, but it's

15:09

not completely encapsulated; therefore, it's category two.

15:13

But on the, um, ADC and the DWI, it's the darkest thing,

15:18

and the brightest thing.

15:20

Now, the size does come into play for DWI.

15:24

This is category five because of its size

15:27

on DWI, but it's overall category three.

15:31

On biopsy,

15:32

this was large-volume Gleason three plus three cancer.

15:36

Um, now here's another example of a partially

15:40

encapsulated lesion, uh, in the transition

15:43

zone, which is again, uh, DWI category four.

15:50

Um, but in this case,

15:51

it was a false positive,

15:53

uh, PI-RADS three.

15:54

So again, partially encapsulated, so category

15:58

two, but markedly, uh, hyperintense, DWI

16:02

and hyperintense ADC, category four.

16:05

Um, we didn't see any enhancement, um, but

16:08

we were able to target this lesion with

16:10

ultrasound, uh, and it was negative on biopsy.

16:14

So, uh, sometimes, uh, a category

16:17

three will be, uh, negative.

16:20

Then here's a T2-weighted

16:22

image below the level of lesion.

16:24

You can see this is the anterior

16:25

fibromuscular stroma, which is normal.

16:28

But then, uh, in the left aspect of the transition

16:32

zone, um, we see a lesion where, in this case,

16:36

it's hard to evaluate exactly where the margin is

16:40

because the transition zone is so heterogeneous.

16:44

Uh, and so we called this obscured

16:46

margins, meaning T2, category three.

16:49

Now you can see it's not bright on the DWI.

16:53

So the DWI is also category three.

16:56

If this were T2, category two, it would stay T2,

17:00

category two, but it's already category three.

17:03

And so we don't really have to care about the DWI because

17:07

it's not category five, and it's overall category three.

17:12

Uh, and two more, uh, follow-up, uh, examples.

17:16

This is an example of a central zone lesion.

17:19

So here's some axial T2-weighted images with some motion.

17:22

You can see the rectum, it's very distended, but on the

17:25

coronal we can see this lesion here in the medial base,

17:30

um, and that it's conspicuous on the ADC and the DWI.

17:34

Um, and so we described this as.

17:38

You can see that it has an irregular margin.

17:40

And so that's T2, category four.

17:43

Um, and it's markedly hyperintense on the ADC,

17:46

but only mildly hyperintense on the DWI.

17:49

It does have focal early enhancement, um, but because

17:52

it's T2, category four, and in the central zone where

17:56

we use the transition zone descriptors, it's overall

17:59

category four, and one last, uh, peripheral zone lesion.

18:05

This is way at the bottom of the apex.

18:08

So at the apex, the transition zone ends right about

18:12

here, and we're down here on this coronal image.

18:15

And so what you see in the anterior, uh, peripheral

18:19

zone, uh, because there's no transition zone this far

18:23

down in the prostate is it's the darkest thing on the ADC.

18:27

It's the brightest thing on the DWI.

18:29

Um, and so, uh, this is overall.

18:34

Oh, sorry.

18:35

It's only moderately hypointense.

18:37

Sorry.

18:37

So this is actually outside of the prostate.

18:40

This lesion here, uh, corresponds to

18:44

the DWI, but it's the same as the rest of the

18:47

urethra and some other areas in the, uh, prostate.

18:51

So it's not markedly hypointense.

18:53

It's not the darkest thing, and you can

18:55

see that the enhancement isn't focal.

18:58

So this was overall category three.

19:00

However, the PSA density was above 0.15.

19:04

And so a category three lesion, which is

19:07

itself equivocal suspicion, is modulated

19:11

by the clinical suspicion, which is high.

19:13

And that's concordant with finding

19:16

high-grade, uh, cancer on biopsy.

19:21

And that brings us to, what about MRI for

19:24

recurrence after radiation and surgery?

19:28

So imaging the prostate after treatment, uh, includes

19:33

the cases of radiation therapy, uh, focal therapy,

19:38

but also patients on hormonal therapy will also show

19:43

a decrease in overall T2 signal and an increase,

19:47

as well as a decrease in the overall ADC.

19:56

Uh, non-affected prostate or non-cancerous

19:59

prostate see a decrease in the DWI and DCE.

20:05

Um, what this means is the whole prostate is kind

20:08

of abnormal, and this decreases our specificity.

20:12

Um, the main things we look for are

20:15

asymmetry, an abnormality on the high B

20:19

value DWI, and a focal early enhancement.

20:25

We can't really use our PI-RADS suspicion

20:29

categories in the post-treatment state.

20:33

Um, we also can see focal atrophy in areas of focal therapy.

