Frank G. Shellock, PhD, FACC, FACSM

 has been an important diagnostic imaging modality for almost 30 years. Advancements in technology and imaging protocols have contributed to the growth of MRI applications and expanded the demographic of patient populations from neonates to high-risk patients. The use of sedation or anesthesia is necessary for certain MRI examinations, especially for pediatric or critically-ill patients.

 Importantly, the volume of pediatric patients undergoing MRI or computed tomography (CT) procedures under sedation or anesthesia has grown at an annual rate of 8 percent to 9 percent.

This monograph focuses on the need to monitor body temperature in patients during MRI and discusses the sites to record temperature based on efficacy and stability of the measurement, as well as the response time (i.e., the temporal resolution) during temperature fluctuations.

Monitoring Patients in the MRI Environment

Conventional monitoring equipment and accessories were not designed to operate in the harsh MRI environment that utilizes electromagnetic fields that can adversely affect or alter the operation of these devices.

 Fortunately, various monitors and other patient support devices have been developed to perform properly during MRI procedures.

MRI health care professionals must consider the ethical and medico-legal ramifications of providing proper patient care, which includes identifying patients who require monitoring in the MRI setting and following a proper protocol to ensure their safety by using appropriate equipment, devices, and accessories.

 The early detection and treatment of complications that may occur in high-risk, critically-ill, sedated, or anesthetized patients undergoing MRI examinations can prevent relatively minor issues from becoming life-threatening situations.

Monitoring during an MRI procedure is indicated whenever a patient requires observations of vital physiologic parameters due to an underlying health problem or is unable to respond or alert the MRI technologist or other health care professional regarding pain, respiratory problem, cardiac distress, or difficulty that might arise during the examination.

 In addition, a patient should be monitored if there is a greater potential for a change in physiologic status during the MRI procedure.

Table 1 summarizes the patients who require monitoring and support during MRI procedures. Besides patient monitoring, various support devices and accessories may be needed for use in high-risk patients to ensure safety.

Table 1. Patients who require monitoring and support during MRI procedures 

Patients undergoing MRI examinations while under sedation or general anesthesia require the same standard of care as provided in operating rooms and intensive care units (ICUs)(5). This includes monitoring vital physiological parameters including the electrocardiogram (ECG), oxygen saturation, blood pressure, end tidal carbon dioxide (CO2), and body temperature.

 The use of sedation or anesthesia is necessary for certain MRI examinations, especially for pediatric or critically ill patients.

 Importantly, children represent the largest group requiring sedation for MRI exams

 Sedation is used on children to minimize discomfort, motion, and anxiety during the procedure.

 The American Academy of Pediatrics and the American College of Radiology have published guidelines for monitoring children and adults during sedation

 The vital signs that must be monitored include the heart rate, blood pressure, respiratory rate, and temperature.

Because of the widespread use of MRI contrast agents and the potential for adverse effects or idiosyncratic reactions to occur, it is prudent to have appropriate monitoring equipment and accessories readily available for the proper management and support of patients who may experience side effects. This is emphasized because adverse events, while extremely rare, may be serious or life threatening. In addition, patients may have adverse reactions to other medications while undergoing MRI procedures.

In 1992, the Safety Committee of the Society for Magnetic Resonance Imaging published guidelines and recommendations concerning the monitoring of patients during MRI procedures.

 This information indicates that all patients undergoing MRI examinations should be visually (e.g., using a camera system) and/or verbally (e.g., intercom system) monitored, and that patients who are sedated, anesthetized, or are unable to communicate should be physiologically monitored and supported by the appropriate means.

Injuries and fatalities have occurred in association with MRI examinations. These may have been prevented with the proper use of monitoring equipment and devices

 Notably, guidelines issued by the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) indicate that patients receiving sedatives or anesthetics require monitoring during administration and recovery from these medications.

 Other professional organizations similarly recommend the need to monitor certain patients using proper equipment and techniques.

In human subjects, “deep” body or core temperature is regulated between 36oC and 38oC by the hypothalamus and continuously fluctuates due to diurnal, internal, as well as external factors.

