Surgery – Instruments – Electrical application
Reexamination Certificate
2001-02-22
2004-04-20
Bennett, Henry (Department: 3743)
Surgery
Instruments
Electrical application
C606S034000, C606S045000, C606S049000, C606S050000, C606S009000, C607S101000
Reexamination Certificate
active
06723091
ABSTRACT:
This invention relates to tissue resurfacing, for example, skin resurfacing, or the resurfacing or removal of tissue located within, e.g., the alimentary canal, respiratory tracts, blood vessels, uterus or urethra.
Human skin has two principal layers: the epidermis, which is the outer layer and typically has a thickness of around 120&mgr; in the region of the face, and the dermis which is typically 20-30 times thicker than the epidermis, and contain hair follicles, sebaceous glands, nerve endings and fine blood capillaries. By volume the dermis is made up predominantly of the protein collagen.
A common aim of many cosmetic surgical procedures is to improve the appearance of a patient's skin. For example, a desirable clinical effect in the field of cosmetic surgery is to provide an improvement in the texture of ageing skin and to give it a more youthful appearance. These effects can be achieved by the removal of a part or all of the epidermis, and on occasions part of the dermis, causing the growth of a new epidermis having the desired properties. Additionally skin frequently contains scar tissue, the appearance of which is considered by some people to be detrimental to their attractiveness. The skin structure which gives rise to scar tissue is typically formed in the dermis. By removing the epidermis in a selected region and resculpting the scar tissue in the dermis it is possible to improve the appearance of certain types of scars, such as for example scars left by acne. The process of removing epidermal and possibly dermal tissue is known as skin resurfacing or dermabrasion.
One known technique for achieving skin resurfacing includes the mechanical removal of tissue by means of an abrasive wheel, for example. Another technique is known as a chemical peel, and involves the application of a corrosive chemical to the surface of the epidermis, to remove epidermal, and possibly dermal skin cells. Yet a further technique is laser resurfacing of the skin. Laser are used to deliver a controlled amount of energy to the epidermis. This energy is absorbed by the epidermis causing necrosis of epidermal cells. Necrosis can occur either as a result of the energy absorption causing the temperature of the water in the cells to increase to a level at which the cells die, or alternatively, depending upon the frequency of the laser light employed, the energy may be absorbed by molecules within the cells of the epidermis in a manner which results in their dissociation. This molecular dissociation kills the cells, and as a side effect also gives rise to an increase in temperature of the skin.
Typically during laser resurfacing a laser beam is directed at a given treatment area of skin for a short period of time (typically less than one millisecond). This can be achieved either by pulsing the laser or by moving the laser continuously and sufficiently quickly that the beam is only incident upon a given area of skin for a predetermined period of time. A number of passes be may made over the skin surface, and dead skin debris is usually wiped from the skin between passes. Lasers currently employed for dermabrasion include a CO
2
laser, and an Erbium-YAG laser. The mechanisms by which energy is absorbed by the tissue causing it to die, and the resultant clinical effects obtained, such as the depth of tissue necrosis and the magnitude of the thermal margin (i.e. the region surrounding the treated area that undergoes tissue modification as a result of absorbing heat) vary from one laser type to another. Essentially, however, the varying treatments provided by these lasers may be considered as a single type of treatment method in which a laser is used to impart energy to kill some or part of the epidermis (and depending upon the objective of the treatment, possibly part of the dermis), with the objective of creating growth of a new epidermis having an improved appearance, and also possibly the stimulation of new collagen growth in the dermis.
Other prior art references of background interest to the present invention include U.S. Pat. No. 3,699,967 (Anderson), U.S. Pat. No. 3,903,891 (Brayshaw), U.S. Pat. No. 4,040,426 (Morrison), U.S. Pat. No. 5,669,904, WO95/0759, WO95/26686 and WO98/35618.
The present invention provides an alternative to known skin resurfacing techniques, apparatus and methods of operating such apparatus.
According to a first aspect of the present invention, a tissue resurfacing system comprises: a surgical instrument having a gas conduit terminating in a plasma exit nozzle, and an electrode associated with the conduit, and a radio frequency power generator coupled to the instrument electrode and arranged to deliver radio frequency power to the electrode in single or series of treatment pulses for creating a plasma from gas fed through the conduit, the pulses having durations in the range of from 2 ms to 100 ms.
The application of an electric field to the gas in order to create the plasma may take place at any suitable frequency, including the application of standard electrosurgical frequencies in the region of 500 kHz or the use of microwave frequencies in the region of 2450 MHz, the latter having the advantage that voltages suitable for obtaining the plasma are more easily obtained in a complete structure. The plasma may be initiated or “struck” at one frequency, whereupon optimum power transfer into the plasma may then take place at a different frequency.
In one embodiment a radio frequency oscillating voltage is applied to the electrode in order to create a correspondingly oscillating electric field, and the power transferred to the plasma is controlled by monitoring the power reflected from the electrode (this providing an indication of the fraction of the power output from the power output device which has been transferred into the plasma), and adjusting the frequency of the oscillating voltage from the generator accordingly. As the frequency of the oscillating output from the generator approaches the resonant frequency of the electrode (which is affected by the presence of the plasma), the power transferred to the plasma increases, and vice versa.
Preferably, in this embodiment, a dipole electric field is applied to the gas between a pair of electrodes on the instrument which are connected to opposing output terminals of the power output device.
In an alternative aspect of the invention a DC electric field is applied, and power is delivered into the plasma from the DC field. The gas employed is preferably non-toxic, and more preferably readily biocompatible to enable its natal secretion or expulsion from the body of the patient. Carbon dioxide is one preferred gas, since the human body automatically removes carbon dioxide from the bloodstream during respiration. Additionally, a plasma created from carbon dioxide is hotter (albeit more difficult to create) than a plasma from, for example argon, and carbon dioxide is readily available in most operating theatres. Nitrogen or even air may also be used.
According to another aspect of the invention, a gas plasma tissue resurfacing instrument comprises: an elongate gas conduit extending from a gas inlet to an outlet nozzle and having a heat resistant dielectric wall; a first electrode located inside the conduit; a second electrode located on or adjacent an outer surface of the dielectric wall in registry with the first electrode; and an electrically conductive electric field focussing element located inside the conduit and between the first and second electrodes.
Some preferred features are set out in the accompanying dependent claims. The system described hereinafter has the benefit of being able to produce rapid treatment at the tissue surface while minimising unwanted effects, e.g. thermal effects, at a greater than required depth.
A further aspect of the present invention provides a method of skin resurfacing at least the epidermis of a patient using a surgical system comprising an instrument having an electrode connected to a power output device, the method comprising the steps of: operating the power output device to crea
Amoah Francis
Goble Colin C. O.
Hancock Christopher P
Penny Keith
Bennett Henry
Dahbour Fadi H.
Gyrus Medical Limited
Oliff & Berridg,e PLC
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