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ACR Guidance Document for Safe MR Practices: 2007

¹ Department of Radiology, University of Pittsburgh Medical Center, Pittsburgh, PA.
² Neuroradiology Section, University of California San Francisco, San Francisco, CA.
³ American Society of Anesthesiologists and Department of Anesthesiology, New York University School of Medicine, New York, NY.
⁴ Colorado Springs Radiologists, Colorado Springs, CO.
⁵ Professor and Chairman, Department of Radiology, University of California San Diego, San Diego, CA.
⁶ Department of Radiology, University of Minnesota, Minneapolis, MN.
⁷ MRI-Planning, Kansas City, MO.
⁸ East Tennessee Heart Consultants, Lenoir City, TN.
⁹ University of Michigan Health System and Red Forest Consulting, Ann Arbor, MI.
¹⁰ Chapel Hill, NC.
¹¹ Department of Electrical and Computer Engineering, Purdue University, West Lafayette, IN.
¹² MR Systems Engineering, GE Healthcare, Milwaukee, WI.
¹³ Yale University School of Medicine, New Haven, CT.
¹⁴ U.S. Food and Drug Administration, Rockville, MD.
¹⁵ American College of Radiology, 1891 Preston White Dr., Reston, VA 20191.

Received December 8, 2006; accepted after revision December 18, 2006.

 
E. Kanal is a consultant for, is a member of the speakers bureau of, and provides research support for Bracco Diagnostics and GE Healthcare; is a member of the speakers bureau of and provides research support for Siemens Medical Solutions; and provides research support for Berlex and Medtronic.

T. Gilk is a consultant for Mednovus, Inc.

J. R. Gimbel provides research support for St. Jude Medical, Medtronic, and Biotronik.

J. Nyenhuis is a consultant for and provides research support to Medtronic.

J. Weinreb is a consultant and member of the speakers bureau for GE Healthcare.

Address correspondence to N. Sass.

FOR YOUR INFORMATION

See the accompanying CME/SAM article in this month's issue of AJR Integrative Imaging included with your AJR.

FOR YOUR INFORMATION

The reader's attention is directed to the commentary on this article, which appears on page 1446.

Keywords: MR contrast agents • MRI • safety

Introduction

Top Introduction ACR Guidance Document for... APPENDIX 1: Personnel and... APPENDIX 2: MR Facility... APPENDIX 3: Safety Screening... APPENDIX 4: MR Facility... References Additional Sources

 
There are potential risks in the MR environment, not only for the patient [1, 2] but also for the accompanying family members, attending health care professionals, and others who find themselves only occasionally or rarely in the magnetic fields of MR scanners, such as security or housekeeping personnel, firefighters, police, etc. [3–6]. There have been reports in the medical literature and print media detailing magnetic resonance imaging (MRI) adverse incidents involving patients, equipment, and personnel that spotlighted the need for a safety review by an expert panel. To this end, the American College of Radiology (ACR) originally formed the Blue Ribbon Panel on MR Safety. First constituted in 2001, the panel was charged with reviewing existing MR safe practices and guidelines [5–9] and issuing new ones as appropriate for MR examinations. Published initially in 2002 [3], the ACR MR Safe Practice Guidelines established de facto industry standards for safe and responsible practices in clinical and research MR environments. These were subsequently reviewed and updated in May 2004 [4]. After reviewing substantial feedback from the field and installed bases, as well as changes that had transpired throughout the MR industry since the publication of the 2004 version of this document, the panel extensively reviewed, modified, and updated the entire document in 2006–2007.

The present panel consists of the following members: A. James Barkovich, MD; Charlotte Bell, MD (American Society of Anesthesiologists); James P. Borgstede, MD, FACR; William G. Bradley, MD, PhD, FACR; Jerry W. Froelich, MD; Tobias Gilk, architect; J. Rod Gimbel, MD, FACC, cardiologist; John Gosbee, MD, MS; Ellisa Kuhni-Kaminski, RT (R)(MR); Emanuel Kanal, MD, FACR, FISMRM (chair); James W. Lester, MD; John Nyenhuis, PhD; Yoav Parag, MD; Daniel Joe Schaefer, PhD, engineer; Elizabeth A. Sebek-Scoumis, RN, BSN, CRN; Jeffrey Weinreb, MD; Loren A. Zaremba, PhD, FDA; Pamela Wilcox, RN, MBA (ACR staff); Leonard Lucey, JD, LLM (ACR staff); and Nancy Sass, RT (R)(MR)(CT) (ACR staff). The following represents the most recently modified and updated version of the combined prior two reports [3, 4] issued by the American College of Radiology Blue Ribbon Panel on MR Safety, chaired by Emanuel Kanal, MD, FACR. It is important to note that nothing that appears herein is the result of a "majority vote" of the members of this panel. As with each prior publication of these ACR MR Safe Practice Guidelines, the entire document, from introduction to the markedly expanded appendices, represents the unanimous consensus of each and every member of this Safety Committee and the various areas of expertise that they represent. This includes representation from fields and backgrounds as diverse as MR physicists, research/academic radiologists, private practice radiologists, MR safety experts, patient safety experts/researchers, MR technologists, MR nursing, National Electrical Manufacturers Association, the U.S. Food and Drug Administration (FDA), the American Society of Anesthesiologists, legal counsel, and others. Lay personnel, physicians, PhDs, department chairs and house-staff/residents, government employees and private practitioners, doctors, nurses, technologists, radiologists, anesthesiologists, cardiologists, attorneys—these are all represented on this Committee. It was felt that achieving unanimity for these guidelines was critical in order to demonstrate to all that these guidelines are not only appropriate from a scientific point of view, but are reasonably applicable in the real world in which we all must live, with all its patient care, financial, and throughput pressures and considerations.

The following MR safe practice guidelines document is intended to be used as a template for MR facilities to follow in the development of an MR safety program. These guidelines were developed to help guide MR practitioners regarding these issues and to provide a basis for them to develop and implement their own MR policies and practices. It is intended that these MR safe practice guidelines (and the policies and procedures to which they give rise) be reviewed and updated on a regular basis as the field of MR safety continues to evolve.

The principles behind these MR safe practice guidelines are specifically intended to apply not only to diagnostic settings but also to patient, research subject, and health care personnel safety for all MRI settings, including those designed for clinical diagnostic imaging, research, interventional, and intraoperative MR applications.

With the increasing advent and use of 3.0-Tesla and higher strength magnets, users need to recognize that one should never assume MR compatibility or safety information about a device if it is not clearly documented in writing. Decisions based on published MR safety and compatibility claims should recognize that all such claims apply only to specifically tested conditions, such as static magnetic field strengths, static gradient magnetic field strengths and spatial distributions, and the strengths and rates of change of gradient and radiofrequency (RF) magnetic fields.

Finally, there are many issues that impact MR safety that should be considered during site planning for a given MR installation. These have historically not been dealt with in the prior versions of the ACR MR Safe Practice Guidelines. For the first time, we include in this article, as separate appendices, sections that address such issues as well, including cryogen emergency vent locations and pathways, 5-gauss lines, siting considerations, patient access pathways, etc. Yet despite their appearance herein, these issues, and many others, should be reviewed with those experienced in MR site planning and familiar with the patient safety and patient flow considerations prior to committing to construction of a specific site design. In this regard, enlisting the assistance of an architectural firm experienced in this area, and doing so early in the design stages of the planning process, may prove most valuable.

