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Page 1. Proc. Annu. Int. Conf. IEEE Eng. Med. Biol. Soc., Philadelphia, PA, Nov. 14, 1990 1060 PERIODIC VARIATIONS IN THE ELECTROTACTILE SENSATION THRESHOLD Kurt A. Kaczmarek1,3, John G. Webster1,4, and Robert G. Radwin1,2 ...
We are using a Hercules (model #F4-4R, 100 psi) pressure sensor to measure the pressure between the foot and shoe. An interface circuit converts the capacitance change into voltage. Over the pressure range from 0 to 1300 kPa, the... more
We are using a Hercules (model #F4-4R, 100 psi) pressure sensor to measure the pressure between the foot and shoe. An interface circuit converts the capacitance change into voltage. Over the pressure range from 0 to 1300 kPa, the capacitance changes from 275 to 580 pF. A 555 timer circuit converts the capacitance into a frequency range from 30 to 63 kHz. A phase-locked loop (PLL) converts this frequency to voltage from 0 to 5 V, which is then filtered using a first-order, low-pass filter, having a corner frequency of 20 Hz to reduce the ripple to 10 mV. The sensor's hysteresis is about 8 percent at 40 degrees Celsius (C) and 12 percent at 20 degrees C. The sensor has a maximal nonlinearity of 8 percent and a worst-case nonrepeatibility of 7 percent. Its temperature coefficient is -0.147 percent per degree C. Its spatial sensitivity decreases nonlinearly from 1 to 0.17 from the center towards the periphery. The sensitivity of the system is 2.77 mV/kPa and the temperature drift is +0.53 percent per degree C. We monitor the pressure at 7 locations under each foot (the rear and the front heel, great toe, and 4 of the 5 metatarsal heads). A portable data-acquisition system permits continuous monitoring for 7 minutes. Test results for pressure distribution for normal walk and run are presented. Results are useful when studying normal and abnormal gait, and for possibly providing feedback (sensory substitution) to diabetic patients with insensate feet in order to help them dynamically adjust pressure distribution under their feet.
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A portable data acquisition system using pressure sensors, built to measure pressures between bony prominences of each foot and the shoe, is described. Data acquisition algorithms for extracting peak pressure, area under the curve, heel... more
A portable data acquisition system using pressure sensors, built to measure pressures between bony prominences of each foot and the shoe, is described. Data acquisition algorithms for extracting peak pressure, area under the curve, heel strike to pushoff time, and center of pressure are discussed. Sample results of an analysis from 2-h tests on ten subjects are presented, revealing interesting
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ABSTRACT
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In this paper, we summarize our experiences as advisors supervising biomedical engineering design projects in the design backbone of our curriculum, the six-semester design course sequence required for all biomedical engineering majors at... more
In this paper, we summarize our experiences as advisors supervising biomedical engineering design projects in the design backbone of our curriculum, the six-semester design course sequence required for all biomedical engineering majors at the University of Wisconsin-Madison.
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The performance of the Interlink force sensor for measuring force under insensate feet of diabetics has been tested. Embedded in a rubber insole, seven of these sensors measure the force under high-pressure points on the sole of the foot... more
The performance of the Interlink force sensor for measuring force under insensate feet of diabetics has been tested. Embedded in a rubber insole, seven of these sensors measure the force under high-pressure points on the sole of the foot during walking. In sensor operation, force compresses a conductive polymer film against a printed conductive pattern and hence decreases the resistance of the sensor. Using the described sensor and electronics, an umbilical system has been constructed to monitor the pressure under the center of the heel, the five metatarsal heads, and the big toe of each foot. The response of the sensor under the center of the heel for two consecutive steps is shown.
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The authors are using basket electrodes to validate electrical-thermal computer models of RF catheter ablation for the cure of tachycardias. They have measured electrical characteristics of the basket electrode and shown that accuracy... more
The authors are using basket electrodes to validate electrical-thermal computer models of RF catheter ablation for the cure of tachycardias. They have measured electrical characteristics of the basket electrode and shown that accuracy degrades above 100 kHz. They present some preliminary measurements and suggest considerations for the validation of the model for RF catheter ablation
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... Punit Prakash*(1), Mark C. Converse(2), John G. Webster(1) and David M. Mahvi(2 ... and shape of the ablation zone, as well as antenna efficiency, using a finite element (FE) model. ... we used NSGA-II, a nondominated, sorting genetic... more
... Punit Prakash*(1), Mark C. Converse(2), John G. Webster(1) and David M. Mahvi(2 ... and shape of the ablation zone, as well as antenna efficiency, using a finite element (FE) model. ... we used NSGA-II, a nondominated, sorting genetic algorithm [6]. A nondominated solution is one ...
