WO2006084676A1

WO2006084676A1 - Microwave device for the ablation of tissues

Info

Publication number: WO2006084676A1
Application number: PCT/EP2006/001098
Authority: WO
Inventors: Nevio Tosoratti
Original assignee: H.S. - Hospital Service - S.P.A.
Priority date: 2005-02-11
Filing date: 2006-02-08
Publication date: 2006-08-17
Also published as: ITMO20050034A1

Abstract

A microwave device for the ablation of organic tissues comprising a coaxial antenna (1) insertible in a hollow needle (7) , said antenna (1) comprising: an internal conductor (2) , surrounded by a layer of dielectric material (3) ; an external conductor (4) externally coaxial with said layer of dielectric material, a portion of said dielectric material (3) and of said internal conductor (2) protruding from a distal end of said external conductor (4) , to constitute a radiant end (5) of said antenna (1) ; a quarter- wave impedance transformer (8) arranged coaxially to said antenna (1) and ending in a short circuit. Said device can also be provided with: cooling means (11, 12, 13, 14; 16, 17, 18, 19) arranged around the antenna (1) for at least a portion of the length thereof; solid state means (32) and corresponding accessories (33, 34, 35) for storing data in digital format, on which it is possible to record rating data of the device and data detected during use of the device; means for introducing the device directly into the biological tissues (7, 28, 28a, 30, 31) .

Description

Microwave device for the ablation of tissues

The present invention relates to a microwave device for the ablation of tissues , in particular an interstitial microwave applicator for hyperthermal treatment of biological tissues . The heating and coagulative necrosis of biological tissues caused by the absorption of electromagnetic waves is a well- known and tested technique used on its own or in combination with surgical or pharmacological techniques or with ionising radiation, in particular in the treatment of tumour pathologies . Interstitial applicators of electromagnetic radiation are widely used due to the lesser invasiveness of the intervention.

Microwave interstitial applicators offer, with respect to other electromagnetic applicators widely used in thermoablative treatment of biological tissues ( for example laser ray devices or radio-frequency electrodes) , some significant advantages - for the same power output and treatment duration - in terms of safety of treatment, extension and/or homogeneity and/or controllability of the heating figures and therefore of the volume of nectrotized tissue , with much more repeatable and uniform performance as the type of treated tissues varies . In particular, microwave applicators , of the same power, are able to nectrotize much greater volumes of tissue with respect to laser devices ; furthermore, the microwave applicators are much less sensitive than radiofrequency applicators to local variations in the electric conductivity of the organic tissue, which enables more uniform heating of the tissue in the zone irradiated by the microwaves and better repeatability of the results on any type of organic tissue . Furthermore, microwave applicators, unlike radiofrequency applicators , do not require earthing of the treated person and, in general , have less power density to the emitter, which reduces the risk of local carbonisation of the tissue . Lastly, for the same extent of necrosis obtained, an interstitial microwave device, compared to a radiofrequency applicator, generally requires significantly lower power levels ( from 5 to 10 times) over a shorter time (up to 50% less) .

In the prior art , microwave applicators are known consisting of a coaxial antenna comprising an internal conductor, a dielectric layer that covers the internal conductor for its entire length, an external conductor that covers coaxially the dielectric layer and the internal conductor, except for a distal end portion of the latter, constituting the radiant end of the antenna, the antenna being insertible into a catheter or metal needle or other appropriate introducing means through which it is introduced into the body of a patient until it reaches the zone of tissue to be treated. Whatever introducing means is used, at least in the final operating configuration, the radiant end portion of the antenna must be in direct contact with the tissue to be subjected to treatment, or must not have in the neighborhood thereof metal screening or highly absorbent layers that prevent or diminish the irradiation of microwaves to the surrounding tissues . Applicators are known, furthermore comprising a quarter-wave impedance transformer ending in a short circuit, commonly known as "choke", for example mounted around the external conductor of the antenna near said radiant end. It comprises -, a side wall consisting of a cylindrical pipe of conducting material that coaxially surrounds the external . conductor of the antenna and is closed on it in a short circuit at the end thereof further from the radiant end of the antenna; one or more dielectric sleeves in succession, to fill the entire space between said conducting pipe and the external conductor of the antenna, for the entire length of the conducting pipe (from the short-circuited end to the free end) . Such sleeves must have dimensions and electrical permittivity such that the physical length of the choke is matched by an equivalent electrical length (calculated as the sum of the products of the length of each dielectric sleeve by the corresponding index of refraction) equal to a quarter of the vacuum wavelength of the microwaves emitted by the antenna . This circumstance, as shown by the theory of the transmission lines , means that the input impedance of the choke at the distal end thereof (i . e . the end that is not short-circuited with the antenna) is virtually infinite, thus preventing the microwaves emitted to the radiant end of the antenna from being able to propagate also backwards along the external wall of the antenna and cause heating of the tissues also in zones that must not be subjected to heat treatment .