It remains the intent of the ACR that these MR Safe Practice Guidelines will prove helpful as the field of MRI continues to evolve and mature, providing MR services that are among the most powerful, yet safest, of all diagnostic procedures to be developed in the history of modern medicine.

ACR Guidance Document for Safe MR Practices: 2007

Top Introduction ACR Guidance Document for... APPENDIX 1: Personnel and... APPENDIX 2: MR Facility... APPENDIX 3: Safety Screening... APPENDIX 4: MR Facility... References Additional Sources

 
A. Establish, Implement, and Maintain Current MR Safety Policies and Procedures

1. All clinical and research MR sites, irrespective of magnet format or field strength, including installations for diagnostic, research, interventional, and/or surgical applications, should maintain MR safety policies.
   
2. These policies and procedures should also be reviewed concurrently with the introduction of any significant changes in safety parameters of the MR environment of the site (e.g., adding faster or stronger gradient capabilities or higher RF duty cycle studies) and updated as needed. In this review process, national and international standards and recommendations should be taken into consideration prior to establishing local guidelines, policies, and procedures.
   
3. Each site will name an MR medical director whose responsibilities will include ensuring that MR safe practice guidelines are established and maintained as current and appropriate for the site. It is the responsibility of the site's administration to ensure that the policies and procedures that result from these MR safe practice guidelines are implemented and adhered to at all times by all of the site's personnel.
   
4. Procedures should be in place to ensure that any and all adverse events, MR safety incidents, or "near incidents" that occur in the MR site are reported to the medical director in a timely fashion (e.g., within 24 hours or 1 business day of their occurrence) and used in continuous quality improvement efforts. It should be stressed that the Food and Drug Administration states that it is incumbent upon the sites to also report adverse events and incidents to them via their MedWatch program. The ACR supports this requirement and feels that it is in the ultimate best interest of all MR practitioners to create and maintain this consolidated database of such events to help us all learn about them and how to better avoid them in the future [10, 11].
   

B. Static Magnetic Field Issues: Site Access Restriction
1. Zoning
The MR site is conceptually divided into four Zones (see Figure 1 and Appendix 1):

View larger version (20K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1 —Idealized sample floor plan illustrates site access restriction considerations. Other MR potential safety issues, such as magnet site planning related to fringe magnetic field considerations, are not meant to be include herein. See Appendix 1 for personnel and zone definitions. Note—In any zone of the facility, there should be compliance with Health Insurance Portability and Accountability Act (HIPAA) regulations in regard to privacy of patient information. However, in Zone III, there should be a privacy barrier so that unauthorized persons cannot view control panels.

1. Zone I: This region includes all areas that are freely accessible to the general public. This area is typically outside the MR environment itself and is the area through which patients, health care personnel, and other employees of the MR site access the MR environment.
   
2. Zone II: This area is the interface between the publicly accessible, uncontrolled Zone I and the strictly controlled Zones III and IV. Typically, patients are greeted in Zone II and are not free to move throughout Zone II at will, but are rather under the supervision of MR personnel (see section B.2.b, below). It is in Zone II that the answers to MR screening questions, patient histories, medical insurance questions, etc. are typically obtained.
   
3. Zone III: This area is the region in which free access by unscreened non-MR personnel or ferromagnetic objects or equipment can result in serious injury or death as a result of interactions between the individuals or equipment and the MR scanner's particular environment. These interactions include, but are not limited to, those involving the MR scanner's static and time-varying magnetic fields. All access to Zone III is to be strictly restricted, with access to regions within it (including Zone IV, see below) controlled by, and entirely under the supervision of, MR personnel (see section B.2.b, below). Specifically identified MR personnel (typically, but not necessarily only, the MR technologists) are to be charged with ensuring that this MR safe practice guideline is strictly adhered to for the safety of the patients and other non-MR personnel, the health care personnel, and the equipment itself. This function of the MR personnel is directly under the authority and responsibility of the MR medical director or the level 2 MR personnel–designated (see section B.2.b, below) physician of the day for the MR site.
   Zone III regions should be physically restricted from general public access by, for example, key locks, passkey locking systems, or any other reliable, physically restricting method that can differentiate between MR personnel and non-MR personnel. The use of combination locks is discouraged as combinations often become more widely distributed than initially intended, resulting in site restriction violations being more likely with these devices. Only MR personnel shall be provided free access, such as the access keys or passkeys, to Zone III.
   There should be no exceptions to this guideline. Specifically, this includes hospital or site administration, physician, security, and other non-MR personnel (see section B.2.c, below). Non-MR personnel are not to be provided with independent Zone III access until such time as they undergo the proper education and training to become MR personnel themselves. Zone III, or at the very least the area within it wherein the static magnetic field's strength exceeds 5 gauss, should be demarcated and clearly marked as being potentially hazardous.
   Because magnetic fields are three-dimensional volumes, Zone III controlled access areas may project through floors and ceilings of MRI suites, imposing magnetic field hazards on persons on floors other than that of the MR scanner. Zones of magnetic field hazard should be clearly delineated, even in typically nonoccupied areas such as rooftops or storage rooms, and access to these Zone III areas should be similarly restricted from non-MR personnel as they would be inside any other Zone III region associated with the MRI suite. For this reason, magnetic field strength plots for all MRI systems should be analyzed in vertical section as well as in horizontal plan, identifying areas above or below, in addition to areas on the same level, where persons may be at risk of interactions with the magnetic field.
   
4. Zone IV: This area is synonymous with the MR scanner magnet room itself, that is, the physical confines of the room within which the MR scanner is located. Zone IV, by definition, will always be located within Zone III, as it is the MR magnet and its associated magnetic field that generates the existence of Zone III. Zone IV should also be demarcated and clearly marked as being potentially hazardous due to the presence of very strong magnetic fields. As part of the Zone IV site restriction, all MR installations should provide for direct visual observation by level 2 personnel to access pathways into Zone IV. By means of illustration only, the MR technologists would be able to directly observe and control, via line of sight or via video monitors, the entrances or access corridors to Zone IV from their normal positions when stationed at their desks in the scan control room.
   Zone IV should be clearly marked with a red light and lighted sign stating, "The Magnet is On." Except for resistive systems, this light and sign should be illuminated at all times and should be provided with a backup energy source to continue to remain illuminated for at least 24 hours in the event of a loss of power to the site.
   In case of cardiac or respiratory arrest or other medical emergency within Zone IV for which emergent medical intervention or resuscitation is required, appropriately trained and certified MR personnel should immediately initiate basic life support or CPR as required by the situation while the patient is being emergently removed from Zone IV to a predetermined, magnetically safe location. All priorities should be focused on stabilizing (e.g., basic life support with cardiac compressions and manual ventilation) and then evacuating the patient as rapidly and safely as possible from the magnetic environment that might restrict safe resuscitative efforts.
   Further, for logistical safety reasons, the patient should always be moved from Zone IV to the prospectively identified location where full resuscitative efforts are to continue. (See Appendix 2.)
   Quenching the magnet (for superconducting systems only) is not routinely advised for cardiac or respiratory arrest or other medical emergency, since quenching the magnet and having the magnetic field dissipate could easily take more than a minute. Furthermore, as quenching a magnet can theoretically be hazardous, ideally one should evacuate the magnet room, when possible, for an intentional quench. One should rather use that time wisely to initiate life support measures while removing the patient from Zone IV to a location where the strength of the magnetic field is insufficient to be a medical concern. Zones III and IV site access restriction must be maintained during resuscitation and other emergent situations for the protection of all involved.
   