20:38

This can include an area of boost from

20:42

radiation therapy, as well as the focal

20:44

therapy that I'll describe a little later on.

20:47

Um, when you compare these, uh, features with

20:50

what we expect to see after prostatectomy.

20:54

What we look for is very similar: an enhancing

20:57

nodule with high signal on the high B-value DWI.

21:03

We can also consider using MRI for treatment response.

21:08

Uh, this is primarily used in radiation

21:11

therapy and focal therapy, although even

21:14

then, uh, this remains somewhat controversial.

21:18

We can see changes on imaging before we would

21:23

uh, detect a change in the PSA, and so you may have

21:28

referrers that recommend MRI even before the patient

21:33

reaches the PSA cutoff for, uh, biochemical failure.

21:39

The ADC can quantify response, but remember that the,

21:43

uh, quantitative ADC depends on the B-values used.

21:48

And so if you have the same scanner platform.

21:52

You're using the same protocol, you

21:54

can compare ADCs across scanners.

21:57

But otherwise, if you use different ADC or, uh,

22:00

different B values for the, uh, computation of the

22:03

ADC, or if you're using different scanner platforms, you

22:07

may not be able to compare the ADC. Dynamic contrast

22:11

enhancement may be the best indicator of failure.

22:14

Um, and you can quantify the,

22:18

uh, pharmacokinetic parameters.

22:21

However, uh, what this means may be, uh,

22:25

complex, and T2-weighted imaging can be difficult

22:29

to interpret in the post-treatment setting.

22:33

So, MRI, uh, can predict response, uh, and this has been

22:38

shown ever since, uh, 2009, where, uh, dynamic contrast

22:44

enhancement was, uh, shown to, uh, correlate with response.

22:50

Others have looked at ADC and either

22:52

radios or texture feature characteristics.

22:56

However, how these should be used, uh, long-term and

23:01

especially for modulating treatment, is not well established.

23:05

Uh, but as I mentioned, a change in the

23:07

MRI will precede a change in the PSA.

23:13

Um, and I'd like to point out this, uh, example case.

23:18

HDR brachytherapy.

23:19

So high-dose-rate brachytherapy.

23:22

This is different than low-dose-rate brachytherapy,

23:25

where seeds are left in the prostate, and HDR

23:29

brachytherapy catheters are placed into the

23:31

prostate, and very highly radioactive seeds are,

23:36

uh, positioned along the course of the catheters to

23:39

deliver a defined amount of radiation to the prostate.

23:43

After which the catheters and the seeds are

23:46

removed, so nothing is left in the prostate.

23:49

And you can see on the initial images, uh,

23:52

these arrows are pointing out two areas where

23:54

we see restricted, uh, diffusion on the ADC

23:57

map and, importantly, uh, focal, uh, enhancement.

24:00

Uh, and they're, uh, sort of obscured, uh, hypointense

24:04

on T2-weighted imaging. Uh, on the follow-up imaging.

24:08

The T2-weighted images are very hard

24:10

to interpret, as is the ADC map.

24:13

What we see is that the dynamic contrast enhancement

24:17

has normalized, and this is, uh, reassuring that

24:23

the patient has adequately responded to treatment.

24:28

You'll also notice that, uh, the green arrows

24:31

identified the catheter defects on the T2-weighted imaging.

24:35

Um, and I'll show you another example of, uh, an

24:39

artifact, uh, from radiation therapy later on.

24:42

So my, uh, colleague, Valeria Panebianco in Rome, um,

24:47

is working on a proposal for post-treatment assessment.

24:52

This is not yet published, but I want you to

24:54

keep an eye out for an article, uh, from Dr. Panebianco,

24:59

uh, that should be released, uh, in the

25:02

next few months that will provide a framework

25:07

similar to PI-RADS, but in the post-treatment state.

25:11

And while we have descriptors for T2-weighted

25:14

imaging, you'll see that it's dynamic contrast that is

25:18

most important, modulated by diffusion-weighted imaging.

25:23

Uh, it's also important that we're looking

25:26

for, uh, fairly simple descriptors.

25:29

So if it's, um, high on the DWI or low on the ADC,

25:35

but not both, this is sort of, uh, equivocal suspicion.

25:40

It's more suspicious if it's abnormal on both.

25:43

But we don't really have a background, so it's hard

25:46

to say, is it markedly hyperintense and hyperintense,

25:50

or mildly, because the whole prostate is abnormal.

25:53

So basically you're looking to see, is it,

25:56

uh, distinctly bright on the DWI and darker on

26:01

the ADC compared to the rest of the prostate.

26:04

Similarly, we want to look to see if there is a focal

26:07

early enhancing nodule or a focal late-enhancing nodule.

