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Shimon Abboud

Publications and source records attributed to Shimon Abboud.

14 recordsLinked to original sources
PubMed2006

Induced current bio-impedance technique for monitoring bone mineral density--a simulation model.

In this study, the feasibility of using induced current bio-impedance technique as a method to determine and monitor bone mineral density (BMD) was theoretically evaluated using computerized simulation model. A 2D polar coordinates numerical solver was developed using the Finite Volume Method (FVM) in order to simulate the developed potentials over an axial CT cross section of a human thigh. Varying femur BMD were simulated by varying femur relative permittivity values. At the chosen excitation current of 1 ampere at a frequency of 20 kHz, the real component of the surface potential was found to be more sensitive to BMD variation than the imaginary component (3.9 microV g(-1) cm3 compared with 0.174 microV g(-1) cm3). The correlation between varying femur permittivities and the real component of the developed surface potential was found to be quadratic and influenced by the coil geometry and the measuring point location. Measurement sensitivity was improved either by taking the measuring point closer to the femur location or by minimizing the distance between the excitation coil and the femur. These results provide the basic principle that may enable a future use of bio-impedance technique for bone density evaluation and monitoring.

Animals↗
PubMed2005

Contactless bio-impedance monitoring technique for brain cryosurgery in a 3D head model.

A contactless induced-current bio-impedance system for monitoring brain cryosurgery procedure was modeled and numerically simulated, where the excitation coil was also performing as the measuring, or pick-up coil. A segmented three-dimensional (3D) MRI database was used for building the volume conductor geometry, and the numerical finite-volume method was employed for solving the forward problem for calculating the scalar potential distribution and the second-order voltage change on the pick-up coil. Several coil configurations were considered, varying in their relative positioning to the 3D head model. For each case, the sensitivity of the measured voltage change on the excitation coil to the volume of a frozen lesion was calculated. The highest sensitivity (1.1 x 10(-5) relative voltage change per mm3 of frozen tissue) was obtained for a coil arrangement where its closest segment to the volume conductor is at the maximum distance away from the frozen region position. The simulated system signal-to-carrier ratio was O(10(-8)).

Brain↗
PubMed2005

Induced current bio-impedance technique for monitoring cryosurgery procedure in a two-dimensional head model using generalized coordinate systems.

In the noninvasive bio-impedance technique, small amplitude currents are applied to the body and the developing potentials on its surface are measured. This noninvasive technique is used to monitor physiological and pathological processes, which alter the values or the spatial distribution of the electrical impedance inside the human body. A possible application of the bio-impedance technique is monitoring brain cryosurgery procedure--a surgical technique that employs freezing to destroy undesirable tissues. A numerical solver was developed to evaluate the ability of an induced-current bio-impedance system to monitor the growth of the frozen tissue inside the head in simulation. The forward-problem bio-impedance solver, which is based on the finite volume method in generalized two-dimensional (2-D) coordinate systems, was validated by a comparison to a known analytical solution for body-fitted and Cartesian meshing grids. The sensitivity of the developed surface potential to the ice-ball area was examined using a 2-D head model geometry, and was found to range between 0.8 x 10(-2) and 1.68 x 10(-2) (relative potential difference/mm2), depending on the relative positioning of the excitation coil and the head. The maximal sensitivity was achieved when the coil was located at the geometrical center of the model.

Animals↗
PubMed2004

Model-based prediction of expiratory resistance index in patients with asthma.

OBJECTIVES: Develop a sensitive algorithm and index for detection of asthma patients using forced expiratory flow curves. METHODS: A lumped-parameter model of forced expiration was developed. The model can predict the flow-volume curve during forced expiratory maneuver. The flow-volume curves generated by the model depend on values of resistance parameters (FER). Use of flow-volume curves recorded from normal subjects and from patients with asthma before and after ventolin inhalation as inputs for the inverse model, yielded the resistance parameters for each case. These parameters are based on the entire information presented in the flow-volume curve and on the reduction in flow at all lung volumes. RESULTS: Forced Expiratory Resistance (FER(N)) indices were estimated at different percent of lung volumes using the inverse model. The index was significantly affected by inhalation of ventolin in asthmatic patients and was insensitive to ventolin inhalation in normal patients. In asthmatic patients, the FER index at five lung volumes (out of eight), was two--five times greater than in normal subjects with p < 0.05 (three of them with p < 0.01). CONCLUSIONS: The estimated parameters were sensitive indicators of the degree of lung function impairment and were able to accurately distinguish between healthy and asthmatic patients.

Algorithms↗
PubMed2004

Induced current electrical impedance tomography system: experimental results and numerical simulations.

