0:02

Hello and welcome to Noon Conference, hosted by MRI Online

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through free live educational webinars that are accessible

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by creating a free MRI online account.

0:29

Today we are honored to welcome Dr.

0:31

Lacey McIntosh for a lecture entitled Introduction

0:34

to Reading Oncology Pet ct.

0:37

Dr. Lacey McIntosh is an assistant professor

0:40

of radiology at UMass Medical School

0:42

and specializes in cancer and molecular imaging.

0:46

She currently serves as the assistant program director,

0:49

diagnostic radiology residency,

0:51

and the Division Chief Oncologic

0:53

and Molecular Imaging at UMass Memorial Medical Center.

0:57

She loves teaching and working with residents,

0:59

and we're grateful for her being here today

1:01

to share her expertise.

1:03

At the end of the lecture, please join Dr. McIntosh in a q

1:06

and a session where she will address questions you may

1:08

have on today's topic.

1:10

Please remember to use the q

1:12

and a feature to submit your questions so we can get to

1:14

as many as we can before our time is up.

1:16

With that, we are ready to begin today's lecture. Dr.

1:19

Macintosh, please take it from here.

1:23

Good afternoon. Thank you guys for having me today.

1:25

Um, I'm happy to talk to you about the introduction

1:28

to Reading Oncology Pet ct.

1:30

Um, I'm a cancer imager,

1:32

and so the way we're gonna kind of approach these today is,

1:36

um, from the oncology lens.

1:37

But you guys all know that PET is used

1:39

for more than just oncology.

1:41

We've got some dementia imaging

1:42

and vascular imaging, um, you know, a variety of things,

1:47

but we're gonna kind of stick to oncology.

1:49

Um, it's gonna be a little bit of a different topic

1:51

because this is a little bit more didactic

1:54

and kind of based on processes, um,

1:58

and kind of reporting rather than imaging.

2:01

So hopefully I can keep you guys, uh,

2:03

paying attention even though there's not a lot

2:05

of pictures here today.

2:06

So, um, and as mentioned, please feel free

2:09

to enter questions into the, um, question

2:11

and answer section, and I'm happy

2:12

to go over those at the end.

2:14

I think we'll have some extra time.

2:16

Um, okay,

2:21

let's see some, so some disclosures.

2:23

Um, I help MRI online with, uh, curriculum design

2:26

and oncology, um, related things.

2:29

And then I do some consulting, um, for several

2:33

clinical trial, uh, sponsors.

2:35

Um, this is, this lecture is based on some materials

2:39

that we prepare for our residents at UMass.

2:41

And so I just wanted to, uh, acknowledge doctors Evan Rappel

2:44

and Elisa qut, um, who have helped with creating this,

2:47

um, this lecture.

2:50

So, today, objectives, um, we're going

2:52

to have an introduction to an oncology oriented approach

2:56

to reading PET ct.

2:58

Um, hopefully

2:59

after this lecture, you will gain some understanding in the

3:02

role of PET C Teen Cancer Imaging, really kind

3:04

of exploring indications, um,

3:07

looking at details about reporting purpose

3:09

and structure, um, kind of thinking about qualitative

3:14

and quantitative assessments within your report,

3:16

and then really providing a comprehensive interpretation.

3:20

Um, so like I mentioned this,

3:22

this lecture is largely focused on approach and reporting.

3:26

Um, so we'll dive right in.

3:29

So for reports, um, you know, every attending has

3:33

and every, you know, reader has a different kind of style

3:36

that they like to look at,

3:37

but I think most people usually have these general

3:40

components of the report.

3:41

Um, you know, with one section being history, an indication,

3:45

um, another looking at technique

3:47

and then kind of the body

3:48

of the report describing the findings.

3:50

And then finally at the end, a conclusion or impression.

3:53

Um, so what I teach our residents is that, you know,

3:57

your job with this exam is to really find out,

4:01

do your homework and figure out

4:02

what the clinical question is.

4:04

Um, and that really should be your number one impression

4:07

point is answering that question.

4:09

Um, so we're gonna talk about today kind

4:11

of the various reasons that clinicians will order pet ct

4:15

and kind of how we answer those specific questions.

4:18

Um, so going into, um,

4:22

the indications section of the report.

4:24

So, um, you know, you cannot just read these, uh,

4:30

and PET cts in isolation.

4:31

We really have to know kind of what is the goal.

4:34

So here's some examples of things that people may be looking

4:37

for when they order a pet CT on one of their patients.

4:39

So, um, you know, are we looking for malignancy

4:43

or inflammation based on symptoms?

4:45

Sometimes, you know, a patient might have night sweats

4:49

or, uh, unintentional weight loss,

4:52

and they haven't been able to identify any sites

4:55

of disease either by clinical exam

4:57

or with, um, you know,

4:59

traditional imaging modalities like CT or MRI or ultrasound.

5:03

And so they may really strongly suspect

5:05

that there's something going on with the patient,

5:07

whether it's cancer or an inflammatory disease like sarcoid,

5:11

and they're looking for a place, they're either looking

5:14

for imaging evidence

5:15

or looking for a place to biopsy to confirm, um,

5:19

their suspicions.

5:21

So we kind of think about those

5:22

as like a fishing expedition, right?

5:24

Um, other reasons that we do pulmonary nodules, uh,

5:28

are a big indication for PET ct.

5:30

Um, and so sometimes we're characterizing findings

5:32

that we've seen on other imaging.

5:34

Often there's, uh, you know, a, a preceding CT

5:37

or sometimes MR that sort of triggers the pet, uh,

5:41

because we're trying to figure out what's going on

5:43

with a finding that we've seen elsewhere.

5:45

Um, sometimes we're looking for a suitable biopsy site.

5:49

Uh, we may have imaging evidence of a disease, for example.

5:53

Um, you know, we could have CT evidence of multis

5:57

lymphadenopathy, um,

5:58

but we're looking for the best place

6:01

to be able to biopsy it.

6:02

We don't know if a certain lymph node is involved,

6:04

or we do know that a lymph node's involved,

6:06

but it's a very, um, technically challenging biopsy to do.

6:10

So we're looking for an alternate area that we might be able

6:13

to more easily access to to get that tissue diagnosis.

6:17

Um, sometimes the diagnosis is already known, um,

6:21

and we're just looking to either identify a primary

6:24

or, um, give an initial staging.

6:27

Um, so for example,

6:28

here we might have a patient who's had a ct,

6:31

and we have found, um, multiple liver lesions

6:34

that look like metastatic disease.

6:36

Um, this has been biopsied

6:38

and there's, you know, a carcinoma

6:40

or an adenocarcinoma of unknown primary site.

6:43

Um, and so what we're doing is we're, we're not only like,

6:46

you know, staging the patient

6:47

and figuring out what other sites of disease are involved,

6:50

but we're looking for a primary that may not, you know,

6:53

have either been imaged

6:54

or may not be apparent on the previous imaging.

6:57

Um, we also run into this sometimes with our DOTATATE scans,

7:00

which are done, uh, for neuroendocrine tumors.

7:03

So the, if,

7:04

if you have a primary neuroendocrine tumor in the small

7:07

bowel, those are kind of notoriously known

7:09

for being difficult to identify by ct.

7:12

Um, and they can be, you know, kind of cul

7:14

by other forms of imaging.

7:16

So sometimes we know we have metastatic neuroendocrine

7:18

tumor, but we're really looking for that primary, um,

7:21

primary site or multiple primary sites

7:24

to determine if the patient, um,

7:26

can be managed in a local way

7:27

or if they need systemic therapy.

7:30

Um, we also do PET CT for restaging

7:33

or assessing treatment response.

7:35

So if a patient already has a known disease,

7:38

it's already been staged,

7:39

they've had chemotherapy initiated, um, you know,

7:43

lymphoma's a really good example of that.

7:45

Most patients get an interim stage restaging exam, you know,

7:49

after two or three cycles of therapy.

7:51

And what we're looking to do is figure out

7:53

how is the treatment working?

7:55

How well is it working? There can be prognostic information

7:58

that we get from, um, you know, kind of gauging

8:01

what the initial response looks like.

8:03

Um, so, you know, determining if our treatment's working.

8:07

Um, sometimes patients have already completed their

8:10

treatment course for their cancer.

