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D T Delpy

Publications and source records attributed to D T Delpy.

132 records · Page 8Linked to original sources
PubMed1979

Continuous comparison of in vitro and in vivo calibrated transcutaneous oxygen tension with arterial oxygen tension in infants.

Transcutaneous PO2 simultaneously recorded by Drager and Radiometer electrodes on the abdominal skin was compared for six-hour periods with aortic PaO2 recorded by a Searle intravascular oxygen electrode. Ten newborn infants with serious respiratory illnesses, six of whom needed mechanical ventilation, were studied. The skin electrodes were heated to 44 degrees C and calibrated first in vitro, and then in vivo against the infant's PaO2. The results showed that 1) after in vivo calibration both skin electrodes gave an accurate estimate of PaO2 for six hours without resiting of the electrodes; 2) the Radiometer electrode gave as satisfactory an estimate of PaO2 after in vitro as after in vivo calibration; 3) the Drager electrode gave a significantly less accurate estimate of PaO2 after in vitro than after in vivo calibration; 4) no evidence suggesting that peripheral vasoconstriction interfered with the accuracy of estimation of PaO2 by the skin electrodes was found.

Arteries↗
PubMed1975

A catheter-tip capacitance pressure transducer.

A simple miniature capacitance pressure transducer is described. The operational characteristics of the device when mounted on the tip of a 6.3 F catheter are discussed and results of in vivo trials illustrated, using a commercially available catheter-tip pressure transducer for comparison.

Blood Pressure Determination↗
PubMedDate not supplied

A finite element approach for modeling photon transport in tissue.

The use of optical radiation in medical physics is important in several fields for both treatment and diagnosis. In all cases an analytic and computable model of the propagation of radiation in tissue is essential for a meaningful interpretation of the procedures. A finite element method (FEM) for deriving photon density inside an object, and photon flux at its boundary, assuming that the photon transport model is the diffusion approximation to the radiative transfer equation, is introduced herein. Results from the model for a particular case are given: the calculation of the boundary flux as a function of time resulting from a delta-function input to a two-dimensional circle (equivalent to a line source in an infinite cylinder) with homogeneous scattering and absorption properties. This models the temporal point spread function of interest in near infrared spectroscopy and imaging. The convergence of the FEM results are demonstrated, as the resolution of the mesh is increased, to the analytical expression for the Green's function for this system. The diffusion approximation is very commonly adopted as appropriate for cases which are scattering dominated, i.e., where mu s >> mu a, and results from other workers have compared it to alternative models. In this article a high degree of agreement with a Monte Carlo method is demonstrated. The principle advantage of the FE method is its speed. It is in all ways as flexible as Monte Carlo methods and in addition can produce photon density everywhere, as well as flux on the boundary. One disadvantage is that there is no means of deriving individual photon histories.

Health Physics↗