26:11

The late-enhancing nodule being equivocal suspicion.

26:15

And, uh, scar will be different if there

26:19

is a prostate in situ or if it's taken out.

26:22

So in the prostate, a scar would be sort of a linear

26:26

hypointense signal, whereas when the prostate's removed,

26:29

it would be diffuse thickening at the surgical bed.

26:33

Um.

26:34

It's also important to point out you increase

26:37

your level of suspicion if the abnormality is on

26:41

the same side where you initially had a tumor.

26:45

And this, uh, refers to both the prostate, the prostate bed,

26:51

and the seminal vesicles, which are important to assess,

26:55

uh, after treatment, including the seminal vesicle bed.

26:58

So if there was a tumor in the

27:00

prostate and the prostate is removed.

27:03

And at the site of the seminal vesicle

27:06

bed, on that same side, you see an early

27:10

enhancing nodule that restricts diffusion.

27:12

That is very suspicious.

27:15

So here's an example that I showed you earlier, where

27:18

again, we see a lot of heterogeneity on T2-weighted imaging.

27:22

This is a site of the original tumor, and you

27:24

can see that it's maybe a little more mass-like,

27:27

but it's hard to tell that this is different

27:28

than that, or that on the ADC map, it's dark.

27:33

Probably more mass-like, but you can see that

27:36

there's a lot of patchy low signal on the ADC.

27:39

However, on DWI, it shows focal, uh, high signal

27:44

intensity and, uh, focal early enhancement.

27:49

So since this is on the same side as the original tumor,

27:52

at the, at the same site, uh, and it's abnormal on

27:56

DWI, ADC, and DCE, this would be very highly suspicious.

28:03

And compare this with, uh, recurrence after prostatectomy.

28:08

So this is the bladder lumen, and this

28:11

is the vesicourethral anastomosis.

28:13

So this is the bottom of the bladder, just above the

28:17

urethra, uh, and basically where the prostate used to be.

28:22

And you can see this is the, uh, uniform low signal.

28:25

This would be, uh, like either

28:27

normal bladder mucosa or scar.

28:31

But here we see this sort of intermediate signal

28:34

intensity nodule is moderately, not markedly, hypointense.

28:39

Uh, but again, it's got very low signal on the ADC,

28:43

and importantly, high signal on the high b-value DWI.

28:48

And, um, it's, uh, focal early enhancement

28:52

on dynamic contrast-enhanced imaging.

28:55

Um, and so again, this is very suspicious.

28:58

Recurrence after prostatectomy.

29:00

Uh, and here's an example of fiducial markers.

29:03

These are sometimes put in, um, to guide

29:06

radiation therapy, uh, using CT, but they are

29:10

not placed specifically at the site of a tumor.

29:13

So if you see these, um, all that tells you is that

29:17

the patient's had external beam radiation therapy.

29:19

Uh, they don't really tell you where the tumor was.

29:23

So here's a case example.

29:25

This is a patient that actually had, um,

29:28

androgen deprivation therapy and intensity-

29:30

modulated radiation therapy 10 years ago.

29:34

Um, and here on the, uh, same side where we saw

29:37

the original tumor, there's this large mass.

29:40

It's got early enhancement, it's got low signal

29:43

on the ADC and high signal on the DWI.

29:46

Um, and so, uh, and, and this is the seminal vesicle bed.

29:51

So this is invading the seminal vesicle.

29:53

It's a recurrent, uh, or residual

29:56

tumor that's, uh, stage T3B.

29:58

Um, and the stage doesn't really matter at this point.

30:01

So this patient had repeat IMRT.

30:04

Now note that on the side opposite where we saw the

30:08

recurrence or the residual tumor, um, we see a new

30:13

lesion with low signal on the ADC, high signal on the DWI,

30:19

and sort of, uh, subtle but focal early enhancement, um,

30:24

because you have a match on the DWI, ADC, and DCE, even

30:30

though it's at a different site than the original tumor.

30:34

Um, this suggests, uh, that this is

30:38

a highly suspicious lesion, uh,

30:42

and the other thing to keep in mind is we can

30:46

identify lymph nodes on the DWI as well.

30:49

So this patient had these newly enlarged lymph nodes.

30:52

Um, the DWI is very useful for identifying where they are,

30:56

but it doesn't really tell you if they're involved or not.

30:59

Uh, and neither does DCE. DCE also points

31:02

out all the lymph nodes, normal and otherwise.

31:05

Um, and so we still use the size and

31:07

shape descriptors like we would on CT

31:10

to determine the level of lymph node suspicion.

31:14

And the patient had, um, additional

31:17

stereotactic body radiation therapy.

31:21

And what we see is that there is normalization on T2

31:25

imaging, DWI, maybe a little residual high signal here.

