Abstract:
A mechanical element allows the tip of the handpiece of a dermatological treatment system to rotate to adjust for deviations in handpiece angle with respect to the surface of the treatment area. The tip may glide over the surface of the skin, the tip may include wheels or rotating cylinders on which the tip rolls across the skin, or the tip may be removed from the skin and placed in a new location in a stamping motion. The tip of the handpiece rotates around a single axis, or around two perpendicular axes, so that pressure on the tip moves the flat surface of the tip into proper orientation for planar contact with the skin. An element can be included in the handpiece to apply a restoring force on the tip so that the tip rests in its optimal position in the absence of external forces.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 60/939,817, “Pivoting Roller Tip for Dermatological Treatment Apparatus”, filed May 23, 2007, by Kenton Whitaker and Danica Wyatt. The subject matter of all of the foregoing is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to apparatus and method for energy delivery to dermatological tissue. More particularly, it relates to a systems and methods for delivering light via a handpiece that rolls or glides over skin or is generally moved from one location to another on the skin. 
     2. Description of the Related Art 
     Medical and aesthetic dermatological treatments are commonly performed by exposing skin to an appropriate quantity of energy at a wavelength absorbed by some component of the skin tissue. For example, energy can be targeted for selected absorption in blood vessels or hair follicles. Wrinkles, hyperpigmentation and scarring can be reduced by devices that target features of the water absorption spectrum. In some cases, a delivery mechanism that exposes only a fraction of the skin surface to light while sparing surrounding tissue may be preferred to a more aggressive treatment that ablates the full epidermis, because a fractional treatment reduces the risk of infection and better stimulates the wound healing response. 
     Prior medical laser systems have included mechanisms for controlling energy intensity, pulse duration, and size of treatment zones. Known methods often rely on both automated systems and interactive operator control to deliver an optimal treatment. One approach is to deliver light via a handpiece that gives the operator some degree of spatiotemporal control of exposure. Some handpieces are configured for delivering a fractional light exposure. A number of options exist for creating a pattern of exposure on the skin. Some systems deliver energy in a 2-D pattern that is stamped repeatedly onto the skin to cover the treatment area. Some known handpiece designs contain a single focused laser beam or an array of laser spots that are temporally controlled to produce a desired pattern as the handpiece moves over the skin. A subset of these systems also include a method for imaging the skin passing under the tip to calculate a tip velocity for feedback into a system that adjusts the pulse rate of the laser to accommodate changes in an operator&#39;s hand speed. 
     A common disadvantage of existing handpieces is that their automated control of laser focus, pulse rate and energy relies on the assumption that the operator will hold the handpiece normal to the skin surface. While a trained and conscientious clinician may be capable of approaching this level of precision, it is unreasonable to assume absolute consistency, especially in treatment of contoured regions of a treatment area, such as a face. 
     The consequences of handpiece misalignment depend on the details of the laser treatment. In a system with a 2-D fractional pattern, tilting the handpiece could distort the treatment pattern and shift the focal point of laser spots. The macroscopic result could be inhomogeneity of treatment with possible skin damage in regions of overexposure. A scanning handpiece with velocity feedback depends on normal orientation of the handpiece to properly track movement. Tilting the handpiece by a large angle could interrupt the delivery of treatment by triggering a safety shut-off in the tracking mechanism. This would result in undertreatment of that region of tissue. Even with a small error in angle, the focus of the laser could shift on both horizontal and vertical axes from its calculated target under the epidermis to some unspecified point outside of the treatment region. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the limitations of the prior art by using a mechanical element that allows the tip of the handpiece of a dermatological treatment system to rotate to adjust for deviations in handpiece angle with respect to the surface of the treatment area. The tip of the handpiece includes a planar element with an exit port for laser light. The tip may also include optical elements for redirecting and focusing the laser. Alternatively or additionally, the tip may deliver a 2-D array of laser beams designed for a stamping application of a fractional pattern. In one embodiment, the tip glides over the surface of the skin. In another embodiment, the tip includes wheels or rotating cylinders on which the tip rolls across the skin. 
     In one embodiment, the tip of the handpiece rotates around a single axis. In this arrangement, unequal forces on opposite sides of the pivot axis caused when only one side of the tip is in contact with the treatment surface would move the tip until the forces are equalized by the tip making planar contact with the treatment surface on both sides of the pivot axis. In one implementation of the single axis of rotation, the pivot point lies between two roller elements of the tip. In another embodiment, the tip of the handpiece rotates around two perpendicular axes, so that pressure on the tip from any angle moves the flat surface of the tip into proper orientation for planar contact with the skin. In another implementation, a socket joint is used to allow full angular pivoting of the tip. 