8:12

Um, and based on, you know, what the response looked like

8:16

or what the nature of the disease was, how high risk it was,

8:20

PET CT may be used for surveillance.

8:22

Um, you know, even

8:23

after the patient has completed everything, kind

8:26

of just monitoring to make sure that

8:28

that disease stays at bay or is quiet or is cured, um,

8:32

and looking for any sort of recurrence in a,

8:34

in a surveillance kind of setting.

8:36

Um, sometimes we're doing a pet to follow up a finding

8:40

that was identified on a prior pet.

8:43

Um, the thing that kind of most often comes to mind

8:46

with this are head and neck cancers.

8:48

Uh, a lot of these patients are treated with chemoradiation

8:51

and so on their, you know, post-treatment pet, they get,

8:56

um, they, you know,

8:58

may have some residual FDG avidity in their cancer.

9:02

And what's difficult to tell kind

9:04

of in the immediate post-radiation setting is does

9:07

that represent residual disease

9:09

that still needs further treatment,

9:11

or is this just responding disease

9:14

that hasn't quite quieted down?

9:15

Is there post-treatment inflammation?

9:17

So sometimes the purpose of the pet is to follow up

9:20

what we saw on a prior pet.

9:22

Um, and then I'll just mention these

9:25

'cause today's really focused on oncology,

9:27

but you know, there's lots of other non

9:29

oncologic indications.

9:30

Um, you know, here at UMass we do quite a bit

9:33

of cardiac sarcoidosis.

9:35

Um, there can be vasculitis, workups

9:37

or other rheumatologic assessment, um, brain imaging

9:41

and dementia, just to kind of mention a few of, of the ones

9:44

that come up frequently.

9:47

So when I'm crafting my report,

9:49

and this is kind of what I really, um,

9:51

drill into our residents when they're crafting their

9:54

reports, is, um, an indication is really an opportunity

9:57

to kind of pull together all of the clinical information.

10:01

Um, you know,

10:03

and for PET ct, you really can't read these in isolation.

10:05

You can't just open the pet and interpret what you see.

10:08

Um, it's really an opportunity to kind

10:11

of like pull together all the imaging that's been done

10:13

and really figure out what's going on with the patient

10:16

and what's, what's the question.

10:17

So, um, I'll show you guys in a few slides the formula

10:21

that I use to kind of craft, uh,

10:23

craft the indication and craft the report.

10:26

Um, but the things that I always want

10:28

to know when I'm reading is the tumor type

10:30

and you know, specifically the histology.

10:33

And that's obviously if we know it.

10:35

Um, if we don't have a diagnosis yet,

10:36

then all we really have is like findings or symptoms.

10:39

But, um, you know,

10:42

different tumors can have different patterns of spread

10:45

or different sites that they like to involve and, uh,

10:49

or just different kind of metabolic behavior.

10:52

Um, you know, uh, triple negative breast cancer

10:56

may have different patterns of spread than say,

10:59

a lobular cancer, which, um, may kind

11:02

of involve atypical sites.

11:03

And the FDG avidity is not always particularly high.

11:07

So, um, you know, when I am walking into an exam,

11:12

I wanna know kind of what I'm looking for,

11:13

where I should be looking

11:14

and how sensitive I need to be based on sort

11:17

of inherent FDG avidity.

11:19

So tumor type

11:20

and histology, specific histologic features if known

11:24

are important to me.

11:25

So I like to know those and put those in my indication.

11:28

Um, also, if a patient ha is not in the staging,

11:33

but they're in a restaging or, um, you know, a follow-up

11:37

or, uh, reassessment

11:38

or restaging scenario,

11:41

I wanna know about the prior treatments

11:42

and, um, what their timeline look at look like,

11:45

which may affect the read.

11:48

Um, and you wanna know about kind of the most recent line

11:51

of treatment that they're on

11:52

or when treatment has been changed.

11:54

And the reason for this is

11:55

because a lot of these patients through the course

11:57

of their treatment, especially if they've failed multiple

11:59

lines of chemotherapy or local therapies

12:02

or had recurrences, um, you know,

12:06

they may have a lot of imaging, right?

12:07

And so if you are reading the current pet and the pa,

12:11

and this goes for all cancer imaging,

12:13

if you're reading the current time point

12:15

and they have only been on that drug for say, three months

12:18

or six months, you wanna be comparing to the prior study

12:22

that is done at the initiation of that treatment if you're,

12:26

because the question you're answering is,

12:28

does this treatment work?

12:29

And so you wanna look

12:31

and compare to since when that treatment was started.

12:34

If you compare to a study that was done a year ago,

12:38

that's not really answering the question about

12:41

how is this drug working,

12:43

because a year ago they were on a different drug

12:45

and maybe that drug worked, or maybe that drug didn't,

12:47

but you're kind of providing an interpretation that's not

12:51

relevant to the clinical context.

12:53

And so when you read these studies,

12:55

you really should be comparing

12:57

to similar time points from when the

12:59

patient's been on the same drug.

13:01

Um, you know,

13:02

and you should be aware of if they've had treatment breaks

13:04

or, you know, toxicities that require them to, you know,

13:09

stop and take steroids.

13:10

And, um, all of those kind of factors can kind of impact,

13:15

uh, how you interpret what you're seeing.

13:17

So you wanna make sure that your, uh, your comparisons are

13:21

relevant and appropriate.

13:23

Um, and we all know from practice that

13:25

that may not always be the case.

13:27

Sometimes you are in a situation

13:28

where the patient's been on a treatment for three months,

13:31

and the only comparison that you have is from six or nine

13:34

or 12 months prior.

13:35

And so, um, in those cases, you kind of have

13:39

to just say what you see.

13:41

Um, but I usually try to alert them to, you know,

13:44

since the prior imaging, this is what I see.

13:48

But please keep in mind

13:49

that the prior imaging was not done at the same time point

13:53

as like the initiation of therapy or something like that.

13:56

Um, you know, that really is up to the clinician to kind

13:58

of put those pieces together,

13:59

but the more that we can help that

14:01

and kind of understand how our read fits in,

14:03

we can be helpful to our clinician counterparts.

14:06

Um, so next point, try

14:09

to understand why the pet is being done at this point.

14:12

Like, are we looking at a specific time point in treatment

14:15

or, you know, has the patient been doing well,

14:17

but now all of a sudden they have new back pain?

14:20

Is there something we should really hone in on

14:22

or their new findings seen on a ct?

14:25

Um, you know, sometimes it might be

14:27

that like a new liver lesion has been seen

14:28

and we're specifically, you know, trying to work that up

14:31

and we need to know what does

14:33

that look like on the prior imaging?

14:34

Is it so tiny that we can't interpret it by pet?

14:37

Is it, you know, newly appreciated?

14:39

But if we actually go back, it's been there for 10 years

14:42

and we just couldn't see it on, you know,

14:44

certain phases of contrast.

14:45

So we really need to kind of know what we're looking at and,

14:48

and what we're trying to interpret.

14:50

Um, this is kind of, you know, for, for those

14:53

of us practicing in the states, um, billing purposes,

14:57

they really want this verbiage of, uh,

14:59

initial versus subsequent treatment strategy.

15:02

Um, staging and restaging sometimes don't, um,

15:06

meet the criteria for reimbursement.

15:08

So this is one that our billing department always really

15:11

asks us to make sure that we use this, um, you know,

15:14

preferred language of initial versus

15:15

subsequent treatment strategy.

15:20

So here's kind of a formula I use to create my indication.

15:23

So, um, you know, type of cancer, uh,

15:26

and, you know, obviously location

15:28

of the organ that's involved.

15:29

So an example of this would be

15:31

adenocarcinoma of the stomach.

15:33

And there are certain features that I like to know about,

15:35

like signet ring features.

15:37

Um, when cancers have this specific feature,

15:40

there's a higher propensity for it

15:42

to involve the peritoneum.

15:44

Um, so if I know

15:45

that the patient has signe ring features in their tumor

15:48

tumor, I will kind of scrutinize the peritoneum a little bit

15:51

more carefully and I'll interpret, you know, small findings

15:54

that you might otherwise blow off

15:56

or say, oh, that's just like a small lymph node

15:58

or, uh, you know, if you're reading say,

16:01

a pulmonary nodule workup,

16:02

you may not really give the same degree of, uh, weight

16:06

or significance to a small peritoneal finding

16:09

as you would if, um, you know that it's an adenocarcinoma

16:13

with significant ring features.

