28.Neuro_Imaging Flashcards
disadvantages of radiographs for neuro imaging
–limited contrast resolution–summation of superimposed structures
benefits of radiographs for neuro imaging
–cheap–available–easy–global perspective (congenital anomalies, vertebral instability)–HIGHEST spatial resolution (ID lysis)
where does myelography inject contrast fluid into
SUBarachnoid spaceiodinated contrast materialcan be performed with CT
what is contrast resolution
ability to discriminate tissues of differing compositionsMRI is the gold standard, followed by CT
what is spatial resolution
ability to define fine detail CT superior to MRI
bone imaging on MRI
poor spatial resolution (CT IS BETTER)Cortical bone lacks hydrogen protons, thus, has no signalBONE IS BLACK ON MRI IMAGESif infiltrative bone disease, MRI may be better bc when ST infiltrates contrast resolution of MRI may be better
hounsfield units of fat vs bone/mineral vs water vs hemorrhage on CT
Water: 0FAT: HU -100 hypoattenuatingHemorrhage: HU 60-100Bone/mineral: HU 100->1000 hyperattenuating
contrast medium used in CT vs MRI
CT–iodinated basedMRI–gadolinium based
radiographs, CT, MRI terms to describe brightness
radiographs—opacityCT—attenuation or densityMRI–intensity
what does a golf tee sign indicate
intradural but extra medullary lesion
difference btwn T1 and T2 images on MRI
T1W: shows good anatomic detaillong relax —fluid is BLACK/HYPOINTENSEshort relax—fat, MetHb stage of hemorrhage, Protein fluids (mucin), melanin are BRIGHT/HYPERINTENSET2W: more sensitive for pathology long relax: fluid (edema, CSF, necrosis, cell infiltrate, demyelin) is BRIGHT/HYPERINTENSE
contrast media does not normally enter brain parenchyma bc of an intact BBB. What happens when the barrier’s integrity is loss
vasogenic edema, but contrast does not follow it into the parenchyma well edema travels along the white matter tracts more readilyhypoattenuating on CThypointense on T1W MRIhyperintense on T2W MRI
2 incidental or normal variation seen in brain MRI
- brachy breeds may lack septum which leads to lack of separation of the rostral aspect of the lateral ventricles)2. age variations–enlargement of ventricles and subarachnoid space w age–ex vacuo effect w signal intensity reversal in young; returns to normal as myelination of white matter occurs w age (16wk)
secondary pathologic changes detected on advanced imaging
–vasogenic cerebral edema –perilesional–syringomyelia–ventriculomegaly–hydrocephalous from obstruction –mass like effects–compression of surrounding structurescan be reversible; variable recovery time
clues on extra-axial lesion identification on MR
–broad base along dura or calvarium–dural tail–cleft of CSF btwn lesion and brain–adjacent hyperostosis or remodeling of skull–buckling of grey/white matter junction (?)
