System and method for microablation of tissue

Abstract

The present invention generally relates to the field of laser treatment of tissue, and particularly, to a system and method for creating microablated channels in skin. The present invention is more particularly directed to treating subsurface tissue through the created channels.

1 . A method for treating tissue using a laser system with pulsed light output, comprising (a) indicating by a user at least two of (a1) a desired total light output energy, (a2) a desired average light output power, or (a3) a desired duration of laser application, (b) controlling the laser by the system in order to achieve the selected conditions (a1), (a2), or (a3) specified by the user, (c) directing the light output of the laser to the tissue to be treated over the desired duration. 
     
     
         2 . The method of  claim 1 , wherein the laser system has a control for power used to produce a population inversion, wherein the control varies between on and off states, a population inversion being produced when the control is varied from an off state to an on state, and wherein the system varies this control between on and off states at least four times in order to achieve the selected conditions (a1), (a2), or (a3). 
     
     
         3 . The method of  claim 1 , wherein the laser system has at least two attenuating elements and the system places at least one of these at least two attenuating elements in the path of the laser's output in order to achieve the desired energy or average power or duration. 
     
     
         4 . The method of  claim 1 , wherein the light output of the laser is ablative during a portion of the time that it is directed to the tissue and non-ablative during another portion of the time that it is directed to the tissue. 
     
     
         5 . The method of  claim 1 , wherein the light output of the laser is directed to the tissue through a mirror, an optical fiber, a prism, or another optical element. 
     
     
         6 . The method of  claim 1 , wherein as a result of the light output power being directed to tissue, a channel is ablated in the tissue having a predetermined width and predetermined height, and a thermal affected zone of predetermined volume and shape is created proximate said channel. 
     
     
         7 . The method of  claim 6 , wherein the tissue has a surface through which the light output power passes and the thermal affected zone has a cross section in a plane parallel to that surface which increases in diameter with the plane's distance from that surface, so that the diameter of the cross section increases with distance from that surface for a range of distances to the surface. 
     
     
         8 . The method of  claim 6 , further comprising administering a treatment through the channel. 
     
     
         9 . The method of  claim 1 , wherein the output light power raises the temperature of at least a portion of the tissue into which it is directed above 100° C. 
     
     
         10 . The method of  claim 2 , wherein the system measures the laser's light output power. 
     
     
         11 . The method of  claim 10 , wherein the measured light output power is used in a feedback control system in order to decide when to change the control from an on state to an off state or vice versa. 
     
     
         12 . The method of  claim 1 , wherein the desired average light output power is no greater than about 10% of the maximum instantaneous light output power which the laser is capable of producing. 
     
     
         13 . The method of  claim 1 , wherein the light output power deviates by no more than 10% from the desired average light output power during at least about 90% of the time that the laser is producing light output in response to the user's setting. 
     
     
         14 . The method of  claim 3 , wherein the system selects from a set of discrete attenuation values the attenuation closest to the desired level. 
     
     
         15 . A system for treating tissue with light, comprising: a laser with pulsed light output and a digital controller for the laser, wherein the digital controller implements a user interface which permits a user to select at least two of (a) a total energy to be applied to the tissue, (b) a duration of the application of light to the tissue, and (c) a desired average power level to be applied to the tissue, and wherein the digital controller controls the laser's light output to achieve the conditions (a), (b), or (c) specified by the user. 
     
     
         16 . The system of  claim 15 , wherein the light with which the tissue is treated has a wavelength of at least about 9 μm. 
     
     
         17 . The system of  claim 15 , wherein the laser is capable of producing a pulsed light output with at least about 200 W peak light power. 
     
     
         18 . A system for treating tissue with light, comprising: a laser with pulsed light output, an optical system for directing the light output of the laser to the tissue, and a digital controller for the laser, wherein the laser comprises a pumping mechanism and a control for that mechanism which can be varied between an on state and an off state, wherein varying the control from the off state to the on state produces a population inversion, wherein the digital controller is programmed to vary the control from the off state to the on state and back to the off state a plurality of times, and wherein the light output power of the laser does not fall to zero between the first transition to the off state and the last transition to the on state. 
     
     
         19 . The system of  claim 18 , wherein the digital controller is programmed to receive from a user at least one numerical value and to compute from the at least one numerical value a desired light output power, and wherein the average light output power of the laser between the first transition to the off state and the last transition to the on state lies within about 10% of the desired light output power.