Dynamic cooling of human skin using a nontoxic cryogen with no ozone depletion and minimal global warming potential

Abstract

A method and apparatus for performing a laser treatment of a patient includes applying a positive pressure impulse on a predetermined target site on the patient with sufficient positive pressure arising from the momentum flux of sprayed material incident on the target site to momentarily lessen pain sensation during irradiation during or proximate in time to irradiation of the target site. The predetermined target site is cooled by applying a predetermined amount of coolant or cryogen onto the target site. The target site is radiated with energy to produce heat in tissue at the target site while leaving a superficial part of the target site substantially undamaged due to dynamic cooling of the superficial part of the target site by the coolant. Mediation of the pain sensation arising from the radiation is at least partially masked or lessened by the positive pressure impulse and / or by the temperature of the coolant.

Description

[0001]The present application is a continuation-in-part application of copending U.S. patent application Ser. No. 11 / 845,503, filed on Aug. 27, 2007, which in turn is related to U.S. Provisional Patent Application Ser. No. 60 / 840,867, filed on Aug. 28, 2006, both of which are incorporated herein by reference and to which priority is claimed pursuant to 35 USC 120.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The invention relates to the field of therapeutic treatment of skin or tissue by exposure to light or other electromagnetic radiation in combination with cryogen cooling of the irradiated tissue.[0004]2. Description of the Prior Art[0005]An important issue in laser treatment of cutaneous lesions is to protect the epidermis from thermal damage. This heating, which is primarily caused by light absorption in the melanosomes, can easily bring the temperature of the basal layer above the threshold damage value of 65-70° C. Precooling of the epidermal basal layer fro...

AI Technical Summary

Benefits of technology

[0028]In the preferred embodiment the apparatus is for performing laser treatment of a biological tissue or skin and comprises a laser directed to deliver energy to a selected location of the biological tissue, a source of liquid carbon dioxide, a controller; and a spray applicator having at least one nozzle communicated with the source of liquid carbon dioxide. The spray application and laser are coupled to and controlled by the controller to spray a predetermined amount of liquid carbon dioxide through the at least one nozzle to expand or nearly adiabatically expand the liquid carbon dioxide to create a controlled amount of carbon dioxide snow which impinges onto the selected location of the biological tissue in coordination with laser irradiation onto the selected location. The carbon dioxide snow is substantially all deposited on the biological tissue in a solid state. The deposition of the carbon dioxide snow on the biological tissue substantially all in the solid state avoids pooling of any substantial amount of liquid state carbon dioxide and consequent uneven cooling of the biological tissue.

[0029]In another embodiment the apparatus is for performing laser treatment of a biological tissue or skin and comprises a laser directed to deliver energy to a selected location of the biological tissue; a source of liquid carbon dioxide under high pressure at room or elevated temperature; a controller to accurately control a predetermined time period of liquid carbon dioxide release from the source; and a spray applicator having a high pressure valve and at least one nozzle communicated with the source of liquid carbon dioxide, coupled to and controlled by the controller to spray a predetermined amount of liquid carbon dioxide through the at least one nozzle to expand or nearly adiabatically expand the liquid carbon dioxide to create an accurately controlled amount of carbon dioxide snow which impinges onto the selected location of the biological tissue, so that precise control of the duration of the time-controlled pulses of carbon dioxide are achieved by use of the high pressure valve.

Problems solved by technology

An important issue in laser treatment of cutaneous lesions is to protect the epidermis from thermal damage.

Potential non-flammable candidates for cryogen spray cooling could be carbon dioxide (CO2, R-744) or nitrous oxide (N2O, R-744a) but, unfortunately, these compounds do not form boiling liquids at atmospheric pressure.

Liquid CO2 results in dry-ice formation immediately after leaving the outlet nozzle.

However, the evaporation loss is high, and the cryogenic equipment for delivering liquid cryogen spurts in the 100 ms range might be technically very cumbersome.

Thus, the combined use of flammable cryogen and high laser energy might induce burns to the skin.

Port wine stain is a congenital lesion with a frequency of one in two hundred births, often resulting in a high psychological burden for the child.

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