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Validation of true low-dose 18F-FDG PET of the brain
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. (Elna-Marie Larsson)ORCID iD: 0000-0001-5615-2036
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Hermes Medical Solutions, Stockholm, Sweden. (Nuklearmedicin och PET)ORCID iD: 0000-0002-9752-6142
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. (Nuklearmedicin och PET)ORCID iD: 0000-0002-2454-5086
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2016 (English)In: American Journal of Nuclear Medicine and Molecular Imaging, ISSN 2160-8407, Vol. 6, no 5, 269-276 p.Article in journal (Refereed) Published
Abstract [en]

The dosage of 18F-FDG must be sufficient to ensure adequate PET image quality. For younger patients and research controls, the lowest possible radiation dose should be used. The purpose of this study was to find a protocol for FDG-PET of the brain with reduced radiation dose and preserved quantitative characteristics. Eight patients with neurodegenerative disorders and nine controls (n=17) underwent FDG-PET/CT twice on separate occasions, first with normal-dose (3 MBq/kg), and second with low-dose (0.75 MBq/kg, 25% of the original). Five additional controls (total n=22) underwent FDG-PET twice, using normal-dose and ultra-low-dose (0.3 MBq/kg, 10% of original). All subjects underwent MRI. Ten-minute summation images were spatially normalized and intensity normalized. Regional standard uptake value ratios (SUV-r) were calculated using an automated atlas. SUV-r values from the normal- and low-dose images were compared pairwise. No clinically significant bias was found in any of the three groups. The mean absolute difference in regional SUV-r values was 0.015 (1.32%) in controls and 0.019 (1.67%) in patients. The ultra-low-dose protocol produced a slightly higher mean difference of 0.023 (2.10%). The main conclusion is that 0.75 MBq/kg (56 MBq for a 75-kg subject) is a sufficient FDG dose for evaluating regional SUV-ratios in brain PET scans in adults with or without neurodegenerative disease, resulting in a reduction of total PET/CT effective dose from 4.54 to 1.15 mSv. The ultra-low-dose (0.5 mSv) could be useful in research studies requiring serial PET in healthy controls or children.

Place, publisher, year, edition, pages
Madison, USA: e-Century Publishing Corporation , 2016. Vol. 6, no 5, 269-276 p.
Keyword [en]
PET, FDG, neuroimaging, neurodegeneration, methodology
Keyword [sv]
Hjärnavbildning, PET, lågdos, demens, neurodegenerativ
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Radiology
Identifiers
URN: urn:nbn:se:uu:diva-304730OAI: oai:DiVA.org:uu-304730DiVA: diva2:1033711
Available from: 2016-10-08 Created: 2016-10-08 Last updated: 2017-11-30Bibliographically approved
In thesis
1. ­­­Visual assessment of perfusion and metabolism in neurodegenerative dementia
Open this publication in new window or tab >>­­­Visual assessment of perfusion and metabolism in neurodegenerative dementia
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A worldwide demographic shift is currently occurring, with rapidly increasing numbers of elderly individuals. Since the incidence of neurodegenerative disease generally increases with age, this entails an increase in dementia prevalence. There are several strong incentives for establishing robust and widely available imaging methods for the early diagnosis of these diseases. Atrophy patterns are evident only late in the disease process, and the distinction from healthy ageing can often be elusive. For early diagnosis, physiologic parameters such as perfusion or metabolism must be assessed. The available modalities all have restricted clinical usefulness. The main aim of this thesis was to advance the clinical usefulness of perfusion and metabolism imaging in patients with neurodegenerative dementia, with a focus on visual assessment.

A cohort of patients with neurodegenerative dementia was included, along with an age-matched control group. All subjects underwent MRI, including a pseudocontinuous ASL sequence and FDG-PET. In papers II and III, a subgroup containing both patients and controls underwent a second FDG-PET with reduced dose. In paper IV, the material was combined with a similar cohort from Amsterdam.

Paper I showed that spatial smoothing increased the correlation between visually assessed perfusion and metabolism levels as displayed with FDG-PET. However, the distinction between patients and healthy controls was less satisfactory due to false positives.

Paper II showed that differences in regional standard uptake value ratios between normal- and low-dose FDG-PET were small and without clinically significant bias.

Paper III showed that the diagnostic performance of Z-score maps showing regions of significant deficits in metabolism was highly similar in normal- and low-dose FDG-PET images. 

Paper IV showed that ASL perfusion-based Z-score maps can be used for diagnostic purposes with high specificity, but inferior sensitivity, compared to FDG-PET.

In conclusion, the included studies address aspects of the visual assessment of perfusion and metabolism neuroimaging, with a focus on clinical usefulness in diagnosing neurodegenerative dementia.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 65 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1266
Keyword
Dementia, Neurodegenerative, Brain imaging, Diagnostics, Neuroradiology, Neuroimaging, Demens, Neurodegenerativ, Hjärnavbildning, diagnostik, Neuroradiologi, Neuroimaging
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Radiology
Identifiers
urn:nbn:se:uu:diva-304731 (URN)978-91-554-9714-9 (ISBN)
Public defence
2016-12-07, Gunnesalen, Akademiska Sjukhuset, ing 10, 751 85, Uppsala, 09:00 (English)
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Available from: 2016-11-14 Created: 2016-10-08 Last updated: 2016-11-30

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