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 First AD patient with PIB scans 
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Joined: Fri Aug 11, 2006 1:46 pm
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Location: SF Bay Area (Northern CA)
Post First AD patient with PIB scans
Those of you interested in advances in imaging for neurodegenerative disorders and the correlations between imaging studies (while a patient is alive) and brain pathology (seen on post-mortem autopsy) will LOVE this news. Since LBD typically co-occurs with Alzheimer's Disease, this exciting research about PIB also applies to the LBD community.

The PET is a type of brain scan. Currently, nearly all PET scans employ FDG, which picks up on glucose in the brain. For the last several years, the latest in PET scans for Alzheimer's or other dementia patients employs PIB, Pittsburgh Compound B. PIB picks up on amyloid plaques. (The dye is retained by the insoluble amyloid protein.) Alzheimer's disease is a disorder of two proteins -- amyloid (which forms plaques) and tau (which forms tangles).

Hopefully, one day, we'll have PET scans that can detect alpha-synculein (which would help diagnose LBD and PD).

The Alzheimer Research Forum has a (mostly-understandable) summary of a recently published article in the December 13th issue of the journal Brain about a woman with Alzheimer's Disease who "volunteered for the first PET-PIB scan ever performed. She received another PIB scan two years later, and over the course of her disease also got an MRI and three PET scans using fluorodeoxyglucose (FDG), a marker for glucose use and therefore brain metabolism." The woman died at the age of 61. She donated her brain for autopsy.

"Over the eight years she was studied, the woman’s score on the Mini-Mental State Examination declined from a near-normal score of 27 down to five. The FDG data showed that her brain’s glucose metabolism decreased in parallel with her cognitive powers. By contrast, PIB retention, already high at first examination, showed little change over two years during which her cognition declined steeply. The amount of amyloid deposition seen at autopsy three years later also looked similar to PIB estimates...suggesting no further change in amyloid between the second PIB scan and death three years later. This pattern matches the data from numerous previous studies, in which PIB retention increases during mild cognitive impairment, then seems to plateau during AD."

"Autopsy results confirmed the patient’s diagnosis of pure AD. ... The results confirmed that in vivo PIB retention correlates quite well with amyloid deposits, but does not correlate closely with tau and neurofibrillary tangles, as previous studies have found. ... In addition, the authors performed detailed studies not done before and turned up intriguing correlations between amyloid accumulation and synaptic receptor density, as well as a surprising lack of correlation with markers of inflammation."

The summary on the Alzheimer Research Forum discusses four clinical trials with compounds targeting amyloid in Alzheimer's patients. The trials were all negative. This PET-PIB study gives additional insight as to why that may be the case.

Here's the summary on ARF about the recently-published study:
http://www.alzforum.org/new/detail.asp?id=2653

Note that some of the comments are well worth reading, though harder to understand than the summary. Some of the comments (posted in 2004) give historical info on PIB.

The recently-published study is available at no charge through the journal Brain. See:
http://brain.oxfordjournals.org/content/134/1/301.long (for HTML version)


Mon Jan 03, 2011 2:23 am
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Joined: Mon Dec 27, 2010 11:34 am
Posts: 67
Location: North Carolina
Post Re: First AD patient with PIB scans
I have wondered about the seemingly scarceness of PET scans. I conducted some research a few weeks ago and PETs seem to be used at a few research hospitals. Are they expensive and new? If these scans difinitively evidence plaques, why are they not used to difinitively dx? Now, off to research glucose metabolism- thanks! Perhaps I should begin my online science degree.

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Katie (36) daughter of Marcia (70)


Mon Jan 03, 2011 9:02 am
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Joined: Mon Dec 27, 2010 11:34 am
Posts: 67
Location: North Carolina
Post Re: First AD patient with PIB scans
I have wondered about the seemingly scarceness of PET scans. I conducted some research a few weeks ago and PETs seem to be used at a few research hospitals. Are they expensive and new? If these scans difinitively evidence plaques, why are they not used to difinitively dx? Now, off to research glucose metabolism- thanks! Perhaps I should begin my online science degree.

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Katie (36) daughter of Marcia (70)


Mon Jan 03, 2011 9:02 am
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Joined: Wed Dec 30, 2009 1:46 pm
Posts: 3213
Location: WA
Post Re: First AD patient with PIB scans
Robin, do they know whether the decreased glucose metabolism is a result of the pathology or vice versa? Interesting that it correlates better than with measurable cognitive changes than does the plaque formation.

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Pat [68] married to Derek [84] for 38 years; husband dx PDD/LBD 2005, probably began 2002 or earlier; late stage and in a SNF as of January 2011. Hospitalized 11/2/2013 and discharged to home Hospice. Passed away at home on 11/9/2013.


Mon Jan 03, 2011 11:16 am
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Joined: Fri Aug 11, 2006 1:46 pm
Posts: 4811
Location: SF Bay Area (Northern CA)
Post Re: First AD patient with PIB scans
Katie,

PET scans aren't new. The scans are very expensive, and few insurance companies pay for them. So, PET scans are, as you say, normally only available at major medical universities and only for those participating in research.

A PET-PIB scan cannot be used to definitively diagnose DLB or PDD.

A special kind of SPECT scan (one that looks at dopamine uptake in the basal ganglia) is very helpful in diagnosing DLB, PDD, and PD....but still not definitive. Because of patent issues, SPECT is not as widely available in the US as it is in Europe. It's available in a few major medical universities in the US. Perhaps if insurance companies start paying for DAT SPECTs for parkinsonism cases, we'll see greater use of this type of scan in the US.

I think there is also a PET scan that looks at dopamine uptake. That's the extent of my knowledge on that type of PET!

As you may know, a confirmed diagnosis is only possible upon brain autopsy.

Robin


Mon Jan 03, 2011 1:39 pm
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Joined: Fri Aug 11, 2006 1:46 pm
Posts: 4811
Location: SF Bay Area (Northern CA)
Post Re: First AD patient with PIB scans
Pat,

I don't think the decrease in brain metabolism is thought to be a cause of the pathology but rather it's thought to be due to changes in the brain (perhaps from decreased neurotransmitter levels or neurotransmitter dysfunction).

It would seem that FDG-PET can only confirm the presence of dementia but that PIB can at least pin-point whether amyloid is present or not.

Robin


Mon Jan 03, 2011 4:01 pm
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