WO2014133870A1

WO2014133870A1 - Electric pulse generators with non-penetrating applicator tips

Info

Publication number: WO2014133870A1
Application number: PCT/US2014/017453
Authority: WO
Inventors: Jack Robert WEISSBERG; Sudeep Deshpande; Jonathan Gregory LASCH; Mac Clements CHAPMAN; Fikret Nuri Kirkbir
Original assignee: Alfred E. Mann Institute For Biomedical Engineering At The University Of Southern California
Priority date: 2013-02-28
Filing date: 2014-02-20
Publication date: 2014-09-04

Abstract

This disclosure relates to an in vivo treatment of a skin lesion of a mammal comprising application of electrical energy to the skin lesion in a form of electrical pulses. Electric pulse generators with non-penetrating tips may be used for such in vivo treatments of the skin lesions. At least one electrical pulse is applied. The pulse duration may be at least 1 nanosecond at the full-width-half-maximum. This treatment may prevent at least growth of the lesion.

Description

ELECTRIC PULSE GENERATORS WITH NON-PENETRATING

APPLICATOR TIPS

CROSS-REFERENCE TO RELATED APPLICATIONS

[001] This application is based upon and claims priority to U.S. Provisional Application Serial Number 61/770,884, filed February 28, 2013, attorney docket no. 064693-0277, entitled "Electric Pulse Generators with Non-Penetrating Applicator Tips", the entire content of which is incorporated herein by reference.

TECHNICAL FIELD

[002] This disclosure relates to electrical pulse generators and particularly to electrical pulse generators with non-penetrating applicator tips. This disclosure also relates to treatment of skin lesions by delivery of electric pulses to such lesions.

DESCRIPTION OF RELATED ART

[003] Ultra-short, high-field strength electric pulses may be used in the electroperturbation of biological cells. For example, these electric pulses may be used in treatment of human cells and tissue including tumor cells such as basal cell carcinoma, squamous cell carcinoma and melanoma. For a detailed discussion of such applications, for example, see, Garon et al. "In Vitro and In Vivo Evaluation and a Case Report of Intense Nanosecond Pulsed Electric Field as a Local Therapy for Human Malignancies", Int. J. Cancer, vol. 121 , 2007, pages 675-682. The entire content of this publication is incorporated herein by reference.

[004] The voltage induced across a cell membrane may depend on the pulse length and pulse amplitude. Pulses longer than about 1 microsecond may charge the outer cell membrane and lead to opening of pores, either temporarily or permanently. Permanent openings may result in cell death.

[005] Pulses much shorter than about 1 microsecond may affect the cell interior without adversely or permanently affecting the outer cell membrane. Such shorter pulses with a field strength in the range of 10 kV/cm to 100 kV/cm may trigger apoptosis or programmed cell death. Higher amplitude and shorter electric

DM US ₄982₄881-1.06₄693.0293 pulses are useful in manipulating intracellular structures such as nuclei and mitochondria.

[006] Nanosecond high voltage pulse generators have been proposed for biological and medical applications. For example, see: Gundersen et al. "Nanosecond Pulse Generator Using a Fast Recovery Diode", IEEE 26.sup.th Power Modulator Conference, 2004, pages 603-606; Tang et al. "Solid-State High Voltage Nanosecond Pulse Generator," IEEE Pulsed Power Conference, 2005, pages 1 199-1202; Tang et al. "Diode Opening Switch Based Nanosecond High Voltage Pulse Generators for Biological and Medical Applications", IEEE Transactions on Dielectrics and Electrical Insulation, Vol. 14, No. 4, 2007, pages 878-883; Yampolsky et al., "Repetitive Power Pulse Generator With Fast Rising Pulse" U.S. Pat. No. 6,831 ,377; Schoenbach et al. "Method and Apparatus for Intracellular Electro-Manipulation", U.S. Patent No. 6,326,177; Gundersen et al., "Method for Intracellular Modifications Within Living Cells Using Pulsed Electric Fields", U.S. Patent Publication No. 2006/0062074; Kuthi et al., "High Voltage Nanosecond Pulse Generator Using Fast Recovery Diodes for Cell Electro- Manipulation", U.S. Patent No. 7,767,433; Krishnaswamy et al., "Compact Subnanosecond High Voltage Pulse Generation System for Cell Electro- Manipulation", U.S. Patent Publication No. 2008/0231337; Sanders et al. "Nanosecond Pulse Generator", U.S. Patent Publication No. 2010/0038971 ; and Stern "Apparatus and Method for Treatment of Tissue" U.S. Patent No. 6,413,255. The entire content of these publications is incorporated herein by reference.