31:30

There's no early enhancement, um, no, uh, residual

31:34

uh,

31:35

ADC abnormality that we can tell.

31:39

There's still this big lymph node here.

31:41

Um, but at least, uh, the patient responded to SBRT.

31:45

Uh, now, interestingly, uh, 16 years after the first

31:49

treatment, so, uh, uh, five years after the re-treatment,

31:53

we see these lesions that have abnormal enhancement

31:56

with necrotic centers and very restricted diffusion.

32:00

These are neuroendocrine-

32:02

differentiated, um, bladder cancers.

32:05

And, um, so this is a secondary cancer.

32:08

Um, and the important thing to keep in

32:10

mind is, um, other cancers may have a very

32:13

similar appearance to prostate cancer.

32:15

Now, in the prostate, uh, something that looks abnormal is

32:19

overwhelmingly likely to be prostate cancer in the absence

32:22

of, uh, a known malignancy that may metastasize to it.

32:28

And finally, uh, here's an example

32:30

of texture feature analysis.

32:32

So these are, this is the T2-weighted

32:33

image before and after treatment.

32:36

And you can see that it looks fairly similar.

32:39

Um, the energy component of the texture

32:42

features, which is, uh, a measure of

32:45

intensity, doesn't show a lot of difference.

32:47

But entropy, which is a measure of variation, shows a marked

32:53

change, uh, after treatment, and whether this will be useful

32:58

to evaluate, um, for adequate response,

33:02

um, is under, uh, intense investigation.

33:06

We may see this as a standard part

33:09

of our assessment in the near future.

33:12

Um, and finally, I should mention MRI and PET.

33:16

Um, this gives us the specificity of PET imaging

33:22

with the tissue, uh, tissue definition of MRI.

33:24

And as you know, PSMA is not yet clinically approved.

33:28

But, um, there are a number of studies showing

33:32

that it's useful for detecting recurrent disease

33:35

as well as for biopsy and surgical planning.

33:39

Um, and, uh, even with a PSA range as low as 0.2 to 0.5, um,

33:45

there's about a two-thirds detection rate on, uh, PSMA PET.

33:50

So this is something to look out for.

33:53

Um, if you can. Now we're lucky to have

33:56

a clinical trial of PSMA PET/MRI.

33:59

So we have a number of cases where we have, you

34:01

know, T2-weighted imaging, ADC, and then

34:03

here are the, uh, DWI, DCE, and PSMA PET.

34:09

And what you see is that although they all find the tumor,

34:13

the PSMA is much more specific for the site of tumor.

34:18

So PSMA may also be useful for treatment planning.

34:21

Now you don't need a PET/MRI.

34:24

You can get an MR and a PET separately.

34:27

Uh, and the MR is still very useful.

34:29

Um, but, uh, it remains to be seen how we will

34:31

implement PSMA PET, uh, in overall evaluation.

34:35

And, um, finally, uh, I'd like to

34:37

talk a little bit about focal therapy.

34:40

So the first question is, what

34:41

is focal or image-guided therapy?

34:44

This can be anything from intensity-

34:46

modulated radiation therapy to high-intensity

34:48

focused ultrasound or laser ablation.

34:51

It can be done using image fusion, uh, for

34:55

instance, for radiation therapy or ultrasound

34:57

guidance, or in the bore of the MRI scanner.

35:02

There's no specific protocol, uh, that is uniform,

35:06

and there's no standardized reporting recommendation.

35:10

Um, some techniques are not

35:12

compatible with in-bore treatment.

35:14

Um, other techniques you may want to decide

35:17

based on the location, whether you use one,

35:21

uh, imaging technique or another, and whether

35:23

you use, uh, MRI guidance or image fusion.

35:27

And, uh, we'll see that the post-treatment appearance

35:30

can vary depending on, uh, what kind of energy was used.

35:34

So the principle is if you have one significant tumor

35:39

and maybe some insignificant tumors, you could take the

35:42

whole prostate out, or you could treat, um, you know,

35:46

most of the prostate, just one side of the prostate.

35:49

Or even if you're certain about the

35:51

size, just the side of the tumor.

35:54

So here we see that there's a fairly large tumor,

35:57

um, with a number of benign tumors in the prostate.

36:01

Um, and could we have gotten away with

36:03

focal therapy of just this one tumor?

36:05

Probably.

36:06

Uh, and we can, uh, use surveillance to continue to

36:11

evaluate the satellite tumors, um, if the patient

36:14

wants to avoid the risks of whole-gland treatment.

36:18

There are a number of, uh, techniques or, uh,

36:21

energy modalities, everything from laser to

36:23

HIFU, uh, to irreversible electroporation.

