A variable-frequency stimulator for electrosurgery includes an impedance analyzer to identify the electrical impedance of biological tissue being treated by an electrosurgical instrument, such as a laparoscope. Based on the identified tissue impedance, a controller adjusts the frequency of electrical current delivered to the electrosurgical instrument to reduce, minimize or normalize the impedance of the tissue, thereby preventing collateral damage to the tissue in and about the surgical site. Additionally, the laparoscope may be configured with multiple electrically conductive grasping arms that are used to deliver the electrical current to the surgical site. The conductive grasping arms provide multiple current paths for the electrical current to flow, thus concentrating the electrical current at the surgical site during an electrosurgical procedure. Thus, the unwanted spread of electrical current in the tissue is prevented, resulting in the reduction or prevention of collateral damage to tissue in and about the surgical site.

TECHNICAL FIELD

Generally, the present invention relates to surgical devices used to perform electrosurgery. In particular, the present invention relates to a variable-frequency stimulator used to perform electrosurgery that optimizes the frequency of applied electrical current to reduce the electrical impedance of the biological tissue being treated. More particularly, the present invention relates to a variable-frequency stimulator and laparoscope configured to deliver electrical current to biological tissue at multiple contact points to minimize the spread of electrical current through the tissue, so as to prevent collateral damage to tissue surrounding the surgical site.

BACKGROUND ART

Electrosurgery is a widely accepted technique and is used to perform a variety of manual or robot-assisted surgical procedures on biological tissue. For example, electrosurgery is used to hemostatically occlude blood vessels, as well as to perform tonsillectomies, vaginal hysterectomies, and amputation of the liver tip and splenic wedge, as well as to treat polycystic ovary syndrome, remove benign and malignant lesions of the skin, and to perform intradiscal electrothermal therapy for internal disc disruptions of the spine. However, surgeons that utilize currently available robotic and manual laparoscopic electrostimulation devices for electrosurgery are often unable to prevent collateral damage, such as the overheating, charring, and tearing of the tissue surrounding the surgical site. Collateral damage is caused by the uncontrolled spread of energy from the electrostimulation device through tissue that is located in and about the surgical site. Furthermore, the rate of collateral damage caused by laparoscopic electrosurgical stimulators due to the uncontrolled spread of electricity also tends to increase with repeated use of such electrosurgical devices. Unfortunately, such collateral damage often leads to surgical complications, increased pain and discomfort, and longer hospital stays, which increase the costs to the patient.

Although current commercially-available electrosurgical devices use a constant stimulation frequency that is between about 300 kHz to 3 MHz, for example, the biological tissue being treated by such devices has a conductivity that is dependent on the stimulation frequency used. For example, biological tissue, including kidney, liver, lung, heart, spleen, uterus, thyroid, testes, ovary, bladder, tongue, cartilage, muscle, and skin tissue all have an electrical conductivity that tends to increase with increasing stimulation frequencies. However, there are many other examples showing that the conductivity of these tissues can increase by more than two orders of magnitude over a frequency range from 10 Hz to 20 GHz. In addition, changes in electrical conductivity in biological tissue may also be caused by mechanical changes in the structure of biological tissue itself. For example, it has been shown that the electrical conductivity of porcine lung tissue has a large variation in depending on whether the lung is inflated or deflated, which is due to the significant mechanical changes of the structure of the lung during pneumoconstriction. Thus, a wide array of electrosurgical procedures can be positively impacted by providing a variable-frequency stimulator device that is able to deliver an adjustable stimulation frequency to increase the conductivity of the tissue being treated.

In addition, while electrosurgical techniques have improved due to various technological breakthroughs, including advancements in controlling the electrical current, clinically-relevant problems still exist with robotic and manual laparoscopic electrosurgical devices. Thus, surgeons still have difficulty avoiding collateral damage in and about the surgical site being treated by electrosurgical devices. As such, surgical complications from electrosurgery still frequently occur, which result in patient dissatisfaction and increased hospitalization costs, which are unwanted.

Therefore, there is a need for a variable-frequency stimulator for electrosurgery, which controls the conductivity of the biological tissue by varying a stimulation frequency. In addition, there is a need for a variable-frequency stimulator for electrosurgery that can be readily used with any commercially available robotic or manual electrosurgical device, such as a tissue dissector or laparoscope. There is also a need for a variable-frequency stimulator that provides improved electrosurgical efficacy and safety margins, and that reduces the occurrence of collateral damage to tissue surrounding the surgical site being treated. Moreover, there is a need for a laparoscope for use with a variable-frequency stimulator that is configured to concentrate the electrical current near the surface of the surgical site to prevent the uncontrolled spread of electrical current through the tissue, so as to reduce or prevent collateral damage to nearby tissue.

SUMMARY OF INVENTION

In light of the foregoing, it is a first aspect of the present invention to provide a variable-frequency stimulator for performing electrosurgery on tissue comprising a controller; a switch coupled to said controller, said switch configured to be placed into either of a first state or a second state; a surgical instrument coupled to said switch, said surgical instrument configured to contact the tissue; an impedance analyzer coupled to said controller and to said switch, said impedance analyzer configured to identify the impedance of tissue over a range of frequencies; and a frequency generator coupled to said controller and to said switch, said frequency generator configured to generate an electrical signal at a frequency greater than about 3 MHz, wherein when said switch is in said first state and said surgical instrument is in contact with the tissue, said impedance analyzer is electrically coupled to said surgical instrument to identify a frequency or range of frequencies in said frequency range that lowers the impedance and/or increases the conductivity of the tissue, and when said switch is in said second state, said frequency generator is coupled to said surgical instrument, so as to apply said electrical signal at said identified frequency or range of frequencies to the tissue.

