WO2005122934A1

WO2005122934A1 - Electrosurgical apparatus

Info

Publication number: WO2005122934A1
Application number: PCT/IT2004/000353
Authority: WO
Inventors: Aldo Mauti; Paolo Mauti; Adriano De Majo; Maurizio Mattei; Piero Rossi; Valentino Quattrini
Original assignee: Consorzio I.P.O.Te.S.I; Led S.P.A.
Priority date: 2004-06-21
Filing date: 2004-06-21
Publication date: 2005-12-29

Abstract

Electrosurgical apparatus (1) used for the thermocoagulation of a hepatic tumor tissue, comprising an electrosurgical current generator (10), operatively connected to one or more pairs of electrodes (31, 32) so as to attain a bipolar thermocoagulation mode; and means (40, 200) for assessing the impedance phase of the tissue comprised between the electrodes of said or each pair.

Description

ELECTROSURGICA APPARATUS

Description

The present invention relates to an electrosurgical apparatus apt to be used for a thermal treatment, and in particular for the thermocoagulation or thermoablation of tumor tissues, and especially of hepatic tissues.

The invention further relates to a method for assessing the level of tissue thermocoagulation or thermoablation reached in an electrosurgical operation conducted in a bipolar mode.

Nowadays, the progress of the surgical technique and of anesthesia and the knowledge of the hepatic anatomy and physiopathology allow a resective surgery of the liver with an acceptable mortality and morbidity.

Technology has provided the surgeon with several devices for transecting the hepatic parenchyma (e.g. ultrasonic, water-jet, radio frequency and irrigation dissectors) and for improving the quality of the hepatic cut itself (e.g. Argon coagulator, clips and sutures, topical hemostatic agents, fibrin glue, laser). Nevertheless, to date hepatic resection remains an important deed, so much so that it is taken over by dedicated centers. The most significant complications of the hepatic resections are: post-operative bleeding, biliary leakage and hepatic insufficiency. Perioperatory hemormaging is an essential prognostic factor conditioning mortality and morbidity.

Therefore, hepatic surgery provides for some mode of vascular control that, as it is known to those skilled in the art, may span from the mere Pringle maneuver (clamping of the hepatic peduncle) to the complex and technically difficult intermittent total vascular exclusion (Pringle and suprahepatic veins, without interruption of the caval flow) and total vascular exclusion (clamping of the peduncle and of the sub- and suprahepatic caval vein).

There are several kinds of hepatectomy, classifiable according to the importance of the resection and to the surgical technique. The surgeon should be capable of selecting among all the options, so as to carry out the hepatectomy best suited to the lesion to be treated and to the quality of the residual parenchyma. Ideally, it would be advisable to have a resection without blood losses, without vascular exclusion (so as not to injure the hepatic parenchyma, and avoiding the risk linked to the isolation of the suprahepatic veins) and leaving a cut with a good hemostasis, without eschars and without secretions or bile losses.

To date, electrosurgery is also used for the resection of hepatic tumor tissues. In fact, such a resection, commonly referred to with the term 'hepatectomy', is one of the fundamental steps in the treatment of this kind of neoplasms.

In agreement with the foregoing, one of the fundamental problems of hepatic resection is to avoid hemorrhaging and bile losses, which may negatively affect the postoperative prognosis and morbidity, and to ensure an adequate coagulative necrosis of the smaller blood and bile vessels in the region concerned by the resection itself. However, this need has to be conciled with the need for an adequate blood perfusion of the organ during the surgical operation, so as to avoid undesired permanent injuries.

As a partial answer to said needs, Habib ("New technique for liver resection using heat coagulative necrosis", Annals of Surgery, Vol.236(5), November 2002, pp. 560-563) first described in 2002 an innovative technique envisaging the use of monopolar RF energy to carry out 'bloodless' minor hepatic resections without using sutures, clips or glue. Such a technique provides the coagulation by a cooled monopolar electrode of the perilesional hepatic tissue, at about 2 cm from the nodule. The subsequent section, with a blade scalpel, will fall halfway between the nodule and the coagulative necrosis line. The author surmises its application in major hepatectomies.

