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MRI Safety

The MR Safety web based training will provide the Technologists with information regarding screening for all personnel entering the MR environment, definitions for MR safe, and conditional and unsafe devices and objects. Spatial gradients, Magnetic Filed B0, Static Magnetic field, and Eddy Currents will be discussed. MR Contraindications, MR Compatibility,and other MRI safety considerations will also be reviewed.

Welcome The MR Safety web based training will provide the Technologists with information regarding screening for all personnel entering the MR environment, and definitions for MR safe, and conditional and unsafe devices and objects. Spatial gradients, Magnetic Filed B0, Static Magnetic field, and Eddy Currents will be discussed. MR Contraindications, MR Compatibility, and other MRI safety considerations will also be reviewed.   You should now be able to: Perform screening for Patients, personnel, and non-personnel Identify MRI safe, conditional, and unsafe devices and objects Identify the various electromagnetic fields Identify Magnetic Field Lines Identify Spatial Gradients and Magnetic Field B0 Identify Static Magnetic field (e.g., projectiles) Describe and identify Eddy Currents induced by gradient pulsing Describe Safety Instructions on RF and gradient fields  Describe MR Contraindications   Illustrate MR Compatibility Describe and illustrate other MRI safety considerations (e.g., cryogen safety, fire, medical emergencies)                                                                                                                                                                           Thank you! Proceed to the quiz sections below to complete the course. Screening for Patients, personnel and non-personnel Preliminary Screening Helps prevent scheduling patients that may be inappropriate candidates for MR examinations Comprehensive Screening Printed form to document screening procedure Review information on screening form Verbal interview to verify information on form and discuss patient concerns MR-safety trained healthcare professionals must conduct patient screening Anyone in the MR examination room exposed to the MR field (e.g. patients, physicians, operating and cleaning personnel, accompanying persons, and rescue personnel/fire fighters) All limits and safety measures regarding electromagnetic fields equally apply Course Objectives Upon successful completion of this course, the participants will be able to: Perform screening for patients, personnel, and non-personnel Identify MR safe, conditional, and unsafe devices and objects Identify the various electromagnetic fields Identify Magnetic Field Lines Identify Spatial Gradients and Magnetic Field B0 Identify Static Magnetic field (e.g., projectiles) Describe and identify Eddy Currents induced by gradient pulsing Describe Safety Instructions on RF and gradient fields  Describe MR Contraindications   Illustrate MR Compatibility Describe and illustrate other MRI safety considerations (e.g., cryogen safety, fire, medical emergencies)                                                                                                                                                                                                                                              Electromagnetic fields Static Magnetic Field Generated by a superconductive magnet and may extend beyond examination room (walls, ceilings) 2 type of forces exerted on a ferrous object brought close to the magnet Rotational force (torque) Ferrous object turns and align with magnetic field direction Translational force Pulls ferrous objects toward magnet’s isocenter Forces are felt when a ferrous object is in a magnetic field that changes in strength over distance Static Magnetic field (e.g., projectiles) Static Magnetic Field Magnetic objects introduced into the magnetic field may become projectiles Injury to patient and operating personnel Forces on ferromagnetic objects are directly proportional to the spatial gradient, and not the actual magnetic field Magnetic Field Lines – View Direction of Magnet Axis   Magnetic field strength of 3T Starts at magnet isocenter 0.5 mT line marks exclusion zone of basic main magnetic field Contours of equal field strength Graphic referenced to plane z=0 Electromagnetic Fields Continued Gradient Fields Spatially linear rising additional fields of variable strength Gradient fields are superimposed on static main magnetic field in three different orientations May cause electrical currents in patient's tissue and lead to peripheral nerve stimulation Slew Rate Rate of change of gradient amplitude is usually quoted Evaluating gradient performance and potential physiological effects Maximum (amplitude or slew rate) is defined for a single given physical direction of X, Y, or Z ”Effective maximum” (amplitude or slew rate) is defined for when all 3 physical