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ABSTRACT The authors have developed a portable, microprocessor-based data-acquisition system to measure pressures between the foot and shoe of ambulatory subjects. They attached seven pressure sensors to the surface of each insole of a... more
ABSTRACT The authors have developed a portable, microprocessor-based data-acquisition system to measure pressures between the foot and shoe of ambulatory subjects. They attached seven pressure sensors to the surface of each insole of a pair of extra-deep shoes. They were located under the center of the heel, the five metatarsal heads, and the big toe of each foot. This system continuously collects raw pressure data for seven min at a 20 Hz sample frequency per channel. The authors then dump the data to an IBM PC for postprocessing and display. The acquisition, postprocessing, and display equipment is described, and some measurement results are reported.< >
The authors have characterized the performance of the commercially available Interlink pressure sensor. The sensor costs less than $1. It is 0.25-mm thick, is light and flexible, and can be customized for a wider range of applications.... more
The authors have characterized the performance of the commercially available Interlink pressure sensor. The sensor costs less than $1. It is 0.25-mm thick, is light and flexible, and can be customized for a wider range of applications. The resistance-versus-pressure characteristic of the sensor is logarithmic. The operating range is from 0 to 2 MPa. The hysteresis is 8% and the
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Static image reconstruction in electrical impedance tomopphy (EIT) using iterative algorithms requires a large computation time. We developed an improved NewtonRaphson (N-R) method which is more efficient, robust, and easily... more
Static image reconstruction in electrical impedance tomopphy (EIT) using iterative algorithms requires a large computation time. We developed an improved NewtonRaphson (N-R) method which is more efficient, robust, and easily parallelizable. In order to check the feasibility of parallel computation in EIT, we implemented the algorithm on a parallel computer system. The results show a reduction in the computation time
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A three-dimensional finite element model was developed using ANSYS, a commercial finite element analysis software. The effect of temperature-dependent electrical and thermal conductivities to the FE model which incorporated cardiac... more
A three-dimensional finite element model was developed using ANSYS, a commercial finite element analysis software. The effect of temperature-dependent electrical and thermal conductivities to the FE model which incorporated cardiac muscle, blood, electrode and catheter body, was investigated in this study. Computer simulations were performed to calculate the temperature distribution during RF ablation. The authors compared the results of the
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ABSTRACT The authors measured impedance of swine aorta from 10 Hz to 500 kHz. The resistivity is 184 Ω·cm at low frequencies, it starts to decrease above 10 kHz and becomes 149 Ω·cm at 500 kHz
We measured ventilation from infants by impedance plethysmography (IP) and respiratory inductance plethysmography (RIP) on the ribcage (re) and abdomen (abd) in order to characterize sensor performance during unrestrained sleep. We... more
We measured ventilation from infants by impedance plethysmography (IP) and respiratory inductance plethysmography (RIP) on the ribcage (re) and abdomen (abd) in order to characterize sensor performance during unrestrained sleep. We recorded airflow using a pneumotachometer (PT) attached to a standard infant mask gently sealed over the face. For each subject, we recorded spontaneous respiratory activity for one hour, and
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We designed a spandex tank top with dry electrodes for continuous electrocardiogram (ECG) recording. This pilot study determined the best fabric, the best electrode types, sizes, and locations. Optimal electrodes provide high signal to... more
We designed a spandex tank top with dry electrodes for continuous electrocardiogram (ECG) recording. This pilot study determined the best fabric, the best electrode types, sizes, and locations. Optimal electrodes provide high signal to artifact ratio (SAR) and reliability by meeting the following criteria: 1) low baseline shift, 2) high adhesion, 3) good physical stability, 4) large effective area, 5) thin with high flexibility (Luo et al 1992). We compared electrodes from three main groups: Ag/AgCl gel electrode, commercial conductive rubber and foam-metal based electrodes. Ag/AgCl gel electrodes are easy to apply, make good body contact and do not slip during the course of an experiment. We found that higher SARs are obtained when electrode area is increased (40 mm diameter) and the two dry measurement electrodes are located on convex areas (over chest muscle) rather than concave areas (over sternum), so the spandex will apply light pressure to the dry electrode to yield good elec...
