J. Jossinet

Bio: J. Jossinet is an academic researcher from French Institute of Health and Medical Research. The author has contributed to research in topics: Electrical impedance & Output impedance. The author has an hindex of 19, co-authored 30 publications receiving 1776 citations.

Variability of impedivity in normal and pathological breast tissue

Abstract: The impedivity of six groups of breast tissue is measured between 0.488 kHz and 1 MHz using a hand-held probe, ensuring a constant geometry factor, and a microcomputer-controlled impedance spectroscopy system. 120 spectra are collected in excised tissue samples from 64 patients undergoing breast surgery. Each spectrum consists of 12 frequency points. The mean m, the standard deviation s, and the ‘reduced standard error’ (e=s/(m N)) of the magnitude and the phase angle of the impedivity are calculated at each frequency for all groups of tissues. The variability at low frequency (f<10 kHz) is attributed to the dispersion in measurement errors. This contributed to the choice of 32 kHz as the lower limit of measurement frequency in the constructed electrical impedance tomograph. The collected data also show that frequencies larger than 1 MHz are needed for the bio-electrical characterisation of breast tissue. In the frequency range used in electrical impedance tomography the reduced standard error of impedivity in breast tissue is about 0.1 or less. The lowest dispersions are observed in the adipose tissue, carcinoma and fibro-adenoma.

The impedivity of freshly excised human breast tissue

Abstract: A set of 120 impedivity spectra was collected in breast tissue immediately after excision from 64 patients undergoing breast surgery. The measurements were made at 12 discrete frequencies halving from 1 MHz to 488 Hz. The spectra were sorted into three groups of normal tissue, mammary gland, connective tissue and adipose tissue, and three groups of pathological tissue, mastopathy, fibroadenoma and carcinoma. Intergroup multiple comparisons of the components of impedivity and admittivity were systematically carried out at every measurement frequency. The low-frequency-limit resistivity, the fractional power and characteristic frequencies were calculated from the experimental data. No significant correlation between impedivity and admittivity and patient's age was observed, except for mastopathy. No significant difference between groups of normal tissue and benign pathology (mammary gland, mastopathy and fibroadenoma) was found. The group of carcinoma differed from all the other groups principally by the low-frequency-limit resistivity, the fractional power and the phase angle at frequency above 125 kHz. These results indicate that impedance spectroscopy is appropriate for the detection of breast cancer.

Classification of breast tissue by electrical impedance spectroscopy.

Abstract: Electrical impedance spectroscopy is a minimally invasive technique that has clear advantages for living tissue characterisation owing to its low cost and ease of use. The present paper describes how this technique can be applied to breast tissue classification and breast cancer detection. Statistical analysis is used to derive a set of rules based on features extracted from the graphical representation of electrical impedance spectra. These rules are used hierarchically to discriminate several classes of breast tissue. Results of statistical classification obtained from a data set of 106 cases representing six classes of excised breast tissue show an overall classification efficiency of ∼92% with carcinoma discrimination >86%.

A Review of Parameters for the Bioelectrical Characterization of Breast Tissue

Abstract: In the data set collected by the authors in freshly excised breast tissue, the admittance loci generally differed from circular arcs, rendering the calculation of the usual set of parameters impossible. Alternative parameters were used for the analysis of these data. The present study consists of the definition and evaluation of a set of such parameters aimed at the characterization and differentiation of breast tissues. These parameters were defined so that their calculation does not require the fit of circular arcs to the experimental points and is independent of any equivalent circuit model. The results of the statistical analysis showed significant differences between most of the tissue groups, especially between cancerous tissue and all the other groups, which confirmed that impedance spectroscopy can be considered as potentially suitable for breast cancer detection.