16:14

So, um, that, those are kind of some clues

16:17

that I think help us help ourselves

16:19

and help us kind of know what to look for.

16:21

Um, so treatments

16:23

and timeline, this is obviously only applicable if the

16:26

patient's on a treatment,

16:27

but, um, you know, an example

16:29

of this might be currently on FOLFOX since a

16:32

particular date, right?

16:33

Because then we know what's our timeline,

16:35

when should we be looking at?

16:37

We can kind of ignore things that have been done prior

16:39

to this because they aren't relevant

16:41

to this particular treatment.

16:43

Um, another thing that's important too is to know about, um,

16:47

any local treatments

16:49

that have been administered to the patient.

16:51

So, um, if you're trying to answer a question of,

16:55

is my drug working, then if a patient has had radiation

16:59

to something, or in this example, an ablation

17:02

to a liver lesion, when you see a response

17:06

or a change in that particular finding,

17:08

we can't really attribute that

17:09

to the systemic treatment, right?

17:11

And so, um, you know, we, we kind of need

17:14

to know if things have been treated in a local manner.

17:18

So if we see that disease is progressing everywhere except

17:22

for a right liver metastasis that's been ablated,

17:25

there's two ways to kind of look at that, right?

17:27

One way that you could read that is, oh,

17:29

there's a mixed response.

17:30

And what you're saying when you tell a clinician

17:33

that there's a mixed response is

17:34

that the drug is working on some disease

17:36

and it's not working on other disease,

17:39

and that might be due to disease heterogeneity

17:42

or the acquisition of a mutation.

17:44

We think about like EGFR lung cancers.

17:47

Um, and so that has treatment implications

17:50

because treatment might not be changed

17:53

or that treatment, if it's working on certain parts

17:55

of certain, you know, portions of disease might be continued

17:59

and then treatment gets added to that to treat the disease

18:02

that's not responding.

18:03

Um, or it might result in, you know,

18:05

an overall treatment change.

18:07

But if you know that that lesion has been ablated,

18:11

then really the better interpretation

18:13

and the more accurate interpretation of what's going on is

18:16

that, you know, your,

18:18

your systemic treatment isn't really working.

18:20

Everything that's being addressed by that is progressing.

18:23

You have a response in this liver metastasis,

18:26

but that's simply because it's been ablated.

18:28

And so you can see it's a little bit different

18:31

and it has different implications as to

18:33

what the clinicians are gonna decide to do in terms

18:35

of like their next step of management.

18:37

So again, just kind of stepping back, it's important

18:40

to know if things have been addressed in a local manner,

18:42

whether it's radiation or ablation

18:45

or surgical resection, um, to kind of sort out the responses

18:49

that you're seeing in different findings.

18:51

Um, so then purpose of the study, like I mentioned,

18:54

the preferred terminology is either initial

18:56

or subsequent, um, treatment strategy,

18:59

but I'll often add additional language, like, you know,

19:02

evaluate liver lesions seen on prior CT,

19:05

or, um, you know, anything that's been

19:08

detected clinically you wanna talk about as well.

19:11

So an example, you know, using these kind of pieces

19:15

for the formula might be adenocarcinoma of the stomach

19:18

with sign ring features currently on FOLFOX since 9 5 20 22,

19:22

and status post ablation

19:24

to a right liver metastasis subsequent treatment strategy.

19:28

Um, you know, every kind of reporting system

19:32

and PAX and ordering system is very different,

19:36

but, um, you can consider not including things like

19:40

patient age or sex.

19:41

Um, these, you know, at least at my institution,

19:44

are already part of the report

19:46

and really only leaves room

19:47

for errors if you have like a mis dictation of the patient,

19:50

um, you know, patient's age

19:52

or, you know, just kind of leaves room for errors.

19:55

And, you know, adequacy

19:56

and, uh, accuracy of reports is really important.

20:00

I think when patients, especially now that they have access

20:03

to really pretty much everything,

20:05

whenever they see errors, even if it's like spelling

20:07

or grammar errors, it just kind of opens the door for them

20:11

to, um, mistrust what you're saying

20:13

or what you're interpreting.

20:15

So I really try to keep the reports just

20:18

with relevant information and not redundant

20:20

and not mentioning things

20:23

that are already kind of attached to the record.

20:25

Um, and then disease stage is, I think

20:29

that's a personal preference,

20:31

but personally for me, um, sometimes in the initial stages

20:35

of kind of figuring out what's going on with a patient,

20:38

it can be reported incorrectly

20:40

or, um, it can change as new information becomes available.

20:44

An example of this might be where you have a lung cancer

20:47

that's detected on, um, you know, a chest CT

20:51

and then a, an abdominal pelvic CT or a pet CT is done

20:55

and we think we know the stage,

20:57

but then we find out that there's a brain metastasis, right?

21:00

That might not have been imaged

21:01

or it might not have been apparent by the prior imaging.

21:03

And so, um, you know, I kind

21:06

of usually leave those details out just

21:08

because it again, leaves room for error.

21:10

The clinicians know what the stage is

21:12

and they're kind of operating based on those

21:14

assumptions and that information.

21:18

Um, okay, so I think we really kind of drilled into the, uh,

21:21

into the indication section.

21:23

So kind of moving on into technique, um, information

21:26

that we usually include

21:28

for the technique section would be the dose injected.

21:31

Um, and the site of injection I like to include, um,

21:36

just because if you see activity at this site,

21:38

you can explain it by where the site of injection is,

21:41

or sometimes if there's been an infiltrate, uh, at the site

21:44

of injection, you can get some uptake in those ipsilateral

21:47

axillary lymph nodes.

21:49

Um, so it's always kind of nice for me

21:51

to know when I'm interpreting if I see something like that

21:53

where the injection site was.

21:55

Um, you know, obviously if there's been an infiltrate,

21:58

you wanna kind of communicate that as well to the clinician.

22:01

Um, for FDG, we wanna know about the blood glucose levels

22:05

and for us we use a cutoff of 200, um,

22:08

milligrams per deciliter.

22:10

And the reason for that, uh, you know, is

22:13

that endogenous glucose will compete with FDG.

22:16

And so if you have high levels of circulating blood glucose,

22:20

um, then you will have poorer tracer binding

22:23

because your FDG is not able to kind

22:25

of incorporate into the cells in the same way

22:28

because all of the, um, glute transporters have already kind

22:31

of done their job and saturated the cells with glucose.

22:34

So if we have a patient that, you know, hasn't ED

22:37

or their blood glucose level is greater than 200,

22:41

we usually have them reschedule

22:42

because it can affect, you know, the sensitivity

22:45

and the quality of the study.

22:47

Um, some other things to know are the time between injection

22:50

and acquisition, um, everywhere.

22:52

It's gonna have a slightly different protocol,

22:53

but we really like it to be around 60 minutes.

22:57

Um, and it should be pretty uniform from, you know, exam

23:00

to exam between patients and between each patient's exam.

23:04

Um, that helps us kind of be able

23:05

to compare apples to apples.

23:07

Sometimes if you wait too long to image,

23:09

you're gonna have a cumulative effect of higher SUVs

23:11

and then it becomes a little bit tricky to be able

23:13

to compare exam to exam.

23:16

Um, field of view information, um, this is largely

23:20

for billing, but also, you know, just accuracy.

23:23

The standard field of view

23:25

for most oncology studies is the base

23:26

of skull through the thighs.

23:28

But, um, you know, for head

23:29

and neck cancers, we kind of go to the vertex of the skull

23:32

and include that and for, um, you know, whole body pet CT

23:37

for multiple myeloma or melanoma

23:40

or sarcoma cases, um, we'll really go from vertex

23:43

of the skull all the way through the toes.

23:46

Um, so it's important to just kind

23:47

of accurately describe these things

23:49

and your institution may ask you to include other things

23:52

as well, kind of depending on

23:53

what carries over from the patient record and report.

23:56

But, um, here below I have a few examples of just, you know,

24:00

kind of what we use for FDG dotatate and, um, PSMA.

24:04

These are just several different tracers

24:06

that we have available here, um, at our institution.

24:12

Um, and then talking about SUV, uh,

24:16

this is really more for quality control.

24:18

I think SUV used to be heavily used in interpretation.