It is another aspect of the present invention to provide a variable-frequency stimulator for performing electrosurgery on tissue comprising a controller; a switch coupled to said controller, said switch configured to be placed into either of a first state or a second state; a surgical instrument coupled to said switch, said surgical instrument configured to contact the tissue; an impedance analyzer coupled to said controller and to said switch, said impedance analyzer configured to identify the impedance of tissue over a range of frequencies; and a frequency generator coupled to said controller and to said switch, said frequency generator configured to generate an electrical signal; and wherein when said switch is in said first state and said surgical instrument is in contact with the tissue, said impedance analyzer is electrically coupled to said surgical instrument to identify the lowest impedance of the tissue that is associated with said frequency range, said impedance analyzer also identifying a test impedance in the tissue at a predetermined test frequency, said controller calculating the ratio of said test impedance to the lowest impedance associated with said frequency range to set the power level output by the frequency generator, and when said switch is in said second state, said frequency generator is coupled to said surgical instrument, so as to apply said electrical signal having a frequency that is associated with the lowest impedance and/or highest conductivity to the tissue.

It is yet another aspect of the present invention to provide a method of performing electrosurgery on tissue comprising the steps of providing a frequency generator and an impedance analyzer that are coupled to a controller, said frequency generator generating an electrical signal at a frequency greater that about 3 MHz; providing a surgical instrument that is electrically coupled to said frequency generator and said impedance analyzer; contacting the tissue with said surgical instrument; identifying the impedance of the tissue with said impedance analyzer over a range of associated frequencies; identifying a set frequency that reduces the impedance and/or increases conductivity of the tissue; adjusting the frequency of said electrical signal generated by said frequency generator to said set frequency; and applying said electrical signal to the tissue via the surgical instrument.

It is a further aspect of the present invention to provide a method of performing electrosurgery on tissue comprising the steps of providing a frequency generator and an impedance analyzer that are coupled to a controller storing a predetermined set impedance, said frequency generator generating an electrical signal; providing a surgical instrument that is electrically coupled to said frequency generator and said impedance analyzer; contacting the tissue with said surgical instrument; identifying the impedance of the tissue with said impedance analyzer over a range of associated frequencies; adjusting the frequency of said electrical signal generated by said frequency generator to obtain said set impedance; and applying said electrical signal at said frequency to the tissue via the surgical instrument.

It is another aspect of the present invention to provide a laparoscope comprising a hand grip operatively carrying a thumb trigger and a hand trigger; an elongated support shaft extending from said hand grip; a first actuation member slideably disposed within said support shaft, said first actuation member having opposed first and second ends with a cavity extending therebetween, said first end of said first actuation member attached to said hand trigger; at least two electrically-isolated grasping arms carried by said body and operatively attached with said second end of said actuation member, said at least two grasping arms configured to move between opened and closed positions; a connection interface electrically coupled to said at least two electrically-isolated grasping arms, said connection interface adapted to be connected to the electrostimulator; a second actuation member slideably disposed within said cavity, said second actuation member having opposed first and second ends, said first end of said second actuation member attached to said thumb trigger; and a cutting blade attached to said second end of said second actuation member and said support shaft, said cutting blade extending at least partially between said at least two grasping arms.

Yet still another aspect of the present invention is to provide a laparoscope comprising a hand grip operatively carrying a thumb trigger and a hand trigger; an elongated support shaft extending from said hand grip; a first actuation member slideably disposed within said support shaft, said first actuation member having opposed first and second ends with a cavity extending therebetween, said first end of said first actuation member attached to said hand trigger; at least two electrically-isolated grasping arms carried by said body and operatively attached with said second end of said actuation member, said at least two grasping arms configured to move between opened and closed positions; a connection interface electrically coupled to said at least two electrically-isolated grasping arms, said connection interface adapted to be connected to the electrostimulator; a second actuation member slideably disposed within said cavity, said second actuation member having opposed first and second ends, said first end of said second actuation member attached to said thumb trigger; and a scissor assembly attached to said second end of said second actuation member and said support shaft, said scissor assembly extending at least partially between said at least two grasping arms.

Another aspect of the present invention is to provide a variable-frequency stimulator for performing electrosurgery on tissue comprising a controller; a surgical instrument coupled to said controller and adapted to contact the tissue; and a frequency generator coupled to said controller and configured to supply an electrical signal to said surgical instrument, wherein when said frequency generator is coupled to said surgical instrument, so as to apply said electrical signal at a frequency greater than about 3 MHz to the tissue, thereby reducing the impedance and/or increasing the conductivity of the tissue.