SUMMARY

[007] This disclosure relates to a system for delivery of electrical pulses to a tissue. This system may comprise a pulse generator configured to generate at least one pulse having duration of no more than 1 ,000 nanoseconds at the full- width-at-half-maximum. This system may further comprise a pulse delivery device comprising at least one delivery (e.g. active) electrode and at least one ground (i.e. return, at or near ground potential) electrode that are connected to the pulse generator.

[008] The pulse delivery device may further comprise electrical insulation between the at least one delivery electrode and the at least one ground electrode.

DM US ₄982₄881-1.06₄693.0293 The electrical insulation may comprise fluoropolymer, parylene, polyimide, ceramic, glass or mixtures thereof. The fluoropolymer may be polytetrafluoroethylene.

[009] The at least one delivery electrode, the at least one ground electrode, and the electrical insulation each has a distal end that collectively form a substantially smooth surface that will not penetrate the tissue when pressed against the tissue with pressure sufficient to form an electrical connection between the tissue and the distal ends of the at least one delivery electrode and the at least one ground electrode. The substantially smooth surface may be a substantially flat surface.

[0010] The system may include multiple ground electrodes and/or multiple delivery electrodes.

[0011] The system may be configured to generate at least one pulse of duration of no longer than 100 nanoseconds at the full-width-at-half-maximum. The system also may be configured to generate at least one pulse of duration in the range of 1 nanosecond and 100 nanoseconds at the full-width-at-half- maximum. The system also may be configured to generate at least one pulse of duration in the range of 1 nanosecond and 30 nanoseconds at the full-width-at- half-maximum.

[0012] The system may be configured to generate at least one pulse with amplitude of at least 1 kV or at least 10 kV or at least 20 kV when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection. The electric field formed by the pulses may be at least 1 kV/cm, 10 kV/cm or 20 kV/cm when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection.

[0013] The system may be configured to form an electric field of at least 10 kV/cm at the peak amplitude of the pulse at a depth of about 0.5 mm below the skin surface when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection. The system may also be configured to form an electric field of at least 20 kV/cm at the peak amplitude of the pulse at a depth of about 0.5 mm

DM US 49824881-1.064693.0293 - 3 - below the skin surface when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection. The system may also be configured to form an electric field of at least 20 kV/cm at the peak amplitude of the pulse at a depth of about 2 mm below the skin surface when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection. The system may also be configured to form an electric field of at least 20 kV/cm at the peak amplitude of the pulse at a depth of about 4 mm below the skin surface when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection.

[0014] The pulse delivery device may also comprise an electrode array. The electrode array may comprise at least two delivery electrodes and at least two ground electrodes.

[0015] This disclosure also relates to a treatment of a skin lesion of a mammal comprising application of electrical energy to the skin lesion in the form of at least one electrical pulse by using the system for delivery of electrical pulses to a tissue. Multiple pulses may also be applied. The pulse duration may be no longer than 1 ,000 nanoseconds at the full-width-half-maximum. The energy may be applied in a manner that may prevent at least growth of the lesion.

[0016] The skin lesion may be any deviation of skin from a healthy or a normal condition. Examples of skin lesions include skin diseases, conditions, injuries, defects, abnormalities or combinations thereof. For example, such skin lesions include malignancies (such as basal cell carcinomas, squamous cell carcinomas and melanoma), precancerous lesions (such as actinic keratosis), human papilloma virus (HPV) infected cells (such as verruca vulgaris or common warts, plantar warts, genital warts), immune-related conditions (such as psoriasis), other skin abnormalities (such as seborrheic keratosis and acrocordon) or combinations thereof. In one embodiment, the skin lesion is basal cell carcinoma, papilloma, squamous cell carcinoma, actinic keratosis, warts or combinations thereof. The skin lesion may also comprise common warts. Or the skin lesion may also comprise actinic keratosis.

DM US 49824881-1.064693.0293 [0017] The applied electrical energy may be sufficient to prevent growth of the skin lesion for duration of at least one week after the treatment. The applied electrical energy may be sufficient to reduce the skin lesion volume by at least 30% within eight days after the treatment. The skin lesion volume reduction may be at least 50% or even be at least 80%. The applied electrical energy may be sufficient to clear the skin lesion within eight days after the treatment. The applied energy may be sufficient to reduce the skin lesion volume within eight days after the treatment for at least 40% of cases. The applied energy may be sufficient to reduce the skin lesion volume within eight days after the treatment for at least 80% of cases. The applied energy may be sufficient to reduce the skin lesion volume by at least 30% within eight days after the treatment for at least 80% of cases. The applied energy may eliminate (i.e. clear) the skin lesion. The applied electrical energy may be at least 65 mJ per mm³ of the skin lesion. It may also be at least 260.0 mJ/mm³ or at least 520.0 mJ/mm³.

