t. This paper surveys some of the work our group has done in electrical impedance tomography.

Electrical Impedance Tomography

Electrical impedance tomography (EIT) has been the subject of quite intensive research for about 20 years but has yet to become established as a routine tool in healthcare. None the less the volume of published research work in this area is still rising. This review takes a broad look at what has been achieved and attempts to give the reader sufficient information to form an opinion as to the likely future for this interesting area of research.

Electrical impedance tomography (EIT): a review

Electrical impedance tomography (EIT) is a relatively new imaging method that has evolved over the past 20 years. It has the potential to be of great value in clinical diagnosis; however, EIT is a technically difficult problem to solve in terms of developing hardware for data capture and the algorithms to reconstruct the images. This review looks at the development of EIT and how it has evolved. It focuses on its clinical applications, examining hardware for the collection of data and reconstruction algorithms to generate images. Finally, this review looks at future developments that are evolving from EIT. These new variations use mixed modalities that may produce interesting new clinical imaging tools.

https://www.annualreviews.org/doi/pdf/10.1146/annurev.bioeng.8.061505.095716

Bioimpedance tomography (electrical impedance tomography)

https://www.who.int/immunization/sage/Dennycervical_cancer.pdf

Chapter 8: Screening for cervical cancer in developing countries.

Electrical Impedance Spectroscopy Study of Biological Tissues.

This paper describes the Sheffield Mk3.5 EIT/EIS system which measures both the real and imaginary part of impedance at 30 frequencies between 2 kHz and 1.6 MHz. The system uses eight electrodes with an adjacent drive/receive electrode data acquisition protocol. The system is modular, containing eight identical data acquisition boards, which contain DSPs to generate the drive frequencies and to perform the FFT used for demodulation. The current drive is in three sequentially applied packets, where each packet contains ten summed sine waves. The data acquisition system is interfaced to a host PC through an optically isolated high speed serial link (RS485) running at 2 Mbaud (2 Mbits s(-1)). Measurements on a saline filled tank show that the average signal to noise performance of the system is 40 dB measured across all frequencies and that this figure is independent of frequency of measurement. These results suggest that the current system is 10 dB better in absolute terms than the previous Sheffield (Mk3a) system.

/pdf/mk3-5-a-modular-multi-frequency-successor-to-the-mk3a-eis-20vrew5w3s.pdf

Mk3.5: a modular, multi-frequency successor to the Mk3a EIS/EIT system.

The objective of this study was to assess the performance of cervical impedance spectroscopy in the detection of cervical intraepithelial neoplasia (CIN) using the new MKIII impedance probe. A prospective observational study recruited women referred to colposcopy with an abnormal Papanicolaou smear. A pencil probe incorporating four gold electrodes was used to measure electrical impedance spectra from cervical epithelium. Colposcopy examinations, including probe positioning, were video recorded to allow for correlation between results obtained from colposcopic impression, histopathologic examination of colposcopic punch biopsies, and impedance measurements. Cervical impedance–derived parameters R, S, R/S, C, and Fc were assessed to see if significant difference in values obtained in CIN and normal epithelium existed. The performance of the probe in identifying women with CIN was also assessed. One hundred seventy-six women were recruited and 1168 points analyzed. Parameters R, S, and Fc showed significant separation of CIN or squamous intraepithelial lesion (SIL) from squamous, mature metaplastic, and columnar epithelium. Sensitivities of 74% and specificity of 53% can be achieved in identifying CIN 2/3 (High-grade SIL) in screened women. We conclude that cervical impedance spectrometry provides a potentially promising real-time screening tool for CIN with similar sensitivity and specificity to currently used screening tests. Further research is ongoing to develop the probe for potential clinical use.

The use of electrical impedance spectroscopy in the detection of cervical intraepithelial neoplasia.

Detection of cervical intraepithelial neoplasia using impedance spectroscopy: a prospective study.

The electrical resistivity of lung tissue can be related to the structure and composition of the tissue and also to the air content. Conditions such as pulmonary oedema and emphysema have been shown to change lung resistivity. However, direct access to the lungs to enable resistivity to be measured is very difficult. We have developed a new method of using electrical impedance tomographic (EIT) measurements on a group of 142 normal neonates to determine the absolute resistivity of lung tissue. The methodology involves comparing the measured EIT data with that from a finite difference model of the thorax in which lung tissue resistivity can be changed. A mean value of 5.7 ± 1.7Ωm was found over the frequency range 4kHz to 813kHz. This value is lower than that usually given for adult lung tissue but consistent with the literature on the composition of the neonatal lung and with structural modelling.

Neonatal lungs--can absolute lung resistivity be determined non-invasively?

https://www.gynecologiconcology-online.net/article/S0090-8258(05)00527-5/pdf

P. Milnes

Papers

Mk3.5: a modular, multi-frequency successor to the Mk3a EIS/EIT system.

The use of electrical impedance spectroscopy in the detection of cervical intraepithelial neoplasia.

Detection of cervical intraepithelial neoplasia using impedance spectroscopy: a prospective study.

Neonatal lungs--can absolute lung resistivity be determined non-invasively?

A clinical study of the use of impedance spectroscopy in the detection of cervical intraepithelial neoplasia (CIN).