Laser optical fiber systems have been developed which incorporate an optical fiber assembly to conduct laser radiation from a remote location to a site at which a cutting procedure is to be performed. A lens is commonly attached to the optical fiber to focus and direct the laser radiation at the desired location.
In some applications, the laser cutting apparatus has been combined with an otherwise conventional balloon angioplasty catheter apparatus. The dilatation balloon catheter of the angioplasty apparatus could be advanced through the channel cut by the laser and then an angioplasty procedure could be performed in the conventional manner.
While such laser angioplasty systems were believed to hold great promise, they were later seen to have important limitations. Among these limitations was the inability to combine the needed flexibility of a small optical fiber with the ability to produce by ablation a large lumen. Later devices which utilized a ball tip were able to ablate large lumens if lasers were used that produced some lateral heating. This later heating can present risks to arterial walls and other tissue which is not desired to be ablated. Although pulsed lasers ablated without producing a large lateral thermal component, the lumen produced was smaller that the diameter of the ball lens.
Another limitation was that the apparatus was not structurally strong. This presents difficulties when the lumen produced is smaller than the diameter of the lens, because the lens has an enhanced risk of detachment upon retraction of the apparatus.
As other applications of laser surgery, especially in vivo procedures, have been developed, similar problems have surfaced. This is particularly true when the apparatus is to be manipulated from a remote location by means of a catheter. In such cases, the problem of confining the pattern of laser radiation to a predetermined region directly in front of the distal tip of the fiber has become very important and the subject of intense interest of designers.
These problems can be seen to be the result of the lenses which are presently used in fiber optical laser surgical systems. The typical distribution of radiation from prior art devices is Gaussian, i.e. is shaped like a bell curve. An ideal lens would confine all of the radiation to a region immediately forward of the catheter, and would distribute it evenly. Thus, the shape of such a distribution of radiation would be shaped like a square wave. In this manner the tissue directly in front of the lens would be cut and the device readily advanced.
In addition, the radiation ideally should be directed forward in a pattern as wide as the lens itself, in order to properly clear a path for the advancing apparatus. If this is not done, the advancing apparatus can trap flaps of uncut tissue which act to dislodge, or otherwise disturb, the lens upon retraction of the apparatus from the body. The desired radiation pattern thus is one where radiation is directed forward uniformly over the width of the lens while having negligible radiation beyond such an area. Such a radiation pattern cannot be achieved with typical prior art optical fiber laser lenses.
There remains, therefore, a need for an optical fiber system that allows the accurate direction of laser radiation to a selected site and reduces the chance of damage to the patient from dislodging or disintegrating of the lens end of the optical fiber. It would also be beneficial if such a system were readily adaptable to catheter configurations that could be used for a variety of surgical and intravascular procedures.
Broadly, it is the object of the present invention to provide an improved laser optical fiber lens apparatus and method for creating such an apparatus.
It is a further object of the present invention to provide a laser optical fiber lens apparatus capable of producing radiation patterns of a desired shape.
It is a still further object of the present invention to provide a laser optical fiber lens apparatus capable of directing radiation approximately uniformly forward over an area the size of the lens, with minimal radiation directed beyond that area.
It is a yet further object of the present invention to provide a laser optical fiber apparatus with improved attachment of the lens to the optical fiber.
These and other objects of the present invention will be apparent to those skilled in the art from the following detailed description of the invention and the accompanying drawings.