 Importantly, the regulation of body temperature is suppressed by anesthesia and generally results in the patients becoming hypothermic.

 Side-effects of a decrease in body temperature can range from hypovolemia, myocardial ischemia, cardiac arrhythmia, pulmonary edema, decreased cerebral blood flow in cases of mild hypothermia, to mortality related to extreme hypothermia.

Additionally, some patients may experience malignant hyperthermia, which is a rare life-threatening condition that is usually triggered by exposure to certain drugs used for general anesthesia. In susceptible individuals, these drugs can induce a drastic and uncontrolled increase in skeletal muscle oxidative metabolism, which overwhelms the body's capacity to supply oxygen, remove carbon dioxide, and regulate body temperature. Malignant hyperthermia can eventually lead to circulatory collapse and death if not quickly identified and treated.

The anesthesiologist or nurse anesthetist may not be in the immediate proximity of the patient during the MRI procedure due to the design of the MR system. Therefore, it is imperative to continuously monitor the body temperature and provide real time information to the anesthesia healthcare professional. It is also important that the measurement site has clinical relevance and a relatively “fast” response time to any fluctuation in body temperature because the anesthesiologist or nurse anesthetist is unable to visualize the discoloration of the patient skin in cases of sudden temperature changes.

Measuring Body Temperature During an MRI 

The accuracy and efficacy of the measurement of body temperature has been a topic of discussion for many years.

 Temperature measurements in human subjects is affected by, the following factors:

- The site of measurement (e.g., skin, oral, esophagus, rectal, pulmonary artery, hypothalamus, bladder, tympanic membrane, axillary area).
- Environmental conditions (temperature and humidity).
- The measurement technique (e.g., mercury thermometer, electronic thermometer, thermistor probe or catheter, thermocouple-based probe, infrared radiation readers, fiber optic method).

The most accurate body temperature is measured at the hypothalamus, but this site is not accessible by any practical means. Therefore, a “deep” body site that directly reflects the temperature “sensed” by the hypothalamus will provide clinically relevant information.

 For example, sites that provide high levels of accuracy and correlation to deep body temperature are pulmonary artery blood, urinary bladder, the esophagus, and rectum.

 However, the temporal resolution for each site varies, which can dramatically impact the ability to recognize clinically important changes that may require prompt patient management.

When monitoring temperature during MRI, the decision on which body site to use should be based on accuracy as well as accessibility. There may be limitations on the type of equipment available for temperature measurements in the MR system room.

 For example, hard wire thermistor or thermocouple-based sensors are prone to measurement errors due to electromagnetic interference (EMI) and may introduce artifacts in the MR images.

 Fiber optic sensors (i.e., fluoroptic thermometry) are optimally used to record temperatures in the MRI environment because they safe and unaffected by EMI.

In the MRI setting, anesthesiologists, nurse anesthetists, and clinicians may feel that they are limited to measure “surface” temperatures, such as those in the skin, axilla, and groin. However, these temperature measurement sites are very problematic insofar as they do not properly reflect “deep” body temperature. Another option is to use minimally invasive measurement techniques to record temperature in the rectum or esophagus.

While a so-called “surface” temperature site (i.e., skin, axilla, and groin) tends to be used for temperature recordings during MRI mainly because of the ease of obtaining the measurement with currently available equipment, this method does not provide an accurate representation of body temperature and is susceptible to substantial variations and erroneous information relative to the “deep” body temperature, due to the specific site selected for temperature probe placement, patient movement, and environmental conditions.

Notably, recording skin or surface temperature during MRI can be influenced by the level of the patient’s perspiration due to RF heating and the use of blankets or air circulation from the fan in the bore of the MR system. Additionally, investigations have demonstrated that peripheral vasoconstriction resulting from skin surface cooling decreases the surface temperature measurement without influencing the core or deep body temperature.

In contrast, core or “deep” body temperature measurements require additional set up time and are minimally invasive but provide a more accurate representation of the body temperature.

