Neuroimaging

• What are the principles of computerised tomography (CT) and structural magnetic resonance imaging (MRI)?

  They are imaging techniques used to visualize brain structures.
• What is the application of functional magnetic resonance imaging (fMRI)?

  It is used to assess brain activity by measuring blood flow changes.
• What does functional near-infrared spectroscopy (fNIRS) measure?

  It measures changes in blood oxygenation and deoxygenation.
• What is the purpose of positron emission tomography (PET)?

  It is used to detect biochemical changes in the brain.
• What is spatial resolution in neuroimaging?

  It refers to the level of detail in the spatial dimension of an image.
• Why is higher spatial resolution important in neuroimaging?

  It allows for the identification of specific brain structures.
• What does temporal resolution indicate in neuroimaging?

  It indicates the level of detail in the temporal dimension of an image.
• In which type of imaging is temporal resolution particularly important?

  Temporal resolution is particularly important in functional imaging.
• What is the purpose of structural imaging techniques?

  • Measures structural anatomy of the brain
  • Based on different physical properties of tissues
  • Constructs detailed static images of the brain
• How does a computerised tomography (CT) scan work?

  The patient's head is placed in a large ring containing an x-ray tube and detector.
• Why do different types of tissue absorb x-rays differently in a CT scan?

  More dense tissue absorbs more x-rays than less dense tissue.
• What does the appearance of areas of greater x-ray absorption indicate in a CT scan?

  They appear white, indicating denser tissues like the skull.
• What is a disadvantage of CT scans compared to MRI scans?

  CT scans typically have lower spatial resolution.
• What principle does magnetic resonance imaging (MRI) rely on?

  It is based on the behavior of hydrogen atoms in a magnetic field.
• How do protons behave in an MRI machine?

  Some protons align themselves with the magnetic field created by the MRI.
• What happens when a brief radio pulse is introduced in an MRI scan?

  It causes the aligned protons to change their orientation by 90 degrees.
• What is the purpose of scanning multiple slices in an MRI?

  To create a detailed image of the entire brain.
• What is a T1-weighted image in MRI?

  It is an image that distinguishes between different tissue types based on T1 relaxation time.
• How are T1-weighted images examined?

  They are examined in cross-sectional slices: horizontal, sagittal, and coronal.
• How does grey matter appear in a T1-weighted MRI scan?

  It appears dark grey.
• How does cerebrospinal fluid appear in a T1-weighted MRI scan?

  It appears black.
• What are white matter hyperintensities in MRI scans?

  They are lesions in the brain that show up as areas of increased brightness.
• How can white matter hyperintensities be related to health conditions?

  They can be associated with conditions like multiple sclerosis and cognitive decline.
• What is one advantage of MRI over CT scans?

  MRI can differentiate between white and grey matter.
• What are the key differences between structural MRI and CT scans?

  • Structural MRI provides detailed images based on hydrogen atoms in a magnetic field.
  • CT scans provide images based on differing densities of tissues.
  • MRI has better spatial resolution than CT.
  • Both are used clinically, but MRI is also used in research.
• What is the basis of functional imaging techniques?

  • They are based on the assumption that neural activity produces local physiological changes.
  • These changes can be reflected in dynamic maps of brain activity during cognitive tasks or at rest.
• What does the blood oxygen-level-dependent (BOLD) signal indicate in fMRI?

  It indicates the level of oxygen consumption in active brain regions.
• How does deoxyhaemoglobin affect the magnetic field in fMRI?

  It produces distortions in the magnetic field, indicating its concentration.
• What is the hemodynamic response function (HRF) in fMRI?

  It describes changes in the BOLD signal over time with three phases: initial dip, overcompensation, and undershoot.
• What is a limitation of fMRI regarding temporal resolution?

  It has relatively poor temporal resolution because the hemodynamic response is slow.
• How does functional near-infrared spectroscopy (fNIRS) measure brain activity?

  It detects changes in oxygenation and deoxygenation of blood through optical absorption.
• What age-related differences were found in brain activation during a balance task using fNIRS?

  Older adults showed more activation in certain frontal regions compared to younger adults.
• What does positron emission tomography (PET) measure?

  It measures biochemical changes taking place in the body.
• How does a radioactive isotope function in a PET scan?

  It is injected into the bloodstream and emits positrons as it breaks down.
• What is the temporal resolution of PET scans?

  Approximately 30 seconds.
• What are the key differences between functional imaging techniques like fMRI, fNIRS, and PET?

  • fMRI measures concentration of deoxyhaemoglobin in blood as a function of time (BOLD signal).
  • fNIRS detects changes in oxygenation of blood through optical absorption.
  • PET measures biochemical changes after a radioactive isotope is injected.