We studied the ablative effect of a long-pulse excimer laser (XeCl, 308nm, pulse-width; 70ns, pulse-energy: 42mJ/pulse) on porcine myocardium, and compared that with that of a short-pulse one (308nm, 2Ons, 12mJ/pulse) which we had used before. In the second experiment, after coupling this long-pulse excimer laser light into a quartz fiber (400,μm core-diamter), we measured the distal fiber-end laser energy and examined the ablative effect of the laser transmitted through the fiber.
In result, the cuts produced with the long-pulse laser clearly defined such sharp edges as with the short-pulse one. With the both long-and short-pulse laser, the depth of cuts increased with the number of pulses and the pulse repetition rate. The width of discoloration around the cut margin also increased with the number of pulses and the pulse repetition rate. However, as a whole, the width with the long-pulse was broad er than that with the short-pulse, which showed the thermal injury with the long-pulse was a little more than with the short-pulse. In the second experiment about the fiber transmission, the distal fiber-end power of 16mJ/pulse (128mJ/mm²) with the long-pulse was obtained successfully, compared with 4mJ/pulse with the short-pulse. Besides, the ablative effects of the laser transmitted via the fiber were little different between the long-and short-pulse, though the thermal injury was somewhat more with the long-pulse.
The result suggested the ablative effect of the long-pulse excimer laser were little different with the shoht-pulse, except a slight increase of thermal injury with the long-pulse, and that the elongation of pulse width could make it easy to couple the laser light into the fiber. Therefore, it was expected we would be able to employ this long-pulse excimer laser device to clinical laser angioplasty in no distant future.

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Photodynamic therapy (PDT) is one of modes of treatment for malignant tumors. In PDT, Argon-dye laser (ADL) irradiation following administration of hematoporphyin derivatives (HpD) is generally used. However, the poor tissue penetration and activation of photosensitisers of the ADL, are still problems with PDT. The Pulse-wave gold vapor laser (GVL) is considered to have better tissue penetration than that of the ADL, so we compared the efficacy of GVL and ADL., in PDT, by means of nude mice transplanted human gastric cancer.
Tumor size reduction and complete remission was obtained in the mice given GVL irradiation at 280mW/cm² for 3 minutes with HpD (10mg/kg). The similar responce was obtained in the mice treated with the GVL at 280mW/cm² for 10 minutes with or without HpD. On the other hand no effect of PDT was obtained in the mice given ADL irradiation at 280mW/cm² for 10 minutes even with HpD. In the GVL group, the intra-tumor temperature was increased significantly.
It was concluded that GVL was superior to the ADL for PDT,because it had better tissue penetration, large power output, and an added hyperthermic effect.

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The excirner laser has the possibility of being a valuable tool which can precisely ablate a specific location within central nervous (CN) tissue without heat-injury effects. We have examined the morphological changes of excirner laser irradiated injured tissue in the dorsal column of rat spinal cord. Excimer laser (Kr-F: 248nm) irradiation with 10, 20 and 30 mJ energy produced sharp spinal cord transection without edema and axonal destruction around the lesion. At the energy of 50 mJ and 75 mJ laser irradiation the edges of tra.nsected lesion flared over the surface of the spinal cord with loss of glial cells and spliting of myelin sheaths of axons. Transmission and scanning electron microscope revealed that the excimer laser can sharply and uniformly transect the various types of composed elements (i. e., rnielin sheaths, glial cell, meningial cells, and axons), of CN tissue, in situ through out this experiment. No morphplogical abnormalities caused by thermal effects were detected. These results suggested that the excimer laser is a valuable tool for making sharp transections in spinal cord when employing appropriate power setting.

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Low power laser was irradiated on pain spots of II healthy volunteers. Two pain spots were selected by pin prick methods on the inside of the forearm of each volunteer. Two other spots were also chosen as control, which were not pain spots. The spots were as follows: uncolored non-pain spots (C1) black colored non-pain spots (C3), uncolored pain spots (C2) and black colored pain spots (C4). The spots were randomly irradiated.
Irradiation on Cl elicited pressing sensations in two of eleven and the mean of visual analogue scale (VAS) were 0.18, on C2, stabbing pain sensations occurred (mean of VAS; 1.64), on C3, prickling pain sensations occurred (mean of VAS; 2.41), on C4, unbearable pain occurred (mean of VAS; 4.32).
The mean value of VAS for the irradiation of each spot was significantly getting greater in the following order of Cl, C2, C3, C4.
The cause of analgesic effect of low power laser may be the stimulation of some nociceptors of the skin.

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