DETAILED DESCRIPTION OF THE INVENTION

A variable-frequency stimulator for electrosurgery is generally referred to by numeral100, as shown inFIG. 1of the drawings. Specifically, the variable-frequency stimulator100includes a controller110that provides the necessary hardware and/or software to carryout the functions of the variable-frequency stimulator100to be discussed. Coupled to the controller110is a stimulation frequency generator120, which includes a voltage to frequency converter130that is coupled to an RF (radio frequency) amplifier140. The voltage to frequency converter130is configured to convert a voltage signal received from the controller110into a signal having a predetermined frequency. For example, the voltage to frequency converter130may be configured to generate electrical signals having a variable frequency, such that a plurality of signals having different frequencies are generated over a frequency range. Alternatively, the frequency converter130may be configured to generate one signal at a fixed or discrete frequency, which does not vary over a range. For example, the voltage to frequency converter130may be configured to generate electrical signals at frequencies ranging between about 500 kHz to 250 MHz; ranging from about 3 MHz to 30 MHz, as well as ranging from about 500 kHz-20 GHz, although any other suitable frequency range may be used. Furthermore, it is contemplated that the voltage to frequency converter130may also be configured to generate electrical signals at a frequency range of any suitable increment or size. That is, the voltage to frequency converter130may generate signals over a range having a lower limit frequency of about 4 MHz to an upper limit frequency of any desired value (at any incremental divisions thereof), including but not limited to the upper limit frequencies of 5 MHz, 6 MHz, 7 MHz, 8 MHz, etc. . . . . Furthermore, the signals generated by the voltage to frequency converter130having at a single frequency may utilize any desired frequency (at any incremental division thereof), such as frequencies of about 4 MHz and above for example. For example, frequencies of 5 MHz, 6 MHz, 7 MHz, 8 MHz, 9 MHz, etc. may be used. The RF amplifier140, also coupled to the controller110, is configured to increase the amplitude of the electrical signal generated by the voltage to frequency converter130to a level preprogrammed at the controller110or manually set via a setting button142. The electrical signal output by the RF amplifier140having the desired frequency and amplitude characteristics is delivered to a switch175that is electrically coupled to a surgical instrument suitable for performing electrosurgery, such as a surgical instrument180. The surgical instrument180, which will be discussed in detail below, is a mechanical device, such as a laparoscope or tissue dissector for example, that is configured to perform various manipulations, including electrosurgical manipulations to biologic tissue, including but not limited to grasping, cutting, and cauterizing the tissue190. It should be appreciated by those well practiced in the art that the frequency of stimulation need not be specified by a voltage to frequency converter, but that any suitable means can be used to specify the frequency of stimulation.

The variable-frequency stimulator100also in one exemplary embodiment includes an impedance analyzer200that is coupled to the controller110and to the switch175. It should be appreciated that the switch175may comprise any suitable mechanical, electrical, or electromechanical switching device that is configured to electrically couple either the frequency generator120or the impedance analyzer200with the surgical instrument180. Specifically, the impedance analyzer200is configured to identify the impedance or electrical conductivity of the tissue190that is being treated by the surgical instrument180. As such, the impedance analyzer200is configured to generate a plurality of electrical signals each with a different frequency that are applied to the tissue190to identify the associated tissue190impedance. That is, the impedance analyzer200is configured to sweep through a range of frequencies that are applied to the tissue190when the instrument180is brought into contact with the tissue190, and each associated impedance measurement is recorded by the controller110. Furthermore, the impedance analyzer200is configured to monitor the impedance of the tissue190over any desired range of frequencies, including but not limited to a range of frequencies, such as from about 500 kHz to 250 MHz; 100 kHz to 250 MHz; 3 MHz to 30 MHz, as well as ranging from about 500 kHz-20 GHz, for example. The impedance data acquired by the impedance analyzer200is recorded or stored by controller110and is processed in a manner to be discussed to determine the particular stimulation frequency that is to be delivered from the stimulator120to the tissue190via the electrosurgical instrument180.

Because the electrical conductivity of the tissue190is highly anisotropic and decreases when coagulated, it is important to frequently analyze the impedance of the tissue190by the frequency analyzer200. Thus, by controlling the electrical impedance of the tissue190being treated by variable-frequency electrical stimulation, less collateral damage will be inadvertently imposed upon surrounding biological tissue190due to a reduction in operating temperature. This is because the power dissipated by conductive elements can be described by P=VI=I2Z=V2/Z, where P is power, V is voltage, I is electrical current, and Z is the impedance of the element.

The variable-frequency stimulator100may be powered by any suitable AC (Alternating Current) or DC (Direct Current) power source202, such as a battery or standard wall outlet that is coupled to the controller110. Furthermore, a mode-select or setting switch204may be coupled to the controller110to place the variable-frequency stimulator100into various operating states or modes to be discussed below.

In one aspect, the variable-frequency stimulator100may be configured such that the control algorithm utilized by the controller110is programmed in MATLAB/Simulink using a real-time Windows target kernel and a control loop sample frequency of 1 kHz. In addition, the controller110may include a PCI-6221 (National Instruments) data acquisition card used to sample tissue temperature, voltage, and electrical current data in a manner to be discussed. In one aspect, the PCI-6221 data acquisition card may have two analog voltage outputs, whereby the first output is sent to the voltage-to-frequency converter130that is used to convert the variable voltage command signal from MATLAB/Simulink into a variable frequency. The second analog output from the controller will be sent to the high-bandwidth voltage controlled variable gain amplifier that will be used to adjust the gain of the signal sent to an RF amplifier140and then subsequently to the tissue grasped by the instrument180. In another aspect, the impedance analyzer200may comprise an 4294A impedance analyzer, which is used to measure the electrical frequency response of the tissue190that is in contact with the electrosurgical instrument180over a broad frequency range, as previously discussed.

In addition, the variable-frequency stimulator100may also include a plurality of temperature sensors220, such as a thermocouple or thermistor, that is attached to the tissue190and that is configured to monitor the temperature of the tissue180that surrounds the surgical site in which the surgeon is using the electrosurgical instrument180. The temperature identified by the temperature sensor220is delivered to the controller110and/or to a display monitor240, such as an LCD (liquid crystal display), for example. By allowing the surgeon to monitor the temperature of the tissue190via the display240, he or she is able to determine whether tissue190that is near to the region that is being treated by the electrosurgical instrument180is exceeding a threshold temperature and is in danger of being damaged. In one aspect, the controller110may utilize the temperature of the tissue190in order to vary the duty cycle and/or the frequency of the electrical current signal that is generated by the frequency generator120. This allows the surgeon to have better control of the function of the electrical stimulation applied by the tissue dissector, in the case of coagulation or cutting of tissue for example. It is also contemplated that the output of the impedance analyzer200may be coupled to the monitor240as well, to allow the surgeon to view the impedance of the tissue190being treated.

