TiP-TV Training in Partnership Program Supplement and Test for Imaging Professionals. MR: Quench Your Thirst for MR Safety

Transcription

1 TiP-TV Training in Partnership for Imaging Professionals MR: Quench Your Thirst for MR Safety Publication Date: January 26, 2006 Revised/Reissued: March 1, ASRT-approved Category A CE Credit imagination at work

2 TABLE OF CONTENTS PROGRAM SUMMARY... 3 CONTINUING EDUCATION CREDIT... 4 INTRODUCTION... 5 ELECTROMAGNETIC RADIATION... 6 Static Magnetic Field... 7 Static Magnetic Fields: Vertigo & Nausea... 8 Gradient Magnetic Field... 9 Radiofrequency (RF) MR SCREENING IMPLANTS AND DEVICES PATIENT CARE IN MR Monitoring Contrast Anxiety and Claustrophobia MR Procedure for Pregnancy ACR MR Safe Practice Guidelines APPENDIX A: PRESENTERS APPENDIX B: RESOURCES APPENDIX C: GLOSSARY of 27 GE Medical Systems, A General Electric Company, Going to Market as.

3 PROGRAM SUMMARY This page provides an overview of the program content and learning objectives. Please refer to the Table of Contents for a detailed list of the topics covered. We encourage you to file a copy of this Program Summary and the Table of Contents with your continuing education certificate. We also recommend that you provide a copy of this information to your manager as a record of your educational achievement. PROGRAM DESCRIPTION Magnetic resonance (MR) procedures continue to expand with regard to usage and complexity. Patient management and safety issues are important aspects of this diagnostic imaging modality. MR technology continues to evolve and it is necessary to update, revise, and review MR safety procedures and policies. In this program, we review the present safety guidelines and recommendations, review the latest information for implants and devices used in MR and the safety considerations for clinical use of 3 Tesla (T) systems and higher. PROGRAM OBJECTIVES By the end of this program, the viewer should be able to: 1. Explain the types of electromagnetic radiation that are used in magnetic resonance imaging (MRI). 2. Describe the potential safety concerns regarding MR safety in the MR environment. 3. Explain the American College of Radiology (ACR) Magnetic Resonance Safe Practice Guidelines. 4. Discuss patient comfort with regards to anxiety, contrast administration, monitoring and sedation, and pregnancy. 5. Review the suggested guidelines for the prevention of burns to patients in the MR environment. TARGET AUDIENCE Course objectives for this program specifically target MR technologists. Other technologists and medical personnel may also benefit from viewing this program. While not limited to this audience group, the technical content is most effective when applied to people with this training. NOTE: Regardless of your imaging specialty, you may apply for continuing education credit. Refer to the Continuing Education Credit page for additional information. CONTINUING EDUCATION CREDIT 1.0 ASRT-approved Category A CE Credit 3 of 27

4 CONTINUING EDUCATION CREDIT After viewing the TiP-TV video presentation and reading this program supplement, please complete the required online CE credit activities (test and feedback form). The TiP-TV test measures knowledge gained and/or provides a means of self-assessment on a specific topic. The feedback form provides us with valuable information regarding your thoughts on the program s quality and effectiveness. Online Process for CE Credit TiP-TV satellite broadcast subscribers can go online to obtain CE credit quickly and easily! hls.gehealthcare.com 1. View the entire video presentation this is a requirement for obtaining CE credit. This supplement is not intended to replace watching the video presentation. 2. Go to the Learning System (HLS) web site at hls.gehealthcare.com and complete the post-program test.! You have up to three attempts to successfully complete the test with a passing score of 75% or higher.! The test must be completed without aids or assistance of any kind; this is an individual effort. 3. Complete the feedback form. 4. Upon successful completion of the online CE information, you can instantly print a certificate. The HLS allows ASRT members to immediately submit a record of the completed course to the ASRT for CE credit tracking. CONTINUING EDUCATION CREDIT ELIGIBILITY - IMPORTANT NOTICE! A TiP-TV course may be available in several different formats, such as, but not limited to, a broadcast, online web course, or videotape. You may only be able to receive CE credit once for a particular course, regardless of the format in which it was viewed. If you have already applied for and/or received CE credit for this course, you are encouraged to contact your CE certification organization (ARRT, ARDMS, NMTCB, etc.) to determine if you can repeat this course for CE credit. Thank you for choosing as your continuing education partner. We hope you will join us for other TiP-TV programs in the future. For more details and program schedule information, please visit: If you have a question or comment on the program content, please send a message to: PSTIPApps-mr@med.ge.com 4 of 27

5 INTRODUCTION Are you concerned about MR safety? You should be concerned. The magnetic force of the MR environment can be deceiving. To ensure the safety of our patients, the staff, and other individuals exposed to the MR environment, it is critical that all MR professionals continuously follow the MR Safety Guidelines and standards for a safe MR environment. The expanding capability of magnetic resonance studies has a great impact on the medical diagnosis and prognosis of disease processes. These expanded capabilities have dramatically increased the number of MR procedures performed worldwide. Many more patients, especially those in high-risk or special population groups, are undergoing MR procedures for an ever-widening spectrum of medical indications. For these reasons, we as MR professionals must continue to strive for a safe MR environment. A wide range of topics on MR safety will be covered in this program: Static and gradient magnetic fields Radiofrequency heating Importance of a solid screening program Understanding MR safety in regards to implants, devices, and other objects Monitoring patients Contrast issues Pregnancy More MR safety updates 5 of 27