International patent application WO0261880 , discloses an antenna of the type mentioned above, in which the side conducting pipe of the choke , coaxial to the antenna, consists of the internal wall of the metal needle used to insert the antenna into the body of a patient . The short- circuit closing of the near end of the choke is obtained through a metal ring fixed to the external conductor of the antenna : the metal introducing needle can slide above the ring and form with it a sliding electrical contact, i . e . that also enables small adjustments to physical length and thus to the equivalent electrical length of the choke also in the course of coagulation treatment . Such adjustments may partially compensate any deterioration in the performance of the choke due to effects of thermal drift induced by the noticeable local temperature increase during treatment . Incorporating into the introducing needle the double function of inserting means of the applicator into the lesion to be treated and of the metal side wall of the choke enables minimisation of the transverse dimensions of the device, leading to the minimum degree of invasiveness given the dimensions of the coaxial antenna (proportional to the desired level of dispensable power) .

A drawback that occurs in known antennas is due to the propagation along the metal walls of the introducing needle of the heat generated by the dissipation of microwave power in the dielectric material and along the external and internal conductors of the coaxial antenna, to which the heat is added coming from the tissue subjected to hyperthermal treatment and propagating through heat conduction, also reverse heat conduction, with the consequent risk of overheating of the tissues surrounding the introducing needle for the entire length thereof , also in zones far from the region affected by the coagulative treatment . This may cause lesions to said tissues , that may also go as far as to affect the patient' s skin around the introduction point of the antenna . To these risks , there is added the annulment of the action, exerted by the choke, of controlling and delimiting the heating figure produced by the antenna . Another drawback generally exhibited by the known antennas relates to the poor stiffness and mechanical resistance of the radiant terminal portion of the antenna, that prevents the use thereof as a penetration tip into biological tissues for introducing the microwave applicator directly into the lesion to be subj ected to hyperthermal treatment . Lastly, known applicators lack associated unequivocal identifying means (that are tamperproof and are not separable from the applicator except at the end of the life cycle thereof) that , in addition to providing essential information (for example production data and expiry date) , actively protect both the applicator and ^• the patient from improper uses of the device (for example by setting a maximum dispensable power threshold and a maximum permissible threshold for the microwaves reflection coefficient, fixing precise compatibility criteria between the applier and the source of microwaves used to supply the antenna, preventing the reuse of applicators conceived for single use and already previously used, etc . ) . The present invention aims to remedy the drawbacks indicated above, in particular in order to exploit to the full and further extend the benefits of the invention disclosed in the international patent application WO0261880 and to overcome the limitations thereto .

According to the present invention a microwave • device is provided for the ablation of tissues comprising a coaxial antenna comprising an internal conductor, surrounded by a layer of dielectric material , an external conductor externally coaxial with said layer of dielectric material , a quarter-wave impedance transformer ending in a short circuit and with minimal lateral dimensions , characterised in that said antenna is provided with various alternative cooling means , each of said cooling means being arranged around the antenna for at least a portion of the length thereof . Owing to the invention, the temperature of the applicator, in particular of the metal walls of the introducing needle, can be maintained at levels such as not to damage through overheating the tissues placed along the insertion traj ectory of the applicator inside the lesion to be subj ected to coagulative treatment and to increase the performance of the coaxial antenna, so as to reduce the dimensions thereof (and thus decrease the overall dimensions and degree of invasiveness of the applicator) for the same dispensable power, or, vice versa, to increase the dispensable power (and thus increase the heating efficacy) with the same dimensions . Furthermore, the present invention comprises different alternative means for enabling the direct insertion of the applicator inside the tissue to be subj'ected to coagulative treatment , said means being coupled mechanically with the coaxial antenna, thus preventing the emission of microwaves from the radiant portion of the antenna being hindered, which facilitates the insertion operation without reducing the heating efficacy of the applicator .

Lastly, the present invention comprises a digital device associated with the applicator, having the function of a non-rewritable data memory, that is removable from the applicator only at the end of the life cycle thereof, also usable as a separate device for reading only the data contained therein, having data for identification and safe and appropriate use of the applicator and also usable for the recording of particularly significant data or measurements for the purposes of the evaluation of coagulative treatment , consultable in real time or also subsequently at the end of treatment .

