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47 Cards in this Set
- Front
- Back
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FDA dB average limit |
105 |
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FDA average limit with hearing protection |
99 |
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FDA peak noise limit |
140 |
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Loops of thin wire on a cylindrical shell within bore |
Gradient coils |
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Purpose is to spatially encode information |
Gradient coils |
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Gradient magnetic field known as... |
Time varying magnetic field |
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Effect of rapidly turning on/off gradient magnetic field |
Voltage/eddy currents |
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Law for voltage currents caused by gradient magnetic fields |
Farraday's law |
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3 biological effects we are concerned with while changing magnetic field |
Nerves, blood vessels, and muscles |
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Visual sensation of flashing lights |
Magneto-posphenes |
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Most sensitive index of induced currents |
Retinal stimulation |
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Frequency of sound measured in... |
Hertz |
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dB for pain threshold |
140 |
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Typical noise range for 1.5T |
80-110 dB |
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Quiet gradient system can reduce noise by... |
40dB |
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Earplugs can reduce noise by... |
10-30 dB |
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2 features of magnetic field that are source of most incidents |
Projectile effect and translational attraction |
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Occurs when one point of an object is attracted to a greater extent than kbject's furthest point |
Translational attraction |
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Number of access zones |
4 |
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Zone that provides opportunity for prescreening |
2 |
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Zone that is entry to MRI room and is last barrier against incident |
3 |
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Line that is clearly marked |
5 gauss line |
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Training to go into zones 3 and 4 |
Level 2 training |
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Most common adverse event |
Thermal event |
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Ability of kbject to become magnetized |
Magnetic susceptibility |
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1 tesla is how many gauss |
10,000 |
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2 types of effects in MRI environment |
Translational force and rotational force |
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Also known as missle effect |
Translational force |
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Stray magnetic field which extends beyond the bore of the magnet |
Fringe field |
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Safety zones defined by... |
American college of radiology |
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Card from patient about device should include what 3 things |
Model #, manufacturer, contact # |
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How long after surgery for intravascular coils, filters, stents |
8 weeks |
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How long after surgery for extra cranial clips |
4-6 weeks |
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May contain aluminum foil |
Transdermal patches |
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Magnetic force of attraction follows what law |
Inverse square law |
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Ability of object to become magnetized |
Magnetic susceptibility |
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1T = xGauss |
10,000 |
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Stray magnetic field that extends beyond bore if magnet in all directions |
Fringe field |
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Accelerate faster: large and heavy ir small and light |
Small and light |
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What SI unit represents strength of magnetic field? |
Tesla |
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1.5T how much stronger than earth magnetic field |
30,000x |
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3 types of magnets used in clinical imaging |
Superconducting, permanent, resistive |
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Magnet with water cooling system |
Resistive |
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Magnet most commonly used in clinical setting and cooled by liquid helium |
Superconductive |
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Define MRI safe |
? |
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Used to disconnect from line voltage, but does not turn off magnet |
Emergency shutdown switch |
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Type of gas released during quench |
Helium |