[0018] These, as well as other components, steps, features, objects, benefits, and advantages, will now become clear from a review of the following detailed description of illustrative embodiments, the accompanying drawings, and the claims.

BRIEF DESCRIPTION OF DRAWINGS

[0019] The drawings disclose illustrative embodiments. They do not set forth all embodiments. Other embodiments may be used in addition or instead. Details which may be apparent or unnecessary may be omitted to save space or for more effective illustration. Conversely, some embodiments may be practiced without all of the details which are disclosed. When the same numeral appears in different drawings, it refers to the same or like components or steps.

[0020] FIG. 1 : Example of a system for generation and delivery of electrical nanopulses to a skin lesion.

[0021 ] FIG. 2: Example of a simplified diode pulse generator.

[0022] FIG. 3: Example of an electrical pulse generated by the system shown in FIG. 1 .

DM US ₄982₄881-1.06₄693.0293 - 5 - [0023] FIG.4: Example of a non-penetrating cylindrical distal end of the pulse delivery device: (a) longitudinal cross-sectional view and (b) radial cross-sectional view.

[0024] FIG.5: Example of a non-penetrating cylindrical distal end of the pulse delivery device: (a) longitudinal cross-sectional view and (b) radial cross-sectional view.

[0025] FIG.6: The modeling result for electric field of about 10 kV/cm, which is formed at the peak pulse amplitude of about 7 kV, for the applicator tip schematically shown in FIG. 5.

[0026] FIG.7: The modeling result for electric field of about 15 kV/cm, which is formed at the peak pulse amplitude of about 7 kV, for the applicator tip schematically shown in FIG. 5.

[0027] FIG.8: The modeling result for electric field of about 20 kV/cm, which is formed at the peak pulse amplitude of about 7 kV, for the applicator tip schematically shown in FIG. 5.

[0028] FIG.9: The modeling result for electric field of about 25 kV/cm, which is formed at the peak pulse amplitude of about 7 kV, for the applicator tip schematically shown in FIG. 5.

[0029] FIG.10: The modeling results for penetration depths of the electric field that are formed at the peak pulse amplitudes varying in the range of 7 kV to 20 kV, for the applicator tip schematically shown in FIG. 5

[0030] FIG.11 : The modeling result for electric field of about 25 kV/cm, which is formed at the peak pulse amplitude of about 10 kV, for the applicator tip schematically shown in FIG. 5.

[0031] FIG.12: The modeling result for electric field of about 25 kV/cm, which is formed at the peak pulse amplitude of about 15 kV, for the applicator tip schematically shown in FIG. 5.

[0032] FIG.13: The modeling result for electric field of about 25 kV/cm, which is formed at the peak pulse amplitude of about 20 kV, for the applicator tip schematically shown in FIG. 5.

DM US 49824881-1.064693.0293 DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0033] Illustrative embodiments are now discussed. Other embodiments may be used in addition or instead. Details which may be apparent or unnecessary may be omitted to save space or for a more effective presentation. Conversely, some embodiments may be practiced without all of the details which are disclosed.

[0034] This disclosure relates to an in vivo treatment of skin lesions of mammals by application of at least one electrical pulse with duration of 1 ,000 nanoseconds (ns) or less as measured at the full-width-half-maximum (FWHM) of the pulse wave.

[0035] The skin lesion that may be treated in vivo by the devices described herein may be any deviation of skin from a healthy or a normal condition. Examples of the skin lesions include skin diseases, conditions, injuries, defects, abnormalities or combinations of thereof. For example, such skin lesions may be malignancies (such as basal cell carcinomas, squamous cell carcinoma and melanoma), precancerous lesions (such as actinic keratosis), human papilloma virus (HPV) infected cells (such as verruca vulgaris or common warts, plantar warts, genital warts), immune-related conditions (such as psoriasis), other skin abnormalities (such as seborrheic keratosis and acrocordon) and combinations thereof. The skin lesion may also include aged skin, wrinkled skin or damaged skin. An example of the damaged skin is the skin damaged by sun radiation. In one embodiment, the skin lesions may be basal cell carcinoma (including papilloma), squamous cell carcinoma, actinic keratosis, warts, or combinations thereof. In one embodiment, the skin lesion may be a skin lesion of a human. In this embodiment, the skin lesion may comprise basal cell carcinoma, squamous cell carcinoma, actinic keratosis, warts, or combinations thereof. In this embodiment, the skin lesion may also comprise common warts, actinic keratosis, or combinations thereof. The skin lesion may be a common wart of a human. The skin lesion may also be an actinic keratosis of a human.

