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Biomedical subjects

A Perlin

Publications and source records attributed to A Perlin.

10 recordsLinked to original sources
PubMed1992

Single optical fibre transducer for pressure measurement.

In a single optical fibre transducer, light is injected into a fibre through a fibre optic coupler, located at some distance from the distal end of the fibre. Injected light travels toward the front face of the fibre, where it exits in the shape of a cone. then, after reflection from a reflective surface, it is readmitted into the same fibre. The reflected beam of light travels back through the coupler, exits through the distal end of the fibre and illuminates the photosensitive area of a photo diode, where it is converted to an electrical current. Depending on which one of the parameters is allowed to vary the amount of the returning light, one can build a variety of different sensors. Among them are: linear/angular displacement sensors and their derivatives such as pressure or force sensors; transmittance sensors such as turbidity and chemical sensors; reflectance sensors such as temperature sensors, optical encoders and scanners, colourometric and other types of chemical sensors. In the case of the single optic fibre transducer (SOFT) made by Pearl Instruments (Chicago, II, USA), the reflective surface is made of a thin metal foil with 6 microns thickness and 1.25 mm diameter. Optical fibres are pf the multimode type with 55 microns diameter. Their numerical aperture is equal to 0.66. The SOFT head is 1.25 mm in diameter and has an overall length of 50 cm. The disposable part of the system contains the head, fibre, protective sheathing and plug. Its operating range is -15 to +300 mmHg, and +25 to +45 degrees C, and its resolution is +/- 1 mmHg.

Computer Simulation↗
PubMed1985

Mechanical and metallurgical properties of carotid artery clamps.

The mechanical and metallurgical properties of carotid artery clamps were evaluated. The pressure plate retreat propensity, metallurgical composition, surface morphology, magnetic properties, and corrosion resistance of the Crutchfield, Selverstone, Salibi, and Kindt clamps were tested. None of the clamps showed evidence of pressure plate retreat. The clamps differed significantly in their composition, surface cleanliness, magnetic properties, and corrosion resistance. The Crutchfield clamp was the only one manufactured from an ASTM-ANSI-approved implantable stainless steel (AISI 316) and the only clamp in which the surfaces were clean and free of debris. The Selverstone clamp was made principally from AISI 304 stainless steel, as was one Salibi clamp. The pressure plate on another Salibi clamp was made from a 1% chromium and 1% manganese steel. Machining and surface debris consisting principally of aluminum, silicon, and sulfur was abundant on the Selverstone and Salibi clamps. The Kindt clamp was manufactured from AISI 301 stainless steel with a silicate-aluminized outer coating. The Crutchfield and Selverstone clamps were essentially nonferromagnetic, whereas the Salibi and Kindt clamps were sensitive to magnetic flux. In the pitting potential corrosion test, the Crutchfield clamp demonstrated good corrosion resistance with a pitting potential of 310 mV and no surface corrosion or pitting by scanning electron microscopy examination. The Selverstone clamp had lower pitting potentials and showed various degrees of corrosion and surface pitting by scanning electron microscopy. The Salibi pressure plate had a very low pitting potential of -525 mV and showed severe corrosion. By metallurgical criteria, only the Crutchfield clamp is suitable for long term implantation.

Animals↗
PubMed1984

Intracranial clips: an examination of the devices used for aneurysm surgery.

A properly functioning aneurysm clip is of paramount importance in the surgical ablation of intracranial aneurysms. An appropriate match between the closing force needed to ablate an aneurysm and the force exerted by the aneurysm clip must be achieved. In this study, the opening and closing forces exerted by several commonly used aneurysm clips were tested. There was a strong correlation between the classification of the clips, according to the Dujovny system, and their mechanical behavior. Minimal variability among different lots of the same clip type and minimal hysteresis were generally exhibited by the alpha mobile fulcrum class clips, such as the Yasargil, Vari-Angle McFadden, Scoville, and Mayfield clips. Significant exceptions included several types of Mayfield and Drake clips. In contrast, pivot class clips generally showed twice as much lot variability among different lots, as well as a significant amount of hysteresis. Clips of this class include the Vari-Angle, Heifetz, and Pivot clips. Because significant variations in clip force exist and because several other factors can compound these differences, it is suggested that aneurysm clips be individually tested for their closing forces before they are used in an operation.

Humans↗
PubMed1983

Mechanical and metallurgical properties of vascular clips designed for temporary use.

Six commonly used surgical clips (Kleinert-Kutz, Pivot, Vari-Angle, Yasargil, Biemer, and Acland) that have been designated by their manufacturer as being suitable for temporary occlusion were studied in terms of their mechanical and metallurgical properties. Opening and closing forces were determined for all of the clips. Significant variations in clip force with respect to blade gap were found in all of the pivot-type clips. Metallurgical testing showed that all six clips exhibited properties that contraindicate long-term implantation.

Corrosion↗
PubMed1981

A variable-force microvascular clip.

An easily adjustable, variable-force microvascular clip is described. This clip is superior to other clips currently available because it is essentially three clips in one. Its advantages are that it can reduce the amount of table area needed to store clips during surgery and it offers the surgeon greater flexibility in the selection of clips with different closing forces. This clip was developed by modifying the segments of a basic alpha-type clip, designing a computer program to analyze the force contributions made by each segment of the clip, constructing several clips with different blade lengths, and testing them in a microvascular surgery research program. The clip we have developed is easy to use, reduces clutter on the instrument table, aand offers the surgeon a wide choice of closing forces with a minimal number of clips.

Humans↗
PubMed1980

Aneurysm clip testing meter.

The force that a vascular clip exerts when it is applied to a vessel is a critical factor in its safe and proper use. Permanent occlusion effected in the obliteration of aneurysms requires clip closure forces great enough to resist sliping, yet low enough not to damage the neck of the aneurysm. The authors consider the need for a device that can readily measure clip closing forces just prior to pre-surgical sterilization (immediately prior to implantation), and an instrument that meets that need is presented.

Aneurysm↗
PubMed1979

Temporary microvascular clips.

Selected commercially designated temporary clips (Acland, Biemer, Kleinert-Kutz, Variangle, and Yasargil) were applied for 1 hour to rat common carotid arteries. Scanning electron and light microscopic studies revealed varying degrees of endothelial damage. The authors believe that further improvements are needed in the design of temporary clips.

Animals↗
PubMed1976

Shunting, release, and distribution of nine and fifteen micron spheres in myocardium.

The shunting, release, and transmural distribution of 9 and 15 mu radioactive microspheres were compared in isolated hearts and intact hearts with and without adenosine triphosphate (ATP) vasodilation. ATP vasodilation caused increase shunting of 9 mu spheres but not 15 mu spheres (p less than 0.05). The transmural distribution of 9 and 15 mu spheres in left ventricle and septum were significantly different (p less than 0.01) and the difference was characteristic for the isolated heart and the nonvasodilated intact heart. There was no difference in distribution across the right ventricle. There appear to be significant differences in regional shunting as well as distribution in the intact heart. We found no systematic correction for comparing flows measured with 9 and 15 mu spheres.

Adenosine Triphosphate↗