Exam #1: Neuroimaging Flashcards
(42 cards)
what are the most relevant neuroimaging techniques for aphasiologists to know about?
- structural neuroimaging
- functional neuroimaging
types of structural neuroimaging:
- (CAT/CT) Computerized Axial Tomography
- (MRI) Magnetic Resonance Imaging
- (DTI) Difussion Tensor Imaging
- Cerebral Angiography (arteriography)
types of functional neuroimaging:
- (fMRI) Functional Magnetic Resonance Imaging
- (PECT/PET) Positron Emission (Computed Tomography)
- (EEG) Electroencephalography
structural neuroimaging
have a picture of the brain to see what is going on
functional neuroimaging
shows how your brain is functioning
Structural Neuroimaging:
Computerized Axial Tomography (CAT/CT) scan
- takes x-rays of thin slices of the brain (1-2 mm thick)
- bone and blood are high in density and absorb many x-rays, show up as light areas)
- white and gray matter and the ventricles are low density areas that don’t absorb many x-rays and therefore show up as dark areas (e.g., cerebral infarctions, edema, cystic lesions)
CT is useful in detecting both…
focal and progressive pathologies
for a CT scan, infarct may not be visible on the scan in what stages?
- acute
- fails to reveal small lesions
CT scan is useful to rule out…
- hemorrhages
- it is an important screening factor for the administration of tPA
- it is a quick and easy way of looking at the brain in the E.R.
what is tPA (thrombolytic plasminogen activator)?
a drug that acts as a clot buster when administered in the first hours following ischemic stroke onset
cost of CT scan:
- $1,500 (cheaper than MRI)
- available in most medical centers in the U.S.
(will not reveal lacunae arteries because they are too small)
Structural Neuroimaging:
Magnetic Resonance Imaging (MRI)
- capitalizes on the magnetic activities of hydrogen molecules contained in water in the body
- does not use radiation
why does an MRI show excellent distinctions between gray and white matter?
because gray matter contains more water than with matter
Why is an MRI superior to a CT scan for spatial resolution and identifying ischemic storkes?
- it detects small lesions missed by CT
- however, it takes longer to obtain images, and it makes loud banging noises, which some patients are unable to tolerate
Some patients may be unable to have MRI scans if they have metals that stick to magnets (e.g., pacemaker)
- damage device components
- inhibit pacemaker function
- trigger rapid pacing
- deliver inappropriate shocks
cost of an MRI:
$2,000 to 4,000
Structural Neuroimaging:
MRI - Diffusion Tensor Imaging (DTI) / Tractography
- method used to measure the directional flow of water molecules in the brain, thus mapping out white matter such as the corpus callosum and arcuate fasciculus as well as small fibers in the brain
in an MRI - DTI, by quantifying white matter connections between gray matter areas…
it is possible to have a metric of dysfunctional or damaged white matter in the brain
Structural Neuroimaging:
Cerebral Angiography
the arteries are infused with a radiopaque substance and then x-rays are taken of them
What is a cerebral angiography good for identifying?
thromboses, aneurysms, hemorrhages, and irregularly displaced arteries (e.g., caused by tumors or hematomas)
Cerebral Angiography:
x-ray radiopaque material shows…
- variation in blood circulation that might suggest vascular occlusions
- arterial sections beyond a clot that blocks the blood flow will not show up because the radiopaque materials is blocked
Functional Neuroimaging:
- functional magnetic resonance imaging (fMRI)
- positron emission (computed) tomography (PECT, or PET)
- electroencephalography (EEG)
Functional Neuroimaging:
shows how your brain is functioning
Functional Neuroimaging:
Functional Magnetic Resonance Imaging (fMRI)
- this method helps to detect changes in cerebral blood flow as the patient performs different activities
- shows the areas of the brain where the blood is flowing associating to the task they are doing - brain areas “light-up” when performing certain tasks