[0036] The in vivo treatment may be achieved by providing electrical energy to the skin lesion in a form of electrical pulses. During this treatment, tissue removal may not be intentional and, if it happens, may not be substantial. Thus, the

DM US 49824881-1.064693.0293 - 7 - treatment may thereby be advantageous over current or other proposed treatment techniques, since it may achieve its purpose with no substantial tissue removal.

[0037] The in vivo treatment of the skin lesion may prevent growth of the lesion. In one embodiment, the treatment may reduce the volume of the skin lesion. That is, the treatment may induce shrinkage of the lesion. This shrinkage may be at least 10%, 20%, 30%, 60%, 70%, 80%, or 90%. Yet, in another embodiment, it may be a treatment to reduce the skin lesion volume to a negligible level (i.e. clearance of the lesion). In yet other embodiments, the lesion growth prevention or the lesion volume reduction may be achieved in at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% of the cases.

[0038] When the lesion volume shrinks to a negligible size (i.e. about 100 %), the lesion is "cleared". If the lesion growth or shrinkage is less than 10% after the treatment, the lesion growth is considered to have been "prevented" or that there is "no change". If the lesion shrinkage is in the range of >10 % and <50 %, it is concluded that there is lesion "shrinkage". If the lesion shrinkage is in the range of >50 % and <100 %, it is concluded that there is "substantial shrinkage". If the lesion growth is in the range of >10 % to <100 %, it is concluded that there is lesion "growth". And if the lesion growth is >100 %, it is concluded that there is "substantial growth".

[0039] The treatment results may be permanent or temporary. In one embodiment, the growth prevention, or the shrinkage or the clearance may last for a duration of at least 7 days, at least 10 days, at least 20 days, at least 30 days, at least 40 days, at least 50 days, at least 60 days, at least 70 days, at least 80 days, at least 90 days, at least 100 days, or at least 1 10 days.

[0040] Any system may be used for delivery of electrical nanopulses with a duration of 1 ,000 ns or less at FWHM to the skin lesion.

[0041] The system may comprise a power supply, a controller, a pulse generator, and a pulse delivery device (e.g., a wand). An example of this system is schematically shown in FIG. 1.

[0042] The pulse generator may be any pulse generator that is capable of generating pulses with a duration of 1 ,000 ns or less at FWHM. Examples of such pulse generators are disclosed in Kuthi et al., "High Voltage Nanosecond Pulse

DM US ₄982₄881-1.06₄693.0293 Generator Using Fast Recovery Diodes for Cell Electro-Manipulation", U.S. Patent No. 7,767,433; Sanders et al. "Nanosecond Pulse Generator", U.S. Patent Publication No. 2010/0038971 ; Schoenbach et al. "Method and Apparatus for Intracellular Electro-Manipulation", U.S. Patent No. 6,326,177; Weissberg et al. "In Vivo Treatment of Skin Lesions by Electrical Nanopulses", U.S. Patent Publication No. 2013/0041443; and Weissberg et al. "Electric Pulse Generators", U.S. Patent Publication No. 2013/0150935. The entire content of these patents is incorporated herein by reference.

[0043] The pulse delivery device may be any device that can deliver the electrical pulses to the skin lesion. This device may comprise at least one delivery (e.g. active) electrode. This device may further comprise at least one ground (i.e. return, at or near ground potential) electrode. This device may further comprise an electrical insulation between the at least one delivery electrode and the at least one ground electrode. Both the at least one delivery electrode and the at least one ground electrode may deliver the electrical pulses without substantially penetrating the said electrodes into the skin lesion, below its surface. For example, the at least one delivery electrode, the at least one ground electrode, and the electrical insulation each having a distal end that collectively form a substantially smooth surface that will not penetrate the tissue when pressed against the tissue with pressure sufficient to form an electrical connection between the tissue and the distal ends of the at least one delivery electrode and the at least one ground electrode. For example, this substantially smooth surface may be a substantially flat surface. In an example of the substantially flat surface, the electrodes may slightly protrude from a substantially flat surface. This slight protrusion may be no longer than 0.5 mm, 1 mm or 2 mm. In another example, the substantially smooth surface is a curved surface. For example, the curved surface is a convex surface or a concave surface or a surface that is in part a concave surface and in part a convex surface (like cyma reversa).

[0044] An example of the distal end of the electrical pulse delivery device is illustrated in FIG. 4. In this example, the distal end is a cylinder and the nonpenetrating surface is substantially flat. This electrical pulse delivery device has one delivery electrode placed at the center and one ground electrode surrounding the delivery electrode, forming a complete "ring". The space between the delivery

DM US ₄982₄881-1.06₄693.0293 - 9 - electrode and the ground electrode is filled with an electrically insulating material, such as teflon or a metal oxide.