In one aspect, the temperature sensor220used to measure the temperature of the tissue190, may comprise five FLUKE 5611A silicon-bead probe thermocouples220that are carried by a polycarbonate fixture242, as shown inFIGS. 2A-B, which includes a slot that is dimensioned to receive various end-effectors of the electrosurgical instruments180, including those discussed in detail below. Specifically, the thermocouples or temperature sensors220may be placed in the fixture242at a 1 mm distance around a mouth244, which is dimensioned to receive the surgical instrument180to measure the temperature distribution profile during the surgical procedures. The fixture242also includes a spring clip mechanism246that allows the thermocouple device220to be removeably clipped to the tissue190, such that when the tissue190is subsequently stimulated by the variable-frequency stimulator100, the nearby tissue temperature is measured by the five thermocouples220. It should also be appreciated by those well practiced in the art that the tissue temperature could be measured by any suitable sensor such as an infrared sensor.

Thus, with the components of the variable-frequency stimulator100set forth, the following discussion sets forth the operational steps carried out by the variable-frequency stimulator100during its operation. Initially, before the tissue190is grasped with the surgical instrument180, the switch175is placed in a first mode or state, where the impedance analyzer200is electrically coupled to the surgical instrument180. Specifically, the impedance measured by the impedance analyzer200across the grasping arms of the surgical instrument180before they contact the tissue190is infinite, and when the tissue190is brought into contact or grasped with the instrument180the impedance becomes finite and the impedance analyzer120sweeps through a predetermined range of frequencies, as previously discussed. In one aspect, the sweep time of the impedance analyzer200over the range of frequencies may be achieved in less than 100 ms, for example, although other sweep times may be used. The impedance analyzer200continues analyzing the impedance of the tissue190over the predetermined frequency range until the surgeon activates the electrical stimulation function of the stimulator100by placing the switch175into a second mode or state. Placing the switch175into the second mode or state disconnects the impedance analyzer200from the surgical instrument180, and connects the frequency generator120to the surgical instrument180, thereby allowing electrical signals at a range of frequencies to be delivered to the surgical site as previously discussed. The impedance of the tissue can be determined while the tissue is stimulated through the ratio of the measured voltage and current.

In another aspect, the variable-frequency stimulator100may be configured to be placed in various operating modes via the mode-select switch204. Specifically, in a first or normal mode, the variable-frequency stimulator100utilizes a control algorithm that is executed by the controller110, which is programmed to deliver electrical signals over a range of stimulation frequencies, as previously discussed, which have a constant average power that produces a lower or the lowest level of tissue impedance over a specific frequency band. This allows the electrosurgical instrument180to have a fast cutting time, while allowing the temperature of the tissue190to remain low thereby reducing burns and collateral damage to the tissue. Specifically in one aspect, the tissue impedance at a stimulation frequency of about 500 kHz is compared by the controller110to the lowest tissue impedance measured over an entire predetermined frequency range, such as from about 100 kHz to 4 MHz or from about 300 kHz to 250 MHz, as determined by the impedance analyzer200, as previously discussed. Next, the ratio of the tissue impedance at 500 kHz with respect to a lower or the lowest measured impedance is calculated by the controller110in order to reduce the power level of the electrical stimulation, which would be implemented at the frequency producing the lowest tissue impedance. The frequency of stimulation can also be chosen without use of an impedance analyzer to reduce tissue impedance or increase tissue conductivity based on the knowledge that tissue conductivity increases in general with increasing stimulation frequency, in particular with stimulation frequencies greater than 3 MHz. It should also be clear that the frequency of stimulation corresponding to a lower or the lowest level of tissue impedance can be used without any reduction in power. It should also be clear that after a stimulation frequency in the range of, for example, 3 MHz-20 GHz is used, a lower frequency of stimulation for example between 300 kHz-3 MHz could be subsequently used. It should also be clear that the frequency and/or duty cycle of stimulation can be adjusted based on tissue temperature feedback to produce lower or more desirable operating temperatures. This algorithm produces less collateral damage, necrosis and operating temperatures that are lower than that produced by currently available constant frequency stimulators that typically operate between 300 kHz and 3 MHz. The frequency of electrical stimulation that would most closely produce the desired tissue impedance or conductivity is then used with a constant average power stimulation mode each time the tissue190is subsequently grasped by the instrument180.

In a second operating mode selected by the mode-select switch204, the electrostimulator100maximizes the conductivity of the tissue190, by selecting a stimulating frequency from the range of analyzed stimulation frequencies that achieves a lower or the lowest tissue impedance, as identified by the impedance analyzer200. That is, the controller110utilizes the stimulation frequency and associated impedance data that is collected by the impedance analyzer200to control the voltage to frequency converter130and RF amplifier140of the frequency generator120, so as to generate a stimulation frequency that is applied to the tissue190that reduces or minimizes the impedance or increases or maximizes the conductivity of the tissue190. The reduction and/or minimization in impedance and/or the increase and/or maximization of conductivity is with respect to the levels of impedance and/or conductivity that can be obtained with lower frequency levels between for example 300 kHz 3 MHz. As such, the present invention is capable of lowering or reducing the impedance with respect to the impedance levels that can be obtained by commercially available devices that operate between 300 kHz-3 MHz, which is highly desirable.