directions are applied simultaneously at their maximums Magnetic Field Lines – Side View of Magnet MR Contraindications Qualified physician must evaluate risk versus benefit of MR examination for every patient Spatial Gradients of Magnetic field B0   Magnetic Field B0 – Side View Origin of diagram is referenced to magnet isocenter Contour lines run through center of magnet Highest location value is shown on each diagram identified as an Eddy Currents induced by Gradient Pulsing Patient burns Check MR Safety guidelines for implants and prostheses prior to scanning the patient or entering the magnet room Electrically conducting objects Injury to patient due to warming and incorrect diagnosis due to artifacts Patient should remove all electrically conducting objects, e.g. Jewelry and piercings, etc Patient removes all clothing that has electrically conducting material, for example bras, metallic appliqués or woven metallic yarns Eyeliners and tattoos may contain ingredients causing artifacts or skin irritations during MR exams Remove makeup prior to examination Patients should seek medical attention in case of discomfort during or following the MR exam Safety Instructions on RF and Gradient Fields   Patient Monitoring Routine monitoring – All patients should receive Mandatory monitoring – Sedated, and physically unstable patients First Level Controlled Operating Mode medical supervision is mandatory Inform patient about monitoring and communication equipment Squeeze ball, intercom Patients unable to communicate should be monitored closely, these include but may not be limited to Small children, seriously ill, paralyzed, unconscious, sedated, or handicapped patients Incompatible monitoring devices may cause Patient burns Use only MR-conditional monitoring devices e.g., ECG electrodes including disposable electrodes and pulse sensor that meet the conditions for safe use MR Compatibility MR Compatibility – Combinations with other systems, accessories The following hazards or complications may occur through the use of third-party products during MR examinations Heating of system cables or connection cables Interference with MR image quality Malfunctioning of third-party products Auxiliary equipment, not been specifically tested and approved for use in environment of MR equipment May result in burns or other injuries to patient   Ambient conditions Ambient conditions and SAR have a considerable effect on patient’s body temperature Regularly check ambient conditions Regulating Room Temperature Patient’s ability to dissipate heat is increasingly affected as room temperature and relative humidity increase Room temperature ≤ 22°C (or) 72°F Relative humidity ≤ 60% Other Safety Considerations Emergencies Familiarize location and functionality of installed emergency switches Report all accidents resulting in personal injury immediately to appropriate authorities Observe established emergency plans Emergency plan in case of coolant accidents Emergency plan for fire fighting Static Magnetic field (e.g., projectiles) Patient effects Patients, Personnel and non-personnel are exposed to the static magnetic field Keep sufficient distance to the magnet and avoid rapid head movements Possible side effects more prevalent at 3T Dizziness, light-headednes Changes in ECG Increased T-wave – due to aortic flow Induced currents in saliva Metallic taste Magnetophophenes Receptors on retina irritated by eddy currents Changes in ECG - Increased T-wave   Importance of Product Gradients Fields and Spatial Gradients Force applied to a device near the magnet will either be proportional to the spatial gradient, or the product gradient field Depends if the device is magnetically saturated or not Most instances Danger exists outside the magnet, not inside magnet Spatial Gradients versus Product Gradients   Spatial Gradients versus Product Gradients Continued What is the Magnetic Saturation?   Safety Instructions on RF and Gradient Fields Localized Regions of High RF and bore wall contact Localized regions of high RF in close proximity to the body coil are generated when Patient's skin contacts tunnel lining or RF coil cables Parts of patient's body touch e.g., knees May lead to burns or increase probability of peripheral nerve stimulation Safety Instructions on RF and Gradient Fields Localized Regions of High RF and bore wall contact Prevent potential localized regions of high RF as shown in red labeled illustration Ensure the patient is positioned with proper distance to magnet tunnel and between parts of the body as shown in the green labeled illustration Lower effects of gradient fields or RF fields Keep sufficient distance to magnet tunnel and RF coils Reduce time of exposure during measurements Safety Instructions on RF and Gradient Fields Patient’s wearing electrically conductive material and incorrect patient positioning Formation of electric current loops and peripheral nerve stimulation of the patient