24:22

Um, and now that we're doing PET for so many more things,

24:25

and especially in working up small findings in particular

24:28

pulmonary nodules, it has less of a role in interpretation.

24:33

Um, there are some exceptions with lymphoma.

24:35

We do reference, um, you know, background liver, FDG uptake,

24:40

um, you know, kind of qualitatively comparing to liver

24:43

and background mediastinum.

24:44

But, um, you know,

24:46

the historical thinking was if something's more avid than

24:49

background liver, it's more likely to be malignant.

24:51

And if it's less avid than background liver,

24:53

it's more likely to be benign.

24:55

But we've kind of entered a higher level of interpretation

24:59

with that because we all know,

25:01

and we've all seen plenty of things

25:02

that are less avid than liver that are definitely malignant.

25:05

And you know, the reverse of that is true as well.

25:08

Um, so when we take a a mean SUV in the liver,

25:12

we usually take a 3.5 centimeter, um, area or sphere,

25:17

and we, uh, take the mean SUV at that location

25:21

and it's really for quality control.

25:22

Is their patient adequately fasting?

25:24

Is there good bio distribution?

25:27

Um, and you know, kind

25:28

of less importantly used in in interpretation, um,

25:32

we really only talk about this for FDG.

25:34

Uh, that's the only place where it's validated.

25:37

We don't really know how to use SUV in the same way

25:41

for the other tracers.

25:42

So when we are interpreting SUVs, uh,

25:46

or when we're reporting SUVs in

25:48

FDG, we know what those mean.

25:50

Um, at our institution, we,

25:52

and I think this is pretty generally accepted,

25:54

that when you're reading other tracers,

25:55

we don't really report SUV, we use more

25:58

of a visual interpretation

25:59

and use descriptive terms,

26:00

which we'll talk about going forward.

26:03

So, um, this lecture is not a technical lecture on pet,

26:07

but just a note here on what SUV is,

26:09

it's a semi quantitative measurement

26:11

of radiotracer uptake within a region of interest.

26:13

And we're kind of looking at the measured activity

26:16

concentration in a tissue at a certain time,

26:19

and then, um, dividing that

26:21

by the injected dosed divided by the body volume.

26:23

And that's what gives us our SUV at a particular time point.

26:27

So, um, if you are in research, there's lots

26:30

of different ways to look at SUV,

26:32

but clinically the, the most commonly used ones

26:35

that we talk about are an SUV mean, um,

26:37

which we just talked about is the average of values,

26:40

and we look at that in the liver,

26:42

but what we're usually reporting with each finding, um,

26:44

for FDG is an SUV max, which is the highest voxel, uh,

26:49

value in a defined, um, VOI.

26:51

So we'll go too, too detailed here,

26:54

but it's just to kind of know about

26:56

and, um, you know, things to consider.

26:59

But there are factors that impact your SUV.

27:01

There's biologic factors like weight composition,

27:05

body size calculation, blood glucose levels, um,

27:08

the post injection time, which we sort

27:10

of touched on already, and respiratory motion, um,

27:14

reconstruction and lesion size will impact SUV.

27:17

And also, depending on your field of view

27:19

and what you're measuring it, you can have the same finding

27:22

that you measure with two different fields or,

27:24

or that you look at in two different fields of view

27:26

and you will get different SUVs.

27:27

So SUV is not the end all be all, it's, you know,

27:32

it's an impacted by a lot of things,

27:34

but it's a very useful tool that we can like use

27:37

to look at metabolic activity and metabolic behavior

27:40

and use for comparison with FDG studies.

27:42

So, um, there's some good references here if you want

27:45

to learn more about it, but, um, sort of just kind

27:49

of mentioning it here.

27:52

Um, so SUV is not enough on its own, as I mentioned.

27:57

We really, um, I find that we really need to, in addition

28:01

to the quantification of SUV, we need to also provide a,

28:05

a qualification where we're kind

28:07

of providing a visual interpretation

28:09

of the degree of uptake.

28:11

And I'll talk about this in the next couple slides.

28:14

Um, and when I say SUV max alone is not enough,

28:17

this is a question that often comes up at,

28:19

at, you know, tumor boards.

28:20

I can think of an example when we're talking about

28:22

like a pulmonary nodule.

28:23

People will say, well, what's the SUV?

28:26

And depending on the size of your finding,

28:29

if you have a very small pulmonary nodule,

28:31

smaller things are just gonna be less avid, right?

28:33

They have less cells, they have less glucose transporters,

28:36

they're just not able to incorporate

28:38

as much FDG into their cells as a large finding with many,

28:42

many more cells will be able to.

28:44

Um, and so I'll give them an SUV,

28:47

but it might not sound very impressive, right?

28:49

If you'll say, oh, it's three, they'll say, oh,

28:51

liver's three, but you say, no, no, no,

28:53

we can't interpret those, those small

28:55

findings in that same way.

28:57

Um, so you know, an SUV max of five

29:00

and a sub centimeter nodule is not the same as an SUV max

29:03

of five and a five centimeter mass.

29:05

Um, so I'm gonna show you an example here.

29:07

This is just one from some cases that I had here at UMass.

29:10

So at the top we can see

29:13

that there's a finding in the right upper lobe, um,

29:16

which is circled with the green circle here,

29:18

and it's, you know, a consolidated opacity.

29:21

Um, we look at the pet, uh, images on the left,

29:25

and you can see there's an SUV max of 3.1, right?

29:28

But like looking at this,

29:29

this is a not very impressive metabolic finding, right?

29:33

We look at it, and it's very similar

29:35

to the background mediastinal structures.

29:37

The message that this is sending is that this is not

29:40

very metabolically active.

29:42

Um, I would describe this as maybe minimally FDG avid.

29:47

Uh, so we look at the case below on the bottom,

29:50

and this is a small finding, it's probably one

29:53

and a half centimeters.

29:54

We can see it circled again

29:55

with the green circle on the right.

29:56

This patient obviously has bigger issues in the right lung,

30:00

there's a huge tumor here,

30:01

and this is an intra pulmonary metastases

30:03

to the contralateral lung.

30:05

But we look on the pet, uh, images

30:07

and we also have an SUV max of 3.1, right?

30:11

So the message that we're sending here when we say, oh,

30:15

the SUV max is 3.1, is a little bit ambiguous, right?

30:19

We don't know, well, what does that mean?

30:21

You know, our finding is so small, what does a 3.1 mean?

30:24

So in the, in the example on the top,

30:27

I would say this is minimally FDG avid,

30:29

but in the example on the bottom, I would describe this

30:31

as intensely f dg, avid, right?

30:32

And that's sending the message.

30:33

This is like definitely aggressive.

30:35

This is definitely malignant.

30:37

Um, and so turns out, yes,

30:39

this is an int pulmonary metastasis,

30:41

this is squamous cell carcinoma on top.

30:44

This is actually a mucinous adenocarcinoma.

30:46

So even though it's minimally FDG avid,

30:48

it is also malignant.

30:49

So I'll back up to the slide before.

30:51

So, um, you know, these two findings, both have an SUV max

30:55

of 3.1, but they look very different, right?

30:57

And they're behaving very different.

30:59

And the whole point of having this, you know,

31:01

metabolic imaging is to show us how things are behaving.

31:04

So in addition to the SUVs,

31:07

I also provide a visual

31:08

interpretation of the degree of uptake.

31:09

So I use words like minimal, mild, moderate, or intense.

31:14

FDG uptake is seen in the, in this example,

31:17

pulmonary nodule, which measures 1.5 centimeters

31:21

with an SUV max of 3.1.

31:23

So describing it in this way

31:25

where you have both the qualitative

31:27

and the quantitative measures kind of helps us correct

31:29

for size, you know,

31:30

smaller things are just gonna be less avid.

31:32

I'll say that over and over again today.

31:35

Um, so moving into the, uh, findings section, um,

31:40

I kind of, I like to use formulas, um, in my reports.

31:43

I think in general people prefer standardized reporting,

31:47

and if you use formulas, it makes it very easy to kind

31:50

of navigate your report

31:51

and figure out where the information

31:53

is that you're looking for.

31:54

And it's also helpful in comparison.

31:56

So, um, you know, an example that, you know, we kind

32:01

of just went through, but I'll go through again,

32:03

is in the pink here.

32:04

I'm using these qualitative descriptors of

32:06

how much avidity there is.

