14. Intro to Neuroradiology Flashcards
List the imaging modalities available for neurological imaging.
- Radiography (X-Ray)
- Fluoroscopy
- Ultrasound
- ComputedTomography(CT)
- Magnetic Resonance (MR)
Explain how computed tomography creates images and how these images are read (e.g. are cross sections viewed from an inferior or superior view).
CT takes a. series of X-rays that are scanned axially and then lets you digitally re-slive in image in ANY place.
Describe the Hounsfield scale and how adjustments can be made so different tissues and anomalies can best be viewed (e.g. compare a soft tissue window vs a bone window).
- When looking at CT’s, we measure the radiodensity because we are measuring the absorbed radiation. Radiodensity is measured in Hounsfields units (HU) relative to water, which is 0 HU.
- Hypodense: white/bright
- Hyperdense: black/dark
Describe the Hounsfield scale and how adjustments can be made so different tissues and anomalies can best be viewed (e.g. compare a soft tissue window vs a bone window).
To look at tissue or bone, you can adjust the window and level.
-
Window is the width of the HU.
- Wider windows are used to compare areas with different HU (bone vs. air),
- Smaller windows are used to measure things with similar H.Us (brain vs. blood)
- Level is the center of the window.
Window of bones, air and tissue?
- +1000 HU
- -1000 HU
- +30-40
Bone window: most common
W: 1000HU L:400HU
Soft tissue window: most common
W:350HU
L:40HU
Explain how magnetic resonance imaging is utilized to produce an image.
- Patients lies in a large magnet, which aligns all the protons (i.e. Hydrogen or water molecules) in the body
- Radiowaves are then passed through the patient and returning signals are converted into an image.
How do we describe MRIs?
- Hyperintense: white/bright
- Hypointense: black/dark
Explain the difference between T1 and T2 weighted MR.
T1 is good for looking at anatomy.
- CSF is dark (hypointense)
- White matter is bright (hyperintense)
T2
- CSF is bright (hyperintense)
- White matter is dark. (hypointense)
What is a T2 FLAIR (FLuid Attenuated Inversion Recovery)?
Removes CSF from a T2 image and leave you with soft tissue.
This enhances the fluid that is NOT CSF; that with a different protein coponent.
This is good for looking at edema and strokes.
Identify the primary differences between plain film X-ray and fluoroscopy and when one is preferred over the other.
- Fluoscopy has the same process as a X-ray. However, it is a real time x-ray.
- Continuous X-ray radiation passes through the body only a fluroscent screen to creat. a. moveing X-ray image.
- Also causes contrast
Identify the primary differences between plain film X-ray and fluoroscopy and when one is preferred over the other.
Xrays: use for
- trauma (fracture),
- degenerative diseases (RA),
- post-op checks
Fluroscopy: used for
-
diagnosis and intervention;
- swallow studies,
- angiography
- myelography
List the different types of contrast used in neurological imaging.
Base?
Fx:
Cons:
- CT contrast is iodine based.
- absorbs X rays
- Con: risk of anaphylaxis, allergic reactions or contrast induced neuropathy
- MRI contrast is gadolinium based
* Gadolinium is a paramagnetic metal that increases T1 relaxation of nearby water
protons (bright on MRI).
- Cons: If a person has renal insuffiency and gadolinium is aborbed by. kidneys -> causes systemic fibrosis
what structures are enhanced with IV contrast.
REMEMBER: only tissue that gets brighter with CONTRAST enhances; it reflects that vascularity of the tissue.
- Cerebral blood vessels
- Meninges
- Pineal gland
- Pituiary. gland
- Choroid plexus
- Use when performing fluroscopy
When do we do CT w or w/o contrast
- Non-contrast CT use used in patients with head/spine trauma or acute stroke. It is the fastest test in MRGNC situations. It is the preferred test within 3 hours of acute symptom onset.
- Contrast CT is used when sx last longer than 3 hours: neoplasm, infection, vascular disease, inflammatory disease.
YES OR NO CT WITH IV CONTRAST
- Trauma
- neoplasm
- infection
- Rule out Hemorrhage
- vascular disease
- Hydrocephalus
- Dementia
- inflammatory disease
- Epilepsy
NO IV contrast:
- Trauma
- Rule out Hemorrhage
- Hydrocephalus
- Dementia
- Epilepsy
YES IV contrast:
- Neoplasm
- infection
- Vascular disease
- Inflammartory disease
What. happens if brain parenchyma is enhanced
- Enhancement in brain parenchyma is indicative the BBB is absent or dysfunctional (tumors, inflammation, infarction).
Compare and contrast the various neuroimaging modalities in regards to indications, advantages and disadvantages.
- Xrays (radiography)
- Use for:
- Pro:
- Con:
- Fluroscopy (barium swallow, angiography, myelography)
X rays are used for: trauma (fractures), degenerative diseases, post-op checks
Pro: cheap and fast
Cons: uses radiation and cant see detail of soft tissue
Fluorscopy:
- Barium swallow test
- Used: dysphagia, epigastric pain, GERD
- Pro: shows us live swallowing
- Cons: time consuming, uses contrast, radiation
- Angiography
- Used: aneurisms, vascular malformations, stenosis, thrombosis, stenting, embolization, thrombylysis
- Pro: can intervene and fast
- Con: invasive, uses contrast. and radiation
- Myelography (cervical or lumbar puncture to inject contrast -> follow with CT to eval)
- Used for: spinal stenosis, nerve root compression, CSF leak, if MRI is contraindicated
- Pro: defines our subarachnoid space and identifies spinal block
- Cons: invasive, complications (CSF leak-> HA), radiation (bc must follow up with CT) , contrast
Compare and contrast the various neuroimaging modalities in regards to indications, advantages and disadvantages.
US
Use for:
Pro:
Con:
Use for: carotid stenosis, brain imaging for BBs
Pro: non-invasive, cheap and fast. Quantitates blood velocity
Con: operator must learn to use with experience, limited penetration through air or bone
Compare and contrast the various neuroimaging modalities in regards to indications, advantages and disadvantages.
CT
Use for:
Pro:
Con:
Used for:
- Trauma, bone lesions of skull and vertebrea
- Ventricles: Hydrocephalus, masses, mass effect
- Intracrania lmasses,mass effect; if pt comes in with N/V, HA, vzn problems
- Hemorrhage, ischemia (stroke, mental status change,
- Calcification
Pros: FAST and Cheap
Cons:
- Less detail
- Radiation
- Low sensitivity in posterior fossa
MRI
Used for:
Pros:
Cons:
Used for:
- further evaluate findings in CT;
- chronic, subacute sx
- Tumors, masses
- Infections (absess, meningitis, encephalitiis
Pro: more detail, safe in pregnancy, no constrast
Cons: slower, more contraindications (metal in body), expensive, patient must hold still
What provides the GREATEST AMOUNT OF DETAIL (better than contrast enhanced CT when evaluating ischemia)?
MRI
What is the most beneficial for ruling out large pathology (bleed, large ischemic stroke, mass, abscess, hydrocephalus)?
CT; bc fast and cheap.
However, MRI provides the greatest detail, just is slower, more contraindications, expensive.