6 ELECTROMAGNETIC RADIATION Electromagnetic Radiation is energy radiated in the form of a wave caused by the motion of electric charges. A moving charge gives rise to a magnetic field, and if the motion is changing or accelerating, then the magnetic field varies, and in turn produces an electric field. Figure 1 Hydrogen Atom MR is the absorption or emission of electromagnetic energy by nuclei in a static magnetic field after excitation by a suitable radiofrequency or RF pulse. The current application involves imaging the distribution of hydrogen nuclei or protons in the body (Figure 1). The hydrogen nuclei are used because of their highly magnetized nature and abundance in the human body. Figure 2 Hydrogen Atom Alignment When a patient is placed in the presence of a strong magnetic field, hydrogen atoms align with the external magnetic field. Some hydrogen atoms align parallel while others align anti-parallel to the static magnetic field (Figure 2). The factors affecting which hydrogen nuclei align parallel and which align anti-parallel are determined by the strength of the external magnetic field and the thermal energy level of the nuclei. Low thermal energy nuclei do not possess enough energy to oppose the magnetic field in the anti-parallel direction. High thermal energy nuclei do possess enough energy to oppose this field. In equilibrium, there are always fewer high-energy nuclei than low energy nuclei. For that reason, the magnetic moments of the nuclei aligned parallel to the magnetic field cancel out the smaller number of magnetic moments aligned anti-parallel. Figure 3 Precessing Proton In addition to the hydrogen atoms aligning with the static magnetic pole, another phenomenon occurs. These hydrogen atoms are also spinning like a gyroscope (Figure 3). Therefore, they are precessing as they spin. At some point, an RF pulse will be transmitted towards the hydrogen atoms, which eventually produces a signal. This signal from the hydrogen atoms produces an MR image. 6 of 27

7 STATIC MAGNETIC FIELD MR patients are exposed to various electromagnetic radiation variants (such as static magnetic field, gradient magnetic field and radiofrequency). The forces and torques produced by the static magnetic field are important issues to address. Interview with Daniel J. Schaefer, Ph.D. Notes: Static Magnetic Fields, Forces and Torques Forces depend on the product of the magnetic field and its spatial rate of change = B db/dt For the same geometry, forces increase with B 2 Due to field geometry => low field open forces may be greater than high field Forces from shielded magnets drop faster than from unshielded ones, However: The peak force is typically higher. Approaching the magnet, shielded magnet forces become overwhelmingly more abruptly than for unshielded magnets. Alignment torgues on non-spherical objects may be 90 times greater than forces Figure 4 Static Magnetic Fields Flow Potentials 7 of 27

8 STATIC MAGNETIC FIELDS: VERTIGO & NAUSEA Schenck model: B0/motion-induced pressure inner ear in semi-circular canals: P = abωb 2 /ρ P = pressure, a=inner canal radius, b=outer canal radius B = magnetic field strength, Ω=radian velocity of head ρ = resistivity of fluid Percent experiencing vertigo (Schenck): At 4T: 89% At 1.5T: 42% Probability of vertigo falls with field strength and head velocity: P_threshold = 1.25 E-05 N/m 2 a = 1.5 E-04 m, b = 0.003m ρ = 0.5 ohm m, Ω = 10.5 rad/s P = 1.5 E-04 at 4T Figure 5 Inner ear cupula 2a 2b Interview with Frank Shellock, Ph.D. Notes: Bioeffects and Safety Issues to Static Magnetic Field Static magnetic field associated with the MR system is ALWAYS on. Prominently display appropriate signs in and around the room of the MR system. Proper procedures must be in place to control access to the MRI environment. Static Magnetic Field FDA/CDRH Criteria for Significant Risk Investigations of Magnetic Resonance Diagnostic Devices Issued 7/14/2003 Population Adults, children, and infants aged > one month Neonates, i.e., infants aged one month or less Static Magnetic Field 8 Tesla 4 Tesla 8 of 27

9 Missile Effect One of the more critical MRI safety issues to consider regarding the static magnetic field is the "missile effect." The "missile effect" refers to the capability of the fringe field component of the static magnetic field to attract a ferromagnetic object, drawing it into the scanner by considerable force. The "missile effect" can pose a significant risk to the patient inside the MR scanner and/or anyone in the path of the projectile. The projectile can cause substantial damage to the MR system, even if there is no injury to a patient or individual. It is imperative to be aware of the "missile effect" and the potential hazards that it can cause. Not only can this seriously affect patients and other individuals, it can also be a costly expense if the projectile damages the MR system. Missile related accidents from oxygen tanks have resulted in at least one fatality, several injuries, and substantial damage to MR systems. One case resulted in a fatality that occurred in July of This accident was highly publicized in the lay press. To guard against accidents from projectiles, the general area associated with the MR system must have supervised and controlled access. Signs must be placed on the entrance to the MR system room. It is also important to place a sign on or near the door frame so that it can be seen when the door is opened. This sign clearly states: DANGER! THIS MAGNET IS ALWAYS ON. The List over 1,300 objects Latest safety information Regular updates on all topics Search engine response GRADIENT MAGNETIC FIELD Coils of wire situated within the bore of the magnet generate magnetic field gradients. The laws of electromagnetic induction state that when current is passed through a gradient coil, a magnetic field or gradient field, as it is known, is induced. This gradient field interacts with the main static magnetic field so that the magnetic field strength along the axis of the gradient coil is altered in a linear fashion. Figure 6 Gradient Coils The gradient coil is composed of three sets of wire coils (X, Y, and Z) wrapped around a fiberglass cylinder located within the magnet housing shown in Figure 6. Electric current flows through these gradient coils and is turned on and off very rapidly producing expansion and contraction of the gradient coils. This expansion and contraction creates the tapping sound heard when scanning. X Z Y 9 of 27

