Assessment of Low Back Pain in Helicopter Pilots Using Electrical Bio-Impedance Technique: A Feasibility Study.

Low back pain (LBP) is known to pose a serious threat to helicopter pilots. This study aimed to explore the potential of electrical bio-impedance (EBI) technique with the advantages of no radiation, non-invasiveness and low cost, which is intended to be used as a daily detection tool to assess LBP in primary aviation medical units. The LBP scales (severity) in 72 helicopter pilots were assessed using a pain questionnaire, while the bilateral impedance measurements of the lumbar muscle were carried out with a high precision EBI measurement system. Results showed that the modulus of lumbar muscle impedance increased with LBP scale whereas the phase angle decreased. For different LBP scales, significant differences were found in the modulus of lumbar muscle impedance sum on both sides (Z sum ), as well as in the modulus and phase angle of lumbar muscle impedance difference between both sides (Z diff and ϕ diff ), respectively (P < 0.05). Moreover, Spearman's correlation analysis manifested a strong correlation between Z sum and LBP scale (R = 0.692, P < 0.01), an excellent correlation between Z diff and LBP scale (R = 0.86, P < 0.01), and a desirable correlation between ϕ diff and LBP scale (R = -0.858, P < 0.01). In addition, receiver operator characteristic analysis showed that for LBP prediction, the area under receiver operator characteristic curve of Z sum , Z diff , and ϕ diff were 0.931, 0.992, and 0.965, respectively. These findings demonstrated that EBI could sensitively and accurately detect the state of lumbar muscle associated with LBP, which might be the potential tool for daily detection of LBP in primary aviation medical units.

Probing for Stomach using the Focused Impedance Method (FIM).

For probing deep organs of the body using electrical impedance, the conventional method is to use Electrical Impedance Tomography (EIT). However, this would be a sophisticated machine and will be very expensive when a full 3D EIT is developed in the future. Furthermore, for most low income countries such expensive devices may not deliver the benefits to a large number of people. Therefore, this paper suggests the use of simpler techniques like Tetrapolar Impedance Measurement (TPIM) or Focused Impedance Method (FIM) in probing deeper organs. Following a method suggested earlier by one of the authors, this paper studies the possibility of using TPIM and FIM for the stomach. Using a simplified model of the human trunk with an embedded stomach, a finite element simulation package, COMSOL, was used to obtain transfer impedance values and percentage contribution of the stomach region in the total impedance. For this work, judicious placement of electrodes through qualitative visualizations based on point sensitivity equations and equipotential concepts were made, which showed that reasonable contribution of the stomach region is possible through the use of TPIM and FIM. The contributions were a little over 20% which is of similar order of the cross-sectional area percentage of the stomach with respect to that of the trunk. For the case where the conductivity of the stomach region was assumed about 4 times higher, the contributions increased to about 38%. Through further studies this proposed methods may contribute greatly in the study of deeper organs of the body.

Identifying and Localizing of the In-depth Pulmonary Nodules Using Electrical Bio-Impedance.

Intraoperative localization of small and in-depth pulmonary nodules particularly during video-assisted thoracoscopic surgery (VATS), is one of the main challenges for Thoracic surgeons. Failure to determine the location of nodules may lead to a large incision in the normal lung tissue or the conversion of the minimally invasive surgery to an open thoracotomy. The aim of this study is to evaluate the use of electrical bio-impedance measurement to precisely determine the position of in-depth pulmonary nodules and tumors, which are not visible during thoracoscopic surgeries or even are not palpable during open thoracic surgeries. With this regard, a suitable bio-impedance sensor similar to a biopsy forceps has been designed in order to measure the lung tissue bio-impedance. Using the available data on the electrical properties recorded from lung tissue during inhalation and exhalation, combined with the tumor modeling in COMSOL software, the effect of different parameters including the size and depth of tumor and the relative difference of electrical properties between healthy and tumoral tissue has been assessed. Furthermore, the geometric characteristics of the proposed sensor are considered. The results generally verify that larger size of nodules results in an easier distinguishing process. Additionally, it is worthy to note that applying a larger geometrically sensor is essential to detect the small and in-depth nodules.

Design and Integration of Electrical Bio-impedance Sensing in Surgical Robotic Tools for Tissue Identification and Display.

The integration of intra-operative sensors into surgical robots is a hot research topic since this can significantly facilitate complex surgical procedures by enhancing surgical awareness with real-time tissue information. However, currently available intra-operative sensing technologies are mainly based on image processing and force feedback, which normally require heavy computation or complicated hardware modifications of existing surgical tools. This paper presents the design and integration of electrical bio-impedance sensing into a commercial surgical robot tool, leading to the creation of a novel smart instrument that allows the identification of tissues by simply touching them. In addition, an advanced user interface is designed to provide guidance during the use of the system and to allow augmented-reality visualization of the tissue identification results. The proposed system imposes minor hardware modifications to an existing surgical tool, but adds the capability to provide a wealth of data about the tissue being manipulated. This has great potential to allow the surgeon (or an autonomous robotic system) to better understand the surgical environment. To evaluate the system, a series of ex-vivo experiments were conducted. The experimental results demonstrate that the proposed sensing system can successfully identify different tissue types with 100% classification accuracy. In addition, the user interface was shown to effectively and intuitively guide the user to measure the electrical impedance of the target tissue, presenting the identification results as augmented-reality markers for simple and immediate recognition.

