10) Imaging Flashcards
Advantages of MRI
- No ionizing radiation
- Contrast dye usually doesn’t cause side effects
- Non-invasive
- Great resolution & contrast regardless of tissue thickness
- Good detail even w/out contrast
- Works in any plane
Disadvantages of MRI
- Can’t do if pt has metal in their body
- Can’t do on pregnant women
- Not good for looking at bone
- Some pt’s are claustrophobic
- Obese pt’s can’t fit in the machine
- Kids will prob need to be sedated
- Pt needs to stay completely still
- Noisy
- Expensive
- Time-consuming
- Sometimes there’s a waitlist
MRA
Used to image blood vessels to eval for stenosis, aneurysms, AVM, etc
fMRI
Displays metabolic activity of the brain by measuring the BOLD level Hgb)
Why does fMRI work?
Hgb is dimagnetic when oxygenated, but paramagnetic when deoxygenated so imaging results change based on O2 levels
Strengths of fMRI
- Non-invasive
- Replicable
- Good spatial localization
- Well validated
Limitations of fMRI
- Mediocre temporal resolution
- Complex & highly variable analyses
- Time consuming
- Expensive
EEG
Detects electrical activity in the brain using electrodes placed on the scalp to dx epilepsy & sleep disorders
True or False: EEG is non-invasive but isn’t as spatially accurate as fMRI is.
True
PET scan
Maps brain fxn’ w/injectable tracers to look at glucose metabolism in the brain to detect CA, dementia, & seizures
Strengths of PET scan
- Simple physiologic mechanism
- Provides absolute, quantitative data
- Allows imaging of anything that can be tagged
Limitations of PET scan
- Poor temporal & spatial resolution
* Requires radioactive injections
How does MRI work?
Pt gets injected w/contrast dye & the dye moves around at different speeds
What is MRI good at dx’ing?
- MS
- Strokes
- Neuro infections
- Tumors
- Tendonitis
- Torn ligaments
- Disc problems
W/a T1 weighted MRI, how will tissues w/fluids & tissues w/fat appear?
Tissues w/fluid=Dark
Tissues w/fat=Bright
W/a T2 weighted MRI, how will tissues w/fluids & tissues w/fat appear?
Tissues w/fluid=Bright
Tissues w/fat=Dark
Why is T2-weighted MRI good for looking at pathologies?
Bc damaged tissues tend to devo edema, so the area will be illuminated
What is a CT scan good for?
Looking at the brain
What can be used to make organs more visable on a CT scan?
Contrast dye
On a CT scan, what color will bone, tissues, & liquids/gases be?
Bone=White
Tissue=Gray
Gasses & Liquids=Black
What does a CT scan image correspond to?
3D section of the pt
True or False: CT scans look at structure rather than fxn.
True
