6 - Functional Neuroimaging in Disease

Question 1

2 (outdated) Classifications of Disease types

Answer 1

Functional

Organic

Question 2

Functional Diseases

Answer 2

Outdated Term:
Invisible on autopsy, and maybe even microscopy (eg Huntington’s disease, Parkinson’s disease, depression, schizophrenia)

Question 3

Organic Diseases

Answer 3

Outdated Term:

Can be seen on autopsy (eg hemorrhage, stroke, inflammation, tumor, etc)

Question 4

2 (outdated) Classifications of Lesions

Answer 4

Structural
Functional
Used by Psychiatry still, but Neuroscience has left them behind.

Question 5

Structural Lesions / Structural Imaging

Answer 5

Visible/”Organic”

Stroke
Neoplasm
Infection
Inflammation
Trauma

Question 6

Functional Lesions / Functional Imaging

Answer 6

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

Question 7

Functional Imaging’s Mission

Answer 7

To examine regional changes in energy metabolism. This is done by examining visualizable neurovascular variables coupled to metabolism

Question 8

Visualizable neurovascular variables coupled to metabolism

Answer 8

Change in Blood Flow
Change in Cerebral Blood Volume
Change in Glucose Uptake
Change in Oxygen Metabolism
Deoxyhemoglobin Content

Question 9

PET - Mechanism

Answer 9

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.

Question 10

fMRI

Answer 10

Functional Magnetic Resonance Imaging

Question 11

SPECT

Answer 11

Single-Photon Emission Computed Tomography

Question 12

3 Functional Imaging Techniques

Answer 12

PET
fMRI
SPECT

Question 13

What is the relationship between Basal Cerebral Blood Flow (CBF) and Basal Cerebral Metabolic Rate for Oxygen (CMRO2)?

Answer 13

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.

Question 14

PET Scan - Values Measured

Answer 14

CBF, CBV, CMRO2

Question 15

fMRI - Values Measured

Answer 15

CBV, CBF, BOLD Deoxyhemoglobin

Question 16

SPECT - Values Measured

Answer 16

CBV, CBF

Question 17

What do you inject prior to an fMRI?

Answer 17

Gadolinium contrast

Question 18

Arterial Spin Labeling (ASL)

Answer 18

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.

Question 19

Blood Oxygen Level Dependent (BOLD) Deoxyhemoglobin pathway

Answer 19

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