Highly sensitive magnetic resonance compatible temperature measurement system

Abstract

One of the steps in determining the compliance of an implantable medical device with the safety requirements in magnetic resonance imaging (MRI) is the experimental assessment of its heating over the course of the study. However, the application of traditional methods, such as thermocouple measurements or radiation thermometry, is difficult in connection with the conditions of high magnetic fields. A spectrometric system is proposed for measuring temperature in a magnetic resonance imaging cabinet with sensitivity of 0.01 °C and error of 0.1 % in the range of 10–50 °C. Temperature sensors are Fabry–Perot interferometers formed by flat ends of optical fibers located at a distance of about tens of micrometers. A design of the sensor and a calibration method are described. A design of the sensor and a calibration method are described. The system was tested in the process of two passive implants heating in 1,5 T MRI. As a result, compliance with the accepted recommendations for assessing the heating of implantable medical devices in MRI was demonstrated, and the temperature rise value was obtained that was comparable to the manufacturer’s tests of this product according to ASTM F 2182. The presented measurement system can be used to assess the MR-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.