Scholars@Duke
Patrick D. Wolf

Patrick D. Wolf

Associate Professor Emeritus of Biomedical Engineering
Biomedical Engineering
patrick.wolf@duke.edu
Box 90281, Durham, NC 27708-0281
Rm. 276, Hudson Annex, Durham, NC 27708

Selected Publications

3-D Ultrasound Imaging Using Helicoid Array Transducers.

Journal Article IEEE transactions on ultrasonics, ferroelectrics, and frequency control · March 2021 Real-time 3-D intracardiac echocardiography (ICE) can enable faster imaging of surfaces orthogonal to the transducer, such as the pulmonary vein (PV) antra and cardiac valve annuli. However, the requirement for a 2-D grid of individually wired elements mak ... Full text Cite

Measuring Intraventricular Pressure Using Ultrasound Elastography.

Journal Article Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine · May 2019 ObjectivesIntraventricular pressure (IVP) is one of the most important measurements for evaluating cardiac function, but this measurement is not currently easily assessable in the clinic. The primary reason for this is the absence of a noninvasive ... Full text Cite

Assessment of Diastolic Function Using Ultrasound Elastography.

Journal Article Ultrasound in medicine & biology · March 2018 Shear wave elasticity imaging (SWEI) is a novel ultrasound elastography technique for assessing tissue stiffness. In this study, we investigate the potential of SWEI for providing diastolic functional assessment. In 11 isolated rabbit hearts, pressure-volu ... Full text Cite

Scanned 3-D Intracardiac ARFI and SWEI for Imaging Radio-Frequency Ablation Lesions.

Journal Article IEEE transactions on ultrasonics, ferroelectrics, and frequency control · July 2017 Radio-frequency ablation (RFA) is used to locally disrupt electrical propagation in myocardium and treat arrhythmias, and direct visualization of ablation lesions by acoustic radiation force methods may benefit RFA procedures. This paper compares four imag ... Full text Cite

Quantifying Myocardial Contractility Changes Using Ultrasound-Based Shear Wave Elastography.

Journal Article Journal of the American Society of Echocardiography : official publication of the American Society of Echocardiography · January 2017 BackgroundMyocardial contractility, a significant determinant of cardiac function, is valuable for diagnosis and evaluation of treatment in cardiovascular disorders including heart failure. Shear wave elasticity imaging (SWEI) is a newly developed ... Full text Cite

Characterization of catheter motion in intracardiac echocardiography (ICE) elastography imaging

Conference IEEE International Ultrasonics Symposium, IUS · November 1, 2016 Momentum created by a high intensity acoustic wave emitted in intracardiac echocardiography (ICE) Acoustic Radiation Force Impulse (ARFI) imaging sequences is absorbed by the backing material of the catheter causing a kickback motion. This study was design ... Full text Cite

A Comparison of Acoustic Radiation Force-Derived Indices of Cardiac Function in the Langendorff Perfused Rabbit Heart.

Journal Article IEEE transactions on ultrasonics, ferroelectrics, and frequency control · September 2016 In the past decade, there has been an increased interest in characterizing cardiac tissue mechanics utilizing newly developed ultrasound-based elastography techniques. These methods excite the tissue mechanically and track the response. Two frequently used ... Full text Cite

The Evolution of Tissue Stiffness at Radiofrequency Ablation Sites During Lesion Formation and in the Peri-Ablation Period.

Journal Article Journal of cardiovascular electrophysiology · September 2015 IntroductionElastography imaging can provide radiofrequency ablation (RFA) lesion assessment due to tissue stiffening at the ablation site. An important aspect of assessment is the spatial and temporal stability of the region of stiffness increase ... Full text Cite

Ultrasound shear wave elasticity imaging quantifies coronary perfusion pressure effect on cardiac compliance.

Journal Article IEEE transactions on medical imaging · February 2015 Diastolic heart failure (DHF) is a major source of cardiac related morbidity and mortality in the world today. A major contributor to, or indicator of DHF is a change in cardiac compliance. Currently, there is no accepted clinical method to evaluate the co ... Full text Cite

Feasibility of near real-time lesion assessment during radiofrequency catheter ablation in humans using acoustic radiation force impulse imaging.

Journal Article J Cardiovasc Electrophysiol · December 2014 BACKGROUND: Visual confirmation of radiofrequency ablation (RFA) lesions during clinical cardiac ablation procedures could improve procedure efficacy, safety, and efficiency. It was previously shown that acoustic radiation force impulse (ARFI) imaging can ... Full text Link to item Cite

M-mode ARFI imaging demonstrates the effect of coronary perfusion on cardiac stiffness

Conference IEEE International Ultrasonics Symposium, IUS · October 20, 2014 Myocardial stiffness is an important clinical indicator of cardiac function. One of the contributors to stiffness in the heart is coronary perfusion. The interaction between cardiac tissue and coronary vasculature has been studied for several decades using ... Full text Cite

Feasibility of using a generalized-Gaussian Markov random field prior for Bayesian speckle tracking of small displacements

Journal Article IEEE International Ultrasonics Symposium, IUS · October 20, 2014 Accurate displacement estimation can be a challenging task in acoustic radiation force elastography, where signal decorrelation can degrade the ability of a normalized cross-correlation (NCC) estimator to characterize the tissue response. In this work, we ... Full text Cite

Double Ring Array Catheter for In Vivo Real-Time 3D Ultrasound.

Journal Article Ultrasonic imaging · July 2014 We developed new forward-viewing matrix transducers consisting of double ring arrays of 118 total PZT elements integrated into catheters used to deploy medical interventional devices. Our goal is 3D ultrasound guidance of medical device implantation to red ... Full text Cite

The feasibility of myocardial infarct visualization using atrial kick induced strain (AKIS) contrast.

Journal Article Ultrasound Med Biol · June 2014 The most common mechanical measure of the heart integrates ventricular strain between end-diastole and end-systole in order to provide a measure of contraction. Here an approach is described for estimating a correlate to local passive mechanical properties ... Full text Link to item Cite

Contrast in intracardiac acoustic radiation force impulse images of radiofrequency ablation lesions.

Journal Article Ultrason Imaging · April 2014 We have previously shown that intracardiac acoustic radiation force impulse (ARFI) imaging visualizes tissue stiffness changes caused by radiofrequency ablation (RFA). The objectives of this in vivo study were to (1) quantify measured ARFI-induced displace ... Full text Open Access Link to item Cite

Implanted electrodes for multi-month EEG.

Journal Article Annu Int Conf IEEE Eng Med Biol Soc · 2014 An implanted electroencephalogram (EEG) recorder would help diagnose infrequent seizure-like events. A proof-of-concept study quantified the electrical characteristics of the electrodes planned for the proposed recorder. The electrodes were implanted in an ... Full text Link to item Cite

The effect of acute coronary perfusion change on cardiac function measured by Shear Wave Elasticity Imaging.

Conference Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference · January 2014 The possibility of measuring cardiac function noninvasively has generated wide interest in elastography imaging techniques. Shear Wave Elasticity Imaging (SWEI) is an ultrasound-based elastography technique used to measure stiffness of tissues. While this ... Full text Cite

Acute and chronic myocardial infarct differentiation using atrial kick induced strain (AKIS) imaging

Journal Article IEEE International Ultrasonics Symposium, IUS · December 1, 2013 We have previously shown that the passive ventricular stretch induced during the active filling phase of the heart can be used to make images correlated to the passive mechanical stiffness of the ventricles. In the initial feasibility study chronic infarct ... Full text Cite

Three-dimensional fusion of Shear Wave Imaging and electro-anatomical mapping for intracardiac radiofrequency ablation monitoring

Journal Article IEEE International Ultrasonics Symposium, IUS · December 1, 2013 Electroanatomical Mapping (EAM) provides electrophysiologists with a three-dimensional visualization of endocardial geometry and electrical activity, used to guide transcatheter ablation (TCA) treatment of arrhythmia. Acoustic Radiation Force Impulse (ARFI ... Full text Cite

Intracardiac acoustic radiation force impulse (ARFI) and shear wave imaging in pigs with focal infarctions.

Journal Article IEEE transactions on ultrasonics, ferroelectrics, and frequency control · August 2013 Four pigs, three with focal infarctions in the apical intraventricular septum (IVS) and/or left ventricular free wall (LVFW), were imaged with an intracardiac echocardiography (ICE) transducer. Custom beam sequences were used to excite the myocardium with ... Full text Open Access Cite

Confirmation of cardiac radiofrequency ablation treatment using intra-procedure acoustic radiation force impulse imaging

Conference IEEE International Ultrasonics Symposium, IUS · December 1, 2012 Recurrence of atrial fibrillation after transcatheter ablation (TCA) is common because there is no imaging modality that can visually confirm the presence of radiofrequency ablation (RFA) lesions. We have previously shown that acoustic radiation force impu ... Full text Cite

Feasibility and safety of transthoracic cardiac acoustic radiation force impulse imaging methods

Conference IEEE International Ultrasonics Symposium, IUS · December 1, 2012 This work examines clinical feasibility of using non-invasive transthoracic echocardiography techniques to visualize temporal variations of stiffness through the cardiac cycle using acoustic radiation force impulse (ARFI) imaging. © 2012 IEEE. ... Full text Cite

Intracardiac ARF-driven shear wave velocimetry to estimate regional myocardial stiffness and contractility in pigs with focal infarctions

Conference IEEE International Ultrasonics Symposium, IUS · December 1, 2012 Four pigs, three with focal infarctions in the apical intraventricular septum (IVS) and/or left ventricular free wall (LVFW), were imaged with an intracardiac echocardiography (ICE) transducer. Custom beam sequences were used to excite the myocardium with ... Full text Cite

Intracardiac acoustic radiation force impulse imaging: a novel imaging method for intraprocedural evaluation of radiofrequency ablation lesions.

