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Using electrical impedance spectroscopy (EIS) technology to detect breast abnormalities in general and cancer
in particular has been attracting research interests for decades. Large clinical tests suggest that current EIS systems can
achieve high specificity (≥ 90%) at a relatively low sensitivity ranging from 15% to 35%. In this study, we explore a new
resonance frequency based electrical impedance spectroscopy (REIS) technology to measure breast tissue EIS signals in
vivo, which aims to be more sensitive to small tissue changes. Through collaboration between our imaging research
group and a commercial company, a unique prototype REIS system has been assembled and preliminary signal
acquisition has commenced. This REIS system has two detection probes mounted in the two ends of a Y-shape support
device with probe separation of 60 mm. During REIS measurement, one probe touches the nipple and the other touches
to an outer point of the breast. The electronic system continuously generates sweeps of multi-frequency electrical pulses
ranging from 100 to 4100 kHz. The maximum electric voltage and the current applied to the probes are 1.5V and 30mA,
respectively. Once a "record" command is entered, multi-frequency sweeps are recorded every 12 seconds until the
program receives a "stop recording" command. In our imaging center, we have collected REIS measurements from 150
women under an IRB approved protocol. The database includes 58 biopsy cases, 78 screening negative cases, and other
"recalled" cases (for additional imaging procedures). We measured eight signal features from the effective REIS sweep
of each breast. We applied a multi-feature based artificial neural network (ANN) to classify between "biopsy" and
normal "non-biopsy" breasts. The ANN performance is evaluated using a leave-one-out validation method and ROC
analysis. We conducted two experiments. The first experiment attempted to classify 58 "biopsy" breasts and 58 "non-biopsy"
breasts acquired on 58 women each having one breast recommended for biopsy. The second experiment
attempted to classify 58 "biopsy" breasts and 58 negative breasts from the set of screening negative cases. The areas
under ROC curves are 0.679 ± 0.033 and 0.606 ± 0.035 for the first and the second experiment, respectively. The
preliminary results demonstrate (1) even with this rudimentary system with only one paired probes there is a measurable
signal of changes in breast tissue demonstrating the feasibility of applying REIS technology for identifying at least some
women with highly suspicious breast abnormalities and (2) the electromagnetic asymmetry between two breasts may be
more sensitive in detecting changes in the abnormal breast. To further improve the REIS system performance, we are
currently designing a new REIS system with multiple electrical probes and a more sophisticated analysis scheme.
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