In a third operating mode selected by the mode-select switch204, the controller110is configured to control the stimulating frequency such that the impedance of the grasped tissue is the same regardless of the type of tissue190being treated by the instrument180. This normalized operation of the variable-frequency electrostimulator100allows the surgeon or other operator of the device to have a consistent level of cutting and/or cauterizing control across all types of tissue. This is in contrast to the electrostimulator100operating modes previously discussed, which may vary the stimulation frequency to provide a lower or the lowest impedance depending on the type of tissue190being treated. That is, by configuring the electrostimulator100to select the necessary frequency to achieve the same level of impedance and/or conductivity independent of the type of tissue190allows the surgeon to apply a consistent ratio of current to voltage for any specific power setting used to treat the tissue190, regardless of the type of tissue or the way that the a specific type of tissue is grasped. This ensures that consistent tissue heating effects occur regardless of the tissue that is treated.

In a fourth operating mode, any number of components fromFIG. 1may be omitted and a single electrical signal having a constant or fixed frequency of stimulation, as previously discussed, can be applied to the tissue with or without any feedback controller. In this embodiment, the specific frequency of stimulation can be specified ahead of time anywhere between a range of any desired frequencies, such as for example 4 MHz 20 GHz. This can be done to reduce collateral damage, tissue temperature and burning during electrosurgery, because the tissue impedance decreases in general with increasing stimulation frequency. The tissue conductivity also increases in general with increasing stimulation frequency. These two factors significantly impact the ratio of voltage to current for any power level that is used to cut tissue which in turn impacts the tissue temperature, collateral damage and tissue burning. The reduction and/or minimization in impedance and/or the increase and/or maximization of conductivity with respect to the levels of impedance and/or conductivity that can be obtained with lower frequency levels between for example 300 kHz-3 MHz.

Thus, because most biological tissue impedances decrease with increasing stimulation frequency, control over the tissue impedance is possible through the control of the stimulation frequency via the variable-frequency stimulator100. As such, the stimulator100is configured to stimulate tissue with a frequency that reduces and/or minimizes the electrical impedance of the tissue. Hence, the stimulator100is also configured to stimulate tissue with a frequency that increases and/or maximizes the electrical conductivity of the tissue. Such reduction and/or minimization of the electrical impedance of biological tissue treated by the stimulator100is able to reduce the operating temperatures of surrounding tissue to prevent or reduce the amount of collateral damage and tissue necrosis that occurs during electrosurgical procedures. It should also be appreciated that the variable-frequency stimulator100, through control of the frequency of stimulation can also control the amount and/or rate of blood loss, tissue temperature, tissue cauterization, and tissue burning that occurs during electrosurgery, which is highly desirable.

Experimental

To evaluate the efficacy of the methods of electrical stimulation utilized by the electrostimulator100, a four component Maxwell-Wagner model of tissue300, as shown inFIG. 3was experimentally evaluated with an electrosurgical stimulator, using an electrosurgical instrument comprising bipolar laparoscope forceps. The default stimulation frequency was set at a constant 500 kHz, while a power setting of 1 W was used. Two different combinations of resistor and capacitor values were chosen to show how the constant frequency affects the voltage across the tissue model300. As shown inFIG. 4, the peak-to-peak voltage applied by the stimulator is roughly 0.6V for resistors and capacitors (R1-R2and C1-C2having an effective impedance of Z1. However, for different values of resistance and capacitance (R1-R2and C1-C2) with an effective impedance of Z2, the peak-to-peak voltage stimulator increases to roughly 3.5V, as shown inFIG. 5.

In the next evaluation, a function generator was used to stimulate the tissue model (Z2) at three different frequencies to show the advantage of using a variable stimulation frequency to allow the effective impedance of the tissue to be lowered. As shown from the stimulation frequencies at 900 kHz and 2 MHz, the voltage across the tissue model300is much larger compared to the input voltage than at the 500 kHz stimulation frequency, as shown inFIGS. 6, 7, and8. Specifically,FIG. 6shows the response of the voltage across impedance Z2with a stimulation frequency of 500 kHz;FIG. 7shows the increased amplitude in the voltage across impedance Z2when the stimulation frequency was increased to 900 kHz, even though the input amplitude is the same;FIG. 8shows the increased amplitude in the voltage across impedance Z2when the stimulation frequency is increased to 2 MHz. Thus, variation of the stimulation frequency changes the amplitude of the voltage applied across impedance Z2.

Thus, the results set forth above show that the same amount of electrical current can be driven through the biological tissue190with a lower voltage when a stimulation frequency is chosen to minimize and/or reduce the effective impedance of the tissue190. During electrosurgery, this results in lower operating temperatures, and therefore less collateral damage to surrounding tissue. Furthermore, the results above also show that for any specified electric power level, a plurality of different ratios of voltage to current can be achieved by choice of the frequency of stimulation to control the impedance of the biological tissue190. This is important because of the different tissue heating effects that occur with different ratios of voltage and current. Specifically, the temperature increase in the tissue from electrical stimulation is described by Eq. 1, where

Δ⁢⁢T=J2⁢tσ⁢⁢CP⁢d,
where J is the electric current density, t is the amount of time the tissue is stimulated, σ is the electrical conductivity; CPis the specific heat of the tissue, and d is the density of the tissue.

Therefore, when the stimulation frequency is selected to increase and/or maximize the tissue conductivity, the amount of time to cut the tissue is reduced, and the temperature of the tissue190will increase if a constant power stimulation mode is utilized. However, if the cutting time and all other parameters, except a, remain constant, a lower tissue temperature increase is achieved.