Some ways of implementing the invention are disclosed below purely by way of non-limitative example, with reference to the enclosed drawings , in which:

Figure 1 is a longitudinal section view of a coaxial antenna usable in any embodiment of the device according to the invention;

Figure 2 is a longitudinal section view of a device according to the prior art defined by international patent application WO0261880 ;

Figure 3 is a longitudinal section view of a first embodiment of the cooling means that is associable with any embodiment of the device according to the invention,- Figure 4 is a longitudinal section view of a variant of the cooling system in Figure 3 ;

Figure 5 is a longitudinal section view of a second embodiment of the cooling means associable with any embodiment of the device according to the invention; Figures 6 to 9 , illustrate schematically the method of insertion into the body of a patient of any embodiment of the device according to the invention not provided with direct introducing means into the biological tissues ;

• Figures 10 and 11 illustrate a detail of a first embodiment of direct introducing means for introducing directly into the biological tissues , associable with any embodiment of the device according to the invention;

Figures 12 and 13 illustrate a detail of a second embodiment of direct introducing means for introducing directly into the biological tissues , associable with any embodiment of the device according to the invention, with reference, respectively, to the initial configuration (introducing into the lesion) and final configuration (irradiating inside the aforementioned lesion) of the device .

Figures 14 , 14a and 15 are, respectively, the first a frontal view and the remaining ones two longitudinal sections of a third embodiment of direct introducing means for introducing directly into the biological tissues associable with any embodiment of the device according to the invention, in the initial operating conditions (at the moment of introduction into the lesion to be treated, Figures 14 and 14a) and final operating conditions (at the moment of dispensing of microwave power into the aforementioned lesion, Figure 15) ; Figures 16 and 17 illustrate, respectively in a frontal view and in longitudinal section, a possible embodiment of the digital support , having the function of non-rewriteable data memory that is associable with any embodiment of the device according to the invention. The field of the invention comprises any device for interstitial hyperthermal treatment on biological tissues that is obtained by a coaxial antenna of the type in Figure 1 that is provided with a quarter-wave impedance transformer (choke) made as in Figure 2 , of cooling means as in Figures 3_. and 4 or as in Figures 5 and 6 , with introducing means as in Figures 7 to 10 , or with direct introducing means as in Figures 11 and 12 , or as in Figure 13 , or as in Figures 14 , 14a and 15 , and with a digital support having a data memory function as in Figures 16 and 17. In Figure 1 there is illustrated a coaxial antenna 1 usable in a device according to the invention, comprising an internal conductor 2 , surrounded by a layer of insulating material 3 surrounded in turn by an external conductor 4 , coaxial with the internal conductor 2. A distal end portion 5 of the internal conductor 2 with the corresponding layer of insulating material 3 protrudes from a distal end of the external conductor 4 , constituting the radiant end of the antenna 1. The end of the antenna opposite said end portion 5 is provided with a connector 6 for connecting the antenna 1 , directly or through suitable extension lines , to a source of microwaves . In Figure 2 there is schematically illustrated a device according to the prior art, in which the antenna 1 is inserted inside a hollow metal needle 7 the function of which is to guide the antenna 1 during introducing into the body of the patient . The antenna 1 is provided with a device 8 for blocking the reflected microwaves , in order to avoid indiscriminate heating of the tissues surrounding the applicator for the entire length of the introducing needle, also at a distance from the portion of tissue directly affected by the coagulative treatment . This device 8 is a quarter-wave impedance transformer terminating in a short circuit, commonly called a "choke", comprising a layer 9 of dielectric material that envelops like a sleeve the external conductor 4 of the antenna 1 , a ring 10 in conducting material , fixed to said external conductor 4 , and the portion of the metal walls of the hollow needle 7 in sliding contact with the side surface of said ring 10 and said dielectric sleeve 9. The equivalent electric length of the choke 8 is the same as a quarter of the vacuum wavelength of the microwaves that propagate inside the coaxial antenna 1 and are emitted by the latter.

In Figure 3 there is illustrated a first embodiment of the device according to the invention, that differs from the device according to the prior art illustrated in Figure 2 through the fact that it is provided with a cooling device of the antenna 1 , placed immediately upstream of the choke 8 looking in the direction of the microwave source that supplies the antenna 1. Furthermore, here as in all the other possible embodiments of the device that are illustrated below, the dielectric sleeve 9 that is part of the choke 8 can be formed, rather, than by a single layer of dielectric material, by a sequence of several sleeves of different dielectric materials, provided that the sum of the equivalent electrical lengths of the single layers amounts to a quarter of the vacuum wavelength of the microwaves emitted by the antenna - excluding from the calculation any portions of dielectric material that extend beyond the distal end section of the needle 7.

