Roselle Anderson

Electrical impedance scanning for classifying suspicious breast lesions: first results

Abstract. It has long been established that cancer cells exhibit altered local dielectric properties compared with normal cells. Consequently, different electrical conductivity and capacitance are measurable in malignant vs normal tissues. In this study we evaluated the reliability of electrical impedance scanning (EIS), a new technology, for the classification of suspicious lesions: differentiating benign from malignant, and as a primary means of detection of breast cancer. Fifty-two women with 58 sonographically and/or mammographically suspicious findings were examined using electrical impedance scanning. Two different examination modes of TransScan TS2000 (Siemens, Erlangen, Germany), the standard-resolution mode for a routine overview examination, and the targeted high-resolution mode for a local examination of the suspicious lesion were used. All patients were additionally imaged by MR mammography (MRM) and underwent core-biopsy and/or surgical treatment after the EIS examination. With respect to the histopathological findings (29 malignant and 29 benign lesions) 27 of 29 (93.1 %) malignant lesions were correctly identified using the high-resolution mode of EIS, whereas 19 of 29 (65.5 %) benign lesions were correctly identified as benign (10 of 29 benign lesions showed as false-positive findings). Negative and positive predictive values of 90.5 and 73.0 % were observed, respectively. Using the standard-resolution mode 22 of 29 malignancies were correctly detected (sensitivity 75.9 %), whereas 22 of 29 were correctly identified as benign (specificity 72.4 %). Electrical impedance scanning appears to be a promising new technology providing a relatively high sensitivity for the verification of suspicious mammographic and/or sonographic lesions especially using the high-resolution mode for local examinations. Artifacts, such as signals from superficial skin lesions, poor contact, and air bubbles, are currently a limitation.

Additional value of electrical impedance scanning: experience of 240 histologically-proven breast lesions

The aim of this study was to quantify the clinical value of using electrical impedance scanning (EIS) as an adjunct to other diagnostic techniques in order to identify cancerous tissue based upon its inherent altered local dielectric properties. 210 consecutive women with 240 sonographically and/or mammographically suspicious findings were examined using EIS. All lesions were histologically-proven. 86/103 malignant and 91/137 benign lesions were correctly identified using EIS (87.8% sensitivity, 66.4% specificity). NPV and PPV of 84.3% and 65.2% were observed, respectively. Excluding cases as defined by a priori criteria, i.e. lesions located deeper than 35 mm, lesions larger than 35 mm, and retroareolar lesions, a sensitivity of 85.5% was observed, and for invasive cancers, 91.7%. The detection rate for ductal carcinoma in situ (DCIS) was poor (57.1%, n=14). By adding EIS to mammography and ultrasound, the sensitivity rose from 86.4 to 95.1%, whereas the accuracy decreased from 82.3 to 75.7%. EIS appears to be of interest as an adjunct to breast diagnostic techniques, performing with a reasonable sensitivity. Further investigations on histomorphological characteristics and the reasons for false-negative findings are essential to gain further knowledge about the bioelectricity of breast lesions, and prove the value of this new technology.

Electrical impedance scanning as a new imaging modality in breast cancer detection—a short review of clinical value on breast application, limitations and perspectives

Objective. Cancer cells exhibit altered local dielectric properties compared to normal cells, measurable as different electrical conductance and capacitance using electrical impedance scanning (EIS). Therefore, active biocompatible current is applied to the patient for calculation of both parameters taking into account frequency, voltage and current flow. Subjects and methods. 240 women with 280 sonographically and/or mammographically suspicious findings were examined using EIS. All lesions were histologically proven. A lesion was scored as positive, when a focal increased conductance and/or capacitance was measurable using EIS. The lesion was visible as a bright area in a 256 grey-scale computer output. Due to system limitations patients having a pacemaker or pregnant had to be excluded from the study. Results. 91/113 malignant and 108/167 benign lesions were correctly identified using EIS (80.5% sensitivity, 64.7% specificity). NPV and PPV of 83.1% and 60.7% were observed, respectively. Accuracy was 0.73. A wide range of factors can induce false positive results, although by an experienced observer a number of these findings can be detected such as scars, skin alterations, contact artefacts, air bubbles and naevi, hairs and interfering bone. Based upon visibility on ultrasound (194 lesions visible, 86 not visible) significant differences in the detection rate occurred. Histology-dependent detectability rate varied significantly with lowest rate in CIS-cases (50%). Specificity values varied histology-depending, too; probably depending on the rate of proliferation between 75% (inflammatory lesions) and papillomata (50%). Best detectability was observed in malignant lesions with a size between 20 and 30 mm. Further possible applications will be discussed regarding the currently available literature (lymph nodes, salivary glands, mathematical and animal based models). Conclusion. EIS appears to be a promising new additional technology providing a rather high sensitivity for the verification of suspicious breast lesions. Further investigations on histomorphological characteristics of false negative as well as false positive lesions are essential to gain further knowledge about the bioelectricity of breast lesions. Currently high false positive rate and observer-dependence limit clinical usage. r 2002 Elsevier Science B.V. All rights reserved.

Animal-Based Model to Investigate the Minimum Tumor Size Detectable with an Electrical Impedance Scanning Technique

RATIONALE AND OBJECTIVES The purpose of this study was to determine the minimum tumor size detectable with electrical impedance scanning (EIS) in laboratory animals. MATERIALS AND METHODS VX2 tumor cells (1 mm3) were implanted bilaterally into the upper leg musculature of five white New Zealand rabbits. EIS and ultrasound (US) were performed before, during, and immediately after implantation and on every 2nd day thereafter until tumors could be visualized with both modalities. This was followed by an extended follow-up regimen until a tumor size of 1 cm3 was reached. Rabbits were anesthetized subcutaneously. RESULTS Tumors could not be implanted in one rabbit. Neither EIS nor US were performed in one rabbit due to severe skin alterations at the implantation site. No focal increase in conductance was visible before or immediately after tumor injection. The smallest tumor identified with EIS was determined with US to be approximately 8 mm3. The mean tumor size at initial detection was 52 mm3 (determined with EIS). In two cases, the tumor was first seen with US (EIS detection was delayed with a delay of 1 and 2 days, respectively). In all remaining cases, tumors were detected simultaneously with both EIS and US. All tumors were visible with EIS. CONCLUSION The animal-based model is feasible. VX2 tumors are detectable with EIS. Tumors characterized by a focal spot at EIS could be detected starting at a tumor size of 7.5 mm3.