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