     In various embodiments, an element is included in the handpiece to apply a restoring force on the tip so that the tip rests in its optimal position in the absence of external forces, such as those applied when the tip makes contact with the treatment surface. In one implementation, a plastic segment between the handpiece and tip flexes under pressure to maintain contact between the tip and skin surface, and applies a restoring force on the tip to return the tip to its optimal position when not in contact with the skin surface. In some embodiments, the restoring force is sufficient to provide feedback to the operator to indicate a desired corrective action and/or a desired angle for the operator to adjust a tilt of the handpiece. 
     Other aspects of the invention include methods corresponding to the devices and systems described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention has other advantages and features which will be more readily apparent from the following detailed description of the invention and the appended claims, when taken in conjunction with the accompanying drawings, in which 
         FIG. 1A  illustrates a prior art design of a roller tip for a dermatological handpiece. 
         FIGS. 1B and 1C  illustrate a pivoting tip for a dermatological handpiece at two different angles with respect to the treatment surface, in accordance with an embodiment of the invention. 
         FIG. 2  is a diagram of a full handpiece showing the pivot point of the tip, in accordance with one embodiment. 
         FIG. 3A  illustrates an example shift in focal point of a laser that occurs when a handpiece with a rolling tip is misaligned with the treatment surface. 
         FIG. 3B  illustrates a single axis pivoting tip for improving laser aim, in accordance with one embodiment. 
         FIG. 4  illustrates a tip with rotation on two perpendicular axes and fiber delivery of laser light to the skin, in accordance with one embodiment. 
         FIG. 5  illustrates a configuration for a 2-D beam array delivery with a tip and handpiece joined by a compressible medium, in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1A  illustrates a prior art design of a roller tip  101  for a dermatological handpiece. As shown in  FIG. 1A , the tip  101  of the dermatological handpiece may become misaligned, i.e., tilted, with respect to the surface of skin  10 , and one of the roller elements  11  may lose contact with the skin  10 . In some cases, the misalignment is caused by operator error. In other cases, the particular contours of the treatment surface make consistently maintaining the handpiece casing  3  at the proper angle with respect to skin  10  challenging if not impossible as the tip  101  is rolled over the skin  10 . As a result, the treatment energy  5  is likely to miss the target  110  of the treatment. In the example shown in  FIG. 1A , the tilt of the tip causes the treatment energy  5  to fail to penetrate the skin to the appropriate depth, and the target  110  is under-exposed as a consequence. 
       FIGS. 1B and 1C  illustrate a pivoting roller tip  201  for a dermatological handpiece at two different angles with respect to the treatment surface, in accordance with one embodiment of the invention. In one implementation of the single axis of rotation, the pivot point  7  lies between two roller elements  11  of the tip. Roller elements  11  may be wheels or rotating cylinders, for example. In this arrangement, unequal forces on opposite sides of the pivot axis caused when only one side of the tip  201  or one of the roller elements  11  is in contact with the treatment surface would rotate the tip  201  until the forces are equalized by the tip  201  or the roller elements  11  making contact with the treatment surface on both sides of the pivot mechanism  7 . As shown in  FIG. 1B , the tip  201  of the dermatological handpiece maintains proper alignment and roller elements  11  maintain contact with the surface of skin  10 , despite the handpiece casing  3  being held such that treatment energy  5  is incident on skin at an acute angle α. In  FIG. 1C , the tip  201  maintains proper alignment and roller elements  11  maintain contact with the surface of skin, when the handpiece casing  3  is held such that the treatment energy  5  is incident on the skin at an obtuse angle β as well. In both examples, the pivot mechanism  7  allows the tip  201  to rotate along one axis with respect to the handpiece casing  3 , and the treatment energy  5  hits the target  110 . 
     It is particularly beneficial for the roller elements  11  to maintain contact with the surface of the skin  10  in devices wherein feedback is provided based on the velocity or positional parameters of one or more roller elements  11 . For example, such feedback can be to the user to indicate that the user is moving too fast or too slow or can be to a laser controller for control of the pulse energy, pulse repetition rate, and/or pulse timing. Examples of systems employing such a feedback system are described in additional detail in copending U.S. patent application Ser. No. 11/744,161, entitled “Opto-mechanical apparatus and method for dermatological treatment,” which is herein incorporated by reference. 
       FIGS. 1B and 1C  illustrate a pivoting roller tip  201  for a dermatological handpiece at two different angles with respect to the treatment surface, in accordance with one embodiment of the invention. In one implementation of the single axis  107  of rotation, the pivot point  7  lies between two roller elements  11  of the tip. Roller elements  11  may be wheels or rotating cylinders, for example. In this arrangement, unequal forces on opposite sides of the pivot axis  107  used when only one side of the tip  201  or one of the roller elements  11  is in contact with the treatment surface would rotate the tip  201  until the forces are equalized by the tip  201  or the roller elements  11  making contact with the treatment surface on both sides of the pivot mechanism  7 . As shown in  FIG. 1B , the tip  201  of the dermatological handpiece maintains proper alignment and roller elements  11  maintain contact with the surface of skin  10 , despite the handpiece casing  3  being held such that treatment energy  5  is incident on skin at an acute angle α. In  FIG. 1C , the tip  201  maintains proper alignment and roller elements  11  maintain contact with the surface of skin, when the handpiece casing  3  is held such that the treatment energy  5  is incident on the skin at an obtuse angle β as well. In both examples, the pivot mechanism  7  allows the tip  201  to rotate along one axis  107  with respect to the handpiece casing  3 , and the treatment energy  5  hits the target  110 . The tip  201  of the dermatological handpiece rotates around the single axis  107  so that pressure on the tip  201  moves a flat surface  109  of a planar element  111  of the tip  201  into proper orientation for planar contact with the skin  10 . 