The cooling device in Figure 3 comprises a cylindrical chamber 11 that is coaxial to the antenna 1 and sealed, laterally delimited by a hollow cylindrical element lib, closed above by a cap 11a - through which the antenna 1 passes and which surrounds the antenna 1- and closed below by a second cap, or fixed (for example through welding or gluing) to the metal ring 10. The external diameter of the hollow cylindrical element lib is chosen in such a way that it can be housed inside the hollow needle 7. In the cylindrical chamber 11 a cooling liquid 12 is circulated that is brought to the cylindrical chamber 11 through a delivery conduit 13 supplied by a pump, for example a peristaltic pump (not shown) , and is evacuated from the cylindrical chamber 11 through an evacuating conduit 14 , connected to a collecting tank (not shown) . The conduits 13 and 14 penetrate inside the chamber 11 , the same- as the antenna 1 , through the top cap 11a . Circulating a liquid at ambient temperature - or below - around the antenna 1 for the entire length of the chamber 11 enables the heat generated by the ohmic losses in the antenna 1 to be removed (by convection) and the consequent cooling of the walls of the introducing needle 7. In Figure 4 there is illustrated a variant of the disclosed cooling system by means of forced circulation of liquid around the antenna 1 , in which the cylindrical chamber 11 is delimited laterally by the internal walls of the needle 7 , below by the metal ring 10 and above by the cap 11a through which the- antenna 1 and the refrigerant delivery and evacuating conduits 13 and 14 passes , the seal between needle 7 and cap 11a above and between needle 7 and metal ring 10 below being assured by two gaskets , respectively lie and Hd (for example, two 0-rings) , housed between suitable seats obtained in the cap Ha and in the ring 10. This second embodiment of the forced cooling with refrigerant liquid obtains, due to the elimination of the hollow cylindrical element Hc , an increase of the space available for housing the various components of the device that are located inside the introducing needle 7. In the cooling systems in Figures 3 and 4 , if the level of power required in the hyperthermal applications does not exceed a given threshold (quantifiable as 60-70 W for coaxial antennas with an external diameter of a millimetre) , the use of refrigerant at ambient temperature has proved experimentally suitable for the purpose, even if the refrigerant is not subject to replacement , but is pre-charged into the sealed chamber 11 and is made to flow continuously between the chamber and the external pumping line (not shown in the figure) , to form a closed hydraulic circuit . In this way, the use of external tanks for the refrigerant can be avoided and the procedures for preparing and installing the applicator before the coagulating treatment can be shortened.

The device according to the present invention is provided

(in the embodiments disclosed so far, as in all the others presented below) , with at least a temperature sensor 15 , for example a thermocouple joint or an optic fibre sensor, the sensitive end element of which is located just above the metal ring 10 , inside the hollow needle 7. The temperature measurements made by the sensor 15 provide an important indication of the state of advance of the hyperthermal treatment at a fixed distance from the radiant portion of the antenna 1 , constantly monitoring treatment performance in terms of security, efficacy and correct actuation and providing an obj ective criterion for stopping treatment . The device according to the invention can be provided with other temperature sensors (not shown) located at different heights along the stem of the coaxial antenna 1 or along the wall of the introducing needle 7 , for example for the purpose of monitoring the efficacy of the cooling action. In Figure 5 there is illustrated another embodiment of a device 1 according to the invention, in which cooling is obtained by installing around the hollow needle 7 a sleeve

16, in the inside of which an annular chamber 17 is defined into which there is inserted a rapid cooling assembly consisting of two substances that , when they come into contact with one another, develop a highly endothermal chemical reaction. The first substance is inserted into the annular chamber 17 , whereas the second substance is contained in a perforable container 18 that is also inserted into said annular chamber 17. A perforating element 19 that may be operated from outside is associated with the annular chamber 17 and is used perforate the container 18 , to place the two substances in contact and start the endothermal reaction, which causes rapid cooling of the annular chamber

17 , thus causing removal of heat from the hollow needle 7 and from the antenna 2 inserted therein. Alternatively, the container 18 may consist of two distinct and non-communicating bags suitable for respectively housing the two reagents and keeping them separate until the perforating element 19 is operated, that is able to perforate simultaneously both bags so as to obtain the mixing and chemical reaction between the two substances inside the chamber 17.

In order to encourage the passage of heat from the antenna 2 to the annular chamber 17 through the hollow needle 7 , between the antenna 1 and the internal wall of the needle 7 a material 20 is inserted that is a good heat conductor .

