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Diagnostic effectiveness of quantitative [¹⁸F]flutemetamol PET imaging for detection of fibrillar amyloid β using cortical biopsy histopathology as the standard of truth in subjects with idiopathic normal pressure hydrocephalus.
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2014 (English)In: Acta neuropathologica communications, E-ISSN 2051-5960, Vol. 2, 46- p.Article in journal (Refereed) Published
Abstract [en]

INTRODUCTION: PET imaging of amyloid-β (Aβ) in vivo holds promise for aiding in earlier diagnosis and intervention in Alzheimer's disease (AD) and mild cognitive impairment. AD-like Aβ pathology is a common comorbidity in patients with idiopathic normal pressure hydrocephalus (iNPH). Fifty patients with iNPH needing ventriculo-peritoneal shunting or intracranial pressure monitoring underwent [18F]flutemetamol PET before (N = 28) or after (N = 22) surgery. Cortical uptake of [18F]flutemetamol was assessed visually by blinded reviewers, and also quantitatively via standard uptake value ratio (SUVR) in specific neocortical regions in relation to either cerebellum or pons reference region: the cerebral cortex of (prospective studies) or surrounding (retrospective studies) the biopsy site, the contralateral homolog, and a calculated composite brain measure. Aβ pathology in the biopsy specimen (standard of truth [SoT]) was measured using Bielschowsky silver and thioflavin S plaque scores, percentage area of grey matter positive for monoclonal antibody to Aβ (4G8), and overall pathology impression. We set out to find (1) which pair(s) of PET SUVR and pathology SoT endpoints matched best, (2) whether quantitative measures of [18F]flutemetamol PET were better for predicting the pathology outcome than blinded image examination (BIE), and (3) whether there was a better match between PET image findings in retrospective vs. prospective studies.

RESULTS: Of the 24 possible endpoint/SoT combinations, the one with composite-cerebellum SUVR and SoT based on overall pathology had the highest Youden index (1.000), receiver operating characteristic area under the curve (1.000), sensitivity (1.000), specificity (1.000), and sum of sensitivity and specificity for the pooled data as well as for the retrospective and prospective studies separately (2.00, for all 3). The BIE sum of sensitivity and specificity, comparable to that for quantitation, was highest using Bielschowsky silver as SoT for all SUVRs (ipsilateral, contralateral, and composite, for both reference regions). The composite SUVR had a 100% positive predictive value (both reference regions) for the overall pathology diagnosis. All SUVRs had a 100% negative predictive value for the Bielschowsky silver result.

CONCLUSION: Bielschowsky silver stain and overall pathology judgment showed the strongest associations with imaging results.

Place, publisher, year, edition, pages
2014. Vol. 2, 46- p.
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
URN: urn:nbn:se:uu:diva-261036DOI: 10.1186/2051-5960-2-46PubMedID: 24755237OAI: oai:DiVA.org:uu-261036DiVA: diva2:849540
Available from: 2015-08-28 Created: 2015-08-28 Last updated: 2017-05-10
In thesis
1. Characterization of [18F]flutemetamol binding properties: A β-amyloid PET imaging ligand
Open this publication in new window or tab >>Characterization of [18F]flutemetamol binding properties: A β-amyloid PET imaging ligand
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The criteria for diagnosing Alzheimer’s disease (AD) have recently been revised to include the use of biomarkers for the in vivo presence of β-amyloid, one of the neuropathological hallmarks of AD. Examples of such biomarkers are positron emission tomography (PET) β-amyloid specific ligands, including [18F]flutemetamol. The aim of this thesis was to characterize the binding properties of [18F]flutemetamol from a tracer kinetic perspective as well as by validating binding measures through comparison with tissue pathology assessments. The applicability of previously developed kinetic models of tracer binding for voxel-based analysis was examined and compared to arterial input compartment modelling, the “gold standard” for PET quantification. Several voxel-based methods were found to exhibit high correlations with compartment modelling, including the semi-quantitative standardized uptake value ratio (SUVR). The kinetic components of [18F]flutemetamol uptake were also investigated without model assumptions using the data driven method spectral analysis, with binding to β-amyloid shown to relate to a slow kinetic component. The same component was also found to predominate in the uptake of white matter, known to be free of β-amyloid accumulation. White matter uptake was however possible to separate from β-amyloid binding based on the relative contribution of the slow component to the total volume of distribution. Uptake of [18F]flutemetamol as quantified using SUVR or assessed visually was found to correlate well with tissue pathology assessments. Classifying the brains of 68 deceased subjects who had undergone [18F]flutemetamol PET scanning ante mortem, based on the spatial distribution of β-amyloid according to pre-defined phases, revealed that abnormal uptake patterns of [18F]flutemetamol were only certain to be found in the last phase of β-amyloid accumulation. In the same cohort however, [18F]flutemetamol was also shown to accurately distinguish between subjects with AD and non-AD dementia. While this supports the use of [18F]flutemetamol in clinical settings for ruling out AD, the association of abnormal [18F]flutemetamol uptake to late phases of β-amyloid accumulation may limit the detection of early accumulation and pre-clinical stages of AD. It remains to be investigated whether application of voxel-based methods and slow component filtering may increase sensitivity, particularly in the context of clinical trials.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 74 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1139
Keyword
Positron emission tomography (PET), molecular imaging, amyloid, tracer validation
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Radiology
Identifiers
urn:nbn:se:uu:diva-262019 (URN)978-91-554-9356-1 (ISBN)
Public defence
2015-11-19, Skoogsalen, Akademiska Sjukhuset, Ingång 79, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2015-10-28 Created: 2015-09-07 Last updated: 2015-11-10

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