2. MR personnel and non-MR personnel

1. All individuals working within at least Zone III of the MR environment should be documented as having successfully completed at least one of the MR safety live lectures or prerecorded presentations approved by the MR medical director. Attendance should be repeated at least annually, and appropriate documentation should be provided to confirm these ongoing educational efforts. These individuals shall be referred to henceforth as MR personnel.
   
2. There are two levels of MR personnel:
   
   1. Level 1 MR personnel: Those who have passed minimal safety educational efforts to ensure their own safety as they work within Zone III will be referred to henceforth as level 1 MR personnel.
      
   2. Level 2 MR personnel: Those who have been more extensively trained and educated in the broader aspects of MR safety issues, including, for example, issues related to the potential for thermal loading or burns and direct neuromuscular excitation from rapidly changing gradients, will be referred to henceforth as level 2 MR personnel. It is the responsibility of the MR medical director not only to identify the necessary training, but also to identify those individuals who qualify as level 2 MR personnel. It is understood that the medical director will have the necessary education and experience in MR safety to qualify as level 2 MR personnel. (See Appendix 1.)
      
   
   
3. All those not having successfully complied with this MR safety instruction guideline shall be referred to henceforth as non-MR personnel. Specifically, non-MR personnel will be the terminology used to refer to any individual or group who has not within the previous 12 months undergone the designated formal training in MR safety issues defined by the MR safety director of that installation.
   

3. Patient and non-MR personnel screening

1. All non-MR personnel wishing to enter Zone III must first pass an MR safety screening process. Only MR personnel are authorized to perform an MR safety screen before permitting non-MR personnel into Zone III.
   
2. The screening process and screening forms for patients, non-MR personnel, and MR personnel should be essentially identical. Specifically, one should assume that non-MR personnel, health care practitioners, or MR personnel may enter the bore of the MR imager during the MR imaging process.
   Examples of this might include when a pediatric patient cries for his mother, who then leans into the bore, or when the anesthetist leans into the bore to manually ventilate a patient in the event of a problem.
   
3. Metal detectors
   The usage in MR environments of conventional metal detectors which do not differentiate between ferrous and nonferromagnetic materials is not recommended. Reasons for this recommendation against conventional metal detector usage include, among others:
   
   1. They have varied—and variable—sensitivity settings.
      
   2. The skills of the operators can vary.
      
   3. Today's conventional metal detectors cannot detect, for example, a 2 x 3 mm, potentially dangerous ferromagnetic metal fragment in the orbit or near the spinal cord or heart.
      
   4. Today's conventional metal detectors do not differentiate between ferromagnetic and nonferromagnetic metallic objects, implants, or foreign bodies.
      
   5. Metal detectors should not be necessary for the detection of large metallic objects, such as oxygen tanks on the gurney with the patients. These objects are fully expected to be detected—and physically excluded—during the routine patient screening process.
      However, ferromagnetic detection systems are currently available that are simple to operate, capable of detecting even very small ferromagnetic objects external to the patient, and now, for the first time, differentiating between ferromagnetic and nonferromagnetic materials. While the use of conventional metal detectors is not recommended, the use of ferromagnetic detection systems is recommended as an adjunct to thorough and conscientious screening of persons and devices approaching Zone IV. It should be reiterated that their use is in no way meant to replace a thorough screening practice, which rather should be supplemented by their usage.
      
   
   
4. Non-MR personnel should be accompanied by, or under the immediate supervision of and in visual or verbal contact with, one specifically identified level 2 MR person for the entirety of their duration within Zone III or Zone IV restricted regions. However, it is acceptable to have non-MR personnel in a changing room or restroom in Zone III without visual contact as long as the personnel and the patient can communicate verbally with each other.
   Level 1 MR personnel are permitted unaccompanied access throughout Zones III and IV. Level 1 MR personnel are also explicitly permitted to be responsible for accompanying non-MR personnel into and throughout Zone III, excluding Zone IV. However, level 1 MR personnel are not permitted to directly admit, or be designated responsible for, non-MR personnel in Zone IV.
   In the event of a shift change, lunch break, etc., no level 2 MR personnel shall relinquish their responsibility to supervise non-MR personnel still within Zone III or Zone IV until such supervision has been formally transferred to another of the site's level 2 MR personnel.
   
5. Nonemergent patients should be MR safety–screened on site by a minimum of 2 separate individuals. At least one of these individuals should be level 2 MR personnel. At least one of these 2 screenings should be performed verbally or interactively.
   Emergent patients and their accompanying non-MR personnel may be screened only once, providing the screening individual is level 2 MR personnel. There should be no exceptions to this.
   
6. Any individual undergoing an MR procedure must remove all readily removable metallic personal belongings and devices on or in them (e.g., watches, jewelry, pagers, cell phones, body piercings [if removable], contraceptive diaphragms, metallic drug delivery patches [see section I, below], cosmetics containing metallic particles [such as eye make-up], and clothing items that may contain metallic fasteners, hooks, zippers, loose metallic components, or metallic threads). It is therefore advisable to require that the patients or research subjects wear a site-supplied gown with no metal fasteners when feasible.
   
7. All patients and non-MR personnel with a history of potential ferromagnetic foreign object penetration must undergo further investigation prior to being permitted entrance to Zone III. Examples of acceptable methods of screening include patient history, plain X-ray films, prior CT or MR studies of the questioned anatomic area, or access to written documentation as to the type of implant or foreign object that might be present. Once positive identification has been made as to the type of implant or foreign object that is within a patient, best-effort assessments should be made to identify the MR compatibility or MR safety of the implant or object. Efforts at identification might include written records of the results of formal testing of the implant prior to implantation (preferred), product labeling regarding the implant or object, and review of peer-reviewed publications regarding MR compatibility and MR safety testing of the make, model, and type of the object. MR safety testing would be of value only if the object or device had not been altered since such testing results had been published.
   All patients who have a history of orbit trauma by a potential ferromagnetic foreign body for which they sought medical attention are to have their orbits cleared either by plain X-ray orbit films (2 views) [12, 13] or by a radiologist's review and assessment of contiguous cut prior CT or MR images (obtained since the suspected traumatic event), if available.
   
8. Conscious, nonemergent patients and research and volunteer subjects are to complete written MR safety screening questionnaires prior to their introduction to Zone III. Family or guardians of nonresponsive patients or of patients who cannot reliably provide their own medical histories are to complete a written MR safety screening questionnaire prior to their introduction to Zone III. These completed questionnaires are then to be reviewed orally with the patient, guardian, or research subject in their entirety prior to permitting the patient or research subject to be cleared into Zone III.
   The patient, guardian, or research subject as well as the screening MR staff member must both sign the completed form. This form should then become part of the patient's medical record. No empty responses will be accepted—each question must be answered with a "yes" or "no" or specific further information must be provided as requested. A sample pre-MR screening form is provided (see Appendix 3). This is the minimum information to be obtained; more may be added if the site so desires.
   
9. Screening of the patient or non-MR personnel with, or suspected of having, an intracranial aneurysm clip should be performed as per the separate MR safe practice guideline addressing this particular topic (see section M, below).
   
