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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 right now and the

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shutting down of in person events, we have decided to provide free Noon

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Conferences for radiologists all around the world. Today we are joined for

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a noon conference by Dr. Elcin Zan. She is a radiologist who specializes

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in neuroradiology and nuclear medicine with a focus on theranostics, combining

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imaging and therapy. A reminder that there will be a Q&A session at

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the end of the lecture, so please use the Q&A feature to ask

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your questions and we will get to as many as we can before

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our time is up. That being said, thank you all for joining us

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today. Dr. Zan, I'll let you take it from here. Well, good afternoon, good

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morning or good evening, wherever you are. Thank you very much for joining

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us. I will be talking about molecular PET in head and neck oncology. Those

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are my disclosures but nothing relevant to the topic we will discuss here.

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We will talk about the major differences between molecular PET and radiology,

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and we will see the proven value of FDG PET in head and neck oncology and

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the pending value of DOTA TATE PET in head and neck oncology. Instead

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of providing you the sensitivity and specificity analyses from the literatures,

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I will be very practical and I will share you cases.

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All of them are my own cases from NYU,

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the institution that I work right now, because I want to show the

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real value of how practical the molecular PET could be in the real

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world, except the last case and we will see. So I'm going to

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stop my video so that we can all focus on the images. Let's

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start with the differences. What's the biggest difference between anatomic

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versus PET imaging? That's the basic question between radiology and molecular

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nuclear medicine practices. In radiology, as we can see here, we have an

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external source, whether it's a CT or MRI, and it is an organ based

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imaging, whether you scan the brain, head, or neck, or part of the

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body, it's organ based. So the biggest amount of data that you can

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collect is going to give you the information about the local,

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T, and nodal, and staging. As opposed to PET, it's an emission scan. We

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inject a small amount of, a minor amount of radiopharmaceutical, and then

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the body becomes the source of our signal, the body becomes the

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signal emitter, and the PET scanner collects the signal from the patient's

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body. That is a product of the inherent physiologic or pathologic states.

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So the difference is, again, anatomic, organ based,

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and it's a transmission scan, because we are an external source, as opposed

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to PET's molecular, it's a functional imaging, because we inject the patient,

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and then after a while, we image the patient as a whole,

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the entire body, to see the physiologic as well as the pathologic processes.

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And one of the fundamental differences aside from the techniques or technical

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equipment that we use is the PET tracers versus the gadolinium, because

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in CT or MRI, we use contrast, and mostly in... The example shown

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here is a blood vessel that shows how the contrast

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enhancement happens, as opposed to the PET, molecular PET, radiopharmaceuticals

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and the molecules at the top. So let's focus on

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the gadolinium first on MRs, which the same applies to the iodine. You

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do have either increased number of vessels within the

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mass or wherever the disease is, and this increased number of vessels are

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not healthy vessels. They are leaky, as you can see here,

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and they let either the iodine or the gadolinium to leak through the

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vessels, and that creates your enhancement and the recognition of the mass

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or lesions. And this is a very passive process. There is nothing specific

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to the type of the disease. Everything can enhance right. As opposed to

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the PET, it is as specific as we can get.

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The most commonly used radiopharmaceutical is FDG, as you can see.

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It's a GLUT transporter specific evaluation of the diseases, and the second

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most commonly clinically used tracer, we are talking about head and neck

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again, is DOTA TATE PET, and that is not specific but highly selective

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to somatostatin receptor type 2, and both are localized at the cell membrane.

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When a patient receives the radiopharmaceutical, as you can see here,

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after they are transferred into the interstitial space, their interaction

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with the disease states is through transporters or receptors, which is

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highly selective and more specific compared to gadolinium. It's not a passive

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evaluation of what is going on in the patient's body, but it's a more

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active evaluation of what functionally is going on in the patient's body.

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And once again, tracer uptake is not equal to enhancement. After that,

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this is the laundry list of PET tracers that we use,

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either for clinic or for research purposes, but I will show you the

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proven value of glucose analog, which is the FDG PET, more commonly known,

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as well as the DOTA TATE PET. That is a receptor,

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as you can see here, DOTA TATE peptide receptor imaging.

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I just want to put the name here so that we all

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become familiar. I think that is what the feature lies in

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some certain disease states, but not well proven for the head and neck yet.

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As much as FDG and all other imaging tracers that we have so

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far are focusing on the cells, specifically the cancer cells, this tracer,

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namely FAPI, the fibroblast activation protein inhibitor, is focusing on

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the tumor microenvironment. And now we know that

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tumor microenvironment is one of the major drivers of

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treatment response or developing treatment resistance to certain immunotherapy

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agents. So why do we care? Because why do we want to have

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more and more data? Wouldn't the head and neck CT or MR be enough

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for providing the patient the appropriate prognostic stage group, right?

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The only way we can acquire this complementary evaluation after primary

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and nodal disease evaluation by the CT or MRI is PET CT. We

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need PET CT.