MRSO exam Preparation study guide, Exams of Magnetic Resonance Imaging (MRI)

Download MRSO exam Preparation study guide and more Exams Magnetic Resonance Imaging (MRI) in PDF only on Docsity! MRSO exam Preparation study guide 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 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^2 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. These agencies regulates Static Magnetic Field Occupational Exposure - Answer>> ICNIRP & IEC This agency regulates Static Magnetic Field Patient Exposure - Answer>> FDA These agencies regulates Time-Varying Gradient Field Occupational Exposure - Answer>> ICNIRP & IEC These agencies regulates Time-Varying Gradient Field Patient Exposure - Answer>> IEC/FDA This agency regulates MRI sound pressure levels - Answer>> FDA MRI Sound Pressure Levels limited to - Answer>> 99dBA with Hearing protection These agencies regulates Time-Varying RF Field Patient Exposure - Answer>> FDA & IEC These agencies regulates Time-Varying RF Field Occupational Exposure - Answer>> IEC & ICNIRP Active Shielding - Answer>> The use of a coil of wire, with an electrical current running through it to produce an electromagnetic field opposing the static magnetic field, to reduce the fringe field. Bsub0 - Answer>> The unit used to describe the static magnetic field. Deflection - Answer>> The amount of attraction an object has to the static magnetic field. Diamagnetism - Answer>> A weekly repulsive force when placed in a strong static magnetic field. Faraday's Law of Induction - Answer>> This describes how electrical currents are produced in the presence of alternating magnetic fields. 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. 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 B0 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. Parallel Imaging - Answer>> This is a technique where 2 or more coils can be used in tandem to collect multiple lines of K space at a time. Radio Waves - Answer>> the range of frequencies that are used in MRI to produce resonance. Receive Only Coil - Answer>> A Coil that only detects signal emitted from the patient. Reflective Burns - Answer>> This is a burning where RF is reflected back to the patient producing burning. example: foil-backed medicine patches. Resonance - Answer>> The transverse of energy from one thing to another by means of two or more things oscillating at the same frequency. Resonant Burns - Answer>> This is a type of burn where resonance is produced in an implant or in equipment on a patient, which will produce induction. The e-fields produced will cause burning. Proximity Burns - Answer>> This is a type of burning where tissues in the near field get burned. Second Controlled Mode - Answer>> This is a mode reserved for research or testing where the SAR can operate above the maximum regulated limit. SAR - Answer>> Specific Absorption Rate Estimated measure of patient heating. Measured in watts/kg Types of Thermoregulatory Mechanisms - Answer>> Evaporation, Conduction, Convection, Radiation Thermoregulatory Mechanisms: Evaporation - Answer>> Sweating. The body releases sweat through pores lowering the body temperature. Short Term Adverse Effects - Answer>> An adverse effect to a contrast agent that occurs minutes, hour or days after it was administered. Transmetallation - Answer>> The process of a ligand losing a gadolinium ion and picking up another metal ion (zinc) 5 Gausse Line - Answer>> A distance from the MR unit where 5 gauss of magnetism is demonstrated. This is the area where malfunctions to electrical devices can occur. ACR Guidance Policy 2013 - Answer>> A document that defines the safest MR practices that should be used clinically. American College of Radiology - Answer>> An organization that defines safe practices and quality in radiology. ASTM - Answer>> American Society for Testing and Materials. An international standard that publishes technical standards for many items and equipment. Responsible for the labels: MR Safe, MR Conditional, MR Unsafe. ASTM F2503 - Answer>> Standards for implants and objects in the MR environment. Defines MR Safe, MR Conditional, MR Unsafe guidelines. ASTM F2052 - Answer>> Test Method for measurement of magnetically induced displacement force on medical devices in the MR Environment. Explains how objects are tested in the Static Magnetic Field. ASTM F2119 - Answer>> Test method for evaluation of MR image artifacts for passive implants. Defines how images are evaluated for artifacts. ASTM F2182 - Answer>> Test method for measurement of radio frequency induced heating on or near passive implants during MR imaging. 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 T1 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 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. Risk of Time Varying Magnetic Field - Will not pose a large threat. Can produce large artifact. Passive Implants: Ocular Implants - Answer>> Retinal Tack or Eyelid Springs may contain some ferrous components. Risk of Static Magnetic Field - Can interact and cause patient harm. Risk of Time Varying Magnetic Field - Will not pose a large threat. Can produce artifact. Glaucoma Drainage Implants majority nonmetal. The 316 K stainless steel is nonferrous, but can cause artifact. Scleral Buckle (repair retinal detachment with a Tantalum clip) are nonferrous. Passive Implants: Wires/Leads/Sutures - Answer>> >2cm can induce heating. Length, Orientation, Size, Location, Position, and