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General Policies For The Performance of Magnetic Resonance Imaging Back to Course Index

 

 

General Policies

For The Performance of

Magnetic Resonance Imaging

 

INTRODUCTION

 

Magnetic Resonance Imaging (MRI) is a non-invasive diagnostic technique that produces computerized images of internal body tissue and is based on nuclear magnetic resonance of atoms within the body, induced by the application of radio waves.  It is primarily used to examine pathological or other physiological alterations of living tissues and is a commonly used form of medical imaging.  MRI images are produced using magnetism, radio waves, and a computer.   The computer generates visual images of the area of the body that was scanned and transfers the information to film.  A radiologist interprets the results and provides information to the attending physician.  MRI scanning is non-invasive, painless, and does not involve X-ray radiation.

 

 MR scanning requires the presence of a strong magnetic field; consequently, everyone in the MR environment is exposed to the field, which may be physically hazardous, or it could attract metal objects to cause either physical damage to an individual or the MRI equipment.  This environment mandates strict adherence to safe practices to protect or minimize risk for all individuals involved in the MRI process.  It also requires a constant awareness of safety practices by all involved in the MRI process and also mandates site access as well as site design and layout restrictions. Consequently, the MR scanning policies and procedures must be in place to control activities within the environment and to control equipment that is allowed into the MR area. Also, one must recognize that MRI is a medical procedure that is not appropriate (safe) for all individuals; consequently, the MRI practice must have guidelines in place that address contraindications and how the risks can be minimized if it is medically necessary to scan a high-risk individual.  For example, scanning may be unsafe for an individual with a heart pacemaker, metal implants, or other metal objects in or on their body.  Also, it may be unsafe to scan any patient with any metal in their eyes. Also, the risks (if any) associated with scanning during pregnancy are not known.  The decision to scan or not scan is often decided after a radiologist makes a risk-benefit assessment.  In any case, a decision to scan these individuals must be made on an individual basis and often requires written consent (informed consent) before the scan.  MRI is performed in an enclosure; accordingly, anyone who is claustrophobic may have a severe psychological reaction to the process.  Sedative medication may be ordered by a physician to moderate this discomfort.

 

The MRI process exposes patients to an uncomfortable and noisy environment (patients lie within a closed chamber on a firm table for about one hour; scan times of up to 1.5 hours are not uncommon) and require them to remain still during the scanning.  Typically, the area being scanned is stabilized (held in position) while undergoing the test. The patient can communicate via intercom with an MRI technologist throughout the test. The patient should be briefed before the scan on what he or she will experience during the test.  Noise is often mentioned as an area of concern as it is often loud and random (earplugs are recommended during the scan).  The patient’s anxiety level can be significantly reduced if he or she is aware of the noise and other unique attributes of the scan before his or her exposure.    

 

MRI FUNCTION

 

In essence, MRI is a multi-planar imaging method based on an interaction between radio frequency (RF) electromagnetic fields and certain nuclei in the body (normally hydrogen nuclei) after the body has been placed in a strong magnetic field.  MRI can differentiate between normal and abnormal tissues, providing a sensitive examination to detect disease.  This sensitivity is based on the high degree of inherent contrast due to variations in the magnetic relaxation properties of different tissues, both normal and diseased, and the dependence of the MR signal on these tissue properties.

 

MRI technology is complex and one needs a technical background to master the technical aspects of how it works; consequently, this CEU will provide only general information related to MRI operational characteristics and will focus primarily on the safe practices related to MRI.

 

MRI MACHINE

 

Most MRI machines look like large cubes.  The overall dimensions are approximately six feet tall, five feet wide, and eight feet long.  The machine is constructed with a horizontal tube extending through the magnet from front to back.  The patient slides into the tube via a special table.  MRI machines vary in size and shape with newer models designed for more openness around the sides.  New models of MRI machines are also shrinking due to technological improvements.  The MRI systems consist of the following major components:

 

o      Field magnets

o      Gradient magnets (located inside the main magnet; they are turned “on” and “off” very rapidly in a specific manner and alter the main magnetic field on a very local level). A picture or “slice” of a particular area can be generated.

o       Radio Frequency (RF) pulses; specific to hydrogen; cause protons to spin or process; applied via coils that generally conform to areas being scanned.