Patient is not wearing wet clothing Patient is free of jewelry and piercings Patient is free of electrically conductive materials worked into items of clothing (e.g., bras, metallic appliqués or woven metallic yarns) Always position patient so patient's arms are aligned with torso and ensure hands, arms, and legs do not touch (minimum distance: 5mm)   Minimum distance of 5 mm is maintained between patient and tunnel covering Ensure distance by, using positioning aids, e.g. blankets made of linen, cotton, or paper, or dry material that is permeable to air Sufficient ventilation needed Instruct patients of possible stimulation during the MR examination Twitching muscles, tingling sensation Safety Instructions on RF and Gradient Fields Acoustic Noise – Hearing Protection Appropriate hearing protection that lowers noise to at least 99 dB Headphones are not classified as hearing protection Headphones should only be used in combination with ear plugs for communication purposes Provide anesthetized or unconscious patients with hearing protection Ear protection should not be omitted even at moderate sound levels Anyone in examination room should wear hearing protection during examination that lowers noise to at least 85 dB Training the operator is required for proper positioning of hearing protection for neonates and infants Applies to any condition where an alternative form of hearing protection is needed Safety Instructions on RF and Gradient Fields Maintenance and Repair High voltage and currents inside electronics cabinets Risk of death by electrocution Electronics cabinets should only be opened by Siemens authorized personnel Exposure to all electrical current sources Risk of electrocution / electrical burns Cleaning of system Only clean system covers and surfaces with a damp cloth Safety Instructions on RF and Gradient Fields Miscellaneous Fluids Solutions must be handled carefully with respect to Material Safety Data Sheet (MSDS) for chemical agents Dielectric Cushions Phantoms           Safety Instructions on RF and Gradient Fields Laser Light Aperture Do not stare directly into laser beam RF Blankets Heating up or ignition of synthetic blankets is possible via RF field during measurement! Patient burns Use only covers made of paper, cotton or linen Heating up of RF blankets or shields used to avoid aliasing artifacts Patient burns Never use RF blankets or other conductive sheets within the MR system Other Safety Considerations Emergency Switches MR systems have different types of emergency switches            Other Safety Considerations Magnet Stop Switch Magnet Stop switch triggers a controlled magnet quench Shuts down magnetic field MR system is not disconnected from power Two different versions of Magnet Stop switch on MR system Individual switch Integral part of alarm box Switches may also be installed in other areas of MR system Other Safety Considerations Emergency Shut-down switch Emergency Shut-down switch is used to switch off electric power of entire MR system Typically there are two Emergency Shut-down switches installed: Near alarm box Examination room Warning Fire or electrical accidents and personal injury Press Emergency Shut-down switch immediately Contact the fire department Other Safety Considerations Table Stop button Used to stop motorized table movement Located on intercom Patient table Other Safety Considerations Coolant accidents First aid in case of shortness of breath Person becomes unconscious due to severe shortness of breath: Remove unconscious persons immediately from examination room Start CPR and contact a physician immediately First aid in case of frostbite Direct contact with subzero liquids, gases, and surfaces (e.g. pipes) may lead to frostbite Eyes and mucous membranes are especially vulnerable Other Safety Considerations Fire Following devices/materials may be used for fire fighting Non-magnetic CO2 extinguisher Self-contained, anti-magnetic compressed-air breathing apparatus (or hose connection) Airtight chemical protective suit Other MR Safety Recommendations MR Safety officer MR policies and procedures Assess staff compliance Provide MR Safety courses for staff with access to MR scan room Transport, security, housekeeping, maintenance, emergency responders, etc. Allow only non-ferrous MR equipment in MR environment Wheelchairs, stretchers, oxygen bottles, IV poles, etc. Other Safety Considerations Magnetic Stop Switch Continued After Magnet Stop switch has been pressed Alarm is triggered WARNING LED will light up and an alarm signal sounds NOTE: As a rule, Siemens Customer Service Engineer and the Customer Care Center must be called following a quench. The magnet must only be put back into operation by Siemens authorized service personnel.                