Samenvatting
Summary Neurological and Psychiatric Disorders (AB_1023)
This document consists of a summary of the course Neurological and Psychiatric Disorders, corresponding to the Minor Biomedical Topics in Healthcare.
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Voorbeeld van de inhoud
Neurological and Psychiatic DisordersNeurological and Psyciatric
Disorders (AB_1023) 2022 - 2023
,Neurological and Psychiatric Disorders (AB_1023) 2022-2023
Brain MRI
Learning objectives
o Being able to name different imaging modalities of the brain.
o Being able to describe the technique behind the imaging.
o Being able to describe the underlying neurobiological substrate that is measured.
Neuroimaging is used for:
• Clinic
▪ For diagnosis/prognosis
▪ CT, MRI, MRA, MRS, PET, X-ray
• Research
▪ For improvement of diagnostics
▪ For prediction
▪ To understand biological processes
Brain imaging in research:
• Qualitative
▪ Standard clinical practice
▪ Look for pathology
• Quantitative
▪ ‘Numbers’ as output
▪ Used to understand biological mechanisms
▪ Compare patient groups to healthy controls.
Anatomical planes
o Axial = separates top from bottom
o Coronal = separates front from back
o Sagittal = separates left from right
1.1 Structural imaging
Structural Brain Imaging (X-ray, CT and MRI) can be used to identify effects of stroke, locating cysts
and tumors, finding swelling and bleeding and disease-related lesions
CT-scan = 3D x-ray with a low resolution. Bones are light in a CT-scan
MRI scan = higher resolution. Bones are dark in a MRI-scan.
1.1.1 How does an MRI machine work?
MRI has a great resolution and shows tissue well. MRI uses magnetism and radiofrequency signals to
acquire images. MRI images are based on density of protons. Hyrogen atoms are randomly positions.
The spin of these hydrogen atoms are directed in the direction of the magnetic field. Using a radiopulse
the spin direction changes. The time it takes for the direction of the spin to go back to the original
direction gives the image.
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,Neurological and Psychiatric Disorders (AB_1023) 2022-2023
Advantages of MRI Disadvantages of MRI
Non invasive Time consuming
Non-ionizing radiation Contradictions for MRI (pacemaker e.g.)
High soft-tissue resolution and discrimination between Noise
tissue types
Morphological information (form and structure) as well Sequence need to be adapted to question
as functional information
1.1.2 T1 and T2, what is that
Main techniques in MRI:
• T1 weighted images
▪ Shows contrast between fat and water
▪ Is used in anatomy and enhancement
▪ Water is shown in black and fat is shown in white
• T2 weighted images
▪ Shows contrast between water and tissue
▪ Is used in pathology
▪ Water is white, tissue is black. Because the water is white, it is really good visible and
you can find edema’s easily.
• FLAIR (Fluid-attenuated inversion recovery)
▪ T2 weighted MRI scan
▪ Inversion recovery (= null the signal for certain tissue). CSF (cerebrospinal fluid) is
suppressed, so water is also shown as black in the image.
▪ This technique makes it easier to see the damaged area.
• Double inversion recovery
▪ T2 + FLAIR
▪ Both CSF and white matter signal.
▪ Lesions (damages tissue) in the white matter of between grey/white matter
1.1.3 MRA
MRA (Magnetic Resonance Angiography) uses a powerful magnetic field and radio waves to evaluate
blood vessels and help identify abnormalities like AVM (Arteriovenous Malformation). An AVM is an
abnormal tangle of blood vessels connecting arteries and veins, which disrupts normal blood flow.
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, Neurological and Psychiatric Disorders (AB_1023) 2022-2023
1.1.4 DTI
White matter is very important in diseases like
alzheimer’s disease, parkinson’s disease, multiple
Sclerosis and schizophrenia. DTI (Diffusion Tensor
Imaging) sees how water moves in the brain and
assessed the integrity (eigenschap) of the white matter:
Isotropic or Anisotropic. DTI provides information about
structural connectivity by quantifying the number of
axons between two brain regions. Tractofraphy can be used as a 3D modeling technique to visually
represent nerve tracts.
Four main diffucion outcome parameters for microstructural integrity
1. Fractional anisotropy (FA) – directionality of water diffusion
2. Mean diffusivity (MD) – the average diffusivity
3. Axonal diffusivity (AD) – diffusivity along the axes
4. Radial diffusivity (RD) – diffusivity perpendicular (loodrecht) to the axon
1.2 Functional imaging
1.2.1 PET
PET (Positron Emission Tomography) uses radiotraces (isotopes) to visualize and measure metabolic
processes. The isotopes bind to specific substances in the tissue and because they are radioactive they
are traceable. An injection with radioactive isotopes are given in an artery. To detect the radioactive
isotopes gamma ray emission is used. PET is most of the time used in combination with a CT or MRI to
visualize the spread of the isotopes.
For cancer to grow it needs energy, glucose. To detect cancer you can use a isotope that binds to
glucose. PET is one of the most reliable ways to detect alzheimer’s disease.
1.2.2 MRS
MRS (Magnetic Resonance Spectroscopy) is a special type of MRI. It generates a spectrum instead of a
image. It measures metabolite (choline, creatine, GABA, glutamate, glutathione) concentration in the
brain. Using MRS there is no ionizing radiation.
1.2.3 fMRI
fMRI (functional MRI) measures differences in oxygenated
blood and deoxygenated blood. It measures the
hemodynamic response of neuronal activity. This works by
using blood-oxygen level depended (BOLD) contrast. The
neural activity is way faster than the BOLD-signal. fMRI is
indirect, because you measure brain activity based on blow
flow.
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