The flashcards below were created by user
on FreezingBlue Flashcards.
What two interactions does MRI use to create
- Magnetic fields
- Radio waves
What type of protons in the body are used in MRI
calculations and why?
Hydrogen protons because they are the most numerous and have the strongest magnetic properties.
What is a significant advantage of MRI over CT
and diagnostic radiography?
No ionizing radiation is used in MRI.
When did MRI generally become operational?
What happens to hydrogen protons when placed in a strong, uniform magnetic field?
They line up parallel to the direction of the magnetic field
In terms of the hydrogen protons being affected by a magnetic field, what does “precession” mean?
Precession is the wobbling motion of the hydrogen protons as they line up with the magnetic field.
What is “resonance” in regards to MRI?
Resonance is the absorption of energy by the precessing protons when exposed to radio waves of the same frequency
What are the (3) primary MRI system components?
- Magnet(MAJOR COMPONENT)
Name and describe the types of magnets used in
various MRI systems?
- 1) Permanent
- - magnetized ceramic blocks
- - magnetic field up to 0.3T
- - lower operating cost
- 2) Resistive
- - large electromagnet with electric
- current flowing through coil of wire
- - electrical resistance produces heat
- limiting maximum magnetic strength
- - magnetic field up to 0.3T
- 3) Superconductive
- - electromagne
- - cryogenic: cooled by liquid helium
- and nitrogen
- - permits much stronger magnetic
- field; standard is 1.5T
What are the two primary types of MRI systems?
Briefly describe their characteristics.
- 1) Closed
- - original and still most prevalent
- - superconductive with higher magnetic field strength
- - generally provides best images
- - faster
- - claustrophobia can be a problem
- 2) Open
- - new innovation to combat claustrophobia
- - generally lower magnetic field strength - < 1.0T
What is a MRI coil?
Term for antenna that picks up signal
What image planes can MRI perform while the
patient is in the magnet?
Is MRI considered safe for patients and
Yes, no known adverse effects.
List MRI hazards and precautions.
- Ferrous (metal objects)
- Metal implants
- Internal electronic equipment
- Wires from EEG/ECG can cause burns
- Loud noise from magnet
- Loss of liquid helium/nitrogen
List MRI contraindications.
- Neurostimulators/bone growth
- Internal/external electrical pumps
- Brain aneurysm clips
- Some metal implants
- Metal splinters in eyes
What is the primary contrast agent used in MRI? What
is its primary purpose?
What are its contraindications?
- Gadolinium. Enhances visualization of tumors and scar tissue in T-1 weighted images.
- No known contraindications.
- Recently linked to cause nephrogenic systemic fibrosis (NSF) in patients with advanced kidney disease
What is MRI?
A computer based cross sectional image modality using the interaction of magnetic fields and radio waves to create images.
What does cryogenic mean?
Cooled by liquid helium and nitrogen
What is MRI used for?
- Imaging soft tissue
What measures metabolic changes within the active part of the brain to determine the location of various functions?
- fMRI-Function MRI
- Diagnostic method for learning how normal, diseased, or injured brain is working–
- Used to identify
- Brain tumors
- Abnormalities related to dementia or seizures.
What happens as the field strength becomes greater?
The faster the exam and the better the images
What is T1 better to look at?
What is T2 better known to look at?
What helps computers to determine slices
What is the standard tesla?
When does contrast media primarily show up?
in T1 exams
What is quinch?
- Loss of liquid gases
- Not poisonous but displaces oxygen