11. Brain Imaging Techniques Flashcards
MRI - general:
Non-acute indications
Indications: white matter (MS, no CM), tumors, degenerative, inflammation, AVM, vascular lesions, epilepsy, acute ischemia (DWI damaged cells = lower diffusion = higher signal)
MRI - Variations:
fMRI: localize functional areas
Predict return of function
Preoperatively to evaluate danger/safe zones
MRS: presence of substances
Proton spectroscopy - lactate, choline, creatine
P31 spectroscopy - AMP, ADP, ATP
Amount/Ratio various for each disease
MRI - Importance:
Superior soft tissue resolution
Better white/grey matter distinction
T1: fluid = dark, white matter brighter, anatomical structures
T2: fluid = bright, white matter darker, pathological (edema)
MRA: NO CONTRAST ToF, CE-MRA
MRS: metabolic concentrations
DTI: diffusion tensor imaging (white matter tracts)
CT - General:
Acute conditions (speed, availability)
Intracranial pathologies
CT - Indications:
Acute stroke: ischemic/ hemorrhagic
Hemorrhage = hyperdense
Trauma: intracranial bleeding + epidural/subdural hematoma
Calcifications, Brain tumors, Developmental abnormalities, Degenerative diseases, Vascular lesions
CT - Contrast:
Slice thickness: 2,5-5mm
- First unenhanced
If tumor, inflammation, vascular disease - Second contrast enhanced
CT - windowing:
Brain window: parenchyma, ventricular system
Bone window
CT - Description:
Brain: grey (white matter 40HU, grey matter 45HU)
CSF: black (0 HU)
Hyperdense: bone, calcifications, bleeding (70HU), metallic foreign body
Hypodense: ischemia
FLAIR: like T2, but CSF dark (black-black-white)
CT - types:
CTA: stenosis, aneurysm, AVM
CTA VRT: 3D reconstruction
CT perfusion: blood flow
Angiography:
Intracranial/extracranial arteries
Diagnosis: CTA/MRA
US: infants, cervical arteries
DSA: highly suspected vascular pathologies not found in non-invasive techniques
ALWAYS before endovascular treatment
CTA: first choice - acute SAH
Angiography - Indications:
Stenosis
Aneurysms
AVM
Fistula (Dural AV, Carotid-cavernous)