Journal Article Heart Rhythm · November 2012 BACKGROUND: Arrhythmia recurrence after cardiac radiofrequency ablation (RFA) for atrial fibrillation has been linked to conduction through discontinuous lesion lines. Intraprocedural visualization and corrective ablation of lesion line discontinuities cou ... Full text Open Access Link to item Cite

Intracardiac echocardiography measurement of dynamic myocardial stiffness with shear wave velocimetry.

Journal Article Ultrasound in medicine & biology · July 2012 Acoustic radiation force (ARF)-based methods have been demonstrated to be a viable tool for noninvasively estimating tissue elastic properties, and shear wave velocimetry has been used to measure quantitatively the stiffening and relaxation of myocardial t ... Full text Cite

Acoustic radiation force impulse imaging of mechanical stiffness propagation in myocardial tissue.

Journal Article Ultrasonic imaging · July 2012 Acoustic radiation force impulse (ARFI) imaging has been shown to be capable of imaging local myocardial stiffness changes throughout the cardiac cycle. Expanding on these results, the authors present experiments using cardiac ARFI imaging to visualize and ... Full text Cite

Direct in vivo myocardial infarct visualization using 3D ultrasound and passive strain contrast

Conference IEEE International Ultrasonics Symposium, IUS · December 1, 2011 An approach for myocardial elastography is presented for infarct visualization. Infarcts are visualized using passive strain in the ventricles induced by atrial contraction. Results are compared against ARFI and delay-enhanced contrast MR. © 2011 IEEE. ... Full text Cite

Intracardiac shear wave velocimetry using Acoustic Radiation Force (ARF) excitations: In vivo results

Journal Article IEEE International Ultrasonics Symposium, IUS · December 1, 2011 Acoustic Radiation Force (ARF)-driven shear wave velocimetry is a validated way of quantitatively measuring tissue elasticity. Open-chest velocimetry experiments have been able to measure regional myocardial contractility, a potentially useful diagnostic p ... Full text Cite

Dual-mode IVUS transducer for image-guided brain therapy: preliminary experiments.

Journal Article Ultrasound Med Biol · October 2011 In this study, we investigated the feasibility of using 3.5-Fr intravascular ultrasound (IVUS) catheters for minimally-invasive, image-guided hyperthermia treatment of tumors in the brain. Feasibility was demonstrated by: (1) retro-fitting a commercial 3.5 ... Full text Link to item Cite

Excitation properties of the right cervical vagus nerve in adult dogs.

Journal Article Experimental neurology · January 2011 Vagus nerve stimulation (VNS) is an approved treatment for epilepsy and depression, and it is currently under investigation for applications in Alzheimer's disease, anxiety, heart failure, and obesity. However, the mechanism(s) by which VNS has its effects ... Full text Cite

Planar saline bath phantom of the Rush head model.

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference · January 2011 The Rush head model is an approximation of the volume conducting properties of the human head. A planar saline bath phantom was developed to simulate the key properties of the Rush head model while creating a testing platform for implantable neural devices ... Full text Cite

Selective control of physiological responses by temporally-patterned electrical stimulation of the canine vagus nerve.

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference · January 2011 Vagus nerve stimulation (VNS) is effective for treating epilepsy and depression, and has emerging indications for anxiety and heart failure. However, stimulation-evoked side effects remain a challenge for long-term compliance. We investigated the feasibili ... Full text Cite

Intracranial dual-mode IVUS transducer for image-guided brain therapypreliminary experiments

Journal Article Proceedings - IEEE Ultrasonics Symposium · December 1, 2010 In this study, we investigated the feasibility of using 3.5-Fr IVUScatheters for minimally-invasive, image-guided hyperthermia treatment of tumorsin the brain. Feasibility is demonstrated in two ways: 1) by fitting a 3.5-FrIVUS catheter with a 5 × 0.5 × 0. ... Full text Cite

Ring array transducers for real-time 3D ultrasound guidance of prostheticheart valve deployment

Journal Article Proceedings - IEEE Ultrasonics Symposium · December 1, 2010 We have previously developed 2D ring array transducers for real-timevolumetric imaging guidance of minimally invasive procedures. These transducerswere integrated with an 11 French catheter sheath of a Cook Medical, Inc. venacava filter deployment kit. We ... Full text Cite

Intracardiac measurements of elasticity using Acoustic Radiation ForceImpulse (ARFI) methods: Temporal and spatial stability of shear wave velocimetry

Journal Article Proceedings - IEEE Ultrasonics Symposium · December 1, 2010 Acoustic Radiation Force Impulse (ARFI) methods have been validated formeasuring tissue elastic properties, with shear wave velocimetry emerging as aquantitative way to measure stiffness. Using ultrasound to interrogate cardiacelasticity holds promise for ... Full text Cite

Parametric pressure-volume analysis and acoustic radiation force impulse imaging of left ventricular function

Conference Proceedings - IEEE Ultrasonics Symposium · December 1, 2010 Extensive research has been devoted to the quantification of left ventricular (LV) function via an elasticity metric known as elastance. Similar to a stress-strain relation, yielding stiffness, myocardial elastance is measured from the pressure-volume (PV) ... Full text Cite

An in vitro assessment of acoustic radiation force impulse imaging for visualizing cardiac radiofrequency ablation lesions.

Journal Article J Cardiovasc Electrophysiol · May 2010 INTRODUCTION: Lesion placement and transmurality are critical factors in the success of cardiac transcatheter radiofrequency ablation (RFA) treatments for supraventricular arrhythmias. This study investigated the capabilities of catheter transducer based a ... Full text Link to item Cite

Optimizing the automatic selection of spike detection thresholds using a multiple of the noise level.

Journal Article Medical & biological engineering & computing · September 2009 Thresholding is an often-used method of spike detection for implantable neural signal processors due to its computational simplicity. A means for automatically selecting the threshold is desirable, especially for high channel count data acquisition systems ... Full text Cite

Intracranial catheter for integrated 3D ultrasound imaging & hyperthermia: Feasibility study

Conference AIP Conference Proceedings · July 21, 2009 In this study, we investigated the feasibility of an intracranial catheter transducer capable of real-time 3D (RT3D) imaging and ultrasound hyperthermia, for application in the visualization and treatment of tumors in the brain. We designed and constructed ... Full text Cite

In vivo cardiac, acoustic-radiation-force-driven, shear wave velocimetry.

Journal Article Ultrasonic imaging · July 2009 Shear wave elasticity imaging (SWEI) was employed to track acoustic radiation force impulse (ARFI)-induced shear waves in the mid-myocardium of the left ventricular free wall (LVFW) of a beating canine heart. Shear waves were generated and tracked with a l ... Full text Cite

Novel acoustic radiation force impulse imaging methods for visualization of rapidly moving tissue.

Journal Article Ultrasonic imaging · July 2009 Acoustic radiation force impulse (ARFI) imaging has been demonstrated to be capable of visualizing changes in local myocardial stiffness through a normal cardiac cycle. As a beating heart involves rapidly-moving tissue with cyclically-varying myocardial st ... Full text Cite

Acoustic radiation force-induced shear wave propagation in cardiac tissue

Journal Article Progress in Biomedical Optics and Imaging - Proceedings of SPIE · June 19, 2009 Shear wave elasticity imaging (SWEI) was employed to track acoustic radiation force (ARF)-induced shear waves in the myocardium of a beating heart. Shear waves were generated in and tracked through the myocardium of the left ventricular free wall (LVFW) in ... Full text Cite

Dual-mode intracranial catheter integrating 3D ultrasound imaging and hyperthermia for neuro-oncology: feasibility study.

Journal Article Ultrason Imaging · April 2009 In this study, we investigated the feasibility of an intracranial catheter transducer with dual-mode capability of real-time 3D (RT3D) imaging and ultrasound hyperthermia, for application in the visualization and treatment of tumors in the brain. Feasibili ... Full text Link to item Cite

A fully implantable 96-channel neural data acquisition system.

Journal Article J Neural Eng · April 2009 A fully implantable neural data acquisition system is a key component of a clinically viable brain-machine interface. This type of system must communicate with the outside world and obtain power without the use of wires that cross through the skin. We pres ... Full text Link to item Cite

Integrated circuit amplifiers for multi-electrode intracortical recording.

