Week 2 H4,13,19 Flashcards
First Imaging Technique in Neuropsychology
Computed Tomography (CT)
Types of Neuroimaging
Structural: Investigates the anatomy of the brain.
Functional: Depicts underlying processes like water movement or blood flow.
Examples of Structural Neuroimaging
CT (Computed Tomography) and MRI (Magnetic Resonance Imaging).
Examples of Functional Neuroimaging
PET (Positron Emission Tomography), SPECT (Single Photon Emission Computed Tomography), EEG (Electroencephalogram), MEG (Magnetoencephalography).
How does a CT scan produce a brain image?
- A motorized X-ray source rotates in a spiral around the patient’s head.
- Beams of X-rays are sent through the head from various angles, capturing thin slices of the brain.
- Digital X-ray detectors measure the strength of radiation after it passes through the head.
- The computer uses this information to calculate areas of stronger or weaker absorption using algorithms.
- A two-dimensional image is constructed.
- Multiple cross-sectional images are combined to create a three-dimensional image.
which three things do CT images allow a neuroradiologist to observe and deduce about the inside of the head?
Atrophy (tissue loss)
Swelling post brain trauma
Congenital abnormalities
How does CT imaging depict changes in brain tissue due to most diseases, and when is CT commonly used in a clinical setting?
Most diseases increase the brain tissue’s water content, which appears darker (hypodense) on CT compared to normal tissue. Blood and calcium appear white (hyperdense). CT is frequently used in acute settings for quick patient diagnosis.
How does the presence of radiological contrast agents in the brain indicate potential pathology?
When there’s a pathology, the blood-brain barrier is compromised. This allows the contrast fluid to enter the brain, enhancing the CT image, indicating potential cerebral diseases.
What is CT perfusion (CTP) and how does it utilize contrast agents?
herhaalde CT-scans worden gemaakt om veranderingen in de bloedstroom en doorbloeding in een specifiek orgaan of weefsel in realtime te meten en in kaart te brengen.
intraveneuze contrastmiddelen geïnjecteerd, en vervolgens worden meerdere opeenvolgende CT-scans gemaakt om de distributie van het contrastmiddel in de weefsels te volgen.
What are two disadvantages of using CT scans?
Cannot differentiate between various brain tissue types.
Exposure to radiation poses a risk of DNA damage and potential cancer risk.
How does MRI technology work to visualize the brain?
- Hydrogen atoms in the body have protons that rotate, creating a magnetic field.
- MRI’s strong magnetic field alters the rotation of these protons to align with its axis.
- A horizontal radio frequency pulse from the MRI disrupts this alignment (excitation).
- When the pulse stops, protons return to their original state, releasing energy (relaxation).
- Radio frequency coils capture this energy release.
- Computer processes these signals to visualize the brain structure slice by slice.
In MRI scans, how are bright and dark areas described?
Bright areas: Hyperintense
Dark areas: Hypointense
How are water-rich structures and fat depicted in T1-weighted MRI images?
Water-rich structures: Dark (low signal intensity)
Fat: Light grey to white (short T2 relaxation time)
Why are T1-weighted scans used when viewing the anatomy of the brain?
They show good contrast between CSF, grey matter, and white matter.
What is the primary use of T2-weighted images in brain imaging?
T2-weighted images are mainly used to detect brain abnormalities, especially those accompanied by an increase in water content in the brain tissue.
What is the FLAIR sequence in MRI?
FLAIR (Fluid-Attenuated Inversion Recovery) is an MRI sequence similar to T2-weighted images but with dark CSF.
Why is the FLAIR sequence useful?
It detects subtle changes near the CSF (cerebrospinal fluid), especially in the hemispheres and the periventricular area.
In which conditions is FLAIR particularly beneficial?
lacunar stroke and multiple sclerosis to reveal ‘white spots’ or scars from inflammations.
What are T2and SWIin MRI, and what techniques are they associated with?
T2 and Susceptibility Weighted Imaging (SWI) are gradient echo techniques in MRI.
What do T2* and SWI sequences help visualize?
They image deoxygenated blood, hemosiderin residues (blood products), iron, and calcium.
What does MRI with diffusion-weighted imaging (DW) measure? where is it used for?
- DW measures the microscopic movement of water molecules (diffusion) in the brain.