In electrical impedance tomography (EIT), measurements of developed surface potentials due to applied currents are used for the reconstruction of the conductivity distribution. Practical implementation of EIT systems is known to be problematic due to the high sensitivity to noise of such systems, leading to a poor imaging quality. In the present study, the performance of an induced current EIT (ICEIT) system, where eddy current is applied using magnetic induction, was studied by comparing the voltage measurements to simulated data, and examining the imaging quality with respect to simulated reconstructions for several phantom configurations. A 3-coil, 32-electrode ICEIT system was built, and an iterative modified Newton-Raphson algorithm was developed for the solution of the inverse problem. The RMS norm between the simulated and the experimental voltages was found to be 0.08 +/- 0.05 mV (<3%). Two regularization methods were implemented and compared: the Marquardt regularization and the Laplacian regularization (a bounded second-derivative regularization). While the Laplacian regularization method was found to be preferred for simulated data, it resulted in distinctive spatial artifacts for measured data. The experimental reconstructed images were found to be indicative of the angular positioning of the conductivity perturbations, though the radial sensitivity was low, especially when using the Marquardt regularization method.

Algorithms↗
PubMed2004

Automatic identification of bacterial types using statistical imaging methods.

The objective of the current study is to develop an automatic tool to identify microbiological data types using computer-vision and statistical modeling techniques. Bacteriophage (phage) typing methods are used to identify and extract representative profiles of bacterial types out of species such as the Staphylococcus aureus. Current systems rely on the subjective reading of profiles by a human expert. This process is time-consuming and prone to errors, especially as technology is enabling the increase in the number of phages used for typing. The statistical methodology presented in this work, provides for an automated, objective and robust analysis of visual data, along with the ability to cope with increasing data volumes.

Bacteriophage Typing↗
PubMed2003

Induced-current electrical impedance tomography: a 2-D theoretical simulation.

A reconstruction algorithm, based on the modified Newton-Raphson algorithm, was developed for induced-current electrical impedance tomography and studied in theoretical two-dimensional geometry representing a human thorax. The finite-volume method was applied for the discretization of the physical domain, resulting in a symbolic representation of the Jacobian matrix, which is accurate and fast to construct. Several system configurations, differing in the number of excitation coils and electrodes, were simulated, and the performance in thoracic imaging was studied. It was found that a six-coil system shows a significant 40% improvement of conductivity values reconstruction over the three-coil system (an error of 2.06 omega(-1) compared with 3.44 omega(-1)). A number of 32 electrodes was found to be sufficient, being the smallest number of electrodes to still provide a reasonable performance (only 4.2% degradation in average conductivity error compared with the maximum possible 106-electrode system).

Algorithms↗
PubMed2003

Validation of vital signs recorded via a new telecare system.

A telecare system (Medic4All) has been developed that relies on a wireless wristwatch-like sensor to measure the pulse wave from the radial artery. From this, the heart rate and respiration rate are derived. The system's performance was examined by comparing the results obtained from the pulse wave signal with those obtained from conventional electrocardiographic and spirometer devices. A total of 144 patients participated in the study; their mean (SD) age was 43 (18) years. There were 44 cardiac patients in group 1 and 100 healthy patients, who were studied in their homes, in group 2. There was a significant correlation between the heart rates measured by the two monitoring methods. A 'difference versus average' analysis showed that the error distribution had a mean (SD) value of -0.1 (3.3) beats/min. Similarly, the respiration rates measured by the two techniques were significantly correlated. The error distribution had a mean (SD) value of 0.1 (1.9) respirations/min. The present study suggests that the wrist-worn sensor represents a promising tool for online detection and monitoring of vital signs in the home.

Adult↗
PubMed2002

Heart rate variability parameters correlate with functional independence measures in ischemic stroke patients.

This study gives quantitative information regarding the effect of brain infarction on the regulation of the cardiovascular system. Electrocardiograms of 16 patients, ranging from 54 to 85 years old, admitted for rehabilitation after an ischemic supratentorial stroke, all without a history of cardiac disease or rhythm disturbances, were recorded during physiotherapy effort. All patients were evaluated for the functional independence measure (FIM) score 48 to 72 hours following admission and repeated at one week before discharge. The heart rate variability (HRV) parameters: standard deviation (SD) of the RR series, the power spectrum of the RR intervals for the low frequency range (LF: 0.04-0.15 Hz), and the high frequency range (HF: 0.15-0.4 Hz) were calculated. The results showed that all heart rate variability parameters had statistically significant relationship with the FIM on admission and discharge scores. In conclusion, the HRV parameters correlate with the clinical measures of function: the greater the HRV parameter the higher the FIM score. The presented technique may prove useful as a prognostic tool providing a simple way for determining functional performance of stroke patients.