10 Interview with Frank Shellock, Ph.D. Notes: The Potential of Gradient Fields to Produce Peripheral Neurostimulation in Patients During MRI is Dependent on a Variety of Factors: The peak gradient amplitude The current density The duration of the induced voltage The orientation of the gradient magnetic fields relative to the patient s tissues The size of the greatest diameter of the patient s body The sensitivity of the tissue to respond to induced currents Gradient Magnetic Field FDA/CDRH Criteria for Significant Risk Investigations of Magnetic Resonance Diagnostic Devices Issued 07/14/03 Any time rate of change of gradient fields (db/dt) sufficient to produce severe discomfort or painful nerve stimulation Acoustic Noise Acoustic noise is another MRI safety issue related to gradient magnetic fields. Acoustic noise is generated by the time-varying, magnetic fields during the operation of an MR procedure. This noise occurs during the rapid alterations of currents within the gradient coils. The greatest levels of acoustic noise are typically caused by: Higher field strength MR systems using faster imaging procedures Thinner slice selections Smaller fields of view Shorter repetition times Shorter echo times Because excessive noise is known to be one of the most common causes of hearing loss, whenever loud noises are anticipated to be present, it is important to provide patients with hearing protection during MRI procedures.the simplest and least expensive means of preventing problems associated with acoustic noise is to routinely use disposable earplugs or noise attenuation headphones. 10 of 27

11 Various types of acoustic noise are produced during the MR examination. The problems associated with acoustic noise for patients and healthcare workers include: Simple annoyance Difficulties in verbal communication Heightened anxiety Temporary hearing loss In extreme cases, the potential for permanent hearing impairment So, it is recommended that you use hearing protection for MR patients. RADIOFREQUENCY (RF) The majority of the RF power transmitted for MR imaging is transformed into heat within the patient's tissue as a result of resistive losses. The primary bioeffects associated with exposure to RF radiation is related to the thermogenic quality or heat production of this electromagnetic field. Interview with Frank Shellock, Ph.D. Notes: The last of the three electromagnetic fields used for MR procedures is RF energy. RF energy is non-ionizing, electromagnetic radiation. RF fields are used during magnetic resonance procedures to excite protons. During the MRI procedure, the patient absorbs a portion of the transmitted RF energy, which may result in tissue heating due to resistive losses. Not surprisingly, whole-body and localized heating are the primary safety concerns associated with the absorption of RF energy. The amount of RF power deposition that is associated with an MR procedure is a complex function of numerous variables. These variables include: The frequency (which, in turn, is determined by the strength of the static magnetic field of the MR system) The type of RF pulse used The repetition time The type of RF coil used The type and volume of tissue contained within the coil Other factors The potential for RF power absorption to lead to excessive temperature increases in patients tend to be more of an issue for MRI procedures conducted using high field strengths. That is, those MR systems operating at 1.5T or higher. 11 of 27

12 Thermoregulatory and other physiologic changes that human subjects exhibit in response to exposure to RF radiation are dependent on the amount of energy that is absorbed. The dosimetric term used to describe or to characterize the absorption of RF radiation is the specific absorption rate, or SAR. The unit of measurement used for SAR is watts per kilogram (W/kg). Currently, the United States Food and Drug Administration (FDA) recommends the following criteria for RF exposure that are considered to be acceptable levels for clinical MR procedures: 4 W/kg averaged over the whole body during a 15-minute period 3 W/kg averaged over the head during a 10-minute period 8 W/kg averaged in any one gram of tissue involving the head or torso during a 15-minute period 12 W/kg averaged in any one gram of tissue of the extremities during a 15-minute period Fortunately, MR systems operating within the current FDA recommendations will not deposit excessive RF power nor produce excessive tissue temperatures, even for patients with reduced thermoregulatory capabilities. Potential Heating Since the topic of potential heating is under discussion, let's discuss other aspects of MRI procedures that may induce excessive temperature increases that can result in first-, second-, and even third-degree burns. Most reports of excessive temperatures that caused patient injuries, namely burns, were related to the presence of conductive materials touching the patients. This mainly occurred when the conductive materials formed a coil or loop or for those that have an elongated shape. Importantly, induced currents may result in excessive heating and burn injuries for certain implants, devices, or accessories, even when the MR system is operating within recommended SAR levels. Implants or devices that have an elongated shape or form a closed loop, that have conductive leads or components, especially if they are damaged, may present increased risks for burns in patients undergoing MRI procedures. For example, excessive heating has been reported under certain MR operating conditions for the following: Neurostimulation systems Cardiac pacemakers Halo vests and cervical fixation devices Transdermal medication patches RF coils (especially if damaged) Electrocardiogram (EKG or ECG) leads Plethysmographic leads Pulse oximeters Therefore, special precautions must be followed whenever these types of devices are present. The prevention of excessive heating and burns in the MRI environment requires an understanding of safety criteria for certain electrically-conductive implants and devices, as well as an appreciation of the proper use of accessories such as monitoring equipment and surface coils. Important guidelines that prevent burns may be reviewed by visiting 12 of 27