10. Screening of patients for whom an MR examination is deemed clinically indicated or necessary, but who are unconscious or unresponsive, who cannot provide their own reliable histories regarding prior possible exposures to surgery, trauma, or metallic foreign objects, and for whom such histories cannot be reliably obtained from others:
    
    1. If no reliable patient metal exposure history can be obtained, and if the requested MR examination cannot reasonably wait until a reliable history might be obtained, it is recommended that such patients be physically examined by level 2 MR personnel. All areas of scars or deformities that might be anatomically indicative of an implant, such as on the chest or spine region, and whose origins are unknown and which may have been caused by ferromagnetic foreign bodies, implants, etc., should be subject to plain-film radiography (if recently obtained plain films or CT or MR studies of such areas are not already available). The investigation described above should be made to ensure there are no potentially harmful embedded or implanted metallic foreign objects or devices. All such patients should also undergo plain film imaging of the skull or orbits and chest to exclude metallic foreign objects (if recently obtained plain films or CT or MR studies of such areas are not already available).
       
    2. Monitoring of patients in the MR scanner is sometimes necessary. The potential for thermal injury from excessive RF power deposition exists. Sedated, anesthetized, or unconscious patients may not be able to express symptoms of such injury. This potential for injury is greater on especially higher-field whole-body scanners (e.g., 1 Tesla and above). Distortion of the electrocardiogram within the magnetic field makes interpretation of the ECG complex unreliable, even with filtering used by contemporary monitoring systems. However, routine monitoring of heart rate and rhythm may be accomplished using pulse oximetry, which also eliminates the risks of thermal injury from electrocardiography. Patients who require ECG monitoring and who are unconscious, sedated, or anesthetized should be examined after each imaging sequence, with potential repositioning of the ECG leads and any other electrically conductive material with which the patient is in contact. Alternatively, cold compresses or ice packs could be placed upon all necessary electrically conductive material that touches the patient during scanning.
       
    
    
11. Final determination of whether or not to scan any given patient with any given implant, foreign body, etc., is to be made by the level 2 MR personnel–designated attending MR radiologist, the MR medical director, or specifically designated level 2 MR personnel following criteria for acceptability predetermined by the medical director.
    For implants that are strongly ferromagnetic, an obvious concern is that of magnetic translational and rotational forces upon the implant which might move or dislodge the device from its implanted position. If an implant has demonstrated weak ferromagnetic forces on formal testing, it might be prudent to wait several weeks for fibrous scarring to set in, as this may help anchor the implant in position and help it resist such weakly attractive magnetic forces that might arise in MR environments.
    For all implants that have been demonstrated to be nonferrous in nature, however, the risk of implant motion is essentially reduced to those resulting from Lenz's forces alone. These tend to be quite trivial for typical metallic implant sizes of a few centimeters or less. Thus, a waiting period for fibrous scarring to set in is far less important, and the advisability for such a waiting period may well be easily outweighed by the potential clinical benefits of undergoing an MR examination at that time. As always, clinical assessment of the risk–benefit ratio for the particular clinical situation and patient at hand are paramount for appropriate medical decision making in these scenarios.
    It is possible that during the course of an MRI examination an unanticipated ferromagnetic implant or foreign body is discovered within a patient or research subject undergoing the examination. This is typically suspected or detected by means of a sizable field-distorting artifact seen on spin-echo imaging techniques that grows more obvious on longer TE studies and expands markedly on typical moderate or long TE gradient-echo imaging sequences. In such cases, it is imperative that the medical director, safety officer, and/or physician in charge be immediately notified of the suspected findings. This individual should then assess the situation, review the imaging information obtained, and decide what the best course of action might be.
    It should be noted that there are numerous potentially acceptable courses that might be recommended which in turn depend upon many factors, including the status of the patient, the location of the suspected ferromagnetic implant/foreign body relative to local anatomic structures, the mass of the implant, etc. Appropriate courses of action might include proceeding with the scan under way, immobilizing the patient and the immediate removal of the patient from the scanner, or other intermediate steps. Regardless of the course of action selected, it is important to note that the forces on the implant will change, and may actually increase, during the attempt to remove the patient from the scanner bore. Further, the greater the rate of motion of the patient/device through the magnetic fields of the scanner bore, the greater the forces acting upon that device will likely be. Thus, it is prudent to ensure that, if at all possible, immobilization of the device during patient extraction from the bore, and the slow, cautious, deliberate rate of extricating the patient from the bore, will likely result in weaker and potentially less harmful forces on the device as it traverses the various static magnetic field gradients associated with the MR imager.
    It is also worthy of note that the magnetic fields associated with the MR scanner are distributed throughout space three-dimensionally. Thus, especially for superconducting systems, one should avoid the temptation to have the patient sit up as soon as he or she is physically out of the bore. Doing so may expose the ferrous object to still-significant torque- and translation-related forces despite the patient's being physically outside the scanner bore. It is therefore advisable to continue to extract the patient along a straight line course parallel to the center of the magnet while the patient remains immobilized until they are as far as physically possible from the MR imager itself, before any other patient/object motion vector is attempted or permitted.
    
12. All non-MR personnel (e.g., patients, volunteers, varied site employees, and professionals) with implanted cardiac pacemakers, autodefibrillators, diaphragmatic pacemakers, or other electromechanically activated devices upon which the non-MR personnel is dependent should be precluded from Zone IV and physically restrained from the 5-gauss line unless specifically cleared in writing by a level 2 MR personnel–designated attending radiologist or the medical director of the MR site. In such circumstances, a specific defending risk–benefit rationale should be provided in writing and signed by the authorizing radiologist.
    Should it be determined that non-MR personnel wishing to accompany a patient into an MR scan room require their orbits to be cleared by plain-film radiography, a radiologist must first discuss with the non-MR personnel that plain X-ray films of their orbits are required prior to permitting them access to the MR scan room. Should they still wish to proceed with access to Zone IV or within the 5-gauss line, and should the attending radiologist deem it medically advisable that they do so (e.g., for the care of their child about to undergo an MR study), written informed consent should be provided by these accompanying non-MR personnel prior to their undergoing X-ray examination of their orbits.
    
13. MR scanning of patients, prisoners, or parolees with metallic prisoner-restraining devices or RF ID or tracking bracelets could lead to theoretic adverse events, including: (1) ferromagnetic attractive effects and resultant patient injury, (2) possible ferromagnetic attractive effects and potential damage to the device or its battery pack, (3) RF interference with the MRI study and secondary image artifact, (4) RF interference with the functionality of the device, (5) RF power deposition and heating of the bracelet or tagging device or its circuitry and secondary patient injury (if the bracelet were in the anatomic volume of the RF transmitter coil being used for imaging). Therefore, when requested to scan a patient, prisoner, or parolee wearing RF bracelets or metallic handcuffs or ankle cuffs, request that the patient be accompanied by the appropriate authorities who can and will remove the restraining device prior to the MR study and be charged with its replacement following the examination.
    
