Novel PET Scans Could Improve Alzheimer's Assessment

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Main Category: Alzheimer's / Dementia
Also Included In: Medical Devices / Diagnostics;  Radiology / Nuclear Medicine
Article Date: 13 Aug 2008 - 0:00 PDT

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Positron emission tomography (PET) scanning may allow non-invasive assessment of the formation of Alzheimer's disease-related plaques in the brain, according to a study released early online on August 11, 2008 in the Archives of Neurology, one of the JAMA/Archives journals.

Alzheimer's disease is degenerative neurological disease characterized by dementia. It usually effects older people, though a small subset of early-onset victims exists. β-amyloid and other plaques are often used as a basis for Alzheimer's disease diagnosis and assessment, according to the article. Presently, these aggregates are examined through analysis of brain tissue samples that are obtained during life or observed after death. According to the authors, this marks a "a major methodological obstacle considering clinical drug trials of early Alzheimer's disease," as this makes it very difficult to assess the progression of the disease.

Normal-pressure hydrocephalus, which is an increase in the levels of cerebrospinal fluid in the brain, shares some common symptoms with Alzheimer's disease, including cognitive impairment. Between 22% and 42% of patients with normal-pressure hydrocephalus symptoms also have the brain lesions that characterize Alzheimer's disease.

PET scanning is a medical imaging technique that measures the location of tracer molecules in a three dimensional picture. A non-invasive, relatively standard procedure, PET has enormous potential as an assessment method for Alzheimer's if the right tracer marker is used.

To investigate this option, Ville Leinonen, M.D., Ph.D., of the University of Kuopio, Finland, and colleagues examined 10 patients who did not have severe dementia but had undergone biopsy of the frontal cortex because they were suspected of having normal-pressure hydrocephalus. Of these, six were found to have samples with β-amyloid plaques, while four displayed no Alzheimer's related tissue. Carbon 11-labeled Pittsburgh Compound B ([¹¹C]PiB) was injected into each subject as a tracer before undergoing a 90 minute PET scan.

Those patients with β-amyloid plaques in their brain biopsies also displayed a higher update of [¹¹C]PiB in certain brain areas. In comparison, patients without Alzheimer's plaques did not show this result.

The authors indicate that this means PET using this marker could be a viable option for future diagnosis of Alzheimer's disease. "This study supports the use of [¹¹C]PiB PET in the evaluation of beta-amyloid deposition in, for example, mild cognitive impairment, Alzheimer's disease or normal-pressure hydrocephalus," they say. "Large and prospective studies are required to verify whether [¹¹C]PiB PET will become a tool in diagnosing Alzheimer's disease. Another potential use of [¹¹C]PiB would be the quantitative monitoring of beta-amyloid deposits in the brain in subjects under treatment in pharmaceutical trials of early Alzheimer's disease targeting amyloid accumulation."

Assessment of β-Amyloid in a Frontal Cortical Brain Biopsy Specimen and by Positron Emission Tomography With Carbon 11-Labeled Pittsburgh Compound B
Ville Leinonen, MD, PhD; Irina Alafuzoff, MD, PhD; Sargo Aalto, MSc; Timo Suotunen, BM; Sakari Savolainen, MD, PhD; Kjell Någren, PhD; Tero Tapiola, MD, PhD; Tuula Pirttilä, MD, PhD; Jaakko Rinne, MD, PhD; Juha E. Jääskeläinen, MD, PhD; Hilkka Soininen, MD, PhD; Juha O. Rinne, MD, PhD
Arch Neurol. 2008;65(10)
doi:10.1001/archneur.65.10.noc80013
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Written by Anna Sophia McKenney
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