13 MR SCREENING Patient and personnel screening is the most effective way to avoid potential safety hazards to patients. Careful questioning and education of patients and all personnel can produce a controlled MR environment. This is achieved by utilizing a comprehensive screening form that is completed by all individuals entering the magnetic field. Healthcare workers who are specially trained in MR safety should screen patients and other individuals. The top portion of this form states: "The MR system has a very strong magnetic field that may be hazardous to individuals entering the MR environment." Therefore, all individuals are required to fill out this form BEFORE entering the MR environment. THE MR SYSTEM MAGNET IS ALWAYS ON. Comprehensive patient screening involves three concepts: The use of a printed form to document the screening procedure. A review of the information on the screening form. A verbal interview to verify the information on the form. Note that undergoing previous MR procedures without incident does not guarantee a safe subsequent MR examination. A written screening form must be completed each time a patient prepares to undergo an MR procedure. If there are patient limitations related to the ability to complete the MR Safety Form, an appropriate advocate should be involved in the screening process to verify any information that may impact patient safety. Versions of this form should also be available in other languages as needed. Interview with Frank Shellock, Ph.D. Notes: The Institute of Magnetic Resonance Safety, Education, and Research (IMRSER) recently reviewed information pertaining to screening and developed forms to be used to screen patients and other individuals.this information, along with newly developed and completely revised screening forms, may be found at Please note there are two separate screening forms (for screening patients and for individuals) that may need to enter the MRI environment. Both of these forms are in a format that allows you to easily download and use them for your MRI facility. By requiring the completion of these written screening forms and verifying the information, your MRI facility will ensure that health conditions or items that may pose safety issues or other problems will not be missed. The screening forms list questions that should be posed to patients and other individuals to identify areas of concern. These should be addressed prior to allowing entry into the MRI environment. 13 of 27

14 IMPLANTS AND DEVICES The magnetic field interaction with implants and devices is an important consideration. Translational attraction and/or torque may cause movement or dislodgement of a ferromagnetic implant resulting in an uncomfortable sensation or injury to a patient or individual. Translational attraction is proportional to the strength of the static magnetic field, the strength of the spatial gradient, the mass of the object, the shape of the object, and the magnetic susceptibility of the object. The effects of translational attraction on external and implanted ferromagnetic objects are predominant hazards in the immediate area around the MR system. A good tip regarding a 3T magnet is that we may not feel the strong force at first, but as soon as we approach the bore of the magnet, the magnetic force increases dramatically. A discussion on various types of implants, devices, and other objects will be presented regarding force, MR safety, and compatibility. Interview with Frank Shellock, Ph.D. Notes: Figure 7 Reference Manual for Magnetic Resonance Safety, Implants, and Devices Magnetic resonance procedures may be contraindicated for patients primarily because of risks associated with movement or dislodgment of a ferromagnetic implant, device, or other objects. In addition, the MRI environment may be hazardous for individuals with certain implants There are other possible hazards and problems related to the presence of a metallic object or implant that include the following: Induction of currents (that is, in materials that are conductors). The production of excessive heating. The alteration in the functional aspects of the device. The misinterpretation of an imaging artifact as an abnormality. To date, more than 1,300 implants and objects have been tested for MR-safety or MR-compatibility. Over 300 of these objects have been tested in association with 3T MR systems. This information is readily available online for all MRI healthcare professionals and lay people at Note: This reference manual is updated annually. 14 of 27

15 MRI healthcare professionals should follow the general guidelines where MRI procedures should only be performed on a patient with a metallic object that has been previously tested and demonstrated to be safe. The important safety aspects for a given implant or device may be relative to specific conditions, such as the field strength of the MR system and the level of RF power that is utilized for the imaging procedure. A similar guideline should be followed when deciding whether or not to allow an individual with an implant or device into the MRI environment. Various factors influence the risk of performing an MRI procedure in a patient with a metallic object, including: Strength of the static magnetic field Degree of ferromagnetism of the object Its magnetic susceptibility Mass of the object Geometry or shape of the object Location and orientation of the object in vivo Presence of retentive mechanisms (such as fibrotic tissue, bone, or sutures) Length of time the object has been in place With the increased used of 3T MR systems, it is important to verify that the implant or device present in the patient referred for an MRI procedure underwent evaluation relative to the use of a 3T scanner. This evaluation should typically involve assessments of magnetic field interactions and heating. This is especially important because it is possible for an implant that displayed "weakly" ferromagnetic qualities in association with a 1.5T scanner to present a substantial safety hazard at 3T. Furthermore, because of the difference in the frequencies used at 1.5T vs. 3T, the heating characteristics for an elongated implant or one that forms a closed loop may be significantly different. The presence of an intracranial aneurysm clip in a patient referred for an MRI procedure or an individual that needs to enter the MRI environment represents a situation requiring the utmost consideration because of the associated serious risks. There are many different types of aneurysm clips. Aneurysm clips made from magnetic forms of stainless steels are an absolute contraindication to the use of MRI procedures, because excessive magnetic field interactions may displace these clips and cause serious injury or death. By comparison, specific aneurysm clips classified as "nonferromagnetic" or "weakly ferromagnetic" have been tested and shown to be safe for patients undergoing MRI procedures, at field strengths up to and including 8T. For example, aneurysm clips made from Phynox, Elgiloy, titanium alloy, or commercially pure titanium are generally safe for patients undergoing MRI procedures. In consideration of the current knowledge pertaining to aneurysm clips, the following guidelines are recommended: Specific information about the aneurysm clip must be known. You must have information pertaining to the manufacturer, the type or model number, and know what material was used for the clip in question. The aneurysm clip should have been tested at the same field strength that will be used for the intended MRI procedure. That is, do not assume that an aneurysm clip shown to be safe at 1.5T is safe for an examination to be performed using a 8T scanner. 15 of 27

