6 - Functional Neuroimaging in Disease Flashcards
2 (outdated) Classifications of Disease types
Functional
Organic
Functional Diseases
Outdated Term:
Invisible on autopsy, and maybe even microscopy (eg Huntington’s disease, Parkinson’s disease, depression, schizophrenia)
Organic Diseases
Outdated Term:
Can be seen on autopsy (eg hemorrhage, stroke, inflammation, tumor, etc)
2 (outdated) Classifications of Lesions
Structural
Functional
Used by Psychiatry still, but Neuroscience has left them behind.
Structural Lesions / Structural Imaging
Visible/”Organic”
Stroke Neoplasm Infection Inflammation Trauma
Functional Lesions / Functional Imaging
Invisible/”Functional”
Early Stage Neurodegeneration (Alzheimer’s, Parkinson’s, Fronto-Temporal Degeneration, ALS)
Psychiatric Illness (Schizophrenia, PTSD, Depression)
Developmental Disorders (Autism, Dyslexia)
Toxins (‘Chemo’ Brain)
Cognitive Aging
Functional Imaging’s Mission
To examine regional changes in energy metabolism. This is done by examining visualizable neurovascular variables coupled to metabolism
Visualizable neurovascular variables coupled to metabolism
Change in Blood Flow Change in Cerebral Blood Volume Change in Glucose Uptake Change in Oxygen Metabolism Deoxyhemoglobin Content
PET - Mechanism
Positron Emission Tomography
Unstable radionuclides injected into bloodstream, taken up by the brain.
Radionuclide emits positron, collides with electron, forms a gamma ray, identifying site of uptake.
fMRI
Functional Magnetic Resonance Imaging
SPECT
Single-Photon Emission Computed Tomography
3 Functional Imaging Techniques
PET
fMRI
SPECT
What is the relationship between Basal Cerebral Blood Flow (CBF) and Basal Cerebral Metabolic Rate for Oxygen (CMRO2)?
Linear relationship across broad dynamic range
Fixed and Firm across all regions of the brain (Invariant)
1:1
THIS IS ONLY IN THE BASAL STATE. CBF and CMRO2 have a different relationship that varies, depending on the areas being activated.
PET Scan - Values Measured
CBF, CBV, CMRO2
fMRI - Values Measured
CBV, CBF, BOLD Deoxyhemoglobin
SPECT - Values Measured
CBV, CBF
What do you inject prior to an fMRI?
Gadolinium contrast
Arterial Spin Labeling (ASL)
A magnetic moment is picked up by MRI scanners when the coil applies a magnetic field and forces the spin of the blood to tilt.
Blood Oxygen Level Dependent (BOLD) Deoxyhemoglobin pathway
BOLD measures total deoxyhemoglobin content (not concentration)
Weird roundabout pathway: Increase in O2 metabolism leads to Increase in O2 delivery leads to Decrease in deoxyhemoglobin Leads to increase in MRI signal
Bottom Line:
More metabolism = More Signal