36:28

And all of these, uh, are going to see an

36:31

increase in their use, uh, and possibly

36:34

stratification depending on the patient.

36:37

So what are the, uh, imaging considerations for planning?

36:42

Again, we know that MRI underestimates the tumor

36:45

size, and so we plan treatment based on the MRI

36:48

plus the location of positive systematic biopsy.

36:52

We also know that after treatment, the PSA will not

36:54

extinguish because most of the prostate is untreated.

36:57

And so we follow the PSA nadir, but we may

37:01

also need to re-image the patient because,

37:04

again, um, most of the prostate remains intact.

37:07

Um, there are proposed standards, but

37:09

these have not been widely accepted yet.

37:13

And how does treatment affect the imaging appearance?

37:17

So because this is gaining popularity, you

37:19

will likely see, uh, patients that have

37:22

undergone HIFU and maybe cryoablation.

37:25

You'll also see patients that have had a laser TURP.

37:29

Um, and this is a very similar appearance, uh,

37:32

between, uh, these two, uh, energy techniques.

37:36

The treated area shrinks.

37:38

Uh, early on you'll see very bright

37:40

signal with a dark rim on T2.

37:42

Um, but later on you'll see that it's, um, very dark

37:46

or almost completely, uh, signal void on T2-weighted

37:49

imaging, with a, uh, variable effect on the ADC, but

37:52

usually a decrease and overall decreased perfusion.

37:56

Uh, and there's, uh, a number of, uh,

38:00

articles in the literature to support this.

38:03

So, um, going back nearly a quarter century,

38:07

MRI was used to detect recurrence, and it took,

38:10

uh, over a decade after that to start to think

38:14

about, uh, the use of MRI for reevaluation

38:19

of these patients, uh, in this case, DCE.

38:22

Um, and now we're beginning to consider the

38:25

use of MRI for quantifying response, uh, and

38:29

how to, um, incorporate MRI for follow-up

38:35

and, uh, treatment planning.

38:38

Uh, we've also seen that MRI is a better predictor

38:41

of recurrence than just following the PSA, which

38:44

is why most of these patients will get imaging

38:46

follow-up regardless of their PSA kinetics.

38:50

However, PSA is still an important part of their management.

38:55

So here's an example of a patient

38:57

that went, uh, laser ablation.

38:58

On this T2-weighted image, you can barely make out that

39:01

there is a, a tumor here, uh, in the anterior transition

39:05

zone at the border with the, uh, peripheral zone.

39:08

Here you can see a laser fiber in the

39:11

tumor on MRI, and this is immediate, uh,

39:15

post-treatment imaging, the high B-value DWI.

39:18

Um, and you can see a large, uh, perfusion defect on, uh,

39:23

the immediate post-treatment, uh, contrast enhancement.

39:27

But this is six months later.

39:28

And what we see is the treated zone is actually

39:31

this very dark area here with kind of a

39:33

cystic change, uh, immediately adjacent to it.

39:37

Um, and, uh, the successfully treated area is bright on

39:42

ADC, dark on DWI, with no perfusion. Unfortunately,

39:49

uh, peripheral or distal to the treatment zone,

39:53

we see this sort of diffuse ADC abnormality,

39:56

but focal abnormality on high B-value

39:59

DWI and on, uh, dynamic contrast.

40:04

And this was, uh, biopsy-proven

40:07

recurrent or possibly residual cancer.

40:10

So, um, the techniques for focal therapy are

40:14

still being, uh, developed and perfected.

40:18

Um, and, uh, it's important to be conscientious to

40:24

evaluate, uh, these patients to see if they need an

40:27

additional treatment, which is an option for these patients.

40:32

Um, now here's, um, a patient after

40:35

cryotherapy rather than laser.

40:37

Uh, and so this was done with ultrasound, uh, and

40:41

this is, uh, uh, years after the initial treatment.

40:44

The initial treatment was in the anterior gland, and

40:47

what you see is that, again, it's very dark on T2,

40:50

it's dark on ADC, uh, but completely devoid of signal

40:54

on the high B-value DWI and devoid of perfusion.

40:57

Unfortunately, uh, what we see here is the sort of

41:00

intermediate signal intensity amorphous tumor on T2-

41:04

weighted imaging, kind of nonspecific compared to the rest

41:07

of the prostate, but it's got focal early enhancement.

41:11

Um, focal high signal on the high B-value

41:14

DWI and mildly restricted diffusion.

41:17

And this was a biopsy-proven recur-

41:19

rent or, or, um, uh, interval cancer.

41:22

So, uh, this patient has the option of surgery,

41:27

radiation therapy, or repeat focal therapy.