 Two of the most prevalent core temperature measurement sites used during MRI procedures are the rectum and esophagus.

 measurements are highly accurate and within 0.6oC of the deep body temperature.

 The main drawback to this temperature measurement site is associated with a lag or delay in the temporal response to changing body temperature due to the presence of thermal inertia from the intervening tissues (i.e., between the rectum and hypothalamus). This temporal delay may also be caused by the presence of feces and poor blood supply in the rectum.

 A clinical investigation reported that the rectal temperature substantially lagged in response to changes in body temperature.

 The lack of temporal resolution can expose the patient to a hypothermic or hyperthermic condition for an extended period without being recognized by the clinician. Also, special care must be taken when placing a rectal temperature probe in neonatal or pediatric patient to prevent perforation and infection.

 measurements provide a high level of accuracy and good temporal correlation to body temperature due to the close proximity to the aorta, a deep body site.

 In addition to the accuracy, the temperature recorded in the esophagus is responsive to fluctuations in body temperature and readily tracks changes compared to rectal or surface temperature measurement sites.

 The only caveat is that the accuracy of measuring temperature in the esophagus is directly linked to the proper positioning of the probe.

 Airflow in the trachea can impact the measured temperature if the probe is not inserted deep enough into the esophagus. The recommended placement of the sensor is in the lower one-third of the esophagus for an accurate core temperature measurement.

Table 2 presents a comparison of the measurement sites to monitor during MRI, with the advantages and disadvantages.

Table 2 Comparison of the measurement sites for temperature monitoring during MRI

Monitoring Body Temperature During MRI: Recommendations

In consideration of the available temperature measurement sites that may be monitored during MRI, especially with regard to which site provides the most accurate information along with the best temporal resolution, the temperature of the esophagus will provide the most acceptable and clinically relevant information. Furthermore, esophageal temperature is insensitive to ambient air circulation and patient perspiration during the MRI examination and has the added benefit of fast response time to temperature fluctuations in the body compared to the measurement of temperature in the rectum. The current availability of temperature probes and recording equipment properly designed for use in the MRI setting permits the monitoring of body temperature in the esophagus, which provides physiologic information that is vital to patient care.

Shellock is adjunct clinical professor of radiology and medicine at the Keck School of Medicine, University of Southern California. He is also director for MRI Studies of Biomimetic MicroElectronic Systems at the National Science Foundation, Engineering Research Center, University of Southern California. 


