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MRSO exam Preparation study
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Zero Boil-Off - Answer>> System that reduces/eliminates the need to recharge Helium in a magnet. Quench - Answer>> 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 - Answer>> 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 - Answer>> Liquid Helium 42* Kelvin Dual Cryogen System - Answer>> Helium Nitrogen (used to keep Helium cold as back-up) Quench Vent - Answer>> 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. - Answer>> 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 - Answer>> 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 - Answer>> 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 - Answer>> 400mT
Time-Varying RF Field Concerns - Answer>> The deposit of Heat (measured in SAR). Localized Heating to: Eyes, Fetus, & Testicles. RF Burning. Time-Varying RF Field Temperature Increase Limits - Answer>> FDA
- Whole body Exposure <1* Celsius. Time-Varying RF Field Heating Limits Normal Operating Mode - Answer>> 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 - Answer>> 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 - Answer>> 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 - Answer>> 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 - Answer>> 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 - Answer>> 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 - Answer>> IEC
- 4W/kg SAR ICNIRP
- 0.4 W/kg SAR
- 61 V/m
- 0.16 A/m
- 0.2 mT
- 10 W/m^ Pregnancy Concerns to Static Magnetic Field - Answer>> No adverse effects noted to date. Pregnancy Concerns to Time-Varying RF Field - Answer>> Some affect thave been noted at heating greater than 39* Celsius Pregnancy Concerns to Time-Varying Gradient Field - Answer>> Noise production is a concern ICNIRP Pregnancy Concerns - Answer>> Limit RF heating to < .5* Celcius. No Gadolinium given. Pregnant MR Tech cannot be in zone IV during data acquisition.
Ferromagnetism - Answer>> An object with strong attractive force, in a strong static magnetic field, that retains a magnetic field even when leaving the strong static magnetic field. Flux Lines - Answer>> The gradient of magnetic densities that move from north pole of the static magnetic field to the south pole. Fringe Field - Answer>> The magnetic field that extends outside the MR unit. Gauss - Answer>> A magnetic field unit of measurement. 10,000 Gauss = 1 Tesla Horizontal Static Magnetic Field - Answer>> A magnetic field vector that is Horizontal. Seen in Superconducting Magnets Lenz's Force - Answer>> The process of non-ferrous objects producing a magnetic field when moved through a strong static magnetic field. Magnetic Field Strength - Answer>> The overall magnetic field strength of the MR unit. Magnetic Moment - Answer>> An individual magnetic field produced by each hydrogen proton. Magnohydrodynamic Effect - Answer>> When a patient is exposed to a strong static magnetic field, their blood becomes magnetized. This causes an elevated T wave in their cardiac cycle. Paramagnetic - Answer>> A weekly attractive force when placed in a static magnetic field. Passive Shielding - Answer>> The use of magnetically conductive material in an MR unit to reduce the fringe field.
Pauli Exclusion Principle - Answer>> The principle that describes the atom structure and the types of magnetism. Ferromagnetism, Superparamagnetic, Paramagnetic, Diamagnetism Rotational Force - Answer>> A force which aligns objects affected by the static magnetic field to its flux lines. Torque Spatial Gradient Magnetic - Answer>> The changing magnetic field strength demonstrated at different distances from the MR unit. Superparamagnetic - Answer>> A stronger attractive force than paramagnetic, but not as strong as ferromagnetism when placed in a strong static magnetic field. Teratogentic - Answer>> The potential effects of a static magnetic field on offspring of individuals exposed to it. Tesla - Answer>> The unit of measurement used to describe the static magnetic field. 1 Tesla - 10,000 Gauss Translation Force - Answer>> The attractive force of an object as it translates through the static gradient magnetic field. Missle Effect Vector - Answer>> The direction of the static magnetic field. Superconducting Magnet - Horizontal Permanent Magnet - Vertical Vertical Static Magnetic Field - Answer>> A magnetic field vector that is vertical. Seen with Permanent Magnets.
