Apparatus and method for reducing subcutaneous fat deposits by electroporation

[0002] The present application claims priority from and is a continuation-in-part of U.S. patent application Ser. No. 09/931,672, filed Aug. 17, 2001, entitled Apparatus and Method for Reducing Subcutaneous Fat Deposits, Virtual Face Lift and Body Sculpturing by Electroporation, the specification and drawings of which are incorporated herein in their entirety by reference. The present application also claims priority from U.S. Provisional Patent Application Serial No. 60/358,443, filed Feb. 22, 2002, and entitled Apparatus and Method for Reducing Subcutaneous Fat Deposits by Electroporation, the specification and drawings of which are incorporated herein in their entirety by reference.

[0003] The present invention relates generally to electroporation in-vivo and specifically to apparatus and method for reducing subcutaneous fat deposits and/or for performing virtual face lifts and/or body sculpturing.

[0004] “Cosmetic surgery” is a phrase used to describe broadly surgical changes made to a human body with the usual, though not always, justification of enhancing appearance. This area of medical practice constitutes an ever-growing industry around the world. Obviously, where such a procedure fails to deliver an enhanced appearance, the procedure fails to meet the desired goal. One of the reasons that the majority of current procedures fail to deliver upon their promise is that, for the most part, current procedures are invasive, requiring incisions and suturing, and can have serious and unpleasant side effects, including but not limited to scarring, infection, and loss of sensation.

[0005] One of the more common forms of cosmetic surgery is the “face-lift.” A face-lift is intended to enhance facial appearance by removing excess facial skin and tightening the remaining skin, thus removing wrinkles. A face-lift is traditionally performed by cutting and removing portions of the skin and underlying tissues on the face and neck. Two incisions are made around the ears and the skin on the face and neck is separated from the subcutaneous tissues. The skin is stretched, excess tissue and skin are removed by cutting with a scissors or scalpel, and the skin is pulled back and sutured around the ears. The tissue tightening occurs after healing of the incisions because less skin covers the same area of the face and neck and also because of the scars formed on the injured areas are contracting during the healing process.

[0006] Traditional face-lift procedures are not without potential drawbacks and side effects. One drawback of traditional cosmetic surgery is related to the use of scalpels and scissors. The use of these devices sometimes leads to significant bleeding, nerve damage, possible infection and/or lack of blood supply to some areas on the skin after operation. Discoloration of the skin and alopecia (baldness) are other possible side effects of the standard cosmetic surgery. The overall quality of the results of the surgery is also sometimes disappointing to the patients because of possible over-corrections, leading to undesired changes in the facial expression. Additionally, face-lift procedures require a long recovery period before swelling and bruising subside.

[0007] The use of lasers to improve the appearance of the skin has been also developed. Traditional laser resurfacing involves application of laser radiation to the external layer of the skin—the epidermis. Destruction of the epidermis leads to rejuvenation of the epidermis layer. The drawback of the laser resurfacing procedure is possible discoloration of the skin (red face) that can be permanent.

[0008] Another laser procedure involves using optical fibers for irradiation of the subcutaneous tissues, such as disclosed in U.S. Pat. No. Re36,903. This procedure is invasive and requires multiple surgical incisions for introduction of the optical fibers under the skin. The fibers deliver pulsed optical radiation that destroys the subcutaneous tissues as the tip of the fiber moves along predetermined lines on the face or neck. Debulking the subcutaneous fat and limited injury to the dermis along the multiple lines of the laser treatment results in contraction of the skin during the healing process, ultimately providing the face lift. The drawback of the method is its high price and possibility of infection.

[0009] Electrosurgical devices and methods utilizing high frequency electrical energy to treat a patient's skin, including resurfacing procedures and removal of pigmentation, scars, tattoos and hairs have been developed lately, such as disclosed in U.S. Pat. No. 6,264,652. The principle drawback of this technology is collateral damage to the surrounding and underlying tissues, which can lead to forming scars and skin discoloration.

[0010] Other forms of cosmetic surgery are also known. One example is liposuction, which is an invasive procedure that involves inserting a suction device under the skin and removing fat tissues. As with other invasive surgical procedures, there is always a risk of infection. In addition, because of the invasive nature of the procedure, physicians usually try to minimize the number of times the procedure must be performed and thus will remove as much fat tissue as possible during each procedure. Unfortunately, this procedure has resulted in patient deaths when too much tissue was removed. Assuming successful removal of excess fat tissue, further invasive surgery may be required to accomplish desired skin tightening.

