Patent ID: 6248103
Filing Date: 2001-06-19
Classification: A61B,A61N

Abstract:
A method for performing laser treatment of biological tissues comprising:cooling a selected portion of said biological tissue for a predetermined first time period 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 established by providing a spurt of a predetermined amount of cryogenic liquid in direct contact with said biological tissue for said first time period at a site which is later irradiated for a predetermined second time period;immediately after said first time period irradiating a superficial and deeper part of said selected portion of said biological tissue for said second time period approximately equal to or in excess of one millisecond to thermally treat said deeper part of said biological tissue while leaving said superficial part of said biological tissue substantially undamaged, said cryogenic liquid having a latent heat of vaporization, said superficial part of said biological tissue being cooled for said second time period by a change of state of said cryogenic liquid to vapor, heat being quickly dissipated from said superficial part of said biological tissue by means of supplying said latent heat of vaporization to said cryogenic liquid, said heat being dissipated in an amount as determined by said predetermined amount of cryogenic liquid applied to said superficial part of said biological tissue, the amount of dissipation of said heat from said superficial part of said biological tissue being specified by said predetermined amount of said cryogenic liquid applied to said superficial part of said biological tissue and by said latent heat of vaporization of said cryogenic liquid; andcooling said selected portion of said biological tissue for a predetermined third time period overlapping with said second time period by providing one or more additional spurts of predetermined corresponding amounts of cryogenic liquid in direct contact with said biological tissue at said site which is being irradiated to maintain said selected portion of said biological tissue at or below an average selected temperature,whereby said deeper part of said selected portion of said biological tissue may be laser treated without damage to said superficial part.