- It is highly sensitive to acute stroke, assess brain tumors, abscesses, and other brain pathologies.
Describe isotropic vs. anisotropic diffusion in DWI.
Isotropic diffusion is the normal, random movement of water molecules.
Anisotropic diffusion indicates restricted water movement due to pathologies like tumors or swollen cells.
What is the difference between DWI and diffusion tensor imaging (DTI) in MRI?
DWI primarily measures the magnitude and direction of water diffusion within tissues –> information about the overall diffusion properties of water in tissues –> rapid identification of acute stroke, brain tumors, and areas of inflammation or cellular proliferation in various tissues.
DTI beyond DWI by measuring the diffusion of water in multiple directions within each voxel –> information about the anisotropic diffusion of water –>traumatic brain injury, multiple sclerosis, and neurodegenerative diseases.
What does DTI inform us about white matter pathways?
DTI allows us to understand how white matter pathways run in the brain using tractography.
What is perfusion in the context of the brain?
refers to the delivery of oxygen and nutrients to the brain through the bloodstream.
List the three types of perfusion techniques and briefly describe each.
- Dynamic susceptibility contrast (DSC) perfusion: Uses gadolinium and results in T2- or T2*-weighted images.
- Dynamic contract-enhanced (DCE) perfusion: Uses gadolinium and results in a T1-weighted image.
- Arterial spin labelling (ASL): No contrast agent; uses naturally occurring water in arterial blood as contrast. Mainly for research.
How does MRS differ from MRI in analyzing the brain, and in which patient groups is MRS commonly used?
-
mriprovides detailed anatomical images of the brain and its structures.
MRSgoes beyond anatomical imaging to provide information about the chemical composition of brain tissues. - MRS is used in children for metabolic disorder detection, stroke patients, and epilepsy patients.
What is the significance of the BOLD signal in fMRI?
The BOLD (Blood Oxygenation Level Dependent) signal reflects the ratio of oxygenated (diamagnetic) to deoxygenated (paramagnetic) blood in brain areas, helping to identify active regions.
How does fMRI help map brain areas involved in specific tasks?
fMRI compares resting state images with active state images to identify brain areas involved in certain tasks.
What is the Default Mode Network (DMN) and its main components?
- The DMN represents intrinsic brain activity during rest.
- Its main components are
1. the posterior cingulate gyrus,
2. medial and lateral parietal areas,
3. the medial prefrontal cortex.
What is the Frontal-Parietal Network (FPN) and its main components?
- active both at rest and during motor and cognitive tasks (spatial attention, mental rotation, working memory tasks).
- concists of:
1. the posterior parietal cortex,
2. premotor,
3. prefrontal cortex (including the frontal eye field).
What is the Salience Network and its primary regions?
- involved in complex brain functions including communication, social behavior, and self-awareness.
- Its key regions are:
1. the anterior insula
2. dorsal anterior cingulate cortex.
What is nuclear imaging
Nuclear imaging involves functional techniques using radioactive substances (bijv PET en SPECT).
How do PET scans work?
- A radioisotope ‘tracer’ is injected into the patient.
- The tracer travels to the brain and disintegrates, emitting a positron.
- The positron collides with an electron, releasing gamma rays.
- Detectors capture these rays, and a computer generates a 3D image showing the tracer’s distribution.
Disadvantages of PET scan?
- High cost.
- Lower resolution compared to CT and MRI.
Advantages of PET scan?
- Can detect brain diseases before anatomical changes are visible.
- Radiation load on the patient is relatively low.
Difference between SPECT and PET?
terwijl SPECT gammastralen detecteert uitgezonden door radioactieve isotopen en 2D-beelden levert, gebruikt PET positron-emitterende isotopen om 3D-beelden te creëren, en biedt over het algemeen een hogere ruimtelijke resolutie en kwantitatieve capaciteiten
two advantages and Disadvantages of EEG?
- Low cost
- extremly High temporal resolution
- Low spatial resolution (hard to pinpoint exact activity location)
- only captures cortical activity, missing deeper brain areas.
What does MEG do?
MEG detecteert de zwakke magnetische velden die worden geproduceerd door de elektrische activiteit van neuronen in de hersenen.
What does vascular cognitive impairment refer to?
Vascular cognitive impairment covers the entire spectrum of cognitive consequences resulting from vascular disease, ranging from mild impairment to full-blown dementia.