[0011] The prior art to date, then, does not meet the desired goal of performing cosmetic surgery in a non-invasive manner while causing minimal or no scarring of the exterior surface of the skin and at the same time resulting in the skin tightening.

[0012] The term “electroporation” (EP) is used herein to refer to the use of a pulsed electric field to induce microscopic pores in the biological membranes, also commonly called a cell wall, of living cells. The cell membrane separates the inner volume of a cell, or cytosol, from the extracellular space, which is filled with lymph. This membrane performs several important functions, not the least of which is maintaining gradients of concentration of essential metabolic agents across the membrane. This task is performed by active protein transporters, built in the membrane and providing transport of the metabolites via controlled openings in the membrane. Normally, the active protein transporters, or pumps, which routinely provide transport of various metabolic agents, especially proteins, across the cell membrane, use either the energy of positive ions (hydrogen or sodium ions) passing from the positive potential of the intracellular space to the negative potential of the cytosol, or the energy of negative ions (chlorine ions) for movement across the membrane in the opposite direction. This energy supply for the protein transporters is provided by maintaining the potential difference across the membrane, which, in turn, is linked to the difference in concentrations of sodium and potassium ions across the membrane. When this potential difference is too low, thousands of the active transporters find themselves out of power.

[0013] Inducing relatively large pores in the cell membrane by electroporation creates the opportunity for a fluid communication through the pores between the cytosol and the extracellular space that may lead to a drastic reduction of these vitally important gradients of concentrations of the metabolic agents and thus a reduction in the potential difference across the membrane. Uncontrolled exchange of metabolic agents, such as ions of sodium, potassium, and calcium between a living cell and the extracellular space imposes on the cell intensive biochemical stress.

[0014] When a cell is undergoing biochemical stresses the major biochemical parameters of the cell are out of equilibrium and the cell cannot perform its routine functions. Invasion of very high concentration of calcium ions through membrane pores from the interstitial space between cells, where the calcium ion concentration is about 100 times higher than in the cytosol, can create such stresses by reducing the potential difference across the membrane. In an attempt to repair itself, the cell starts working in a damage control mode: an emergency production of actin filaments is triggered that extend across the large pores in the membrane in an attempt to bridge the edges of the pores, pull the edges together, and thereby seal the membrane. In muscle cells the calcium ion invasion may cause lethal structural damage by forcing the cell to over-contract and rupture itself. Small pores in the membrane created by a relatively short electric pulse can reseal themselves spontaneously and almost instantaneously after the removal of electric field. No significant damage to the cell is done in this case. Contrary to that, larger pores may become meta-stable with very long life time and cause irreversible damage. It can be said that, depending on the number, effective diameter -and life time of pores in the membrane, electroporation of the cell may result in significant metabolic or structural injury of the cell and/or its death. The cause of cell death after electroporation is believed to be an irreversible chemical imbalance and structural damage resulted from the fluid communication of the cytosol and the extracellular environment.

[0015] Below a certain limit of the electric field no pores are induced at all. This limit, usually referred to as the “lower EP limit” of electroporation, is different for different cells, depending, in part, on their sizes in an inverse relationship. That is, pores are induced in larger cells with smaller electric fields while smaller cells require larger electric fields. Above the lower EP limit the number of pores and their effective diameter increase with both the amplitude and duration of the electric field pulses.

[0016] Removing the electric field pulses enables the induced pores to reseal. This process of resealing of the pores and the ability of the cell to repair itself, discussed briefly above, currently is not well understood. The current understanding is that there is a significant range of electric field amplitudes and pulse durations in which cells survive electroporation and restore their viability thereafter. An electroporated cell may have open pores for as long as many minutes and still survive. The range of electric field amplitudes and pulse durations in which cells survive is successfully used in current biomedical practice for gene transfer and drug delivery inside living cells.