41:31

Um, and I wanted to contrast that

41:33

with the early post-cryotherapy image.

41:37

So we have a clinical trial looking at

41:40

patients one to two weeks out to

41:43

see if we can predict, uh, response.

41:46

And, uh, this is a very typical case.

41:49

You can see that the treatment zone is very high

41:52

signal on T2-weighted imaging with its black rim, a

41:55

very dark, uh, rim, and that the treatment zone shows

42:00

markedly restricted diffusion on ADC and DWI and this

42:05

sort of, uh, typical appearance with an enhancing rim.

42:08

No internal enhancement.

42:11

Now, if you didn't know that this patient had had

42:14

cryotherapy, um, and especially if you had the history

42:19

of UTI or fever or any, uh, source of infection, this

42:24

is exactly what a prostatic abscess would look like.

42:27

So context is crucial, though, you're

42:30

for evaluating these patients.

42:32

Uh, now obviously they're going

42:33

to be followed closely clinically.

42:36

And, uh, you know, vital signs will confirm that

42:41

this is just normal post-treatment-related change.

42:44

Uh, but it's important to be aware that early

42:47

on you can see a very different appearance

42:49

compared with the late changes in focal therapy.

42:53

Um, we're also looking at, uh, different forms of

42:55

quantitation, including susceptibility mapping.

43:00

So what are the take-home points?

43:03

PI-RADS version 2.1

43:06

is designed for primary significant

43:08

cancer, uh, detection and staging.

43:12

So untreated, uh, clinically significant cancer, dynamic

43:17

contrast enhancement and diffusion, especially the high

43:21

b-value DWI, detect recurrence both in the prostate itself

43:27

and in the surgical bed, and standards for the assessment

43:32

of response and, uh, reporting after treatment are evolving.

43:37

Uh, and we expect to see, uh, an initial, uh, recommend-

43:42

ed set of recommendations published, uh, later this year.

43:46

Um, but again, their performance remains to be established.

43:49

So although we will have recommendations for

43:52

assessment, we won't really know, uh, how

43:56

accurate they are until we have more data.

44:00

Uh, obviously I need to thank a number of

44:03

people for allowing me to do this kind of work.

44:06

Uh, so my chair for offsetting our research

44:09

costs and for, uh, keeping me gainfully employed,

44:13

um, my colleagues in urology, um, who both

44:17

refer patients and also, uh, cure the cancers.

44:21

Uh, and similarly, uh, my colleagues in radiation oncology.

44:26

Um, and maybe most of all my colleagues in pathology

44:29

who keep me honest, uh, and let me know when,

44:32

uh, I call something correctly and when I don't.

44:35

Um, but I should also thank the American College

44:37

of Radiology, uh, and, uh, the European Society

44:41

of Urogenital Radiology, who oversee the, uh,

44:45

PI-RADS, uh, committee, um, which was started

44:49

by the AdMeTech Philanthropic Foundation.

44:53

And the Society of Abdominal Radiology, which is doing

44:56

a lot to help further our understanding of prostate

45:01

MRI. Thank you very much for your attention, and I'm,

45:06

uh, interested to see if there are any questions.

45:09

Perfect.

45:09

Thank you so much for your time.

45:10

I do see a few questions in the Q and A feature.

45:13

Um, if you don't mind opening that and

45:14

just reading through some of those.

45:15

I know that you're pressed for hard

45:16

off at 1:00 PM, so we'll keep an eye.

45:18

Yes.

45:18

So

45:19

unfortunately, I have yet another

45:20

meeting, but we've got about 15 minutes.

45:23

So, um, when you say brightest on the DWI and

45:27

darkest on the ADC, um, the question is,

45:31

is this in that image or the whole gland?

45:33

That's a good question, and it's not really well established.

45:38

Um, effectively, it's the whole gland, with the

45:42

possible caveat that you normally see very

45:45

low signal corresponding to the central gland.

45:49

And so if something is as dark as that, it's probably

45:52

markedly hypointense, but there really shouldn't be

45:55

anything as bright as cancer on the high b-value DWI.

45:59

So, effectively, you can use just that image.

46:06

Uh, generally, if there is something that's markedly

46:10

hyperintense on the ADC and markedly hyperintense

46:12

on the DWI, it's probably another cancer.

46:15

So generally, we use just that image, but you can think

46:20

of it, um, relating to the whole prostate, especially if

46:24

you're way at the apex or you're at the base and you

46:26

want to get a better sense of what's normal for that patient.

46:30

Um, so there's a question about the erased

46:34

charcoal sign, which is one of the descriptors.

46:38

Um, and does that automatically

46:41

make it a PI-RADS five category?