14. Firefighter, police, and security safety considerations: For the safety of firefighters and other emergent services responding to an emergent call at the MR site, it is recommended that all fire alarms, cardiac arrests, or other emergent service response calls originating from or located in the MR site should be forwarded simultaneously to a specifically designated individual from among the site's MR personnel. This individual should, if possible, be on site prior to the arrival of the firefighters or emergent responders to ensure that they do not have free access to Zone III or Zone IV. The site might consider assigning appropriately trained security personnel, who have been trained and designated as MR personnel, to respond to such calls.
    In any case, all MR sites should arrange to prospectively educate their local fire marshals, firefighters' associations, and police or security personnel about the potential hazards of responding to emergencies in the MR suite.
    It should be stressed that even in the presence of a true fire (or other emergency) in Zone III or Zone IV, the magnetic fields may be present and fully operational. Therefore, free access to Zone III or Zone IV by firefighters or other non-MR personnel with air tanks, axes, crowbars, other firefighting equipment, guns, etc., might prove catastrophic or even lethal to those responding or to others in the vicinity.
    As part of the Zone III and Zone IV restrictions, all MR sites must have clearly marked, readily accessible MR-conditional or MR-safe fire extinguishing equipment physically stored in Zone III or Zone IV. All conventional fire extinguishers and other firefighting equipment not tested and verified safe in the MR environment should be restricted from Zone III.
    For superconducting magnets, the helium (and the nitrogen as well, in older MR magnets) is not flammable and does not pose a fire hazard directly. However, the liquid oxygen that can result from the supercooled air in the vicinity of the released gases might well increase the fire hazard in this area. If there are appropriately trained and knowledgeable MR personnel available during an emergency to ensure that emergency response personnel are kept out of the MR scanner or magnet room and away from the 5-gauss line, quenching the magnet during a response to an emergency or fire should not be a requirement.
    However, if the fire is in such a location where Zone III or Zone IV needs to be entered for whatever reason by firefighting or emergency response personnel and their firefighting and emergent equipment, such as air tanks, crowbars, axes, and defibrillators, a decision to quench a superconducting magnet should be very seriously considered to protect the health and lives of the emergent responding personnel. Should a quench be performed, appropriately designated MR personnel still need to ensure that all non-MR personnel (including and especially emergent response personnel) continue to be restricted from Zones III and IV until the designated MR personnel has personally verified that the static field is either no longer detectable or at least sufficiently attenuated as to no longer present a potential hazard to one moving by it with, for example, large ferromagnetic objects such as air tanks or axes.
    For resistive systems, the magnetic field of the MR scanner should be shut down as completely as possible and verified as such prior to permitting the emergency response personnel access to Zone IV. For permanent, resistive, or hybrid systems whose magnetic fields cannot be completely shut down, MR personnel should ideally be available to warn the emergency response personnel that a very powerful magnetic field is still operational in the magnet room.
    

4. MR personnel screening
All MR personnel are to undergo an MR screening process as part of their employment interview process to ensure their safety in the MR environment. For their own protection and for the protection of the non-MR personnel under their supervision, all MR personnel must immediately report to the MR medical director any trauma, procedure, or surgery they experience or undergo in which a ferromagnetic metallic object or device may have become introduced within or on them. This will permit appropriate screening to be performed on the employee to determine the safety of permitting that employee into Zone III.

5. Device and object screening
Ferrous objects, including those brought by patients, visitors, contractors, etc., should be restricted from entering Zone III, whenever practical.

As part of the Zone III site restriction and equipment testing and clearing responsibilities, all sites should have ready access to a strong handheld magnet ( 1000 gauss). This will enable the site to test external, and even some superficial internal, devices or implants for the presence of grossly detectable ferromagnetic attractive forces.

1. All portable metallic or partially metallic devices that are on or external to the patient (e.g., oxygen cylinders) are to be positively identified in writing as ferromagnetic or, alternatively, nonferromagnetic and safe or conditionally safe in the MR environment prior to permitting them into Zone III. For all device or object screening, verification and positive identification should be in writing. Examples of devices that need to be positively identified include fire extinguishers, oxygen tanks, and aneurysm clips.
   
2. External devices or objects demonstrated to be ferromagnetic and MR unsafe or incompatible in the MR environment may still, under specific circumstances, be brought into Zone III if, for example, they are deemed by MR personnel to be necessary and appropriate for patient care. They should only be brought into Zone III if they are under the direct supervision of specifically designated level 1 or level 2 MR personnel who are thoroughly familiar with the device, its function, and the reason supporting its introduction to Zone III. The safe utilization of these devices while they are present in Zone III will be the responsibility of specifically named level 1 or 2 MR personnel. These devices must be appropriately physically secured or restricted at all times during which they are in Zone III to ensure that they do not inadvertently come too close to the MR scanner and accidentally become exposed to static magnetic fields or gradients that might result in their becoming either hazardous projectiles or no longer accurately functional.
   
3. Never assume MR compatibility or safety information about the device if it is not clearly documented in writing. All unknown external objects or devices being considered for introduction beyond Zone II should be tested with a strong handheld magnet ( 1000 gauss) for ferromagnetic properties before permitting them entry to Zone III. The results of such testing, as well as the date, time, and name of the tester, and methodology used for that particular device, should be documented in writing. If a device has not been tested, or if its MR compatibility or safety status is unknown, it should not be permitted unrestricted access to Zone III.
   
4. All portable metallic or partially metallic objects that are to be brought into Zone IV must be properly identified and appropriately labeled utilizing the current FDA labeling criteria developed by ASTM (American Society for Testing and Materials) International (http://www.astm.org) (see Fig. 2). Those items which are wholly nonmetallic should be identified with a square green "MR safe" label. Items which are clearly ferromagnetic should be identified as "not MR safe" and labeled appropriately with the corresponding round red label with a slash through it. Objects with an "MR conditional" rating should be affixed with a triangular yellow MR conditional label prior to being taken into the scan room/Zone IV.
   As noted in the introduction to this section B.5, above, if MR safety data are not prospectively available for a given device, initial testing for the purpose of this labeling is to be accomplished by the site's MR personnel by exposing the metallic object to a handheld magnet ( 1000 gauss). If grossly detectable attractive forces are observed between the object being tested or any of its components and the handheld magnet, it is to be labeled with a circular red "not MR safe" label. If no or negligible attractive forces are observed, a triangular yellow "MR conditional" label is to be attached to the object. It is only when the composition of an object and its components are known to be nonmetallic that the green "MR safe" label is to be affixed to a device or object.
   Particularly with regard to nonclinical and incidental equipment, current products marketed with ill-defined terminology such as "non-magnetic," or outdated classifications such as "MR-compatible," should not be presumed to conform to a particular current ASTM classification. Similarly, any product marketed as "MR safe" but with metallic construction or components should be treated with suspicion. Objects intended for use in Zone IV, including nonclinical incidental products such as stepping stools or ladders, which are not provided with manufacturer or third-party MR safety test results under the new ASTM criteria, should be site tested as described above.
   
5. Decisions based on published MR compatibility or safety claims should recognize that all such claims apply to specifically tested static field and static gradient field strengths—for example, "MR conditional, having been tested to be safe up to 3.0 Tesla at gradient strengths of 400 G/cm," or "MR conditional, having been tested to be safe up to 1.5 Tesla up to maximum static gradient fields experienced in an unshielded 1.5-Tesla [manufacturer's name] wholebody MR scanner tested 1.5 feet (roughly 45 cm) within the bore."
   
