Side-firing fibers are used to provide coagulative therapy to the urologic tract. These fibers use different optical technologies to deflect the beam transverse to the fibers' optical axis. This produces emitted beams which differ in both beam direction and divergence angles. The relative optical performance of 13 fibers was studied in an optical phantom suspension. The fluence rate distribution created by each side-firing fiber was determined. The fluence rate distribution accounts for both the direct and spurious beams emitted from side-firing fibers as well as the light scattering produced by the target tissue. Based upon limited clinical dosimetry studies, the relative fluence rate distribution appears to indicate general exposure conditions for the evaluated fibers. © 1999 Society of Photo-Optical Instrumentation Engineers.

Background and Objective: Sapphire and sculpted silica fiber scalpels were evaluated for performance as they aged. Performance was determined by measuring their useful lifetime, forward transmission, incision depth, and the thermal coagulation thickness at the sides and bottom of the incision.Study Design/Materials, and Methods: Aging was performed with a chicken breast model. Performance measurements were made at periodic intervals. Sapphire scalpels were cooled with air or saline.Results: The air-cooled, frosted sapphire scalpels had the longest useful Lifetime, whereas the saline-cooled, frosted sapphire scalpels had the shortest. Aging deteriorated the forward transmission of the sculpted silica fiber scalpels the most. Little difference was found between the averages of all incision measurements. Two of the saline-cooled, frosted sapphire scalpels fractured during the aging process.Conclusion: Aging influences the scalpel lifetime, but there was no evidence that the aging process significantly affected the incision size. (C) 1995 Wiley-Liss, Inc.

This study evaluated the performance of sapphire and fused silica hemispherical tips under the same exposure conditions. Lesions produced in the chicken breast and a blood field were sectioned for light and transmission polarizing microscopy. Lesion size and thermal damage area were recorded as a function of the tips accumulated exposure. The tips transmission was measured after every 1,000 J of exposure. Fused silica tips lasted for ∼5,000 J and experienced significant surface and transmission deterioration. The sapphire hemispherical tips lasted for > 12,000 J with no surface and transmission deterioration. Lesions produced with the fused silica tips generally increased in depth with use, and depths of 6 mm were common. Lesions produced by the sapphire tips were subsurface spherical areas of coagulation with the tissue surface relatively intact. This difference in resulting lesions may be attributed to the higher thermal conductivity of sapphire. © 1994 Wiley‐Liss, Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.

Round sapphire and silica tips have been studied as surgical probes for focusing Nd:YAG laser radiation during various surgical indications. Since most of these data have been obtained with silica tips from Surgical Laser Technology, there are limited data on the physical performance of round sapphire tips. An investigation of round sapphire tip performance during tissue ablation was undertaken. Nd:YAG laser power was delivered in repetitive 2-sec exposures to a round sapphire tip placed on fresh skinned chicken breast. Total exposures of 1,000 J were performed at different saline perfusion rates. The tip's performance in terms of tissue perforation rate, blanched tissue area, tissue heating rate, and forward transmission was measured. Best tip performance occurred at the lowest cooling rates and was independent of the tip's forward transmission value. No physical deterioration of the tip's optical surface was observed. Round sapphire tip performance in a saline field is primarily determined by the tip's temperature.

Studies were made of the propagation of both continuous wave, all line, argon ion (515,496,488,476 nm) and Nd:YAG (1060 nm) laser radiation from a spherically-tipped optical fiber through a blood-saline solution. It was found that the transmission of the argon ion laser light through the mixture increased as the power emitted from the tip increased. The transmission of Nd:YAG laser radiation through a similar mixture showed a reduction in transmission as power increased.

Abstract DNA damage from photon scatter or beam spread during UV excimer laser irradiation was investigated using the induction of bacteriophage lambda in E. coli BR339. Prophage induction in these cells leads to the production of β‐galactosidase which can be detected colorimetrically by the application of appropriate substrates. An agar surface overlayed with BR339 cells was placed at various distances from the focal point of a converging lens and exposed to either 193 or 248 nm laser radiation. Energy densities ranging from approximately 5 mJ/cm2 to 30 J/cm2 were used. Ablation with 193 nm laser radiation produced an 800 u, m wide clear ‘trench’ surrounded by a 500 μm zone of cells in which lambda had been induced. Following ablation with 248 nm laser radiation, the zone of induction was several millimeters wide. Exposures to 193 nm radiation at 170 mJ/cm2/pulse produced visible ablation of the agar surface at 1.7 J/cm2. Lambda induction was observed surrounding cleared ablation areas. The presence of induction in this system suggests that both 248 and 193 nm excimer laser radiation delivered at high energy densities has sufficient spread or scatter to damage DNA in cells surrounding areas of ablation.

The optical emission pattern of experimental sphere-tipped fibers and an assortment of shapes of sapphire-tipped fibers has been measured. The emission patterns were recorded in both air and water. These patterns show that cone and wedge shaped tips unexpectedly have focusing properties. The observed patterns help give an understanding of the results that the tips produce on tissues. The optical analysis suggests ways of improving tip designs.

Fiber optical delivery of laser power for surgery allows considerable freedom for external procedures and reduces the need for invasive surgery by using the natural vessels of the body. Irradiation of undesirable tissues is controlled by the optical properties of the emitting tip of the fiber. Numerous types of tip have been analyzed to characterize the emission patterns of the laser radiation. Ball tips being considered for angioplasty have been studied in air, liquid and solids. Sapphire cone tips, rounded tips, and other tip configurations have also been studied in air, liquid, and solids. The emission patterns have been compared to a simple optical theory which predicts the performance for near paraxial rays. Implications for improved designs can be seen.

A laser light radiometer has been developed for the Electro-Optics Branch of the Center for Devices and Radiological Health (CDRH). The radiometer measures direct laser radiation emitted in the visible spectrum. Based upon this measurement, the instrument's microprocessor automatically determines at what time duration the exposure to the measured laser radiation would exceed either the class I accessible emission limits of the Federal Performance Standard for laser products or the maximum permissible exposure limits of laser user safety standards. The instrument also features automatic background level compensation, pulse measurement capability, and self-diagnosis. Measurement of forward surface illumination levels preceding HpD photoradiation therapy is possible.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text David D. Royston, Zhiyuan Geng, and Jianguo Liu, "Silicon radiometer whose response is independent of operating temperature," Appl. Opt. 23, 785-786 (1984) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Some laser effects in laser lght shows irradiate audiences directly with laser radiation. This laser radiation must be below Class I accessible emission limits. If actual radiometric measurements cannot be performed, a numerical analysis of the laser effect can be made to determine if the accessible laser radiation is below acceptable limits. An analysis is presented of the following laser light show effects: a sawtooth wave scan, a triangular wave scan, a sine wave scan, a circular Lissajous pattern, a stationary laser beam on a rotating mirror ball, and a scanning laser bean on a mirror ball. The level of laser radiation of the effect is computed as well as the length of time the effect remains below Class I levels.