46:43

So, erased charcoal margin is, um, that blurred, uh, margin

46:50

where you can tell there is not a narrow zone of transition.

46:54

Now, again, obscured is, I can't tell if

46:57

it's sharp or blurred because of features

47:00

of the prostate or technical, uh, aspects.

47:03

So obscured is when you can't tell if it's blurred or not.

47:07

Slurred means I am sure that the margin is not sharp.

47:12

I am sure that there is a broad zone of

47:14

transition, but that's only category four,

47:19

unless it's invasive or at least 1.5 centimeters.

47:24

Uh, so again, that would, uh, increase the,

47:28

uh, suspicion, uh, if it's large or invasive.

47:32

Uh, another question is about the endorectal coil.

47:36

Um, and we have good data to suggest that a three Tesla

47:41

magnet, um, does not need the use of an endorectal coil.

47:45

And we have some data to suggest

47:47

that a 1.5 Tesla magnet does.

47:49

Unfortunately, those of you that have done a

47:52

fair amount of body MRI have probably figured out

47:55

that your gradient performance is more important

47:58

than your field strength, and I'd rather have

48:02

a modern, well-tuned 1.5 Tesla magnet

48:05

than an old, kind of shabby three Tesla.

48:09

So you don't need an endorectal

48:12

coil at 1.5 Tesla in all cases.

48:16

Um, what you want to evaluate is can you get adequate image

48:21

quality on your T2-weighted imaging to determine whether features

48:25

are sharp or blurred, and can you get adequate signal

48:30

on your diffusion-weighted imaging to tell, um, whether or

48:35

not there is, uh, hyperintensity on the high b-value image.

48:39

Now, you may have software that will

48:41

calculate a high b-value image with, uh,

48:45

intermediate and low b-values, and that's fine.

48:48

We actually recommend that because it's more efficient, and

48:51

the performance is the same, but you still need to be able

48:54

to get adequate signal on your diffusion-weighted image

48:58

to evaluate lesions.

49:01

Um, I have another question about spectroscopy.

49:05

Um, spectroscopy is probably the most specific component.

49:11

Uh, unfortunately, it's very time-

49:12

consuming and very technically demanding.

49:16

And you're lucky if you have one or two techs

49:21

that know how to acquire adequate spectroscopy.

49:25

Um.

49:26

Unfortunately, it's also very finicky, so the same cases

49:30

which are going to be a problem on DWI are going to be

49:35

a bigger problem on spectroscopy when there's a lot of

49:38

gas in the rectum or when there's metal in the pelvis.

49:42

We generally only do spectroscopy in

49:45

research cases because it does not appear to

49:48

significantly add to our diagnostic confidence.

49:53

So I wouldn't dissuade you from doing

49:55

spectroscopy, but I also don't recommend it.

50:00

And so that's a related question.

50:02

What is multiparametric

50:03

MRI?

50:04

That means that you're doing T2-weighted imaging

50:07

and, uh, diffusion-weighted imaging, dynamic contrast-

50:12

enhanced imaging, and maybe spectroscopic imaging.

50:16

For a while, um, we would consider, um, spectroscopy

50:21

with either diffusion or dynamic contrast-enhanced

50:25

imaging to also constitute multiparametric MRI.

50:29

But with PI-RADS version 2.1, because the

50:33

evaluation depends so much on the three core

50:36

sequences, those are now multiparametric.

50:40

There's also the term biparametric,

50:43

which is T2 and DWI, without dynamic contrast.

50:47

Uh, and we should see a recommendation

50:50

from the PI-RADS committee about when and

50:52

when not to consider biparametric imaging.

50:57

Generally, if you can do multiparametric imaging, it avoids

51:02

those situations where you wish you had done it in the first

51:06

place, such as when the DWI is technically compromised.

51:12

And sometimes you can predict that when there is,

51:15

uh, a hip replacement, and sometimes you can't.

51:19

Um, for clinically insignificant tumors, uh, Gleason

51:23

three plus three equals six, or Grade Group 1.

51:26

What factors determine choosing active

51:28

surveillance over definitive treatment?

51:31

Um, that's a whole hour in itself.

51:35

It's generally up to the referrer.

51:39

But the current recommendations are if you have

51:44

only one or two sextants with less than half of a

51:49

complete core Gleason three plus three, that is

51:53

an appropriate patient for active surveillance.

51:57

There are some sites that will do active surveillance

52:00

for patients that have one core of three plus

52:04

four, meaning predominantly Grade Group 3.

52:07

Where it's, um, less than 50% of the core, um, sometimes

52:13

less than five millimeters, no more than two cores positive.

