Positron emission tomography

So based off endocannabinoid receptors, CB1, CB2, CB2, The individual cannabinoids that are made in the body, like 2-AG and anandamide, you go, okay, so we have adaptation to this, and the body seems to tolerate these chemicals well because there's some adaptation to it.

And when you realize what it does on a mechanistic level, and this is based off PET data in particular… Cannabis actually seems to have neuromodulatory properties.

So you go, this works like a homeostasis agent.

It literally works within the system.

[piano interlude] So welcome to Life in Voxels, a scientific podcast about the people, technologies, and collaborations shaping the future of medical imaging.

We're happy to shoot our first pilot episode of this podcast, and we are very excited having with us, uh, two experts in PET instrumentation from Spain.

But first, let me introduce, uh, the host of the podcast.

I'm Nikolaos Karagatsanis, Associate Professor of Biomedical Engineering in the Department of Radiology at Weill Cornell Medical College, and I have the pleasure to co-host this, uh, episode t-together with George.

I am, uh, a Research Staff Associate in Weill Cornell Medicine.

[laughs]

Okay, so for our first pilot episode, we will be exploring a very fundamental question in imaging science: How does a PET scanner progress from an initial concept, an idea, to an actual functioning prototype? And for that, uh, the title of our first episode will be From Conceptualization to Prototyping in PET Instrumentation.

We're joined by two guests who are directly involved into this process.

And I'm going to continue on the subject of cardiac amyloidosis with two additional studies that were published in JAMA in conjunction with ESC.

The first is titled Iodine-124 Evusamatide Positron Emission Tomography, Computed Tomography for Diagnosing Cardiac Amyloidosis.

And this study, a non-randomized clinical trial, looked at a new cardiac imaging approach for the diagnosis of cardiac amyloidosis.

Traditionally, technetium pyrophosphate scanning has been used in the diagnosis of cardiac amyloidosis.

Yeah.

And in the PET world, again, in imaging, which is, you know, very promising, they are developing, um, some new ligands.

Ligands are, um, things that bind to cells.

Um, so in PET, which I don't know if any listeners have gone in for a PET CT or a PET test, um, they will inject you with something that's radioactive, and whatever it binds to shows up.

It's like on a camera image.

It's detected.

So what's really cool with the microglial inflammation is that they're developing some new PET ligands.

That's what they call the compound that they would inject.

Yes.

And the abnormal dopamine release that you visualize on the PET scan coincides directly with the impaired salience networks that are flickering away on the fMRI.

And the glutamate abnormalities that we measure with spectroscopy correspond perfectly with dysfunctional hippocampal circuits.

Right.

Exactly.

They annihilate each other and emit two gamma rays in exactly opposite directions.

The PET scanner is essentially a ring of detectors that captures these simultaneous gamma rays.

which allows the computer to map the precise spatial location of where the tracer is binding to the D2 receptors.

Why did we move away from PT? And what makes fMRI the preferred instrument in this hall of living minds?

Well, the shift was largely driven by three things, safety, resolution, and practicality.

I mean, PETE scanning was revolutionary back in the 1980s.

It was

a huge deal at the time.

That's the main issue.

Because it relies on ionizing radiation, there is a very strict limit on how many times you can scan a single person.

You just cannot ethically put a patient in a PETE scanner repeatedly for longitudinal studies.

So with that in mind, we'll get started.

Again, if you're in the right place, this is the Should I Order a PET Scan? Integrating Molecular Imaging into Urologic Oncology Clinical Practice, Current Approaches and Future Opportunities.

Do we have to push a little bit on this to get it to move forward? Maybe I'll try this other one.

There we go.

Course objectives are here.

I won't read them out to you, but essentially we'll be covering molecular imaging in terms of PET scans in four different urologic oncology malignancies.

Often this is the algorithm that has been historically provided and how we stage different cancers, you can see.

Typically, local imaging, distant imaging, and bone scans have been used for initial staging.

So let's, um, delve a little bit more into the cerebral, uh, fluid AT biomarkers.

So what are the two major gold standards? One is the amyloid PETs, and the other is the CSF biomarker measurements.

So what are the advantages of each of them? The amyloid PET can visualize the plaque-associated A- ABeta fibers, so those are the insoluble plaques there have accumulated in the brain.

The advantage is that it can give you a load and distribution of amyloid.

Sometimes for patients, if you explain, "This is gonna allow us to rule out a lot of potential other things that we're worried about," and this is the best test for us to look into multiple analytes, provide more accurate diagnosis, and rule out important conditions.

I think it's very important to emphasize for us cognitive neurologists or all clinicians, we cannot stand only one test.

You have to look into the history, a detailed history, cognitive exam, um, brain imaging, and look as the molecular data with CSF or blood or PETs as an additional piece of information that you can integrate into the whole clinical picture of patients for the best diagnosis.

So what happens in CSF biomarker results? So you have low Abeta42 and Abeta42/40, so the ratio is low.

So in a very real sense, what's going on in the gut is absolutely going on in the brain as well.

And then can you talk about what they've shown in people that have insulin resistance and changes in this activity on PET imaging?

Well, absolutely.

What, what has been demonstrated, uh, a couple of things really exciting.