[0045] Other electrode configurations, for example those with different electrode spacing, may also be used for the treatment of the lesions. However, as the effect of these short pulses on cells is largely dependent upon the strength of the electric field, an increase in the return and active electrode spacing may have to be accompanied by a proportional increase in output voltage to maintain the required field for the effect on cells. Similarly, if the spacing is reduced, the voltage could be proportionally decreased.

[0046] An array of ground electrode and delivery electrode configurations may also be used to construct the electrical pulse delivery device to deliver the electrical pulses to the skin lesions. For example, an electrode array comprising at least two delivery electrodes and at least two ground electrodes may be used for this purpose.

[0047] The electrical energy may be applied to the skin lesion in the form of at least one electrical pulse. In one embodiment, at least 10 pulses, at least 100 pulses or at least 1 ,000 pulses may be applied to treat the lesion during a single treatment.

[0048] In one embodiment, the duration of one or more of the pulses at FWHM may be in the range of 0.01 ns to 1 ,000 ns. The duration of one or more of the pulses at FWHM may also be in the range of 1 ns to 100 ns or in the range of 1 ns to 30 ns. Frequency of pulses may be in the range of 0.1 Hertz (Hz) and 100,000 Hz. The frequency of pulses may also be in the range of 1 Hz to 1 ,000 Hz.

[0049] The electrical energy applied per volume of the skin lesion may be at least 65 mJ/mm³. The applied electrical energy per volume of the skin lesion may also be at least 260 mJ/mm³. In yet another embodiment, the applied electrical energy per volume of the skin lesion may also be at least 520 mJ/mm³.

[0050] The electric pulse forms an electric field between the at least one delivery electrode and the at least one ground electrode. The formation of this electric field below the tissue surface may prevent at least the growth of the lesion. This electric field may also cause shrinkage or clearance of the lesion. The electric field formed by each pulse may be at least 1 kV/cm, 10 kV/cm or 20 kV/cm

DM US 49824881-1.064693.0293 - 10 - at the peak amplitude of the pulse when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection. The electric field formed by each pulse may also be in the range of 1 kV/cm to 1 ,000 kV/cm at the peak amplitude of the pulse when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection. Yet, in another embodiment, the electric field formed by each pulse may be in the range of 1 kV/cm to 100 kV/cm at the peak amplitude of the pulse when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection. The electric field formed by each pulse may also be in the range of 10 kV/cm to 50 kV/cm at the peak amplitude of the pulse when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection.

EXAMPLE 1 . NANOPULSE GENERATOR AND ELECTRICAL NANOPULSES

[0051 ] An electrical pulse generation and delivery system, schematically shown in FIG. 1 , comprising a pulse generator was constructed at the Alfred E. Mann Institute for Biomedical Engineering at the University of Southern California (Los Angeles, California). In this system, the controller provided control signals to both the power supply and the pulse generator. The power supply provided power to both the controller and the pulse generator. And the pulse generator generated the high voltage nanosecond pulses. The wand comprised a pulse trigger button and a tip with electrodes. The pulse trigger button controls the delivery of the pulses from the pulse generator.

[0052] An example of the pulse generator is schematically shown in FIG. 2. This pulse generator was previously disclosed in detail in U.S. Patent No. 7,767,433 to Kuthi et al. and in U.S. Patent Application U.S. 2010/0038971 to Sanders, the content of which is incorporated by reference. This pulse generator is briefly described below.

[0053] As shown in FIG. 2, the diode pulse generator may include a tank circuit consisting of inductances l_i and L₂ and capacitances Ci and C₂. The tank circuit may be connected in series with a diode D across which a load RL to be driven

DM US 49824881-1.064693.0293 - 1 1 - may be connected. This load is the resistance of the lesion or tissue. The pulse generator may include a switching system, such as switches Si and S₂, which may be electronic. A voltage supply V_in may be connected to the diode pulse generator through a resistance R_Ch-

[0054] Before the beginning of a pulse cycle, the switch Si may be open and the switch S₂ may be closed. This may cause the capacitance Ci to fully charge and the capacitance C₂ to fully discharge.

[0055] At the beginning of the pulse cycle, the switch Si may be closed and the switch S₂ may be opened. This may cause charge to transfer from the capacitance Ci to the capacitance C₂. During this transfer, the current through the tank circuit may rise and fall in approximately a sinusoidal manner.

[0056] This current may cause the diode D to be forward-biased as it travels through it. During this process, charge may be stored in the depletion layer of the diode D.

[0057] At the end of the half-cycle, switch S₂ may be closed. During the next half-cycle, the current flow may reverse in direction, causing the diode D to be reverse-biased. During the first part of the second half-cycle, current may still flow through the diode D while charge in its depletion layer is being depleted. Once the charge is depleted, the current through the diode D stops, causing the diode to appear as an open switch. This may cause the current through the inductance L₂ to commute from the diode D to the load R|_. The diode D may thus be configured to act as an opening switch, interrupting the current in the inductance L₂ and commuting it into the load R|_.