       FIG. 3A  illustrates an example shift in focal point of a laser that occurs when a handpiece with a rolling tip is misaligned with the treatment surface. As shown in  FIG. 3A , a handpiece having a tip  9  rigidly attached to the handpiece casing  3  is tilted with respect to the surface of skin  10 . This results in the focal point of treatment energy  5  missing the treatment target  110 . In contrast,  FIG. 3B  illustrates a single axis pivoting tip for improving laser aim, in accordance with one embodiment. The pivoting action allows the tip  9  to stay in contact with the skin  10  even if the angle of the handpiece with respect to the surface of the treatment area deviates from normal. Thus, the treatment energy  5  is focused at the target  110 . 
     In one implementation, locating the pivot axis  7  close to the treatment area is advantageous in that the optical path length of the beams is preserved such that the beams are approximately the right size as they enter the skin  10 . This prevents problems caused by having optical path lengths change when the handpiece is tilted, such as the adjacent beams overlapping or the beam size altering, which can cause under or over-exposure. In other embodiments, the pivot axis  7  can be located below the skin  10  surface at the beam focal point or can be adjusted to other locations depending on the desired optical effect, such as to compensate for the change in angle and preserve the beam cross-sectional area on the skin surface or at some desired level within the skin, such as the dermal-epidermal junction. 
       FIG. 3A  illustrates an example shift in focal point of a laser that occurs when a handpiece with a rolling tip is misaligned with the treatment surface. The treatment energy  5  passes through a transparent window  8  of tip  9  to reach the skin  10 . The transparent window  8  defines an exit port in the planar element  111  of the rolling tip for the treatment energy  5 . As shown in  FIG. 3A , a handpiece having a tip  9  rigidly attached to the handpiece casing  3  is tilted with respect to the surface of skin  10 . This results in the focal point of treatment energy  5  missing the treatment target  110 . In contrast,  FIG. 3B  illustrates a single axis pivoting tip for improving laser aim, in accordance with one embodiment. The pivoting action allows the tip  9  to stay in contact with the skin  10  even if the angle of the handpiece with respect to the surface of the treatment area deviates from normal. Thus, the treatment energy  5  is focused at the target  110 . Alternative embodiments can employ springs, rubber stretching members, flexible compression members, or other means for generating a restorative force. 
     In some embodiments, the restoring force is sufficient to provide feedback to the operator to indicate a desired corrective action and/or a desired angle for the operator to adjust a tilt of the handpiece. For example, the restoring force can give an operator feedback on how far the operator was tilting the handpiece from normal, such that the operator can correct the misalignment of the handpiece. This can improve the delivery of the treatment beam(s) to the desired treatment location(s). 
       FIG. 5  illustrates a configuration for a 2-D array delivery with a tip and handpiece joined by a compressible medium  16 , in accordance with one embodiment. In this embodiment, the handpiece casing  3  houses an optical fiber  14  that carries laser light to delivery optics  15 B that deliver the treatment energy  5  according to a desired 2-D treatment pattern. In the embodiment depicted in  FIG. 5 , the delivery optics comprises a collimating lens  17  and a lens array  18 . Other embodiments will be evident to those skilled in the art. The treatment energy  5  in the 2-D pattern passes through transparent window  8  to the treatment area. In the embodiment shown in  FIG. 5 , a compressible medium  16 , such as a compressible plastic, is placed between the handpiece and the tip. The compressible medium asserts a restorative force on the tip so that the tip rests in its optimal position in the absence of external forces, such as the forces applied when the tip makes contact with the treatment surface. However, the compressible medium  16  between the handpiece and tip flexes under pressure to maintain contact between the tip and skin surface as the tip glides along the contours of the skin surface. 1-D and 3-D treatment patterns can also be used, as desired. 
     Although the detailed description contains many specifics, these should not be construed as limiting the scope of the invention but merely as illustrating different examples and aspects of the invention. It should be appreciated that the scope of the invention includes other embodiments not discussed in detail above. The aspects of this invention as described above can be further combined to create other embodiments that are within the scope of this invention. Various other modifications, changes and variations which will be apparent to those skilled in the art may be made in the arrangement, operation and details of the method and apparatus of the present invention disclosed herein without departing from the spirit and scope of the invention.