The annular chamber 17 may slide above the hollow needle 7 , which, at the end of the procedure of inserting the applicator into the body of the patient, enables the chamber to be positioned at the shortest possible distance from the distal end of the applicator (thus in contact with the skin of the patient) so as to optimise the refrigerating action. In Figures 6 to 9 there are illustrated schematically the methods of introducing into the body of the patient versions of the device according to the invention that are not provided with means for direct percutaneous insertion. In order to introduce said versions of the device according to the invention into the body of a patient, the hollow needle 7 is first introduced, with the help of an extractable mandrel 21 that is provided with a perforating tip, until it reaches the zone that has to be subj ected to thermal treatment through microwaves .

The mandrel 21 is then extracted from the hollow needle 7 and the antenna 1 is then inserted that is illustrated in Figure 7 , until the radiant end 5 of the antenna is aligned with the end of the hollow needle 7 (as in Figure 8) : the alignment is facilitated by a first reference mark 22 located, for example, on the external surface of the metal ring 10 , suitably elongated in the direction of the near end of the antenna to almost totally cover the antenna; lastly, the hollow needle 7 is retracted to expose the radiant end 5 of the antenna 1 and adjust the electric length of the choke 8 so that it corresponds to a quarter of the vacuum wavelength of the microwaves used; for this purpose, on the external surface of the metal ring 10 a second reference mark 23 may be provided (as shown in Figure 9) or a simple mechanical end stop system for the needle (not shown) . At this point , the antenna 1 , once it is connected between the connector 6 to a suitable source of microwaves , is ready to- irradiate microwaves to the tissues surrounding the radiant end 5. In Figures 10 and 11 , there is illustrated a first embodiment of a device according to the invention that is able to penetrate an organic tissue directly, without the need for an auxiliary penetration mandrel , owing to the^' presence at the distal end of the hollow needle 7 of a perforating tip 28. In the side walls of the hollow needle 7 , near the tip 28 , slits 29 are made to enable irradiation of the microwaves coming from the radiant end 5 of the antenna 1. The dimensions of the slits 19 are selected so as to hamper minimally the diffusion of the microwaves coming from the radiant end 5 of the antenna 1 and so as not to excessively weaken the structure of the end part of the hollow needle 7. Furthermore, the radiant end 5 of the antenna 1 is ■ completely wound by the dielectric material 9 of the choke, in order to increase the mechanical resistance of the distal portion of the device . In this embodiment, the radiant portion 5 of the antenna 1 is therefore inserted into the body of a patient together with the hollow needle 7 , using the penetration tip 28 of the hollow needle 7. In the embodiment of the device according to the invention illustrated in Figure 12 the dielectric material 9 completely envelops the radiant end 5 of the antenna 1 and at the far end thereof has a metal penetration tip 28a, that is suitably fixed, for example, through gluing, snap- connection or screw-connection. This tip 28a is initially on the distal end of the hollow needle 7. The radiant end 5 of the antenna may, (but does not necessarily have to) go as far as touch the tip 28a - as shown in Figure 12 - , in which case further fixing of the tip 28a through welding to the far end of the central conductor 2 of the antenna 1 can be provided. Once the procedure of direct insertion of the device inside the body of the patient has been terminated using the penetration capacity of the tip 28a, the needle 7 is made to slide above the metal ring 10 (the antenna 1 remaining stationary) , so as to achieve the final operating configuration of the applicator shown in Figure 13. Precisely the retraction of the needle 7 with respect to the antenna 1 results in forming a choke 8 having the correct electric length and, simultaneously freeing the radiant end 5 of the antenna 1 from metal screens hampering the irradiation of microwaves to the surrounding tissues . A possible guided and secure needle .7 retraction mechanism for retracting the needle 7 with respect to the antenna 1 is disclosed below.

In Figures 14 , 14a and 15 there is illustrated a further embodiment of the device according to the invention in which at the proximal end of the hollow needle 7 there is associated a cap 30 provided with a vertical or also curved slit 30a, (as in Figure 14 ) , terminating in two slots 30b and 30c arranged horizontally, said cap being able to slide above a sleeve 31 fixed to the proximal end of the antenna 1 (opposite the distal radiant end 5) , or the associated cooling space 11 (as in Figures 14a and 15) . In said sleeve a locking pin 31a is inserted, initially locked inside the slot 30b of the slit 30a made on the walls of the cap 30 , so as to maintain the initial mutual positions of the introducing needle 7 and antenna 1. A sleeve 9a of dielectric material is fixed to the distal end of the hollow needle 7 (for example by means of gluing or through snap- fitting) ; the central hole of this sleeve has a diameter that is slightly greater than the diameter of the external conductor 4 of the antenna 1 , except for a short portion at the distal end, where the hole narrows until it reaches a diameter that is hardly greater than that of the dielectric material 3 of the antenna 1. A second dielectric sleeve 9 is on the other hand fixed to the antenna and leans against the metal ring 10 that closes the choke 8 , as already seen in the previous embodiments of the device . The distal end 7a of the hollow needle 7 , the distal end 9b of the sleeve 9a of dielectric material integral with the tip of the needle and the distal end Ia of the antenna 1 are cut obliquely along the same plane, forming an acute angle with the longitudinal axis of the antenna 1. In the initial configuration of the device, shown in Figures 14 and 14a, these distal ends 7a, 9b and Ia, respectively, of the needle 7 of the dielectric sleeve 9a and of the antenna 1 , are aligned so a to form a full and sharp tip shaped like a flute mouthpiece or like other suitable profiles . This tip easily penetrates inside the organic tissues and thus enables the direct insertion of the device into the body of a patient , thus preventing potentially infected or cancerous tissue material being collected inside the hollow needle 7 that would risk being disseminated along the introduction/extraction traj ectory of the device .