Journal Article Journal of neural engineering · February 2009 Significant progress has been made in systems that interpret the electrical signals of the brain in order to control an actuator. One version of these systems senses neuronal extracellular action potentials with an array of up to 100 miniature probes inser ... Full text Cite

Dual-mode intracranial catheters for minimally-invasive neuro-oncology feasibility study

Journal Article Proceedings - IEEE Ultrasonics Symposium · January 1, 2009 In this study, we investigated the feasibility of dual-mode intracranial catheter transducers for visualization and treatment of tumors in the brain. Feasibility is demonstrated in two ways: 1) by developing a 12 Fr, integrated matrix and linear array cath ... Full text Cite

Acoustic radiation force impulse imaging of cardiac tissue

Journal Article Proceedings - IEEE Ultrasonics Symposium · January 1, 2009 Cardiovascular disease remains the most likely cause of death in developed countries, accounting for approximately 870,000 deaths in the United States alone in 2004. Virtually every form of cardiovascular disease involves modifications in tissue stiffness. ... Full text Cite

On the characterization of left ventricular function with acoustic radiation force impulse imaging

Journal Article Proceedings - IEEE Ultrasonics Symposium · January 1, 2009 Extensive research has been dedicated to investigating the assessment of left ventricular (LV) function via myocardial elasticity. Previous research has demonstrated acoustic radiation force impulse (ARFI) imaging to be capable of visualizing variations in ... Full text Cite

Vibrating interventional device detection using real-time 3-D color Doppler.

Journal Article IEEE Trans Ultrason Ferroelectr Freq Control · 2008 Ultrasound image guidance of interventional devices during minimally invasive surgery provides the clinician with improved soft tissue contrast while reducing ionizing radiation exposure. One problem with ultrasound image guidance is poor visualization of ... Full text Link to item Cite

Vibrating interventional device detection using real-time 3D color doppler

Journal Article Proceedings - IEEE Ultrasonics Symposium · December 1, 2007 We have previously described guidance of several interventional devices using a real time 3D (RT3D) ultrasound system with 3D color Doppler combined with the ColorMark technology. We then developed an analytical model for a vibrating needle to maximize the ... Full text Cite

Intracranial catheter for integrated 3D ultrasound imaging & hyperthermia: Feasibility study

Journal Article Proceedings - IEEE Ultrasonics Symposium · December 1, 2007 In this study, we investigate the feasibility of developing an intracranial catheter transducer capable of real time 3D (RT3D) imaging and ultrasound hyperthermia, for application in the visualization and treatment of tumors in the brain. Feasibility is de ... Full text Cite

Acoustic radiation force impulse imaging of mechanical stiffness propagation within myocardial tissue

Journal Article Proceedings - IEEE Ultrasonics Symposium · December 1, 2007 Acoustic radiation force impulse (ARFI) imaging has been shown to be capable of imaging the local myocardial stiffness changes of heart throughout the cardiac cycle. Expanding on these results, we have experimentally assessed cardiac ARFI imaging to be a s ... Full text Cite

Phase-noise driven system design of fractional-N frequency synthesizers and validation with measured results

Journal Article Proceedings - IEEE Computer Society Annual Symposium on VLSI: Emerging VLSI Technologies and Architectures · November 28, 2007 Phase noise has been a primary issue in the design of frequency synthesizers. The system level noise analysis of a fractional-N (frac-N) PLL is presented to enable the circuit design of a 5-Mbps GMSK modulated data transmitter in the 900 MHz ISM band. A ma ... Full text Cite

In vivo assessment of myocardial stiffness with acoustic radiation force impulse imaging.

Journal Article Ultrasound in medicine & biology · November 2007 Acoustic radiation force impulse (ARFI) imaging has been demonstrated to be capable of visualizing variations in local stiffness within soft tissue. Recent advances in ARFI beam sequencing and parallel imaging have shortened acquisition times and lessened ... Full text Cite

A 900 MHz ISM band mash-12 fractional-n frequency synthesizer for 5-Mbps data transmission

Journal Article Proceedings of the ACM Great Lakes Symposium on VLSI, GLSVLSI · October 1, 2007 The design of a fractional-N PLL in the 900 MHz ISM band is presented to enable 5-Mbps data transmission for neuro application using GMSK modulation. The frac-N PLL consists of a phase frequency detector (PFD), charge pump (CP), loop filter, LC-VCO, and a ... Full text Cite

Design methodology and CAD tools for prototyping delta-sigma fractional-N frequency synthesizers

Journal Article Proceedings of the International Workshop on Rapid System Prototyping · September 25, 2007 In this paper we present the design flow for a fractional-N (frac-N) frequency synthesizer prototype from the system level conceptualization of the PLL to its hardware implementation. The prototyping hardware consists of a of frac-N PLL IC designed in TSMC ... Full text Cite

A single-chip signal processing and telemetry engine for an implantable 96-channel neural data acquisition system.

Journal Article Journal of neural engineering · September 2007 A fully implantable neural data acquisition system is a key component of a clinically viable cortical brain-machine interface. We present the design and implementation of a single-chip device that serves the processing needs of such a system. Our device pr ... Full text Cite

An analytical comparison of the information in sorted and non-sorted cosine-tuned spike activity.

Journal Article Journal of neural engineering · September 2007 Spike sorting is a technologically expensive component of the signal processing chain required to interpret population spike activity acquired in a neuromotor prosthesis. No systematic analysis of the value of spike sorting has been carried out, and little ... Full text Cite

Real-time 3-D intracranial ultrasound with an endoscopic matrix array transducer

Journal Article Ultrasound In Medicine And Biology · August 2007 A transducer originally designed for transesophageal echocardiography (TEE) was adapted for real-time volumetric endoscopic imaging of the brain. The transducer consists of a 36 x 36 array with an interelement spacing of 0.18 mm. There are 504 transmitting ... Cite

Real-time three-dimensional transesophageal echocardiography for guiding interventional electrophysiology: feasibility study.

Journal Article Ultrason Imaging · July 2007 At present, there are limited methods of acquiring three-dimensional visualization of cardiac structure and function in real-time during interventional electrophysiology procedures. Images acquired for integration of computerized tomography and magnetic re ... Full text Link to item Cite

Challenges and implementation of radiation-force imaging with an intracardiac ultrasound transducer.

Journal Article IEEE transactions on ultrasonics, ferroelectrics, and frequency control · May 2007 Intracardiac echocardiography (ICE) has been demonstrated to be an effective imaging modality for the guidance of several cardiac procedures, including radiofrequency ablation (RFA). However, assessing lesion size during the ablation with conventional ultr ... Full text Cite

Thermal considerations for the design of an implanted cortical brain-machine interface (BMI)

Chapter · January 1, 2007 Devices for the brain-machine interface (BMI) are no longer science fiction but are being tested in patients with severe paralysis and advanced neuromuscular diseases.While the feasibility of controlling a device using brain-derived neural signals has been ... Cite

3-D ultrasound guidance of surgical robotics: A feasibility study

Journal Article Proceedings - IEEE Ultrasonics Symposium · December 1, 2006 The integration of real-time three-dimensional (RT3D) laparoscopic ultrasound with recent advances in robotic surgery can increase automation and ease of use for surgery in general, gynecological, and urological procedures. In this study, the 3D measuremen ... Full text Cite

Two dimensional arrays for real time 3D intracranial imaging of the brain

Journal Article Proceedings - IEEE Ultrasonics Symposium · December 1, 2006 We have described and fabricated 2D array transducers for many real time volumetric imaging applications. These applications include transducers operating up to 5 MHz for transthoracic imaging, up to 15 MHz for intracardiac echocardiography (ICE), 5 MHz fo ... Full text Cite

In Vivo acoustic radiation force impulse imaging of the cardiac cycle

Journal Article Proceedings - IEEE Ultrasonics Symposium · December 1, 2006 In vivo ARFI images of an exposed canine heart were acquired through multiple cardiac cycles. The matched eletrocardiogram (ECG) was also recorded. Sequences with the radiation force pulse amplitude set to zero were also acquired to measure potential artif ... Full text Cite

3-D ultrasound guidance of surgical robotics: a feasibility study.

Journal Article IEEE transactions on ultrasonics, ferroelectrics, and frequency control · November 2006 Laparoscopic ultrasound has seen increased use as a surgical aide in general, gynecological, and urological procedures. The application of real-time, three-dimensional (RT3D) ultrasound to these laparoscopic procedures may increase information available to ... Full text Cite

Liver ablation guidance with acoustic radiation force impulse imaging: challenges and opportunities.

Journal Article Phys Med Biol · August 7, 2006 Previous studies have established the feasibility of monitoring radiofrequency (RF) ablation procedures with acoustic radiation force impulse (ARFI) imaging. However, questions remained regarding the utility of the technique in clinically realistic scenari ... Full text Link to item Cite

Real-time, 3-D ultrasound with multiple transducer arrays.

Journal Article IEEE Trans Ultrason Ferroelectr Freq Control · January 2006 Modifications were made to a commercial real-time, three-dimensional (3-D) ultrasound system for near simultaneous 3-D scanning with two matrix array transducers. As a first illustration, a transducer cable assembly was modified to incorporate two independ ... Full text Link to item Cite

Real-time 3D ultrasound laparoscopy

Journal Article Proceedings - IEEE Ultrasonics Symposium · December 1, 2005 We have previously described 2D array ultrasound transducers operating up to 13.5 MHz for applications including real time 3D transthoracic imaging, real time volumetric intracardiac echocardiography (ICE), real time transesophageal echocardiography (TEE) ... Full text Cite

In vivo acoustic radiation force impulse imaging of cardiac ablations

Journal Article Proceedings - IEEE Ultrasonics Symposium · December 1, 2005 Radiofrequency ablation (RFA) has been demonstrated to be an effective procedure for the treatment of rapid or irregular heartbeats such as atrial fibrillation. Assessing lesion size and growth with ultrasound has been limited, as the changes within conven ... Full text Cite

A membrane model of electrically remodelled atrial myocardium derived from in vivo measurements.

