Prostate Cancer Detection Using Composite Impedance Metric

Abstract

Prostate cancer (PCa) recurrences are often predicted by assessing the status of surgical margins (SM) – positive surgical margins (PSM) increase the chances of biochemical recurrence by 2–4 times which may lead to PCa recurrence. To this end, an electrical impedance acquisition system with a microendoscopic probe was employed in an ex-vivo study of human prostates. This system measures the tissue bioimpedance over a range of frequencies (1 kHz to 1MHz), and computes a number of Composite Impedance Metrics (CIM). A classifier trained using CIM data can be used to classify tissue as benign or cancerous. The system was used to collect the impedance spectra from 14 excised prostates, which were obtained from men undergoing radical prostatectomy, for a total of 23 cancerous and 53 benign measurements. The data revealed statistically significant (p<0.05) differences in the impedance properties of the benign and tumorous tissues, and among the measurements taken on the apical, base, and lateral surface of the prostate. Further, in the leave-one-patient-out cross validation, a maximum predictive accuracy of 90.79% was achieved by combining high frequency CIM phase data to train a support vector machine classifier with a radial basis function kernel. The observations are consistent with the physiology and morphology of benign and malignant prostate tissue. CIMs were found to be an effective tool in distinguishing benign from cancerous tissues.

Comparative study of separation betweenex vivoprostatic malignant and benign tissue using electrical impedance spectroscopy and electrical impedance tomography

“…In comparison to our prior study (Khan et al 2016), the clinical parameters are quite similar, but here we have significantly improved registration between impedance measurements, yielding a more nuanced analysis on accuracy as a function of percent cancer. Overall, the results presented in this paper corroborate our previous studies and present the strongest evidence yet that an intraoperative-capable impedance probe can be used to distinguish benign from malignant prostate tissues.…”

“…6/9 and 9/6) to give a total of 16 impedance measurements per ring. A noise filter applied to the data removes patterns whose 1) voltage difference is too small (< 50 mV), 2) voltage or current noise power is too large (> 2 V and > 3/(499 Ω) A for voltage and current, respectively; see (Khan et al 2016) for description of noise power measurements in this system and note that 499 Ω is the resistor used on the current sense electrode), and/or 3) if the sensed current magnitude is too small (< 0.1 mA, in voltage drive mode). These thresholds were empirically determined and were conservatively chosen to keep higher quality measurements.…”

“…Based on these studies we have been recently developing SMA EIS/EIT probes. Khan et al reported preliminary results from this effort where a technique called the Composite Impedance Metric (CIM) was used to establish separation between benign and malignant prostatic tissue that had a predictive accuracy of 90.3% using the Support Vector Machine (SVM) algorithm and a best area-under-curve (AUC) from receiver operator characteristic (ROC) analysis of 0.86 (Khan et al 2016). However, there were several limitations to this study that should be addressed.…”

“…Second, the resolution of the probed sites for the 9-electrode probe used is limited to a diameter of 7.5 mm. Third, the high frequency phase data used to conduct SVM classification may be affected by the presence of stray capacitance in the system, which is nearly 300 pF at each channel (Khan et al 2016). …”

Use of Bioelectric Impedance Analysis (BIA) as a new method to detect prostate cancer

“…Previous studies on BIA revealed enthusiastic results mainly in patients with aggressive cancers [5][6][7]. Studies conducted in the setting of prostate cancer in particular, were limited by the applicability of proper probes on the prostate gland surface and by the anatomic deep site in which the prostate is placed inside the pelvic bone girdle [8].…”