16 Figure 8 demonstrates slight artifacts from aneurysm clips (the arrows indicate artifacts). Figure 8 Aneurysm Clip In general, the implanting surgeon is responsible for entering this information in the patient's or individual's records. An aneurysm clip that is in its original package and made from Phynox, Elgiloy, MP35N, titanium alloy, commercially pure titanium, or other material known to be nonferromagnetic or weakly ferromagnetic does not need to be evaluated for ferromagnetism, and is considered to be safe relative to the field strength that was used to test it. The radiologist and implanting surgeon should ultimately be responsible for evaluating the available information pertaining to the aneurysm clip, for verifying its accuracy, and for deciding to perform the MRI procedure. Patients that have most of the hemostatic vascular clips, fasteners, and staples listed on are not at risk for injury during MRI procedures. Currently, there is one hemostatic clip that is an exception to this the Resolution clip. This clip currently has labeling that states it is contraindicated for a patient undergoing an MRI procedure. Many heart valve prostheses and annuloplasty rings have been evaluated for MR safety using MR systems operating at field strengths as high as 3T. The majority of these implants displayed measurable yet relatively minor magnetic field interactions. However, because the actual attractive forces exerted on these cardiovascular implants were minimal compared to the force exerted by the beating heart, an MRI procedure is not considered to be hazardous for a patient that has any of the heart valve prostheses or annuloplasty rings that have undergone testing, to date. With respect to clinical MRI procedures, there has never been a report of a patient injury related to the presence of a heart valve prosthesis or annuloplasty ring. External hearing aids are included in the category of electrically activated implants or devices that may be found in patients referred for MRI procedures. The magnetic fields used for MRI examinations can easily damage these devices. Therefore, a patient or other individual with an external hearing aid must not enter the MRI environment due to the possible risk of damage to the device. Fortunately, to prevent damage to the device, an external hearing aid can be readily identified and removed from the patient or individual prior to permitting entrance to the MRI environment. 16 of 27

17 Other hearing devices exist that have external components, as well as pieces that are surgically implanted in or near the ear. Because the powerful magnetic field of the MR system may adversely affect these devices, patients must not be allowed into the MRI environment because of the possibility of damaging the implanted components. ACR White Paper Various types of coils, filters, and stents were evaluated for safety with MR systems. Several of these demonstrated magnetic field interactions in MR scanners. The American College of Radiology (ACR) "White Paper on MR Safety: 2004 Update and Revisions" focused on additional areas of concern. This paper addresses four new topics and several additions and revisions to the original paper published in 2002: Drug Delivery Patches and Pads Pediatric MR Safety Fetal MR Contrast Agent Safety Concerns MR scanning of patients in whom there are or may be cardiac pacemakers and/or implanted cardioverter defibrillators (ICDs) This information was published in the American Journal of Radiology in May As the field of MR continues to evolve, regular monitoring of potential safety hazards and issues will be addressed and updated appropriately. Keeping abreast of MR Safety issues is crucial for an MR safe environment. Interview with Frank Shellock, Ph.D. Notes: There appears to be much confusion regarding performing MRI procedures in patients with coils, filters, and stents. There are many different types of implants that fall into this category. It should be noted that new coils, filters, and stents are being developed on a continuing basis. Therefore, there are NO general MRI safety recommendations for these implants, as it is necessary to know the particular type of implant in question before it can be determined if an MRI procedure may be performed safely in a patient with a coil, filter, or stent. In fact, here is an example of a translational attraction for a Zenith AAA stent graft. This implant is contraindicated for MRI procedures. Notice the substantial translational attraction exhibited by this stent during exposure to a 1.5T MR system. 17 of 27