32:08

So no appreciable, barely perceptible, minimal,

32:12

et cetera to intense.

32:14

FDG uptake is seen in the left upper lobe pulmonary nodule,

32:18

which measures 1.5 centimeters with an SUV max

32:21

of 3.1, right?

32:23

So here's another example here.

32:25

Moderate FDG uptake is seen in the peripheral, right?

32:27

Lower lobe solid nodule, which measures 1.4 centimeters

32:30

with an sev v max of 3.2.

32:33

So just as a note for non nodal findings,

32:36

when you are looking at t staging,

32:38

and most cancers use TNM staging, not all,

32:41

but many cancers use TNM, um,

32:44

really only the longest axis measurement is relevant.

32:48

Um, you know, so personally for me as a cancer imager,

32:52

when I report the size of a tumor,

32:54

I really only give one dimension.

32:56

If somebody is specifically asking about, you know, volumes,

32:59

I'll give three dimensions,

33:00

but, um, you know, I will give the one longest dimension

33:04

because if that's, you know, a surgical patient

33:06

and it gets resected, we want that to, to match, right?

33:09

We wanna, we wanna be able

33:10

to give the longest axis measurement.

33:12

And that's not always gonna be on your axial.

33:14

A lot of times it is.

33:16

But, um, you know, if it's a coronal measurement,

33:19

then you do wanna take that

33:20

because that's important for predicting the T stage.

33:23

Um, you can give multiple measurements.

33:26

Personally, I, I kind of don't,

33:29

I find it a little bit confusing.

33:30

And the, the measurements

33:33

that are not the longest access are sort of, um,

33:36

you know, non-contributory.

33:38

And I often see this in, you know,

33:40

sometimes in trainees reports

33:41

where like three measurements are given.

33:43

And if you're gonna do this, you really should lead

33:45

with the greatest measurement

33:47

because I think, you know,

33:48

there's just like a lot of information here.

33:50

And what the important one is,

33:51

is really the longest measurement.

33:53

So I encourage you for non nodal findings

33:56

to really just report one axis of measurement.

33:59

Um, you know, and you can specify which axis that

34:02

or which kind of plane you found that in.

34:05

Um, but you know, I think we can kind

34:08

of do without these other ones in, in my opinion.

34:11

Um, so another example of this would be intense.

34:14

FDG uptake is seen with an enlarged per aortic lymph node,

34:18

which measures three centimeters by 2.1 centimeters

34:20

with an sev v max of 9.8.

34:22

So lymph nodes are different.

34:24

Um, I think a lot of us are taught

34:26

that only the short axis measurement is important.

34:29

But, um, you know, as a cancer imager, we kind

34:33

of always use two axial measurements to report lymph nodes

34:37

and listing the long axis first.

34:39

Um, lymph nodes are often small,

34:42

and so this is a better way to kind

34:43

of volumetrically assess 'em.

34:45

Um, and if you look at things like the lugano, uh,

34:50

assessment criteria, which is what we use

34:52

for clinical trial assessment of, um, lymphomas,

34:55

we're always measuring into axises for, uh, for lymph nodes.

34:59

So, um, I would list the longest axis first

35:03

and then the short axis.

35:04

Um, you know, and these are taken perpendicular on

35:06

the axial plane.

35:08

So again, if you list three measurements, um,

35:10

which is like very thorough, um, you kind

35:14

of are losing some information here, right?

35:16

It can be confusing. And again, non-contributory.

35:18

So this isn't just specific to pet,

35:20

but this is a cancer imaging point that I always like to try

35:23

and teach whenever I'm lecturing.

35:25

Um, so this is just for findings in isolation.

35:28

Um, when I am reporting a finding in comparison

35:32

to a prior finding, um, this is just personal style for me.

35:36

I like to, to lead with what's happening with it.

35:39

Um, I think, you know, a a lot

35:41

of times you could describe a whole finding

35:43

and then you can say when compared to the prior,

35:45

it's decreased in size or whatever,

35:47

but you can just kind of cut down on a lot of words.

35:49

If you really just lead with,

35:51

you know, what's happening with it?

35:52

Is it decreased? Is it increase?

35:54

Is there no significant change?

35:55

And then you kind of just follow with the same formula here.

35:58

So decrease in size of the now minimally fdg,

36:02

avid distal esophageal tumor, which extends over a length.

36:05

Again, this is giving the long axis of 1.5 centimeters

36:08

with an SUV max of 2.2, previously 5.5 centimeters

36:12

with an SUV max of 10.2.

36:14

So, you know, this is not the shortest sentence,

36:18

but I think it's the shortest way to really give all

36:20

of the information that's needed, right?

36:22

What's happening? It's decreasing, what does it look like?

36:25

Now it's minimally FDG, avid, what's the size in the SUV

36:29

and what was it previously?

36:30

So I think, you know, for me, this is the formula

36:33

that I like to use that really kind

36:35

of packs in the most information

36:37

and really the only pertinent information

36:39

and keeps it as short and as brief

36:41

and to the point as possible.

36:45

All right, some tips, um,

36:47

I know many people use PowerScribe,

36:48

but there's lots of different dictation softwares,

36:50

um, available.

36:52

But really kind of use the features that are available

36:55

to you to streamline your reports and decrease errors.

36:58

So, um, you know, I often find

37:01

that like many drug names will come up wrong, even,

37:04

you know, no matter how many times you train it.

37:07

Um, so sometimes I figure out

37:09

what it always is mis dictating

37:11

and I will auto correct drug names

37:13

or, you know, train words.

37:15

These are a couple that, you know, uh, PowerScribe at least

37:19

with my voice has had a hard time recognizing.

37:22

And so, um, you know, take the time

37:24

to actually do the training for any of these words

37:26

that keep being mis dictated

37:27

and that will help streamline your reports.

37:30

Um, one thing that I do per this is just a personal, um,

37:34

you know, stylistic thing is, uh, I change with an SUV max

37:39

of to, I use the auto correct feature to

37:42

actually put an equal sign in there.

37:44

And I like to do that because there's

37:45

so many numbers in these reports.

37:47

Um, this is the example from the last page of

37:50

where we had a, a comparison of a finding.

37:52

And you know, when you have, uh, measurements combined

37:56

with SUVs, I like to have the equals right next to the SUV

37:59

because I just think it makes the report a little

38:01

bit easier to navigate.

38:02

And when you're looking for SUVs, you can find them just,

38:06

you know, with these visual cues.

38:07

So, um, everybody has different styles

38:10

and, uh, different preferences.

38:12

This is just one that one that I like to use.

38:16

So moving on to the findings and impression.

38:19

Um, you know, this is really an opportunity

38:21

to provide a comprehensive read.

38:23

Um, the key to a good pet read is really reviewing all the

38:26

imaging leading up and having a pretest probability

38:29

or suspicion for a finding.

38:31

Um, you never ever wanna let a negative pet

38:34

or an unimpressive pet talk you out of a finding

38:36

that's been suspicious on other imaging.

38:39

Um, and this is really important for small findings

38:41

and pulmonary nodules,

38:42

but you know, as an example, if

38:44

by CT you have an eight millimeter sub solid pulmonary

38:47

nodule, it's been slowly growing.

38:50

Um, so increasing in size

38:52

and density, uh,

38:54

previously measuring five millimeters one year ago

38:56

and three millimeters two years ago, um, so you know,

39:00

you do your FDG PET CT and we see no appreciable uptake.

39:05

Um, so, you know, this nodule is very likely malignant.

39:08

Um, a lot of adenocarcinomas are on this spectrum of kind

39:13

of, they're not entirely solid

39:15

or they start out as ground glass, they become more solid

39:17

until they're entirely solid.

39:19

Um, but they can just have a very indolent growth pattern.

39:22

It can take years for these to declare themselves.

39:24

So this nodule is very likely malignant

39:27

and it may just be indolent based on the growth pattern.

39:30

And so we don't actually really expect

39:32

to see much uptake on, uh, on FDG pet, right?

39:35

Because these are not turning over at a high rate.

39:38

These are not metabolically aggressive.

39:41

So there's two we two ways

39:43

to read this kind of study, right?

39:44

Like you can say negative PET

39:46

or no evidence of FDG having malignancy,

39:49

but like that's not very helpful.

39:51

Um, you are giving the impression to the clinician

39:54

that there is nothing to worry about when you say things

39:56

like negative or no evidence of malignancy.