In principle, a way to meet said needs would be that of allowing the surgeon to control, punctually and in real time, the thermocoagulation condition attained in the treated region. For this purpose, the known electrosurgical apparatuses attempt to control the entity of the electromagnetic energy transmitted to the tissue by monitoring an operative parameter like, e.g., the treatment time, the temperature of the electrode and the power outputted therefrom or the amplitude of the impedance of the biological tissue. However, the methodologies and apparatuses used up tp now to perform the thermocoagulation of hepatic tumor tissues do not allow to adequately solve the aforementioned problems, thereby exposing the patient to postoperative complications. In particular, the known apparatuses do not allow to monitor effectively and in real time the level of thermocoagulation reached by the treated tissue. Moreover, the known techniques allow in no way the surgeon to identify any possible vascular or biliary structures in the treated region. Accordingly, said apparatuses do not allow the surgeon to optimally adjust the thermocoagulation modes, and in particular the energy-outputting times required for completing the treatment and the powers involved, to the evident detriment of the accuracy and effectiveness of the surgical operation.

^■ Hence, the technical problem posed and solved by the present invention is that of providing an electrosurgical apparatus and a method for assessing the level of tissue thermal treatment, and in particular of thermocoagulation, attained, overcoming the drawbacks hereto-mentioned with reference to the known art. Such a problem is solved by an apparatus according to claim 1. According to the same inventive concept, the present invention further provides a method according to claim 29. Preferred features of the present invention are provided in the dependent claims. The present invention provides several relevant advantages. First of all, it allows detecting substantially in real time the attainment of the required coagulation or ablation condition, thereby optimizing the times, the modes and the therapeutic result of the surgical operation. Thus, useless and injuring protractions of the latter are avoided. Moreover, the invention allows detecting the presence of blood and bile vessels in the treated region. Hence, it allows to carry out an effective coagulation action on the small and medium vessels which supply the treated organ, with an optimal and timely control of the hemostasis of the small- and medium-sized vessels, thereby abating the intraoperative bleeding. In particular, the experience accumulated in treating hepatic tumors by means of resections and RFA prompted the inventors to develop an electrosurgical method carrying out, by means of electrodes in series and a bipolar current, a linear coagulative necrosis of a length such as to allow a section the hepatic parenchyma with nil or minimal intra- and post- operatory blood loss and without biliary fistulas. Other advantages, features and the modes of employ of the present invention will be made apparent in the following detailed description of some embodiments thereof, given by way of a non-limiting example. Reference will be made to the figures of the annexed drawings, wherein: Figure 1 shows a schematic representation of the equivalent model of cellular membrane to which the present invention refers; Figure 2 is a vector representation of the body tissue impedance; Figure 3 shows a block diagram of an embodiment of the apparatus of the invention; Figure 3A shows a schematic representation of a metering electric circuit of the apparatus of Figure 3; Figure 3B shows a schematic representation of a reference electric circuit of the apparatus of Figure 3; Figure 3C shows an exemplary representation of a graph related to the pattern of the phase of the impedance detected by the apparatus of Figure 3; Figures 4A, 4B and 4C show each a view, perspective, front and side, respectively, of an embodiment of a comb electrode useful in association with the apparatus of Figure 3; Figure 5 shows a schematic perspective view of the apparatus of Figure 3 during its use in a surgical operation; Figure 6 shows a perspective view of the comb electrode of Figures 4A-4C during its use in a surgical operation; and Figure 7 shows a perspective view of a variant embodiment of the electrode of Figures 4A- 4C.

Prior to describing in detail a preferred embodiment of the invention, it is useful to recall some basic principles of cellular modeling useful to an understanding of the invention itself.

The equivalent model of cellular membrane of a biologic tissue adopted in the present invention is schematized in Figure 1. According to such a model, the cellular impedance can be assimilated to that associated with the connection in parallel of a resistor R and of a capacitor C. Such an impedance Z is defined by the known relation: Z = R - jX_c, wherein X_c designates the capacitive reactance, with x _c , f being the supply frequency. ^c //

As it is known to a person skilled in the art, the reactance X_c is a measure of the capacity of the volume of the cellular membrane and an indirect measure of intracellular volume.

From Figure 2, it also related to a well-known vector scheme, it is inferred that the phase φ of the impedance Z is expressible with the formula: (X. φ = arctg R

In light of the above, a high phase φ denotes a high capacitive reactance, thereby indicating that the cell is intact. On the contrary, a low phase φ denotes a small capacitive reactance, thereby indicating cellular necrosis. As it will be illustrated in greater detail later on, the present invention is actually based on the observation that the phase of the cellular impedance, and therefore of the tissue impedance, is directly correlated to the level of cellular necrosis of the tissue itself.