Journal Article Europace : European pacing, arrhythmias, and cardiac electrophysiology : journal of the working groups on cardiac pacing, arrhythmias, and cardiac cellular electrophysiology of the European Society of Cardiology · September 2005 AimsContemporary ionic-based membrane models are computationally expensive and are not intended to match the properties of a given experimental preparation. The aim of this work was to use measured restitution properties of electrically remodelled ... Full text Cite

Real-time 3D laparoscopic ultrasonography.

Journal Article Ultrason Imaging · July 2005 We have previously described 2D array ultrasound transducers operating up to 10 MHz for applications including real time 3D transthoracic imaging, real time volumetric intracardiac echocardiography (ICE), real time 3D intravascular ultrasound (IVUS) imagin ... Full text Link to item Cite

Acoustic radiation force impulse imaging of myocardial radiofrequency ablation: initial in vivo results.

Journal Article IEEE transactions on ultrasonics, ferroelectrics, and frequency control · April 2005 Acoustic radiation force impulse (ARFI) imaging techniques were used to monitor radiofrequency (RF) ablation of ovine cardiac tissue in vivo. Additionally, ARFI M-mode imaging methods were used to interrogate both healthy and ablated regions of myocardial ... Full text Cite

Engineering skeletal myoblasts: roles of three-dimensional culture and electrical stimulation.

Journal Article American journal of physiology. Heart and circulatory physiology · April 2005 Immature skeletal muscle cells, or myoblasts, have been used in cellular cardiomyoplasty in attempts to regenerate cardiac muscle tissue by injection of cells into damaged myocardium. In some studies, muscle tissue within myoblast implant sites may be morp ... Full text Cite

Enhanced phase noise modeling of fractional-N frequency synthesizers

Journal Article IEEE Transactions on Circuits and Systems I: Regular Papers · January 1, 2005 Mathematical models for the behavior of fractional-N phase-locked-loop frequency synthesizers (Frac-N) are presented. The models are intended for calculating rms phase error and determining spurs in the output of Frac-N. The models describe noise contribut ... Full text Cite

Real time 3D ultrasound imaging of the brain

Journal Article Proceedings - IEEE Ultrasonics Symposium · December 1, 2004 We tested the feasibility of real time three dimensional ultrasound imaging in the brain with a 2.5MHz 2D array using a Volumetrics Model 1 scanner. In a human subject, the real time 3D scans produced simultaneous transcranial axial, coronal and saggital i ... Cite

Real-time 3D transesophageal echocardiography

Journal Article Proceedings - IEEE Ultrasonics Symposium · December 1, 2004 Transesophageal echocardiography (TEE) is established as an essential diagnostic tool for patients that are obese or that exhibit signs of pulmonary disease. However, current techniques in transesophageal scanning of the heart are limited by the maneuverab ... Cite

Real-time 3D color doppler for guidance of vibrating interventional devices

Journal Article Proceedings - IEEE Ultrasonics Symposium · December 1, 2004 The goal of this investigation is to examine the feasibility of guiding interventional devices using piezoelectric buzzers to create a velocity source, which is imaged and tracked with real time 3D (RT3D) ultrasound and Color Doppler. Interventional device ... Cite

A miniaturized catheter 2-D array for real-time, 3-D intracardiac echocardiography.

Journal Article IEEE Trans Ultrason Ferroelectr Freq Control · October 2004 The design, fabrication, and characterization of a 112 channel, 5 MHz, two-dimensional (2-D) array transducer constructed on a six layer flexible polyimide interconnect circuit is described. The transducer was mounted in a 7 Fr (2.33 mm outside diameter) c ... Full text Link to item Cite

Feasibility study: real-time 3-D ultrasound imaging of the brain.

Journal Article Ultrasound Med Biol · October 2004 We tested the feasibility of real-time, 3-D ultrasound (US) imaging in the brain. The 3-D scanner uses a matrix phased-array transducer of 512 transmit channels and 256 receive channels operating at 2.5 MHz with a 15-mm diameter footprint. The real-time sy ... Full text Link to item Cite

Real-time 3D transesophageal echocardiography.

Journal Article Ultrason Imaging · October 2004 Transesophageal echocardiography (TEE) is an essential diagnostic tool in patients with poor transthoracic echocardiographic windows or when detailed imaging of structures distant from the chest wall is necessary. A real-time 3D TEE probe has been fabricat ... Full text Link to item Cite

Transmural action potential repolarization heterogeneity develops postnatally in the rabbit.

Journal Article J Cardiovasc Electrophysiol · July 2004 INTRODUCTION: In the hereditary long QT syndrome, arrhythmia risk changes with age despite the presence of an ion channel mutation throughout development. Age-dependent changes in the transmural dispersion of repolarization may modulate this vulnerability. ... Full text Link to item Cite

Real-time 3D color flow Doppler for guidance of vibrating interventional devices.

Journal Article Ultrason Imaging · July 2004 The goal of this investigation was to examine the feasibility of guiding interventional devices using piezoelectric buzzers to create velocity sources, which were imaged and tracked with real-time 3D color flow Doppler. The interventional devices examined ... Full text Link to item Cite

Evaluation of spike-detection algorithms for a brain-machine interface application.

Journal Article IEEE transactions on bio-medical engineering · June 2004 Real time spike detection is an important requirement for developing brain machine interfaces (BMIs). We examined three classes of spike-detection algorithms to determine which is best suited for a wireless BMI with a limited transmission bandwidth and com ... Full text Cite

Transmission latencies in a telemetry-linked brain-machine interface.

Journal Article IEEE Trans Biomed Eng · June 2004 To be clinically viable, a brain-machine interface (BMI) requires transcutaneous telemetry. Spike-based compression algorithms can be used to reduce the amount of telemetered data, but this type of system is subject to queuing-based transmission delays. Th ... Full text Link to item Cite

Minimum energy single-shock internal atrial defibrillation in sheep.

Journal Article J Interv Card Electrophysiol · April 2004 Well-tolerated internal atrial defibrillation shocks must be below the pain threshold, which has been estimated to be less than 1 Joule. Defibrillation of the atria with low energy is made possible by delivering shocks at the low end of the defibrillation ... Full text Link to item Cite

A multichannel telemetry system for single unit neural recordings.

Journal Article J Neurosci Methods · February 15, 2004 We present the design, testing, and evaluation of a 16 channel wearable telemetry system to facilitate multichannel single unit recordings from freely moving test subjects. Our design is comprised of (1) a 16-channel analog front end board to condition and ... Full text Link to item Cite

A low power multichannel analog front end for portable neural signal recordings.

Journal Article J Neurosci Methods · February 15, 2004 We present the design and testing of a 16-channel analog amplifier for processing neural signals. Each channel has the following features: (1) variable gain (70-94 dB), (2) four high pass Bessel filter poles (f(-3 dB)=445 Hz), (3) five low pass Bessel filt ... Full text Link to item Cite

A simulation study of information transmission by multi-unit microelectrode recordings.

Journal Article Network (Bristol, England) · February 2004 To analyse the information content of multi-unit signals, cases of two and three superimposed neural responses to a stimulus were simulated. The multi-unit Shannon information rates were compared with those of the constituent single-unit spike trains and a ... Full text Cite

A novel implantable cardiac telemetry system for studying atrial fibrillation

Journal Article Physiol. Meas. (UK) · 2004 Atrial fibrillation (AF) is the most common arrhythmia in clinical practice. Most in vivo experimental research on AF is performed in a surgical setting, on animals instrumented by external devices, or using commercial implantable pacemakers. This paper de ... Full text Link to item Cite

Advances in 2-D array catheter transducers for real-time three-dimensional intracardiac echocardiography

Journal Article Proceedings of the IEEE Ultrasonics Symposium · December 1, 2003 In this paper, we describe advances in the design, fabrication and testing of two-dimensional catheter-mounted arrays for real-time three-dimensional (RT3-D) intracardiac echocardiography (ICE). These include a 7 Fr (2.3 mm O.D.), 112 element 2-D array uti ... Cite

ARFI imaging of thermal lesions in ex vivo and in vivo soft tissues

Conference Proceedings of the IEEE Ultrasonics Symposium · December 1, 2003 The ability of ARFI imaging to monitor the ablation of soft tissues both ex vivo and in vivo was investigated. Thermal lesions were induced both in freshly excised bovine liver samples and in myocardial tissue of live sheep. While conventional sonography w ... Cite

Dual lumen transducer probes for real-time 3-D interventional cardiac ultrasound.

Journal Article Ultrasound Med Biol · September 2003 We have developed dual lumen probes incorporating a forward-viewing matrix array transducer with an integrated working lumen for delivery of tools in real-time 3-D (RT3-D) interventional echocardiography. The probes are of 14 Fr and 22 Fr sizes, with 112 c ... Full text Link to item Cite

Two multichannel integrated circuits for neural recording and signal processing.

