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KMID : 1137820070280010084
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의공학회지
2007 Volume.28 No. 1 p.84 ~ p.94
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320-Channel Multi-Frequency Trans-Admittance Scanner(TAS) for Anomaly Detection
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Oh Tong-In
Lee Min-Hyoung
Kim Hee-Jin
Woo Eung-Je
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Abstract
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In order to collect information on local distribution of conductivity and permittivity underneath a scan probe, we developed a multi-frequency trans-admittance scanner (TAS). Applying a sinusoidal voltage with variable frequency on a chosen distal part of a human body, we measure exit currents from 320 grounded electrodes placed on a chosen surface of the subject. The electrodes are packaged inside a small and light scan probe. The system includes one voltage source and 17 digital ammeters. Front-end of each ammeter is a current-to-voltage converter with virtual grounding of a chosen electrode. The rest of the ammeter is a voltmeter performing digital phase-sensitive demodulation. Using resistor loads, we calibrate the system including the scan probe to compensate frequency-dependent variability of current measurements and also inter-channel variability among multiple. We found that SNR of each ammeter is about 85dB and the minimal measurable current is 5nA. Using saline phantoms with objects made from TX-151, we verified the performance of the lesion estimation algorithm. The error rate of the depth estimation was about 19.7%. For the size estimate, the error rate was about 15.3%. The results suggest improvement in lesion estimation algorithm based on multi-frequency trans-admittance data.
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KEYWORD
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multi-frequency, TAS (trans-admittance scanner), conductivity, permittivity, lesion estimation algorithm
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