Referring initially to Figure 3, an electrosurgical apparatus according to the invention is globally denoted by 1.

Apparatus 1 comprises a main electrosurgical current generator 10, working in the field of radio frequencies (RF field), and preferably at about 500 kHz.

The generator 10 is apt to induce the flowing of an electrosurgical current through two or more electrodes according to a bipolar thermocoagulation mode. For this purpose, the generator 10 is connected to a plurality of electrodes, namely to six electrodes designated by the reference numerals 31 to 36, by connecting means generally indicated by 17. Therefore, in the present embodiment it is provided that the generator 10 has six electrical connections, indicated by the reference numerals 21 to 26, respectively, each afferent to a respective electrode 31-36. As it will be illustrated in greater detail later on, in the present embodiment it is provided the electrodes 31-36 be arranged aligned, and that generator 10, through the connecting means 17, be apt to supply pairs of adjacent electrodes in a bipolar mode.

The connecting means 17 provides each connection 21-26 with a breaker, or switch, 11-16, apt to interrupt/make the connection between the generator 10 and the respective electrode 31-36. The switches 11-16 of the means 17 are controlled by a central control unit 200 according to modes that will be detailed later on.

The hereto-introduced components, i.e. the main electrosurgical generator 10, the electrodes 31-36 and the related connections form an operating unit of the apparatus 1. Moreover, with said operating unit there is associated phase assessing means, generally indicated by 40 and described in the following, for assessing the phase of tissue impedance that sets up between each pair of adjacent electrodes. For brevity's sake, said means 40 will hereinafter be referred to as impedance assessing means.

Both the operating unit and the assessing means 40 are controlled by said central control unit 200. ln order to assess the impedance phase of the tissue comprised between a pair of adjacent electrodes, the means 40 is apt to carry out a comparative analysis between a first signal outputted from said electrodes and a second reference signal generated internally to the means 40 itself. For this purpose, the impedance assessing means 40 comprises an auxiliary generator 50, operating at a 50 kHz frequency and having a first outlet 51 and a second outlet 52.

The first outlet 51 is connected, via a known current generator, to a measurement circuit, generally designated by 400 and schematically depicted also in Figure 3A. This latter figure refers, by way of example, to the first and second electrode 31 and 32. The measurement circuit 400 allows detecting the impedance between each pair of adjacent electrodes, across the auxiliary generator 50. In particular, this circuit comprises a first electrical connection 41 , apt to connect the first outlet 51 of the auxiliary generator 50 to an electrode selected among the second, fourth and sixth electrode, 32, 34 and 36, respectively. The circuit 400 further comprises a second electrical connection 42, apt to selectively set an electrode, selected among the first, third and fifth electrode, 31, 33 and 35 respectively, at a reference potential 43, e.g. a floating potential or a zero potential.

Said selective connections between the first outlet 51 of the auxiliary generator 50 and one of said electrodes 32, 34 and 36, and between the reference potential 43 and an electrode, among said electrodes 31, 33 and 35, adjacent to that currently connected to the first outlet 51 , are made by means of a switch 60 controlled by the central unit 200.

The measurement circuit 400 is then closed within first phase detecting means 91, containing therein an element at said reference potential 43.

The second outlet 52 is instead connected, always via a known current generator, to a reference circuit, generally designated by 401 and schematically depicted also in Figure 3B. The reference circuit 401 comprises a resistive load 53, interposed between the second outlet 52 and a zero potential 54 or anyhow a possibly floating reference potential 54, and is closed within second phase detecting means 92, containing therein an element at said zero or reference potential 54.

Of course, the potentials 43 and 54 may be equal. Hence, the first phase detecting means 91 is inputted the current l_M flowing in the measurement circuit 400, and therefore the current crossing a patient's body tissue between the pair of adjacent electrodes that, due to the action of the switch 60, currently take part in the measurement circuit itself. The second phase detecting means 92 is instead inputted the current l_R that sets up in the reference circuit 401. Each of the phase detecting means 91, 92 is apt to detect the passage of the inputted current signal for a reference value, typically zero. As schematically indicated in Figure 3, each of such means 91 , 92 outputs a double square wave signal defining just the instants of transit of the respective input signal for said reference value.