In addition, during the third mode of operation of the electrostimulator100, impedances Z1and Z2of the model300are each stimulated at different frequencies. In the first case, impedance Z1is stimulated with a peak-to-peak input of 20V and a frequency of 610 kHz, which resulted in a response of 1.5V peak-to-peak, as shown inFIG. 9. Next, impedance Z2was stimulated with the same peak-to-peak input of 20V, but at a frequency of 400 kHz, which also resulted in a response of 1.5V peak-to-peak, as shown inFIG. 10. Thus, by choosing the appropriate stimulation frequency, the tissue impedance can be changed so that the voltage/current ratio can be kept the same. Thus, the current density through the tissue will remain constant and the heating of the tissue190described by Eq. 1 will be the same regardless of the type of tissue that is stimulated.

In addition,FIGS. 11A-Cshow temperature measurements in liver, lung, and muscle tissue when stimulating frequencies of 500 kHz and 30 MHz are used, as well as the average temperature of the tissue and corresponding standard deviation. It should be noted that the 30 MHz stimulation frequency produces a lower average temperature, with all three types of tissue, as shown in the Figs. For example,FIG. 11Ashows the temperature measurements for liver tissue for 500 kHz and 30 MHz stimulation frequencies with a constant 15 W power setting, whereby the 30 MHz stimulation frequency produces a lower average tissue temperature.FIG. 11Bshows the temperature measurements for lung tissue for 500 kHz and 30 MHz stimulation frequencies with a constant 10 W power setting, whereby the 30 MHz stimulation frequency produces a lower average tissue temperature. Finally,FIG. 11Cshows the temperature measurements for muscle tissue for 500 kHz and 30 MHz simulation frequencies with a constant 15 W power setting, whereby the 30 MHz stimulation frequency produces a lower average tissue temperature. Thus, the 30 MHz stimulation frequency produced a 14%, 11%, and 15% lower average maximum tissue temperature in the respective liver, lung, and muscle tissue than the 500 kHz stimulation frequency produced.

Thus, with the discussion of the components and manner of operation of the variable-frequency stimulation device100set forth, the following discussion presents the various surgical instruments180that may be utilized with the stimulation device100. Specifically, the surgical instrument180may comprise a laparoscope400, as shown inFIGS. 12-18of the drawings. Specifically, the laparoscope400comprises an end effector410having a cutter or cutting blade412and grasping arms414A-B that are operatively attached to a hand grip420via actuation members430and432that extend through an elongated cavity434disposed in an elongated support shaft440having opposed ends433A and433B. Specifically, the actuation members430and432have respective opposed ends434A-B and436A-B, such that ends434A,436A are operatively attached to the end effector410(cutting blade412and grasping arms414A-B) and ends434B,436B are operatively attached to the handgrip420. The actuation member432slideably reciprocates within the cavity434of the support shaft440, and includes an elongated receiving cavity447in which the actuation member430slideably reciprocates. That is, the actuation member432slideably reciprocates within the cavity434of the support shaft440, while the actuation member430slideably reciprocates within the cavity447of the actuation member432. Specifically, the hand grip420, shown clearly inFIGS. 14A-D, is formed as a pair of opposed case sections450A and450B. The case sections450A-B have an opposed inner surface454and outer surface458, such that when the housing sections450A-B are attached together, a cavity460is formed therein to carry an actuation assembly462that controls the operation of the end effector410.

The hand grip420is attached to the support shaft440via a collar466. In addition, the hand grip420also includes a pair of spaced pivot shafts470and472that extend from the inner surface454of the housing section450B at a substantially right angle. A yoke member480is pivotably attached to pivot shaft470via mounting aperture481. The yoke member480includes a pivot arm482that is attached to a pair of parallel spaced yoke arms484and486, whereby a pivot aperture490is disposed in the pivot arm482, and yoke apertures494are disposed in each yoke arm484,486. It should be appreciated that the yoke member480may be formed as a single section or formed from two sections, as shown in the Figs. In addition, the spaced yoke arms484,486are configured to retain a clamp497that includes protrusions488that are received within the yoke apertures494. The clamp497is attached to an end cap498that is attached at end434B of the actuation member430. In addition, a thumb trigger504is pivotably attached to the pivot aperture490of the yoke member480by a protrusion501. Furthermore, the yoke member480is biased by a spring510that is disposed between the end cap498and the inner surface454of the rear of the hand grip450B. Thus, when the thumb trigger504is depressed from its normal resting position, the spring510is compressed and the cutting blade412attached to end434A of the actuation member430is retracted within the support shaft440, and when the thumb trigger504is released, the spring510decompresses, causing the yoke member480to pivot, such that the cutter412to extends to its normal position.

The actuation assembly462also includes a hand trigger520, as shown clearly inFIGS. 14A-D, which include a pivot aperture524that receives the protrusion472extending from the inner surface454of the case450B therein, so as to allow the hand trigger500to pivot. The hand trigger520also includes spaced plates524and526, each of which includes a receiving aperture530therein. The receiving apertures530are configured to pivotably receive protrusions534therethrough, which extends from an actuator clamp540. The actuator clamp540is configured to be attached to the end436B of an actuation member432that extends through the support shaft440.

Thus, when the hand trigger520is squeezed or pulled backward from its normal resting position, a back edge550of the hand trigger520engages the yoke members480, causing the cutter412to retract and the spring510to compress and the cutting blade412to retract, and the grasping arms414A-B attached to the end436A of the actuation member432to close. And when the hand trigger520is released, the spring510decompresses, such that the cutting blade extends forward and the grasping arms414A-B open. Thus, due to the configuration of the thumb trigger504and the hand trigger520, the cutter412and the grasping arms414A-B are able to operate independently of one another.