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Hepatic resection is the current standard treatment for hepatic malignancies. During hepatic resection part of the liver containing the tumor is surgically removed. This type of surgery is associated with high blood loss of approximately... more
Hepatic resection is the current standard treatment for hepatic malignancies. During hepatic resection part of the liver containing the tumor is surgically removed. This type of surgery is associated with high blood loss of approximately 1 L. Blood loss is associated with increased complication rates, prolonged hospital stay and reduced patient survival, especially when transfusion is required. We present a device that allows coagulation of a plane of tissue 1 to 2 cm wide, including coagulation of large vessels. This enables reduction of blood loss to a minimum by performing surgery along the coagulated tissue plane. The device consists of a linear array of radiofrequency (RF) electrodes 1.5 cm apart. By application of RF current in bipolar mode between two adjacent electrodes, temperatures close to 100 degrees C are obtained in-between electrodes enabling coagulation of large vessels. Rapid switching of applied current between all adjacent electrode pairs enables rapid heating of ...
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ABSTRACT A 4×4 array of four quad (5 mm×5 mm) Interlink conductive polymer pressure sensors was designed. The array was embedded in a shoe insole under the second metatarsal head of a subject. The sensors were calibrated, and a... more
ABSTRACT A 4×4 array of four quad (5 mm×5 mm) Interlink conductive polymer pressure sensors was designed. The array was embedded in a shoe insole under the second metatarsal head of a subject. The sensors were calibrated, and a microprocessor-based portable data-acquisition system was used to monitor the pressure distribution under the second metatarsal head during normal gait. A center-of-pressure algorithm was used to estimate the maximum metatarsal head movement for one subject. A value of 5 mm was obtained, with a maximum error of ±1.5 mm. Hence the diameter of the sensor must be at least 7 mm to cover the peak pressure area under the metatarsal heads
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The finite element method (FEM) has been used to simulate cardiac and hepatic radiofrequency (RF) ablation. The FEM allows modeling of complex geometries that cannot be solved by analytical methods or finite difference models. In both... more
The finite element method (FEM) has been used to simulate cardiac and hepatic radiofrequency (RF) ablation. The FEM allows modeling of complex geometries that cannot be solved by analytical methods or finite difference models. In both hepatic and cardiac RF ablation a common control mode is temperature-controlled mode. Commercial FEM packages don't support automating temperature control. Most researchers manually control the applied power by trial and error to keep the tip temperature of the electrodes constant. We implemented a PI controller in a control program written in C++. The program checks the tip temperature after each step and controls the applied voltage to keep temperature constant. We created a closed loop system consisting of a FEM model and the software controlling the applied voltage. The control parameters for the controller were optimized using a closed loop system simulation. We present results of a temperature controlled 3-D FEM model of a RITA model 30 elect...
Research Interests: Algorithms, Artificial Intelligence, Biomedical Engineering, Optimal Control, Finite element method, and 20 moreAutomatic Control, Finite Element Analysis, Computer assisted orthopaedic surgery, Humans, Computer Simulation, Animals, Heart, Temperature, Feedback, Closed Loop Control, System Simulation, Body Temperature, Radiofrequency Ablation, Analytical Method, Finite Element Model, Finite Difference, Temperature Control, Radiofrequency, Catheter ablation, and PI Controller
An axisymmetric finite element method (FEM) model was employed to demonstrate important techniques used in the design of antennas for hepatic microwave ablation (MWA). To effectively treat deep-seated hepatic tumors, these antennas should... more
An axisymmetric finite element method (FEM) model was employed to demonstrate important techniques used in the design of antennas for hepatic microwave ablation (MWA). To effectively treat deep-seated hepatic tumors, these antennas should produce a highly localized specific absorption rate (SAR) pattern and be efficient radiators at approved generator frequencies. As an example, a double slot choked antenna for hepatic MWA was designed and implemented using FEMLABtrade mark 3.0. This paper emphasizes the importance of factors that can affect simulation accuracy, which include boundary conditions, the dielectric properties of liver tissue, and mesh resolution.
