Neuroimaging Flashcards
What is angiography?
X-Ray imaging used in conjunction with radio-opaque dyes to visualize blood vessels in the brain
What is black and white on XRay?
White = bone (blocks most X-Ray particles) Black = structures containing air Grey = muscle, fat, fluid
When are XRays ordered?
To confirm head/skull injury (use contrast dyes to determine vascular malformations)
MOST COMMON METHOD FOR DETECTING FRACTURES (quick and portable)
What is a CT Scan?
A large series of 2 dimensional XRays taken around a single axis of rotation.
-High contrast resolution
-Dyes used for contrast (vascular imaging)
(Bucky Grid to force XRays in narrow column)
Back projection - subtracting the amount of energy of the beam coming out of the object from the beam coming in - absorption
Computer determines average density for each block within each slice.
Acute blood is denser than soft tissue
Water is denser than fat
Strengths and Weaknesses of CT Scan?
Strengths:
- Better is CASES OF TRAUMA
- Better bone detail
- Fast
- Detects acute hemorrhage
- CT is well-suited to pick up bone abnormalities
Weaknesses:
-CT is regarded as a moderate to high radiation diagnostic technique
What is a Mass Effect?
A distortion of the symmetry and shape of the brain due to a mass putting pressure on the brain and taking up space.
(Video game made by EA)
What is MRI?
.Uses magnets to detect signals from protons (positive charge - acts like a compass?)
H ion spins on own axis; creates magnetic dipole moment
**The stronger the magnet, the greater the # of H ions that will be induced to orient to it (stronger signal = stronger magnetic field = more H ions)
MRI = Map of difference mobile H concentration?
Pros and Cons of MRI?
Pro:
-Non-invasive
-Provides a clear definition of soft tissue
-MRI does not require injections due to protons found naturally in the body (unlike PET)
-MRI images provide greater detail than CT images
(MRI for soft tissue, CT for bone)
Cons:
- Confining test area
- Loud
- Patient must lie still
- Contraindicated for people with metal implants
CT vs MRI?
(MRI for soft tissue, CT for bone)
-CT relies on tissue density, MRI does NOT (it surveys location of hydrogen ions)
T1 vs T2
T1 uses short TR and TE
T2 uses long TR and TE
Flair sequences are becoming more popular (different version of T2)
LOOK AT CSF!
T1 = Dark CSF
T2 = Bright CSF
What is Transcranial Magnetic Stimulation?
Non-invasive method to excite neurons. Allows study of connections within the CNS.
-Weak electric currents induced in tissue by rapidly changing magnetic fields
-This causes either depolarization or hyperpolarization of neurons in the brain
TMS causes NO DISCOMFORT
- Electromagnetic coil used to active brain
- Coil held against skull over area of brain to be stimulated.
- Small electromagnetic pulses pass through skull and activate neurons
Depth of pulse is approximately 2 inches - specific brain areas can be targeted. This has allowed for brain mapping
What is Positional Emission Tomography?
FUNCTIONAL imaging technique
3-D Images of body PROCESSES
-A tracer of biologically active radionuclide is introduced to body and traced using an imager
-Concentrations of the radionuclide in the body can indicate increased tissue metabolic activity and can explore the possibility of cancer metastasis
What is Nerve Conduction Velocity (NCV)?
- Used to evaluae paresthesias and/or weakness in the upper and lower extremities
- This type of study is dependent on symptoms, thus tests are NOT performed without detailed physical exam and history
(Motor NCV and Sensory NCV both performed by eStim - Motor is recorded in muscle)
Common disorders diagnosed with NCV:
- Carpal tunnel syndrome
- Cubital tunnel syndrome
- Guillain-Barre syndrome
- Peripheral neuropathies
- Disc Herniation
Components of NCV studies include:
- Motor NCV
- Sensory NCV
- F-Wave studies
- H-Reflex studies
Latency = TIME
Amplitude = size of response
(both used to record Sensory NCV)
