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Low of middle energy irradiation with helium-neon laser (LLLT) appears to be a simple atraumatic technique for the prevention and treatment of mucositis of various origins. Preliminary findings obtained by Ciais et al prompted randomized multi-center, double-blind trials to evaluate LLLT for the prevention of a acute chemo- and radiation- induced stomatitis. Irradiation by LLLT corresponds to local application of a high photon density monochromatic light source. Activation of epithelial healing on LLL-treated surfaces, the most commonly recognized effect, has been confirmed by numerous in vitro studies, and is a function of cell type, wavelength, and energy dose. The mechanism of action at a molecular and enzymatic level is currently being studied (detoxification of free-radicals).

In order to find out the comparative clinical effects of coherent and noncoherent low power light, wedivided 74 patients with sciatics in three groups, treated with the same energy dose, as follows: - A group: with JR continuous diode laser (3 mW power); - B group: with noncoherent JR diode (9 mW power); - C group: with placebo laser.The positive results were 66.66% for A group, 52.00% forB group and 36.3 6% for C group. We conclude, after these preliminary results, that coherent low power light has superior clinical efficacyversus noncoherent light and placebo laser, when used the same energy dose.Key words: low power laser, sciatics, noncoherent light.Low power lasers (LPL) effects in the treatment of rheumatic diseases is well known although rathercontroversial1' 2, 3 As many other authors2' ' we have already reported good clinical results in the LPLtreatments, especially in rheumatic diseases6' . On the other hand, noncoherent light (red or infrared) hasproved similar effects as coherent light, but only in basic research2. So we tried to fmd out the clinical efficacy

One of the main problems which arise employing PDT is the patient's sensitization to the sunlight during a 4 - 6 week period after the i/v photosensitizers injection. Applying PDT for patients with head and neck cancer there often is the possibility to inject photosensitizer (the doses of photosensitizer used were many times smaller than in ordinary PDT) intra-arterially (i/a). This is followed by immediate tumor irradiation with laser light. The absorbed light's energy dose is the same as the dose usually used during the PDT. Since 1989 172 head and neck tumors were treated by us applying ordinary PDT and for 17 foci of oral cancer we provided intra-arterial photodynamic therapy. The result of i/a PDT was the same as in usual usage of PDT. But i/a PDT enables the usage of much smaller doses of photosensitizer. Patients need not be protected from the sunlight. I/a PDT enables us also to use effective but quickly splitting photosensitizers.

The decay of the surviving cell fraction, F, during photodynamic treatment of a cell population, F0, vs. energy dose obeys an exponential law. The integrated logarithmic form yields a straight line with intercept 0 and slope -k. The reciprocal slope yields LD90, i.e., the energy fluence (J/cm2) necessary to kill 90% of the cell population F0. In reality there are deviations from this simple set of equations. At low power densities most photosensitizers are unable to kill cells. This leads to an `optical threshold' without cell destruction but frequently with cell stimulating effects, so called `overshots.' This general phenomenon occurs in a very pronounced form with melanotic melanoma cells.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

As optical lithography moves into the area of submicron geometries, an increased understanding of lithographic process parameters is required. One area which requires careful examination is the interaction of the photoresist with specific spectral components of the actinic light. This will allow the photoresist performance to be separated from the performance of the imaging optics. An accurate indication of photoresist performance requires the measurement of photoresist response to a specific wavelength and energy dose. The spectrosensitometer reported on here was developed to address this need.