o      Skilled staff (radiologists, technologists, etc.)

o      Computer

 

MAGNET TECHNOLOGY

 

Magnets are rated using a measure of flux density known as Tesla. Tesla is the SI (International system of units) derived unit of magnetic flux density (or magnetic induction).   It is used to define the intensity or density of a magnetic field.  The Tesla, is equal to one Weber per square meter, as defined in 1960.  As such, an MRI magnet is rated by the amount of magnetic flux or Tesla it generates.  The magnets in most MRI machines are in the 0.5 to 2.0-Tesla range.  Magnetic fields in the range of   2-Tesla to 3-Tesla have been approved for medical imaging; however, more powerful magnets (over 50-Tesla) are used in research.  For comparison purposes, the Earth’s magnetic field is approximately 0.5 gauss (1 Tesla equals 10,000 gausses); consequently, these magnets are many times more powerful than the Earth’s magnetic field.

 

The field magnets in MRI machines are generally electromagnets that rely upon the electric current flowing through a coil to generate a magnetic field when the current increases so do the magnetic field.  The electromagnets are constructed with large coils of wire that are wrapped around a cylinder or bore.  An electric current passes through the windings and generates a magnetic field.  This magnet requires a large amount of electricity to operate because of the natural resistance in the wire. This type of magnet is limited to approximately 0.3-Tesla-level machines due to cost. The second type of electromagnetic is the superconducting magnets:  This is a special design where the coil wires are continuously bathed in helium at approximately 452 degrees below zero.  This environment causes the wire resistance to decrease to near zero; consequently, the power requirements for the system are dramatically reduced that in turn significantly reduces the systems operating cost.  The patient is protected from helium via thermal insulation.  The patient would be unaware of this feature unless he was briefed during orientation.

 

The amount of attraction a magnet has for a ferromagnetic object is directly related to the distance between the object and the magnet. Specifically, the force increases exponentially as the object transcends through the field and approaches the magnet.   Consider the consequences should a person carry a large metal object into the scan area.  At 15 to 20 feet, there would be a slight pull on the object, take a few steps closer to the magnet and the force increases significantly.  When the individual gets to within two or three feet of the magnet the force would be strong enough to remove the object from the person’s grasp and accelerate it toward the magnet.

 

As stated previously, magnets are attracted to or repelled by, other materials.  A material that is strongly attracted to a magnet is said to have a high permeability.  Iron and steel are examples of materials with very high permeability, and they are strongly attracted to magnets.  Whereas, water has very low permeability and is slightly repelled by magnetic fields.  Everything has a measurable permeability: people, gases, and even the vacuum of outer space. 

 

A comparison of magnetic field strength helps us understand the relative strength of one magnet versus another and also the natural magnetic field strength of planet earth.  It is also helpful to relate the effects when one is in the scan area. To begin with, it can be a very dangerous place if proper precautions are not taken.  For example, any metal object in the scan area can be drawn toward the magnet and become a dangerous projectile.  The projectiles may cause a threat to the patient, and staff or could damage the MRI machine. There have been incidents reported where patients have been injured or killed due to flying objects in the scan area.  Special awareness and care must be taken to minimize the risk of this type of accident

 

QUALIFICATIONS AND RESPONSIBILITIES OF MRI PERSONNEL

 

Physician/Radiologist

 

Most physicians examine patients, diagnose illnesses and administer treatment for people suffering from a disease.  From the general population of physicians, the American Medical Association indicates that approximately 2% specialize in radiology. The most significant difference is that the radiologist diagnoses disease by obtaining and interpreting medical images whereas other physicians depend on examinations and standard test results for their diagnosis.  In a radiology practice, the radiologist has the responsibility for all aspects of the intervention including but not limited to: reviewing all indications for the examination, specifying the pulse sequence to be performed, specifying the use and dosage of contrast agents, interpreting images, generating written reports, and assuring the quality of both the images and interpretations.  Some images are obtained by using X-rays or radioactive substances, and others use sound waves or the body’s natural magnetism.  A radiologist correlates medical image linking with other examinations and tests, recommends further examinations or treatments, and confers with referring physicians (the doctors who send patients to the radiology laboratory for testing).  Radiologists also treat some diseases using radiation (radiation oncology) or minimally invasive image surgery (interventional radiology).