(1) Schulte-Uentrop L, Goepfert MS. Anaesthesia or sedation for MRI in children. Curr Opin Anaesthesiol. 2010;23:513-7.
(2) Watchel RE, Dexter F, Dow AJ. Growth rates in pediatric diagnostic imaging and sedation. Anesthesia and Analgesia 2009;108:1616-1621.
(3) Shellock FG. Chapter 11, Patient Monitoring in the MRI Environment. In: Magnetic Resonance Procedures: Health Effects and Safety. CRC Press, Boca Raton, FL, 2001, pp. 217-241.
(4) Kanal E, Shellock, FG. Patient monitoring during clinical MR imaging. Radiology 1992;185:623.
(5) Practice Advisory on Anesthetic Care for Magnetic Resonance Imaging, Anesthesiology 2009;110:459–79
(6) Standards For Basic Anesthetic Monitoring (Approved By The ASA House Of Delegates on October 21, 1986, And Last Amended On October 25, 2005)
(7) Holshouser, B., Hinshaw, D. B., and Shellock, F. G. Sedation, anesthesia, and physiologic monitoring during MRI. J Magn Reson Imaging 1993;3:553-558.
(8) American Academy of Pediatrics; American Academy of Pediatric Dentistry, Cote CJ, Wilson S; Work Group on Sedation. Guidelines for monitoring and management of pediatric patients during and after sedation for diagnostic and therapeutic procedures: an update. Pediatrics. 2006;118:2587-602.
(9) Kanal E, Barkovich AJ, Bell C, et al. ACR guidance document for safe MR practices: 2007. AJR Am J Roentgenol. 2007;188:1447-1474.
(10) American College of Radiology, ACR standard for the use of intravenous conscious sedation, and ACR standard for pediatric sedation/analgesia. In, 1998 ACR Standards, Reston, VA, American College of Radiology 1998; pp. 123.
(11) Kanal E, Shellock, FG. Policies, guidelines, and recommendations for MR imaging safety and patient management. Patient monitoring during MR examinations. J Magn Reson Imaging 1992;2:247.
(12) Joint Commission on Accreditation of Healthcare Organizations. Sedation and anesthesia care standards. Oakbrook Terrace, IL: Joint Commission on Accreditation of Healthcare Organizations, 2003.
(13) Dalal PG, Murray D, Cox T, McAllister J, Snider R. Sedation and anesthesia protocols used for magnetic resonance imaging studies in infants: provider and pharmacologic considerations. Anesth Analg. 2006;103:863-8.
(14) Knies RC. Temperature Measurement in Acute Care: The Who, What, Where, When, Why, and How? Web Article http://enw.org/Research-Thermometry.htm (Accessed June 24, 2011)
(15) Michiaki Y. Anesthesia and Body Temperature: Temperature Regulation under General Anesthesia Combined with Epidural Anesthesia. Journal of Clinical Anesthesia 2000; 24:1416-1424.
(16) Takashi M; Anesthesia and Body Temperature: General Anesthesia and Thermoregulation. Journal of Clinical Anesthesia 2000; 24:1408-1415.
(17) Schubert A. Side Effects of Mild Hypothermia. Journal or Neurological Anesthesiology 1995, Vol 7, No. 2, Page 139-147
(18) Lilly JK, Boland JP, Zekan S. Urinary Bladder temperature Monitoring: A new Index of Body Core Temperatures, Critical Care Medicine 1980, 8(12):742-744
(19) Lefrant J –Y, Muller L, Emmanuel Coussaye J, Benbabaali M, Lebris C, Zeitoun N, Mari, C, Saissi G, Ripart J, Eledjam J –J. Temperature Measurement in intensive care patients: comparison of urinary bladder, esophageal, rectal, axillary, and inguinal methods versus pulmonary artery core method. Intensive care Med 2003; 29:414-418 .
(20) Robinson J, Charlton J, Seal R, Spady D, Joffres MR. Esophageal, rectal, axillary, tympanic, and pulmonary artery temperatures during cardiac surgery. Canadian Journal of Anesthesiology 1998;45:317-323.
(21) Takashi A. Anesthesia and Body Temperature: interoperative monitoring of body temperature and its significance. Journal of Clinical Anesthesia, 2000;24:1432-1443.
(22) Shellock FG, Rubin SA. Simplified and highly accurate core temperature measurements. Med Prog Technol.1982;8:187-8.
(23) Gooden CK. Anesthesia for magnetic resonance imaging. Curr Opin Anaesthesiol. 2004;17:339-42.
(24) Wilson TE, Sauder CL, Kearney ML, Kuipers NT, Leuenberger UA, Monahan KD, Tay CA. Skin surface cooling elicits peripheral and visceral vasoconstriction in humans. Journal of Applied Physiology 2007;103:1257-1262.
(25) Newsham KR, Saunders JE, Nordin ES. Comparison of rectal and tympanic thermometry: Discussion. Southern Medical Journal 2002; 95, 804-810

Articles

MRI Safety: Monitoring Body Temperature During MRI

 approval from the FDA, which for the first time allows MRI procedures to be performed in patients by following specific labeling requirements. http://www.medtronic.com/mrisurescan. The “MR Conditional” Revo MRI SureScan Pacing System from Minneapolis-based Medtronic Inc. was designed to 

 with the electromagnetic fields used during MRI examinations.

Comprehensive labeling information must be reviewed and adhered to ensure patient safety, and includes, but is not limited to, the following:


A complete SureScan pacing system including a Revo MRI SureScan IPG and two SureScan leads is required for use in the MRI environment. Any other combination may result in a hazard to the patient during an MRI scan. The SureScan feature must be programmed to “on” prior to scanning a patient according to the specified conditions for use.