39:59

So an alternative way to read this,

40:01

and this is really reading the PET

40:03

and the ct, the multiple cts leading up to it, is

40:06

that you would say despite the lack of FDG uptake,

40:08

this nodule remains suspicious by CT morphology

40:11

and growth pattern and likely represents a minimally

40:13

invasive adenocarcinoma, right?

40:16

So this is more informative, more accurate.

40:18

This is helpful to the clinician.

40:20

It still conveys the concern

40:21

for malignancy and really leaves no question.

40:24

And, you know, aside from doing the right thing

40:27

for the patient and you know, making sure that the degree

40:29

of concern is conveyed, it's also important medical legally,

40:32

right, that we are kind

40:34

of giving accurate information and assessment.

40:36

So again, like I've said

40:38

before, we can't read these in isolation.

40:39

You really need to like look at everything

40:41

that's happened leading up.

40:43

And this can be a problem too,

40:44

especially if you work at a place like ours

40:46

where we're a referral center,

40:48

and sometimes you'll just, you'll get a pet ordered

40:50

and you open it up and there's no imaging, right?

40:52

There's no CT or none of the prior imaging

40:55

that has triggered the pet available to you.

40:58

And it's, it's really difficult.

40:59

You have to make a decision. You know,

41:00

do you feel comfortable reading that

41:02

or do you really need to go through all the steps to get,

41:04

um, the prior imaging made available to you so

41:07

that you can give a comprehensive and accurate read.

41:10

Um, so we have some mechanisms in place that try to,

41:13

you know, get us everything we need.

41:14

It's not perfect, but, um, you know, it's, it's kind

41:18

of important to do that and to,

41:19

and to not read these in isolation.

41:22

Um, and again, a note on staging.

41:24

If it's a staging exam, I generally try to provide all

41:27

of the important information needed

41:29

for them to be able to stage.

41:31

Um, but I don't give an actual, actual actual stage, um,

41:34

for the reasons mentioned before, right?

41:36

There may be findings

41:37

or disease that we're not aware of

41:39

that could impact the staging.

41:41

Like sometimes skin lesions pop up that are not apparent

41:44

by imaging, and that would obviously change the stage brain

41:46

mets, um, et cetera.

41:49

But whenever you're reading a staging exam,

41:51

you should have open the TNM staging system for that disease

41:54

and know about, you know, the information

41:56

that affects T stage, nodal involvement, metastatic disease,

42:00

lymphoma, um, you know, knowing

42:04

what things might upstage patients

42:06

and being able to include that in your reports.

42:09

Um, so pulmonary nodules, I'll just give a note on this

42:12

because this is a big part of, uh, PET indications.

42:16

Um, so there can be multiple scenarios

42:19

for which a pet CT is ordered in the setting

42:21

of a pulmonary nodule, you wanna kind of try

42:23

to figure out which one you're in prior to reading

42:25

and answer the appropriate question, right?

42:28

So sometimes a nodule hass been identified

42:30

and what they're looking to do is actually

42:32

characterize the nodule.

42:34

Um, you know, you wanna talk about things like morphology.

42:37

If you have priors, you wanna talk about growth

42:39

and density changes over time.

42:42

Um, you know, if the nodule is like very FDG avid,

42:45

you're gonna probably be thinking more about malignancy.

42:48

If there's no avidity in it

42:50

and it, you know, looked low density, um, you know,

42:54

it might be an area of like mucus plugging

42:57

or if it had actually fat in calcification in it,

42:59

you might be thinking about a hematoma.

43:02

Um, but sometimes, you know,

43:04

the nodule is already suspicious based on ct, right?

43:07

The example I gave on the previous slide, we know

43:09

that it's growing, we know that it's increasing in density.

43:13

Um, you know, or it's like clearly speculated

43:16

and eating into an adjacent rib.

43:18

Um, you know, the pet is really done to see kind

43:21

of the metabolic behavior and to stage it right?

43:23

Like which nodes are involved

43:25

and is, are there, is there evidence of distant metastases?

43:29

Um, you know, and that's important for management, right?

43:31

They wanna know like, should we sample this percutaneously?

43:35

Um, you know, should this be done by ir

43:37

or is this something that can be done

43:39

by interventional pulmonology?

43:40

And we can sample if there's abnormal nodes

43:43

that should be sampled, we should, you know, try to combine

43:45

that procedure so that it can be done at the same time.

43:48

Um, you know,

43:50

sometimes malignancy is already known sometimes by the pet,

43:53

the time the pet is done, there's already been a biopsy.

43:55

And so in this case, you don't really need

43:57

to talk about the growth and the density changes over time.

44:01

You don't really need to prove your suspicion about the

44:04

nodule if it's already been characterized.

44:06

So, you know, an example

44:07

of this is like if it's already been biopsied,

44:09

I'll say intense FDG uptake is seen in the biopsy proven

44:13

right upper lobe squamous cell carcinoma, you know,

44:15

that measures this with an sev v max of this.

44:18

Um, but when you're characterizing a nodule,

44:21

you wanna spend a little more time, right?

44:23

So kind of figure out which scenario you're in

44:25

and that will tailor your report

44:27

so you're not wasting time talking about things

44:29

that don't matter and

44:30

that you're actually actually giving the

44:31

information that they're looking for.

44:33

Um, if a biopsy is needed or planned, be really specific.

44:36

Okay? You wanna talk about how close are we

44:39

to the central bronchi

44:40

or, you know, bronchovascular structures, um,

44:43

because that's going to give them information about

44:45

how they should go about doing the biopsy.

44:48

Um, you know, for pulmonary nodules, obviously things

44:50

that are more central are gonna be amenable to, um,

44:54

endobronchial approach.

44:55

And I'm actually surprised, you know,

44:57

every month I feel like I come across a case

44:59

that I thought was too peripheral

45:00

for interventional pulmonary pulmonology to reach

45:03

and they are able to do it.

45:05

So they're actually able to get, um, pretty far away,

45:08

but certain locations are a little bit more difficult

45:10

for them, like the upper lobes

45:12

because there's a, a bit of a more acute angulation

45:14

to get into the upper lobe bronchus.

45:16

So, um, give them information

45:18

'cause that's helpful for them to plan their biopsies also,

45:22

um, I personally will provide series

45:24

and images, image numbers from, um, the diagnostic CT

45:28

for my IR colleagues.

45:30

Um, it's especially important if there's multiple nodules.

45:33

We often see these patients with just, you know,

45:35

multiple synchronous primary adenocarcinomas.

45:38

Um, and so what I'll say is

45:41

after I describe a nodule, I'll say this corresponds

45:43

with the nodules seen on series three,

45:45

image 1 45 from the CT chest of whatever date.

45:48

Um, just it is helpful

45:50

for them when they're approaching the time of the biopsy

45:53

to know exactly what nodule we're talking about, um, so

45:56

that the wrong nodule doesn't get, uh, biopsied

45:59

or, you know, if perhaps it goes away, um,

46:02

because it was something that was infectious

46:03

or inflammatory, it's really helpful for them

46:05

to know exactly what we're talking about.

46:09

So finally, the impression, right?

46:11

This is like we spend all that time talking about the rest

46:14

of the report, but this is really often the most important

46:17

part of what we're providing to the clinician.

46:20

So if it's a fixed fishing exhibition, they're looking

46:22

for malignancy or inflammation based on the symptoms, um,

46:26

you know, your impression should be something.

46:28

If we don't see anything, we can say there's no evidence

46:31

of FDG AVID malignancy.

46:33

Sometimes I'll add additional information,

46:35

like if they're looking for something

46:36

that might be in the urinary tract, um, you know,

46:39

that's not something

46:40

that FDG PET is good at looking at, right?

46:44

We have all of the, uh, the activity

46:47

that's being excreted within the, um, within the urine.

46:50

And so that can really obscure lesions

46:52

that are in the ureter or the proximal collecting system

46:55

or, um, in the bladder itself.

46:58

So if you know that's the case, I might say no evidence

47:01

of fd GA malignancy,

47:03

but, you know, suboptimal evaluation of the urinary tract,

47:07

uh, you know, due to excreted tracer or something like that.

47:10

So you also want to provide any

47:11

limitations that might be there.

