PubMed · 8715016
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A Smith. 1995. Seeing the light.. https://pubmed.ncbi.nlm.nih.gov/8715016/
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PURPOSE: We developed a positioning method that does not depend on the positioning mechanism originally annexed to the linac and investigated the positioning errors of the system. METHODS AND MATERIALS: A small video camera was placed at a location optically identical to the linac x-ray source. A target pointer comprising a convex lens and bull's eye was attached to the arc of the Leksell stereotactic system so that the lens would form a virtual image of the bull's eye (virtual target) at the position of the center of the arc. The linac gantry and target pointer were placed at the side and top to adjust the arc center to the isocenter by referring the virtual target. Coincidence of the target and the isocenter could be confirmed in any combination of the couch and gantry rotation. In order to evaluate the accuracy of the positioning, a tungsten ball was attached to the stereotactic frame as a simulated target, which was repeatedly localized and repositioned to estimate the magnitude of the error. The center of the circular field defined by the collimator was marked on the film. RESULTS: The differences between the marked centers of the circular field and the centers of the shadow of the simulated target were less than 0.3 mm.
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BACKGROUND: Technologic advances have led to increased use of computers at home and in the workplace. It is estimated that more than 100 million workers in the United States and Canada will be using computers daily by the year 2000. Anecdotal reports have suggested a link between video display terminals (VDTs) and disease. This has generated much concern about whether electromagnetic radiation (EMR) emitted by VDTs cause illness among users. METHODS: We reviewed pertinent articles in the literature. RESULTS: Several studies have addressed the role of VDTs in disease causation, specifically whether EMR causes skin or ocular disease or obstetric complications. The data reviewed were inconsistent or methodically flawed. Therefore, a definitive conclusion cannot be drawn to support the hypothesis that EMR produced by VDTs causes disease. CONCLUSIONS: We believe continued research should be done to further define and elucidate the risk of EMR produced by VDTs.