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C3 > L10 Imaging Alzheimer's Disease > Flashcards

L10 Imaging Alzheimer's Disease Flashcards

1
Q

where does the disease start in AD and where does it spread

A

in preclinical stage starts in trans-entorhinal to limbic to neocortical

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2
Q

what are types of dementia

A

alzheimers
vascular
dementia with lewy bodies
frontotemporal

prion
progressive supranuclear palsy
huntingdon’s disease
leukodystrophies, SCAs, CADASIL

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3
Q

with what imaging can we see cerebral perfusion and metabolism

A

SPECT
MRI perfusion and fMRI
FDG-PET

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4
Q

what can you see with molecular imaging

A

PET: amyloid or tau
activated microglia
synaptic density
PET tracers can bind to amyloid and tau deposits - imaging the histological hallmarks of AD, and ligands that can assess specific neurotransmitter systems - such as the dopaminergic transporter uptake - preferentially affected in lewy body disease

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5
Q

what imaging type is used in current clinical practice for AD

A

t2 (FLAIR) to assess vascular and other pathology
volumetric T1-w imaging to assess atrophy pattern
diffusion for CJD
functional imaging to distinguish FTLD from AD

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6
Q

what is purpose of the research framework

A

acknowledge increasing use of imaging and other biomarkers

separates biology from clinical syndrome

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7
Q

what are the steps from pathology to neurodegeneration

A

protein misfolding and accumulation
neuronal loss in vulnerable networks
progressive atrophy
progressive symptoms

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8
Q

what is AD characterised by

A

symmetrical atrophy with posterior greater than anterior loss

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9
Q

what sites show early change in AD

A

medial temporal lobe
precuneus
posterior cingulate

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10
Q

what % is the hippocampus smaller in patients than in controls

A

10-20%

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11
Q

what does atrophy relate to

A

loss of neurons

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12
Q

there is a high correlation between MRI volumetric measures and …

A

no. of neurons present

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13
Q

what is hippocampla atrophy a risk factor for

A

progression for MCI –> AD

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14
Q

what may be the earliest region in atrophy published by Devanand et al

A

entorhinal cortex - neurofibrillary tangles may first appear there before spreading to medial temporal lobe structures and then on neocortical association areas

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15
Q

apart from ad where else is symmetrical hippocampal atrophy seen in

A

dementia with lewy bodies

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16
Q

what is a reliable way to distinguish AD from DLB

A

PET using tracers binding to amyloid and dopamine transporter uptake

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17
Q

what focal atrophy patterns have positive/negative predictive value for FTLD /AD

A

FTLD +VE

AD -VE

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18
Q

what is TDP-43 pathology related to

A

increased hippocampal atrophy rates in addition to f tau and amyloid status

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19
Q

what do tau negative subjects show that separate them from tau positive shown in Josephs et al

A

show FDG pattern that results in a simple ratio of inferior to medial temporal lobes on the FDG image

20
Q

what is LATE and what is it associated with

what % in what age group

A

limbic predominant age-related TDP-43 encephalopathy
clinically related to AD symptoms that are more severe than expected for the amount of amyloid and tau pathology. often associated with hippocampal sclerosis

20-50% of individuals over age 80

21
Q

what is the most used functional imaging and what can it show comparing AD to FTLD

A

PET using radiolabelled glucose

pattern of hypo metabolism different in FTD than AD, more frontal, less parietal

22
Q

what have studies such as Klunk and Mathis, Rowe, Nelissen, Rabinovici shown in AD compared to controls

A

increased level of amyloid binding

23
Q

in what MCI subjects does amyloid binding increase in

A

subjects who progress to AD

24
Q

in ADNI data used to track the spread of amyloid deposition, what does the analysis show of areas with amyloid

A

first areas were inferior temporal lobe and anterior cingulate followed by precuneus, posterior cingulate and prefrontal cortex.
medial temporal and subcortical structures some of last to change

25
Q

what does spatiotemporal distribution of beta-amyloid in Alzheimer’s disease results from

A

heterogeneous regional carrying capacities

26
Q

in a graph of x axis-time and y axis SUVr. what is r,NS, T.50, K symbolise on a curve

which ones are regional and which ones are global

A

r - growth rate
NS - non-specific binding
T.50 - transition time from no to max binding
K - tissue carrying capacity

regional: K and NS
global: r and T.50

27
Q

what does tau-PET imaging with 11^C-PBBR show

A

medial temporal lobe shows no to little amyloid binding to in AD

28
Q

the pattern of amyloid deposition does not associate strongly with …

A

patterns of atrophy and glucose hypometabolism

29
Q

the pattern of tau deposition does associate strongly with

A

patterns of atrophy and glucose hypometabolism

30
Q

what are tau-PET limitations

A
  • non-specific uptake in basal ganglia, thalamus, choroid plexus, likely telated to monoamine oxidase B
  • increased uptake in non-tau pathologies (semantic dementia) and no uptake in some tau pathologies
31
Q

what staging does the spread of tau pathology follow

A

Braak

32
Q

the paper by Cho H Lee et al on predicted sequence of cortical tau and amyloid beta deposition shows what regions are positive in tau and amyloid interactions

A

tau : entorhinal cortex is positive before any other region becomes tau positive or amyloid positive
the parahippocampal gyrus, fusiform fyrus, amygdala and inferior temporal lobe are the next regions to turn tau positive

in amyloid: whole host of regions turn positive roughly at same time as tau

33
Q

what is a reliable biomarker to track the disease

A

measure the rate of loss over multiple scans from the same individual

34
Q

what is the % of atrophy rates per year in control compared to AD and what are the volumes for brain, ventricle, hippocampus

A 
Brain: 1000 ml
Ventricle: 40ml
Hippocampus: 2-5ml
B: 0.3% / 2%
V: 1ml / 5ml
H: 0.6% / 4%
35
Q

why may one scan not be enough

A

atrophy overlaps with aging

36
Q

what happens in registration

A

a transform that maps one scan onto another by matching image features and voxel gray level.
uses all information within complex brain structure

37
Q

what is boundary shift integrsl

A

integrating shifts in intensity differences at brain boundary
require highly accurate alignment and consistent imaging protocols and quality

38
Q

how is atrophy measurement through non-rigid registration

A

neurodegeneration involves structural readjustments as well as tissue loss
model volume changes by warping one image to match another

39
Q

why do drug trials require a primary endpoint

A

to see if patient feels functions or survices

40
Q

what do atrophy measures show and how changing helps

A

atrophy measures show the underlying disease process. atrophy measures changing would help prove disease modification if atrophy was slowed with symptomatic benefit

41
Q

what do primary endpoints in AD trials measure

A

function

42
Q

what do imaging endpoints for AD trials require

A

smaller sample sizes

43
Q

in what clinical trial were there clear reductions in clinical decline with high dose aducanumab

A

EMERGE

44
Q

in what clinical trials were there clear reductions in amyloid PET with high dose aducanumab

A

EMERGE

ENGAGE

45
Q

Is the prevalence of dementia in the elderly population (e.g 70-80 years old)?
Your risk?
What are the major causes of dementia?
Where are the earliest sites of pathological involvement in AD – and how does it progress?
What are the characteristic features of AD on
CT
MRI
Functional imaging (PET/Spect)
Other imaging modalities
Roles of imaging?

A

need to go through

C3 (13 decks)

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