New fiber-optic tip for laser angioplasty

A class of fiber tip radiating laser light mainly along a cone coaxial to the fiber has been extensively studied in the past few years, and tests have been carried out, for example, in gastroentherology to remove occluding cancers. Their interest in treating obstructions in blood vessels or bronchos is also well known. In practice, however, these fiber tips consisting of cones or truncated cones are not safe in medical applications, in particular, in endoscopy. The cones indeed still radiate a non-negligible part of the light on-axis, particularly in the case of truncated cones. In these cases, the wall of vessels or other cavities can be damaged. Moreover, the conical tips can easily break. Recently more study sapphire tips have become available, but their size frequently does not fit the vessel lumen while the high refractive index results in a different optical behavior with respect to quartz cone tips. For these reasons a new probe has been studied, particularly for laser angioplasty, consisting of a cone fiber tip inserted in a quartz microcapsule. This capsule is sealed on the top by a toroidal-shaped lens structure, which avoids the on-axis radiation and gives rise to a sharp corolla-shaped beam. A typical overall radiation diagram shows a dark central cone with half-aperture of 30-450, depending on the aperture of the cone tip, surrounded by a bright crown with uniform intensity