Nystagmus - Answer>> Involuntary rapid eye movements caused by exposure to a changing magnetic field due to Faraday's Law of Induction in the Optic Nerve. Peripheral Nerve Stimulation - Answer>> When nerves are stimulated when exposed to a changing magnetic field due to Faraday's Law of Induction. Physical Gradient - Answer>> The term used to describe the spatial encoding of the gradient coils. Z Gradient - Axial images X Gradient - Sagittal imaging Y Gradient - Coronal imaging Precession - Answer>> The wobbling motion that hydrogen nuclei demonstrates. Rise Time - Answer>> The period of time that it takes for the gradients to reach the sequences maximum amplitude. Slew Rate - Answer>> The speed at which the gradient coils can change the gradient magnetic field. 90 Degree RF - Answer>> The amount of energy used to tilt the hydrogen from longitudinal magnetism into the transverse axis. 180 Degree RF - Answer>> The amount of energy used to tilt the hydrogen from longitudinal magnetism 180 degrees. Used in a Spin Echo sequence to regain phase coherency. Bsub1 - Answer>> The unit used to describe the time-varying RF magnetic field. E-fields - Answer>> The electrical field is a result when a conductive material is exposed to a changing magnetic field.
Electromagnetic Spectrum - Answer>> The spectrum of frequencies that identify the amount and form of energy found at a specific frequency. Faraday's Law of Induction - Answer>> This describes how electrical current are produced in the presence of alternating magnetic field. Far Field - Answer>> The area in our gantry furthest from the RF transmitter. Near Field - Answer>> The area in our gantry closest to the RF transmitter. First Controlled Mode - Answer>> This is a mode where maximum regulated limit of SAR is allowed during acquisition. Limited to 4W/kg for whole body. Flip Angle - Answer>> A variable RF pulse that will tilt hydrogen away from the longitudinal axis less than 90 degrees. Hertz - Answer>> The amount of waveform in a second. Larmor Equation - Answer>> The equation used to identify the center frequency at a specific static magnetic field strength. Precessional frequency = gyromagnetic ration x B Longitudinal Recovery - Answer>> The period of time after an excitation pulse where magnetism returns to equilibrium magnetism. Loop Burns - Answer>> This is a type of burning where electrical current is induced in a patient and forced through a small contact area causing a burn. Non-Ionizing - Answer>> A form of energy that does not cause biological damage to tissues. Normal Mode - Answer>> This is a standard mode of operation where SAR for the whole body is limited to 2W/kg and 3.2 Wkg for the Head.
Thermoregulatory Mechanisms: Conduction - Answer>> Energy can be transferred from one source to another through contact, lowering the body temperature. Example: Heat Sink Thermoregulatory Mechanisms: Convection - Answer>> Heat radiating from a heat source to a cooler area. Use of a fan to pass cool air over patient can help lower body temperature. Thermoregulatory Mechanisms: Radiation - Answer>> Heat will flow away from the patient's body. Transmit-Receive Coil - Answer>> A coil that both produces and receives RF energy to/from the patient. Transverse Decay - Answer>> The period of time after an excitation pulse where magnetism is lost in the transverse axis. Wavelength - Answer>> The distance from one amplitude in a frequency to the next. Anthropogenic - Answer>> The process of gadolinium contrast entering th drinking water system from patients who have received gadolinium contrast. Blood-Pool Contrast - Answer>> Contrast that binds to proteins (albumin) in the blood so it can stay intravascular longer. Used to image the vasculature system. Chelate - Answer>> A process of binding a metal ion (gadolinium ion) to a molecule so it can be easily released from the body. Extracellular Contrast - Answer>> Contrast that disperses extracellular. Used to image Central Nervous System (Neuro).
Gadolinium Associated Plaque - Answer>> Plaques (Hardening) that form on a patient's skin that contain gadolinium in them. Gadolinium Retention - Answer>> The deposition of gadolinium in the body in patients with normal kidney function. GFR - Answer>> Glomerular filtration rate. Hepatobilliary Contrast - Answer>> Contrast that is primarily excreted by the liver. Used in Liver imaging. Ionic Contrast - Answer>> A type of contrast that contains a charge when dissolved in a solution (blood) that forms a stronger bind between the gadolinium ion and the ligand. Linear - Answer>> A type of ligand with a linear design structure which attaches a gadolinium ion on it. Long Term Adverse Reaction - Answer>> An adverse effect from a contrast media that occurs days, months, or years after the contrast was administered. Macrocyclic - Answer>> A type of ligand structure which "cages" in the gadolinium ion. Nephrogenic System Fibrosis - Answer>> A condition where fibrosis develops on skin and internal organs when patients with compromised renal function are exposed to gadolinium contrast. Non-Ionic Contrast - Answer>> A type of contrast that does not contain a charge between the gadolinium and the ligand. Relaxivity - Answer>> The amount of T1 shortening produced from a contrast agent. Viscosity - Answer>> The thickness of a contrast agent.