Journal Article IEEE Trans Biomed Eng · February 2003 We have developed, manufactured, and tested two analog CMOS integrated circuit "neurochips" for recording from arrays of densely packed neural electrodes. Device A is a 16-channel buffer consisting of parallel noninverting amplifiers with a gain of 2 V/V. ... Full text Link to item Cite

16-channel neural pre-conditioning device

Conference International IEEE/EMBS Conference on Neural Engineering, NER · January 1, 2003 We present the mixed-signal circuit design, layout, implementation techniques, and test data for a 16-channel neural pre-conditioning device that is used to amplify and filter signals acquired from chronically implanted electrodes in an animal's brain. Sch ... Full text Cite

Effects of spike sorting error on information content in multi-neuron recordings

Conference International IEEE/EMBS Conference on Neural Engineering, NER · January 1, 2003 In brain-machine interface (BMI) applications, multi-channel recordings are spike sorted before the single-unit spike trains are used in computational analysis to decode the neural response. Nevertheless, questions about the necessity and effectiveness of ... Full text Cite

Two dimensional arrays for 3-D ultrasound imaging

Journal Article Proceedings of the IEEE Ultrasonics Symposium · December 1, 2002 Phased array ultrasound transducers have been fabricated in our laboratories at Duke University since 1970. In 1986, we began the development of 2-D arrays with a 20 × 20 element Mills cross array including 64 active channels operating at 1 MHz which produ ... Cite

A multichannel CMOS analog front end IC for neural recordings

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 2002 A multichannel integrated circuit for processing extracellular neural signals has been designed and manufactured. The analog CMOS IC consists of 17 parallel channels, each comprised of three cascaded stages: bandpass filter with gain, switched capacitor fi ... Cite

Response of fibrillating atria to successful low probability of success shocks

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 2002 The mechanism of very low probability of success (PS) atrial defibrillation is not understood. We studied the activation patterns of the atria following low energy/low probability of success shocks to determine if the pattern of activation following these ... Cite

Progress toward controlling in vivo fibrillating sheep atria using a nonlinear-dynamics-based closed-loop feedback method.

Journal Article Chaos (Woodbury, N.Y.) · September 2002 We describe preliminary experiments on controlling in vivo atrial fibrillation using a closed-loop feedback protocol that measures the dynamics of the right atrium at a single spatial location and applies control perturbations at a single spatial location. ... Full text Cite

Region specific modeling of cardiac muscle: comparison of simulated and experimental potentials.

Journal Article Annals of biomedical engineering · July 2002 This article investigates the quantitative predictive capabilities of region-specific models by comparing experimental electrograms obtained from in vivo mapping of the ventricular free wall with those obtained through simulation of a region specific three ... Full text Cite

Guidance of cardiac pacemaker leads using real time 3D ultrasound: feasibility studies.

Journal Article Ultrasonic imaging · April 2002 We investigated the feasibility of the guidance of pacemaker lead implantation using the pacemaker lead stylet as an acoustic wave-guide combined with real time 3D ultrasound imaging. In one approach, with a 2.5 MHz transducer coupled to a stylet of a pace ... Full text Cite

Feasibility study of real-time three-dimensional intracardiac echocardiography for guidance of interventional electrophysiology.

Journal Article Pacing Clin Electrophysiol · March 2002 The authors tested the feasibility of real-time three-dimensional intracardiac echocardiography for guidance of interventional electrophysiological studies. The three-dimensional scanner uses a matrix array ultrasound transducer of 64 channels operating at ... Full text Link to item Cite

Feasibility study for real time three dimensional Doppler intracardiac echocardiography.

Journal Article Ultrason Imaging · January 2002 Using catheter-mounted two-dimensional array transducers, we have obtained real-time three-dimensional color flow and spectral Doppler ultrasound images in phantoms. We have constructed several transducers operating at 5 MHz with up to 137 channels inside ... Full text Link to item Cite

Locating a catheter transducer in a three-dimensional ultrasound imaging field.

Journal Article IEEE transactions on bio-medical engineering · December 2001 Cardiac procedures rely on fluoroscopy for catheter guidance and visualization. However, fluoroscopy provides poor contrast of myocardial structures and exposes both the patient and health care providers to ionizing radiation. As an alternative to fluorosc ... Full text Cite

Real-time three dimensional intracardiac echocardiography for guidance of cardiac interventional procedures

Journal Article Proceedings of the IEEE Ultrasonics Symposium · December 1, 2001 We have tested the feasibility of real-time three dimensional intracardiac echocardiography for guidance of interventional electrophysiology studies. We have constructed 2D array ultrasound transducers operating at 5MHz with 64 channels in a 12 F catheter, ... Cite

Real-time three-dimensional intracardiac echocardiography.

Journal Article Ultrasound Med Biol · September 2001 Using catheter-mounted 2-D array transducers, we have obtained real-time 3-D intracardiac ultrasound (US) images. We have constructed several transducers with 64 channels inside a 12 French catheter lumen operating at 5 MHz. The transducer configuration ma ... Full text Link to item Cite

Two dimensional arrays for real time volumetric and intracardiac imaging with simultaneous electrocardiogram

Journal Article Proceedings of the IEEE Ultrasonics Symposium · December 1, 2000 Design, fabrication and performance of a two-dimensional array operating at 10 MHz for real time volumetric and intracardiac imaging with simultaneous electrocardiagram was presented. Use of the device to monitor and quantify RF ablation study was demonstr ... Cite

Finite element model of radiofrequency ablation with true blood flow

Journal Article Annals of Biomedical Engineering · December 1, 2000 A finite element model (FEM) of radiofrequency ablation (RFA) with true fluid motion (TEM) is presented. The FEM tissue (TT) and blood temperature (BT) data are validated with in vitro (IV) experimental TT and BT data. ... Cite

A three-dimensional finite element model of radiofrequency ablation with blood flow and its experimental validation.

Journal Article Annals of biomedical engineering · September 2000 A novel three-dimensional finite element model for the study of radiofrequency ablation is presented. The model was used to perform an analysis of the temperature distribution in a tissue block heated by RF energy and cooled by blood (fluid) flow. This wor ... Full text Cite

In vitro temperature map of cardiac ablation demonstrates the effect of flow on lesion development.

Journal Article Annals of biomedical engineering · September 2000 This paper presents an in vitro temperature mapping study of bovine cardiac tissue during radiofrequency ablation. The objectives were to: (i) develop a technique for measuring the spatial and temporal temperature distribution in the tissue and in the bloo ... Full text Cite

Existence of bistability and correlation with arrhythmogenesis in paced sheep atria.

Journal Article Journal of cardiovascular electrophysiology · July 2000 IntroductionStudies of the electrical dynamics of cardiac tissue are important for understanding the mechanisms of arrhythmias. This study uses high-frequency pacing to investigate the dynamics of sheep atria.Methods and resultsA 504-elec ... Full text Cite

Designing a brain- machine interface for neuroprosthetic control

Chapter · January 1, 2000 There are roughly four major subassemblies of a brain derived neuroprosthetic control device: (1) the electrodes subassembly, (2) signal conditioning subassembly, (3) signal acquisition subassembly, and (4) transmitter subassemblies (Table 6.1). Notably ab ... Cite

Two dimensional arrays for real time intracardiac volumetric imaging

Journal Article Ultrasound in Medicine and Biology · January 1, 2000 We describe the design, fabrication, and evaluation of catheter mounted two dimensional array transducers for real time intracardiac volumetric scanning as a guide for cardiac interventional procedures including electrophysiological mapping and radiofreque ... Cite

Two dimensional arrays for real time intracardiac volumetric imaging

Journal Article Ultrasound in Medicine and Biology · 2000 We describe the design, fabrication, and evaluation of catheter mounted two dimensional array transducers for real time intracardiac volumetric scanning as a guide for cardiac interventional procedures including electrophysiological mapping and radiofreque ... Cite

Two dimensional arrays for real time intracardiac volumetric imaging

Journal Article Ultrasound in Medicine and Biology · 2000 We describe the design, fabrication, and evaluation of catheter mounted two dimensional array transducers for real time intracardiac volumetric scanning as a guide for cardiac interventional procedures including electrophysiological mapping and radiofreque ... Cite

Temperature-controlled and constant-power radio-frequency ablation: what affects lesion growth?

Journal Article IEEE transactions on bio-medical engineering · December 1999 Radio-frequency (RF) catheter ablation is the primary interventional therapy for the treatment of many cardiac tachyarrhythmias. Three-dimensional finite element analysis of constant-power (CPRFA) and temperature-controlled RF ablation (TCRFA) of the endoc ... Full text Cite

Registration of three-dimensional cardiac catheter models to single-plane fluoroscopic images.

Journal Article IEEE transactions on bio-medical engineering · December 1999 Transvenous cardiac procedures require accurate positioning of catheters within the geometrically complex cavities of the heart. Recently, nonfluoroscopic catheter tracking technologies have been developed to quantitate the (degrees-of-freedom) three-dimen ... Full text Cite

Existence of bistability and correlation with arrhythmogenesis in sheep atria

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1999 This experimental study investigates the response of sheep atria to periodic pacing. In 23 trials over 6 animals, a window of bistability was observed wherein for a range of pacing periods the atria responded 1:1 or 2:1 depending on whether pacing period w ... Cite

Method for locating a catheter transducer in a 3-D ultrasound field

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1999 This paper presents a method for using ultrasound to locate a catheter mounted transducer in three dimensions. The method processes signals received on the catheter transducer to locate its position within the emitted ultrasonic field. The simulation resul ... Cite

Effect of pacing site on ventricular fibrillation initiation by shocks during the vulnerable period.

