MRI Flashcards
What is MRI ?
A diagnostic imaging modality using magnetic resonance technology
Was renamed MRI due to the word “nuclear” in what year ?
1980 s
The 1st MRI units were sold commercially ?
1984
How does MRI work ?
By Magnet , Nuclei (Protons) and Radio Frequency
Magnet ?
The earth’s magnetic field is about 0.5 gauss
MRI : 0.5 tesla , 1 tesla , 1.5 tesla and 3 tesla
MRI measurements ?
Gauss: unit used in the measurement of a low magnetic field strength
Tesla (T) : unit used in the measurement of a high magnetic field strength
Radio frequency ( RF) :
It is a radio waves and use to excite the protons
RF coils ?
Coils send and receive RF signals,
come in various shapes and sizes
and work best when placed close to the scanned body part
Magnetic strength ?
Earth’s magnetic field = 0.5 Gauss
Which 1.5 Tesla magnet is 15,000 Gauss about 30,000 times stronger than Earth’s 0.5 Gauss of magnetic field
what are screening form ?
Pacemaker
Cerebral Aneurysm clips
Implanted electromagnetic devices
Cochlear implants
Metal fragment in body
Pregnancy
Pregnant patient in MRI ?
Not known biological effects on fetus
Not recommended 1st trimester
Pregnant employee ?
Technologist should set up the patient, but not to remain in the room during image acquisition
Advantages of MRI ?
Non Ionizing Radiation
Minimal Preparation Time
Multi Plane Imaging
Soft Tissue Detail
What are multi plane imaging ?
Axial , Coronal , Sagittal , Oblique and
3D Reconstruction
Soft tissue detail ?
MRI is capable of imaging muscles, tendons, ligaments and tumors
MR angiography ?
Method of visualizing vessels
Non-invasive procedure
No contrast media
Disadvantages of MRI ?
High cost , patient Size , patient screening ,
Claustrophobia
Sensitive To Motion and Slower Modality
Patient can have an mrI when ?
Patient with Pacemaker, aneurysm clips, cochlear implant and Trauma
Patient cooperation can have MRI
Slower modality ?
Takes a longer time to perform compared to CT exams
Average 20-45 minutes
Patient size ?
Table weight limit is 300 pounds , 130
Some patient are unable to fit in the scanner due to their size ( open MRI is an option)
Claustrophobia
As many as 20% of patients cannot complete the scan due to claustrophobia
what modality sensitive to motion ?
MRI
Sensitive to motion ?
Due to the length of the exam, it may be difficult for patients to hold still
Pain , Discomfort and Uncooperative
Patient monitoring equipment ?
Only MRI compatible equipment are allowed in the scan room
There is MRI compatible equipment for Anesthesia cases