18 Therefore, for coils, filters, and stents, the following is recommended: Specific information about the coil, filter, or stent must be known, especially with respect to the material used to make the implant. If the implant is made from nonferromagnetic material, an MRI procedure may be performed immediately after placement. In fact, some MRI facilities deploy intravascular stents under MR-guidance at 1.5T. If the coil, filter, or stent is made from "weakly ferromagnetic" material, it may be necessary to wait a period of six to eight weeks to allow for tissue ingrowth to help retain the implant in place. Currently, there are many types of Bare metal and Drug Eluting Coronary stents that are being used in patients on a regular basis. Many of these coronary artery stents have now undergone MR safety testing at 3T and most of them have been shown to be safe for patients undergoing MR procedures immediately after they have been implanted in these individuals. For specific information on Bare metal and Drug Eluting stents, please refer to the MR safety web site at There are many different types of magnetically activated devices, including dental implants, tissue expanders, stoma plugs, and prosthetic appliances. Many of these may be problematic for patients and others in the MRI environment. Guidelines for managing patients and individuals with magnetically-activated implants may be reviewed by visiting In the past, the presence of an electronically-activated implant or device was generally considered to be a strict contraindication for a patient or individual in the MRI environment. Since comprehensive studies have recently defined safe guidelines for certain devices, there are now several electronically activated devices that are considered to be safe for patients undergoing MR procedures. For example, studies have been performed that identified the safe means of performing MR procedures in patients with certain electronically activated implants, including: Implantable bone fusion stimulator Certain cochlear implants A programmable infusion pump Certain neurostimulation systems. These studies identified highly specific criteria for the safe use of MR imaging when these devices are present in patients. These specific devices have FDA-approved labeling that is highly specific to the conditions that must be followed to ensure safety for the patient. Cardiac pacemakers are generally considered to be strictly contraindicated for patients referred for MRI procedures and individuals who need to enter the MRI environment. These devices present potential problems from several mechanisms, including: Possible movement of the pulse generator due to interaction with the MR system Temporary or permanent modification of the function of the device Excessive heating of the pacemaker leads Electromagnetic interference of these devices by the operation of the MR system 18 of 27

19 However, much of this information really pertains to older cardiac devices. Because of the reduction in ferromagnetic components, improved circuitry, and enhanced electromagnetic interference capabilities of "modern-day" pacemakers, reports have indicated that patients with certain devices may safely undergo MRI procedures using MR systems operating from 0.5T to 2T by following highly specific guidelines. These safety guidelines include the following: Scanning only nonpacemaker dependent patients. Having a cardiologist/electrophysiology specialist present throughout the procedure. Having advanced cardiac life support personnel present during the exam. Having the ability to interrogate the pacemaker before and after the MRI scan. Possibly reprogramming the device prior to the MRI procedure. Only performing certain types of MRI exams with associated risk (such as MRI of the brain). Limiting the amount of RF power used for the exam. Monitoring the patient with proper equipment throughout the MRI procedure. Being prepared to intervene in the event of an emergency. Apparently, the MRI safety issues and concerns for modern-day pacemakers may have been overstated. It is important to understand that the MRI facilities that scan patients with cardiac pacemakers do this only under highly controlled conditions. Additional studies are warranted on this topic to define criteria that may be followed to allow MRI procedures to be used in patients with certain cardiac pacemakers. There are many other implants, devices, and objects that may be encountered in patients referred for MRI procedures, or in individuals that may need to enter the MRI environment. A comprehensive listing of information for these may be reviewed on the web site Over the years, there has been a great deal of confusion regarding the issue of performing an MRI procedure during the post-operative period in a patient with a metallic implant or device. In general, if the metallic object is a "passive implant" (that is, there is no power associated with the operation of the implant) and it is made from a nonferromagnetic material, the patient may undergo an MRI procedure immediately after placement of the object, by using an MR system operating at the field strength that was used to assess safety for the particular implant. However, for a metallic object that is "weakly" magnetic, it is often necessary to wait a period of 6 to 8 weeks before allowing the patient to undergo the MRI procedure. If there is any concern regarding the integrity of the tissue with respect to its ability to retain the object in place during an MRI procedure or during exposure to the MRI environment, the patient or individual should not be allowed to enter the MR system room. 19 of 27

20 PATIENT CARE IN MR MR healthcare workers must carefully consider the ethical and medico-legal ramifications of providing proper patient care, including: Guidelines to prevent excessive heating and burns associated with MR procedures (discussed earlier). Handling of patients who may experience anxiety and/or claustrophobia. Safety issues regarding the administration of contrast for MR exams. Recommendations for using sedation on patients requiring an MR examination and patients who require monitoring in the MR environment. A review of the recommended guidelines for imaging pregnant patients and recommendations for the pregnant MR technologists. Interview with Frank Shellock, Ph.D. Notes: MONITORING Another topic of great importance is patient monitoring in the MRI environment. Monitoring a patient during an MRI examination is indicated whenever a patient requires observations of vital physiologic parameters due to an underlying health problem, or whenever a patient is unable to respond to the MRI technologist or other healthcare worker regarding pain, respiratory problem, cardiac distress, or any other difficulty that may arise during the examination. Conventional monitoring equipment and accessories were not designed to operate in the harsh MRI environment, where electromagnetic fields can adversely effect or alter the operation of these devices. Fortunately, various monitors and other patient support devices have been developed or specially modified to perform properly during MRI procedures. Other patient support devices may be required for different patient populations that require physiologic monitoring. Only devices and equipment demonstrated and verified to be safe for use in the MRI environment should be used. Support devices that are commercially available for use in the MRI environment include gurneys, oxygen tanks, stethoscopes, suction devices, infusion pumps, power injectors, ventilators, and gas anesthesia systems. Only healthcare professionals with appropriate training and experience should be responsible for monitoring patients and using proper support devices during MRI procedures. 20 of 27