 

Radiologists must have graduated from a four (4) year, accredited medical school, passed a licensing examination, and completed a residency program.  Radiologists are usually board certified, indicating that they have taken and passed an examination and thus approved to practice in the field of Radiology by the American Board of Radiology, the American Osteopathic Board, or the Royal College of Physicians and Surgeons of Canada. 

 

Physician/Radiologist Subspecialties

 

The last part of the 20th century and the 21st century is the age of specialization in the medical and many other disciplines.  Radiology is no exception as can be seen from the following list:

o      Radiologist specialty for various parts of the body (examples are breast, cardiovascular, chest, gastrointestinal, head/neck, musculoskeletal, neuroradiology, genitourinary, and others).  A radiologist specializes in the unique challenges associated with their specialty. For example, the radiologist with a chest specialty is concerned with the diagnostic radiology of diseases of the thorax, especially the heart and lungs.

o      Computed Tomography (CT) is concerned with diagnostic radiology using computerized radiologic equipment that demonstrates both bone and soft tissues.

o      Magnetic Resonance Imaging subspecialty relates to diagnostic radiological modality using nuclear magnetic resonance technology.

o       Ultrasound subspecialty is concerned with the use of high-frequency sound waves and other techniques for medical diagnosis.

 

Medical Physicist

 

A medical physicist is generally responsible for overseeing the equipment quality control program and for monitoring performance upon installation and routinely thereafter.  He or she is the individual who is competent to practice independently one or more of the subfields in medical physics.  The American College of Radiology considers that certification and continuing education in the appropriate subfield (s) demonstrate that an individual is competent to practice one or more of the sub-fields in medical physics and to be a Qualified Medical Physicist.  The sub-fields are: Therapeutic Radiological Physics, Diagnostic Radiology Physics m Medical Nuclear Physics, and Radiological Physics

 

Technologist

 

A radiologist technologist assists the radiologist.   Some of the tasks they perform are:

o      Implement MR Safety practices: control access to the restricted areas; conduct safety screening procedures; conduct MR Hazard checklist; provide instruction to patients; etc.

o      Operate the radiographic equipment;

o      Brief patient regarding procedures to be run, run time, and operational characteristics of the equipment (noise, space, etc.);

o      Position the patient on the table and attach coils as required;

o      Assure the patient is as comfortable and safe as possible during the test;

o      Align patient and able to obtain an optimum view of a specific body part;

o      Install radiation protection devices such as lead shields to prevent unnecessary radiation exposures to parts of the body that is not being scanned (for example, it may be appropriate to shield the head/eyes when the image of the chest is being made;

o, Communicate with the patient during the test.

 

A technologist usually has a college degree (associate or bachelor’s), from one to four years of formal training, and a certification from The American Registry of Radiologic Technologists  (ARRT) or equivalent.  All technologists must maintain current certification in American Heart Association Basic Life Support at the health care provider level. All technologists must be trained as level 2 MR personnel during their orientation before being permitted free access to the MR scan area (Zone III/IV).  The level 2 training consists of extensive training and education 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.  It is generally the responsibility of the MR director to identify the required training and to identify those individuals who qualify as level 2 MR personnel.

 

Radiological Nurse

 

The responsibility of the radiological nurse is to help meet the physical, mental, and emotional needs of the patient.  The nurse is typically responsible for the development and implementation of an individual treatment/care plan that identifies the process and procedures to be run on the patient.  The nurse also coordinates the plan with the patient to help them understand the treatment objectives and goals. As prescribed/ordered by the radiologist, the nurse can perform examinations or carry out preventive health measures.  The nurse may also assist during examinations and be responsible for medical records.

 

Radiological nurses practicing in Florida are required to meet all state requirements for licensure and practice and to have graduated from an accredited nursing school.  The nurse must also pass a state-approved licensing examination.