Journal Article Am J Physiol · November 1999 The critical point hypothesis for the upper limit of vulnerability (ULV) states that the site of S1 pacing should not affect the ULV S2 shock strength for a single S2 shock electrode configuration but may affect the S1-S2 interval at which sub-ULV shocks i ... Full text Link to item Cite

Two-dimensional catheter arrays for real time intracardiac volumetric imaging

Journal Article Proceedings of SPIE - The International Society for Optical Engineering · January 1, 1999 The arrays for intracardiac volumetric imaging based upon two different designs: a 10×10 = 100 element 5 MHz forward looking 2-D array; and a 13×11 = 143 element 5 MHz 2-D array for side scanning are constructed. For the forward looking 2-D arrays, the tra ... Cite

Random nature of fibrillation leads to the probabilistic nature of defibrillation.

Journal Article Journal of electrocardiology · January 1999 Full text Cite

Effect of skin electrode location on radiofrequency ablation lesions: an in vivo and a three-dimensional finite element study.

Journal Article Journal of cardiovascular electrophysiology · December 1998 IntroductionObjectivesTo assess the effect of skin electrode location on radiofrequency (RF) ablation lesion dimensions and energy requirements.BackgroundLittle is known about the effects of skin electrode location on RF ablation ... Full text Cite

Finite element analysis predicts dose-response relationship for constant power and temperature controlled radiofrequency ablation

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1997 Radiofrequency (RF) energy is commonly used to ablate cardiac tissue responsible for tachyarrhythmias. Lesion growth with time is investigated for temperature controlled and constant power RF ablation. Computer simulations are performed to obtain the lesio ... Cite

Application of sonomicrometry and multidimensional scaling to cardiac catheter tracking.

Journal Article IEEE transactions on bio-medical engineering · November 1997 This paper describes a technique for tracking the three-dimensional (3-D) position of a cardiac catheter using sonomicrometry and the mathematical method of multidimensional scaling (MDS). Sonomicrometry is used to measure the distances between ultrasonic ... Full text Cite

Importance of electrode conductive surface area and edge effects on ventricular defibrillation efficacy.

Journal Article Journal of cardiovascular electrophysiology · November 1997 IntroductionThe role of edge effects and electrode surface area of the right ventricular (RV) transvenous lead (TVL) on defibrillation efficacy is unknown.Methods and resultsDefibrillation threshold (DFT) testing was conducted randomly in ... Full text Cite

Surface coverage effects on defibrillation impedance for transvenous electrodes.

Journal Article Annals of biomedical engineering · July 1997 Transvenous defibrillation electrodes are constructed by wrapping conductive elements around an insulating base. However, these conductive elements do not cover the entire area of the base. The effects of varying the surface area coverage on the defibrilla ... Full text Cite

Does reducing capacitance have potential for further miniaturisation of implantable defibrillators?

Journal Article Heart (British Cardiac Society) · March 1997 ObjectiveTo determine whether considerably smaller capacitors could replace 125 microF capacitors as the standard for use in implantable defibrillators.MethodsMeasured energy, impedance, voltage, and current delivered were compared at def ... Full text Cite

Finite element study of the effects of ground electrode position on radio frequency ablation lesions

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1996 The effect of the ground patch location on lesions caused by radio frequency (RF) ablation is investigated. Computer simulations are performed to compare the lesion dimensions and shape generated by RF ablation for different locations of the ground patch. ... Cite

Epicardial sock mapping following monophasic and biphasic shocks of equal voltage with an endocardial lead system.

Journal Article Journal of cardiovascular electrophysiology · April 1996 IntroductionThe reason for the increased defibrillation efficacy of biphasic shocks over monophasic shock is not definitely known.Methods and resultsIn six anesthetized pigs, we mapped the epicardium after transvenous defibrillation shock ... Full text Cite

Combined experimental and modeling approach for designing transvenous defibrillation leads

Journal Article IEEE/ Engineering in Medicine and Biology Society Annual Conference · December 1, 1995 The performance and behavior of Transvenous Defibrillation (TVD) electrodes is influenced by their complex characteristics. These include the electrodes' geometry, surface structure, and material. This study describes the experimental and modeling approach ... Cite

Chilled-tip electrode radio frequency ablation of the endocardium: a finite element study

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1995 Computer simulations are performed to compare the depth and volume of the lesions caused by chilled radio-frequency ablation and conventional RF ablation. Results indicate that when the tissue temperature reaches 100°C, the volume and the depth of the tiss ... Cite

Effect of point of connection on the surface current profile over transvenous defibrillation electrodes

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1995 This study uses a semi-analytic solution to model the role played by the point of connection in Transvenous Defibrillation (TVD) electrodes. Results indicate that the current distribution on the electrode surface is significantly perturbed by this electrod ... Cite

Regional capture of fibrillating ventricular myocardium. Evidence of an excitable gap.

Journal Article Circulation research · October 1995 Previous investigations have suggested that during ventricular fibrillation (VF) pacing stimuli are incapable of evoking propagated ventricular activations. To determine whether regional myocardial capture could be achieved during rapid pacing in VF, extra ... Full text Cite

Predicting the potential gradient field in ventricular fibrillation from shocks delivered in paced rhythm.

Journal Article Am J Physiol · June 1995 A method of defibrillation threshold determination that utilizes low-strength shocks delivered in a benign rhythm would be desirable. Because the two-dimensional epicardial potential gradient (PG) is a shock parameter that is linked to defibrillation, we e ... Full text Link to item Cite

Alteration of ventricular fibrillation by propranolol and isoproterenol detected by epicardial mapping with 506 electrodes.

Journal Article Journal of cardiovascular electrophysiology · June 1995 IntroductionWe hypothesized that drugs which alter ventricular refractoriness or excitability produce quantifiable changes in ventricular fibrillation.Methods and resultsWe used a 528-channel mapping system to quantify the effects of the ... Full text Cite

Comparison of defibrillation probability of success curves for an endocardial lead configuration with and without an inactive epicardial patch.

Journal Article J Am Coll Cardiol · May 1995 OBJECTIVES: This study sought to assess the effect of passive "bystander" epicardial electrodes on defibrillation efficacy. BACKGROUND: We hypothesized that an inactive epicardial patch placed in an area of low potential gradient from an endocardial electr ... Full text Link to item Cite

Importance of representing surface geometry and electrode resistance of transvenous electrodes in defibrillation models

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1994 The potential gradient fields created by Transvenous Defibrillation (TVD) Electrodes during internal defibrillation are often calculated using volume conductor models. Most defibrillation models represent the TVD electrode as an equipotential cylindrical r ... Cite

Importance of anisotropy in potential gradient calculations

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1994 The effects of anisotropy on potential gradient calculations in muscle tissue are investigated in an idealized two dimensional geometry. The percent of area above a gradient threshold (PAAT) is calculated in an uniform applied field and in a non-uniform fi ... Cite

Effects of peroneal nerve stimulation on hypothalamic stimulation-induced ventricular arrhythmias in rabbits.

Journal Article The American journal of physiology · November 1994 We tested the hypothesis that peripheral afferent nerve stimulation decreases the incidence of ventricular arrhythmias induced by central nervous system stimulation. The hypothalamus in each of 24 anesthetized rabbits (12 with anterior myocardial ischemia) ... Full text Cite

The probability of defibrillation success and the incidence of postshock arrhythmia as a function of shock strength.

Journal Article Pacing and clinical electrophysiology : PACE · July 1994 The effects of high voltage defibrillation shocks given to six swine were studied to determine if there is a limit to the advantage gained from increasing the shock strength. An endocardial electrode was placed in the right ventricle, and a 114-cm2 cutaneo ... Full text Cite

Why do some patients have high defibrillation thresholds at defibrillator implantation? Answers from basic research.

Journal Article Pacing and clinical electrophysiology : PACE · February 1994 Implantable cardioverter defibrillators reduce the risk of sudden cardiac death in patients with ventricular tachyarrhythmias. However, for the few patients with unacceptably high defibrillation thresholds at implantation the risk of sudden death may remai ... Full text Cite

Estimation of tissue resistivities from multiple-electrode impedance measurements.

Journal Article Physics in medicine and biology · January 1994 In order to measure in vivo resistivity of tissues in the thorax, the possibility of combining anatomical data extracted from high-resolution images with multiple-electrode impedance measurements, a priori knowledge of the range of tissue resistivities, an ... Full text Cite

Measuring changing spatial complexity in ventricular fibrillation using the Karhunen-Loeve decomposition of 506-channel epicardial data

Journal Article Computers in Cardiology · December 1, 1993 The Karhunen-Loeve (K-L) decomposition was used to describe quantitatively changes in spatial organization during extended episodes of ventricular fibrillation (VF). VF was induced by premature stimulation in 5 pigs. Unipolar epicardial electrograms were s ... Cite

528 channel system for the acquisition and display of defibrillation and electrocardiographic potentials

Journal Article Computers in Cardiology · December 1, 1993 A 528 channel data acquisition and display system has been developed which allows us to study electrical therapies of the heart. The acquisition system records defibrillation shock potentials and electrograms from the heart. The display system presents ani ... Cite

Accurate finite element model of the heart for calculating the electric field due to defibrillation

Journal Article Computers in Cardiology · December 1, 1993 A physiologically accurate heart model is created from a set of magnetic resonance images of a pig heart. Details include the four chambers as well as the superior vena cava (SVC), and the pulmonary artery. A pair of electrodes is introduced into the model ... Cite

A quantitative measurement of spatial order in ventricular fibrillation.