[0017] Nevertheless, the survivability of electroporated cells is limited. As the electric field amplitude and/or duration of pulses, increases, this limit, usually referred to as the “upper EP limit” of electroporation, is inevitably achieved. Above the upper EP limit, the number and sizes of pores in the cellular membrane become too large for a cell to survive. Multiple pulses cause approximately the same effect on the cells as one pulse with a duration equal to the total duration of all applied pulses. After application of an electrical pulse above the upper electroporation limit the cell cannot repair itself by any spontaneous or biological process and dies. The upper EP limit is defined by the combinations of the amplitudes of electric field and pulse durations that cause cellular death.

[0018] The vulnerability of cells to electroporation depends on their size: the larger the cell, the lower the electric field and duration of a pulse capable of killing it. If cells of different sizes are exposed to the same electric field, the largest cells will die first. Thus, this ability of electroporation to discriminate cells by their sizes may be used to selectively kill large cells in the human body.

[0019] In the previously referred to application for U.S. patent application entitled “Apparatus and Method for Reducing Subcutaneous Fat Deposits, Virtual Face Lift and Body Sculpting by Electroporation”, Ser. No. 09/931,672, filed Aug. 17, 2001, an apparatus and method for performing non-invasive treatment of the human face and body by electroporation in lieu of cosmetic surgery is disclosed. The apparatus comprises a high voltage pulse generator and an applicator having two or more electrodes utilized in close mechanical and electrical proximity with the patient's skin to apply electrical pulses thereto. The applicator may include at least two electrodes with one electrode having a sharp tip and another having a flat surface. High voltage pulses delivered to the electrodes create at the tip of the sharp electrode an electric field high enough to cause death of relatively large subcutaneous fat cells by electroporation. Moving the electrode tip along the skin creates a line of dead subcutaneous fat cells, which later are metabolized by the body. Multiple applications of the electrode along predetermined lines on the face or neck create shrinkage of the skin and the subcutaneous fat reduction under the treated area.

[0020] The electroporation in-vivo, employed in the disclosed method is a non-invasive treatment of subcutaneous fat, which, as was previously described before, involves application of high amplitude electric pulses between external electrodes to cause death by electroporation of the subcutaneous fat cells. Fat cells, being typically larger than other cells of the body, are more easily killed by electroporation treatment than are smaller lean muscle cells. The electric field, applied to the external electrodes, is efficient for cell killing in the subcutaneous layer of fat tissue directly under the skin. However, the amplitude of the field significantly decreases with increasing the depth of the deposits of fat cells. The deeper penetration of the electric field may be achieved by increasing the distance between electrodes with simultaneous increase in the operating voltage. This approach, though, leads to concomitant increase of the volume that is treated by electroporation. Occasionally, during such cosmetic and body sculpting procedures as described above, a small volume of deep subcutaneous fat deposit must be treated. The non-invasive method of treating subcutaneous tissue by electroporation as described in the earlier referenced patent application, in which the high voltage pulses are applied to the external electrodes, is sometimes difficult to apply to deep fat deposits especially when a fine spatial resolution is required

[0021] It would be desirable to have available an apparatus and a method for electroporation treatment to reduce deep fat deposits by allowing deep localized application of the electroporation pulses that can provide high spatial resolution of the body sculpting. Preferably, such apparatus and methods would also be minimally invasive.

[0022] The present invention provides an apparatus and method for creation of a controlled electroporation injury to deep subcutaneous fat tissues that, with the healing that follows, leads to permanent loss of the fat cells in the treated tissue. According to present invention an electric field capable of killing fat cells in deep subcutaneous deposits may be applied by a set of needle electrodes, configured for placement deeply under the skin. An apparatus according to the current invention comprises a voltage pulse generator, an applicator with two or multiple electrodes of different shapes and sizes, and a cable connecting the electrodes to the pulse generator. The pulse generator produces a sequence of high voltage pulses of predetermined amplitude, duration and number to cause necrosis in a treated area of the subcutaneous tissue.

[0023] A method of weight loss and body sculpturing in accord with the present invention comprises application of electrical pulses to the electrodes positioned under the skin in a treatment area of the subcutaneous fat tissue. The amplitude, duration and number of applied pulses are selected to cause necrosis of fat cells at a predetermined distance around the needles in the subcutaneous tissue. During the treatment a number of sites in a predetermined pattern are exposed to electroporation. Later, during the healing process the treated area contracts as the electroporated cells die and are metabolized by the body, thus reducing volume of fat tissue and providing desired change of body contours. The injury to the tissues made by electroporation is very selective, targeting only large fat cell and not damaging the epidermis, the most external layer of the skin. As a matter of fact, in accordance with the current invention, the electrical field is applied only to the deep subcutaneous fat deposits, no electric field is applied to the skin of the patient.