 

SAFE-PRACTICE CONCEPTS

 

The hazards associated with MRI magnets attracting metal objects are fairly well documented and most individuals who work with MRI equipment have been trained regarding how to protect themselves and others.  It is also fairly well known that as the higher-powered magnets (3.0 Tesla and higher) are introduced into the workplace there will be a corresponding increase in the hazards.  It is interesting that we depend a lot on our senses (sight, smell, feel, etc.) to alert us to potential hazards; unfortunately, the MRI equipment is rather benign and does not smell or give off any visible signs that would indicate an active state (no one can see or smell a magnetic field).  Consequently, when an unsuspecting worker or patient with a metal object (such as a ferromagnetic oxygen cylinder) is exposed to this environment a catastrophic outcome may occur as the forces of the magnetic field act upon the object and attract it toward the core of the magnetic.  The object can accelerate rapidly and become a projectile that may harm individuals or damage equipment.     

 

In the clinical setting, the principal surrounding “standard of care” is implemented to serve and protect patients in the MRI area.  In general, the standard of care is based on accessibility, availability, and best practices (those that are established in the industry) for the delivery of service to the patient.  For MRI, the concept of protection is extended to others (security, housekeeping personnel, firefighters, police, etc) that need to enter the area. This approach is dependent upon the expertise, training, and professionalism of the MRI staff to assure the safetypatientsient and support personnel; consequently, we are all human and some are more dedicated to providing safe health care than others; consequently, there have been numerous incidents of unsafe practices in the MRI industry.  Most are looked at as operational issues or explained away as operator errors with a recommendation to increase training or supervision.  However, MRI safety is still a concern and most believe that it must be addressed at the facility (site) level as well as at the operational level.  The best approach to increasing operational safety is through the implementation of comprehensive MRI safe-practice standards while continuing to implement effective personnel training and certification.  This approach should increase overall awareness of the hazards inherent in the MRI industry and how to prevent/avoid injuries to personnel and damage to equipment.  

 

As noted previously, overall MRI safety is dependent upon personnel and management approaches as well as site design considerations.  The most comprehensive “guidance” for operational as well as site design considerations is contained in ACR White Paper on Magnetic resonance (MR) Safety—Combined Papers of 2002 and 2004).  The following excerpts were taken (some almost verbatim) from the white paper with the hope that they will stimulate others to become more aware of the need to implement MRI safe-practice procedures and to increase their interest in more safe design and layout of future MRI sites.  The overall objective is to set the stage for a safer MRI environment.

 

Introduction To Safe-Practices/Site Design Concepts

 

Following a fatal accident at an MRI facility, the American College of Radiology (ACR) convened a panel to review existing MR safe practices and to issue new guidance for MRI suite design and various other aspects relating to MRI safety.  Some specific recommendations are listed below:

 

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

o      All sites should maintain MR safety policies and procedures, which are to be reviewed and updated, as appropriate.  Compliance should be assessed and documented annually.  The policies and procedures manual should be available to the MR professionals at all times.

o      MRI policies and procedures should be reviewed concurrently with the introduction of any significant equipment or procedural changes in the MR environment of the site (e.g., adding faster or stronger gradient capabilities or higher RF duty cycle studies).

o      It is the responsibility of the site administrator to ensure that the policies and procedures are adhered to at all times by MR personnel and others who support MRI activities.

o      Procedures should require that all adverse events, MR safety incidents, or “near incidents” are reported to the medical director in a timely fashion (typically one business day).

 

(B) Static Magnetic Field Issues: Site Access Restriction

         

1.     Zoning—As the magnetic field is increasing due to more powerful magnets, more attention must be applied to the design and layout of the MRI facility.  It is now fairly standard to employ a layout that consists of four zones with varying levels of MR safety practices invoked for each.  It is also important to note that a magnetic field may be present beyond the standard boundaries of the MRI site and could expose unsuspecting individuals as they pass near an MR scanner; consequently, when a site safety evaluation is performed all adjacent areas (including vertical and horizontal) should be evaluated for the level of magnetic field and properly controlled if the field strength exceeds 5 G.

 

Zone I:  Is outside the influence of the magnetic field and is freely accessible to the general public.  Access to the MR environment is through zone 1.

 

Zone II:  Zone II is primarily a patient processing area.  It is where the patients answer the MR screening questionnaire, provide patient history, answer insurance questions, and provide other related health care information.  Patients are under the supervision of MR personnel and their movement within Zone II is controlled.   