Clinical and pre-clinical testing has demonstrated that the SureScan pacing system is safe for use in the MRI environment when used according to the instructions in the Revo MRI SureScan Pacing System technical manual.

The SureScan pacing system can be scanned in patients under the following conditions:

1. Horizontal, cylindrical bore magnet, clinical MRI systems with a static magnetic field of 1.5 T must be used.

2. Gradient systems with maximum gradient slew rate performance per axis of ≤ 200 Tesla per meter per second (T/m/s) must be used.

3. The scanner must be in the “Normal Operating Mode.”
• Whole body averaged specific absorption rate (SAR) as reported by the MRI equipment must be ≤ 2.0 Watts per kilogram (W/kg).
• The head SAR must be < 3.2 W/kg.

4. The patient must be positioned within the bore such that the isocenter (center of the MRI bore) is superior to the C1 vertebra or inferior to the T12 vertebra.

5. Proper patient monitoring must be provided during the MRI scan. The methods include visual and verbal contact with the patient, electrocardiography, and pulse oximetry (plethysmography).

6. Patients and their implanted systems must be screened to meet the following requirements:
• no previously implanted (active or abandoned) medical devices, leads, lead extenders, or lead adaptors
• no broken leads or leads with intermittent electrical contact as confirmed by lead impedance history
• a SureScan pacing system that has been implanted for a minimum of six weeks
• a SureScan pacing system implanted the left or right pectoral region
• pacing capture threshold values of ≤ 2.0 volts (V) at a pulse width of 0.4 milliseconds (ms)
• a lead impedance value of ≥ 200 ohms (Î©) or ≤ 1500 Î©
• no diaphragmatic stimulation at a pacing output of 5.0 V and at a pulse width of 1.0 ms in patients whose device will be programmed to an asynchronous pacing mode when MRI SureScan is on

7. A health professional who has completed cardiology SureScan training must be present during the programming of the SureScan feature.

8. A health professional who has completed radiology SureScan training must be present during the MRI scan.

9. The implanted system must consist solely of a SureScan device and SureScan leads. Any other combination may result in a hazard to the patient during MRI scans.

. MRI healthcare professionals are advised to contact the respective manufacturer in order to obtain the latest safety information to ensure patient safety relative to the use of an MRI procedure.

Instructions for Use, SURESCAN MRI procedural information for Revo MRI SureScan RVDR01, CapSureFix MRI 5086MRI, Medtronic, Inc., Minneapolis, MN

Shellock FG, Woods TO, Crues JV 3rd. MR labeling information for implants and devices: explanation of terminology. Radiology 2009;253:26-30

Sutton R, Kanal E, Wilkoff BL, et al. Safety of magnetic resonance imaging of patients with a new Medtronic EnRhythm MRI SureScan pacing system: clinical study design. Trials. 2008;2;9:68.

Wilkoff BL, Bello D, Taborsky M, et al. Magnetic resonance imaging in patients with a pacemaker system designed for the magnetic resonance environment. EnRhythm MRI SureScan Pacing System Study Investigators.
Heart Rhythm. 2011;8:65-73

On February 8, 2011, a new cardiac pacemaker received approval from the FDA, which for the first time allows MRI procedures to be performed in patients by following specific labeling requirements. http://www.medtronic.com/mrisurescan. The “MR Conditional” Revo MRI SureScan Pacing System from Minneapolis-based Medtronic Inc. was designed to minimize the potential interactions with the electromagnetic fields used during MRI examinations.

MRI Safety: New Cardiac Pacemaker System Now Available in the U.S.

An insulin pump allows the replacement of slow-acting insulin for basal needs with a continuous infusion of rapid-acting insulin. By using an insulin pump, a patient can typically match the dosage of insulin to lifestyle and activities, rather than adjusting those to the body’s response to insulin injections. The advantages of using an insulin pump include the fact that an insulin pump replaces the need for periodic injections by delivering rapid-acting insulin continuously throughout the day via a catheter. It greatly simplifies the management of diabetes. 