[0058] Current may now travel through the load R|_ until the energy stored in the tank circuit consisting of the capacitance C₂ and the inductance L₂ depletes, thus delivering a pulse into the load R_L.

[0059] This pulse generator included a current limiting resistor, R_CL configured to limit damage to the pulse generator. The value of this resistor was about 1 ohm. The pulse generator further included a terminating resistance, RT in parallel with the diode, wherein the terminating resistance was configured to protect the output stage of the pulse generator. The value of this resistor was about 1 00 ohms.

DM US 49824881-1.064693.0293 - 1 2 - [0060] The pulse generator disclosed above provided at least one electrical pulse with a duration varying in the range of about 7 ns at FWHM to about 20 ns at FWHM. In one example, a pulse with duration of about 20 ns at FWHM was generated. The characteristics of this pulse were recorded by an oscilloscope manufactured by Tektronix (Beaverton, OR) with a model number of DPO4104. As shown in FIG. 3, this pulse had pulse duration of about 20 ns at FWHM and a peak amplitude of about 8.00 kV.

[0061] The pulse generator disclosed above provided at least one electrical pulse with duration of about 14 ns at FHWM. Each pulse with a duration of about 14 ns at FHWM contained significant frequency components centered at about 71 .4 megahertz (MHz). Each such pulse had peak amplitude of about 7.0 kilovolts (kV). These pulses were generated with a frequency of about 50 pulses per second. The electric field was expected to be nominally in the range of 20 kilovolts/centimeter (kV/cm) to 40 kV/cm between the delivery electrode and each of the ground electrodes at the peak amplitude of about 7.0 kV.

[0062] Values of the pulse durations and the peak amplitudes disclosed in this document were average values unless specifically indicated. These pulse durations and the peak amplitudes may vary with a standard deviation of 10% of their average values. For example, the pulse duration of about 14 ns at FWHM may be an average of pulse durations that vary within the range of 12.60 ns and 15.40 ns, or it is 14.00 ± 1 .40 ns. Similarly, the peak amplitude of about 7.00 kV may be an average of the peak amplitudes that vary within the range of 6.30 kV and 7.70 KV, or it is 7.00 ± 0.70 kV.

[0063] Electrical power delivered by the applicator tip at the peak of the pulse,

Ppeak IS

[0065] where, V_peak is peak amplitude of electrical potential. R|_ was fixed at about 100 ohms when the pulse generator was configured. That is, the lesion resistance was expected to be about 100 ohms.

[0066] And, the electrical energy delivered by the applicator tip per pulse, E_p is:

[0067] E p - (2 X Ppeak X tFHWM) 3

[0068] where, t_FHWM is the pulse duration at FWHM.

DM US 49824881-1.064693.0293 - 13 - [0069] Then, for RL of about 100 ohms and Vpeak of about 7.00 kV, the total energy delivered to the tissue per pulse was calculated to be about 2.29 millijoules (mJ) for the pulse duration of about 7 ns at FWHM, about 4.57 mJ for the pulse duration of about 14 ns at FWHM, or about 5.88 mJ for the pulse duration of about 18 ns at FWHM. For RL of about 100 ohms and Vpeak of about 5.5 kV, the total energy delivered to the tissue per pulse was calculated to be about 2.82 mJ for the pulse duration of about 14 ns at FWHM.

EXAMPLE 2. APPLICATION OF NANOSECOND ELECTRICAL PULSES TO SKIN

LESIONS

[0070] In Example 2, the lesions, may be treated by using the nanopulse generator and the insulated applicator tip disclosed in Example 1 .

[0071 ] To avoid formation of air pockets between the electrodes, both the lesion and the electrodes may be covered with Aquasonic 100 ultrasound transmission gel (Parker Laboratories Inc., Fairfield, New Jersey, USA). Electrical pulses with varying duration, amplitude and number may be delivered to the skin lesion to determine effects of these pulse parameters on lesion treatment.

[0072] Lesion size may be measured before each treatment and one week after the treatment by using a vernier caliper. The highest elevation of the lesion as measured from the healthy skin surface is recorded as the lesion height. The longest length of the lesion as measured parallel to the healthy skin surface is recorded as the lesion length.

[0073] The widest size perpendicular to the lesion length is recorded as the lesion width. The lesion volume, L_v is then calculated by using the following equation:

[0074] Lv = 0.625 x L_L x L_w x L_H

[0075] where L_L is the lesion length, L_w is the lesion width and L_H is the lesion height. The percent of lesion growth or shrinkage T_c is:

[0076] Lc = 100 X (L after - Lv.before ) / Lv.before

[0077] where L_v,_after is the lesion volume measured one week after the treatment and L_v,before is the lesion volume measured before the treatment.