 

Zone III: All access to Zone III is physically restricted from general public access.  Access is generally limited/controlled by key locks, passkey locking systems, or any other reliable method that can differentiate between MR personnel and non-MR personnel.  Only MR personnel should be provided free access, such as access keys or passkeys.  The regions within Zone III (including Zone IV) are also controlled and under the supervision of MR personnel.

 

Non-MR personnel (including hospital or site administration, physicians, and security) are not to be provided with independent Zone III access until they undergo the proper education and training to become MR personnel themselves.  Zone III, or at least the area within it wherein the static magnetic field’s strength exceeds 5 G, should be demarcated and marked as being potentially hazardous.

 

Zone IV: Zone IV contains the MR scanner and is located within Zone III, as it is the MR magnet and the associated magnetic field that generates the existence of Zone III.  Zone IV should also be demarcated and marked as being potentially hazardous due to the presence of very strong magnetic fields.  The Zone IV layout should provide for direct visual observation by level 2 MR personnel to access pathways into Zone IV.  The MR technologists should be able to directly observe, via line of site or video monitors, the entrances or access corridors to Zone IV from the control center or other station as appropriate.

 

Zone IV should contain a red light that indicates the “magnet is on” and it should be illuminated at all times (except for resistive systems).  There should be an emergency backup power source to continue to illuminate for at least 24 hours following a power outage.

 

In case of a cardiac or respiratory arrest or another medical emergency within Zone IV for which emergency care is required, appropriately trained 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 magnetically safe location.  All priorities should be focused on stabilizing the patient and then evacuating the patient as rapidly and safely as possible from the magnetic environment that might restrict safe resuscitative efforts.

 

            2. Personnel Classification

 

Non-MR personnel:  This classification refers to any individual or group who has not undergone formal training in MR safety within the previous 12 months.  This classification may include patients, patient families, visitors, facility staff, or other support personnel.

 

Level 1 MR Personnel:  Individuals who have completed formal safety educational efforts to ensure their safety as they work within Zone III/IV are classified as Level 1 MR personnel.  This typically includes MRI department staff, patient aids, and other MRI support staff.

 

Level 2 MR Personnel:  This classification includes individuals 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.  This classification generally includes MR technologists, radiologists, and radiology department nursing staff.

 

2.     Screening of patients and non-MR personnel (See Forms 1 and 2)

 

Access:  All non-MR personnel must pass an MR safety screen before admittance into zone III.  The screening procedure is to be administered by MR personnel.  The screening process and screening forms for patients, non-MR personnel, and MR personnel should be essentially identical.  Specifically, one should not assume that non-MRI personnel, health care practitioners, or MR personnel would not enter the bore of the MR scanner during the MRI process.  For example, a pediatric patient cries for his mother, who then leans into the bore, or the anesthetist leans into the bore to manually ventilate.

 

Non-MR personnel:  Non-MR personnel should be accompanied by or under the supervision of a Level 2 MR person while they are in Zone III/IV except when the non-MR person is in the dressing room or restroom.  At these times, the level 2 person should be able to communicate with the Non-MR person.

 

Level 1 MR personnel are permitted unaccompanied access throughout Zones III and IV.  Also, they are generally permitted to be responsible for accompanying non-MR personnel into and throughout Zone III.  However, level 1 MR personnel are not permitted to directly admit, or be designated responsible for, non-MR personnel in Zone IV.

3) Precautionary measures:

1.     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 piercing (if removable), contraceptive diaphragms, metallic drug delivery patches, cosmetics containing metallic particles and clothing items that may contain metallic fasteners, hooks, zippers, loose metallic components, or metallic threads.

2.     All patients and non-MR personnel with a history of potential ferromagnetic foreign object penetration must undergo further investigation before being permitted entrance to Zone III.  It is recommended that a radiologist conduct the investigation.

3.     Conscious patients and research and volunteer subjects are to complete written MR safety-screening questionnaires before their introduction to Zone III.  Family or guardians of non-responsive patients or patients who cannot reliably provide their medical histories are to complete a written MR-safety screening questionnaire before their introduction 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 record.