47:13

Um, let's say it's positive, you might have, uh,

47:16

an impression like this, fdg, a thickening

47:18

of the ascending colon is highly suspicious

47:20

for a primary malignant neoplasm such as adenocarcinoma.

47:24

And if you are ever suspecting

47:25

or giving a read that's highly suspicious for cancer,

47:28

you also kind of need to address the t,

47:30

the N and the M, right?

47:31

So we've kind of talked a little bit about t we've probably

47:34

given a measurement in the report,

47:36

but we also wanna talk about nodes

47:38

and metastatic disease, right?

47:39

Because that's what our job is, is to stage that.

47:41

So in the same sentence I'll say, you know,

47:44

or in the same impression point, I'll say no fdg,

47:46

avid regional lymphadenopathy

47:48

or evidence of distant metastatic disease.

47:50

So these are just some examples.

47:52

Um, if we're characterizing a finding seen on other imaging.

47:55

So here's a couple examples.

47:57

No evidence of FDG AVID disease,

47:59

specifically the previously described right liver lesion is

48:02

not fdg avid and favored to represent hemangioma, right?

48:05

You're giving 'em all the information.

48:07

You say there's no FDG uptaken it.

48:09

And in fact, when I combine this with the features

48:12

that we saw on the prior imaging, this is likely a heman.

48:16

Um, or you could have a positive one here.

48:18

The previously described enlarging retroperitoneal lymph

48:21

node is moderately FDG avid

48:22

and highly suspicious for recurrence.

48:25

Um, if the diagnosis is suspected

48:28

and they're looking for a biopsy site, an example,

48:31

what you might say is, you know,

48:32

intensely FDG added lymphadenopathy above

48:35

and below the diaphragm, most likely representing

48:37

lymphoma, right?

48:38

We could kind of stop there. We've given a complete report.

48:41

We, we've just, we've described all of the lymphadenopathy,

48:44

we think there's a lymphoma.

48:46

But if we know that they're looking for a biopsy site,

48:48

what we can also say is if tissue sampling is desired,

48:52

left inguinal lymphadenopathy is percutaneously

48:54

accessible and representative.

48:57

Um, you know, sometimes in lymphoma we have really

48:59

heterogeneous disease where we, you know,

49:01

especially in like the setting of A CLL that's transformed

49:04

or something like that, um, you want to make sure

49:07

that they're going to be biopsying something

49:09

that's representative of the worst

49:11

and most FDG AVID disease, you don't want

49:13

to be directing them to biopsy something that's not very,

49:16

even though it's enlarged.

49:18

If it's not, you know, one of the most FD AVID findings,

49:21

then if they biopsy that they, that may not capture the, um,

49:25

the malignant transformation or degeneration.

49:29

Um, so if a diagnosis is, is known

49:31

and we're looking to identify a primary

49:34

or to initially stage,

49:35

we can say things like findings consistent

49:37

with metastatic neuroendocrine tumor.

49:39

We know that, right? With a primary lesion identified in the

49:42

right lower quadrant ilia ileum with metastatic nodal

49:46

and liver metastases, um,

49:49

or you know, something like intensely fdg avid, right?

49:52

Cervical lymphadenopathy consistent

49:53

with a biopsy proven metastatic disease.

49:55

There's no appreciable FDG avenue postal scalp

49:59

or salivary gland to identify, um,

50:01

the primary side of malignancy.

50:03

Sometimes we can't find it, right? That's never satisfying.

50:06

Um, so here's just a few more examples.

50:09

Restaging assessing treatment response.

50:11

So, uh, this is the one I love to give the most,

50:13

is saying excellent

50:14

and complete treatment response with resolution

50:17

of previously seen thoracic lymphadenopathy doil one doil

50:20

iss like a, um, staging system that we use in assessing, uh,

50:24

lymphoma, avidity and response.

50:27

But, um, you want to tell them what their question is,

50:30

you know, is my treatment working yes or no?

50:33

And how well has it worked?

50:35

Is everything gone or is there still some disease?

50:37

So using words like complete treatment response

50:40

or partial treatment response will give them the

50:43

information that they're looking for.

50:44

So the second example being partial,

50:46

but incomplete treatment response as evidenced

50:48

by mild improvement

50:50

and FDG uptake in the right liver lesion.

50:52

So you're telling them like,

50:54

it's improved, but it's not gone.

50:56

There's still disease there, there's still work to be done.

50:59

Um, or you could say something like mild residual FDG uptake

51:02

in the previously radiated cervical mass

51:05

is indeterminate, right?

51:06

It could represent residual

51:07

or responding disease,

51:09

recommend a short-term follow-up PET ct.

51:12

Um, so right, those are all different,

51:14

very different answers in how we restage

51:16

and assess treatment response.

51:18

Um, if somebody's doing surveillance, we can say, you know,

51:21

small but mildly.

51:23

FDG added mesenteric lymph node in the location

51:25

of original involvement raises the possibility of relapse.

51:29

Consider tissue sampling as clinically indicated.

51:32

Um, an example of following up a finding from the prior pet,

51:36

you know, the previous area

51:37

of residual FDG uptake in the radiated cervical mass has

51:40

resolved and likely represented responding disease

51:43

slash post-treatment change.

51:45

Um, or the converse of that would be the previous area

51:48

has increased an extent in FDG avidity

51:50

and is highly suspicious for recurrent disease.

51:53

Um, so yeah, that's, uh, those are some examples of,

51:58

you know, the questions that might be asked

52:00

and how we can specifically answer those.

52:02

And so, you know, just looking over the last two slides,

52:05

like these are all very different answers,

52:07

providing very different and specific information,

52:10

and I encourage you to try to figure out as best you can,

52:13

what the question is so that you can answer it

52:15

and give all of the information

52:17

that's needed for the clinician.

52:19

Um, another thing I like

52:21

to do is very be be very specific about the differential.

52:25

Um, you know, I really love this graphic.

52:28

The, uh, source is here,

52:29

but these are pulmonary nodules on the ground

52:31

glass to solid spectrum.

52:33

And so, um, depending on how much solid tissue you have,

52:36

kind of directs you into this more invasive category.

52:39

So, you know, I like to be specific about

52:42

what I think something is when I can be,

52:45

but you know, sometimes you can't.

52:46

So, um, that's just kind of a tip

52:49

that's helpful to clinicians.

52:50

And then be really specific about your

52:52

follow-up recommendations.

52:53

Um, you know, if you're gonna recommend another study,

52:57

be done, recommend exactly what you want,

52:59

and sometimes you can give options, right?

53:01

You can say it could be a CT or it could be an mr,

53:03

but be specific about if you want contrast with that or not,

53:06

or if you want a specialized protocol for it.

53:09

Um, and try to be specific about when,

53:11

and you can give ranges if you're not really, you know, if,

53:14

if you wanna leave it up to the clinician to kind

53:16

of use their discretion

53:18

or the degree of clinical suspicion to decide,

53:21

but you could say, you know, recommend a follow-up CT from,

53:24

you know, in three to six months or something like that.

53:27

Uh, and just be conscious about using words like recommend

53:29

versus consider when you say things like recommend,

53:32

you're kind of telling the

53:34

clinician that they need to do it.

53:35

Um, versus when you say things like,

53:38

consider you're giving them an option

53:39

and they're, you're giving them some leeway

53:41

to use their clinical judgment if they want

53:43

to wait on something or um, kind

53:46

of clinically follow it instead of followed by imaging.

53:50

So that's it. That was a lot of information

53:51

and not a lot of pictures.

53:53

So, um, apologize, hopefully you're still here with me.

53:57

Um, I've got some questions

53:58

and answers that I'll try to address.

54:01

Um, let's see.

54:04

Is there an SUV value that could be used to distinguish

54:07

between post-radiation osteonecrosis versus local regional

54:11

residual disease recurrence if imaging performed

54:14

before three to three months or 12 weeks?

54:17

I think post radiotherapy.

54:19

Um, so my answer to this question is almost always no,

54:23

there's never an SUV cutoff that, um, you know,

54:27

will help you answer a question like that.

54:30

Um, it's really for me more of like a visual interpretation.

54:35

Um, and sometimes a lot

54:37

of times I think actually we can't use, uh,

54:41

or we can't really come down in these cases

54:43

of like post-radiation.