52:17

You can imagine this gets a little tricky with targeted

52:20

biopsy because you may have multiple cores in the

52:25

tumor that are positive, yet it's a very small tumor,

52:29

and so the number of cores is becoming less important

52:33

compared to the number of sites that are positive.

52:38

Um, there's a question about what are the optimal

52:41

B values for multiparametric, uh, 3T MRI.

52:45

Um, and those are defined in the PI-RADS document.

52:49

Generally, you want one B value between zero and 100,

52:53

ideally between 50 and 100, but zero is acceptable.

52:58

Um, and at least one between around 800.

53:01

So between, uh, 800 and 1,000. Um, 500 is

53:09

probably, uh, a bit too low for the maximum B value.

53:14

Um, and then you can add additional B values in between

53:18

those, um, to better characterize the ADC. Um, the

53:24

important thing is that you get adequate signal for both

53:27

the low B value and the high B value to calculate that ADC,

53:31

and you can also acquire a high B value image.

53:36

You don't want to use a B value above 1,000 in the

53:40

calculation of the ADC because of, uh, sorry about that,

53:44

because of, um, the, uh, diffusion kurtosis effects.

53:55

Um,

53:58

So you want to acquire that either separately or make

54:02

certain that your ADC calculation does not include

54:06

uh, the high B value DWI component. Um, is it more

54:11

possible in the, in the presence of brachytherapy implants?

54:14

So when the seeds are still in

54:16

place, it actually works fairly well.

54:18

Even diffusion, the seeds are small enough

54:21

and are the kind of metal that does not

54:24

cause significant susceptibility artifact.

54:27

The bigger problem is the whole prostate looks abnormal.

54:30

Um, and so we do not really know

54:32

how well we perform in these cases.

54:35

But we do know that we can detect at least

54:38

some and maybe most recurrent cancers.

54:41

So, uh, I would still recommend standard

54:44

multiparametric MRI, uh, in, uh, patients with a

54:48

concern for recurrence after, uh, brachytherapy.

54:53

So, uh, DWI categories four or five

54:57

change a, uh, T2 category three,

55:00

to overall, uh, sorry, T2 category two,

55:03

to overall category three in the transition zone.

55:06

Um, this only applies to the transition zone.

55:09

It does not apply to the peripheral zone.

55:12

In the peripheral zone,

55:14

we only care about the DWI and DCE.

55:17

We actually do not really care about T2, except

55:20

for determining whether or not a lesion is invasive.

55:25

Um.

55:27

And does enhancement change category two to category three?

55:31

No, enhancement is only used to change the category for

55:35

peripheral zone lesions that are DWI category three.

55:40

However, um, it can be very useful

55:44

to assess the overall size of the tumor.

55:48

And it can be crucial when DWI fails.

55:52

In that case, you have only DCE and T2-weighted

55:55

imaging, and the PI-RADS document describes how to use

55:59

those, uh, in both the peripheral and transition zone.

56:03

Um, and it can also be very useful for less experienced

56:06

readers, uh, because again, all the tumors light up

56:10

more or less, uh, and so it can help, uh, identify

56:14

small lesions that you might have initially overlooked.

56:19

Um, and, uh, one more question, uh, for transition zone

56:25

T2-weighted imaging and diffusion-weighted imaging,

56:28

um, and for peripheral zone diffusion-weighted imaging.

56:32

Oh, so, so for the transition zone, we use T2 and DWI.

56:36

For the peripheral zone, we use DWI and contrast, uh, and

56:41

this does not really change in PI-RADS version 2.1.

56:45

The main change was to the T2-weighted descriptors and

56:50

the ability to upgrade a transition zone category two lesion

56:56

to overall category three, but we still primarily use DWI

57:01

and contrast in the peripheral zone and T2 and diffusion

57:07

in the transition zone, uh, in technically adequate cases.

57:14

I think that encompasses, uh, all

57:19

of the questions we had today.

57:22

Uh, I would like to thank you all very much for your attention.

57:25

Hopefully this will be useful to you, uh, because I

57:29

think we are all going to see a lot of men, uh, with,

57:34

uh, treated and hopefully cured prostate cancer,

57:37

um, where we can be an important, uh, and likely crucial,

57:43

uh, component of their management, uh, in the future.

57:47

Thank you very much.

57:49

Perfect.

57:49

We just want to thank you for your time today, Dr. Merlis.

57:51

We really appreciate it.

57:52

And thanks all of you for participating in this noon

57:53

conference, and remind you that it will be made available

57:55

on demand, complimentary@mrionline.com, and tomorrow.

57:59

Please join us, Dr. Jim Wu will be with us for a

58:00

noon conference on imaging of soft tissue tumors.

58:03

Thank you, and have a wonderful day.

58:05

Stay well, everyone.