Interactive Transcript
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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.
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