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The majority of the focus related to the modernization of medical records is placed on developed countries. However, developing countries are also progressing from paper-based records to electronic records. The requirements of their... more
The majority of the focus related to the modernization of medical records is placed on developed countries. However, developing countries are also progressing from paper-based records to electronic records. The requirements of their systems can be dramatically different from those of the developed world. This paper describes briefly the benefits of EMRs in developing countries. It focuses on the basic EMR information, including types of EMRs, components of EMRs, and already existing case studies, in order to establish which EMR systems would be feasible and effective for specific situations.
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Engineering is becoming a more globally aware discipline that is revolutionizing the way individuals interact internationally. Engineering World Health (EWH) - Madison Chapter is a student-initiated organization that has developed... more
Engineering is becoming a more globally aware discipline that is revolutionizing the way individuals interact internationally. Engineering World Health (EWH) - Madison Chapter is a student-initiated organization that has developed opportunities to facilitate both local and global engineering education. Through EWH - Madison Chapter student-initiated activities, this organization has developed an interface between Traditional, Technical, and Translational education mediums. This study attests to the development of global engineering programs in the context of biomedical applications.
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Many people in developing countries cannot afford or rely on certain modes of electricity. We establish the reasonability of relying on lead-acid batteries, 9 V alkaline batteries, and lithium-ion batteries for charging low-voltage... more
Many people in developing countries cannot afford or rely on certain modes of electricity. We establish the reasonability of relying on lead-acid batteries, 9 V alkaline batteries, and lithium-ion batteries for charging low-voltage medical equipment. Based on the research and tests we conducted, we determined that using these battery types to charge medical devices truly is a reasonable solution.
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We need a sensor to measure the convective heat transfer coefficient during ablation of the heart or liver. We built a minimally invasive instrument to measure the in vivo convective heat transfer coefficient, h in animals, using a... more
We need a sensor to measure the convective heat transfer coefficient during ablation of the heart or liver. We built a minimally invasive instrument to measure the in vivo convective heat transfer coefficient, h in animals, using a Wheatstone-bridge circuit, similar to a hot-wire anemometer circuit. One arm is connected to a steerable catheter sensor whose tip is a 1.9 mm x 3.2 mm thin film resistive temperature detector (RTD) sensor. We used a circulation system to simulate different flow rates at 39 degrees C for in vitro experiments using distilled water, tap water and saline. We heated the sensor approximately 5 degrees C above the fluid temperature. We measured the power consumed by the sensor and the resistance of the sensor during the experiments and analyzed these data to determine the value of the convective heat transfer coefficient at various flow rates. From 0 to 5 L/min, experimental values of h in W/(m2.K) were for distilled water 5100 to 13000, for tap water 5500 to 1...
Research Interests: Biomedical Engineering, Water, Electrochemistry, Liver, Calibration, and 15 moreAnimals, Thin Film, Platinum, Temperature, Thermal Conductivity, Myocardium, Distilled Water, Convective Heat Transfer, Catheter ablation, Flow Rate, Minimally Invasive, Equipment Design, Electric Impedance, Biosensing Techniques, and *Hot Temperature
Medical devices intended for use in developing countries have certain differences compared to those used in developed countries. Thus, many of the medical devices built for developed countries may not be compatible with the environment in... more
Medical devices intended for use in developing countries have certain differences compared to those used in developed countries. Thus, many of the medical devices built for developed countries may not be compatible with the environment in developing countries. In this specific case study we consider the respiratory problems in India and elucidate design constraints and approaches for the development of medical devices to diagnose them.
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The use of compound electrodes to improve the conditioning and sensitivity of an electrical impedance tomography imaging system is described. Effects of electrode-skin contact impedance are discussed and a model is proposed. Reconstructed... more
The use of compound electrodes to improve the conditioning and sensitivity of an electrical impedance tomography imaging system is described. Effects of electrode-skin contact impedance are discussed and a model is proposed. Reconstructed static images from phantoms are shown
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Magnetic coupling between chest and abdominal bands modulates desired oscillation frequencies in a two-channel inductive plethysmograph. When modulation is excessive, kqwy locking occurs and independent measurea €rom both channels cannot... more
Magnetic coupling between chest and abdominal bands modulates desired oscillation frequencies in a two-channel inductive plethysmograph. When modulation is excessive, kqwy locking occurs and independent measurea €rom both channels cannot be made. We show that as the chest and abdominal band oscillator frequencies are sufficiently separated, we decrease modulation and avoid frequency locking.
