Apparatus and method for dynamic cooling of biological tissues for thermal mediated surgery

A method of laser treating port wine stain birthmarks in human skin having an epidermis containing melanin and a dermis containing said port wine stains comprising the steps of:

• dynamically cooling said epidermis by directly applying a controlled amount of a cryogenic liquid to said epidermis such that onset of a predetermined nonequilibrium temperature profile within said epidermis is achieved within a first time period substantially shorter than the thermal diffusion time between said port wine stain in said dermis and said overlying epidermis;
• and
• immediately thereafter irradiating said port wine stain in said dermis through said epidermis for a second predetermined time period sufficient in length to selectively destroy cutaneous blood vessels within said port wine stain, but for a time duration less than said thermal diffusion time between said epidermis and dermis,
• simultaneously with said step of irradiating, rapidly cooling said epidermis by vaporizing said cryogenic liquid, said amount of said cryogenic liquid applied to said epidermis being controlled by offsetting a rate of cooling of said epidermis by vaporization of said cryogenic liquid against a rate of heating of said epidermis by said step of irradiating;
• whereby said port wine stain is destroyed without substantial biological damage to said epidermis.

A method for performing laser treatment of biological tissues comprising the steps of:

• cooling a first part of said biological tissue for a predetermined first time period by direct contact of a liquid cryogen to said first part to establish a predetermined nonequilibrium dynamic temperature gradient through said tissue so that substantially only said selected portion of said biological tissue is cooled by a predetermined minimum temperature drop, said predetermined dynamic temperature gradient being defined in said biological tissue for said first time period at a site which is later irradiated for a predetermined second time period;
• and
• immediately after said first time period, irradiating said first part and a second part of said biological tissue for said second time period to thermally treat said second part of said biological tissue while leaving said first part of said biological tissue substantially undamaged;
• and
• simultaneously with said step of irradiating, cooling said first part of said biological tissue for said second time period by quickly dissipating heat from said first part of said biological tissue through a thin layer of said liquid cryogen on said first part of said biological tissue at a rate high enough to prevent thermal-induced biological damage to said first part of said biological tissue;
• and
• quickly terminating said step of cooling to prevent any substantial removal of heat from said second part of said biological tissue which would interfere with a thermal biological effect to said second part of said biological tissue,
• whereby said second part of said selected portion of said biological tissue may be laser treated without damage to said first part.

A method for performing laser treatment of biological tissues comprising the steps of:

• applying a selected amount of cooling cryogenic liquid in direct contact with a selected proximate portion of said biological tissue for a selected first time period having a beginning and an end;
• irradiating said proximate portion and targeted chromophores in a selected adjacent and distal portion of said biological tissue by a laser beam beginning from said end of said selected first time period and continuing through a selected second time period having a beginning and an end, said end of said selected first time period being controllable within a few milliseconds, and wherein said first time period is less than that required to substantially cool said targeted chromophores;
• and
• ending irradiation of said proximate and distal portion of said biological tissue at said end of said selected second time period, said end of said selected second time period being controllable within a few milliseconds, and wherein said second time period is less than that at which damage begins to occur in said proximate portion,
• whereby said distal portion of said biological tissue is thermally surgically mediated without damage to said proximate portion.