Electrical Impedance Tomography

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

Transport phenomena in nanofluidics

Abstract: This thesis explores transport phenomena in nanochannels on a chip. Fundamental nanofluidic ionic studies form the basis for novel separation and preconcentration applications for proteomic purposes. The measurements were performed with 50-nm-high 1D nanochannels, which are easily accessible from both sides by two microchannels. Nanometer characteristic apertures were manufactured in the bonded structure of Pyrex-amorphous silicon – Pyrex, in which the thickness of the amorphous silicon layer serves as a spacer to define the height of the nanochannels. The geometry of the nanometer-sized apertures is well defined, which simplifies the modeling of the transport across them. Compared to biological pores, the present nanochannels in Pyrex offer increased stability. Fundamental characteristics of nanometer-sized apertures were obtained by impedance spectroscopy measurements of the nanochannel at different ionic strengths and pH values. A conductance plateau (on a log-log scale) was modeled and measured, establishing due to the dominance of the surface charge density in the nanochannels, which induces an excess of mobile counterions to maintain electroneutrality. The nanochannel conductance can be regulated at low ionic strengths by pH adjustment, and by an external voltage applied on the chip to change the zeta potential. This field-effect allows the regulation of ionic flow which can be exploited for the fabrication of nanofluidic devices. Fluorescence measurements confirm that 50-nm-high nanochannels show an exclusion of co-ions and an enrichment of counterions at low ionic strengths. This permselectivity is related to the increasing thickness of the electrical double layer (EDL) with decreasing salt concentrations, which results in an EDL overlap in an aperture if the height of the nanochannel and the thickness of the EDL are comparable in size. The diffusive transport of charged species and therefore the exclusion-enrichment effect was described with a simple model based on the Poisson-Boltzmann equation. The negatively charged Pyrex surface of the nanometer characteristic apertures can be inversed with chemical surface pretreatments, resulting in an exclusion of cations and an enrichment of anions. When a pressure gradient is applied across the nanochannels, charged molecules are electrostatically rejected at the entrance of the nanometer-sized apertures, which can be used for separation processes. Proteomic applications are presented such as the separation and preconcentration of proteins. The diffusion of Lectin proteins with different isoelectric points and very similar compositions were controlled by regulating the pH value of the buffer. When the proteins are neutral at their pI value, the diffusion coefficient is maximal because the biomolecules does not interact electrostatically with the charged surfaces of the nanochannel. This led to a fast separation of three Lectin proteins across the nanochannel. The pI values measured in this experiment are slightly shifted compared to the values obtained with isoelectric focusing because of reversible adsorption of proteins on the walls which affects the pH value in the nanochannel. An important application in the proteomic field is the preconcentration of biomolecules. By applying an electric field across the nanochannel, anionic and cationic analytes were preconcentrated on the cathodic side of the nanometer-sized aperture whereas on the anodic side depletion of ions was observed. This is due to concentration polarization, a complex of effects related to the formation of ionic concentration gradients in the electrolyte solution adjacent to an ion-selective interface. It was measured that the preconcentration factor increased with the net charge of the molecule, leading to a preconcentration factor of > 600 for rGFP proteins in 9 minutes. Such preconcentrations are important in micro total analysis systems to achieve increased detection signals of analytes contained in dilute solutions. Compared to cylindrical pores, our fabrication process allows the realization of nanochannels on a chip in which the exclusion-enrichment effect and a big flux across the nanometer-sized aperture can be achieved, showing the interest for possible micro total analysis system applications. The described exclusion-enrichment effect as well as concentration polarization play an important role in transport phenomena in nanofluidics. The appendix includes preliminary investigations in DNA molecule separation and fluorescence correlation spectroscopy measurements, which allows investigating the behavior of molecules in the nanochannel itself.

Acoustic imaging catheter and the like

Abstract: Acoustic imaging balloon catheters formed by a disposable liquid-confining sheath supporting a high fidelity, flexible drive shaft which carries on its end an ultrasound transducer and includes an inflatable dilatation balloon. The shaft and transducer rotate with sufficient speed and fidelity to produce real time images on a T.V. screen. In preferred embodiments, special features that contribute to the high fidelity of the drive shaft include the particular multi-filar construction of concentric, oppositely wound, interfering coils, a pre-loaded torque condition on the coils enhancing their interfering contact, and dynamic loading of the distal end of the probe, preferably with viscous drag. The coil rotating in the presence of liquid in the sheath is used to produce a desirable pressure in the region of the transducer. Numerous selectable catheter sheaths are shown including a sheath with an integral acoustically-transparent window, sheaths with end extensions that aid in positioning, a liquid injection-producing sheath, a sheath having its window section under tension employing an axially loaded bearing, a sheath carrying a dilatation or positioning balloon over the transducer, a sheath carrying a distal rotating surgical tool and a sheath used in conjunction with a side-viewing trocar.

Wearable sensors: modalities, challenges, and prospects

Abstract: Wearable sensors have recently seen a large increase in both research and commercialization. However, success in wearable sensors has been a mix of both progress and setbacks. Most of commercial progress has been in smart adaptation of existing mechanical, electrical and optical methods of measuring the body. This adaptation has involved innovations in how to miniaturize sensing technologies, how to make them conformal and flexible, and in the development of companion software that increases the value of the measured data. However, chemical sensing modalities have experienced greater challenges in commercial adoption, especially for non-invasive chemical sensors. There have also been significant challenges in making significant fundamental improvements to existing mechanical, electrical, and optical sensing modalities, especially in improving their specificity of detection. Many of these challenges can be understood by appreciating the body's surface (skin) as more of an information barrier than as an information source. With a deeper understanding of the fundamental challenges faced for wearable sensors and of the state-of-the-art for wearable sensor technology, the roadmap becomes clearer for creating the next generation of innovations and breakthroughs.

A large-scale study of the ultrawideband microwave dielectric properties of normal breast tissue obtained from reduction surgeries.

Abstract: The efficacy of emerging microwave breast cancer detection and treatment techniques will depend, in part, on the dielectric properties of normal breast tissue. However, knowledge of these properties at microwave frequencies has been limited due to gaps and discrepancies in previously reported small-scale studies. To address these issues, we experimentally characterized the wideband microwave-frequency dielectric properties of a large number of normal breast tissue samples obtained from breast reduction surgeries at the University of Wisconsin and University of Calgary hospitals. The dielectric spectroscopy measurements were conducted from 0.5 to 20 GHz using a precision openended coaxial probe. The tissue composition within the probe’s sensing region was quantified in terms of percentages of adipose, fibroconnective and glandular tissues. We fit a one-pole Cole–Cole model to the complex permittivity data set obtained for each sample and determined median Cole–Cole parameters for three groups of normal breast tissues, categorized by adipose tissue content (0–30%, 31–84% and 85–100%). Our analysis of the dielectric properties data for 354 tissue samples reveals that there is a large variation in the dielectric properties of normal breast tissue due to substantial tissue heterogeneity. We observed no statistically significant difference between the within-patient and between-patient variability in the dielectric properties. (Some figures in this article are in colour only in the electronic version)