DM US 49824881-1.064693.0293 - 14 - [0078] The pulse duration at FWHM, the pulse amplitude, and the number of pulses per application is set on the pulse generator. Then, the electrodes are brought into contact with the lesion and the electrical pulses are applied. More than one application may be used to cover entire surface of the lesion.

[0079] The total electrical energy delivered by the applicator tip per treatment, E_T is:

[0081 ] where N_P is the number of pulses per application and A_N is number of applications per lesion. Electrical energy delivered per volume of lesion, E_v is:

[0082] Ev = E_T / l-V, before

EXAMPLE 3. N UMERICAL MODELING OF PENETRATION OF ELECTRICAL FIELD INTO SKIN

[0083] In this example, penetration depth of the electrical field into a healthy human skin is determined by solving Maxwell equations using a numerical modeling software, COMSOL (Stockholm, Sweden). For this modeling, following parameters were used.

[0084] Configuration of the applicator tip used in the simulations is shown in FIG. 5. The diameter of the delivery electrode was about 4 millimeters (mm). The inner diameter of the ground electrode was about 8 mm and its outer diameter was about 8.6 mm. Both the delivery electrode and the ground electrode were protruded from the flat surface of the distal end of the applicator tip. The protrusion length was about 0.05 mm for both the delivery electrode and the ground electrode. The insulating material was Teflon. Material of the delivery electrode and the ground electrode was AISI 4340 grade steel. This steel had the relative permittivity of 1 and the electrical conductivity of 4 x 10⁶ Siemens per meter (S/m).

[0085] The duration of the electrical pulse was about 20 ns at FHWM. Peak to peak interval between each pulse was about 0.01 second. These pulses contained significant frequency components centered at about 40 megahertz (MHz).

DM US 49824881-1.064693.0293 - 15 - [0086] In this modeling, the entire surface of the distal end of the applicator tip was in full contact with the surface of the healthy human skin. The dielectric properties of the healthy human skin was disclosed by Huclova et al. in a publication "Modeling and Validation of Dielectric Properties of Human Skin in the MHz Region Focusing on Skin Layer Morphology and Material Composition" J. Phys. D: Appl. Phys. 45 (2012) p1 -17. The entire content of this publication is incorporated herein by reference. The dielectric parameters disclosed for electrode sensor Ei in the FIG. 7 of this publication were used in the numerical modeling. According to this publication, at 40 MHz, the effective relative permittivity of the skin is 50 and effective electrical conductivity is 0.25 S/m.

[0087] Results of this modeling, based on these dielectric parameters, were graphically shown in FIGs. 6-13.

[0088] At the electric field of about 10 kV/cm formed by a pulse at the peak amplitude of about 7.0 kV, the penetration depth of this electric field in the tissue from the radial center of the delivery electrode at the skin surface is about 2.62 mm, as shown in FIG. 6. This electric field penetration depth decreases with the increasing electric field, from about 2.62 mm at about 10 kV/cm to about 0.66 mm at about 25 kV/cm, as shown in FIGs. 6-9.

[0089] The electric field penetration depth increases with the increasing peak pulse amplitude, as shown in FIG. 10. These modeling results may indicate that when the lesion depth is longer than the penetration depth of the electric field, it may be necessary to increase the peak pulse amplitude to provide required electric field to whole lesion to thereby treat the particular lesion.

[0090] The isoline for the electric field of about 10 kV/cm extends from the delivery electrode to the ground electrode's outer diameter covering all skin surface that is touching the applicator tip. At the higher electric fields, for example at about 20 kV/cm and about 25 kV/cm, there are "holes" in the electric field isolines, as shown in FIG. 8-9. In such cases, it may be necessary to provide multiple applications at different positions at the surface of the lesion to cover the whole lesion to provide necessary treatment to the particular lesion. Also, whole lesion surface may also be covered by increasing the peak pulse amplitude as shown in FIGs. 9 and 11 -13.

DM US 49824881-1.064693.0293 - 16 - [0091] The components, steps, features, objects, benefits and advantages which have been discussed are merely illustrative. None of them, nor the discussions relating to them, are intended to limit the scope of protection in any way. Numerous other embodiments are also contemplated. These include embodiments which have fewer, additional, and/or different components, steps, features, objects, benefits and advantages. These also include embodiments in which the components and/or steps are arranged and/or ordered differently.

