Method and apparatus for cryogenic treatment of skin tissue
Cosmetic method and apparatus are provided that can provide cooling and/or freezing of skin tissue proximal to the skin surface to generate an appearance of lightening or reduced pigmentation in the skin. The skin can be cooled to a temperature of less than about −5 degrees Celsius for a duration of about one minute or less, using a plurality of cooled contact surfaces, each having a width between about 2 mm and about 20 mm. A cooling arrangement can be provided to provide controlled heat removal from the skin tissue being treated. A sensor can optionally be provided to detect freezing of tissue proximal to the cooled surfaces.
1. A non-invasive cosmetic method for freezing a portion of a skin tissue to lighten a pigmentation appearance of the skin tissue, the method comprising:
providing a non-invasive handheld apparatus having a handle and a plurality of protrusions;
positioning the handheld apparatus on a portion of a skin tissue with the handle; and
freezing a plurality of separated surface regions of skin tissue to produce a lightened pigmentation appearance in the skin tissue, wherein a width of at least two adjacent frozen regions of the skin tissue is greater than about 2 mm and less than about 20 mm,
wherein the freezing step comprises contacting the surface of the skin tissue with the plurality of protrusions, wherein a width of a distal end of each protrusion is between about 2 mm and about 20 mm and wherein a temperature of the protrusions freezes a basal layer of the skin tissue to produce a lightened pigmentation appearance in the skin tissue; and
wherein the plurality of protrusions are arranged in a configuration where the protrusions have a higher density at a central region of the configuration than at a peripheral region of the configuration so as to provide a feathered arrangement of the protrusions to facilitate greater skin surface contact at the central region than the peripheral region for blending treatment or avoiding excessive cooling in areas of overlap between adjacent placements.
2. The method of claim 1 , wherein a temperature of the protrusions is provided at between about −7 degrees and −10 degrees Celsius.
3. The method of claim 1 , wherein a temperature of the protrusions is provided at between about −5 degrees and −20 degrees Celsius.
4. The method of claim 1 , wherein the surface of the skin tissue is contacted by the protrusions for a duration that is less than about one minute.
5. The method of claim 1 , further comprising detecting a freezing of the skin tissue proximal to at least one of the protrusions in contact with the skin surface.
6. The method of claim 1 , further comprising detecting freezing of the skin tissue to avoid local supercooling of the skin tissue.
7. The method of claim 6 , wherein freeze detection is carried out by an optical sensor.
8. The method of claim 1 , further comprising rewarming or thawing the frozen tissue after a treatment time.
9. The method of claim 1 , further comprising successively placing the apparatus on the skin surface, wherein there is at least one overlap region between the adjacent placements, and wherein the feathered distribution avoids excessive cooling in the overlap region.
10. The method of claim 1 , wherein certain ones of the protrusions are closer together at the central region of the configuration, and wherein other ones of the protrusions are further apart at the peripheral region of the configuration.
11. The method of claim 1 , further comprising modifying a set-point temperature of a cooling arrangement in thermal communication with the plurality of protrusions based on a received signal from a sensor of the apparatus.