Neuro-Imaging Flashcards
Types of neuroimaging:
- CT
- MRI
- Cerebral angiography (MRA and CT angiography)
Which neuroimaging allows for in vivo visualization of orbits and intracranial contents:
CT and MRI
___ allows for clinicians to better view intracranial vasculatures.
Cerebral angiogrpahy (MRA and CT angio)
CT utilizes ___ and ___ based technology that images ___ objects as ___
X-ray; computer; 3D; slices
What is a limitation of CT? and name an example.
High attenuation of x-rays by bone (tissues within bone will have less detail)
Ex. skull base (post fossa and brainstem) > MRI preferable
CT: hypodensity is ___ and hyperdensity is ___. (CT = sity)
Dark; bright
CT, x-ray, and MRI: pts OD in on the ___ side.
Left
MRI has magnetic field gradient which forces protons in ___ to align.
H atoms
T/F: In MRI, radio frequency (RF) pulse disturbs the magnetically induced alignment.
T
Parameters of RF pulse:
Time echo (TE) Repetition time (TR)
___ IV contrast enhances vascular structures, BBB, and lesions.
Gadolinium
MRI types:
T1 weighted (longitudinal) T2 weighted (transverse)
T1 and T2 deals w ___, magnetization, and spin of ___.
Phasing; photons
In T1, TE and TR are set to ___ times.
Short
In T2, TE and TR are set to ___ times.
Long
T1 has exquisite detail and ___.
Anatomy
T2 emphasizes ___.
Pathological lesions
In T1, CSF and vitreous are dark or ___ signal intensity. (Hint: MRI = Intensity)
Low
In T2, CSF and vitreous are ___ or high signal ___.
Bright; intensity
MRI contraindications:
- Any electrically, magnetically, or mechanically activated (ex. hearing aids, insulin pump)
- Metal
- Intracranial aneurysm clips (unless made of titanium)
- Pregnancy
Indications for neuroimaging (orbit):
- VA loss (intracranial, pre/post chiasmal)
- Vascular lesions of orbit
- Hx of visual disturbances
- Optic nerve sheath meningioma
- Optic nerve neuritis
- Optic nerve glioma
- Tumors
- Unilateral proptosis
- Orbital abscess (pus)
- Inflammation
- Thyroid ophthalmopathy
- Extraocular myopathy
CT: ___ is bright due to high attenuation.
Bone
CT: Orbital fat and air sinuses appear dark due to ___ attenuation.
Least
CT: ___, ___, ___ have intermediate attenuation.
EOM, blood vessels, ON = GOOD
___ are the go to for CT.
Brain hemorrhages
MRI: Orbital fat is very ___ and obscures anatomical detail.
Bright
MRI: ___ suppression allows for better orbital detail.
Fat
___ > ___ if brain needs to be imaged.
MRI > CT
___ is better at imaging bone (ex. bone fractures).
CT
Both CT and MRI may be needed to characterize an ___ lesion.
Orbital
___ slices (3 mm apart) offers best orientation for orbit contents.
Always specify thin slices and coronal views for orbital imaging.
Coronal
Advantages of imaging brain w MRI:
- MRI better at imaging the ___ and ___ due to bone attenuation w CT.
- MRI distinguishes ___ and ___ matter w more resolution.
- MRI ___ are more equal.
- MRI can detect cortical ___ within hours.
- Image of choice for ___, MS, ___
- Post fossa and sella turcica
- White and gray
- Planes
- Infarcts
- Tumor, MS, and ischemic stroke
Disadvantage of MRI:
CT is cheaper, faster, less claustrophobic
Pathological processes normally increase water content in tissue which results in a signal increase in ___, ___, and ___.
FLAIR, STIR, DWI
Pathological processes are usually ___ and useful w FLAIR, STIR and DWI imaging techniques.
Brighter
T1 useful in differentiating brain’s ___, brain appears ___ gray, ___ has high intensity and ___ contrast can light up a tumor or abscess.
Parenchyma; medium; fat; gadolinium
In T2, brain appears ___ gray, edema are ___ spots, and useful for ___ pts.
Light; bright; MS
___ are sensitive to ___ and ___ abnormalities and useful for monitoring and detecting low grade ___.
FLAIR; edema and parenchymal; gliomas
___ helpful in confirming ishemic event.
DWI
___ used to image cerebral vasculature (aneurysms, vasculitis)
Cerebral angiography
Four vessel cerebral ___, MRA, CT ___.
Angiogram, angiography