Explains RF heating on implants. ASTM 2213 - Answer>> Test method for measurement of magnetically induced torque on medical devices in the MR environment. This describes the static magnetic field on objects that demonstrate ferrous components. Captain of the Ship Doctrine - Answer>> An act that holds one person (Radiologist) accountable for actions that occur during an MR procedure. Criminal Case - Answer>> A case involving someone who is accused of committing an illegal activity. What organization is responsible for the safety of the general public in the US? - Answer>> FDA IEC 60601-2-23 - Answer>> Defines the conditions of Normal Mode, First Controlled Mode, and Second Controlled Mode. IEC - Answer>> International Electrotechnical Commission A non-profit organization that forms standards for items that involve electro- technology. Malpractice - Answer>> An act that involves not meeting a standard of care and causes harm because of it. MR Conditional - Answer>> A label defined by the ASTM that indicates that an object is safe to enter the MR environment under specific guidelines. MR Safe - Answer>> A label defined by the ASTM that indicates an object is safe to enter the MR environment. Must be non-metal, non-conductive, and non-magnetic. MRI Unsafe - Answer>> A label defined by the ASTM that indicates that an object may pose a threat to a patient in the MR Environment.
NEMA - Answer>> National Electrical Manufacturers Association An organization that develops technical standards. Neglect - Answer>> An act that involves not meeting a standard of care for a patient. Misdemeaner - Answer>> Minor offense punishable by fine or punishment of less than one year NEMA MS1-9 - Answer>> Defines recommendations for operations in an MR environment. Non-MR Personnel - Answer>> Essentially to MRI training, which includes patients visitors, or facility staff who do not meet the criteria of level 1 or level 2 MR personnel. Tester Magnet - Answer>> A magnet that is greater than 1000 gauss that can be used to test how ferrous a potential MR threat is. Tort Case - Answer>> A case that involves damage to a person or property that typically involves paying for damages. What effect does Gadolinium have on tissue. - Answer>> Shortens T and T2 Relaxation. T1 appear brighter. T2 appear darker. Osmolarity - Answer>> The amount of dissolved solutes per liter of solution. Non-Allergic Reaction to Gadolinium - Answer>> Also known as Chemotoxic Reactions. Don't involve the autoimmune system. Examples: Nausea, Emesis, Headache
Body e-Static field limits 1.76 Volts/m (1=0.36/stimulation duration [ms]) Localized Heating by Transmit-Receive Coil SAR Limit at Normal Mode - Answer>> Head - 38C or 3.2W/kg Torso - 39C or 10W/kg Extremities - 40* or 10W/kg IEC 60601-2-33 First Level Limits - Answer>> Noise limits to 99 decibel for MRI patients. Static Magnetic Field up to 4T Heating of up to 1*C (4W/kg) Body Gradient default 20T/sec (1+0.36/stimulation during [ms]) which is equal to or less than 56T/s Body e-field limits 2.2 Volts/m (1=0.36/stimulation duration [ms]) IEC 60601-2-33 Second Level Limits - Answer>> Noise limits to 99 decibel for MRI patients. Requires IRB approval for Static Magnetic Field >4T and requires an investigation device exemption (IDE). NEMA MS 1-9 - Answer>> Methods of measuring SAR. Magnetohydrodynamic Effect - Answer>> Artifact seen on ECG Monitoring. Elevated T wave Wavelength on a 1.5T - Answer>> 500mm Wavelength on a 3T - Answer>> 250mm Length of wire on a 1.5T that has potential for maximum temperature increase - Answer>> 25cm
Wavelength/2 = maximum temperature increase 1.5T Wavelength 500mm = 50cm 50cm/2= 25cm Length of wire on a 3T that has potential for maximum temperature increase - Answer>> 12cm Wavelength/2 = maximum temperature increase 3T Wavelength 250mm = 25cm 25cm/2= 12cm Objects greater than this length will start to start to produce heat. - Answer>> 2cm Passive Implants - Answer>> Implants that contain no electrical components. Example Dental work, Beast Implants, Tissue Expanders, Ocular Implants, Wires/Leads/Sutures, IUD's, Staples, Status, and Filters, Foil Back Medication Patches, Screws, and Foreign Bodies. Passive Implants: Dental Implants - Answer>> If they do not contain magnetic components, no risks or concerns. May cause artifact. Passive Implants: Breast Implants - Answer>> Pose no threat to Static Magnetic Field or Time Varying Magnetic Field. Passive Implants: Tissue Expanders - Answer>> Contain some metallic components. Evaluate for Ferrous components. Risk of Static Magnetic Field - Can cause implant to to migrate.