[0024] The present invention, as well as its various features and advantages, will become evident to those skilled in the art when the following description of the invention is read in conjunction with the accompanying drawings as briefly described below and the appended claims. Throughout the drawings, like numerals refer to similar or identical parts.

[0025] FIG. 1 is a schematic illustration of an electroporation system for treatment of deep subcutaneous fat deposits.

[0026] FIG. 2 shows time diagrams for high voltage pulses during EP treatment wherein FIG. 2aillustrates unipolar pulsing and FIG. 2billustrates bipolar pulsing.

[0027] FIG. 3 illustrates a one-needle applicator with two electrodes.

[0028] FIG. 4 illustrates an embodiment of an applicator comprising one needle in combination with an external patch electrode wherein FIG. 4aprovides a plan view and FIG. 4bprovides a cross-sectional view taken along viewing plane 4b—4b.

[0029] FIG. 5 illustrates an embodiment of the applicator comprising an array of needle electrodes.

[0030] FIG. 6 illustrates in orthogonal views in FIGS. 6aand 6ban embodiment of the applicator comprising needle electrodes without insulated parts.

[0031] FIG. 1 shows schematically an electroporation system 100 for in-vivo treatment of deep subcutaneous fat deposits. The system 100 includes a high voltage electroporation pulse generator 101 connected by an appropriate connector 102 to an applicator 103. Applicator 103 may include a handle 104 and a pair of needle 120 and 122 extending therefrom. Handle 104 may be used by the operator for the safe and efficacious placement of the needles 120 and 122 in a selected-for-treatment anatomical site. Needles 120 and 122 may include proximal insulated portions 124 and 126, respectively, central uninsulated portions 128 and 130, respectively, and distal insulated portions 132 and 134. Preferably, distal portions 132 and 134 includes sharpened ends or tips 136 and 138, respectively.

[0032] As illustrated in the Figure, an operator of system 100 will use handle 104 to push the tips 136 and 138 through the skin 150 of the patient into a deep subcutaneous fat deposit 152. The sharpened tips 136 and 138 facilitate penetration of the skin 150 and fat tissue 152 while minimizing pain or serious discomfort to the patient. Insulated proximal portions 124 and 126 of needles 120 and 122, respectively, provide electrical insulation from the skin 150 during an EP treatment. That is, this insulation prevents a current flow from the needles 120 and 122 through the skin and with it an associated discomfort of the patient. Similarly, the insulated distal portions 132 and 134 of needles 120 and 122 helps to avoid spark discharges between the tips during high voltage electroporation pulsing.

[0033] Central portions 128 and 130 form the electrodes for the system 10, which as noted are uninsulated. The electrodes 128 and 130 are in close electrical contact with the surrounding tissue 152 and provide a pulsed electrical field, as indicated by shown by arrows 160, to the treatment zone 162 between and around electrodes 128 and 130, as indicated by dotted line 162. It will be understood that the treatment zone is actually a three dimensional zone extending in all directions from the electrodes 128 and 130.

[0034] The larger the diameter of the cells or the higher applied voltage, the larger treatment zone 162 will be where the cells are actually killed. It should be mentioned that not all cells die at any point of the treatment zone. The smaller fat cells will survive. As was mentioned early, cell killing by electroporation is selective on the cell size and the upper EP limit is higher for small cells. Small fat cells, for which applied electric field is below the upper electroporation limit, will survive any reasonable number of electric pulses without any morphological or functional damage and will stay in the tissue. Also, there is no electroporation treatment for the tissues interfacing the insulated parts of the needles.

[0035] A computer 170 connected by an appropriate connector 172 to EP generator 101, may be provided to control the whole procedure of EP treatment: the predetermined amplitude, duration, and number of EP pulses supplied to the electrodes 128 and 130. The EP pulses may be applied with a repetition rate of about 1 to about 50 Hz and may have a current peak of about 0.5 to about 10 A depending on the size and shape of electrodes. Generally, the voltage of the EP pulses can be in the range of about 50 V to about 5000 V with a duration from about 10 microseconds to about 10.0 milliseconds depending on the location of the treated segment of the body, the sizes and shapes of the electrodes, and the distance between the electrodes. Regardless of the possible configuration of the electrodes and the voltages applied to the treatment volume, the voltage applied to an individual subcutaneous fat cell should fall in the range of about 2 to about 10 V per cell to be able to kill it.

