RF radiometery sensor sensitivity and detection profile

Abstract

Temperature sensing using microwave radiometry has proven value for non-invasively measuring the absolute temperature of tissues inside the human body. However, current clinical radiometers operate in GHz or infrared frequency ranges; this limits their depth of penetration since the human body is not "transparent" at these frequencies. To address this problem, we have previously designed and built an advanced, near-field radiometer operating at VHF frequencies (64MHz) with a ~100 KHz bandwidth. The radiometer has performed accurate temperature measurements to within ±0.1º C, over a tested physiological range of 28-40º C in saline phantoms whose electric properties match those of human tissue. In this work we analyze radiofrequency (RF) coil designs suitable for RF Radiometry. We investigate the coil profile sensitivity to look where temperature information is coming from and the depth of penetration associated with the receiver used. We also look into the virtues of using multi-turn coils versus single loop coils. We conclude that by using multi-turn coils the received noise signal is more sensitive to sample noise and temperature can be estimated more accurately especially with the use of smaller receivers.