MRI Flashcards
MRI stands for
Magnetic Resonance Imaging
MRI came into existence in the early
1980s
Based on the principles of magnetic spectroscopy which is
the use of a magnetic field and radio frequencies to determine the chemical makeup of a substance
indications for MRI
found in speciality vets, superior for demonstrating spinal cord, brain, and soft tissue structures like ligaments and cartilage in joints, desired modality since no radiation
Magnets like those used in MRI scanners are
very dangerous
Everyone entering an MRI room must be screened for
unsafe implants and any loose metal
highest danger to staff and patients is the
projectile effect- the launching of a metallic object into the magnet by magnetic force
Gauss (G)
imperial unit of measurement for magnetism
Tesla (T)
most common measure of magnetism
1T= _G
10,000
Permanent magnets
two slabs of magnetic material facing each other; rend to be lower magnetic field strengths less than 0.3T
electromagnetic or restive magnets
created by an electrical charge applied through copper wire wrapped around the center. also tend to be lower field magnets less than 0.6T
superconducting magnets
massive electromagnets made of windings that are superconductive in very low temperatures. Most common. Liquid helium used to keep magnet active
If part of the image as shown as bright or closer to white, it is described as having
a high signal intensity
The reverse is true for anatomy seen in darker shades of gray; they are called
low signal intensity
The goal in acquiring MRI images is to have a
high signal to noise ratio, higher amount of signal, better pictures
is it possible to use MRI to image blood vessels without a contrast agent?
yes
The contrast agent used for MRI is called
gadolinium
What should be done before using gadolinium
P’s kidney function should be assessed because gadolinium is removed by the kidneys
_ are often required by specialty practices before an MRI is performed
Referrals
_ and _ required for MRI
anesthesia or sedation
An MRI scan always starts with a low quality quick image called a
localizer
Ferromagnetic shifting
containing metal implanted into a patient may move out of position with exposure to the magnetic field
Heating of implanted metal that can cause
burning of the patient
Assessment for MRI
checklist filled out by owner and pre-MRI x-ray if unsure of hx or possibility of pellets/bullets
Specific absorption rate (SAR)
because animals cannot dissipate or radiate the heat from the radio waves in the same way as humans do through perspiration, cooling pack should be applied to dogs who are larger with less surface area
Noise amount in decibels for MRI
60-90+