21 CONTRAST Gadolinium-based contrast agents are commonly used for MRI exams, and their utilization is increasing. Safety issues and the potential for adverse effects associated with MRI contrast agents need to be addressed. There are five major gadolinium-based, intravenous MRI contrast agents used in the United States. The use of these contrast agents for MRI procedures is a well-established, clinical practice. Numerous investigations have been performed to assess the safety aspects of these MRI contrast agents. Studies have reported that the overall safety profiles for the five different intravenous MRI contrast agents are comparable. Importantly, there is an extremely low incidence of adverse events. In the rare cases when anaphylactoid responses have been reported, the incidence of these more serious side effects is similar for the five different MRI contrast agents. In fact, the gadolinium-based MRI contrast agents are considered to be among the safest intravenous drugs in use today. ANXIETY AND CLAUSTROPHOBIA For some of the millions of patients who undergo MRI procedures every year, the experience may cause great emotional distress. In its mildest form, distress is the normal amount of anxiety most persons will experience when undergoing a diagnostic procedure. Claustrophobia is a disorder characterized by the marked, persistent, and excessive fear of enclosed spaces. In such affected individuals, exposure to enclosed spaces such as the MRI environment almost invariably provokes an immediate anxiety response. There are several techniques that can be used to manage stress in the MRI environment. These include: Prepare and educate the patient. Allow an appropriately-screened relative or friend to remain with the patient in the MR room. Maintain physical or verbal contact with the patient. Use MRI compatible headphones. Position the patient feet first or prone in the MR system. 21 of 27

22 MR PROCEDURE FOR PREGNANCY Pregnancy Patient The use of diagnostic imaging is often required in evaluating pregnant patients. The question of whether or not a patient should undergo an MRI procedure during pregnancy often arises. Unfortunately, there have been too few studies directed toward determining the relative safety of using MRI procedures for pregnant patients. According to the International Society for Magnetic Resonance in Medicine (ISMRM) and the current American College of Radiology (ACR), pregnant patients can be accepted to undergo MR scans at any stage of pregnancy. In the determination of the designated radiologist and referring physician, the risk-benefit ratio warrants an MRI study when: Ultrasound is not satisfactory. MR data is needed to potentially affect the care of the patient and/or fetus. Referring physician does not feel that it is prudent to wait to obtain this data until after the patient is no longer pregnant. It is recommended that pregnant patients undergoing an MRI exam be provided written and verbal informed consent to document that they understand the risk/benefit of the MRI procedure to be performed. Pregnancy Technologist According to the safety guidelines, pregnant MRI technologists and healthcare workers are allowed to perform MRI procedures. The MRI technologist can enter the MR system room and attend to the patient during pregnancy, regardless of the trimester. However, it should be noted that technologists and healthcare workers should not remain within the MR system room or magnet bore during the actual operation of the scanner. ACR MR SAFE PRACTICE GUIDELINES The ACR has updated the ACR Practice Guidelines and Technical Standards for MR Safety. It is the intent of the ACR that these guidelines will be helpful as the field of MR evolves and matures. These guidelines are intended to ensure that MR is not only a powerful diagnostic tool, but also a safe one. According to the ACR Magnetic Resonance Safe Practice Guidelines, the following are recommended to establish, implement, and maintain current MR safety policies and procedures: All clinical and research MRI sites should maintain a MR Safety Policies and Procedures manual. All changes should be upgraded and documented in the MR Safety Policies and Procedures manual. Each site will name an MR Medical Director whose responsibilities include ensuring that the MR Safe Practice Guidelines are established and maintained. Procedures for documenting MR safety incidents or "near incidents" that occur at the MR site should be reported to the Medical Director of the MR sites, preferably within 24 hours. Check the ACR website for updates to the ACR White Paper on MR Safety and other MR safety issues at 22 of 27

23 APPENDIX A: PRESENTERS Denise Lukasik-Sedmak, Ed.D., R.T. (R)(M)(MR)(CT) MR TiP-TV Program Manager Frank Shellock, Ph.D. President, MR Testing Services Adjunct Clinical Professor of Radiology University of Southern California Los Angles, California Daniel J. Schaefer, Ph.D. Principal Engineer DI MR Engineering Waukesha, Wisconsin Special Contributor Waukesha Memorial Hospital Outpatient Center at the D.N. Greenwald Center Waukesha, Wisconsin APPENDIX B: RESOURCES American College of Radiology (2004). (Online). "White Paper on MR Safety: 2004 Update and Revisions": American Journal of Radiology (2004). "White Paper on MR Safety: 2004 Update and Revisions". Shellock, F. (2005). Reference Manual for Magnetic Resonance Safety, Implants, and Devices: 2005 Edition. Los Angeles, California: Biomedical Research Publishing Group. Westbrook, C. and Kaut, C. (1998). MRI in Practice. Malden, Massachusetts: Blackwell Science. Electronic Resources American College of Radiology: Institute for Magnetic Resonance Safety, Education and Research: International Society of Magnetic Resonance in Medicine: MRI Safety website: NOTE: The Internet is an ever-evolving environment and links are subject to change without notice 23 of 27