In addition, the hand grip420also includes an electrical connection interface560, such as a plug or port that is configured to electrically selectively couple the laparoscope end effector410to the switch175of the electrosurgical device100.

Continuing toFIGS. 15-17, the pair of elongated grasping arms414A-B of the end effector410each includes elongated apertures570, as well as a pivot aperture610and an actuation aperture614. As such, the grasping arms414A and414B are pivotably attached to respective attachment arms600and602that extend from the end433A of the support shaft440by a suitable fasteners620, such as a screw, that are received through the corresponding pivot apertures610and threadably retained in a fastener aperture624of the corresponding attachment arm600and602. That is, the grasping arm414A is pivotably attached to attachment arm600and grasping arm414B is pivotably attached to attachment arm602. In addition, dielectric bushings630are disposed between each fastener620and the inner circumference of the fastener aperture624, so as to electrically isolate each grasping arm414A and414B from each other. In addition, wires626and628are respectively coupled at one end to the grasping arms414A-B, and at another end to the connection interface560.

In order to move the grasping arms414A-B from an opened position to a closed position, the actuation member432includes pivot apertures670A-B that are disposed proximate to the end436A. Specifically, the pivot apertures670A-B of the actuation member432are attached to respective grasping arms414A-B by corresponding linkage members650A-B. That is, linkage member650A is pivotably attached between pivot aperture614of grasping arm414A and pivot aperture670A of the actuation member432, and linkage member650B is pivotably attached between pivot aperture614of grasping arm414B and pivot aperture670B of the actuation member432. As such, when the connection interface560is electrically coupled to the switch175, the variable-frequency stimulator100is electrically coupled to the grasping arms414A-B. Furthermore, to allow the grasping arms414A-B to be electrically isolated from each other, the pivot apertures670A-B of the actuation member432may be electrically isolated from the linkage arms650A-B by dielectric bushings630, or alternatively, the linkage arms650A-B may be formed from non-conductive dielectric material.

The cutting blade or cutter412provided by the laparoscope400is attached to the end434A of the actuation member430. Specifically, the cutting blade412is configured to extend within a gap or cavity680formed between the grasping arms414A-B, whereby they are closed. Furthermore, the actuation member430to which the cutter412is attached is disposed within the cavity447of the actuation member432and is configured to reciprocate back and fourth by the operation of the thumb trigger504of the hand grip420previously discussed.

Thus, when the laparoscope400is initially placed into use whereby neither the thumb trigger504nor the hand trigger520are actuated by the user, the cutting blade412is extended to is normal resting position, and the grasping arms414A-B are maintained in an opened state, as shown inFIG. 18A. When the hand trigger520is squeezed and the thumb trigger504is left in its normal resting position, the grasping arms414A-B are closed, and the cutting blade remains in its normal resting position, as shown inFIG. 18B. Alternatively, when the thumb trigger504is depressed and the hand trigger520is left in its normal position, as shown inFIG. 18C, the cutting blade412is partially or fully retracted. Finally, when both the thumb trigger504is depressed and the hand trigger520is squeezed, the cutting blade412is fully/partially retracted, and the grasping arms414A-B are closed, as shown inFIG. 18D.

In another aspect of the present invention, an alternative laparoscope400′ may comprise a scissor assembly700, as shown inFIGS. 19-24, which replaces the cutting blade412previously discussed, with regard to laparoscope400shown inFIGS. 12-18. That is, the end effector410of laparoscope400′ is structurally equivalent to that of laparoscope400except that the cutting blade412of laparoscope400has been replaced with the scissor assembly700. Specifically, the scissor assembly700includes a pair of scissor members702A-B, each having a pivot aperture710and an actuation aperture720, as shown inFIGS. 20A-B. A shaft722is disposed between attachment arms600,602and is received through the pivot apertures710of each scissor member702A-B. In addition, linkage members740and744formed of dielectric material are pivotably attached to the actuation aperture720of each respective scissor member702A-B at one end, and to pivot apertures750disposed on each side of the actuation member430at another end of the linkage members740. In another aspect, the scissor members702A and702B may be separated by a dielectric or non-conductive washer (not shown), such that the scissor members702A-B are electrically isolated from one another, so as to ensure that the grasping arms414A-B remain electrically isolated from each other.

Thus, during operation of the laparoscope400′, when it is in its normal resting position and the thumb trigger504and hand trigger520are not actuated, the grasping arms414A-B and scissor members702A-B are opened, as shown inFIGS. 21A-B. When the hand trigger520is squeezed and the thumb trigger504is not depressed, the grasping arms414A-B are closed, as shown inFIGS. 22A-B, and the scissor members702A-B remain opened and extend through the elongated apertures570of the grasping arms414A-B. Alternatively, when the thumb trigger504is depressed and the hand trigger520is not squeezed, the scissor members702A-B are closed, while the grasping arms414A-B are opened, as shown inFIGS. 23A-B. Finally, when the thumb trigger504is depressed and the hand trigger520is squeezed, the scissor members702A-B and the grasping arms414A-B are both closed, as shown inFIGS. 24A-B.