Once the procedure of inserting the applicator into the zone to be subj ected to heat treatment has terminated, the sleeve 31 is kept stationary and the cap 30 is rotated so as to release the locking pin 31a from the slot 30b of the slit 30a of the cap 30 and raise said cap in the direction of the distal end of the sleeve 31 , this movement being guided by the sliding of the walls of the slit 30a around the locking pin 31a, as far as the locking 31a is definitively positioned through snap-fitting inside the slot 30c , acting as an end stop . In the screwing movement of the cap 30 , the needle 7 and the dielectric sleeve 9a (that are integral with one another and with the cap 30) slide on the antenna 1

(stationary, because integral with the sleeve 31) , until the sleeve 9a abuts on the other sleeve 9 fixed to the antenna, to constitute a sequence of dielectric layers inside the choke 8 (comprised between the metal ring 10 and the distal end of the arrow 7) having an electric length that is equivalent to a quarter of the wavelength of the microwaves emitted. This operation leaves the emitting portion 5 of the antenna 1 completely exposed (except for a short portion at the proximal end of the radiant tip 5 , corresponding to the narrowing of the central hole in the sleeve 9b) , that is now finally available to irradiate microwaves to the surrounding tissue . This final operating configuration of the device is illustrated in Figure 15.

The device according to the invention can be provided with a solid-state microchip 32 (Figures 16 and 17) having a non- rewritable memory, on which it is possible to record and from which it is possible to extract data in digital format for unequivocal identification of the device, for complete traceability of the origin thereof , for an exhaustive technical and constructional characterisation thereof, for active protection against dangerous or incorrect uses , and data on the thermal treatment conducted by means of the device, that are already consultable during the running of treatment , or also in a subsequent period. The consultation of said data in the course of treatment is particularly useful for modifying, for example, the supply of the antenna 1 and/or the flow of the cooling liquid 12 , in order to optimise the results of the treatment , or to avoid undesired effects . For this purpose, the microchip 32 can be connected to a data-processing system suitable for controlling the supply of the antenna 1 , and the circulating pump of the cooling liquid 12 , in function of the rating data pre- recorded on the microchip (production data, technical features, safety thresholds, etc . ) and the treatment parameters recorded in real time on the microchip . The microchip 32 can be connected to the device according to the invention by means of a connector 36 , for example the connector used to connect the temperature sensor 15 to the reader (not shown) . The connector 36 comprises a base 33 with contact elements 36 for the electric wires 27 coming from the temperature sensor 15 and for the microchip 32 , and a cap 34 that , after carrying out the connections (for example through welding) , can be fixed in a non-removable manner to the base 33 , for preventing and/or highlighting any tampering of the connector 36.

At the end of the thermal treatment the microchip 32 can easily be recovered and used as a separate digital device by separating the connector 36 from the electric wires 27 at the inlet to the connector .

In the practical embodiment, the materials , the dimensions and the constructional details may be different from those indicated but be technically equivalent thereto, without thereby falling outside the scope of the present invention.

Claims

1. Microwave device for the ablation of organic tissues comprising a coaxial antenna (1) insertible in a hollow needle (7) , said antenna (1) comprising an internal conductor (2 ) , surrounded by a layer of dielectric material

(3 ) , an external conductor (4) externally coaxial with said layer of dielectric material , a portion of said dielectric material (3 ) and of said internal conductor (2 ) protruding from a distal end of said external conductor (4) to constitute a radiant end (5) of said antenna (1) , a quarter- wave impedance transformer ( 8) ending in a short circuit , characterised in that said antenna (1) is provided with cooling means (11 , 11a, lib, 12 , 13 , 14 ; 16 , 17 , 18 , 19) , said cooling means ( 11 , 12 , 13 , 14 ; 16 , 17 , 18 , 19) being arranged around said antenna (1) for at least a portion of the length thereof .

