Radiology II Flashcards
the MRI can be used to image what elements?
which element does it image in medicine?
why?
- can be used to image any element with an odd number of protons
- in medicine, it is tailored to image / manipulate H+ (one proton)
- this is b/c there are so many H+ atoms in the body
hydrogen is in what state when bound to a molecule within body tissues?
which body tissues most dense in hydrogem?
- when bound: H+ goes from having 1 elecron + 1 proton to just 1 proton.
- tissues most abundant with H+: water, fat
what is the significance of a spinning proton?
the spinning positive charge creates a tiny electrical current
how does hydrogen behave organically vs in the presence of an external magnetic field?
why is this important?
- no external magnetic field:
- protons oreinted different directions
- their individual electric signals cancel out
- external magentic field (in an MRI):
- protons align (either parallel or antiparallel)
- this generates magnetic field
how is an image generated from aligned protons in an MRI?
- a radiofrequency (RF) pulse is sent onto, inducing protons to temporal change their alignments
- the new spinning magnetic field produce an electrical signal
- this electrical signal is detected by a antenna (coil) then mapped into an image
what are TE and TR?
- TE (echo time): time between sending RF pulse and measuring the signal
- TR (reptition time): time between successive RF pulses
what is the difference between T1 and T2 weighted signals?
- T1: fat is white
- T2: fat AND fluid (CSF, for example) are white
label
T1 vs T2?
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cerebellar tonsils
T1 (fluid is dark)
label
T1 vs T2?
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cerebellar tonsils
T2 (eye fluid is white)
tonsillar herniation
- definition
- causes
- when tonsils pass inferior to foramen magnum
- causes:
- Chiari I malformation, often associated w/ syrnix - congenital, mild
- intracranial hemorrhage - acquired, life threatning
- tumor - aqcuired, life threatning
identify
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tonsilar herniation (inf to foramen magnum)
d/t chiari I malformation
identify
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tonsillar herniation (inf to foramen magnum)
d/t posterior fossa tumor
label
T1 vs T2
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label
T1 vs T2
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T2
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label
T1 vs T2
middle cerebellar peduncle
T2
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how does multiple sclerosis appear on an MRI
- T2 intense plaques (lesions) within white matter, which if often:
- radiating perpendendicular from lateral ventricles
- within the corpus collosum
- in middle cerebellar peduncle
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identify
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multiple sclerosis
plaque (lesion) perpendicular from lateral ventricle
identify
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multiple sclerosis
plaque (lesions) perpendicular from lateral ventricles
identify
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multiple sclerosis
plaque (lesion) in corpus collosum
identify
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multiple sclerosis
plaque (lesion) in the middle cerebellar peduncle
label
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identify
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uncal herniation
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hippocampus
hippocampus atrophy - cause?
Athzheimers, commonly
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identify
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atrophied hippocampus
Alzheimers
label
T1 vs T2?
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identify
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epidural hemoatoma
(lens shape)
parkinson’s affects what part of the brain?
the substantia nigra
label
T1 or T2?
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T2
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label
T1 vs T2?
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chronic lacunar infarction
- definition?
- presentation?
- cause: ischemic stroke to the caudate nucleus
- presentation: memory loss
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identify
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chronic lacunar infarction
identify
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chronic lacunar infarction
identify
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chronic lacunar infarction
label
T1 vs T2
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acute cerebral infarction
- presents how on MRI?
- and why?
- how soon after event?
- with what kind of imaging?
- presents with with T2-hyperintensity
- d/t restircted water movement b/c of
- lack of blood flow
- cytotoxic edema
- seen as soon as pt appears for care
- on diffusion waited imaging
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how does an acute cerebral infarction present on CT as opposed to MRI?
- with ribbon like insular cortex
- not for several hours after event
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identify
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acute cerebral infarction - MRI
T2-hyperintensity on diffusion weighted imaging
identify
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acute cerebral infarction - CT
ribbon like insular cortex
identify
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ependiymitis granularis
- a normal variant of ventricular ependyma that has
- less myelin
- increased ECF
- some ependymal degeneration
label
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what is a “midfline shift”?
what is it caused by?
- aka subfalcine herniation
- a mass effect on one side of the brain cause a shift of the septum pellucidum away from the midline towards the opposite side
- ex - subdural hematoma
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identify
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subfalcine herniation
in this case, due to subdural hematoma (cresent shape)
first is T1, second is T2
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label
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label
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hydrocephalus
- cause
- variations
- presentation on MRI
- cause: abnormal increased CSF volume
- presentation on MRI: ventromegaly
- variations: non-communicating (no visible obstruction), communicating (visible obstruction)
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how does normal pressure hydrocephalus present?
“wacky, wobby & wet”
- dementia (wacky)
- wobby (ataxia)
- wet (urinary incontinence)
label
T1 vs T2?
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label
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pituitary adenomas are divided into what two main types?
how do they differ?
- microadenomas (<1 cm): can produce hormones
- macroadenomas (>1 cm): can produce hormones & exert significant mass effect?
how are macroadenomas typically discovered?
how are they treated?
- by growing large enough to compress the optic chiasm and result in visual symptoms
- treatment: bromocriptine
identify
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pituitary microadenoma
label
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label
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identify
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cerebral aneurysm
identify
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