High-Precision Temperature Measurement System for Magnetic Resonance Imaging
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MEDICAL AND BIOLOGICAL MEASUREMENTS HIGH-PRECISION TEMPERATURE MEASUREMENT SYSTEM FOR MAGNETIC RESONANCE IMAGING D. S. Semenov,1 V. A. Yatseev,2 E. S. Akhmad,1 Yu. A. Vasilev,1 K. A. Sergunova,1 and A. V. Petraikin1
UDC 681.78
To determine the compliance of an implantable medical device with the safety requirements in magnetic resonance imaging, an experimental assessment of the heating of this device during a study is necessary. The use of traditional methods, such as thermocouple measurements or radiation thermometry, is difficult in the conditions of a magnetic resonance imaging room. A spectrometric system for measuring temperature in conditions of a magnetic resonance imaging room is proposed. The developed system has a sensitivity of 0.01°C and an error of 0.1% in the range of 10–50°C. The temperature sensors used in the system are Fabry–Perot interferometers. The design of the sensors and the method of calibration are described. The system was tested in determining the heating of two passive implants during the study in a magnetic resonance imager with a magnetic field induction of 1.5 T. The compliance of the developed system with the recommendations adopted in magnetic resonance imaging for evaluating the heating of implantable medical devices is demonstrated. The temperature value obtained is comparable with the value found during testing of this implant according to ASTM F 2182. The presented measuring system can be used to assess the magnetic resonance compatibility of implantable medical devices, to develop scanning protocols for patients with metal structures, as well as to confirm or refine mathematical models of heat transfer. Keywords: magnetic resonance imaging, heating in an electromagnetic field, temperature measurement, fiber optic systems, Fabry–Perot sensor, broadband interferometry, implantable medical devices.
Introduction. Magnetic resonance imaging (MRI) is one of the most widespread methods of medical imaging. Unlike other x-ray methods, this method does not involve patient radiation exposure. However, constant and variable electromagnetic fields lead to the emergence of certain risk factors, including thermal response of tissues. The first data on tissue heating during magnetic resonance were published in the 1980s, however, the performed experiments mainly related to localized temperature changes [1]. A significant contribution to the description of the effects of electromagnetic fields of MRI was made by Shellock [2–4]. Heating of implantable medical devices due to the occurrence of currents in them, which appear as a result of interaction with alternating magnetic fields, is an important factor to consider for ensuring safety. The International Electrotechnical Commission (IEC) has developed MRI safety requirements currently in force in Russia as GOST MEK 60601-2-33, “Medical Electrical Equipment. Part 2-33. Particular Safety Requirements Taking into Account the Basic Functional Characteristics of Medical Diagnostic Equipment Operating on the Basis of Magnetic Resonance,” and limi
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