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Method and apparatus for monitoring and controlling laser-induced tissue treatment

Method and apparatus for monitoring and controlling laser-induced tissue treatment description/claims

This application is a continuation of U.S. Pat. No. 7,282,060, “Method and Apparatus for Monitoring and Controlling Laser-Induced Tissue Treatment,” filed Dec. 21, 2004, which is a continuation-in-part of U.S. patent application Ser. No. 10/745,761, “Method and Apparatus for Monitoring and Controlling Laser-Induced Tissue Treatment,” filed Dec. 23, 2003 and which is also a continuation-in-part of U.S. Pat. No. 7,184,184, “High Speed, High Efficiency Optical Pattern Generator Using Rotating Optical Elements,” filed Dec. 31, 2003, and which also claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 60/605,092, “Method and Apparatus for Monitoring and Controlling Laser-Induced Tissue Treatment,” filed Aug. 26, 2004. All of the foregoing are incorporated herein by reference.

The present invention relates to a method and apparatus for dermatological tissue treatment, and more particularly, to a method and apparatus comprising a combination of a light source, a handpiece, and a means for measurement of the handpiece motion utilized for controlling the tissue treatment.

Lasers and other intense light sources are used for various types of tissue treatment, including dermatological tissue treatment. During dermatological tissue treatment utilizing light, a light beam irradiates the skin surface of a patient. Generally, lasers that are used for such treatment operate at a wavelength that is absorbed by one of the natural chromophores in the skin, such as water. In the case of water as the primary chromophore, cellular and interstitial water absorbs light energy and transforms the light energy into thermal energy. The transport of thermal energy in tissues during treatment is a complex process involving conduction, convection, radiation, metabolism, evaporation and phase change that vary with the operational parameters of the light beam. It is essential in such procedures not to damage tissue underlying or surrounding the target tissue area. If the light beam optical operational parameters, such as wavelength, power, the intensity of the light, pulse duration, rate of emission, etc. are properly selected, cellular and interstitial water in the patient's skin is heated causing temperature increases that produce a desired dermatological effect. Conversely, improper selection of the optical operational parameters can result in undertreatment or overtreatment of the tissue. Therefore, it is desirable to accurately control optical operational parameters used in the treatment so that the light is delivered to the tissue with the proper fluence and in a uniform, controllable manner. A variety of devices have been proposed that intelligently control laser beam power, intensity, duration, etc. However, as will be discussed in greater detail below, application of these devices have significant disadvantages.

Known devices for dermatological tissue treatment include a hand-held delivery apparatus, sometimes referred to as a handpiece. A handpiece is the preferred means by which physicians apply treatment to tissue. During treatment, the handpiece emitting light is moved by a physician's hand along the tissue to be treated. Treatment level from such a device is typically set in advance by manually selecting the light beam operational parameters. The operational parameters, which for example include power level, energy, pulsation rate, temperature, light intensity, and current, determine the degree of treatment of the entire treatment process.

One disadvantage of some of the existing handpiece apparatuses is that they require strict precision in positioning of the handpiece and application of controlled movement in order to stay within limits of safe, uniform and efficacious treatment. Theoretically, strict precision can be achieved with a high degree of skill, attention and dexterity from the treating physician. In a real procedure, however, manual application and control of the handpiece can easily result in non-uniformity of treatment due to imprecise or involuntary movements of the human hand and/or uneven tissue surfaces. This often results in either some areas of the targeted tissue being under-treated, or causes some areas to be over-treated.

A typical approach of known handpieces is to produce a macroscopic, pulsed treatment beam that is manually moved from one area of the skin to another in a patchwork like manner in order to treat a larger region of skin tissue. Such an approach has the disadvantage of producing artifacts and sharp boundaries associated with the inaccurate positioning of the individual treatments with respect to the treated skin surface.

Another disadvantage of known handpieces is that, as discussed above, the laser operational parameters defining the selected level of treatment are typically pre-set once for the entire course of treatment. The individual tissue properties of each patient are factored-in based on a preliminary tissue assessment prior to the treatment and the treatment can proceed using the predetermined operational parameters.

For example, some existing handpiece apparatuses provide feedback indicating to the physician the rate of the handpiece movement which allows the physician to adjust the treatment speed. But this handpiece apparatus requires the physician to treat at a pre-selected rate of motion. The disadvantage of this apparatus is that it restricts the physician to a single treatment speed. In large flat areas, such as the cheek, it is desirable to treat at a high speed. In highly contoured areas, such as the lip, it is desirable to treat at a lower speed. Restricting the physician to a pre-selected rate of motion limits the flexibility of the physician when treating regions, such as the face, that include both large flat areas and highly contoured areas that are in close proximity. Additionally, if the speed of the handpiece changes during the treatment procedure, the apparatus does not provide for automatic adjustment of its operational parameters to compensate for the changed rate of movement, leading to uneven treatment.

The application of robotic means used in the field of dermatological or cosmetic surgery could overcome the limitation of human imprecision. However, one disadvantage of typical conventional robotic apparatuses is that they lack the necessary direction and judgment in treatment that a physician provides. Although robotics is precise, it is not typically intelligent enough to make complex choices or react to unforeseen circumstances during treatment. Additionally, robots deprive a physician of discretion in an aesthetic sense.

Another disadvantage of the typical conventional robotic apparatus is that the full treatment may require complete immobilization of the patient. Alternatively, a sophisticated image stabilization system must be employed to compensate for patient's movement. It is still another disadvantage of such robotic apparatuses that they are bulky and cannot be easily moved into treatment positions in relation to the areas allowing little room for movement. Rather, a tissue surface to be treated has to be brought into a specific position in relation to the apparatus before treatment can take place.

The present invention provides a method and apparatus which significantly reduce the problems associated with the existing laser-induced handpieces apparatuses and robotics.

The present invention provides improved methods and apparatus for controlling light-induced tissue treatment that overcome many of the shortcomings of the prior art. The ways in which the present invention addresses the drawbacks of the now-known techniques for dermatological tissue treatment will be described in greater detail herein. In accordance with various aspects of the present invention, the invention provides for improved, real-time control of the light beam operational parameters which enables greater safety, efficiency, uniformity and continuity of the treatment process.

It is an object of the present invention to provide a more precise and efficient technique for uninterrupted hand-delivered tissue treatment by a freely movable handpiece augmented by a feedback controlling means for improved overall quality of treatment.

It is another object of the present invention to monitor and automatically control in substantially real-time or quasi-real time operational parameters of the treatment beam(s) in response to detected variations in the position and/or movement of the handpiece, whereby optimum treatment conditions can be achieved throughout the treatment irrespective of these variations.

It is a further object of the present invention to provide a method and apparatus for hand-delivered tissue treatment that in real-time adjusts output optics of the handpiece in response to variations in the handpiece positional parameters to simultaneously deliver the light beam in a controlled discontinuous pattern to a plurality of discrete treatment zones with a minimum collateral damage to the intentionally untreated tissue and without blurring or distorting the intended shape and/or dimension of the discrete treatment zones.

It is still a further object of the present invention to provide a method and apparatus for hand-delivered tissue treatment that is adapted to provide uniform light beam fluence and patterns irrespective of the individual target tissue properties and the handpiece velocity.

These and other objects and features will be apparent from the following description of the present invention contained herein.

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