Selective laser induced optical breakdown in biological medium

Abstract

Apparatuses and methods for selectively providing laser induced optical breakdown (LIOB) of absorptive targets in biological media. For example, LIOB may be used as part of tissue therapy, such as cosmetic therapy associated with tattoo removal. In some implementation, a system for selectively providing LIOB includes a field generator configured to generate a field and to apply the field through a portion of a biological medium. The system also includes a light source configured to deliver laser light to the portion of the biological medium during application of the field. Application of the field to the biological medium induces movement of free electrons within the portion of the biological medium which may reduce or slow the formation of vacuoles in the biological medium responsive to the laser light.

1 .- 61 . (canceled) 
     
     
         62 . An apparatus for providing tissue therapy, the apparatus comprising:
 a field generator configured to generate a field and to apply the field through a portion of a biological medium;   a direct current (DC) power supply configured to provide DC to the field generator; and   a light source configured to deliver laser light to the portion of the biological medium during application of the field.   
     
     
         63 . The apparatus of  claim 62 , wherein the field comprises an essentially static field, and wherein the field generator is configured to apply essentially static field to the biological medium to induce movement of free electrons within the portion of the biological medium, and delivery of the laser light to the portion of the biological medium provides optical breakdown of tissue pigment particles. 
     
     
         64 . The apparatus of  claim 62 , wherein the field generator comprises a plurality of electrodes configured to provide the field across the plurality of electrodes, and wherein the field comprises an electrical field. 
     
     
         65 . The apparatus of  claim 62 , wherein the field generator comprises a magnetic coil, and wherein the field comprises a magnetic field. 
     
     
         66 . The apparatus of  claim 62 , wherein the light source comprises a pulsed laser configured to deliver the laser light with a pulse rate of at least 1 Hz and a fluence of 0.5 J/cm 2  to 20 J/cm 2 . 
     
     
         67 . The apparatus of  claim 62 , further comprising:
 a head device configured to contact a surface of the biological medium; and wherein:   the head device includes the field generator; and   the head device is physically coupled to the light source.   
     
     
         68 . The apparatus of  claim 67 , wherein the head device comprises a vacuum head configured to be connected to a vacuum source and to apply suction to the portion of the biological medium, the vacuum head configured to permit light to reach the portion of the biological medium during application of the suction. 
     
     
         69 . The apparatus of  claim 62 , further comprising:
 an electret configured to provide a static electrical field;   wherein the electret is further configured to be positioned relative to the biological medium such that the static electrical field induces an electric field in the biological medium;   wherein the induced electric field affects free electrons in the portion of the biological medium; and   wherein the electret is transparent.   
     
     
         70 . The apparatus of  claim 69 , further comprising:
 a therapeutic laser system configured to deliver a laser beam to the portion of the biological medium;   wherein the electret is configured to permit transmission of the laser beam through the electret; and   wherein the therapeutic laser system is further configured to deliver the laser beam to the portion of the biological medium by transmitting the laser beam through the electret.   
     
     
         71 . The apparatus of  claim 62 , wherein the field generator is configured to apply the field through the portion of the biological medium to induce movement of free electrons within the portion of the biological medium. 
     
     
         72 . The apparatus of  claim 62 , wherein the light source is configured to deliver the laser light to the portion of the biological medium along a laser light path, and wherein the apparatus is configured such that application of the field prior to and/or during delivery of the laser light moves free electrons within the portion of the biological medium away from the laser light path. 
     
     
         73 . The apparatus of  claim 62 , wherein the biological medium comprises skin or tissue. 
     
     
         74 . A method comprising:
 actuating, based on direct current (DC) power, the field generator of  claim 62  to apply a field through a portion of the biological medium; and   delivering laser light from the light source to the portion of the biological medium.   
     
     
         75 . The method of  claim 74 , further comprising:
 prior to actuating the field generator, positioning the field generator adjacent to the biological medium at a first location; and   prior to delivering the laser light, positioning the light source with respect to the portion of the biological medium to deliver the laser light to the portion.   
     
     
         76 . The method of  claim 74 , further comprising:
 placing a vacuum head in contact with a surface of the biological medium; and   applying a negative pressure to the vacuum head to stabilize at least the portion of the biological medium, wherein the at least the portion of the biological medium is stabilized during delivery of the laser light to the portion.   
     
     
         77 . The method of  claim 74 , further comprising, after delivering the laser light:
 positioning the field generator adjacent to the biological medium at a second location;   positioning the light source with respect to another portion of the biological medium;   actuating the field generator to generate another field;   applying the other field through the other portion of the biological medium; and   delivering additional laser light from the light source to the other portion of the biological medium during application of the other field.   
     
     
         78 . The method of  claim 74 , further comprising:
 placing a vacuum head containing a plurality of electrodes in contact with a surface of the biological medium, wherein the plurality of electrodes are spaced apart from each other, wherein a first electrode of the plurality of electrodes comprises an electrically conductive surface contacting the biological medium, and wherein a second electrode of the plurality of electrodes is configured to not conduct current to the biological medium;   applying a negative pressure to the vacuum head to stabilize the biological medium;   applying a direct current (DC) electrical potential across the plurality of electrodes to create the field in the biological medium; and   delivering laser light to the biological medium at a point between the plurality of electrodes.   
     
     
         79 . The method of  claim 74 , further comprising:
 placing a plurality of electrodes relative to a surface of the biological medium such that the electrodes are spaced apart from each other, wherein an electrically conductive surface of a first electrode of the plurality of electrodes contacts the biological medium, and wherein a second electrode of the plurality of electrodes is configured to not conduct current to the biological medium;   applying a direct current (DC) electrical potential across the plurality of electrodes to create the field in the biological medium; and   delivering laser light to the biological medium at a point between the plurality of electrodes.   
     
     
         80 . The method of  claim 74 , wherein the field generator is configured to apply the field through the portion of the biological medium to induce movement of free electrons within the portion of the biological medium. 
     
     
         81 . The method of  claim 74 , wherein the light source delivers laser light to the portion of the biological medium along a laser light path; and wherein application of the field prior to and/or during delivery of the laser light moves free electrons within the portion of the biological medium away from the laser light path. 
     
     
         82 . The method of  claim 74 , wherein the biological medium comprises skin or tissue.