4.     Screening of the patient or non-MR personnel with, or suspected of having, an intracranial aneurysm clip should be performed per the separate MR safe-practice guideline addressing this particular topic.  In the event a patient is identified to have an intracranial aneurysm clip in place, the MR examination should not be performed until it can be documented that the type of clip within that patient is MR-safe or compatible.  All implanted intracranial aneurysm clips that are documented in writing to be composed of titanium (either commercially pure or titanium alloy types) can be accepted for scanning without any other testing.  Barring the availability of either pretest or prior MRI data of the clip in question, a risk-benefit assessment and review by a radiologist must be performed in each case individually. Further, for patients with intracranial clips with no available ferromagnetic or imaging data, should the risk-benefit ratio favor the performance of the MR study, the patient or guardian should provide written informed consent that includes death as a potential risk of the MRI procedure before permitting that patient to undergo an MR examination.

5.     Screening of patients for whom an MR examination is deemed clinically indicated or necessary but who are unconscious or unresponsive or who cannot provide their reliable histories regarding prior possible exposure to surgery, trauma, or metallic foreign objects and for who such histories cannot be reliably obtained from others it is recommended that such patients be physically examined by level 2 MR personnel.  It further assumes that the medical necessity is such that it is not prudent to wait until the patient recovers sufficiently to personally provide the information.

6.     For the safety of firefighters, police, and other emergency responders, it is recommended that all calls originating from or located in the MR site should be forwarded simultaneously to a specifically designated individual from amongst the site’s MR personnel.  This individual should, if possible, be on site before the arrival of the firefighter or emergent responders to ensure that they do not have free access to Zone III/IV.  It should be stressed that, even in the presence of a true fire (or another emergency) in Zone III/IV, the magnetic fields may be present and fully operational.  Therefore, free access to Zone III/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 others in the vicinity.

7.     MR personnel screening:  All MR personnel should undergo an MR screening during orientation (for new hires) or upon a work assignment in the MR area to ensure their safety in the MR environment.  Also, all personnel must immediately report to the MR medical director or equivalent any trauma, procedure, or surgery they experience or undergo where a ferromagnetic metallic object or device may have been introduced within or on them.

8.     Device and object screening: It is recommended that all MRI sites have access to a handheld magnet (> 1000 G) to enable them to test external, and even some superficial internal, devices or implants for the presence of ferromagnetic attraction forces.  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 non-ferromagnetic and either MR-safe or MR-compatible before permitting them into Zone III.  Examples of devices that need to be positively identified include fire extinguishers, oxygen tanks, and aneurysm clips. External devices or objects demonstrated to be ferromagnetic and MR unsafe or incompatible may still under specific circumstances, be brought into Zone III if they are under the direct supervision of specifically designated Level 1 or 2 MR personnel who are thoroughly familiar with the device, its function, and the reason supporting its introduction to Zone III.  The 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.

 

C)          Pregnancy-Related Issues:

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 for the patient warrants that the study is performed.  The radiologist should confer with the referring physician and document the following in the radiology report or the patient’s medical record:

o       The information requested from the MR study cannot be acquired via non-ionizing means;

o       The data is needed to potentially affect the care of the patient or fetus during the pregnancy;

o       The referring physician does not feel it is prudent to wait until the patient is no longer pregnant to obtain this data.

 

MR contrast agents should not be routinely provided to pregnant patients.  The decision to use a contrast agent 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 the particular patient.  It is also recommended that pregnant patients undergoing an MR examination provide written informed consent to document that they understand the 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.

 

D)               Pediatric MR safety concerns:

Children are the largest group of patients requiring sedation for MRI because they cannot remain motionless during scans.  Adherence to standards of care mandate sedation providers follows the guidelines developed by the American Academy of Pediatrics, the American Society of Anesthesiologists, and the Joint Commission on Accreditation of Healthcare Organizations.  Also, sedation providers must comply with the protocols established by the individual state and the practicing institution.  The guidelines require the following provisions:

o  Medical history and examination for each patient

o  Adherence to fasting guidelines appropriate for the age

o  Uniform training and credentialing for sedation providers

o  Intra-procedural and post-procedural monitors with adapters appropriately sized for children (compatible with the magnetic field).

o  Method of patient observation

o  Resuscitation equipment, including oxygen delivery and suction.

For the neonatal and the young pediatric population, special attention is needed in monitoring body temperature in addition to other vital signs.  Also, ensure specialty items such as neonatal isolation transport units are MR compatible. It is also common for the pediatric population to request/require an accompanying parent or guardian during the MRI procedure; consequently, those accompanying or remaining with the patient should be screened using the same criteria as anyone else entering Zone IV.

