Simplified quantification of Pittsburgh Compound B amyloid imaging PET studies: A comparative analysis
Department of Radiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA. Journal of Nuclear Medicine
(Impact Factor: 6.16).
PET studies have been performed using the amyloid binding radiotracer Pittsburgh Compound B (PIB). Previous quantitative analyses using arterial blood showed that the Logan graphical analysis using 90 min of emission data (ART90) provided a reliable measure of PIB retention. This work reports on simplified methods of analysis for human PIB imaging.
PIB PET scans were conducted in 24 subjects (6 Alzheimer's disease [AD], 10 mild cognitive impairment [MCI], 8 controls) with arterial blood sampling. Retest scans were performed on 8 subjects (3 AD, 1 MCI, 4 controls) within 28 d. Data were analyzed over 60 and 90 min using the Logan analysis and (a) metabolite-corrected input functions based on arterial plasma (ART60, ART90), (b) carotid artery time-activity data with a population average metabolite correction (CAR60, CAR90); and (c) cerebellar reference tissue (CER60, CER90). Data also were analyzed using the simplified reference tissue method (SRTM60, SRTM90) and a single-scan method based on late-scan ratios of standardized uptake values (SUVR60, SUVR90).
All methods of analysis examined effectively discerned regional differences between AD and control subjects in amyloid-laden cortical regions, although the performance of the simplified methods varied in terms of bias, test-retest variability, intersubject variability, and effect size. CAR90 best agreed with ART90 distribution volume ratio (DVR) measures across brain regions and subject groups and demonstrated satisfactory test-retest variability (+/-7.1% across regions). CER90 and CER60 showed negative biases relative to ART90 in high-DVR subjects but had the lowest test-retest variability. The single-scan SUV-based methods showed the largest effect sizes for AD and control group differences and performed well in terms of intersubject and test-retest variability.
Of the simplified methods for PIB analysis examined, CAR90 provided DVR measures that were most comparable to ART90; CER90 was the most reproducible and SUVR90 produced the largest effect size. All simplified methods were effective at distinguishing AD and control differences and may be effectively used in the analysis of PIB. SUVR60 data can be obtained with as little as 20 min of PET emission data collection. The relative strengths and limitations of each method must be considered for each experimental design.
Available from: Brian Maxwell Austen
- "Please cite this article as: Matharu, B., et al., Gadolinium-complexed Aβ-binding contrast agents for MRI diagnosis of Alzheimer's Disease, Neuropeptides (2015), http://dx.doi.org/10.1016/j.npep.2015.07.001 Compound B (PIB), a radioactive ligand that binds aggregated β-amyloid and is visualized by PET scanning (Lopresti et al., 2005). Studies with PIB have shown that the time course of various biomarkers of AD shows predictable patterns. "
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ABSTRACT: MRI contrast agents, containing peptide sequences that bind β-amyloid and gadolinium ions ligated to DOTA have been synthesized for evaluation in early diagnosis of Alzheimer's Disease in transgenic mice models. A number of brain penetration modifications were incorporated and sufficient amounts of contrast agent in the brain were achieved only by addition of a cationic cell penetration sequence along with the use of microparticle assisted ultrasound activation. In the T1 mode of a MRI scan, the peptide (R2) illuminated areas of brain rich in amyloid plaques.
Copyright © 2015 Elsevier Ltd. All rights reserved.
Neuropeptides 07/2015; 53. DOI:10.1016/j.npep.2015.07.001 · 2.64 Impact Factor
Available from: Matthew L Senjem
- "All PET quantitative image analysis including quality control were performed at the Mayo Clinic using the same fully automated image processing pipeline as described previously (Jack et al., 2008; Senjem et al., 2008). A global cortical PIB-PET retention ratio was computed by calculating the median uptake over voxels in the prefrontal, orbitofrontal, parietal, temporal, anterior cingulate, and posterior cingulate/precuneus regions of interest for each subject and dividing this by the median uptake over voxels in the cerebellar grey matter region of interest of the atlas (Lopresti et al., 2005). We classified subjects as being on the amyloid pathway (A + or Alzheimer's disease pathophysiology) if their global cortical PIB-PET value was 51.5. "
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ABSTRACT: Our primary objective was to investigate a biomarker driven model for the interrelationships between vascular disease pathology, amyloid pathology, and longitudinal cognitive decline in cognitively normal elderly subjects between 70 and 90 years of age. Our secondary objective was to investigate the beneficial effect of cognitive reserve on these interrelationships. We used brain amyloid-β load measured using Pittsburgh compound B positron emission tomography as a marker for amyloid pathology. White matter hyperintensities and brain infarcts were measured using fluid-attenuated inversion recovery magnetic resonance imaging as a marker for vascular pathology. We studied 393 cognitively normal elderly participants in the population-based Mayo Clinic Study of Aging who had a baseline 3 T fluid-attenuated inversion recovery magnetic resonance imaging assessment, Pittsburgh compound B positron emission tomography scan, baseline cognitive assessment, lifestyle measures, and at least one additional clinical follow-up. We classified subjects as being on the amyloid pathway if they had a global cortical amyloid-β load of ≥1.5 standard uptake value ratio and those on the vascular pathway if they had a brain infarct and/or white matter hyperintensities load ≥1.11% of total intracranial volume (which corresponds to the top 25% of white matter hyperintensities in an independent non-demented sample). We used a global cognitive z-score as a measure of cognition. We found no evidence that the presence or absence of vascular pathology influenced the presence or absence of amyloid pathology and vice versa, suggesting that the two processes seem to be independent. Baseline cognitive performance was lower in older individuals, in males, those with lower education/occupation, and those on the amyloid pathway. The rate of cognitive decline was higher in older individuals (P < 0.001) and those with amyloid (P = 0.0003) or vascular (P = 0.0037) pathologies. In those subjects with both vascular and amyloid pathologies, the effect of both pathologies on cognition was additive and not synergistic. For a 79-year-old subject, the predicted annual rate of global z-score decline was -0.02 if on neither pathway, -0.07 if on the vascular pathway, -0.08 if on the amyloid pathway and -0.13 if on both pathways. The main conclusions of this study were: (i) amyloid and vascular pathologies seem to be at least partly independent processes that both affect longitudinal cognitive trajectories adversely and are major drivers of cognitive decline in the elderly; and (ii) cognitive reserve seems to offset the deleterious effect of both pathologies on the cognitive trajectories.
© The Author (2015). Published by Oxford University Press on behalf of the Guarantors of Brain.
Brain 01/2015; 138(3). DOI:10.1093/brain/awu393 · 9.20 Impact Factor
Available from: Igor D Grachev
- "Thal Phases 1 and 2 correspond to the designation “A1” according to the “ABC” system set forth in the NIA-AA guidelines for the neuropathologic assessment of AD . Similar composite measurements have been previously described for [11C]PiB , [18F]flutemetamol , and [18F]florbetaben . Since the five brain regions vary considerably in size, and the mean was not corrected for VOI size, the SUVR of the composite VOI reflects the level of uptake as if all 5 regions were of equal importance and not the overall uptake level in the composite VOI. "
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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.
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.
Bielschowsky silver stain and overall pathology judgment showed the strongest associations with imaging results.
04/2014; 2(1):46. DOI:10.1186/2051-5960-2-46
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