 There are two basic types of insulin pumps, one is an external device and the other is implanted. Both types currently pose hazards to patients referred for MRI procedures. For an external insulin pump, it may simply need to be removed and kept out of the MR environment to ensure there is no adverse impact on the device’s functionality. 

 The information below provides MRI labeling for several of the most commonly used insulin pumps.

This MRI information pertains to the following insulin pumps from Animas, a Johnson & Johnson company: 

Each of the insulin pumps listed above should be kept from exposure to very strong electromagnetic fields, such as MRIs, radiofrequency welders, or magnets used to pick up automobiles. Very strong magnetic fields, such as those associated with MRI, can magnetize the portion of the pump’s motor that regulates insulin delivery and thus damage the device. 



: If you plan to undergo an MRI, remove the insulin pump beforehand and keep it outside of the MR room during the procedure. If the pump is accidentally allowed into the MR system room, disconnect the pump immediately and contact Animas Pump Support for important instructions. 



: Do not bring the insulin pump near the MR system at any time. If the pump is accidentally allowed into the MR system room, disconnect the pump immediately and contact Animas Pump Support for important instructions.

The user manual for the Cozmo Pump (Deltec, St. Paul, MN), states the following regarding MRI: 
 “Caution: Avoid strong electromagnetic fields, like those present with magnetic resonance imaging (MRI) and direct x-ray, as they can affect how the pump works. If you cannot avoid them, you must take the pump off.”

MiniMed 2007 Implantable Insulin Pump System


 The Medtronic MiniMed 2007 Implantable Insulin Pump System (Medtronic MiniMed, Northridge, CA) may offer treatment advantages for diabetes patients who have difficulty maintaining consistent glycemic control. Patients who have not responded well to intensive insulin therapy, including multiple daily insulin injections or continuous subcutaneous insulin infusion using an external pump, may be primary candidates for the Medtronic MiniMed 2007 System. The implanted device delivers insulin into the peritoneal cavity in short, frequent bursts or pulses, similar to how pancreatic beta cells secrete insulin. 

 The Medtronic MiniMed 2007 Implantable Insulin Pump is designed to withstand common electrostatic and electromagnetic interference but must be removed prior to undergoing an MR procedure. Any magnetic field exceeding 600 gauss will interfere with the proper functioning of the pump for as long as the pump remains in that field. Fields much higher than that, such as those emitted by an MR system, may cause irreparable damage to the pump. 

 By comparison, infusion sets (MMT-11X, MMT-31X, MMT-32X, MMT-37X, MMT-39X) used with this device contain no metallic components, thus are safe to be used and can remain attached to the patient during an MR procedure. The only exceptions would be Polyfin infusion sets. Polyfin infusion sets (MMT-106 AND MMT-107, MMT-16X, MMT-30X, MMT-36X) have a surgical steel needle that remains in the subcutaneous tissue. These infusion sets should be removed prior to any MR procedure. 



MiniMed Paradigm REAL-Time Insulin Pump and Continuous Glucose Monitoring System (522 and 722 Insulin Pumps) 

MRI Information for Patients re: magnetic fields:

 Do not use pump cases that have a magnetic clasp. Do not expose your insulin pump to MRI equipment or other devices that generate very strong magnetic fields. 

 Magnetic fields in the immediate vicinity of such equipment can damage the part of the pump’s motor that regulates insulin delivery, possibly resulting in overdelivery and severe hypoglycemia. Your pump must be removed and kept outside the room during magnetic resonance imaging (MRI) procedures. 

 If your pump is inadvertently exposed to a strong magnetic field, discontinue use and contact your local help line or representative for further assistance. 

 The insulin pump, transmitter, and sensor must be removed prior to entering the MRI environment.

The DANA Diabecare IIS Insulin Pump and DANA Diabecare Insulin Infusion Pump (SOOIL Development, San Diego)

 must not be used in the presence of intense electromagnetic fields, such as those generated by certain electrically powered medical devices. The pump should be removed prior to the user having a CT scan, MRI, or x-ray. (MRI healthcare professionals are advised to contact the respective manufacturer for the latest safety information to ensure patient safety relative to use of the device during an MR procedure.) 