The impedance assessing means 40 further comprises first comparing means 100, that is inputted the signals, 910 and 920, respectively, outputted by the phase detecting means 91 and 92. The comparing means 100 outputs a signal 101, e.g. a square wave signal, of an amplitude proportional to the time difference in the crossing of the reference value between the two input signals 910 and 920. Hence, the means 100 acts as detector of the phase delay between the input signals. Typically, the current signals in the measurement circuit 400 and in the reference circuit 401 are sinusoidal signals. Accordingly, the first comparing means 100 is inputted signals 910 and 920 having a superior half-wave and an inferior half-wave, i.e. typically a positive half- wave and a negative half-wave, and it outputs a sequence of positive square half-waves. In order to ensure a greater reliability and repeatability of operation, with the means 100 there is preferably associated a wavefront selector 110, which is inputted the signal 101 generated by the means 100 and which selects only the wavefronts corresponding to the positive (or negative) half-waves of the signals 910 and 920.

Then, the signal 111 outputted by selector 110 is inputted to second comparing means 130, which iteratively compares it to a reference signal generated by a signal generator 120, and in particular a delay signal generator 120, so as to attain, by subsequent approximations (put and take), a measure of the wave amplitude of the signal 111 itself and therefore of the phase delay between the current l_M flowing in the measurement circuit 400 and that l_R flowing in the reference circuit 401.

Preferably, the apparatus 1 also comprises an interactive terminal 8, to allow an operator to set the working parameters of the apparatus and/or to control specific functions thereof, optionally associated with a display 9, e.g. a monitor, onto which the data related to the treatment progression can be displayed.

Preferably, apparatus 1 also comprises a remote control device 80, e.g. of an infrared kind, apt to allow the operator, e.g. the surgeon him/herself, to activate or anyhow control specific functionalities of the apparatus 1 with no need to move away from the surgical table. Therefore, the remote control device 80 is apt to interact with said central control unit 200.

As mentioned above, the central control unit 200 is connected to the various components of apparatus 1 hereto-described, and it is apt to control and command them by means of known-type signal transmitting/receiving means. Unit 200 further incorporates additional processing means, which will be detailed with reference to the operation modes of the apparatus 1 , apt to determine, on the basis of the impedance assessments provided by the means 40, the progress level of tissue thermocoagulation and the possible presence of any blood or biliary vessels between the electrodes considered.

A preferred embodiment of the electrodes 31-36 is shown in Figures 4A - 4C. According to said embodiment, the electrodes 31-36 are arranged in a line and connected to a common support or handle 37. The latter has a central hollow 370 having an ellipsoidal contour, apt to facilitate its gripping, handling and therefore its positioning by the surgeon or by another operator. Hence, the arrangement described implements a device, generally indicated by 30, usually called 'comb electrode' and in which the electrodes 31-36 are substantially needle-shaped and form indeed the teeth of the comb.

One end 38 of the handle 37 receives the leads for the connection of the electrodes 31-36 to the electrosurgical generator 10 and to the switch 60, bundled within an insulating cable. Preferably, each electrode 31-36 has an anti-stick coating apt to avoid the sticking of the electrodes themselves to the tissue, so that their extraction be easier and entail no hazardous tearing of the tissue.

Preferably, such coating comprises a plurality of overlapped and alternate layers, preferably twelve hundred, alternately of Niobium nitride and Chromium nitride or of materials equivalent thereto.

According to a variant embodiment, the comb electrode can have a fume suction system.

All the elements of the apparatus 1 described hereto can be obtained with hardware and/or software components known to a person skilled in the art, and therefore a further description thereof will be omitted.

The operation modes of the apparatus 1 will be now described with reference to Figures 3, 5 and 6.

First of all, as it is shown in Figures 5 and 6, at the carrying out of the desired thermocoagulation the comb electrode 30 is grabbed at the handle 37 and inserted in the tissue concerned. In the present applicative example, it is provided that the apparatus 1 is used in a hepatic resection surgery, in the context of the treatment of a primitive or secondary tumor.

When the switches 11-16 are closed, the main electrosurgical generator 10 supplies the electrodes 31-36 in a bipolar mode, so that between each pair of adjacent electrodes there is induced the flowing of an electrosurgical current apt to generate a thermocoagulation of the tissue interposed between the electrodes themselves. More precisely, at the start of the treatment a thermocoagulation current sets up above all between the electrodes arranged at the opposite ends of the comb 30, i.e. the first electrode 31 and the sixth electrode 36. Subsequently, as tissue thermocoagulation is generated and therefore the impedance between the electrodes varies, substantial thermocoagulation bipolar currents set up between pairs of adjacent electrodes.

