Absolute temperature monitoring using RF radiometry in the MRI scanner

Abd El Monem M. El-Sharkawy, Paul P. Sotiriadis, Paul A. Bottomley, Ergin Atalar

Research output: Contribution to journalArticlepeer-review

Abstract

Temperature detection using microwave radiometry has proven value for noninvasively measuring the absolute temperature of tissues inside the body. However, current clinical radiometers operate in the gigahertz range, which limits their depth of penetration. We have designed and built a noninvasive radiometer which operates at radio frequencies (64 MHz) with ∼100-kHz bandwidth, using an external RF loop coil as a thermal detector. The core of the radiometer is an accurate impedance measurement and automatic matching circuit of 0.05 Ω accuracy to compensate for any load variations. The radiometer permits temperature measurements with accuracy of ±0.1°K, over a tested physiological range of 28°C-40 °C in saline phantoms whose electric properties match those of tissue. Because 1.5 T magnetic resonance imaging (MRI) scanners also operate at 64 MHz, we demonstrate the feasibility of integrating our radiometer with an MRI scanner to monitor RF power deposition and temperature dosimetry, obtaining coarse, spatially resolved, absolute thermal maps in the physiological range. We conclude that RF radiometry offers promise as a direct, noninvasive method of monitoring tissue heating during MRI studies and thereby providing an independent means of verifying patient-safe operation. Other potential applications include titration of hyper- and hypo-therapies.

Original languageEnglish (US)
Pages (from-to)2396-2404
Number of pages9
JournalIEEE Transactions on Circuits and Systems I: Regular Papers
Volume53
Issue number11
DOIs
StatePublished - Nov 2006

Keywords

  • Automatic matching and tuning
  • Magnetic resonance imaging (MRI)
  • Microwave radiometry
  • Temperature measurement
  • Thermography

ASJC Scopus subject areas

  • Electrical and Electronic Engineering

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