A. Hartov et al., A multichannel continuously selectable multifrequency electrical impedancespectroscopy measurement system, IEEE BIOMED, 47(1), 2000, pp. 49-58
There is increasing evidence that alterations in the electrical property sp
ectrum of tissues below 10 MHz is diagnostic for tissue pathology and/or pa
thophysiology. Yet, the complexity associated with constructing a high-fide
lity multichannel, multifrequency data acquisition instrument has Limited w
idespread development of spectroscopic electrical impedance imaging concept
s. To contribute to the relatively sparse experience with multichannel spec
troscopy systems this paper reports on the design, realization and evaluati
on of a prototype 32-channel instrument. The salient features of the system
include a continuously selectable driving frequency up to 1 MHz, either vo
ltage or current source modes of operation and simultaneous measurement of
both voltage and current on each channel in either of these driving configu
rations. Comparisons of performance with recently reported fixed-frequency
systems is favorable. Volts dc (VDC) signal-to-noise ratios of 75-80 dB are
achieved and the noise floor for ac signals is near 100 dB below the signa
l strength of interest at 10 kHz and 60 dB down at 1 MHz. The added benefit
of being able to record multispectral information on source and sense sign
al amplitudes and phases has also been realized. Phase-sensitive detection
schemes and multiperiod undersampling techniques have been deployed to ensu
re measurement fidelity over the full bandwidth of system operation.