In the present embodiment, it is provided that the central control unit 200 be programmed so as to automatically carry out, at predetermined time intervals, a check about the impedance phase existing between pairs of adjacent electrodes by the impedance assessing means 40. Always in the present embodiment, it is also provided that an operator, by the interface means 8 and/or the remote control device 80, can command the carrying out of said check at will. On request by the operator, such a check may be provided in combination with or alternatively to the automatic checks carried out by the control unit 200.

As mentioned above, the check of the tissue impedance phase provides the activation of the impedance assessing means 40. Therefore, when the control unit 200 commands the carrying out of said phase check, switch 60 closes the contacts related to the first pair of adjacent electrodes 31-32. Thus, according to the configuration of Figure 3, the first electrode 31 is brought to the reference potential 43 and the second electrode is instead connected to the first outlet 51 of the auxiliary generator 50. Concurrently, the latter generates a sinusoidal pulse of voltage v at 50 kHz, thereby inducing in the measurement circuit 400 - formed as just described- a measurement AC current l_M, for which the equation V = zi_M applies. The measurement current l_M is detected as an input by the first phase detecting means 91.

Likewise, the current l_R flowing in the reference circuit is detected as an input by the second phase detecting means 92.

Then, the two signals l_M and l_R are processed by the first comparing means 100, by the selector 110 and by the second comparing means 130 according to the above-illustrated modes.

In particular, a signal 111 is obtained, which is outputted by the selector 110 and which has a time pattern expressing the delay carried by the wave 910 with respect to the other wave 920. Such a delay, assessed by the second comparing means 130, is directly linkable to the phase difference between the reference current l_R and the measurement current l_M, and therefore to the impedance phase of the tissue comprised between the pair of adjacent electrodes considered.

The pattern of said phase as a function of the treatment time is shown, schematically and by way of example, in the graph of Figure 3C. Said graph evidently refers to subsequent phase detections, that may be carried out sequentially or at regular time intervals. As it is evident from said graph, after a first descent slope D such an impedance phase tends to stabilize at a steady value substantially equal or near to zero.

This is due to the fact that, as the treatment goes on, the cellular necrosis in the tissue between the two electrodes increases and the capacitive reactance X_c tends to zero. Accordingly, also the impedance phase φ and therefore the phase difference of the measurement current l_M with respect to the corresponding voltage (i.e. with respect to the reference signal l_R) tend to zero. Hence, a phase value equal or near to zero indicates that the thermocoagulation of the tissue comprised between the pair of electrodes concerned is complete.

It may also be that the phase tends to a steady value different from zero. This occurs when biological structures, like e.g. blood or bile vessels, are present between adjacent electrodes.

A graph such as that in Figure 3C, or a related or equivalent representation thereof, is preferably displayed on the display 9, so that the surgeon or another operator may check the progress of the surgery.

Thus, the surgeon, by visualizing the phase pattern, can verify the occurred complete thermocoagulation between the considered pair of electrodes, commanding accordingly the deactivation of one or both of said electrodes via the disconnecting of the related switch 11 and/or 12. Of course, a certain electrode placed on an intermediate position between other two adjacent electrodes, like, for example, the second electrode 32, will be disconnected by the main generator 10 only when the thermocoagulation of the tissue comprised between the electrode at issue and both the electrodes adjacent thereto is complete.

Always by said visualization, the surgeon can ascertain the presence of vessels between two adjacent electrodes and act accordingly.

Variant embodiments could provide that the control unit 200 be apt to automatically detect the stabilizing of the value of the phase, and/or that the latter be associated with alternative signaling systems apt to communicate to the surgeon the pattern of the phase at issue, the attaining of a substantially steady pattern thereof, or directly the completing of the thermocoagulation or the presence of vessels between a certain pair of electrodes.

Moreover, according to a further variant the control unit 200 could be programmed so as to automatically cause the disconnecting of one or more electrodes from the main generators 10 upon detecting that the thermocoagulation of the tissue concerned by the electrosurgical current associated with the electrode or electrodes considered is complete.

