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Biomedical subjects

A C Easty

Publications and source records attributed to A C Easty.

6 recordsLinked to original sources
PubMed2004

Infrared thermographic SAR measurements of interstitial hyperthermia applicators: errors due to thermal conduction and convection.

Thermal conduction and convection were examined as sources of error in thermographically measured SAR patterns of an interstitial microwave hyperthermia applicator. Measurements were performed in a layered block of muscle-equivalent phantom material using an infrared thermographic technique with varying heating duration. There was a 52.7% reduction in maximum SAR and 75.5% increase in 50% iso-SAR contour area for a 60-s heating duration relative to a 10-s heating duration. A finite element model of heat transfer in an homogeneous medium was used to model conductive and convective heat transfer during the thermographic measurement. Thermal conduction artefacts were found to significantly distort thermographically measured SAR patterns. Convective cooling, which occurs when phantom layers are exposed for thermal image acquisition, was found to significantly affect the magnitude, but not the spatial distribution, of thermographically measured SAR patterns. Results from this investigation suggest that the thermal diffusion artefacts can be minimized if the duration of the applied power pulse is restricted to 10 s or less.

Hot Temperature↗
PubMed1997

Magnetic resonance imaging of temperature changes during interstitial microwave heating: a phantom study.

Changes in magnetic resonance (MR) signals during interstitial microwave heating are reported, and correlated with simultaneously acquired temperature readings from three fiber-optic probes implanted in a polyacrylamide gel phantom. The heating by a MR-compatible microwave antenna did not interfere with simultaneous MR image data acquisition. MR phase-difference images were obtained using a fast two-dimensional-gradient echo sequence. From these images the temperature-sensitive resonant frequency of the 1H nuclei was found to decrease approximately by 0.008 ppm/ degree C. The method and results presented here demonstrate that noninvasive MR-temperature imaging can be performed simultaneously with interstitial microwave thermal treatment.

Biophysical Phenomena↗
PubMed1991

Development and evaluation of two automated methods for quantifying human muscle sympathetic nerve activity.

The microneurographic technique of directly recording muscle sympathetic nerve activity (SNA) in conscious humans was developed over 20 yr ago, but analysis and quantification of the resultant mean voltage neurogram has been largely by visual inspection by a trained observer. Two computer-assisted methods were developed to quantitate these bursts of efferent activity: peak detection, and ECG R-wave-triggered burst averaging. Peak detection was optimized using statistical techniques; burst averaging was compared to both the manual technique and to the peak detection method. Burst averaging was found to be the superior method because of its speed, consistency, and objectivity.

Action Potentials↗
PubMedDate not supplied

Electrosurgery smoke: hazards and protection.

Early discussion regarding smoke produced by both surgical lasers and electrosurgical machines concluded that the smoke produced by these instruments was little more than a malodorous nuisance. Animal and human studies to date, however, have suggested that this smoke is, indeed, dangerous. This smoke has been shown to be mutagenic and can contain bacteria and viruses, the HIV virus being the most notable. Furthermore, these particles are small enough to penetrate deep within the respiratory tract. In response to the concerns raised by these hazards, commercial smoke evacuation systems have been designed to greatly reduce the number of hazardous particles, as well as the noxious odor produced by electrosurgery and laser surgery. The efficacy of these systems, however, is dependent o n usage and placement close to the surgical site. This review paper presents the potential hazards of electrosurgical smoke, along with some guidelines on how to properly protect hospital staff and patients from these hazards.

Air Pollutants, Occupational↗
PubMedDate not supplied

Validating the integrity of one-way check valves for the delivery of contrast solution to multiple patients.

The infusion of contrast solution into multiple patients from a single infusion bag is desired in clinics concerned with the high cost of the solution. Using one-way check valves in the infusion line is a protection method to reduce the risk of blood-borne cross-contamination. The suitability of this method is assessed through testing of the operating characteristics of the valves and infusion system and the high back pressure testing of the valves. The results indicate that the use of back-flow valves can ensure the prevention of flow from the patient to the injector. Results also indicate that the use of sprung valves, those which require a significant forward pressure to open them, are more appropriate for this application.

Blood-Borne Pathogens↗