2. Device according to claim 1 wherein said quarter-wave impedance transformer (8) ending in a short circuit comprises at least a layer ( 9) of dielectric material , that envelops like a sleeve a portion of said external conductor

(4 ) of the antenna (1) , and a ring (10) in conducting material , fixed to said external conductor . (4 ) , the side surface of which is in contact with the internal surface of the hollow needle ( 7) .

3. Device according to claim 1 , or 2 , wherein said cooling means (11 , 12 , 13 , 14 ) comprises a chamber (11) arranged coaxially with respect to a portion of said antenna (1) , a cooling fluid (12 ) being made to circulate inside said chamber (11) .

4. Device according to claim 3 , wherein said chamber (11) is connected to a supply conduit (13 ) and to an evacuating conduit (14) of said cooling fluid (12) , said supply conduit ( 13 ) and evacuating conduit ( 14 ) being connected to circulating means of said fluid (12) .

5. Device according to claim 4 , wherein said circulating means comprises a peristaltic pump .

6. Device according to any one of claims 3 to 5 , wherein into said chamber (11) there is inserted at least a temperature sensor (15) .

7. Device according to any one of claims 3 to 6 , wherein said chamber (11) is defined inside a hollow cylindrical element ( lib) insertable inside said hollow needle ( 7) .

8. Device according to claim 7 , wherein said hollow cylindrical element (lib) is closed at a proximal end by a first closing element (lla) and at a distal end by a second closing element (10) .

9. Device according to claim 8 , wherein said second closing element consists of said ring (10) in conducting material to which there is fixed said distal end of the hollow cylindrical element (lib) .

10. Device according to claim 8 , or 9 , wherein said first closing element (lla) is provided with openings for the passage therethrough of said coaxial antenna (1) , said supply conduit (13 ) , said evacuating conduit (14 ) and said temperature sensor (15) .

11. Device according to any one of claims 3 to 6 , wherein said chamber (11) is defined between the internal walls of said hollow needle (7) , said ring (10) in conducting material , and a closing element (lla) inserted between said antenna (1) and the internal walls of the hollow needle (7) .

12. Device according to claim 11 , wherein a first gasket (lie) is inserted into a seat obtained in said closing element (lla) and a second gasket (Hd) is inserted into a seat obtained in said ring (10) in conducting material .

13. Device according to claim 11 , or 12 , wherein said closing element (Ha) is provided with openings for the passage therethrough of said supply conduit (13 ) , said evacuating conduit (14 ) and said temperature sensor (15 ) .

14. Device according to any one of claims 3 to 13 , wherein said cooling fluid is preloaded in said chamber (11) and is circulated in a closed circuit comprising said chamber (11) , said supply conduits (13 ) and evacuation conduits (14) and a pumping line outside the device .

15. Device according to claim 1 , or 2 , wherein said cooling means (16 , 17 , 18 , 19) comprises sleeve means (16) inside which there is defined an annular chamber (17) in which there is inserted a cooling assembly (18 , 19) .

16. Device according to claim 15 , wherein said cooling assembly (18 , 19) comprises a first substance and a second substance that are suitable for developing an endothermal chemical reaction when they come into contact with one another .

17. Device according to claim 16 , wherein one of said first substance and second substance is inserted into said annular chamber (17) , whilst the other of said first substance and second substance is contained in a perforable container (18 ) inserted into said annular chamber (17) .

18. Device according to claim 17 , furthermore comprising a perforating means (19) associated with said annular chamber

(17) and suitable for perforating said container (18) for enabling the contact between said first substance and said second substance .

19. Device according to claim 16 , wherein one of said first substance and second substance is inserted in a first perforable container, whereas the other one between said first substance and second substance is contained in a second perforable container, said first perforable container and said second perforable container being inserted into said annular chamber (17 ) .

20. Device according to claim 19 , furthermore comprising a perforating means associated with said annular chamber and suitable for perforating said first container and said second container to enable the contact between said first substance and said second substance .

21. Device according to any one of claims 15 to 20 , wherein inside said hollow needle (7) , between the external surface of said antenna (1) and the internal surface of the hollow needle (7) there is arranged a heat conducting means (20) .

22. Device according to any one of claims 15 to 21 , wherein inside said hollow needle ( 7) , between the external surface of said antenna (1) and the internal surface of the hollow needle ( 7) , there is inserted at least a temperature sensor (15) .