Dr. Shellock is adjunct clinical professor of radiology and medicine at the Keck School of Medicine, University of Southern California. He is also director for MRI Studies of Biomimetic MicroElectronic Systems at the National Science Foundation, Engineering Research Center, University of Southern California. 

 http://www.animascorp.com/products/pr_userguide.shtml

http://www.diabetes.org/living-with-diabetes/treatment-and-care/medication/insulin/insulin-pumps.html

An insulin pump allows the replacement of slow-acting insulin for basal needs with a continuous infusion of rapid-acting insulin. By using an insulin pump, a patient can typically match the dosage of insulin to lifestyle and activities, rather than adjusting those to the body’s response to insulin injections. The advantages of using an insulin pump include the fact that an insulin pump replaces the need for periodic injections by delivering rapid-acting insulin continuously throughout the day via a catheter. It greatly simplifies the management of diabetes.

MRI safety: Patients with insulin pumps require special cautions

A pessary is a small medical device or form of pharmaceutical preparation that is inserted into the vagina or rectum and held in place by the pelvic floor musculature. In some instances, a pessary may contain metal that allows it to be shaped to facilitate proper retention. 

Typically, the pessary is a firm ring or similar structure that presses against the wall of the vagina and urethra to help reduce urinary leakage or another condition. It is an effective nonsurgical means of managing a number of gynecologic problems. Indications for the pessary include pelvic support defects such as uterine prolapse and vaginal prolapse, as well as stress urinary incontinence.

A wide variety of pessary styles exist, including those made entirely from nonmetallic, nonconducting materials (e.g., plastic, silicone, or latex) as well as those that have metallic components. Obviously, those pessaries made from nonmetallic, nonconducting materials pose no problems for patients undergoing MRI procedures. 





However, pessaries that have metallic components will cause substantial artifacts, as shown in Figure 1. To date, there are no reports of injuries or other issues related to performing MRI in patients with these devices.

Brubacker L. The vaginal pessary. In: Friedman AJ, ed. 

American Urogynecologic Society quarterly report

, 1991;9(3). 

Davila GW. Vaginal prolapse: management with nonsurgical techniques. Postgrad Med 1996;99:171-176,181,184-185. 

Deger RB, Menzin AW, Mikuta JJ. The vaginal pessary: past and present. Postgrad Obstet Gynecol 1993;13:1-8. 

Komesu YM, Ketai LH, Rogers RG, et al. Restoration of continence by pessaries: magnetic resonance imaging assessment of mechanism of action. Am J Obstet Gynecol 2008;198(5):563.e1-6. 

Miller DS. Contemporary use of the pessary. In: Sciarra JJ, ed. 

, revised 1997 ed. Philadelphia: Lippencott-Raven, 1997:1-12. 

Shellock FG. 

Reference manual and for magnetic resonance safety, implants and devices: 2009 edition

. Los Angeles: Biomedical Research Publishing Group, 2009; www.MRIsafetybook.com

Zeitlin MP, Lebherz TB. Pessaries in the geriatric patient. J Am Geriatr Soc 1992;40:635-639. 



Frank G. Shellock, Ph.D., is an adjunct clinical professor of radiology and medicine at the Keck School of Medicine, University of Southern California. He is also the director of MRI studies at the Biomimetic Microelectronic Systems, National Science Foundation - Engineering Research Center, USC, the founder of the Institute for Magnetic Resonance Safety, Education, and Research (www.imrser.org), and president of Shellock R&D Services.

A pessary is a small medical device or form of pharmaceutical preparation that is inserted into the vagina or rectum and held in place by the pelvic floor musculature.

Frank G. Shellock, PhD, FACC, FACSM

Articles

MRI Safety: Monitoring Body Temperature During MRI

MRI Safety: New Cardiac Pacemaker System Now Available in the U.S.

MRI safety: Patients with insulin pumps require special cautions

Conductive elements in implantable device degrade MR image quality