With the general aging of the population, neurodegenerative diseases such as Alzheimer
have an increasing prevalence. Recently, anti-β-amyloid-antibodies such as aducanumab and
donanemab are under development. These treatments urge for techniques allowing early
diagnosis and treatment monitoring during disease. [18F]FDG PET allows the visualization
of metabolic disturbances and aid in the early diagnosis of Alzheimer, Amyloid PET is
able to detect the amyloid plaques which can be present years before symptom onset. A
recent meta-analysis demonstrated that amyloid PET has a high sensitivity (0.91) and
specificity (0.81) in the differential diagnosis between Alzheimer and controls, however
very poor specificity (0.41) was observed when differentiating between Alzheimer and
patients with mild cognitive impairment.
The National Institute on Aging together with the Alzheimer's Association (NIA-AA)
recently proposed the ATN classification which is based upon the pathological processes
present in Alzheimer's disease (amyloid, tau and neurodegeneration). The amyloid and tau
status can be obtained using cerebrospinal fluid analysis but also non-invasively using
an amyloid or tau PET scan. The N status can be obtained using an [18F]FDG PET scan which
is in Belgium part of standard of care. Both the [18F]FDG PET scan and the amyloid scans
using [18F]Vizamyl are also proposed in the diagnostic algorithm for early and
differential diagnoses of dementia .
Perfusion scans using [15O]H2O have shown a good correlation with [18F]FDG PET,
illustrating the potential of perfusion as a proxy for neuronal dysfunction. Previously,
it has been demonstrated that early amyloid scans represent perfusion and can therefore
be used as a proxy for neuronal activity.
Next generation PET/CT scanners, such as the Omni Legend have a very high sensitivity
which may enable ultra-short PET scans, which is important is this vulnerable patient
group, or dynamic scans with a high effective time resolution due to the possibility to
acquire short time frames with reasonable noise characteristics. Moreover, the ultrashort
scan may limit the movement artefacts frequently encountered in this study population.
The investigators hypothesize that a one minute scan 5 minutes postinjection is
sufficient to determine the N-status of a patients and that a one minute scan 90-110
minutes postinjection can determine the A-status.