23. Microwave device for the ablation of organic tissues comprising a coaxial antenna (1) insertible in a hollow needle (7 ) , said antenna (1) comprising an internal conductor (2 ) , surrounded by at least one layer of dielectric material (3 ) , an external conductor (4) externally coaxial with said layer of dielectric material , a portion of said dielectric material (3 ) and of said internal conductor (2) protruding from a distal end of said external conductor (4 ) to constitute a radiant end (5) of said antenna (1) , a quarter-wave impedance transformer (8) ending in a short circuit , characterised in that it is provided with penetrating means (Ia, 7a, 9a, ; 28 ; 28a) suitable for enabling the penetration of the device into an organic tissue .

24. Device according to any one of claims 1 to 22 , furthermore comprising penetrating means ( Ia, 7a, 9a; 28 ; 28a) suitable for enabling the penetration of the device into an organic tissue .

25. Device according to claim 23 , or 24 , wherein said at least one layer of dielectric material ( 9) also envelops the radiant end (5 ) of the antenna ( 1)

26. Device according to any one of claims 23 to 25 , wherein said penetrating means comprises a penetration tip (28) associated with a distal end of said hollow needle ( 7) , a side surface of the hollow needle (7 ) being provided with slits (29) near said penetration tip (28) .

27. Device according to claim 26 , wherein said penetration tip (28) forms a single body with the distal end of said hollow needle (7 ) .

28. Device according to any one of claims 23 to 25 , wherein said penetrating means comprises a penetration tip (28a) fixed to a distal end of said at least one layer of dielectric material ( 9) .

29. Device according to claim 28 , wherein said penetration tip (28a) is fixed to said at least one layer of dielectric material (9) by gluing, or a screw connection or a snap connection.

30. Device according to any one of claims 23 to 25 , wherein said penetrating means comprises a tapered distal end (7a) of said hollow needle ( 7 ) , tilted in relation to the longitudinal axis of said antenna ( 1) .

31. Device according to claim 30 , wherein a distal end ( 9b) of said dielectric material ( 9 , 9a) is tilted in relation to the longitudinal axis of the antenna ( 1) by an angle of tilt that is substantially the same as the angle of tilt of said tapered distal end (7a) of the hollow needle (7) .

32. Device according to any one of claims 2 to 31 , wherein said at least one layer of dielectric material comprises a plurality of layers ( 9 , 9a) each of which envelops like a sleeve a portion of said external conductor (4) of the antenna ( 1) .

33. Device according to claim 32 , wherein said plurality of layers of dielectric material comprises a first layer (9) fixed to said ring (10) of conducting material and a second layer ( 9a) fixed to a distal end (7a) of said hollow needle ( 7 ) .

34. Device according to claim 33 , wherein a distal end (9a) of said second part (9a) and a distal end of said antenna

(1) are tilted in relation to the longitudinal axis of said antenna (1) .

35. Device according to any one of claims 30 to 34 , wherein with said hollow needle ( 7 ) a cap (30) is associated provided with a vertical or curved slit (30a) terminating in two slots (30b) and (30c) arranged horizontally, said cap being able to slide above a sleeve (31) , fixed to a proximal end of the antenna (1) opposite the radiant end (5 ) .

36. Device according to claim 35 , wherein said sleeve (31) is provided with a stop element (31a) couplable in said slit (30a) and lockable in said slots (30b, 30c) .

37. Device according to any preceding claim, wherein said antenna (1) is provided at the proximal end thereof with connecting means ( 6) for being connected to a microwave supply source .

38. Microwave device for the ablation of organic tissues comprising a coaxial antenna (1) insertible in a hollow needle (7) , said antenna (1) comprising an internal conductor (2 ) , surrounded by a layer of dielectric material

(3 ) , an external conductor (4) externally coaxial with said layer of dielectric material , a portion of said dielectric material (3 ) and of said internal conductor (2) protruding from a distal end of said external conductor (4 ) to constitute a radiant end (5) of said antenna (1) , a quarter- wave impedance transformer ( 8) ending in a short circuit , characterised in that it comprises solid-state microchip means (32 ) .

39. Device according to any one of claims 1 to 37 , furthermore comprising solid-state microchip means (32) .

40. Device according to claim 38 , or 39 , wherein said microchip means (32) comprises a non-rewritable memory .

41. Device according to claim 40 , wherein said microchip means (32 ) is connectable to a data-processing system suitable for controlling the supply of the antenna (1) , and the circulating means of the cooling fluid (12 ) .

42. Device according to any one of claims 38 to 41 , wherein said microchip means (32 ) is connected to connector means (36) to which also said temperature sensor (15) is connected.

43. Device according to claim 42 wherein said connector means (36) comprises a base (33 ) provided with connecting means (35) for said microchip means (32 ) and said temperature sensor (15) and a cap (34) that is fixable to said base (33 ) .

44. Device according to claim 43 , wherein said cap (34) is fixed to said base (33 ) in a non-removable manner .