The Development of a Four-Electrode Bio-Impedance Sensor for Identification and Localization of Deep Pulmonary Nodules.

Identifying and localizing of deep pulmonary nodules are among the main challenges that thoracic surgeons face during operations, particularly in thoracoscopic procedures. To facilitate this, we have tried to introduce a non-invasive and safe method by measuring the lung electrical bio-impedance spectrum with a four-electrode array sensor. To study the feasibility of this method, since any change in the depth or diameter of the nodule in the lung tissue is not practical, we used the finite element modeling of the lung tissue and pulmonary nodule to allow changes in the depth and diameter of the nodule, as well as the distance in between the injection electrodes. Accordingly, a bio-impedance sensor was designed and fabricated. By measuring the electrical impedance spectrum of pulmonary tissues in four different specimens with a frequency band of 50 kHz to 5 MHz, 4 pulmonary nodules at four different depths were identified. The obtained bio-impedance spectrum from the lung surface showed that the magnitude and phase of electrical bio-impedance of the tumoral tissue at each frequency is smaller than that of the healthy tissue. In addition, the frequency characteristic varies in the Nyquist curves for tumoral and healthy lung tissues.

A New Venous Entry Detection Method Based on Electrical Bio-impedance Sensing.

Peripheral intravenous catheterization (PIVC) is frequently required for various medical treatments. Over 1 billion PIVC operations are performed per year in the United States alone. However, this operation is characterized by a very low success rate, especially amongst pediatric patients. Statistics show that only 53% of first PIVC attempts are successful in pediatric patients. Since their veins are small and readily rupture, multiple attempts are commonly required before successfully inserting the catheter into the vein. This article presents and evaluates a novel venous entry detection method based on measuring the electrical bio-impedance of the contacting tissue at the tip of a concentric electrode needle (CEN). This detection method is then implemented in the design of a clinical device called smart venous entry indicator (SVEI), which lights up a LED to indicate the venous entry when the measured value is within the range of blood. To verify this detection method, two experiments are conducted. In the first experiment, we measured the bio-impedance during the insertion of a CEN into a rat's tail vein with different excitation frequencies. Then three classifiers are tested to discriminate blood from surrounding tissues. The experimental results indicate that with 100 kHz excitation frequency the blood bio-impedance can be identified with accuracy nearly 100%, demonstrating the feasibility and reliability of the proposed method for venous entry detection. The second experiment aims to assess the impact of SVEI on PIVC performance. Ten naive subjects were invited to catheterize a realistic baby arm phantom. The subjects are equally divided into two groups, where one group does PIVC with SVEI and the other group uses an ordinary IV catheter. The results show that subjects using SVEI can achieve much higher success rates (86%) than those performing PIVC in a conventional way (12%). Also, all subjects assisted by SVEI succeeded in their first trials while no one succeed in their first attempt using the conventional unassisted system. These results demonstrate the proposed detection method has great potential to improve pediatric PIVC performance, especially for non-expert clinicians. This supports further investment towards clinical validation of the technology.

The impact of lesion vascularisation on tumours detection by electrical impedance scanning at 200 Hz.

OBJECTIVE: Cancer cells exhibit altered local dielectric properties compared to normal cells. These properties are measurable as a difference in electrical conductance using electrical impedance scanning (EIS). EIS is at present not sufficiently accurate for clinical routine despite its technological advantages. To modify the technology and increase its accuracy, the factors that influence precision need to be analysed and identified. While size, depth, localisation and invasiveness affect sensitivity, vascularisation might show an increased conductance and thus might affect specificity. SUBJECTS AND METHODS: All patients were investigated with EIS (TransScan TS 2000, Migdal Ha Emek, Israel) Planned DCE-MRI prior to histological clarification were included (295 lesions). Dynamic enhancements were assigned scores after analysis of subtracted images after application of Gd-DTPA. D1: strong enhancement of >100% from initial signal obtained on native T1weighted sequence; D2: moderate enhancement 50-100%; D3: enhancement similar to glandular tissue, <50%; D4: subtle or no enhancement, less then surrounding glandular tissue. RESULTS: 89/113 malignant and 107/182 benign findings were visible by a focal increased conductance and/or capacitance using EIS (Sensitivity 79%, Specificity 59%). DCE-MRI was aborted due to claustrophobia in 17/295 cases. MR was used and out of 278 completed MR examinations, 101/104 malignant and 141/174 benign lesions were correctly diagnosed as benign or malignant leading to a sensitivity of 97% and a specificity of 81%. D1 benign lesions were positive in EIS in 33/55 cases suggesting a specificity of 44.4%. This value increases significantly with decreased vascularity to 68.9% (D2-4; 82/119). Out of 60 fibroadenomatous lesions, 10/23 fibroadenomas in class 1 had no focal increased conductance or capacitance and were thus considered as non-suspicious in EIS. The same result was applicable for the 29/37 benign lesions with a D2-4 contrast uptake (43.5% vs. 78.4%, p<.01). CONCLUSION: Vascularisation influences the measurable conductance at low frequency and therefore partially causes the insufficiently low specificity of EIS. Impedance measurements at frequencies in a range of 0.1 KHz to 1 MHz are required . According to theoretical and in vitro studies this might increase the accuracy of EIS technology. © 2007 Biomedical Imaging and Intervention Journal. All rights reserved.