Aged↗
PubMed2002

Dynamic cardiophysiologic variables correlate with lesion location and FIMTM in patients with ischemic stroke.

OBJECTIVE: To examine the correlation between a clinical measure of function in patients undergoing rehabilitation who had recently had an ischemic stroke and to examine cardiophysiologic measures registered during effort. DESIGN: A cohort study comprising a sample of consecutive patients, without a history of cardiac disease or rhythm disturbances, admitted for rehabilitation after an ischemic supratentorial stroke. All patients were examined for the FIM trade mark score and dynamic cardiophysiologic variables. Results were analyzed in relation to stroke location. Thirty-eight patients participated in the study. Ten patients had a superficial lesion, 20 had a deep brain lesion, and eight had no noticeable lesion by computed tomographic imaging. Function was measured with the FIM instrument 48-72 hr after admission and repeated at 1 wk before discharge. Electrocardiographic activity was recorded during physiotherapy treatment. The relationship between the RR and QT intervals in the electrocardiographic waveforms was found to estimate two cardiophysiologic variables, the constant (a) and the slope (b) values, reflecting the dynamic change of QT during physiotherapy effort. RESULTS: Only for the subgroup of patients who sustained a deep brain lesion did the motor items in the FIM instrument on admission and discharge scores have a statistically significant relationship with the slope variable (b) and an inverse statistically significant relationship with the constant variable (a). CONCLUSIONS: Deep brain infarction seems to result in a significant dysfunction of the autonomic nervous system, manifesting itself as distorted dynamic behavior of the QT interval and with impaired functional performance.

Aged↗
PubMed2002

Induced current impedance technique for monitoring brain cryosurgery in a two-dimensional model of the head.

A fast and robust finite volume solver of the two-dimensional induced current electrical impedance forward problem was developed. The numerical solver was validated by comparison with an existing analytical solution for a symmetrical geometry case, showing an accuracy of 0.07%. The solver was used to theoretically examine the sensitivity of the induced current impedance technique for the medical procedure of monitoring brain cryosurgery. The simulation was performed using a two-dimensional approximation of otherwise realistic geometry model of the head with different ice-ball sizes, simulating the expansion of the frozen lesion. The sensitivity of the scalp potential to the ice-ball size was found to be 53 x 10(-4) (relative scalp potential mm(-2)).

Biomedical Engineering↗
PubMedDate not supplied

Monitoring lung resistivity changes in congestive heart failure patients using the bioimpedance technique.

The feasibility of a novel, dedicated system for monitoring lung resistivity in congestive heart failure patients, implementing a hybrid approach of the bioimpedance technique, was assessed in this preliminary study. Thirty-three healthy volunteers and 34 congestive heart failure patients were measured with the PulmoTrace system (CardioInspect, Tel Aviv University, Tel Aviv, Israel) during tidal respiration, and the ability to monitor the respective lung resistivity values was assessed. Mean left and right lung resistivity values of 1205+/-163 and 1200+/-165 ohm.cm for the control group and 888+/-193 and 943+/-187 ohm.cm for the congestive heart failure group were found, indicating a significant (p<2.10(-7)) difference between the two groups. The results of long-term monitoring of two patients during medical treatment are also shown. This hybrid approach system is believed to improve diagnostic capabilities and help physicians to better adjust medication dosage on a frequent basis.

Aged↗
PubMedDate not supplied

A three-dimensional numerical fluid dynamic model of antigen-antibody surface adsorption on piezoelectric immunosensors.

A piezoelectric crystal is a unit that changes its frequency in parallel with a change in its mass. This characteristic is exploited in designing flow cell-based immunosensors for detecting the concentration of antibodies in liquid samples. In the present study, computational fluid dynamic techniques are used to optimize the antigen-antibody binding process on an electrode surface placed on the base of a conical flow cell. The geometry optimization of the flow cell was determined to minimize the test time. This time is needed for the electrode to be saturated by the antibody, a process that requires the maximization of the adsorption rate and be accomplished by increasing the shear rate in the vicinity of the electrode. To validate the numerical model and to determine its parameters, experiments were carried out using an identical flow cell. In the experiments, the system did not reach saturation within an acceptable time frame, therefore, the model parameters were determined based on the unsaturated state. The experimental results confirmed the applicability of numerical simulations in predicting the effect of changing the inlet section area of the flow cells, proving the computational model to be very valuable in designing immunosensors based on flow cells.

Adsorption↗