In another embodiment of the present invention a laparoscope400″, which is structurally equivalent to laparoscope400, except that end effector410has been replaced with alternative end effector820is shown inFIGS. 25-32of the drawings. Specifically, the end effector820is configured such that a plurality of spaced notches830are disposed about an outer surface822of the actuation member432, proximate to the end436A, as shown inFIG. 26. The notches830are dimensioned to receive and retain corresponding pivot tabs840therein, which include a fastener end842that is attached to an opposed pivot end844by an extension member845. As such, the fastener end842of the pivot tab840is configured to be snap-fit or frictionally-fit into corresponding pivot holders846disposed in the notches830of the actuation member432, although any other suitable pivoting means of fixation or attachment may be used. The pivot end844of each pivot tab840includes a substantially cylindrical pivot surface850that is dimensioned to be pivotably attached within an arcuate pivot retainer854provided by each grasping arm860A-D. The grasping arms860A-D each include a support arm864that extends from the arcuate pivot retainer854, and which terminates at a curved claw870. In one aspect, the curved claw870of each of the grasping arms860A-D may terminate at a point or tip872. Finally, extending at a substantially right angle from either side of an outer surface880of the grasping arm860A-D at a point proximate to the pivot retainer854are pivot pins882.

The end effector820of the laparoscope400″ also includes a substantially cylindrical collar member890, as shown inFIG. 27, having an inner surface892and an outer surface894, and that is terminated at opposed ends896and898. The collar890includes a plurality of spaced notches900that are disposed proximate to the end896of the collar890, which are dimensioned to allow the support arm864of the respective grasping arms860A-D to slide therethrough. Furthermore, the collar890is dimensioned to receive the actuation member432therein, such that the notches900of the collar890are substantially aligned with the notches830of the actuation member432, thereby aligning the grasping arms860A-D to freely move through the collar notch900. In addition, the collar890also includes retention apertures920that are disposed on either side of the notch900that are dimensioned to receive the pivot pins882of each corresponding grasping arm860A-D therein.

Disposed within aperture447of the actuation member432is the actuation member430to which the cutting blade412is attached, as previously discussed with regard to the embodiment inFIGS. 12-18.

In addition, because the laparoscope400″ includes four grasping arms860A-D, four connection wires950,952,954,956, as shown inFIG. 28, are used to connect each respective grasping arm860A-D to the connection interface560, such that suitable electric signals, as previously discussed, can be delivered to the grasping arms860A-D. Furthermore, it should be appreciated that collar890and actuation member432are electrically isolated from the grasping arms860A-D using known means, such that the grasping arms860A-D are each electrically isolated from each other. Furthermore, in one aspect, the grasping arms860A-D may be configured, such that arms860A and860C comprise positive terminals or electrodes and arms860B and860D comprise negative terminals or electrodes, however, it should be appreciated that the grasping arms860A-D may be configured to be positive or negative in any desired configuration. As such, electrical signal supplied by the frequency generator120of the variable-frequency stimulator100is able to flow in multiple paths between the various positive and negative terminals or electrodes of formed by the grasping arms860A-D, which serves to concentrate the flow of electrical current through tissue being grasped by the grasping arms860A-D. Moreover, by concentrating the flow electrical current, collateral damage, such as overheating, charring, and burning is minimized or prevented. Furthermore, more precise tissue dissection is also enabled with more concentrated current flow.

Thus, during operation of the laparoscope400″, when the laparoscope400″ is at its normal resting state, whereby the thumb trigger504and the hand trigger520are not actuated, the grasping arms860A-D are fully opened, and the cutting blade412is fully extended as shown inFIG. 29. When the thumb trigger504is depressed, and the hand trigger520is not squeezed, the cutting blade412is partially or fully retracted into the cavity447of the actuation member432, and the grasping arms860A-D are fully opened, as shown inFIG. 30. Alternatively, when the hand trigger520is squeezed, and the thumb trigger504is not depressed, the grasping arms560A-D are closed and the cutting blade412is extended, as shown inFIGS. 31A and 31B. Finally, when the thumb trigger504is depressed and the hand trigger520is squeezed, the cutting blade412is partially or fully retracted into the cavity447of the actuation member432and the grasping arms860A-D are closed, as shown inFIG. 32. Thus, the reciprocating back and forth movement of the cutting blade412and the opening and closing of the grasping arms860A-D can be independently controlled by the thumb trigger504and the hand trigger520.

It will, therefore, be appreciated that one advantage of the present invention is that a variable-frequency stimulator for electrosurgery reduces overheating, charring, and tearing of tissue. Another advantage of the present invention is that the variable-frequency stimulator for electrosurgery utilizes a stimulation signal having a constant power. Still another advantage of the present invention is that the variable-frequency stimulator for electrosurgery allows a constant amount of power to be applied independently of the type of tissue being treated. An additional advantage of the present invention is that the variable-frequency stimulator provides a laparoscope that includes multiple grasping arms that permit electrical current to flow in multiple paths between the arms, so as to reduce the temperature of the tissue surrounding the surgical site. Yet another advantage of the present invention is that the variable-frequency stimulator for electrosurgery allows for improved electrosurgery efficacy and safety margins to be attained for not only robotic-assisted applications, such as cholestectomy, fundoplications, gastric banding, hysterectomy, prostatectomy, and colectomy, but will also enable surgeons to expand the scope of the surgical procedures that are performed and enhance advanced procedures, such as esophagectomy, gastrojejunostomy, thymectomy, thoracic parasympathectomy, lobectomy, mediastinal parathyroidectomy and left pancreatic resection, for example. Still another advantage of the present invention is that a laparoscope for use with a variable-frequency stimulator for electrosurgery allows electrical current to be distributed through the tissue being treated at multiple sites, so as to allow the electrical current to be concentrated in a more localized manner to reduce heating and excessive damage of the tissue surrounding the treatment site.

Thus, it can be seen that the objects of the invention have been satisfied by the structure and its method for use presented above. While in accordance with the Patent Statutes, only the best mode and preferred embodiment has been presented and described in detail, it is to be understood that the invention is not limited thereto or thereby. Accordingly, for an appreciation of the true scope and breadth of the invention, reference should be made to the following claims.