Other Safety Considerations Magnetic Stop Switch Continued Warnings: Formation of droplets due to condensation during quenching Personal injury and risk of fire Do not touch exhaust line Do not stand under exhaust line Avoid open flames and do not smoke System indicates Magnet Stop error Hazardous conditions because magnet cannot be quenched in case of emergency Immediately remove patient from magnet Restrict access to examination room Notify Siemens Customer Service Engineer and the Customer Care Center MR Contraindications Continued MR examinations are contraindicated for patients with electronic or electronically conductive implants or metals Especially those containing ferromagnetic foreign matter Exceptions: Certain implantable medical devices are cleared, approved and/or licenses by Competent Governmental Authorities and/or labeled by manufacturer as MR-conditional Contact implant manufacturer for specific conditional information. The conditions for MRI safety are the responsibility of the implant manufacturer, not Siemens Spatial Gradients versus Product Gradients Continued .     Spatial Gradients of Magnetic field B0 Continued Magnetic Field B0 – Top View  Origin of diagram referenced to magnet isocenter. Contour lines run through center of magnet                                        Spatial Gradients of Magnetic field B0 Continued Spatial Gradient of Magnetic Field – Side View Change of magnetic field as a function of distance to magnet expressed by spatial gradient of B0 Highest location value is shown on each diagram identified as an Highest location on each spatial gradient,  force to magnetically saturated ferromagnetic object is largest Spatial Gradients of Magnetic field B0 Continued Spatial Gradient of Magnetic Field – Top View    Change of magnetic field as a function of distance to magnet expressed by spatial gradient of B0 Highest location value is shown on each diagram identified as an Highest location on each spatial gradient,  the force to magnetically saturated ferromagnetic object is largest Please refer to the Siemens MR System Owner Manual for additional information regarding Magnetic field B zero and spatial gradients. MR Compatibility Continued MR Compatibility – Combinations with other systems, accessories The following hazards or complications may occur through the use of third-party products during MR examinations MR system is combined with other systems or components Must be ensured that the planned combination and cable routing do not affect the safety of patients, personnel, or environment Ensure devices used in the examination room are compatible with MR field strength Devices compatible with 1.5T systems may be unsuitable for 3T systems Contact Siemens Customer Service Engineer or the Customer Care Center prior to combining the MR system with other third-party products or devices   Electromagnetic Fields Continued RF Fields The nuclear spins of the body tissue are stimulated via pulsed electromagnetic Radio Frequency (RF) fields RF pulses are generated by an RF transmit amplifier and transferred via RF coils to the object to be measured RF fields lead to warming of the body tissue. Important value per body weight is the Specific Absorption Rate (SAR) Side Effects Dizziness, heating, claustrophobia, and nerve stimulation MRI Safe, Conditional, and Unsafe Devices and Objects Labeling The American Society for Testing and Materials (ASTM) International developed a new classification system for implants and ancillary clinical devices. The following definitions apply: MR Safe MR Conditional MR Un-Safe MR Safe   Device or implant is completely non-magnetic, non-electrically conductive, non-RF reactive, and indicates no known hazards in all MRI environments *Disclaimer: MR imaging of patients with metallic implants brings specific risks. However, certain implants are approved by the governing regulatory bodies to be MR conditionally safe. For such implants, the previously mentioned warning may not be applicable. Please contact the implant manufacturer for the specific conditional information. The conditions for MR safety are the responsibility of the implant manufacturer, not of Siemens. MR Conditional   Device or implant may contain magnetic, electrically conductive or RF-reactive components Devices are safe when used in proximity to MRI provided conditions for safe operation are defined and observed MR-conditional devices (e.g., RF communications equipment) may present hazards Observe manufacturer's operator manual to avoid potential hazards and injuries *Disclaimer: MR imaging of patients with metallic implants brings specific risks. However, certain implants are approved by the governing regulatory bodies to be MR conditionally safe. For such implants, the previously mentioned warning may not be applicable. Please contact the implant manufacturer for the specific conditional information. The conditions for MR safety are the responsibility of the implant manufacturer, not of Siemens. MR Unsafe MR Un-Safe An item that is known to pose hazards in all MR environments

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