54:45

Um, and I often will give a read

54:47

that says this could represent either or,

54:49

and I recommend a short-term follow-up PET CT

54:51

because I think that that, um,

54:53

sometimes we just need more time to sort out a finding, um,

54:57

okay, in post radiation scenario, rectal cancer

55:01

response assessment, which is better MRI or pet.

55:04

Um, so that is an interesting question

55:07

and a lot of times I think they're actually used together.

55:10

Um, I, you know, I think that

55:14

MRI and PET will go together nicely to give you kind

55:18

of the anatomy, right?

55:19

Because we don't get much anatomy detail with pet.

55:22

Um, because oftentimes we're using a non-contrast

55:25

or sometimes a contrast ct,

55:26

but we all know that contrast MR is, um,

55:30

really superior to either of those.

55:32

So, um, I think pet,

55:34

I think MRI is often done in the first instance

55:37

to see if there's anything, um, you know, questionable.

55:40

And then if there is a finding that's just residual disease,

55:44

uh, you know, PET can be done

55:46

after that to kind of work it out.

55:48

But, um, I, I think that the,

55:50

the best scenario is using them together.

55:53

I think stepwise we do MR first

55:55

and then PET to troubleshoot that,

55:57

but I think PET can actually be a little bit

55:59

more definitive, right?

56:01

If it, if it's negative.

56:02

If it's negative, then we feel really good about it.

56:05

Um, if it's positive, we kind of don't know if we're in

56:07

that scenario post-treatment change, um,

56:09

versus residual disease

56:11

and we might need kind of more imaging.

56:14

Um, okay. Let's see.

56:18

Why is comment of liver SUV needed

56:21

as part of technique in the report?

56:23

So we kind of touched on this

56:24

before, it's really just more for quality control

56:27

and in terms of, you know, making sure

56:30

that our bio distribution is good

56:32

and that the patient had adequate, um, you know, fasting

56:35

and that we have like a good quality of report.

56:38

And then as I mentioned, we do use it in interpretation for,

56:42

um, doil scoring and the assessment of lymphoma.

56:45

Um, but I think for the limitations that we also discussed,

56:48

it's not, you know, as big of a part

56:50

of interpretation as it used to be.

56:53

Um, okay.

56:55

Do you measure a lesion on a pet image if it's

56:57

ill-defined on ct?

56:59

That's a really good question.

57:01

So sometimes the answer is yes.

57:03

If I'm reading a pet

57:04

that there's been diagnostic imaging done in the past,

57:07

you know, month or two months, um,

57:09

for instance like a pulmonary mass

57:11

or a pulmonary nodule, I know that

57:14

because of technique that the uh, measurements

57:17

that are taken on the diagnostic CT are going

57:20

to be significantly more reliable than what's on my

57:23

attenuation correction ct.

57:25

And so if I'm providing a measurement,

57:27

I will use the one from the diagnostic.

57:29

But there are lots of cases

57:31

where we either don't have diagnostic imaging, um, available

57:35

to us or not within the right timeframe

57:37

or the lesion has changed.

57:39

Or a really good example

57:41

of this is when you're reading a post-radiation change

57:44

and there's a recurrence

57:45

and by CT you cannot tell where the tumor is.

57:48

Um, so in those cases where it's very ill-defined by ct,

57:52

I will measure on the pet.

57:53

But one strategy I use is I really back off, um,

57:57

of the avidity and turn down the window level so

58:00

that you're not getting a blooming artifact where, you know,

58:03

if something's very, very avid,

58:04

it will sometimes appear bigger than it actually is.

58:07

But when you back off the window

58:08

and kind of open up the, the level a little bit,

58:11

at some point the lesion will stop getting smaller

58:14

and it'll just start getting kind of less avid.

58:17

And that's where you kind of know what the true size

58:19

of your, um, of your finding is.

58:21

I find that really actually important

58:23

and helpful with dotatate imaging

58:24

because those are often so avid that we open up the study

58:28

and we say, oh my gosh, there's this like two centimeter

58:30

tumor, how do we not see it on ct?

58:32

But then when you back off the avidity you're like, oh,

58:34

it's actually only like, you know, 0.9 centimeters.

58:37

It's a very small tumor.

58:38

It's just the, it's so avid

58:40

that it looks like it's very big.

58:42

So yes, sometimes I do measure size on the pet,

58:45

but I also make sure that I'm not over measuring

58:49

by manipulating the window for that.

58:52

Um, how do you divide uptake of FDG?

58:56

Minimal, mild intense. Is there a formula?

58:59

So that's a great question too.

59:00

Um, I'll use what I have here on the screen right now

59:03

to to kind of show you.

59:05

So like, um, and I wish this was in black and white

59:08

'cause that's how we actually read, right?

59:09

The colors just for show.

59:11

But um, you know, something that's like intensely FDG avid,

59:15

it should really be the most intense thing on the scan.

59:17

It should really be kind of in line with

59:19

what we see in the bladder and the collecting system.

59:21

So like all of these findings in the lung I would

59:23

characterize as, um, intense when things are kind

59:27

of less intense than that they're still, you know,

59:30

like significantly greater than, you know, say liver

59:34

or they're, you know, very noticeable,

59:36

but they're not quite as like avid as collecting system

59:39

or you know, what we're seeing here in the lung.

59:41

I would give that kind of like a moderate, um, you know,

59:45

maybe kind of this degree of uptake that we're seeing here.

59:48

And then mild is sort of, kind of, it's not negative,

59:52

but it's not very impressive.

59:54

And you know, maybe

59:55

what we're seeing in the liver here I would

59:57

characterize as mild.

59:59

And then, you know, this, um, stuff

60:01

that we're seeing in the GI tract, which is like,

60:03

it's noticeable, right?

60:04

But it's not very impressive. This is probably minimal.

60:07

And then when I say barely perceptible, this is just kind

60:10

of a personal thing, that's where I have

60:12

to really crank the window to be able to see the finding.

60:15

And it's not negative,

60:16

but it's very, very like low degree of uptake.

60:20

Um, so it's, it's definitely a visual thing.

60:23

There's not a formula, there's not like an SUV cutoff,

60:25

but it's just kind of picking a scale and you know, using it

60:29

and being consistent with it.

60:32

Um, I think we've hit the one o'clock line.

60:35

I'm sorry that there are still a few questions here

60:37

that I didn't get to answer.

60:39

Um, I'll just do one more here.

60:42

Somebody asked how to report doil if adenopathy is present,

60:46

which may or may not be lymphoma related.

60:49

So, um, with the doil criteria, there's uh, you know,

60:53

five categories that we use

60:55

and then there's an x um, qualifier.

60:58

So if I think that a finding is not related to lymphoma,

61:01

but it's very ftg avid, for example, like thyroiditis

61:04

or something, um, you can give it a designation of ADO x,

61:07

which is what you're saying is this is very avid

61:10

and it's abnormal, but I don't think

61:11

it's related to lymphoma.

61:13

Um, you can use that for lymph nodes too if you think

61:16

that they're not related to lymphoma,

61:17

but you have to be very careful in attributing an FDG avid

61:21

lymph node to not being lymphoma in the case of, you know,

61:24

a patient with suspected or known lymphoma.

61:28

Um, oh, sorry, one more last one.

61:29

'cause it's important with PSMA, do you use SUV values

61:33

and, um, for the answers that we kind of like,

61:35

or for the reasons we talked about earlier in this,

61:37

in the um, slides?

61:39

No, because we don't really know, um, what they mean

61:42

outside of FDG.

61:44

Uh, so that's the short answer.

61:46

There's a longer answer, but that's the short answer.

61:49

Um, so I think that's, I think that's all we have time for,

61:53

but thank you all for your attention

61:55

and um, I hope

61:56

that you guys got something out of today's lecture.

61:59

Thank you so much for, uh, being here with us today, Dr.

62:02

Macintosh and sharing your expertise with us.

62:04

We really appreciate it.

62:06

And, uh, thank you to all, uh,

62:08

that participated in today's noon conference.

62:11

You can access the recording of today's conference

62:14

and all our previous noon conferences

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by creating a free MRI online account.

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Be sure to join us next week on Thursday,

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January 25th at 12:00 PM Eastern

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for a live noon conference featuring Dr.

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Jordana Phillips for a lecture entitled

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Contrast Enhanced Mammography Time for Implementation.

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You can register for this free lecture@mrionline.com

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and follow us on social media

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for updates on future noon conferences.

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Thanks again and have a great day.