With the illustrated methodology, any impedance assessing requires very short times, e.g. in the order of 50 nanoseconds. The phase detecting hereto-described with reference to the first two electrodes 31 and 32 is then sequentially repeated for all the other pairs of adjacent electrodes 32-33, 33-34, 34-35 and 35-36. As mentioned above, the complete cycle for assessing the phase value between all pairs of electrodes may be carried out at regular time intervals, e.g. about every 3 s. Each complete cycle may require about from 10 to 15 ms. The phase values assessed at each check are stored at the level of the central unit 200, so as to plot the graph of Figure 3C for each pair of adjacent electrodes.

Of course, the apparatus 1 could also provide that more than one sequential detections are carried out between each pair of adjacent electrodes or between electrodes of a specific pair, instead of a check providing the closing of the measurement circuit sequentially on all the pairs of adjacent electrodes.

In general, it will be understood that the apparatus 1 can allow the operator to set or command in real time the check of the phase value between any electrode pair whatsoever, according to the desired assessing sequence and/or according to preset programs for activating the impedance assessing means 40. As it is schematically shown in Figure 6, with the comb electrode 30 there can be attained a linear necrosis between all the electrode pairs. Then, the surgeon may resect with a scalpel the region isolated downstream of the thermocoagulation line.

It will be understood that the invention also provides a method for assessing the level of thermal treatment, and in particular of thermocoagulation or thermoablation, of the tissue attained in an electrosurgical operation conducted in bipolar mode by means of at least one electrode pair, said method being based on the detecting of the tissue impedance phase according to the modes illustrated above.

It will presently be better appreciated that the apparatus of the invention, in particular in the hereto-described embodiment, allows treating primitive and secondary tumors, and especially the hepatic ones, carrying out rapidly and effectively sections, even regulated or atypical ones, by virtue of the opportunity of monitoring in real time the progress of the thermocoagulation and also of detecting the presence of any unforeseen structures, like, e.g., blood or bile vessels, in the region concerned by the thermocoagulation. Thus, also an optimal coagulation and charring can be attained.

Moreover, it will be understood that the present invention is susceptible of several embodiments and variants alternative to those described hereto, some of which will briefly be illustrated hereinafter merely with reference to the aspects differentiating them from the previous embodiments.

First of all, evidently the operating unit of the apparatus 1, i.e. that formed, in the embodiment described above, by the main generator 10, the electrodes and the related connections, may be of any type whatsoever, for example providing also plural different generating means, and of course any typology of electrodes whatsoever.

Moreover, according to a variant embodiment the electrodes of the apparatus may be mounted on a common support, or handle, so as to define thereamong a bidimensional thermocoagulation contour rather than a linear one. Thus, it is possible to carry out a targeted resection of an intermediate region of the concerned organ. An exemplary comb electrode of this type is shown in Figure 7. In particular, such an electrode, indicated by 300, has two parallel rows of electrodes.

Of course, in complex cases envisaging the need for removing variously extended tissue regions having more or less regular contours, during the surgical operation several electrodes can be employed in combination, for example more than one side-by-side comb electrodes so as to define a polygonal region of any shape whatsoever.

The apparatus and the method of the invention were subjected to testing, both in vivo and ex vivo, for the resection of a pig liver. The testing was conducted using an apparatus according to the invention and six associated electrodes.

For the ex vivo tests on pig liver, a system was used having three RF generators with powers for each generator comprised in the range of 10-25 W and six needle electrodes, in a linear arrangement, like in the comb electrode shown in Figures 4A - 4C. The experimental testing allowed assessing the preferable maximum distance between an electrode and the one adjacent thereto, such as to allow anyhow the attainment of a homogeneous necrosis, with a good coagulation of the small- and medium-size vessels in the organ tissue.

The tests, on average lasting about 10 min, highlighted that the preferable maximum distance between the electrodes of a system thus designed is of about 1.5 cm, for a length of the treatable section, i.e. of the performable linear resection, for each application of the comb of about 7.5 cm.

For the in vivo testing on pig liver, a comb system with six needle-shaped electrodes was used, alike that shown in Figures 4A - 4C, wherein the current was induced by a single RF generator, as in the apparatus of Figure 3.

The distance between the individual needles was set at about 6 mm, equivalent to the implementing, for each individual application of the comb, of a linear necrosis of a length equal to about 3.5 cm.

These tests were carried out to preliminarily demonstrate the reproducibility of the technique in case of an alive animal, through the carrying out of two experiments providing no postoperative stabulation of the animal.

In the case of the two tests not followed by stabulation of the animal, five atypical hepatic resections were carried out.

In two cases the system was positioned, twice consecutively, to sequentially implement a section cut length of about 7 cm.