24 APPENDIX C: GLOSSARY ACR: American College of Radiology B 0 : Static magnetic field or main magnetic field BOLD: Blood Oxygenation Level Dependent CE: Continuing education Contrast-to-Noise Ratio (CNR): Ratio of the absolute difference in intensities between two regions to the level of fluctuations in intensity due to noise. Coronal: The horizontal plane along the longitudinal axis of the body dividing it into anterior and posterior halves. CSF: Cerebrospinal fluid CNR: Contrast-to-noise ratio Echo Planar Imaging: EPI EPI: Echo planar imaging ETL: Echo train length Field of View (FOV): The area of the anatomy being imaged, usually expressed in centimeters. FLASH: Fast low angle shot fmri: Functional magnetic resonance imaging FOV: Field of view Frequency: The scanning direction associated with the frequency gradient. Usually corresponds to the image s long axis. FSE: Fast spin echo GAD, gd, or Gd: Gadolinium Magnetic Resonance (MR): The absorption or emission of electromagnetic energy by nuclei in a static magnetic field after excitation by a suitable RF pulse. Magnetic Resonance Imaging (MRI): The creation of images using the magnetic resonance phenomenon. The current application involves imaging the distribution of hydrogen nuclei (protons) in the body. The image brightness in a given region usually depends jointly on the spin density and the relaxation times. Image brightness is also affected by motion, such as blood flow. Magnetic Resonance Signal: The electromagnetic signal (in the radiofrequency range) produced by the precession of the transverse magnetization of the spins. The rotation of the transverse magnetization induces a voltage in the coil. This voltage is amplified by the receiver. N/A: Not applicable Phase Encoding: The act of localizing an MR signal by applying a gradient pulse to alter the phase of spins before signal readout. Proton Density-Weighted (PD-Weighted): Images that have contrast that is primarily due to the number of protons in the structures. PD-weighted images result when scan timing parameters are selected that minimize the T1 (long TRs) and the T2 (short TEs) contrast effects. R/L: Right/left 24 of 27

25 Radiofrequency (RF): The frequency (intermediate between audio and infrared frequencies) used in magnetic resonance systems to excite nuclei to resonance. Radiofrequency Pulse (RF Pulse): A burst of RF energy, if it is at the correct Larmor frequency, rotates the macroscopic magnetization vector by a specific angle, depending on the amplitude and duration of the pulse. Repetition Time (TR): The time between successive excitations of a slice. That is, the time from the beginning of one pulse sequence to the beginning of the next. In conventional imaging, it is a fixed value equal to a user-selected value. In cardiac-gated studies, however, it can vary from beat to beat depending on the patient s heart rate. SE: Spin echo S/I: Superior/inferior SNR: Signal-to-noise ratio Spatial Encoding: Selective identification of the signal within the imaging volume. Spin Echo Imaging (SE Imaging): A magnetic resonance imaging technique where the spin echo magnetic resonance signal rather than the free induction decay is used. SR: Spatial resolution T/R: Transmit/receive T: Tesla T1: The characteristic time constant for the magnetization s return to the longitudinal axis after being excited by an RF pulse. Also called spin lattice or longitudinal relaxation time. T1-Weighted: Scan protocols that allow the T1 effects to predominate over the other relaxation effects. T2*: The characteristic time constant for loss of transverse magnetization and MR signal due to T2 and local field inhomogeneities. Since such inhomogeneities are not compensated for by gradient reversal, contrast in gradient echo images depends on T2*. T2*-Weighted: Scan protocols that allow the T2* effects to predominate over the other contrast effects. There are three primary gradient echo pulse sequences that can be used to produce varying T2*-weighted images: gradient echo, SPGR, and SSFP. T2: The characteristic time constant for loss of phase coherence among spins caused by their interaction and the resulting loss in the transverse-magnetization MR signal. Also referred to as spin-spin or transverse relaxation time. T2-Weighted: Scan protocols that allow the T2 effects to predominate over the other contrast effects. TE: Time of echo Time of Echo (TE): The time between the center of the excitation pulse and the peak of the echo, usually occurring at the center of the readout. TR: Time of repetition or repetition time 25 of 27

26 APPENDIX D: POST-TEST LMS Course Number: 3017 To be eligible for CE credit, you MUST view the video presentation first and then submit your answers using the online process (go to hls.gehealthcare.com). All tests must be completed by 11:59 p.m. Central Time on the due date listed in the online test module. 1. The nuclei are used in magnetic resonance imaging (MRI) because of their abundance in the human body and they are highly magnetized. a. carbon b. hydrogen c. phosphor d. sulfur 2. Magnetic resonance (MR) patients are exposed to all of the following electromagnetic radiation variants EXCEPT. a. gradient magnetic field b. radiofrequency c. mechanical field d. static magnetic field 3. The gradient coil is composed of three sets of wired coils that are called. a. X, Y, and Z b. X, Y, and Q c. V, W, and X d. W, X, and Y 4. Which of the following variables does NOT produce peripheral neurostimulation in patients during MRI? a. The peak gradient amplitude b. The magnet s bore c. The current density d. The size of the greatest diameter of the patient s body 5. The primary bioeffects associated with exposure to radiofrequency radiation are related to of this electromagnetic field. a. acoustic noise b. peripheral neurostimulation c. heat production d. missile effect 6. The unit of measurement used for specific absorption rate (SAR) is. a. W/kg b. C/kg c. cycles/s d. mg/dl 7. A comprehensive MR safety patient screening involves all of the following concepts EXCEPT. a. the use of a printed screening form b. documentation c. verbal interview d. insurance coverage 26 of 27