Biomedical subjects

Patrick D Wolf

Publications and source records attributed to Patrick D Wolf.

23 records · Page 2Linked to original sources

PubMed2003

Two multichannel integrated circuits for neural recording and signal processing.

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. Device B is a 16-channel two-stage analog signal processor with differential amplification and high-pass filtering. It features selectable gains of 250 and 500 V/V as well as reference channel selection. The resulting amplifiers on Device A had a mean gain of 1.99 V/V with an equivalent input noise of 10 microV(rms). Those on Device B had mean gains of 53.4 and 47.4 dB with a high-pass filter pole at 211 Hz and an equivalent input noise of 4.4 microV(rms). Both devices were tested in vivo with electrode arrays implanted in the somatosensory cortex.

Action Potentials↗

PubMed2002

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

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 5 MHz in a 12 Fr catheter. The system features real-time three-dimensional image rendering and produces up to 60 volumetric scans per second. Using an open-chest sheep model, real-time three-dimensional images of anatomic landmarks were obtained, including the pulmonary veins and coronary sinus, which are of value in electrophysiological procedures. In vivo radio frequency ablation procedures in the right ventricle were also monitored, which yielded lesions of high image contrast.

Animals↗

PubMed2002

Feasibility study for real time three dimensional Doppler intracardiac echocardiography.

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 a 12 French catheter lumen. The transducer configuration may be side scanning or beveled with respect to the long axis of the catheter lumen. We have also included six electrodes to acquire simultaneous electrocardiograms. We have measured Doppler signals in two phantoms, a string phantom and a pulsatile flow phantom. Using an open chest sheep model, we inserted the catheter into the cardiac chambers to study the utility of in vivo 3D intracardiac Doppler echocardiography.

Animals↗

PubMed2002

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

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 pacemaker lead, we used the stylet as a transmitter to track the vibrating tip in a 3D ultrasound scan. In another approach, we connected the stylet to a piezoelectric actuator vibrating in the range 0.5-5 kHz so that the tip of the stylet was imaged using the color Doppler feature of the real time 3D ultrasound scanner. In both approaches, tracking of the isolated stylet showed good accuracy. However, neither approach offered sufficient signal-to-noise ratio to detect the vibration within the lumen of an intact pacemaker lead.

Animals↗

PubMedDate not supplied

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

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-dimensional bidomain model that incorporates measured fiber orientations. Epicardial electrograms were recorded from canine left ventricles during and after unipolar pacing using a 528-channel electrode plaque. Fiber directions throughout the tissue were estimated from diffusion-weighted MRI and from pace mapping. Electrograms were computed in the bidomain model with experimentally derived properties during paced activations at the same spatiotemporal resolution as those recorded experimentally. Epicardial potentials from model and experiment were directly compared, and sensitivities of these comparisons to reference electrode location and to the choice of material properties were analyzed. The comparisons performed here demonstrate, that (1) the stimulus artifact can be used to estimate the in vivo myocardial fiber architecture, (2) the correlation between simulated and experimental electrograms decreases with increasing pacing depth, and (3) the quantitative comparisons between bidomain model and experimental data are sensitive to both the description of the fiber architecture, and the location of the unipolar reference electrode, but relatively insensitive to moderate changes in the bidomain conductivities.

Animals↗