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Terms in this set (81)
Who first discovered properties of MR? When?
Block and Purcell in the 1940's
Who was jointly awarded a Nobel Prize in physics in 1952?
Block and Purcell
Who published the first cross-sectional images produced with MRI? When?
Who showed signals could be mathematically analyzed and faster imaging?
Who was jointly awarded a Nobel Prize in Physiology? When?
Lauterbur and Mansfield in 2003
NMR stands for
Nuclear Magnetic Resonance
MRI stands for
Magnetic Resonance Imaging
Creation of the MR signal is done by -
Induction of current into a receiver coil by the precessing magnetization
Anatomical part is placed -
In the field/Bore of the magnet
_______________ line up and precess.
spin like tops/wobble
____________ ______________ pulses are passed through precessing protons.
If the Radio frequency pulses passed through the precessing protons are the same frequency, it will cause -
the energy to be absorbed through the process of resonance.
What occurs as the excited nuclei return to their normal, unexcited state?
Relaxation (T1, T2)
During the relaxation process the signals (energy release) is picked up by-
Computer converts -
signals to images
T1 or T2 determines-
Signal is proportional to -
# of protons present
MRI signal intensity depends on-
relaxation times of the nuclei
release of energy by the excited protons, which occur at different rates in different tissues.
Excited nuclei relax through what two processes?
1) T1 Spin Lattice Relaxation
2) T2 Spin Spin Relaxation
T1 Spin Lattice Relaxation the excited nuclei releases energy to-
the general environment or Lattice
T1 Spin Lattice Relaxation is measured in -
Short T1(fast spin lattice relaxation rate) produces -
high MRI signal
How does a high MRI signal show on and MRI?
How would a low/weak MRI signal show on MRI?
T2 Spin Spin Relaxation is the release of energy by an excited nuclei through -
interaction among themselves
Long T2 (slow spin-spin relaxation rate) produces -
Two types of electromagnets
Electromagnets are surrounded by
Simple but large electromagnets consisting of coils of wire which cause electrical resistance of the wire.
Resistive magnets resemble -
solenoid with coils
Resistive Magnets are limited with -
What is a potential problem of Resistive Magnets?
Resistive Magnets magnetive field strenghth generally does not exceed -
or (0.6 Tesla according to the book)
Electromagnet with wire loops that are cooled with liquid helium which decreases teh wire's resistance
Field Strength of Super conducting Magnet
Magnet with a constant field that does not requre additional electricity or cooling
Permanent Magnets are usually very -
Fringe fields (magnetic field) of a Perment Magnet
Do not extend as far away from the magnet as do fields of other types of magnets.
Field Strength of Permanent Magnet
Generally do not exceed 0.3 Tesla
Magnetic Field Strenghth is measured in
Tesla or Gauss
Magnetic Field Strength of most MRI's
range from 0.2 to 0.3 tesla
1 Tesla = ______ Gauss
device for transmitting or receiving radio waves
spurious finding in or distortiion of an image
reduction in energy or amount beam of radiation passing through tissues
single or multiple loops of wire designed to produce a magnetic field
degree of difference between two substances in some parameter, with the parameter varying depending on the technique used
relating to extremely low temperature
spontaneous random motion of molecules in a medium
echo planor imaging
fast pulse sequence that can be used to create MR images within a few seconds
images in which the fat tissue in the image is made to be of lower, darker signal intensity
The first MRI exam on a human was performed in
The most important element in the body for MRI imaging
MRI system uses
Radio Frequency pule to change the spin of the atom's nuclei
most common type of magent used in MRI
They MRI System creates images when
hydrogen atoms go back to normal position, releasing energy
the system used to convert mathematical data into one image
to generate an MR image, technologist select a group of scanning parameters known as
coils are used to
transmit RF pulse and receive the MRI signals
Most commonly used cryogen
Other than helium, an option for a cryogen
Purpose of cryogen
to cool the magnet
To turn off the magnetic field as quickly as possible
The process of a Quench
Cryogen is warmed up which causes helium to expand
Precautions and Dangers of performing a quench
asphyxiation and freezing
cost of performing a quench
The release of energy by the excited protons which occur at different rates in different tissue
Reduction in energy
Energy absorption by an object that is tuned to absorb energy of a specific frequency
example of resonance
fat and water are looked at in different frequencies
Similarites of CT and MRI
1. Both are used to diagnose
2. Both can use contrast media
Differences between CT and MRI
1. CT gives off radiation, MRI no radiation
2. MRI shows less bone density than CT
A technique for improving image quality in areas where motion is a problem. Coordinates signals to cardiac or respiratory cycles.
Mostly used in the brain to visualize ischemic changes
most commonly used in the brain, increasing use in breast and prostate imaging to differentiate between normal and abnormal tissue
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