6. It should be noted that alterations performed by the site on MR safe, MR unsafe, and MR conditional equipment or devices may alter the MR safety or compatibility properties of the device. For example, tying a ferromagnetic metallic twisting binder onto a sign labeling the device as MR conditional or MR safe might result in artifact induction—or worse—if introduced into the MR scanner.
   Lenz's Forces:
   Faraday's law states that a moving or changing magnetic field will induce a voltage in a perpendicularly oriented electrical conductor. Lenz's law builds upon this and states that the induced voltage will itself be such that it will secondarily generate its own magnetic field whose orientation and magnitude will oppose those of the initial time-varying magnetic field that created it in the first place. For example, if an electrical conductor is moved perpendicularly toward the magnetic field, B₀, of an MR scanner, even if this conductor is not grossly ferromagnetic, the motion itself will result in the generation of voltages in this conductor whose magnitude is directly proportional to the rate of motion as well as the spatial gradient of the magnetic field, B₀, through which it is being moved. Conducting objects turning in the static field will also experience a torque due to the induced eddy currents. Lenz's law states that this induced current will in turn create a magnetic field whose orientation will oppose the B₀ magnetic field that created this current.
   Thus, moving a large metallic but nonferromagnetic electrical conductor toward the magnet bore will result in the induction of a voltage and associated magnetic field which will orient in such a manner and at such a strength as to oppose the motion of the metallic object into the bore of the MR scanner. If, for example, one tries to move a nonferrous oxygen tank into the bore of an MR scanner, as the scanner bore is approached Lenz's forces will be sufficiently strong to virtually stop forward progress of the tank. Further, the faster one moves the tank into the bore, the greater the opposing force that is created to stop this motion.
   This also has potential consequences for large implanted metallic devices such as certain metallic nonferrous infusion pumps. Although they may not pose a projectile hazard, rapid motion of the patient/implant perpendicular to the magnetic field of the MR imager can be expected to result in forces on the implant that would oppose this motion and may likely be detected by the patient. If the patient were to complain of experiencing forces tugging or pulling on the implant, this might bring the patient or health care personnel to erroneously conclude that there were ferrous components to the device, which might lead to cancellation of the examination. Slowly moving such large metallic devices into and out of the bore is a key factor in decreasing any Lenz's forces that might be induced and in decreasing the likelihood of a misunderstanding or an unnecessary study cancellation.
   

View larger version (16K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2 —U.S. Food and Drug Administration labeling criteria (developed by ASTM [American Society for Testing and Materials] International) for portable objects taken into Zone IV. Square green "MR safe" label is for wholly nonmetallic objects, triangular yellow label is for objects with "MR conditional" rating, and round red label is for "not MR safe" objects.

C. MR Technologists

1. MR technologists should be ARRT (American Registry of Radiologic Technologists)–registered technologists (RTs). Furthermore, all MR technologists must be trained as level 2 MR personnel during their orientation prior to being permitted free access to Zone III.
   
2. All MR technologists will maintain current certification in American Heart Association basic life support at the health care provider level.
   
3. Except for emergent coverage, there will be a minimum of 2 MR technologists or one MR technologist and one other individual with the designation of MR personnel in the immediate Zone II through Zone IV MR environment. For emergent coverage, the MR technologist can scan with no other individuals in their Zone II through Zone IV environment as long as there is in-house, ready emergent coverage by designated department of radiology MR personnel (e.g., radiology house staff or attending radiologist).
   

D. Pregnancy-Related Issues
1. Health care practitioner pregnancies
Pregnant health care practitioners are permitted to work in and around the MR environment throughout all stages of their pregnancy [14]. Acceptable activities include, but are not limited to, positioning patients, scanning, archiving, injecting contrast material, and entering the MR scan room in response to an emergency. Although permitted to work in and around the MR environment, pregnant health care practitioners are requested not to remain within the MR scanner bore or Zone IV during actual data acquisition or scanning.

2. Patient pregnancies
Present data have not conclusively documented any deleterious effects of MR imaging exposure on the developing fetus. Therefore, no special consideration is recommended for the first, versus any other, trimester in pregnancy. Nevertheless, as with all interventions during pregnancy, it is prudent to screen women of reproductive age for pregnancy prior to permitting them access to MR imaging environments. If pregnancy is established, consideration should be given to reassessing the potential risks versus benefits of the pending study in determining whether performance of the requested MR examination could safely wait until the end of the pregnancy.

1. Pregnant patients can be accepted to undergo MR scans at any stage of pregnancy if, in the determination of a level 2 MR personnel–designated attending radiologist, the risk–benefit ratio to the patient warrants that the study be performed. The radiologist should confer with the referring physician and document the following in the radiology report or the patient's medical record:
   
   1. The information requested from the MR study cannot be acquired via nonionizing means (e.g., ultrasonography).
      
   2. The data are needed to potentially affect the care of the patient or fetus during the pregnancy.
      
   3. The referring physician does not feel it is prudent to wait until the patient is no longer pregnant to obtain these data.
      
   
   
2. MR contrast agents should not be routinely provided to pregnant patients. This decision, too, is one that must be made on a case-by-case basis by the covering level 2 MR personnel–designated attending radiologist who will assess the risk–benefit ratio for that particular patient.
   The decision to administer a gadolinium-based MR contrast agent to pregnant patients should be accompanied by a well-documented and thoughtful risk–benefit analysis. This analysis should be able to defend a decision to administer the contrast agent based on overwhelming potential benefit to the patient or fetus outweighing the theoretic but potentially real risks of long-term exposure of the developing fetus to free gadolinium ions.
   Studies have demonstrated that gadolinium-based MR contrast agents pass through the placental barrier and enter the fetal circulation. From there, they are filtered in the fetal kidneys and then excreted into the amniotic fluid. In this location the gadolinium-chelate molecules are in a relatively protected space and may remain in this amniotic fluid for an indeterminate amount of time before finally being reabsorbed and eliminated. As with any equilibrium situation involving any dissociation constant, the longer the chelate molecule remains in this space, the greater the potential for dissociation of the potentially toxic gadolinium ion from its chelate molecule. It is unclear what impact such free gadolinium ions might have if they were to be released in any quantity in the amniotic fluid. Certainly, deposition into the developing fetus would raise concerns of possible secondary adverse effects.
   The risk to the fetus with administration of gadolinium-based MR contrast agents remains unknown and may be harmful.
   
3. It is recommended that pregnant patients undergoing an MR examination provide written informed consent documenting that they understand the potential risks and benefits of the MR procedure to be performed, are aware of the alternative diagnostic options available to them (if any), and wish to proceed.
   

E. Pediatric MR Safety Concerns
1. Sedation and monitoring issues
Children form the largest group requiring sedation for MRI, largely because of their inability to remain motionless during scans. Sedation protocols may vary from institution to institution according to the procedures performed (diagnostic vs interventional), the complexity of the patient population (healthy preschoolers vs premature infants), the method of sedation (mild sedation vs general anesthesia), and the qualifications of the sedation provider.

Adherence to standards of care mandates following the sedation guidelines developed by the American Academy of Pediatrics [15, 16], the American Society of Anesthesiologists [17], and the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) [18]. In addition, sedation providers must comply with protocols established by the individual state and the practicing institution. These guidelines require the following provisions:

1. Preprocedural medical history and examination for each patient
   
2. Fasting guidelines appropriate for age
   
3. Uniform training and credentialing for sedation providers
   
4. Intraprocedural and postprocedural monitors with adaptors appropriately sized for children (compatible with the magnetic field)
   
5. Method of patient observation (window, camera)
   
6. Resuscitation equipment, including oxygen delivery and suction
   
7. Uniform system of record keeping and charting (with continuous assessment and recording of vital signs)
   
8. Location and protocol for recovery and discharge
   
9. Quality assurance program that tracks complications and morbidity.
   

For the neonatal and the young pediatric population, special attention is needed in monitoring body temperature for both hypo- and hyperthermia in addition to other vital signs [19]. Temperature-monitoring equipment that is approved for use in the MR suite is becoming more readily available. Commercially available, MR-approved neonatal isolation transport units and other warming devices are also available for use during MR scans.