For the remaining three hepatic resections, a section cut length of about 10 cm was implemented, thrice reiterating the system positioning.

Subsequently to each single treatment, lasting from about 7 to 16 min, the hepatectomy was completed by cold blade scalpel and an optimum control of the hemostasis on the small- and medium-caliber vessels was ascertained. Hemostatic stitches on venous vessels having a 5 mm diameter were required.

The third experimental test envisaged the implementing of an atypical hepatic resection in three consecutive applications of the comb system, for an overall length of treatment of about 35 min. The animal was stabulated for a total of nine days.

A first check was implemented via the comparative analysis of blood exams on samples collected prior to the surgical operation and after 4 days, respectively.

The optimum control of hemostasis, even mid-term, is deduced from the fact that no hemochrome variation was detected.

Moreover, after said nine days, the animal was subjected to a new surgical operation, aimed at highlighting the presence of post-treatment blood pooling, of postoperative intra- abdominal abscesses or of biliary fistulas. The outcome was negative.

The present invention has hereto been described with reference to preferred embodiments thereof. It is understood that there could be other embodiments afferent to the same inventive kernel, all falling within the protective scope of the claims set forth hereinafter.

Claims

1. An electrosurgical apparatus (1) apt to be used for the thermocoagulation or the thermoablation of a body tissue, comprising:

- electrosurgical current generating means (10), operatively connected or connectible to at least one pair of electrodes (31-32) so as to attain a bipolar mode of thermocoagulation or thermoablation; and

- phase assessing means (40), apt to assess the phase of the impedance of the tissue comprised between the electrodes of said pair.

2. The apparatus (1) according to claim 1, wherein said electrosurgical current generating means (10) is operatively connected or connectible to a plurality of pairs of electrodes (31-

36) so as to attain a bipolar mode of thermocoagulation or thermoablation between each of said pairs, and wherein said phase assessing means (40) is apt to assess the impedance phase of the tissue comprised between each pair of electrodes (31-32, 32-33) of said plurality.

3. The apparatus (1) according to claim 1 or 2, wherein said phase assessing means (40) comprises a measurement circuit (400) that includes or is apt to include the electrodes (31- 32) of said or each pair.

4. The apparatus (1) according to claims 2 and 3, wherein said measurement circuit (400) comprises switching means (60) apt to vary the pair of electrodes (31-32) included in the circuit itself.

5. The apparatus (1) according to claim 3 or 4, wherein said phase assessing means (40) comprises detection means (91) for detecting a measurement current (l_M) which sets up in said measurement circuit (400).

6. The apparatus (1) according to any one of claims 3 to 5, wherein said phase assessing means (40) comprises means (91, 92, 100, 110) for detecting the phase delay between a measurement current (l_M) which sets up in said measurement circuit (400) and a reference signal (l_R).

7. The apparatus (1) according to the preceding claim, wherein said reference signal is a current (l_R) flowing in a reference circuit (401).

8. The apparatus (1) according to the preceding claim, wherein said reference circuit (401) and said measurement circuit (400) comprise a common auxiliary generator (50).

9. The apparatus (1) according to any one of the preceding claims, wherein said phase assessing means (40) comprises an auxiliary generator (50) connected or connectible to said or each pair of electrodes (31-32).

10. The apparatus (1) according to the preceding claim, wherein said auxiliary generator (50) is selectively connectible to a plurality of pairs of electrodes (31-32, 32-33).

11. The apparatus (1) according to any one of the preceding claims, wherein said phase assessing means (40) comprises means (120, 130) for estimating the value of said phase by subsequent approximations (put and take).

12. The apparatus (1) according to any one of the preceding claims, comprising means (200) for determining when the value of the phase assessed by said phase assessing means (40) reaches a substantially steady pattern.

13. The apparatus (1) according to the preceding claim, wherein said means (200) for determining when the value of said phase attains a substantially steady pattern is apt to assess when said phase reaches a substantially nil value.

14. The apparatus (1) according to any one of the preceding claims, comprising means (200) apt to determine the level of thermocoagulation or thermoablation of the tissue comprised between the electrodes of said or each pair (31-32) depending on the phase assessment provided by said assessing means (40).

15. The apparatus (1) according to any one of the preceding claims, comprising means (11- 16, 200) apt to cause the disconnection of one or more electrodes (31, 32) from said generating means (10) depending upon the phase value provided by said assessing means (40).

