Abstract
Positron emission tomography-magnetic resonance imaging (PET/MRI) is an emerging hybrid imaging system in clinical nuclear medicine. Research demonstrates a comparative utility to current unimodal and hybrid methods, including PET-computed tomography (PET/CT), in several medical subspecialities such as neuroimaging. The aim of this review is to critically evaluate the literature from 2016 to 2021 using PET/MRI for the investigation of patients with mild cognitive impairment or dementia, and discuss the evidence base for widening its application into clinical practice. A comprehensive literature search using the PubMed database was conducted to retrieve studies using PET/MRI in relation to the topics of mild cognitive impairment, dementia, or Alzheimer's disease between January 2016 and January 2021. This search strategy enabled studies on all dementia types to be included in the analysis. Studies were required to have a minimum of 10 human subjects and incorporate simultaneous PET/MRI. A total of 116 papers were retrieved, with 39 papers included in the final selection. These were broadly categorised into reviews (12), technical/methodological papers (11) and new data studies (16). For the current review, discussion focused on findings from the new data studies. PET/MRI offers additional insight into the underlying anatomical, metabolic and functional changes associated with dementia when compared with unimodal methods and PET/CT, particularly relating to brain regions including the hippocampus and default mode network. Furthermore, the improved diagnostic utility of PET/MRI, as reported by radiologists, offers improved classification of dementia patients, with important implications for clinical management.
Highlights
Nuclear medicine today includes hybrid imaging modalities such as combined positron emission tomography (PET) and computed tomography (CT), improving on previously used PET‐only cameras
Despite the significant economic and technical barriers, the motivation to advance the use of Positron emission tomography–magnetic resonance imaging (PET/magnetic resonance imaging (MRI)) within routine clinical practice stems from the superior structural information provided by MRI compared to CT, as well as the technical advantages of improved coregistration, and service benefits associated with reducing scanning time
blood oxygen level dependent–functional connectivity (BOLD‐FC) was positively associated with mean cerebral blood flow (CBF) independently of glucose metabolism in the default mode network (DMN) of patients (p = 0.050), suggesting that an impairment in vascular haemodynamic processes contribute to impaired blood‐oxygen level‐dependent (BOLD)‐FC in Alzheimer's disease (AD), separately to reduced neuronal activity
Summary
Nuclear medicine today includes hybrid imaging modalities such as combined positron emission tomography (PET) and computed tomography (CT), improving on previously used PET‐only cameras. The increased diagnostic accuracy of PET/CT, in addition to the reduction in emission scan time resulting from both lutetium‐based PET scintillators, and CT‐based attenuation correction[1] resulted in an economically viable product for widespread clinical use. Despite the significant economic and technical barriers, the motivation to advance the use of PET/MRI within routine clinical practice stems from the superior structural information provided by MRI compared to CT, as well as the technical advantages of improved coregistration, and service benefits associated with reducing scanning time. MRI utilises a magnetic field and radiofrequency pulse to influence the axial spin of hydrogen protons, abundant in water and fat, with the energy emitted during proton relaxation used to produce highly sensitive structural images.[11] Compared to PET/CT, the soft tissue contrast, multiplanar capability, and reduced radiation dose offered by PET/MRI makes it an increasingly attractive tool, within neuroimaging
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