2. Pediatric screening issues
Children may not be reliable historians and, especially in cases of older children and teenagers, should be questioned both in the presence of parents or guardians and separately to maximize the possibility that all potential dangers are disclosed. Therefore, it is recommended that children be gowned before entering Zone IV to help ensure that no metallic objects, toys, etc. inadvertently find their way into Zone IV. Pillows, stuffed animals, and other comfort items brought from home represent real risks and should be discouraged from entering Zone IV. If unavoidable, each such item should be carefully checked with the powerful handheld magnet and perhaps again in the MR scanner prior to permitting the patient to enter Zone IV with the object in order to ensure that it does not contain any objectionable metallic components.

3. MR safety of accompanying family or personnel
Although any age patient might request that others accompany them for their MR examination, this is far more common in the pediatric population. Those accompanying or remaining with the patient should be screened using the same criteria as anyone else entering Zone IV.

In general, it would be prudent to limit accompanying adults to a single individual. Only a qualified, responsible MR physician should make screening criteria exceptions.

Hearing protection and MR safe/MR conditional seating are recommended for accompanying family members within the MR scan room.

F. Time-Varying Gradient Magnetic Field–Related Issues: Induced Voltages
Types of patients needing extra caution:

Patients with implanted or retained wires in anatomically or functionally sensitive areas (e.g., myocardium or epicardium, implanted electrodes in the brain) should be considered to be at higher risk, especially from faster MRI sequences, such as echo-planar imaging (which may be used in such sequences as diffusion-weighted imaging, functional imaging, perfusion-weighted imaging, MR angiographic imaging, etc.). The decision to limit the dB/dt (rate of magnetic field change) and maximum strength of the magnetic field of the gradient subsystems during imaging of such patients should be reviewed by the level 2 MR personnel–designated attending radiologist supervising the case or patient.

G. Time-Varying Gradient Magnetic Field–Related Issues: Auditory Considerations

1. All patients and volunteers should be offered and encouraged to use hearing protection prior to undergoing any imaging in the MR scanners.
   
2. All patients or volunteers in whom research sequences are to be performed (i.e., MR scan sequences that have not yet been approved by the Food and Drug Administration) are to have hearing protective devices in place prior to the initiation of any MR sequences. Without hearing protection in place, MRI sequences that are not FDA-approved should not be performed on patients or volunteers.
   

H. Time-Varying Radiofrequency Magnetic Field–Related Issues: Thermal

1. All unnecessary or unused electrically conductive materials should be removed from the MR system before the onset of imaging. It is not sufficient to merely to "unplug" or disconnect unused, unnecessary electrically conductive material and leave it within the MR scanner with the patient during imaging. All electrical connections, such as on surface coil leads or monitoring devices, must be visually checked by the scanning MR technologist prior to each use to ensure the integrity of the thermal and electrical insulation.
   
2. Electrical voltages and currents can be induced in electrically conductive materials that are within the bore of the MR imager during the MR imaging process. This might result in the heating of this material by resistive losses. This heat might be of a caliber sufficient to cause injury to human tissue. Among the variables that determine the amount of induced voltage or current is the consideration that the larger the diameter of the conductive loops, the greater the potential induced voltages or currents, and thus the greater the potential for resultant thermal injury to adjacent or contiguous patient tissue.
   Therefore, when electrically conductive material (wires, leads, implants, etc.) are required to remain within the bore of the MR scanner with the patient during imaging, care should be taken to ensure that no large-caliber electrically conducting loops (including patient tissue; see section H.5, below) are formed within the MR scanner during imaging. Furthermore, it is possible, with the appropriate configuration, lead length, static magnetic field strength, and other settings, to introduce resonant circuitry between the transmitted RF power and the lead. This could result in very rapid and clinically significant lead heating, especially at the lead tips, in a matter of seconds to a magnitude sufficient to result in tissue thermal injury or burns. This can also theoretically occur with implanted leads or wires, even when they are not connected to any other device at either end. For illustration, the FDA has noted several reports of serious injury, including coma and permanent neurologic impairment, in patients with implanted neurologic stimulators who underwent MR imaging examinations. The injuries in these instances resulted from heating of the electrode tips [20, 21].
   Further, it is entirely possible for a lead or wire to demonstrate no significant heating while undergoing MR imaging examinations at 1.5 Tesla, yet demonstrate clinically significant and potentially harmful degrees of heating within seconds at, for example, 3 Tesla. It has also been demonstrated that leads may show no significant heating at 3 Tesla yet may rapidly heat to hazardous levels when undergoing MR imaging at, for example, 1.5 Tesla (personal observation, MR safety testing, E. Kanal, MD, University of Pittsburgh Medical Center MR Research Center, 8/28/05). Thus, at no time should a label of "MR conditionally safe for thermal issues at [a given field strength]" be applied to any field strength, higher or lower, other than the specific one at which safety was demonstrated.
   Thus, exposure of electrically conductive leads or wires to the RF transmitted power during MR scanning should only be performed with caution and with appropriate steps taken to ensure significant lead or tissue heating does not result (see section H.9, below).
   
3. When electrically conductive materials are required to be within the bore of the MR scanner with the patient during imaging, care should be taken to place thermal insulation (including air, pads, etc.) between the patient and the electrically conductive material, while simultaneously attempting (as much as feasible) to keep the electrical conductor from directly contacting the patient during imaging. It is also appropriate to try to position the leads or wires as far as possible from the inner walls of the MR scanner if the body coil is being used for RF transmission. When it is necessary that electrically conductive leads directly contact the patient during imaging, consideration should be given to prophylactic application of cold compresses or ice packs to such areas.
   
4. Depending on specific magnet designs, care may be needed to ensure that the patient's tissue(s) do not directly come into contact with the inner bore of the MR imager during the MRI process. This is especially important for several higher-field MR scanners. The manufacturers of these devices provide pads and other such insulating devices for this purpose, and manufacturer's guidelines should be strictly adhered to for these units.
   
5. It is important to ensure the patient's tissues do not form large conductive loops. Therefore, care should be taken to ensure that the patient's arms or legs are not positioned in such a way as to form a large-caliber loop within the bore of the MR imager during the imaging process. For this reason, it is preferable that patients be instructed not to cross their arms or legs in the MR scanner. We are also aware of unpublished reports of thermal injuries that seem to have been associated with skin folds, such as in the region of the inner thighs. While the cause of this is not yet fully understood, it might be prudent to consider ensuring that skin folds and other such examples of tissue-to-tissue contact are minimized or eliminated in the region undergoing radiofrequency energy irradiation.
   
6. Skin staples and superficial metallic sutures: Patients requested to undergo MR studies in whom there are skin staples or superficial metallic sutures (SMS) may be permitted to undergo the MR examination if the skin staples or SMS are not ferromagnetic and are not in the anatomic volume of RF power deposition for the study to be performed. If the nonferromagnetic skin staples or SMS are within the volume to be RF-irradiated for the requested MR study, several precautions are recommended.
   
   1. Warn the patient and make sure that they are especially aware of the possibility that they may experience warmth or even burning along the skin staple or SMS distribution. The patient should be instructed to report immediately if they experience warmth or burning sensations during the study (and not, for example, wait until the "end of the knocking noise").
      
   2. It is recommended that a cold compress or ice pack be placed along the skin staples or SMS if this can be safely clinically accomplished during the MRI examination. This will help to serve as a heat sink for any focal power deposition that may occur, thus decreasing the likelihood of a clinically significant thermal injury or burn to adjacent tissue.
      
