Performance Validation of a Modified Magnetic Resonance Imaging–Compatible Temperature Probe in Children Viviane G. Nasr, MD, Roman Schumann, MD, Iwona Bonney, PhD, Lina Diaz, MD, and Iqbal Ahmed, MD, FRCA INTRODUCTION: During magnetic resonance imaging (MRI), children are at risk for body temperature variations. The cold MRI environment that preserves the MRI magnet can cause serious hypothermia. On the other hand, hyperthermia may also develop because of radiofrequency-induced heating of the tissues, particularly in prolonged examinations. Because of a lack of MRI-compatible core temperature probes, temperature assessment is unreliable, and specific absorption rate–related patient heat gain must be calculated to determine the allowable scan duration. We compared an MRI-compatible temperature probe and a modification thereof to a standard esophageal core body temperature probe in children. METHODS: Children undergoing general anesthesia were recruited, each patient serving as his/her own control. Core body temperature was measured using 3 different devices: (1) a fiberoptic MRI-compatible skin surface temperature probe (MRI-skin) located on the child’s skin surface; (2) a fiberoptic MRI-compatible temperature probe modified with a single-use sleeve at the tip (MRI-core), located in the nasopharynx; and (3) a standard temperature monitor (STRD) located in the esophagus or nasopharynx. The Bland–Altman method was used for statistical analysis. RESULTS: We enrolled 60 children aged 7.8  6 years (mean  SD) weighing 32.4 (26.4) kg. The estimated difference between the STRD and MRI-core measurements of core temperature was 0.06°C (confidence interval [CI]: -0.02, 0.15), and between the STRD and the MRI-skin 1.19°C (CI: 0.97, 1.41). According to the Bland–Altman analysis, the 95% limits of agreement ranged from -0.9 to 3.4 and from -1.3 to 1.2 between the STRD and the MRI-skin probe and the MRI-core probe, respectively. DISCUSSION: Our results show good agreement between standard esophageal measure- ments of core temperature and core temperature measured using a modified MRI-core probe during general anesthesia in a general surgical pediatric population. The ability to accurately assess core temperature in the MRI suite may safely allow longer scan times and therefore reduce repeat anesthetic exposure, improve patient safety, and enhance the quality of care in children. (Anesth Analg 2012;114:1230 –4) T he number of children undergoing magnetic reso- nance imaging (MRI) is increasing in recent years, especially with the additional relevance of cardiac MRI for congenital heart diseases. 1 During MRI, patients are at risk of hypo- as well as hyperthermia, but core body temperature monitoring has not been possible for lack of user-friendly, reliable MRI-compatible tempera- ture probes. 2–6 Children seldom tolerate the cold, noisy MRI environment combined with the requirement for immobility for prolonged periods of time and breath holding. Often deep sedation or general anesthesia is needed. Sedation techniques, including general anesthe- sia, impair thermoregulation, leaving patients at risk for hypothermia. 7 In addition, active warming devices are not yet MRI compatible. At other times the MRI’s radiofrequency energy can warm body tissue, causing hyperthermia. 8,9 A safety stan- dard with respect to the duration of MRI allowed has been added recently by the International Electrotechnical Com- mission as long-duration patient imaging sequences have become more common. a,10 The maximum allowed specific absorbed energy is 14.4 kJ/kg (240 W/min/kg) per exami- nation. As a safety feature, MR scanners will cease scanner operation if the predicted absorbed energy exceeds the acceptable limit for the patient being scanned. As a conse- quence, some patients may need additional MRI examina- tions under anesthesia to complete the needed workup. Accurate core body temperature assessment during MRI could eliminate repeat examinations, reduce anesthetic exposure, and greatly improve a child’s safety by detecting either hypothermia or hyperthermia. We conducted this study to evaluate a current MRI- compatible skin surface temperature probe and a modifica- tion of this probe that allows nasopharyngeal or esophageal placement. We validated both devices against a standard From the Department of Anesthesiology, Tufts Medical Center, Boston, Massachusetts. Accepted for publication January 4, 2012. Lina Diaz is currently affiliated with the Massachusetts Eye and Ear Center, Boston, Massachusetts. Funding: Department of Anesthesiology. The manuscript was supported by grant no. UL1 RR025752 from the National Center for Research Resources (NCRR). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NCRR. The authors declare no conflict of interest. Reprints will not be available from the authors. This report was previously presented, in part, at the SPA 2010. Address correspondence to Viviane G. Nasr, MD, Department of Anesthesiol- ogy, Tufts Medical Center, 800 Washington Street, Box #298, Boston, MA 02111. Address e-mail to vnasr@tuftsmedicalcenter.org. Copyright © 2012 International Anesthesia Research Society DOI: 10.1213/ANE.0b013e31824b003e a International Electrotechnical Commission. Medical electrical equipment. Part 2–33. Particular requirements for the safety of magnetic resonance equipment for medical diagnosis. Geneva, Switzerland: International Elec- trotechnical Commission, 2010. 1230 www.anesthesia-analgesia.org June 2012 • Volume 114 • Number 6