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Three methods of creating large thermal lesions with cool-tip cluster electrodes were compared. Three cluster electrodes were arranged 4 cm apart in a triangular array. Eight lesions were created ex vivo in fresh bovine liver (from a... more
Three methods of creating large thermal lesions with cool-tip cluster electrodes were compared. Three cluster electrodes were arranged 4 cm apart in a triangular array. Eight lesions were created ex vivo in fresh bovine liver (from a butcher) with each method: sequential ablation (three electrodes, 12 minutes each); simultaneous activation of electrodes (12 minutes); and rapid switching of power between electrodes (12 minutes), for which an electronic computer-controlled switch was developed. For sequential, rapid switching, and simultaneous methods, lesion volumes were 137.5 cm(3)+/- 22.2, 116.4 cm(3)+/- 15.2, and 22.3 cm(3)+/- 6.4 (P < .05), respectively, and final temperatures at lesion center were 80 degrees C +/- 5, 97 degrees C +/- 8, and 41 degrees C +/- 3 (P < .001), respectively. Because of electrical interference between electrodes, simultaneous method led to little heating at the center between the electrodes and created small discontinuous lesions. Rapid switching created large round lesions by employing multiple electrodes concurrently, which substantially reduced treatment time and resulted in more effective heating between electrodes.
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Research Interests: Biomedical Engineering, Humans, Animals, Physiological, Medical Physiology, and 11 moreTemperature Dependence, Reproducibility of Results, Specific Heat, Electrodes, Physical Model, Electricity Generation, Equipment Design, Electrical And Electronic Engineering, Thermometers, *Hot Temperature, and Tissue Specificity
Research Interests: Biomedical Engineering, Humans, Liver, Physiological, Medical Device, and 11 moreMedical Physiology, Dielectric Properties, Diathermy, Temperature measurement, Microwaves, Specific Heat, Thermal Properties, Materials Testing, Electrical And Electronic Engineering, *Hot Temperature, and Specific absorption rate (SAR)
We have designed and built an ultrasonic time-of-flight system to measure the three-dimensional coordinates of up to three moving emitters. These emitters are fixed on the hand and arm of a human subject or on a hand-held stylus, to... more
We have designed and built an ultrasonic time-of-flight system to measure the three-dimensional coordinates of up to three moving emitters. These emitters are fixed on the hand and arm of a human subject or on a hand-held stylus, to provide information concerning motor control. Three stationary receivers are suspended above the experimental space and provide three diagonal distances which are converted to x, y and z coordinates. The sampling rate for one emitter is 200-400 Hz, depending on the nature of the experiment. Multiple emitters are time-multiplexed. The piezoelectric resonator emitter is pulsed with 200 V for 12 microseconds of each cycle and rings at 40 kHz with a Q factor of four. The piezoelectric resonator receiver drives circuitry with a gain of 500 and a bandwidth of 60 kHz. The system provided highly linear results with a repeatability of +/- 1.64 mm and a resolution of 0.7 mm.
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The TaserX26 output current waveform consists of an arc phase and a stimulation phase, which is responsible for electromuscular stimulation. We modeled the current discharge during the stimulation phase using a simplified overdamped... more
The TaserX26 output current waveform consists of an arc phase and a stimulation phase, which is responsible for electromuscular stimulation. We modeled the current discharge during the stimulation phase using a simplified overdamped series R-L-C circuit. The model provides a reasonable approximation to the TaserX26 current waveform and explains the changes in the peak current and rise and fall time constants due to load variations. We simulated a physiological load using a 0.2% saline solution in a 75 × 30 × 17.2 cm fish tank to represent a supine human torso with resistivity similar to skeletal muscles. The peak current and load resistance varied more with the depth of the Taser darts in saline than with their distance of separation. Experiments performed on three pigs confirmed the decrease in resistance and increase in current with the depth of the Taser dart in the body. An R-C circuit with a time constant of about 2 ms was used to measure the variation of the Taser in stimulating cardiac cells. The Taser is 2.05 times more likely to stimulate the cardiac cell when the darts penetrate 9 mm into the load as compared to when they were just touching the load.