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CCC RadioimagBrain

Radioimaging of Brain and brainstem

QuestionAnswer
Advantages of CT Very fast imaging…seconds to minutes. (emergency situations) Post-processing reconstruction in multiple planes. Called multiplanar reconstruction (MPR) Patient does not have to be present Can be used in patients with implanted devices (unlike MRI).
Disadvantage of CT Uses ionizing radiation (x-rays)
What are HUs? Hounsfield Units (H.U.) Density measurement of a chosen area. 4,096 different shades of grey from pure white to pure black (+3071 to -1,024 Hounsfield units).
HUs of Gray vs. White? Gray-35 HU White 25 HU
Hypodense vs. Hyperdense vs Isodense Hypodense = decreased attenuation = dark Isodense = same attenuation Hyperdense = increased attenuation = white
CT requires contrast? no, can be done with or without
Why are CT contrasts used? Iodinated contrast agent injected I.V. (or intra-arterial). …Iodine molecules attenuate x-rays = white …Identify vasculature and vascularity. …Normal & abnormal tissues enhance differently.
What are contrast problems with CT Potential problems rare: Allergic reaction Renal dysfunction
CSF vs. gray matter which is more attenuated (higher)? gray
Skull is low or high density? high
MRI made via what ? magnetic field and radiofrequency
What is a high signal seen as? bright (white)
What is low signal seen as? dark
Advantages of MRI Don't need iodinated contrast agent Great detail of soft tissue Can scan in any plane No ionizing radiation, so pretty safe
What contrast agent is occasionally used in MRI? Gadolinium
Disadvantages of MRI Scan time is long, so some pts automatically can't use it Implanted devices could malfunction Magnetic metals in pt? MRI can't be used
MRI: T1 CSF is low signal
MRI: T2 CSF is high signal
MRI: Pathology T2 or T1? T2-most pathology has higher water content
MRI: Flair Keeps CSF dark, but its a pathological finding of MRI
MRI: diffusion sequences Very early ischemic stroke detection
White areas of MRI= High signal
Created by: VCOM2013
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