Diagnostic confirmation of cancer in solid organs is based on biopsy findings. In a standard 12-core prostate biopsy protocol, conventional biopsy needles sample only 0.95% (∼0.228 cm³) of a typical 24-cm³ prostate gland. The primary objective of this study was to enhance the sensitivity of standard biopsy protocol by gauging electrical properties of tissue simultaneously with tissue extraction for histopathology analysis. A conventional biopsy (Bx) needle was instrumented with an electrical impedance spectroscopy (EIS) sensor to interrogate the tissue volume surrounding the needle tip. The EIS-Bx device was evaluated in a series of saline bath and ex vivo porcine experiments. It was found to sense a volume of 0.286 cm³ of tissue around the needle tip. EIS measurements were recorded from three ex vivo human prostates using the device, and the extracted biopsy cores were histologically assessed. Prostate conductivity σ ranged from 0.179 to 0.3310 S/m for benign tissues and 0.0746 to 0.0837 S/m for malignant tissues at frequencies ranging from 1 to 100 kHz. Relative permittivity ϵ(r) ranged from 2.10×10⁶ to 2.9 × 10⁴ for benign and 6.63×10⁵ to 5.3 × 10³ for cancer tissues over the same frequency range. Both are found to be significantly higher in normal prostate tissues than in malignant tissue (p< 0.00001).

Two experiments studied the frequency pattern of TLS (temporary loudness shift) as a function of the level and frequency of the fatiguing sound. In experiment 1, the fatiguing tones were intermittent 375-, 1500-, or 3000-Hz tones (10 s on/10 s off) at 75, 80, 85, 90, or 95 dB SPL. The TLS patterns were established for a continuous, 60-phon test tone at different frequencies presented simultaneously with the intermittent fatiguing tone. In experiment 2, a 1000-Hz exposure tone with an intermittency of 10 s on/20 s off was used with a continuous 60-dB test tone at different frequencies. In both experiments, the total exposure duration was 60 s; TLS was measured 5 s after the exposure ended. For the lowest two exposure levels, the TLS pattern had one peak centered on the exposure frequency. As the exposure level increased, a two-peak pattern became evident, with the second peak at higher test frequencies. This finding could be interpreted as psychoacoustical evidence for the double (passive and active) mode of displacement of the basilar membrane. In experiment 2, a TTS (temporary threshold shift) measurement after exposure to a 45-min, 1000-Hz tone at 90 dB was added to the TLS sessions. The correlations between maximum TTS after a 45-min exposure and the TLS obtained after a 60-s exposure were calculated for each of the exposure levels and test frequencies used in TLS measurements. The correlation reached as high as 0.9 for TLSs measured at 1120 Hz after a 90-dB exposure; it was smaller but significant for TLSs at the exposure frequency. Despite these correlations, differences in the overall patterns of TTS and TLS suggest that they stem from two different mechanisms.

Abstract-Electrical impedance was recorded at 21 discrete frequencies (1 to 100 kHz) from 27 ex vivo human prostates. These electrical properties were measured by using custom designed Electrical Impedance Spectroscopy (EIS) sensing biopsy (Bx) needles. EIS-Bx needles gauge the electrical properties of tissue in tandem with the tissue extraction (used for histopathological assessment). The EIS-Bx probe has a signal-tonoise ratio (SNR) of 65 dB across the frequency range (1 kHz to 100 kHz [7]. These contrasts are due to morphological differences present in the different prostatic tissue types. We have developed an electrical impedance spectroscopy (EIS) sensing biopsy (Bx) needle to record bipolar impedance measurements in tandem with tissue core extraction. We have demonstrated that this type of data has the potential to distinguish normal from abnormal tissue across a larger fraction of prostate volume than that sampled during conventional biopsy procedure [8] [9]. We present our most recent analysis of a 27 patient cohort evaluating how well these electrical properties discriminate cancer from non-cancer tissues in the prostate. II. EIS-BX DEVICE OVERVIEWDevice Design A typical biopsy needle is constructed of stainless steel and consists of an inner trocar and an outer cannula. BARD Maxcore Disposable Biopsy Instruments (MC1820, C.R. Bard, Murray Hill, NJ) extract a 22 mm long tissue core and are the standard biopsy needles used for prostate biopsy at our institution. These needles are modified into an EIS-Bx device by electrically isolating the two (inner and outer) needle elements; a thin insulating tube (polyimide) is adhered onto the surface of each of these elements, leaving just the tip of both needles exposed. The tips of inner and outer elements act as two electrodes, through which EIS based bipolar measurements are recoded. The two electrodes are interfaced to an impedance analyzer (HP4284A, Agilent Technologies) through a RCA plug and assembly of coaxial cables. A small current (<1mA) is applied between the tip electrodes. The impedance recorded is the ratio of induced voltage to the applied

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