MRI Flashcards
(250 cards)
White matter characteristics on T1W & T2W
Hypointense on T2 & Hyperintense on T1
Myelin contains membrane phospholipids which have rapid T2 relaxation –> “MR invisible”
NO lipid peak on spectroscopy therefore signal intensity determined by other factors (e.g - 12% less H20 than grey matter)
Demyelination lesions are T2 hyper intense compared to WM b/c of increased H20 protons in lesions
Exit of ophthalmic branch of trigeminal?
Orbital fissure
Exit of mandibular branch of trigeminal?
Oval foramen
Exit of maxillary branch of trigeminal?
Round foramen
Where is the rostral alar foramen located?
Level of hamuli of pterygoids
Where are the caudal alar foramen & oval foramen located?
Level of TMJ
What is contained within the oval foramen?
Mandibular branch of CrN 5
What is contained within the foramen lacerum?
Internal carotid artery
Where is the foramen lacerum located?
Rostral part of basioccipital & flanked by small bony processes from tympanic bulla
What is contained within the tympani-occipital fissure?
CrN 9, CrN 10, CrN 11
What is the internal opening in dogs of the tympani-occipital fissure?
Jugular foramen
What is contained within the stylomastoid foramen?
CrN 7
True or false, leptomeningeal enhancement extends into the cerebral sulci?
True!
But, pachymeningeal enhancement does not.
Contrast enhancement of the pachymeninges involves what structures?
Dura mater and adjacent periosteum, ‘dural’ enhancement
Contrast enhancement of the leptomeninges involves what structures?
Arachnoid & pia mater, ‘pial’ enhancement
True or false, meningoencephalitis is more likely to involve only supratentorial portions of the brain in comparison to neoplasia?
False! More likely to involve BOTH supratentorial and infratentorial portions.
Yorkies and French Bulldogs have been reported to get which type of disease process causing cerebral & brainstem subcortical white matter & cortical gray matter T2 hyperintense & T1 hypointense lesions with possible ringlike enhancement?
Necrotizing leukoencephalitis
What are the MR characteristics of chronic distemper meningoencephalitis?
- Bilaterally symmetric T2 hyperintense white matter lesions at junction of parietal & frontal lobes
- T2 hyperintensity of the arbor vitae –> loss of cerebellar gray-white matter junction
- T2 hyperintensity of caudal brainstem
- Pachymeningeal contrast enhancement
- Lesions NOT visible on T1 pre & post
What is the most common MRI finding of FIP?
Contrast enhancement of the meninges & ventricular lining.
(Histopath lesions = meningitis, ventriculitis, choroiditis, & periventricular vasculitis)
What are two differences between MRI findings of FIP versus other feline meningoencephalitis?
1) Meningeal, ependymal, or periventricular mild to moderate contrast enhancement
2) If present, parenchymal lesions have distinct margins
What locations are most commonly affected by cryptococcosis fungal meningoencephalitis?
Frontal & olfactory lobes
What are the two categories of MRI lesions of Blastomycosis?
1) Mass lesions
2) Ependymal & ventricular changes
What is unique about focal mass like lesions from Blastomycosis?
Some have been reported to be T2 iso- or hypointense, although most are T2 hyperintense/T1 hypo- or isointense
What are 2 diseases with lesions that may be T2 iso- or hypointense & T1 hyperintense?
1) Blastomycosis
2) Cryptococcus