[0036] To achieve successful cell killing by electroporation the electric field applied to the treated volume of cells must be above the upper EP limit for the cells. The probability of cell killing increases if longer or multiple pulses are employed.

[0037] According to present invention high voltage pulses of different waveforms may be used for the EP treatment. The pulses may be rectangular or exponential in shape, be unipolar (positive or negative only) or bipolar (positive and negative). Bipolar rectangular pulses are known to be very efficient in cell killing by electroporation. This is because both directions of the electrical field, positive and negative, are equally efficient in creating pores in cellular membranes, and the electric field strength, contrary to the exponential pulses, stays high during the whole pulse. The efficiency results because electroporation is a process related to the difference in the energy of the porous and non-porous membrane in the presence of an electric field. The energy difference depends on the square of the amplitude (or strength) of the electric field (i.e., E²) and does not depend on the sign or polarity (+ or −) of the electric field.

[0038] From a practical stand point, however, applying balanced pulses during in-vivo electroporation treatment has one important advantage. Contrary to unipolar pulsing, that carries a direct current component into the treated tissue and creates undesired electrolytic effects on the interface of the electrodes and tissues, bipolar pulsing is free from these drawbacks. With bipolar pulsing of the field, problems such as metal depositions from the electrodes or chemical decomposition of tissue during treatment are largely if not completely avoided.

[0039] These advantageous properties of balanced pulses, namely, high efficiency in cell killing and freedom from electrolytic effects, make using rectangular bipolar balanced pulses a preferred mode for electroporation pulsing in the current invention. Technically, balancing of two pulses of the opposite polarities may be easily achieved by using a pulse generator having a direct current blocking capacitor electrically coupled in series to the needle electrodes.

[0040] In FIG. 2aand 2bplots of high voltage EP pulses against time are shown. In FIG. 2athe upper curve shows a plot of rectangular balanced pulses, the preferred embodiment and the lower curve shows exponential balanced pulses. FIG. 2bdepicts rectangular and exponential unipolar pulses in the upper and lower curves, respectively.

[0041] In FIG. 3 another embodiment 300 of the needle applicator is shown. Needle applicator 300 comprises a single needle 310 with two axially separated electrodes 328 and 330 of opposite polarity insulated from each other and separated by insulator 308. The needle may be made of a hollow tube carrying inside two conductors connecting electrodes 328 and 330 via cable 302 to the output of the EP generator, not shown in the figure. Proximal end 325 of the needle 310 is covered with an insulation layer to protect the skin of the patient during treatment from an electric current and discomfort associated with it. To avoid sparking from the distal end 333 of the applicator the needle 310 may be made of insulating material or of a metal piece electrically insulated from the electrodes 328 and 330. Additionally, distal end 333 may have a sharp tip 337.

[0042] The electric field between electrodes 328 and 330 is shown by lines 360. Dotted lines 362 delineate the treatment zone, where the electric field is the highest and where actual killing cells by electroporation occurs.

[0043] Yet another embodiment 400 of the needle applicator is shown in FIG. 4 in two substantially orthogonal views, namely FIGS. 4aand 4b. Applicator 400 comprises a needle 410 with an electrode 428 combined with a patch electrode 430. Patch electrode 430 is placed on the skin 450 of the patient near the treatment site, which is delineated by a dotted line 462. Needle 410 may include a sharp tip 436 and insulated proximal and distal portions 442 and 433 on either side of electrode portion 428 of needle 410. The electrical field lines generated between electrodes 428 and 430 are indicated by lines 460. High voltage EP pulses during treatment are delivered to the electrodes 428 and 430 via appropriate conductors 454 and 455, respectively, which are connected to the connector 402 coupled to the output of the EP generator 101, not shown in the FIG. 4.