Journal Article Journal of cardiovascular electrophysiology · October 1993 IntroductionThe degree of organization in ventricular fibrillation (VF) is not known. As an objective measurement of spatial order, spatial correlation functions and their characteristic lengths were estimated from epicardial electrograms of pigs ... Full text Cite

Effective defibrillation in pigs using interleaved and common phase sequential biphasic shocks.

Journal Article Pacing and clinical electrophysiology : PACE · August 1993 Previous studies have shown that low internal defibrillation thresholds (DFTs) can be attained by using two pairs of electrodes and combining biphasic shocks with sequential timing. The purpose of this two-part study was to test the defibrillation efficacy ... Full text Cite

Effects of monophasic and biphasic shocks on action potentials during ventricular fibrillation in dogs.

Journal Article Circulation research · August 1993 This study determined the response of action potentials during ventricular fibrillation (VF) to timed monophasic and biphasic shocks. A floating glass microelectrode was used to record intracellularly from the anterior right ventricle in 10 open-chest dogs ... Full text Cite

Is the second phase of a biphasic defibrillation waveform the defibrillating phase?

Journal Article Pacing and clinical electrophysiology : PACE · July 1993 Why some biphasic waveforms defibrillate with lower energies than monophasic waveforms of similar duration is unknown. One hypothesis is that the first phase of a biphasic waveform acts as a conditioning, hyperpolarizing prepulse to prepare for defibrillat ... Full text Cite

Epicardial mapping of ventricular defibrillation with monophasic and biphasic shocks in dogs.

Journal Article Circ Res · January 1993 To study the mechanism of defibrillation and the reason for the increased defibrillation efficacy of biphasic waveforms, the potential gradient in a 32 x 30-mm region of the right ventricle in 15 dogs was progressively lowered in four steps while a strong ... Full text Link to item Cite

Calculating endocardial potentials from epicardial potentials measured during external stimulation.

Journal Article IEEE transactions on bio-medical engineering · September 1992 This paper presents a boundary integral method for calculating the potential field generated by external stimulation at locations within the heart using realistic heart geometry and samples of the potential taken from the epicardial surface. This method as ... Full text Cite

Effect of pulse separation between two sequential biphasic shocks given over different lead configurations on ventricular defibrillation efficacy.

Journal Article Circulation · June 1992 BackgroundTwo sequential biphasic shocks delivered over separate lead configurations markedly improve defibrillation efficacy compared with a single shock alone. We investigated the effect of varying the intershock interval between sequential biph ... Full text Cite

Three-dimensional potential gradient fields generated by intracardiac catheter and cutaneous patch electrodes.

Journal Article Circulation · May 1992 BackgroundDefibrillation may be improved if electrode configurations can be found that create a larger and more even voltage gradient field across the heart. This study determined the magnitude of the shock gradient fields generated by four nontho ... Full text Cite

Cardiac potential and potential gradient fields generated by single, combined, and sequential shocks during ventricular defibrillation.

Journal Article Circulation · April 1992 BackgroundPotential gradient field determination may be a helpful means of describing the effects of defibrillation shocks; however, potential gradient field requirements for defibrillation with different electrode configurations have not been est ... Full text Cite

Existence of both fast and slow channel activity during the early stages of ventricular fibrillation.

Journal Article Circulation research · April 1992 Although sodium channels have been reported to be inactive after 5-10 minutes of ventricular fibrillation (VF), their state during early VF is unknown. In 12 open-chest dogs, a floating glass microelectrode was used to record intracellular action potential ... Full text Cite

A method for determining surface electrode location and boundary shape using impedance measurements

Conference Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS · January 1, 1992 We have developed an algorithm to determine the boundary shape of a homogeneous volume conductor in cases where the surface can be defined by the location of electrodes. The algorithm adjusts the positions of electrodes in space to provide the best fit to ... Full text Cite

A programmable cardiac stimulator

Conference Proceedings - Computers in Cardiology, CIC 1992 · January 1, 1992 A programmable constant current cardiac stimulator for use in a cardiac electrophysiology research lab has been implemented with a Macintosh II interfaced to voltage to current converters. The Macintosh II was equipped with three boards from National Instr ... Full text Cite

Pacing thresholds for cathodal and anodal high-frequency monophasic pulses

Journal Article Journal of Cardiovascular Electrophysiology · January 1, 1992 Introduction: The purpose of this study was to investigate ventricular pacing with bursts of high-frequency monophasic pulses using mathematical modeling and animal experiments. The study concentrated on the dependence of anodal and cathodal thresholds on ... Full text Cite

Response of relatively refractory canine myocardium to monophasic and biphasic shocks.

Journal Article Circulation · December 1991 BACKGROUND: Certain biphasic waveforms defibrillate at lower energies than monophasic waveforms, although the mechanism is unknown. METHODS AND RESULTS: The relative ability of monophasic and biphasic shocks to stimulate partially refractory myocardium was ... Full text Link to item Cite

Errors in calculating the epicardial potential gradient field from unipolar voltage measurements during cardiac defibrillation

Journal Article Proceedings of the Annual Conference on Engineering in Medicine and Biology · December 1, 1991 An examination is made of the errors generated when calculating the magnitude of the epicardial potential gradient using voltages recorded from three unipolar electrodes in a fixed triangular geometry on the epicardial surface. The error sensitivity of the ... Cite

Prolongation of repolarization time by electric field stimulation with monophasic and biphasic shocks in open-chest dogs.

Journal Article Circulation research · June 1991 Recent studies suggest that 1) electrically induced fibrillation and defibrillation involve prolongation of refractoriness by the shock in addition to stimulation and 2) biphasic waveforms are more efficient for defibrillation than are comparable monophasi ... Full text Cite

Defibrillation with low voltage using a left ventricular catheter and four cutaneous patch electrodes in dogs.

Journal Article Pacing and clinical electrophysiology : PACE · March 1991 The purpose of this study was to determine a lower limit of defibrillation thresholds (DFTs) that could be used to evaluate nonthoracotomy lead configurations for implantable defibrillators. A lead configuration that consisted of a left ventricular cathete ... Full text Cite

Current concepts for selecting the location, size and shape of defibrillation electrodes.

Journal Article Pacing and clinical electrophysiology : PACE · February 1991 Full text Cite

A graphical display system for animating mapped cardiac potentials

Journal Article · December 1, 1990 A graphical display system for animating mapped cardiac potentials is described. The system displays recorded voltages from 121 epicardial electrodes simultaneously on a computer monitor using color to indicate the magnitude of the voltage. Numerous option ... Cite

Strength-duration and probability of success curves for defibrillation with biphasic waveforms.

Journal Article Circulation · December 1990 Certain biphasic waveforms require less energy to defibrillate than do monophasic pulses of equal duration, although the mechanisms of this increased effectiveness remain unclear. This study used strength-duration and percent success curves for defibrillat ... Full text Cite

Three-dimensional visualization of electrical variables in the ventricular wall of the heart

Journal Article Proceedings of the First Conference on Visualization in Biomedical Computing · December 1, 1990 A set of programs developed to display the potentials and the magnitudes of the estimated potential gradients generated by defibrillation shocks are discussed. There are three types of displays. The first type displays three-dimensional surfaces constructe ... Cite

Effect of limited voltage resolution on an algorithm for determining electrode positions from impedance

Journal Article Proceedings of the Annual Conference on Engineering in Medicine and Biology · December 1, 1990 An algorithm that adjusts the positions of electrodes in space to provide the best fit to impedance data is presented. The performance of this algorithm was tested in a simulation, to determine the effect of limiting the resolution of the input voltage dat ... Cite

Comparison of activation during ventricular fibrillation and following unsuccessful defibrillation shocks in open-chest dogs.

Journal Article Circulation research · June 1990 The purpose of this study was to map in detail the spread of activation away from sites of early postshock excitation following unsuccessful defibrillation to determine whether these activation fronts are the unaltered continuation of activation fronts pre ... Full text Cite

Activation in unipolar cardiac electrograms: a frequency analysis.

Journal Article IEEE transactions on bio-medical engineering · May 1990 We have developed and tested several detectors of local activations in unipolar cardiac electrograms; the detectors are based on the frequency content of the waveforms. For this study, myocardial regions with no local electrical activity were created with ... Full text Cite

Conduction disturbances caused by high current density electric fields.

