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PET Imaging of Dementia (FDG, Amyloid, Tau)

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When we use dementia imaging with PET, again, we mention there is amyloid

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PET, tau PET, and FDG, and obviously they have different appearances.

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The top row is normal, the bottom row is abnormal. An abnormal PET

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will show diffuse binding of the tracer throughout the cortex. Tau PET is

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not a diffuse, it's really you get tau deposition often in the temporal

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lobes, but it tends to deposit where you have areas of atrophy.

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In this patient here in the temporal lobes, and then this is an

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FDG PET, and there'll be a different pattern for the different types of

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dementia syndromes. This patient happens to have Alzheimer's and they have

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cortical hypometabolism here in the bilateral parietal lobes at a different

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level. You would also see in a temporal lobes, also in the posterior cingulate

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gyrus here. Now, with FDG PET, here's a look at FDG PET with

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different types of dementias with Alzheimer's. Again, we see the cortical

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hypometabolism in the bilateral parietal lobes with FDG,

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we were going to see it with frontotemporal dementia in the bilateral frontal

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lobes, as well as the temporal, and dementia with Lewy bodies can often

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have almost like an Alzheimer's type pattern, but plus occipital lobe.

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So here we see some hypometabolism in the parietal lobes. There's a little

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bit actually in the frontal lobes here. We would have probably seen some

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in the temporal and the occipital as well. And this is an amyloid

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case in a patient with Alzheimer's disease. Here's the amyloid PET CT fusion

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images. Here's the amyloid PET MR fusion. Again, diffuse binding of that

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amyloid tracer throughout the cortex tells us that this patient has Alzheimer's

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disease in most cases. Now, depending on the different imaging modalities,

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there's going to be a different pattern that you look for.

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So with MRI for Alzheimer's, you're going to look for atrophy in the

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temporal, parietal, and posterior cingulate gyri. Frontotemporal dementia,

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it's going to be temporal, frontal, and anterior cingulate gyri. Then with

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dementia with Lewy bodies, it's going to be occipital, and then also you

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can get some temporal, parietal, and posterior cingulate gyrus. Now, the

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pattern of hypometabolism that you see with FDG PET is the same as

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the pattern of atrophy that you see with MRI. So these are basically

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the exact same distribution as with MRI. Skipping down here to tau PET,

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again, for Alzheimer's disease and tau PET, it's going to match the same

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pattern that you see with MRI and FDG. So temporal, parietal, and posterior

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cingulate gyri, is where you'll get that tau deposition. The one that is

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different is the amyloid PET because again, that is a diffuse pattern and

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we use that for screening for Alzheimer's disease.

Report

Faculty

Suzie Bash, MD

Medical Director of Neuroradiology

San Fernando Valley Interventional Radiology & Imaging (SFI), RadNet

Tags

Syndromes

PET

Non-infectious Inflammatory

Neuroradiology

Neuro

MRI

Idiopathic

Brain

Acquired/Developmental

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