Molding of laser energy by shaped optic fiber tips.

The development of a new technique for laser recannalizing atheromatous vessels has inherent problems concerning heat damage to the vessel walls. A theoretical analysis of 2,100 light rays in large bulb end (output end) fibers compared to a standard flat end fiber showed (1) a much higher-intensity focus; (2) a 125.4% increase in number of output rays (with respect to number of input rays) in the convergent output beam, due to multiple reflections/refractions ("stars" and "triangles") and standing waves, in the large bulb end, compared to 48.6% in the flat end; (3) 83.69% energy in the converging beam of the large bulb end, compared to 46.1% energy in the flat end; and (4) a rapidly divergent beam after focus. Hence, theoretically a wide area of plaque could be burnt off more rapidly with less heat conduction into the vessel walls. Coupling efficiency was experimentally shown to be greatly increased by also having a bulb at the optic fiber input end.