[0044] During use of the needle applicator 400, the electroporation leading to cellular death occurs only around the conductive surface, i.e., electrode 428, of the needle placed in the tissue. No electroporation takes place near the patch electrode 430 on the skin because the value of the electric field near its surface is less than the upper EP limit. FIG. 4bshows cross section of the applicator. Dotted line 462 delineates the treatment zone around the electrode 428 where the fat cells are killed.

[0045] FIG. 5 shows yet another implementation 500 of a needle applicator in accord with the present invention. Applicator 500 comprises a handle 504 supporting a needle frame 505. Needle frame 505 supports a plurality of needles 520 of one polarity (positive) and a plurality of needles 522 including an electrode of the other polarity (negative), with each needle of one polarity being adjacent to one or more needles of the other polarity. Handle 504 is connected via connector 502 to the output of the EP generator 101 (not shown in the Figure). The needles 520 and 522 in the needle array alternately have positive and negative polarity. The needles 520 and 522 may include a proximal insulated portion 524 and 526, central electrode portions 528 and 530, and distal insulated portions 536 and 538 respectively. Each needle 520 and 522 will also preferably include sharp tip 536 and 538. For EP treatment of subcutaneous deposits the needles are placed preferably normally to the skin. One of benefits of this configuration is that the tissue electroporation occurs in thin cylindrical layers around the electrodes and later, during healing process, macrophages from nearby blood vessels will travel a shorter distance to the damaged cells. Thus, this configuration may accelerate the disposal of the dead fat cells.

[0046] Yet another implementation of the needle applicator is shown in FIG. 6. Applicator 600 may include a handle 604 and a pair of needle 620 and 622 extending therefrom. Handle 604 may be used by the operator for the safe and efficacious placement of the needles 620 and 622 in a selected-for-treatment anatomical site. The sharpened tips 636 and 638 facilitate penetration of the skin 650 and fat tissue 652 while minimizing pain or serious discomfort to the patient. In this implementation of the current invention the whole needles 620 and 622 perform function of electrodes; that is, the needles 620 and 622 do not include insulated portions as in the previously described embodiments. Via an appropriate connector 602 needles 620 and 622 are connected to the EP generator (not shown in the Figures) providing high voltage pulses during treatment. Electric field lines between electrodes 620 and 622 are shown by arrows 660. Dotted line 662 shows the treatment area of the fat tissue 652 where electroporation actually kills fat cells.

[0047] Needle electrode diameters may fall in a range of about 0.3 mm to about 1.0 mm, which corresponds to the standard of minimally invasive size. The distance between adjacent needles may be in a range of several mm to several cm. Applied voltage, depending on the distance between needles and the size of the fat cells to be killed, may vary in a wide range from about 100 V to several hundreds and even thousands of volts. In any case the resultant electric field applied to the treated fat cells must be above their upper electroporation limit, or about 2 to about 10 V per cell. The electroporation pulses during treatment may be applied simultaneously to all electrodes or in a sequence of sets of two to several electrodes throughout the whole treated area. The number of pulses per treatment of a selected site may vary from several pulses to several tens of pulses. Preferred duration of the pulses is from about 10 microseconds to about 10 milliseconds.

[0048] A method for electroporation treatment of deep subcutaneous fat deposits comprises providing a high voltage pulse generator for generation EP pulses and a needle applicator. The needle applicator or needle applicator and pad electrode may be placed by a physician in an anatomically selected site of treatment under ultrasound or other type of imaging guidance. After the needle placement a sequence of high voltage EP pulses is applied to the electrodes. The electrodes may be placed in plurality of treatment sites in accordance with a treatment plan developed by a physician. Sequences of the high voltage EP pulses are repeatedly applied to the electrodes. After a session of electroporation treatment the remnants of fat cells and released lips will be metabolized and removed by the patient's body over about a two week period. A subsequent electroporation treatment can then be performed with new treatment sites selected for the electroporation treatment. In this manner, then, a patient's body can be sculpted as desired.

[0049] The present invention has been described in language more or less specific as to the apparatus and method features. It is to be understood, however, that the present invention is not limited to the specific features described, since the apparatus and method herein disclosed comprise exemplary forms of putting the present invention into effect. For example, while the needles have been described as having sharp tips, blunted end needles may also be used. Additionally, as indicated in the Figures, insulation may be used on the needles in some embodiments, but not others. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalency and other applicable judicial doctrines.