Journal Article Circ Res · May 1990 During internal defibrillation, potential gradients greater than 100 V/cm occur near defibrillation electrodes. Such strong fields may cause deleterious effects, including arrhythmias. This study determined 1) the effects of such strong fields on the propa ... Full text Link to item Cite

Utilization of esophageal reference electrode to enhance impedance imaging

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1989 Summary form only given. The authors report on the results of an analysis of the expected improvement in distinguishability of target inhomogeneities when an esophageal reference electrode is located on the target-body interface. One-dimensional (1-D), two ... Cite

Determination of cardiac geometry from impedance measurements

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings · December 1, 1989 The basic formulation and some preliminary results of the utilization of impedance based measurements for obtaining cardiac geometry information are presented. This geometrical information is required for forward and inverse bioelectric calculations and co ... Cite

The assumptions of isochronal cardiac mapping.

Journal Article Pacing and clinical electrophysiology : PACE · March 1989 Isochronal maps of cardiac activation are commonly used to study the mechanisms and to guide the ablative therapies of arrhythmias. Little has been written about the assumptions implicit in the construction and use of isochronal cardiac maps. These assumpt ... Full text Cite

Stimulus-induced critical point. Mechanism for electrical initiation of reentry in normal canine myocardium.

Journal Article The Journal of clinical investigation · March 1989 The hypothesis was tested that the field of a premature (S2) stimulus, interacting with relatively refractory tissue, can create unidirectional block and reentry in the absence of nonuniform dispersion of recovery. Simultaneous recordings from a small regi ... Full text Cite

Mapping the electrical initiation of ventricular fibrillation.

Journal Article Journal of electrocardiology · January 1989 Full text Cite

Cardiac mapping at Duke Medical Center.

Journal Article The American journal of cardiology · January 1989 CLINICAL PERSPECTIVE: Ventricular fibrillation is a major, but little understood, cause of death. Although defibrillation with electric shock has been in use for several decades, and although many advances have been made in the design of defibrillators (in ... Cite

Cardiac mapping system for the quantitative study of internal defibrillation

Journal Article IEEE/Engineering in Medicine and Biology Society Annual Conference · November 1, 1988 A mapping system for studying the mechanism of electrical defibrillation is described. The specific benefits this system offers for defibrillation research are a dynamic range that extends from microvolts to hundreds of volts, the ability to respond to rea ... Cite

Self-documenting data structure for cardiac mapping

Journal Article IEEE/Engineering in Medicine and Biology Society Annual Conference · November 1, 1988 A data structure has been implemented for a multichannel cardiac mapping system that contains the complete state of the system at any time. This scheme frees the investigator from the responsibility of continuously recording system parameters during the co ... Cite

Mechanism of ventricular defibrillation

Journal Article IEEE/Engineering in Medicine and Biology Society Annual Conference · November 1, 1988 A summary is presented of findings about the mechanisms by which a shock succeeds or fails in halting ventricular fibrillation. It is shown that earliest activations following a subthreshold defibrillation shock occur in regions of low potential gradient g ... Cite

Influence of shock strength and timing on induction of ventricular arrhythmias in dogs.

Journal Article The American journal of physiology · October 1988 We delivered strong shocks via electrodes on the left ventricular apex and the right atrium in seven dogs during the T wave of atrial pacing while recordings were made from 56 epicardial electrodes. After shocks that induced arrhythmias were given, the ear ... Full text Cite

Workstation network for cardiac electrophysiology

Journal Article Computers in Cardiology · September 1, 1988 A system based on a network of engineering workstations has been developed for data acquisition and analysis in multichannel cardiac mapping. The system consists of a microcomputer-controlled data-acquisition front end, the network of workstations, and the ... Cite

Extracellular field required for excitation in three-dimensional anisotropic canine myocardium.

Journal Article Circulation research · July 1988 It is not known how well potential gradient, current density, and energy correlate with excitation by extracellular stimulation in the in situ heart. Additionally, the influence of fiber orientation and stimulus polarity on the extracellular thresholds for ... Full text Cite

Transmural activations and stimulus potentials in three-dimensional anisotropic canine myocardium.

Journal Article Circulation research · July 1988 Epicardial and endocardial pacing are widely used, yet little is known about the three-dimensional distribution of potentials generated by the pacing stimulus or the spread of activation from these pacing sites. In six open-chest dogs, simultaneous recordi ... Full text Cite

Mechanism of ventricular vulnerability to single premature stimuli in open-chest dogs.

Journal Article Circulation research · June 1988 To determine the mechanism of ventricular vulnerability to electrical stimulation, we simultaneously recorded from 120 transmural electrodes in a 35 X 20 X 5-mm portion of right ventricular infundibulum in seven dogs. Baseline pacing (S1) was performed fro ... Full text Cite

Comparison of time domain and frequency domain variables from the signal-averaged electrocardiogram: a multivariable analysis.

Journal Article J Am Coll Cardiol · May 1988 The relative values of the unprocessed signal-averaged electrocardiogram (ECG) and time domain analysis and frequency domain analysis of the signal-averaged ECG were compared in 36 patients with sustained monomorphic ventricular tachycardia and a remote my ... Full text Link to item Cite

Predicting endocardial potentials from epicardial potentials for external stimuli

Journal Article IEEE/Engineering in Medicine and Biology Society Annual Conference · January 1, 1988 A model is presented for calculating the potential field in the heart for externally applied current knowing only the epicardial potential distribution. To test the model, a comparison is made between potentials predicted by the model and those measured in ... Full text Cite

ADAPTIVE DATA REDUCTION ALGORITHM FOR MULTICHANNEL ELECTROGRAM RECORDING.

Journal Article IEEE/Engineering in Medicine and Biology Society Annual Conference · December 1, 1987 A method was developed to control the sample reduction ratio of the fan algorithm by adjusting the error tolerance as the data are processed. The feedback to the adaptation process is a weighted average of the time between output samples. The algorithm was ... Cite

Improved defibrillation thresholds with large contoured epicardial electrodes and biphasic waveforms.

Journal Article Circulation · November 1987 A reduction in the shock strength required for defibrillation would allow use of a smaller automatic implantable cardioverter-defibrillator and would reduce the possibility of myocardial damage by the shock. Most internal defibrillation electrodes require ... Full text Cite

Simultaneous multichannel cardiac mapping systems.

Journal Article Pacing and clinical electrophysiology : PACE · March 1987 There is much current interest in simultaneous multichannel cardiac mapping. In this paper we give recommendations for the construction of a cardiac mapping system. Because the field of cardiac mapping is relatively young, optimum mapping techniques and al ... Full text Cite

DATA STREAM FORMATTER FOR A CARDIAC MAPPING SYSTEM.

Journal Article IEEE/Engineering in Medicine and Biology Society Annual Conference · December 1, 1986 A data stream formatter for a 128-channel mapping system was constructed which combines real-time variables and digitized waveforms into information packets. The variables are formatted by a microprocessor once per millisecond creating, with the digitized ... Cite

INTRAOPERATIVE CARDIAC MAPPING.

Journal Article IEEE/Engineering in Medicine and Biology Society Annual Conference · December 1, 1986 There are several approaches to the design of a mapping system for use during the intraoperative study of cardiac activation. The authors present a brief overview of several designs currently in successful use, discuss attributes desirable in a clinical ma ... Cite

The potential gradient field created by epicardial defibrillation electrodes in dogs.

Journal Article Circulation · September 1986 Knowledge of the potential gradient field created by defibrillation electrodes is important for the understanding and improvement of defibrillation. To obtain this knowledge by direct measurements, potentials were recorded from 60 epicardial, eight septal, ... Full text Cite

Determination of effects of internal countershock by direct cardiac recordings during normal rhythm.

Journal Article The American journal of physiology · May 1986 Recording cardiac electrical activity after a countershock has been limited by amplifier saturation. Modifications to our computer-assisted mapping system allowed us to record electrical activity from 56 epicardial electrodes within 5 ms of the end of a co ... Full text Cite

Activation during ventricular defibrillation in open-chest dogs. Evidence of complete cessation and regeneration of ventricular fibrillation after unsuccessful shocks.

Journal Article The Journal of clinical investigation · March 1986 To test the hypothesis that a defibrillation shock is unsuccessful because it fails to annihilate activation fronts within a critical mass of myocardium, we recorded epicardial and transmural activation in 11 open-chest dogs during electrically induced ven ... Full text Cite

HIGH-SPEED MEMORY FOR THE ACQUISITION AND ANALYSIS OF DATA FROM CARDIAC MAPPING STUDIES.

Journal Article Computers in Cardiology · December 1, 1984 The acquisition and analysis of data from cardiac mapping studies require long-term offline recording as well as short term storage in a buffer device accessible to the host computer. A fast bulk memory has been implemented to buffer digitized electrophysi ... Cite

Time limits for submersion of canine left ventricular biopsies in cold isopentane.

Journal Article The Journal of surgical research · June 1982 Full text Cite

A rationale for the use of sequential coronary artery bypass grafts.

Journal Article The Journal of thoracic and cardiovascular surgery · May 1981 The use of sequential coronary artery bypass grafts has been advocated because of improved graft runoff and increased blood flow through the graft with this technique. To examine the influence of runoff, quantitated in terms of coronary vascular resistance ... Cite

Predicting patterns of epicardial potentials during ventricular fibrillation

Journal Article IEEE Trans. Biomed. Eng. (USA) Ventricular fibrillation (VF) is a fatal cardiac arrhythmia, characterized by uncoordinated propagation of activation wavefronts in the ventricular myocardium. Short-term predictions of epicardial potential fields during VF in pigs were attempted using lin ... Full text Link to item Cite