 

E)     Patients in Whom There Are or May Be Cardiac Pacemakers or Implantable Cardioverter Defibrillators:  It is recommended that the presence of implanted cardiac pacemakers or implanted cardioverter defibrillators (ICDs) be considered contraindicated for routine MRI.  Should an exception be considered, it should be done on a case-by-case and site-by-site basis and only if the site is manned with individuals with the appropriate radiology and cardiology knowledge and expertise on hand.

    

MRI safety is a challenging effort for all individuals associated with the imaging process.  The operational part required trained and dedicated MR personnel, comprehensive processes and procedures, and dedicated staff to ensure that all of the safety controls are consistently imposed and implemented. It is also important to focus on the site design, layout, and control to ensure safety inside and outside the MRI site.  This Continuing Education Course has introduced the reader to several aspects of MRI safety and hopefully will encourage the reader to investigate and go beyond the concepts introduced herein.  I would be remiss if I did not mention that this CEU is limited in scope and is not all-inclusive regarding MRI safety. 

Future CEU courses will address additional MRI safety issues.

 

 

REFERENCES

 

ACR Guidance Document for Safe MR Practices: 2007

 

New Standard of Practice for the Design of MRI Facilities, AIA, 2005

 

Careers in Diagnostic Radiology, RadiologyInfo

 

Various web sites

 

 

FORMS

 

Form-1            Safety Screening Form

 

Date: __________            Name: _______________

Male [] Female  []          DOB ________            Weight ________            Height _____

 

Reason for examination: _______________            Medical Problem: ______________ ________________________________________________________________________

 

Have you ever had an MRI examination before and had a problem?            Yes            No

            If yes, please describe:

 

Have you ever had a surgical operation or procedure of any kind?            Yes            No

            If yes, list all prior surgeries and approximate dates:

 

Have you ever been injured by a metal object or foreign body            Yes            No

(e.g., bullet, shrapnel)?

            If yes, please describe:

 

Have you ever been injured from a metal object in your eye (metal             Yes            No

slivers, metal shavings, and other metal objects)?

                        If yes, did you seek medical attention?

                        If yes, describe what was found:

 

Do you have a history of kidney disease, asthma, or other allergic            Yes            No

respiratory disease?

            If yes, please describe:

 

Do you have any drug allergies?                                                                      Yes            No

            If yes, please list the drugs:

 

Have you ever received a contrast agent or X-ray dye used for             Yes            No

MRI, CT, or other X-ray or study?

            If yes, please describe:

 

Have you ever had an X-ray dye or MRI contrast agent               Yes            No

allergic reaction?

            If yes, please describe:

 

Are you pregnant or do you suspect you may be pregnant?            Yes            No

 

Are you breastfeeding?                                                                        Yes            No

 

What was the date of your last menstrual period: ________

 

Are you postmenopausal?                                                                      Yes            No

 

            Form completed by: _______            Date: ________

 

 

FORM 2:            MR Hazard List

 

Please indicate the location of any metal inside your body or the site of the surgical operation.

Sketch body and show location:

 

The following items may be harmful to you during your MR scan or may interfere with the MR examination.  You must provide a “yes” or “no” for each item.  Please indicate if you have had any of the following:

 

Yes      No      

___      ___            Any type of electronic, mechanical, or magnetic implant

Type:

___      ___            Cardiac pacemaker

___      ___            Aneurysm clip

___      ___            Implanted Cardiac Defibrillator (ICD)

___      ___            Neuro-stimulator

___      ___            Bio-stimulator

                        Type:

___      ___            Any type of infernal electrodes or wires

___      ___            Halo vest

___      ___            Spinal fixation device

___      ___            Any type of coil, filter, or stint

                        Type:

___      ___            Any type of metal object (eg, shrapnel, bullet, BB)

___      ___            Artificial heart valve

___      ___            Any type of implant

___      ___            Penile implant

___      ___            Artificial eye

___      ___            Eyelid spring

___      ___            Any type of implant held in place by a magnet

                        Type:

