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Biomedical subjects

J G Webster

Publications and source records attributed to J G Webster.

At least 91 records · Page 5Linked to original sources
PubMed1984

Human surface electrogastrograms: ac and dc measurements.

Both ac and dc abdominal electrical recordings were made on fasted and fed human subjects using a spatial array of 18 cutaneous, biopotential electrodes. Controlled skin puncture minimized cutaneous potentials. Pregelling electrodes minimized drift. The recording sessions were between two and three hours in length. We determined the optimal location for ac recording of a 3 cpm wave at a location on the midline approximately 5 cm below the xiphoid process. Seven cpm waves were also observed in one individual at the same location. The dc values were fed into a Hewlett Packard 1000 computer which interpolated the intermediate values and plotted two-dimensional contour plots which were examined visually. The right abdominal surface was typically 1.8 mV more negative than the left for prefeeding. The left abdominal surface was typically 4.6 mV more negative than the right for postfeeding. We propose an electrical model that explains these results during the fasted state.

Abdomen↗
PubMed1983

Electrical impedance imaging of the thorax.

In this paper, we propose to develop a new imaging technology, computerized impedance tomography (CIT) for imaging the thorax. Our study involves reconstructing images of thoracic transverse plane impedance distributions noninvasively and nondestructively and exploring the potential of CIT. We overcome the reconstruction problem due to nonlinear and nonplanar current paths in impedance imaging by solving Laplace's equation numerically for every iteration and by using a new back-projection algorithm to modify the impedance profile. We discuss advantages and disadvantages associated with impedance imaging, the computer model, and back-projection algorithms used in reconstructing impedance images. We present reconstructed impedance images with 8 projection angles and different projection methods. We identify important variables affecting the quality of reconstructed images, and discuss the resolution and accuracy of this imaging technique. We summarize numerical aspects, computer requirement, and limitations of impedance imaging. We also discuss the future of impedance imaging.

Computers↗