TY - JOUR
T1 - Absolute temperature monitoring using RF radiometry in the MRI scanner
AU - El-Sharkawy, Abd El Monem M.
AU - Sotiriadis, Paul P.
AU - Bottomley, Paul A.
AU - Atalar, Ergin
N1 - Funding Information:
Manuscript received December 15, 2005; revised August 21, 2006. This work was supported by the National Institute of Health (NIH) under Grant R01HL57483 and Grant R01RR15396. This paper was recommended by Guest Editor A. G. Andreou.
PY - 2006/11
Y1 - 2006/11
N2 - 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.
AB - 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.
KW - Automatic matching and tuning
KW - Magnetic resonance imaging (MRI)
KW - Microwave radiometry
KW - Temperature measurement
KW - Thermography
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U2 - 10.1109/TCSI.2006.884423
DO - 10.1109/TCSI.2006.884423
M3 - Article
C2 - 18026562
AN - SCOPUS:34548856556
SN - 1057-7122
VL - 53
SP - 2396
EP - 2404
JO - IEEE Transactions on Circuits and Systems I: Regular Papers
JF - IEEE Transactions on Circuits and Systems I: Regular Papers
IS - 11
ER -