Neuroimaging Flashcards
What is CT scanning
Utilizes ionizing radiation to produce an image
What is CT scanning based on
differential attenuation of tissue
What absorbs the least to most amount of an x-ray beam
Air, fat…soft tissue, water, then bone then metal absorbs the most
What is and what are the advantages of multidetector scanning
Small, high efficiency detectors in both x and z planes, multiple single slices studied at once,
Allow a VOLUME to be studied.
What are the advantages of CT
- Rapid image aquisition
- Widely available
- Can scan multiple body parts
- can give contrast!
What is the disadvantage to using a CT Myelogram
Can only identify extrinsic lesion compressing the cord
What are the disadvantages of a CT
- Uses ionizing radiation, important if cumulative
12. Contrast agent can produce renal problems
what are Hounsfield units?
Used to convert attenuation coefficient values to grey scale units.
Whiter pixels = higher HU values
what are some uses of a CT scan
- Fractures - good bony anatomy visualization
- Acute blood (like hemorrhage), Acute blood has a high density - appears white
(acute trauma)
What are some common features of an epidural hematoma
- Typically CN3 palsy (ipsilateral) and contralateral limb weakness
- middle meningeal arterial
- Lentiform shape
what does a hypodense subdural hematoma indicate
- Implies chronic bleed ! acute blood - white!
Where do cerebral contusions often occur?
Bifrontal cortex, at the grey/white matter junctions.
How does MRI work
Works on perturbing a precessing proton by radiofrequency, and the rate of relaxation back to its baseline state is measured
What is T1 relaxation
Spin-lattice relaxation time, relies on longitudinal relaxation - fat appears bright, fluid appears dark
What is T2 relaxation
Spin-spin relaxation?, relies on transverse relaxation, due to signal loss , fat is int-bright, fluid is bright