16. The apparatus (1) according to any one of the preceding claims, comprising a control unit (200) apt to command the periodic assessment of said impedance phase by said phase assessing means (40).

17. The apparatus (1) according to the preceding claim when dependent from claim 2, wherein said control unit (200) is apt to command the periodic assessment of the phase by said phase assessing means (40) sequentially for each pair of electrodes (31-32) of said plurality.

18. The apparatus (1) according to any one of the preceding claims, comprising interface means (8, 9) apt to provide an operator with information on the impedance phase assessed by said assessing means (40).

19. The apparatus (1) according to the preceding claim, wherein said interface means (8, 9) is apt to signal to an operator when said phase attains a substantially steady value.

20.The apparatus (1) according to claim 18 or 19, wherein said interface means (8, 9) is apt to provide to an operator a graph representing the pattern of said phase over time.

21. The apparatus (1) according to any one of claims 18 to 20, wherein said interface means comprises a display (9).

22. The apparatus (1) according to any one of the preceding claims, comprising activating means (8, 80) controllable by an operator to activate said phase assessing means (40).

23. The apparatus (1) according to the preceding claim, wherein said activating means comprises a remote control device (80).

24. The apparatus (1) according to any one of the preceding claims, comprising a comb electrode (30).

25. The apparatus (1) according to any one of the preceding claims, which is apt to be used for the thermocoagulation or thermoablation of tumor tissues.

26. The apparatus (1) according to any one of the preceding claims, which is apt to be used for the thermocoagulation or thermoablation of hepatic tissues.

27. The apparatus (1) according to any one of the preceding claims, comprising at least one electrode (31) having an anti-stick coating.

28. The apparatus (1) according to the preceding claim, wherein said coating comprises a plurality of overlapped and alternate layers of Niobium nitride and Chromium nitride.

29. A method for assessing the level of tissue thermocoagulation or thermoablation reached in an electrosurgical operation carried out in a bipolar mode by means of at least one pair of electrodes (31-32), wherein said assessing of the level of thermocoagulation or termoablation is carried out by means of a step of assessing the impedance phase of the body tissue comprised between the electrodes of said pair.

30. The method according to the preceding claim, wherein said phase assessing step provides the use of a measurement circuit (400) comprising the electrodes of said at least one pair (31-32) and the comparison of the phase of a measurement current (I_M) flowing in said measurement circuit (400) with the phase of a reference signal (l_R).

31. The method according to the preceding claim, wherein said reference signal is a current (l_R) flowing in a reference circuit (401).

32. The method according to any one of claims 29 to 31, wherein said phase assessing step provides that the value of said phase be estimated by subsequent approximations (put and take technique).

33. The method according to any one of claims 29 to 32, wherein said phase assessing step provides the use of an auxiliary generator (50) which is selectively connected to said at least one pair of electrodes (31-32).

34. The method according to any one of claims 29 to 33, wherein said phase assessing step is apt to determine when the value of said phase reaches a substantially steady pattern.

35. The method according to the preceding claim, wherein a substantially non-nil steady value of said phase is associated with the presence of a vessel between the electrodes of said pair (31-32).

36. The method according to claim 34 or 35, wherein said phase assessing step is apt to determine when the value of said phase reaches a substantially nil pattern, and wherein said nil value of said phase is associated with the completion of the thermocoagulation or thermoablation of the tissue comprised between the electrodes of said pair (31-32).

37. The method according to any one of claims 29 to 36, wherein said phase assessing step is carried out periodically until the phase of the tissue between said at least one pair of electrodes reaches a substantially steady pattern.

38. The method according to any one of claims 29 to 37, wherein said phase assessing step is carried out sequentially for each pair of electrodes (31-32) of a plurality of pairs of electrodes (31-23, 32-33).

39. A method for the electrosurgical thermocoagulation or thermoablation of body tissues conducted in a bipolar mode by means of at least one pair of electrodes (31-32), comprising a step of assessing the level of tissue thermocoagulation or thermoablation reached between the electrodes of said at least one pair that is carried out according to the method of any one of claims 27 to 38.

40. The method according to the preceding claim, comprising a step of disconnecting one or more electrodes (31, 32) from the electrosurgical generator (10) when said impedance phase reaches a substantially nil value.

41. The method according to claim 39 or 40, wherein said tissue is a tumor tissue.

42. The method according to any one of the claims 39 to 41, wherein said tissue is an hepatic tissue.