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Questions and Answers
What is one advantage of CT scans over MRI scans?
Which of the following conditions may make MRI unsuitable for a patient?
How does MRI technology primarily differentiate between types of tissue?
What feature of MRI provides a clearer image compared to CT?
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What happens initially when a person is placed inside an MRI scanner?
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Which brain imaging technique is better for rapid scanning needs?
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What primary benefit does MRI provide regarding brain structure imaging?
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What type of imaging allows researchers to measure ongoing regional brain activity?
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Which imaging technique provides structural information about the brain at a single point in time?
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What is one disadvantage of EEG compared to structural imaging techniques?
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What do MRS-derived levels compare between groups?
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Which technique can visualize activity in the brain by using a radioactive tracer?
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Which of the following techniques involves manually tracing regions of interest on MRI slices?
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What is the function of event-related potentials (ERPs)?
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Which type of imaging technique typically has high temporal resolution but poor spatial resolution?
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How do voxel-based morphometry (VBM) techniques differ from earlier volumetric analyses?
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What does the term 'Tesla' refer to in MRI imaging?
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In which range does the strength of clinical MRI scanners typically fall?
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How does cerebrospinal fluid appear on T1-weighted images?
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What is the purpose of fluid-attenuated inversion recovery (FLAIR) imaging?
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What advantage does Diffusion Weighted Imaging (DWI) provide?
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How can DWI information be visually represented?
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What is a significant difference between T1 and T2 images in MRI?
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What does the 'T' in T1 and T2 refer to?
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Which imaging method is primarily used for reconstructing directional information of diffusion patterns in the brain?
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Study Notes
Computerized Tomography (CT)
- CT is the preferred brain imaging method in scenarios where cost and speed are crucial.
- Rapid scanning is beneficial, especially in emergencies.
- MRI is contraindicated for patients with pacemakers, metal fragments, or who are agitated.
Magnetic Resonance Imaging (MRI)
- MRI offers superior spatial resolution compared to CT, producing clearer brain images.
- Detailed visualization of gyri and sulci, and better contrast between gray and white matter.
- Protons in the body align with a magnetic field during MRI scans, disrupted by radio frequency pulses.
MRI Mechanics
- Protons return to alignment post-pulse; a computer records alignment time and energy release.
- Data collected allows differentiation of tissue types such as bone, blood, and fluid, facilitating image creation.
- Modern MRI scanners achieve spatial resolution of millimeters.
Magnetic Resonance Spectroscopy (MRS)
- MRS evaluates metabolic activity through the levels of molecules like amino acids and glutamate in specific brain regions.
- Comparison between experimental and control groups helps assess metabolic differences.
Regions of Interest (ROIs) Analysis
- Early studies utilized volumetric analyses with manual tracing on MRI brain slices.
- Voxel-based morphometry (VBM) measures 3D pixels (voxels) for comparative volume analysis.
Structural vs. Functional Neuroimaging
- CT and MRI (including VBM) reveal brain structure at specific time points.
- Functional neuroimaging captures real-time brain activity.
- EEG provides electrical brain activity through scalp electrodes.
EEG Metrics
- Event-related potentials (ERPs) measure brain activity linked to specific stimuli.
- EEG and ERP have high temporal resolution but limited spatial resolution.
Functional Imaging Techniques
- Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) utilize radioactive tracers to highlight active brain areas.
- Active regions are identified based on tracer uptake during specific tasks.
MRI Scanner Strength
- Tesla (T) indicates magnetic field strength; higher fields yield sharper images.
- Clinical MRI scanners typically range from 1.5 to 3 T, while research scanners can go up to 7 T.
T1 vs. T2 Imaging
- T1 and T2 are sequences that affect proton relaxation times and image contrast.
- Fluid appears dark on T1 images and bright on T2 images.
FLAIR Imaging
- Fluid-attenuated inversion recovery (FLAIR) imaging suppresses cerebrospinal fluid signals to enhance detection of brain lesions.
Diffusion Weighted Imaging (DWI)
- DWI assesses white matter by tracking water diffusion across axon membranes.
- Directional diffusion information is used to create white matter maps (diffusion tractography).
Cognitive “Subtraction” Technique
- This technique compares complex tasks against simpler tasks to identify brain regions engaged in complex cognitive processes.
PET and SPECT Tracers
- Common PET tracer, [18F]–fluorodeoxyglucose (FDG), measures glucose metabolism indicating neural activity.
- Alzheimer’s disease often shows decreased FDG activity in the medial temporal lobe.
Radioligands
- Radioligands are attached to molecules, targeting specific receptors like acetylcholine or dopamine.
- Pittsburgh compound B (PIB) detects beta-amyloid deposition in the brain.
Functional MRI (fMRI)
- Blood oxygenation level dependent (BOLD) imaging tracks changes in blood oxygenation linked to neuronal activity.
- fMRI does not require radioactive tracers and is more widely accessible than PET.
Brain Changes with Aging
- "Last in, first out" concept: brain areas developing last are first affected by aging.
- Thinner myelin areas are more susceptible to age-related declines; overall brain volume decreases after age 30.
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Description
This quiz covers the critical aspects of Computerized Tomography (CT) as a method for brain imaging. It highlights scenarios where CT is preferred over MRI, including cost-effectiveness and rapid scanning requirements. Understand the implications of CT in patients with specific medical conditions.
