Neuroimaging Flashcards
(25 cards)
What does neuroimaging provide?
Allows for unobstructed imaging of the spinal cord and brain
-> Provides both anatomical and physiologic information
What does an axial view show?
Birds eye view (horizontal)
Runs parallel to the rostral-caudal axis
-> Viewing them from the feet
(Orientation is Opposite)
What does coronal view show?
divides the brain into anterior and posterior portions (frontal)
Viewing them as if you are talking to them
(Orientation is opposite)
What does a sagittal view show?
Divides the brain into right and left portions
What is an EEG?
Electroencephalogram
- Provides information on broad changes in electrical activity
- Used to diagnose seizures/impairments in sleep and wakefulness
Noninvasive
What is a TMS?
Transcranial Magnetic Stimulation
- Transiently (brief) modifies local brain activity
Ex: if someone is depressed, it can be used to increase activity
Noninvasive
What is a CT?
Computerized Tomography
- NONINVASIVE imagining using x-irradiation and computer processing to visualize the brain in 3D
- Creates a radio DENSITY matrix of the brain
Increased density -> White
Ex: Bone/metal/blood
Decreased density -> Black
Ex: Air/CSF/Ischemia (lack of oxygen)
Radiographic method
What does it mean if something is isodense?
SIMILAR density to reference structure
Related to CTs
What does it mean if something is hyper dense?
LIGHTER as compared to reference structure
Related to CTs
What does if mean if something is hypo dense?
DARKER as compared to reference structure
Related to CTs
What are the pros and cons of CTs?
Pros:
- Fast (takes about 5 min)
- Cheap (less expensive than MRI)
- More readily available than MRI
Cons:
- Radiation
- Difficult to perform in regions with large bone mass
- Resolution of several millimeters
What is a SPECT?
Single Photon Emission CT
- Provides 3D visualization of cerebral BLOOD FLOW using a radioactive tracer
- Increased blood flow noted in areas of high metabolic activity (seizure foci/tumors)
Looking at activity, rather than structures
Radiographic Method
What is a PET?
Positron Emission Tomography
- Uses indirect signs of neural activity, such as metabolic demand, to establish neural activity
-> Identifies areas of increased blood flow (increased oxygen and glucose)
- Injected radioactive isotopes are detected as they travel through the cerebral vasculature
- Measures metabolic demand at the cellular level
- Not widely used
Radiographic Method
What is an MRI?
Magnetic Resonance Imaging
- Uses magnetic fields and radio waves to detect hydrogen ions
- Described in relation to signal INTENSITY of a reference structure
What does it mean if something is Isointense ?
Similar density to brain tissue
Related to MRIs
What does it mean if something is Hyperintense ?
Lighter/brighter as compared to reference structure
Related to MRIs
What does it mean if something is Hypointense?
Darker as compared to reference structure
Related to MRIs
What are T1 MRIs?
T1- Weighted Images
- Increased contrast between grey and white matter
- Provide good ANATOMICAL detail
No bright white
What are T2 CTs?
T2- Weighted Images
- Fluids are highlighted (brighter)
- Pathologies more evident
Bright White
-> Ventricles are bright white from CSF
What are FLAIR MRIs?
Fluid-Attenuated Inversion Recovery
- Type of T2 image with CSF and vitreous fluid suppression
- Does not affect edema
- Ideal for viewing neural tissue edema
What are DTI MRIs?
Diffusion Tensor Imaging
- MRI variant used to illustrate white matter tracts
- Analyses the water diffusion patterns perpendicular and along the axons to create an image
Colorful pretty one
What are the pros and cons to MRIs?
Pros:
- safe (no radiation)
- noninvasive
- versatile
Cons:
- cannot be used with ferromagnetic objects
What is an fMRI?
Functional Magnetic Resonance Imaging
- Provides a dynamic signal in brain regions in which blood flow and oxygen use increases
- Concentration changes lead to localized blood oxygenation level-dependent changes in the magnetic resonance signal
- Produce maps of active brain region during task specific activities
What is a NIRS?
Functional Near-Infrared Spectroscopy
- Non invasive optical technique that allows for cerebral oxygenation to be examined during physical activity/exercise
-> Based on light absorption properties (hemoglobin)
- Portable/Low cost
- Repeat measurements feasible (no radioactive tracers)