Material need to be considered. Risk of Static Magnetic Field - Can cause implant to to migrate. Risk of Time Varying Magnetic/Gradient Field - Can induce electrical current and stimulate tissue at the end of the leads. If stimulation interferes with cardiac process, neurological processes, or respiratory processes, may cause harm to patient. Time Varying Radiofrequency Fields - Causes the greatest risk. Can induce significant heat at the end of the leads or wires. Sutures - Minimal effects, not shown to harm patient. Staples - No threat from Static Magnetic Field. Passive Implants: Stents - Answer>> Risk of Static Magnetic Field - Can demonstrate some deflection. Time Varying Radiofrequency Fields - If metallic may produce heating dependent on size. Follow manufacturer recommendations. Passive Implants: Filters - Answer>> IVC Filters Risk of Static Magnetic Field - Manufactures suggest waiting 6-8 weeks to allow scarring to hold implant in place. Risk of Time Varying Magnetic/Gradient Field - Follow manufacturers recommendations. Risk of Time Varying Radiofrequency Fields - Follow manufacturers recommendations. Passive Implants: Foil Backed Medication Patches - Answer>> Risk of Static Magnetic Field - No Risk Risk of Time Varying Magnetic/Gradient Field - No Risk of Time Varying Radiofrequency Fields - May cause heating. Remove before scan. Passive Implants: Copper7/Copper T - Answer>> No Risk Passive Implants: Foreign Bodies - Answer>> Risk of Static Magnetic Field - Assume that they are ferrous and may cause deflection. More concerned if near vital areas (eyes, vessels, nerves, etc.) Risk of Time Varying Radiofrequency Fields - Usually smaller than <2cm so minimal heating may occur. Active Implants - Answer>> Objects that contain electrical components and use a generator. Follow manufacturer's recommendations. Ways to Lower Gradient Stimulation - Answer>> Use Spine Echo Pulse Sequences - uses 180* RF pulse rather than gradients to refocus Hydrogen Nuclei reducing PNS. Use Thicker Slices - Has a more shallow gradient reducing PNS. Use Smaller Image Matrix - Decreases the number of lines of K-space that fill. Increases resolution. Uses a more shallow Phase Gradient reducing PNS. Use Larger FOV - Uses a more shallow Frequency Gradient reducing PNS. Ways to Lower Patient Heating - Answer>> Use Conventional Gradient Echo, Steady-State Gradient Echo, and Echo Planar Imaging Pulse Sequences - Spin Echos used 180* RF pulse to refocus Hydrogen delivering 4x than a 90* RF pulse. Avoid Chemical Shift Pre-Saturation (Fat Sat) - they increase heating because of the use of one or many 90* RF pulses to the same area. Avoid Spatial Pre-Saturation (Sat Band) - they increase heating because of the use of one or many 90* RF pulses to the same area. Avoid Magnetic Transfer Compensation - Increases heating due to many RF pulses being delivered to a patient at a specific frequency. Avoid Inverse Recovery Sequences - Uses 180* pulse sequences. However has benefits identifying pathology over other imaging weighting including Fat Sat. Decrease Flip Angle - Flip angle is directly related to patient heating. Example 180* has 4 times as much as 90*. Increase Repetition Time (TR) - Longer the TR, the more time we give patient to thermoregulate. Longer TR promotes PD and T2 weighted imaging, so can't be used for T1. Increase Echo Spacing - This increases the space between RF pulses (with spine echo increases the distance between 180* RF pulses) giving the patient time to thromoregulate. Change Pulse Mode - Pulse mode changes the way RF pulse is delivered. Whisper mode, normal mode, or low SAR mode are different types. Reduce Slices - Reducing slices reduces the amount of RF pulses needed. Reduce Image Matrix - Reducing the Phase resolution reduces the number of lines of K-space needed to fill which means less refocusing pulses/TR cycles. Increase Number of Acquisitions - Reduces the number of echos collected per TR allowing our patient time to thermoregulate. Use Parallel Imaging - Uses multiple coil elements to fill K-space. Decrease Number of Averages - Uses less RF pulses to fill K-space. Center Frequency for a 1.5T - Answer>> 64MHz Center Frequency for a 3T - Answer>> 128MHz 1G/cm = T/m - Answer>> .01T/m 1T/m = G/cm - Answer>> 100G/cm Deflection <45* - Answer>> Less than gravity. Deflection >45* - Answer>> Greater than gravity. IEC 60601-2-33 - Answer>> Defines SAR limits. Normal Operating Mode - 2W/kg First Level - 4W/kg Second Level - Exceeds limits set by FDA/IEC. Needs approval. ICNIRP - Answer>> International Commission on Non-Ionizing Radiation Protection Researches the health effects of the exposure to the high static magnetic field. - Determines limits of static field at different controlled modes. - Defines occupational exposure limits. - Defines general public exposures limits. - Explains protective measures. FDA - Answer>> Food and Drug Administration Regulates safety practice in MRI. - Enforces ASTM Practices. - Enforces IEC Practices. ACR - Answer>> American College of Radiology Created blue ribbon panel to address MR Safety. Produced the ACR Guidance Document for Safe MR Practices. ASTM - Answer>> American Society for Testing and Materials. FDA MR Environment Temperature Limit - Answer>> No greater than 25*C. FDA Static Magnetic Field Limits - Answer>> <1 Month Old - 4T >1 Month Old - 8T FDA Auditory Limits - Answer>> Maximum Peak - 140dB With Ear Protection - 99dB