Flashcards in Neuroimaging Deck (23):
Brief changes in slow-wave EEG signal in response to a discrete sensory stimulus
Appearance of CT
White = dense (bone)
Black = less dense (air)
Dark gray (CSF)
Nearly black (fat tissue just outside skull)
Hyperdense = brighter areas
Hypodense = darker areas
Grey/isodense = intermediate density similar to brain tissue
Appearance of hemorrhage on CT
Hyperdense when fresh, becomes isodense after ~ a week, hypodense after ~ 2-3 weeks
MRI is better than CT in what situations?
Subtle tumor/infarct, brainstem lesion, old hemorrhage, anatomical detail
CT is better than MRI in what situations?
Head trauma, lower cost, fresh hemorrhage, speed, skull fracture, pacemaker
Appearance of MRI scans
Hyperintense = brighter areas
Hypointense = darker areas
The study of central nervous blood vessels & related cervicocerebral vasculature using radiographs during injection of IV contrast medium
Unidentifiable bright object
Refers to hyperintense white matter foci on MRIs (T2-weighted)
What might UBOs represent?
May be due to white matter pallor, infarction, ischemia, plaques or other causes
What is the differences between T1 and T2 MRI images?
T1 - white matter is brighter than gray matter
T2 = CSF is brighter than gray matter
Magnetic resonance spetroscopy (MRS)
Noninvasive technique used to measure chemical makeup of tissue (e.g., levels of neurotransmitters in the brain)
EEG changes in dementia
Nonspecific slowing is most common
Limitations of EEG
Unable to detect activity from deep cortical & subcortical structures
EEG - coherence
Degree to which respective regions' frequencies are correlated; often interpreted as a measure of "connectivity" between regions
What neuroimaging findings are most strongly related to AD severity?
Volumetric measures of medial temporal lobe & other cortical structures
Also has prognostic value for IDing progression from MCI to AD
How does IV contrast dye affect the appearance of CTs?
Contains iodine which is denser than brain & will appear hyperdense in areas of increased vascularity or breakdown of BBB
Iodinated contrast dye is introduced into CSF, allows better visual of nerve roots & abnormal impingement on spinal CSF
Describe the appearance of intracranial hemorrhage on MRI
Acute may be hard to see b/c resembles CSF
Subacute contains hemosiderin & appears white
Chronic contains dark areas resulting from hemosiderin deposits
Which MRI sequence is better for identifying anatomy: T1 or T2?
Which MRI sequence is better for clear differentiation of fluid: T1 or T2?
Diffusion tensor imaging
Depicts the directionality of water diffusion which is associated with meylin integrity
How do brain tumors appear on PET?
High-grade neoplasms demonstrated increased metabolism, low-grade neoplasms demonstrate decreased activity; radiation necrosis shows decreased activity & tumor recurrence shows increased