   
   
7. For patients with extensive or dark tattoos, including tattooed eyeliner, in order to decrease the potential for RF heating of the tattooed tissue, it is recommended that cold compresses or ice packs be placed on the tattooed areas and kept in place throughout the MRI process if these tattoos are in the volume in which the body coil is being used for RF transmission. This approach is especially appropriate if fast spin-echo (or other high RF duty cycle) MRI sequences are anticipated in the study. If another coil is being used for RF transmission, a decision must be made if high RF transmitted power is to be anticipated by the study protocol design. If so, then the above precautions should be followed. Additionally, patients with tattoos that had been placed within 48 hours prior to the pending MR examination should be advised of the potential for smearing or smudging of the edges of the freshly placed tattoo.
   
8. In the unconscious or unresponsive patient, all attached leads that will be in or partly in the volume undergoing RF irradiation should be covered with a cold compress or ice pack at the lead attachment site for the duration of the MR study.
   
9. As noted above, it has been demonstrated that resonant circuitry can be established during MRI between the RF energies being transmitted and specific lengths of long electrically conductive wires or leads, which can thus act as efficient antennae. This can result in heating of the tips of these wires or leads to temperatures in excess of 90°C in a few seconds. Therefore, patients in whom there are long electrically conductive leads, such as Swan-Ganz thermodilution cardiac output–capable catheters or Foley catheters with electrically conductive leads, should be considered at risk for MR studies if the body coil is to be used for RF transmission over the region of the electrically conductive lead. This is especially true for higher-field systems and for imaging protocols utilizing fast spin-echo or other high RF duty cycle MRI sequences. Each such patient should be reviewed and cleared by an attending level 2 radiologist and a risk–benefit ratio assessment performed prior to permitting them access to the MR scanner.
   
10. The potential to establish substantial heating is itself dependent on multiple factors, including, among others, the static magnetic field strength of the MR scanner (as this determines the transmitted radiofrequencies [RF] at which the device operates) and the length, orientation, and inductance of the electrical conductor in the RF-irradiated volume being studied. Virtually any lead lengths can produce substantial heating. Innumerable factors can affect the potential for tissue heating for any given lead. It is therefore critical to recognize that of all electrically conductive implants, it is specifically wires, or leads, that pose the greatest potential hazard for establishing substantial power deposition/heating considerations.
    

Another important consideration is that as a direct result of the above, it has already been demonstrated in vitro that heating of certain implants or wires may be clinically insignificant at, for example, 1.5 Tesla but quite significant at 3.0 Tesla. However, it has also been demonstrated that specific implants might show no significant thermal issues or heating at 3.0 Tesla, but may heat to clinically significant or very significant levels in seconds at, for example, 1.5 Tesla. Thus, it is important to follow established product MR safety guidelines carefully and precisely, applying them to, and only to, the static magnetic field strengths at which they had been tested. MR scanning at either stronger and/or weaker magnetic field strengths than those tested may result in significant heating where none had been observed at the tested field strength(s).

I. Drug Delivery Patches and Pads
Some drug delivery patches contain metallic foil. Scanning the region of the metallic foil may result in thermal injury [22]. Since removal or repositioning can result in altering of patient dose, consultation with the patient's prescribing physician would be indicated in assessing how to best manage the patient. If the metallic foil of the patch delivery system is positioned on the patient so that it is in the volume of excitation of the transmitting RF coil, the case should be specifically reviewed with the radiologist or physician covering the patient. Alternative options may include placing an ice pack directly on the patch. This solution may still substantially alter the rate of delivery or absorption of the medication to the patient (and be less comfortable to the patient, as well). This ramification should therefore not be treated lightly, and a decision to proceed in this manner should be made by a knowledgeable radiologist attending the patient and with the concurrence of the referring physician as well.

If the patch is removed, a specific staff member should be given responsibility for ensuring that it is replaced or repositioned.

J. Cryogen-Related Issues

1. For superconducting systems, in the event of a system quench, it is imperative that all personnel and patients be evacuated from the MR scan room as quickly as safely feasible and that the site access be immediately restricted to all individuals until the arrival of MR equipment service personnel. This is especially so if cryogenic gases are observed to have vented partially or completely into the scan room, as evidenced in part by the sudden appearance of white "clouds" or "fog" around or above the MR scanner. As noted in section B.3.n above, it is especially important to ensure that all police and fire response personnel are restricted from entering the MR scan room with their equipment (axes, air tanks, guns, etc.) until it can be confirmed that the magnetic field has been successfully dissipated, because there may still be a considerable static magnetic field present despite a quench or partial quench of the magnet [23].
   
2. It should be pointed out that room oxygen monitoring was discussed by the MR Blue Ribbon Panel and rejected at this time because the present oxygen monitoring technology was considered by industry experts not to be sufficiently reliable to allow continued operation during situations of power outages, etc.
   

K. Claustrophobia, Anxiety, Sedation, Analgesia, and Anesthesia
Adult and pediatric patient anxiolysis, sedation, analgesia, and anesthesia for any reason should follow established ACR [24, 25], American Society of Anesthesiologists (ASA) [26–29], and JCAHO standards [29].

L. Contrast Agent Safety
1. Contrast agent administration issues
No patient is to be administered prescription MR contrast agents without orders from a duly licensed physician. Intravenous injection–qualified MR technologists may start and attend to peripheral IV access lines if they have undergone the requisite site-specified training in peripheral IV access and have demonstrated and documented appropriate proficiency in this area. IV-qualified MR technologists may administer FDA-approved gadolinium-based MR contrast agents via peripheral IV routes as a bolus or as a slow or continuous injection as directed by the orders of a duly licensed site physician.

Administration of these agents is to be performed according to the ACR policy. The ACR approves of the injection of contrast material and diagnostic levels of radiopharmaceuticals by certified and/or licensed radiologic technologists and radiologic nurses under the direction of a radiologist or his or her physician designee who is personally and immediately available, if the practice is in compliance with institutional and state regulations. There must also be prior written approval by the medical director of the radiology department or service of such individuals. Such approval process must follow established policies and procedures, and the radiologic technologists and nurses who have been so approved must maintain documentation of continuing medical education related to materials injected and to the procedures being performed [30].

2. Prior contrast agent reaction issues

1. According to the ACR Manual on Contrast Media [31], adverse events after intravenous injection of gadolinium seem to be more common in patients who had previous reactions to an MR contrast agent. In one study, 16 (21%) of 75 patients who had previous adverse reactions to MR contrast agents reacted to subsequent injections of gadolinium [31]. Patients with asthma also seem to be more likely to have an adverse reaction to the administration of a gadolinium-based MR contrast agent. Patients with allergies also seemed to be at increased risk (2.0–3.7 times, compared with patients without allergies). Patients who have had adverse reactions to iodinated contrast media are more than twice as likely to have an adverse reaction to gadolinium (6.3% of 857 patients) [31].
   
2. At present, there are no well-defined policies for patients who are considered to be at increased risk for having an adverse reaction to MR contrast agents. However, the following recommendations are suggested: Patients who have previously reacted to one MR contrast agent can be injected with another agent if they are restudied, and at-risk patients can be premedicated with corticosteroids and, occasionally, antihistamines [31].
   
3. All patients with asthma, a history of allergic respiratory disorders, prior iodinated or gadolinium-based contrast reactions, etc., should be followed m