Biomedical subjects

Jacques Jossinet

Publications and source records attributed to Jacques Jossinet.

6 recordsLinked to original sources

PubMed2005

Assessment of 1-lead and 2-lead electrode patterns in electrical impedance endotomography.

Electrical impedance endotomography (EIE) is a modality of impedance imaging where the electrodes are located on an insulating core placed at the centre of the region of interest. The absence of a physical limit to the medium surrounding the probe enables the use of remote electrodes. The present study compares the features of 2-lead measurements, where the two pairs of electrodes are located on the probe, to 1-lead measurements, where one of the two injection electrodes and one of the two sensing electrodes are located at a distance far away from the probe. The methodology was the characterization of the sensitivity matrix under the influence of electrode pattern, reconstruction radius and mesh construction. Three mesh constructions, three values of the reconstruction radius and five electrode patterns were compared. The study was carried out in 2D using calculated data. Measurement noise was simulated by an addition of 5% Gaussian white noise. The images were reconstructed using the Tikhonov method and L-curve technique. The results show that the reconstruction mesh and the radius of the reconstruction domain have less influence on the conditioning of the sensitivity matrix than the electrode pattern. Both 1-lead and 2-lead configurations enabled the reconstruction of images of relatively similar quality. Additional selection criteria are expected from hardware considerations.

Animals↗

PubMed2005

Impedance changes in liver tissue exposed in vitro to high-energy ultrasound.

The present study reports the impedance changes observed in bovine liver samples exposed in vitro to high-intensity ultrasound. The measurement frequency ranged from 80 kHz to 2 MHz. The treatment resulted in the average increase of 20% in impedance magnitude at low frequency and the average decrease of 30% at high frequency. The phase angle increased significantly by more than 15 degrees at all measurement frequencies. The slope of the log-modulus of impedance against log-frequency increased in treated tissue at frequencies above 500 kHz. This change was attributed to the alteration of the capacitive response of the tissue. The experimental observations are consistent with the known changes induced by high-energy ultrasound in liver tissue. This study confirmed that ultrasound energy produces measurable changes in a tissue's impedance and that indices can be derived to distinguish between original and treated tissues. The results obtained in liver tissue need confirmation in organs treatable with therapeutic ultrasound, such as breast and prostate.

Animals↗

PubMed2005

Bioimpedance and p-Health.

Bio-impedance is the electrical impedance of living matter. Bio-impedance methods present a range of known advantages for medical and clinical applications including low-cost, non-invasiveness and harmlessness. The measured parameter reflects the physiological and pathological processes that take place within human body. The technological progress in instrumentation has significantly contributed to the progress that has been observed during the last past decades in impedance spectroscopy and electrical impedance tomography. Although bioimpedance is not a physiological parameter, the method enables tissue characterisation and functional monitoring and can contribute to the monitoring of the health status of a person. The association of this flexible and versatile method with micro-electronics and wireless telecommunication systems opens a new field of potential applications.

Biomedical Technology↗

PubMed2004

Electrical impedance endotomography: sensitivity distribution against bipolar current patterns.

Electrical impedance endotomography (EIE) is a modality where the electrodes are located around an insulating core placed inside the region of interest. This approach results in significant differences with respect to conventional EIT. The paper examines the sensitivity distribution of bipolar current patterns and the influence of the spacing between the drive electrodes using a two-dimensional (2D) mathematical model. The number of pixels of sensitivity above a given sensitivity threshold decreases faster with the distance to the probe for diametric and adjacent drive than for other bipolar drive patterns. The reconstruction of images from datasets collected in vitro using a 16-electrode probe confirmed the feasibility of the method at least within a range extending to three times the radius of the probe, under the described experimental conditions. Reduction of system noise, multiple-current patterns and the use of remote current and voltage electrodes are potential methods to increase the sensitivity range. Further work includes the improvement of the model to account for finite length electrodes and the miniaturization of the probe.

Artifacts↗

PubMed2002

Electrical impedance endotomography.

In electrical impedance endotomography (EIE), the impedance measuring electrodes are placed at the centre of the region of interest instead of encircling it, as in usual electrical impedance tomography. EIE has been developed for prostate imaging. The developed mathematical model enables the derivation of analytical equations for electric potential, electric field and sensitivity. This paper focuses on the selection of an optimal current injection method capable of sensing distant points. Experimental measurements were carried out in vitro using an enlarged size, 50 mm diameter, 16-electrode mock-up probe placed in tap water. The collected data enabled the production of images of a circular insulating target, 10 mm in diameter located 100 mm from the axis of the probe. Future work includes extension of sensitivity range, improvement of image reconstruction, design of a multiple frequency hardware system and construction of a real-size, biocompatible impedance probe.

Computer Simulation↗

PubMed2002

Electrical impedance endo-tomography: imaging tissue from inside.

This paper describes a new method for scanning the conductivity of a tissue or an organ using a multielectrode impedance probe placed at the center of the region of interest. The long-term objective of the study is the evaluation, using an urethral impedance probe, of the lesion produced by ultrasound ablathermy of localized prostate cancer. The probe consists of electrodes placed at the surface of an insulating cylinder. The injected current passes around the cylinder and spreads in the medium surrounding the probe. This paper presents the theoretical bases of this method, the calculated sensitivity distributions of electrode configurations involving a pair of diametrically opposed electrodes and an application in vitro. The experimental set-up consisted of a water tank and a 16-electrode prototype probe 50 mm in diameter. Data sets were collected in the presence of conductivity perturbations produced by small size insulators or conductors and a 7.5% constant perturbation model. The presented images, although reconstructed using a simple retro-projection algorithm, demonstrate the feasibility of the method. Improvements in data collection and image reconstruction are possible.

Electric Impedance↗