Ruby laser is effective in treating pigmented skin tumors, such as melanomas and nevus. The conventional ruby laser unit, however, is limited in practical use due to its uneven beam distribution over the target area. To overcome this problem we have developed a new ruby laser system utilizing a kaleidoscope as an application head.
The spatial ununiformity of the kaleidoscope output as well as its efficiency varies depending on the kaleidoscope length, reflection ratio, the incident beam spread angle, incident position, etc. Therefore, the kaleidoscope has excellent characteristics for our purposes, when these items are set to proper values. Up to the present, however, there has been no theory to define the relationship between these factors. So, we have conducted research to establish such a theory. Basic data, which are indispensable in seeking an optimum design, have been collected by simulation.
During the research, we employed the total reflection method utilizing a dielectric substance to conduct simulations, and constructed a trial model based on these results. Its output energy is 20-40J/cm
2 over a 10
2mm irradiated area. The pulse interval is 1 msec. The spatial ununiformity of the output intensity on the kaleidoscope output surface was found to be below 12%, which is close to the simulated data.
After confirming the safety and clinical applicability of this system, we applied it to treating 20 patients suffering from nevus spilus. Irradiated by a 40J/cm
2 (1 msec) ruby laser, 18 out of the 20 cases showed favorable results, though the other two cases suffered recurrence.
The following problems remain to be solved in the future: to improve the efficiency of the kaleidoscope by applying a non-reflective coating to its input and output terminal surfaces; to develop an optical fiber for use with the laser beam to facilitate the system's operation. Clinical application of the system to study recurring cases is the future task.
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