MRSO Prep Test Questions and 100% Verified Solutions

Zero Boil-Off - System that reduces/eliminates the need to recharge Helium in a magnet. Quench - Quickly eliminating the magnetic field. Not immediate, takes 3 to 5 minutes to completely eliminate magnetic field. Loud Noise as Helium rushes out of Quench Vent. Can cause crack in the wire (very costly to repair/replace). Ohm's Law - Resistance that is equal to Voltage divided by the amperage in a wire. V=IR Use of Cryogen reduces/eliminates heating with high voltage and amperage which allows for high magnetic field. Cryogen - Liquid Helium 42* Kelvin Dual Cryogen System - Helium Nitrogen (used to keep Helium cold as back-up) Quench Vent - Used to vent boiled off Helium to the outside. Quench Vent in MRI Room is Zone IV (MRI manufacturer/engineer responsible for inspecting) Quench Vent outside is Zone III (Facility responsible for inspecting) Quench concerns with malfunctioning Quench Vent. - Dense fog in room. Can rain or snow which can contain Oxygen which is a fire risk. Hypothermia/Frostbite due to lowered room temperature. Aphyxiation Ruptured Ear Drums because of increased pressure in room. Difficulty opening door to Zone III due to increased pressure. May have to break window to release pressure. Magnet doesn't immediately lose its magnetic field. Peripheral Nerve stimulation due to change in magnetic field. Static Magnetic Field Concerns - Translation/Rotational Force *No adverse effects to patients or fetus have been noted to individuals exposed to up to 8T. Static Magnetic Field Occupational Exposure Limits - ICNIRP - Head and trunk is limited to a magnetic flux density of 2T - Limits are limited to a magnetic flux density of 8T IEC - Head and trunk is limited to a magnetic flux density of 4T. - Limbs are limited to a magnetic flux density of 4T. Static Magnetic Field General Public Exposure Limits - 400mT FDA Limits for Static Magnetic Field - 1 month old - 4T 1 month old - 8T Exposure to Static Magnetic Field of 4T - Requires approval. Time Varying Gradient Field Concerns - Electrical induction due to principle of Faraday's Law. Cardiac Fibrilation (not reported). Diaphragm Spasm - cause difficulty breathing. Brain Peripheral Nerve Stimulation - limited to the comfort of the patient. Time-Varying Gradient Field Normal Operating Mode Limits - IEC/FDA Normal Operating Mode - 80% of the maximum dB/dt exposure. = +1.0 * rb(1+0.36/teff) Time-Varying Gradient Field First Level Mode Limits - IEC/FDA 100% of the maxiumum dB/dt = 0.8 *rb(1+0.36/teff) Time-Varying Gradient Field Occupational Exposure Limits - ICNRP - restrictions are limited to 100kHz IEC - Limits to peripheral nerve stimulation. Time-Varying RF Field Concerns - The deposit of Heat (measured in SAR). Localized Heating to: Eyes, Fetus, & Testicles. RF Burning. Time-Varying RF Field Temperature Increase Limits - FDA - Whole body Exposure 1* Celsius. Time-Varying RF Field Heating Limits Normal Operating Mode - Increase in core temperature to 0.5* Celsius Increase in whole body SAR to less than 2W/kg Head SAR less than or equal to 3.2 W/kg Time-Varying RF Field Heating Limits First Level Mode - Increase in core temperature to 1* Celsius. Increase in whole body SAR to less than 4W/kg. Head SAR less than or equal to 3.2 W/kg. Time-Varying RF Field Heating Limits Second Level Mode - Increase in core temperature to greater than 1* Celsius. Increase in whole body SAR to greater than 4W/kg. Head SAR less than or equal to greater than 3.2 W/kg. Localized Transmit-Receive Coil Heating Limits for Normal Mode - FDA/IEC SAR equal to or less than 10W/kg in the head or trunk (orbits limited to 1* Celsius). SAR equal to or less than 20W/kg in extremities. Localized Transmit-Receive Coil Heating Limits for First Level Mode - FDA/IEC SAR equal to or less than 20W/kg in the head or trunk (orbits limited to 1* Celsius). SAR equal to or less than 40W/kg in extremities. Localized Transmit-Receive Coil Heating Limits for Second Level Mode - FDA/IEC SAR greater than 20W/kg in the head or trunk (orbits limited to 1* Celsius). SAR greater than 40W/kg in extremities. Time-Varying RF Field Occupational Exposure Limits - IEC - 4W/kg SAR