___      ___            Any type of surgical clips or staple

___      ___            Any IV access port (eg, Broviac, Port-a-Cath, Hickman, PICC line)

___      ___            Medication patch (eg, nitroglycerine, nicotine)

___      ___            Shunt

___      `___            Artificial limb or joint

                        What and where:

___      ___            Tissue expander (eg, breast)

___      ___            Removable dentures, false teeth, or partial plate

___      ___            Diaphragm, IUD, Pessary

                        Type:

___      ___            Surgical mesh

                        Location:

 

___      ___            Body piercing

                        Location:

___      ___            Wig, hair implants

___      ___            Tattoos or tattooed eyeliner

___      ___            Radiation seeds (eg, cancer treatment)

___      ___            Any implanted items (eg, pins, rods, screws, nails, plates wires)

___      ___            Any hair accessories (eg, bobby pins, barrettes, clips)

___      ___            Jewelry

___      ___            Any other type of implanted item

                        Type:

 

Completed by: _______________      Date: ____________



 

Attachment:

 

The Occupational Health and Environment Control standard Number 1910.978 stipulated the requirements for

Nonionizing radiation.  The standard is as follows:

 

 

 

1910.97(a)

“Electromagnetic radiation” –

1910.97(a)(1)

“Definitions applicable to this paragraph.”

1910.97(a)(1)(i)

The term “electromagnetic radiation” is restricted to that portion of the spectrum commonly defined as the radio frequency region, which for this specification shall include the microwave frequency region.

1910.97(a)(1)(ii)

“Partial body irradiation.” Pertains to the case in which part of the body is exposed to the incident electromagnetic energy.

1910.97(a)(1)(iii)

“Radiation protection guide.” Radiation levels should not be exceeded without careful consideration of the reasons for doing so.

1910.97(a)(1)(iv)

The word “symbol” as used in this specification refers to the overall design, shape, and coloring of the rf radiation sign shown in figure G-11.

..1910.97(a)(1)(v)

1910.97(a)(1)(v)

“Whole body irradiation.” This pertains to the case in which the entire body is exposed to the incident electromagnetic energy or in which the cross-section of the body is smaller than the cross-section of the incident radiation beam.

1910.97(a)(2)

“Radiation protection guide.”

1910.97(a)(2)(i)

For normal environmental conditions and incident electromagnetic energy of frequencies from 10 MHz to 100 GHz, the radiation protection guide is 10 mW/cm. (2) (milliwatt per square centimeter) as averaged over any possible 0.1-hour period. This means the following:

Power density: 10 mW./cm.(2) for periods of 0.1-hour or more.
Energy density: 1 mW.-hr./cm.(2) (milliwatt hour per square
 centimeter) during any 0.1-hour period.
 

This guide applies whether the radiation is continuous or intermittent.

1910.97(a)(2)(ii)

These formulated recommendations pertain to both whole-body irradiation and partial-body irradiation. Partial body irradiation must be included since it has been shown that some parts of the human body (e.g., eyes, testicles) may be harmed if exposed to incident radiation levels significantly more than the recommended levels.

1910.97(a)(3)

“Warning symbol.”

1910.97(a)(3)(i)

The warning symbol for radio frequency radiation hazards shall consist of a red isosceles triangle above an inverted black isosceles triangle, separated and outlined by an aluminum color border. The words “Warning – Radio-Frequency Radiation Hazard” shall appear in the upper triangle. See figure G-11.

..1910.97(a)(3)(ii)

1910.97(a)(3)(ii)

American National Standard Safety Color Code for Marking Physical Hazards and the Identification of Certain Equipment, Z53.1-1953 which is incorporated by reference as specified in Sec. 1910.6, shall be used for color specification. All lettering and the border shall be of aluminum color.

1910.97(a)(3)(iii)

The inclusion and choice of warning information or precautionary instructions are at the discretion of the user. If such information is included it shall appear in the lower triangle of the warning symbol.

                         

1910.97(a)(4)

“Scope.” This section applies to all radiation originating from radio stations, radar equipment, and other possible sources of electromagnetic radiation such as those used for communication, radio navigation, and industrial and scientific purposes. This section does not apply to the deliberate exposure of patients by, or under the direction of, practitioners of the healing arts.

[61 FR 9227, March 7, 1996]

 

 

 

 

 

 

 

 

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