Surgery – Instruments – Light application
Reexamination Certificate
1999-07-15
2001-12-11
Gibson, Roy (Department: 3739)
Surgery
Instruments
Light application
C606S018000, C607S009000
Reexamination Certificate
active
06328733
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to medical lasers, and relates more particularly to a hand-held laser scanner that generates a scanned pattern of constant size regardless of the positioning of the laser scanner with respect to a treatment surface.
2. Description of the Relevant Art
Historically, surgical incisions in tissue have been performed with sharp metal cutting instruments. More recently, lasers have become the tool of choice in many medical procedures to cut and treat tissue. Laser beams can be accurately focused on tissue to cut many desired shapes and depths. The slit incision, a very narrow elongated incision, is especially appropriate for laser surgery. Surgeons can make these narrow incisions by passing a focused laser beam over the target tissue.
One medical procedure where slit incisions are desired is hair transplants. Hair transplants have become a common cosmetic procedure, particularly for the treatment of male pattern baldness. In a hair transplant procedure, a piece of the patient's skin having healthy growing hair is removed from a donor region on the scalp and implanted into a hairless, recipient region. This process involves cutting a hole or slit into the recipient region so that the new plug of hair can be inserted. Slit grafting is modernly used because of its many cosmetic and medical advantages over circular punching.
Historically, slit grafting has been accomplished by cutting a slit into the recipient region with a scalpel. More recently, lasers have been used. A laser is more advantageous because the size and shape of the incision can be more accurately controlled. A laser beam, usually a pulsed infrared beam, is focused onto the scalp. The exposure can be controlled to remove the amount of skin needed for the hair graft dimensions. Another advantage of using lasers to cut or remove skin is the coagulating effects of the laser light that minimizes bleeding and pain. Further, the laser radiation removes the skin in the slit it creates thereby creating room for the new plug of hair to be placed inside. A laser assisted hair transplant method is described in U.S. Pat. No. 5,360,447, which is assigned to Coherent, Inc, the assignee of the present application.
A laser beam can be accurately focused on the scalp by a variety of optical delivery systems. One such system is marketed by Coherent, Inc. in conjunction with its sealed carbon dioxide medical laser system under the name Ultrapulse 5000. To create a slit, the surgeon positions the output of the optical delivery system so that the beam will impinge on the target tissue. The surgeon then presses a footswitch which opens a shutter that allows light to exit the output end of the optical delivery system. The doctor then moves the output end over the target tissue until the desired slit width and depth is created. This procedure is followed for every slit made in the target tissue.
The drawback to this optical delivery system is that it takes time and skill to create a series of slits of the desired dimensions and layout. Since the number of slits required can be as numerous as the number of individual hair follicles being transplanted, the time and skill required to create accurate slits in the recipient area can be great. Furthermore, the placement of each slit is important, because uniform patterns give a more natural appearance of the transplanted hair. Thus, there is a need for an optical delivery system that creates multiple slits in uniform patterns.
Lasers are also used surgically to treat relatively large areas of tissue in techniques such as ablation to remove disfigured skin. The spot diameter of the laser beam is typically larger in size and lower in power density as compared to lasers used to make incisions. Even though the spot diameter of the laser beam is relatively large, the area of treatment is usually larger than the area of the spot, which requires that the beam be scanned or otherwise moved across the area to be treated.
One approach to moving the laser beam across a treatment area is to scan the beam like a raster, back and forth in successive rows until the area is covered. One drawback to that approach is that successive rows can overlap with insufficient recovery time in between scans of successive rows, which can damage the tissue in the areas of overlap. Another drawback is that the pattern area covered by the laser can be dependent on the distance between the treatment area and the scanning device, which is not easily controlled if the laser instrument is handheld by the surgeon.
There is thus a need for an optical delivery system that creates an scanned laser beam in a uniform pattern regardless of the precise position of the treatment surface with respect to the laser instrument.
SUMMARY OF THE INVENTION
In accordance with the illustrated preferred embodiments, the present invention is a surgical laser handpiece that scans a laser beam onto a target tissue. The surgical handpiece, or hand-held laser scanner, has a lens and a scanning mirror located at a distance from the lens that is equal to or substantially equal to the focal length of the lens. The laser beam hits the scanning mirror and is reflected onto the lens in a pattern defined by multiple positions of the scanning mirror. The lens projects the laser beam pattern onto the target tissue so that the output beam exits the lens parallel to the optical axis of the lens. The projected pattern has a constant size regardless of the distance between the handpiece and the target tissue. In other words, any variation in the size of the pattern projected onto the target tissue is minimal as the spacing between the lens and the target tissue is varied.
In another aspect of the present invention, the laser beam incident on the scanning mirror can be focused light or collimated light. If the laser beam is focused on the scanning mirror, then the lens collimates the beam, resulting in an output beam having a spot size that does not vary with changing distance between the handpiece and the target tissue. The spot size of this output beam can be adjusted by varying the cone angle of the incident focused beam. If the laser beam incident on the scanning mirror is collimated, then the lens focuses the output beam, thus providing a concentrated laser beam useful for incisions. Beam conditioning optics located upstream of the scanning mirror can be used to focus the laser beam on the scanning mirror, to adjust the cone angle of the focused beam, and to adjust the size of the collimated laser beam incident to the scanning mirror. Preferably, the surgical handpiece of the present invention has two mirrors that are independently rotatable about orthogonal axes. The two independently rotatable mirrors permit two-dimensional patterns of the output beam to be generated.
Another aspect of the present invention is a method of scanning a laser beam onto a target tissue by generating a laser beam and delivering it to a scanning mirror, pivoting the scanning mirror to project the laser beam onto a lens, where the scanning mirror is one focal length upstream of the lens, and projecting the laser beam through the lens and onto the target tissue.
Still another aspect of the present invention is a method of ablating tissue using a laser beam by positioning an output end of a delivery device adjacent the tissue, energizing the laser to generate a laser beam, directing the laser beam within the delivery device through a scanning mirror and then a lens to the tissue, where the scanning mirror is located approximately one focal length from the lens so that the lens projects the laser beam along a path parallel to an optical axis of the lens, and moving the scanning mirror to project a pattern of laser beams on the tissue to be ablated.
The features and advantages described in the specification are not all inclusive, and particularly, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification and claims hereof. Moreover
Eitan Pearl Latzer & Cohen-Zedek
Gibson Roy
Lumenis Inc.
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