[0092] Unless otherwise stated, all measurements, values, ratings, positions, magnitudes, sizes, and other specifications which are set forth in this specification, including in the claims which follow, are approximate, not exact. They are intended to have a reasonable range which is consistent with the functions to which they relate and with what is customary in the art to which they pertain.

[0093] All articles, patents, patent applications, and other publications which have been cited in this disclosure are hereby incorporated herein by reference.

[0094] Nothing which has been stated or illustrated is intended or should be interpreted to cause a dedication of any component, step, feature, object, benefit, advantage, or equivalent to the public, regardless of whether it is recited in the claims.

DM US 49824881-1.064693.0293 - 17 -

Claims

CLAIMS We claim:

1 . A system for delivery of electrical pulses to tissue comprising:

a pulse delivery device comprising at least one delivery electrode, at least one ground electrode, and electrical insulation between the at least one delivery electrode and the at least one ground electrode, wherein the at least one delivery electrode, the at least one ground electrode, and the electrical insulation each having a distal end that collectively form a substantially smooth surface that will not penetrate the tissue when pressed against the tissue with pressure sufficient to form an electrical connection between the tissue and the distal ends of the at least one delivery electrode and the at least one ground electrode; and

a pulse generator connected to the delivery and ground electrodes that is configured to generate at least one pulse that has a duration of no longer than 1 ,000 nanoseconds at full-width-at-half-maximum.

2. The system of claim 1 , wherein the substantially smooth surface is a substantially flat surface.

3. The system of claim 1 , wherein the duration of the at least one pulse is no longer than 100 nanoseconds at the full-width-at-half-maximum.

4. The system of claim 3, wherein the duration of the at least one electrical pulse at the full-width-half-maximum is in the range of 1 nanosecond to 100 nanoseconds.

5. The system of claim 4, wherein the duration of the at least one electrical pulse at the full-width-half-maximum is in the range of 1 nanosecond to 30 nanoseconds.

6. The system of claim 1 , wherein the pulse generator generates at least one pulse with an amplitude of at least 1 kV when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection.

7. The system of claim 6, wherein the pulse generator generates at least one pulse with an amplitude of at least 10 kV when the at least one

DM US ₄982₄881-1.06₄693.0293 - 18 - delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection.

8. The system of claim 7, wherein the pulse generator generates at least one pulse with an amplitude of at least 20 kV when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection.

9. The system of claim 1 , wherein the system is configured to form an electric field of at least 10 kV/cm at the peak amplitude of the pulse at a depth of about 0.5 mm below the skin surface when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection.

10. The system of claim 1 , wherein the system is configured to form an electric field of at least 20 kV/cm at the peak amplitude of the pulse at a depth of about 0.5 mm below the skin surface when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection.

1 1 . The system of claim 1 , wherein the system is configured to form an electric field of at least 20 kV/cm at the peak amplitude of the pulse at a depth of about 2 mm below the skin surface when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection.

12. The system of claim 1 , wherein the system is configured to form an electric field of at least 20 kV/cm at the peak amplitude of the pulse at a depth of about 4 mm below the skin surface when the at least one delivery electrode and the at least one ground electrode are pressed against the tissue with pressure sufficient to form an electrical connection.

13. A method of treating a skin lesion on a mammal comprising:

applying electrical energy to the skin lesion in the form of at least one electrical pulse generated by using the system of claim 1 , wherein the skin lesion comprises malignancies, precancerous lesions, human papilloma virus (HPV) infected cells, immune-related conditions,

DM US ₄982₄881-1.06₄693.0293 - 19 - seborrheic keratosis, acrocordon, aged skin, wrinkled skin, damaged skin, or combinations thereof.

14. The method of claim 13, wherein the skin lesion comprises basal cell carcinoma, squamous cell carcinoma, actinic keratosis, warts, or combinations thereof.

15. The method of claim 13, wherein the skin lesion comprises common warts.

16. The method of claim 13, wherein the skin lesion comprises actinic keratosis.

17. The method of claim 13, wherein the applied electrical energy is sufficient to reduce volume of the skin lesion by at least 30% within eight days after the treatment.

18. The method of claim 13, wherein the applied electrical energy is sufficient to reduce the skin lesion volume within eight days after the treatment for at least 40% of cases.

19. The method of claim 13, wherein the applied electrical energy is sufficient to reduce the skin lesion volume within eight days after the treatment for at least 80% of cases.

20. The method of claim 13, wherein the applied electrical energy is at least 65.0 mJ per mm³ of the skin lesion.

21 . The method of claim 13, wherein the applied electrical energy is at least 260.0 mJ per mm³ of the skin lesion.

22. The method of claim 13, wherein the applied electrical energy is at least 520.0 mJ per mm³ of the skin lesion.

DM US 49824881-1.064693.0293 - 20 -