HK1086733A - Interstitial microwave antenna with lateral effect for tissues hyperthermia in minimal invasive surgery - Google Patents

Description

Interstitial microwave antenna with lateral effect for tissue hyperthermia in minimally invasive surgery

Technical Field

The present invention relates to minimally invasive surgical techniques for the thermal treatment of solid-state deep wounds for applications in medical and surgical (especially oncology) interstitial, percutaneous, laparoscopic, endoscopic and surgical applications. More precisely, the invention relates to a microwave coaxial antenna, which is dedicated to the hyperthermia of large tissue masses. In addition, the invention relates to a method for manufacturing such an antenna.

Background

In oncology, hyperthermia is a method that has been used in the treatment of cancer for more than 30 years (Hahn GM, hyperthermia and cancer, Plenum press, new york, 1982). The method includes heating cancer cells to necrose, either directly or with the assistance of other methods, such as radiotherapy, chemotherapy, or other surgical techniques.

For heating tissue, in particular for treating surface lesions, electromagnetic waves generated by sources located outside the human body are first used.

More recently, very fine instruments (thin appliance) have been employed for Interstitial, percutaneous, laparoscopic, endoscopic and intra-operative applications, and for local treatment of deep lesions, where microwave Antennas operate between several hundred MHz to several thousand MHz generated by coaxial tubes, typically 2450MHz (Iskander MF & tube AM, optimized design of Interstitial Antennas, IEEE protocols for Biomedical Engineering (IEEE transactions on Biomedical Engineering), 1989, 283-.

In computerized imaging techniques (e.g., echographic guiding), TAC, NMR or other), such antennas are typically inserted into the lesion for treatment through a catheter or metal needle. They are suitable for use in conjunction with other procedures (e.g., medication, ionizing waves, and/or surgical resection).

These microwave antennas are generally manufactured using a flexible or semi-rigid coaxial tube suitably modified at one end for transmitting microwave power into the tissue for hyperthermia.

The use of minimally invasive microwave coagulation Therapy (TCMM) for percutaneous, laparoscopic applications and the like is well known and well documented in many industrial countries outside europe (usa, japan, canada, china, etc.).

This therapy typically introduces a small diameter coaxial antenna directly into the lesion center of cancerous or hypertrophic tissue by introducing a metal needle or plastic catheter.

In fig. 1, an axial cross-section of an antenna 100 in combination with a biopsy needle 101 of the prior art is shown. The active device of the antenna on the right side of the figure is suitably configured as a radiating dipole or monopole. More precisely, 107 is the outer conductor of the coaxial tube and 109 is the insulating layer separating the outer conductor from the central conductor 108. An isothermal surface with a rotationally symmetric structure can be obtained by heating biological tissue (not intersecting large blood vessels) using a standard antenna 100, which can be made, for example, by cutting the end of the outer conductor 107 of a coaxial tube and leaving the insulating layer 109 exposed, as shown in fig. 1.

Once placed in the lesion, the antenna emits microwave power (typically 60W at 2450MHz frequency) beyond the active device of the needle 101 sufficient to necrose the globular bulk tissue 112 within a few minutes, for example, 2-3 minutes to coagulate 10ml of water-storing tissue. Coagulation necrosis caused by this treatment destroys the tissue that normally stays where the fibrosis is treated, which shrinks and does not further affect the adjacent areas. However, with increasing duration of treatment and/or of the power supplied by the microwave antenna, the volume of the clot does not grow proportionally, since the heat is reduced proportionally to the surface of the treatment volume by the blood circulation and by conductive diffusion, with the result that lesions of diameter not greater than 2-3cm can be treated in a single operation using an antenna of conventional type.

With the prior art treatment of lesions of larger diameter (> 3cm), the treatment must be repeated by inserting a single antenna 100 in succession as shown in fig. 2A, or introducing multiple antennas 100 simultaneously. As shown in fig. 2B, in this case it is known to use a multi-element support 120 to guide all the needles together (as an array). In both cases, the wound indication of the heat treatment and the pain immediately felt by the patient are significantly increased.

It must be noted that a lesion with a diameter of 8cm requires 20 to 30 single operations, considering the overlap safety factor of 1cm, if TCMM operation alone is sufficient to treat a lesion with a diameter of 3 cm. Thus, the antenna array can only be used when the lesion can be treated with not too many antennas, since otherwise the trauma rate is practically similar to that of a conventional surgical procedure, and also in the case of treatment by inserting a single applicator (applicator) in large numbers in succession at different points.

As shown generally in fig. 2A, by treating liver lesions in a percutaneous manner using an antenna 100 of conventional type, although lesions 20 can be treated even if a large number of insertions are required to coagulate the entire mass, there is inevitably a risk of penetrating or coagulating blood vessels in order to treat lesions 21 in the vicinity of large blood vessels 25.

In addition, the irregular shape of the lesion or the inability to pass longitudinally by the applicator is another difficulty with conventional applicators currently in use.

Disclosure of Invention

It is a feature of the present invention to provide a microwave coaxial antenna for applications in medicine and surgery for further reducing the treatment trauma of minimally invasive microwave coagulation therapy with respect to the prior art, avoiding the increase in the number of operations (by repeatedly extracting and reintroducing applicators at different points of the tissue) and the need for antenna arrays required to treat large lesions with a single, conventionally designed antenna.

It is another feature of the present invention to provide an antenna that is inserted into a lesion and advanced at an adjustable angle in a lateral/oblique direction relative to the axis of the applicator needle.

It is a further feature of the present invention to provide a method for manufacturing such an antenna and its application device.

These and other features are achieved by an exemplary antenna for interstitial, percutaneous, laparoscopic, endoscopic and intraoperative applications in medicine and surgery, particularly for acute hyperthermia in oncology, comprising:

an inner conductor is provided on the inner surface of the inner conductor,

an insulating layer covering the entire length of the inner conductor,

an outer conductor coaxially covering a portion of the insulating layer except for an end portion,

a tubular application device for introducing the antenna coaxially along an introduction direction into the target tissue,

characterized in that the application device has, at its end, a side opening and an inclined guide adapted to guide the antenna through the side opening into the target tissue along an action direction at an angle a to the application device.

Preferably, the application device is a metal needle or a plastic tube having in the end a hard blocking material, for example a metal, having a tapered inner surface forming the inclined guide and a sharp outer surface.

Alternatively, the application device has a thickness at said end portion that gradually increases to form said inclined guide.

Advantageously, for introducing the antenna in the target tissue along the action direction, a metallic flexible mandrel is provided, which slides in the application device before introducing the antenna and is adapted to protrude therefrom through the side opening to form an inlet hole in the tissue for treatment according to the action direction.

Once the hole along the direction of action is made, the mandrel is removed from the application device and replaced with a coaxial antenna inserted to the appropriate length in the hole previously made by the mandrel for correct operation. When the treatment zone has reached a predetermined temperature, the antenna is then removed and inserted in another position, without forming further inlet holes, after rotating the application device by a certain angle or moving it along the introduction direction. In this way, thermal treatment can be applied to axially symmetric tissue masses or irregularly shaped tissue masses.

In addition, such an antenna allows to heat lesions located laterally with respect to the application device, and which the needle does not need to pass through. This feature allows to treat lesions extending in the vicinity of large blood vessels, which cannot be treated by the antennas of the prior art due to the risk of penetrating the blood vessel.

In particular, the needle can be replaced by another needle having a different angle of action α with respect to the introduction direction. Within certain limits, the length of the antenna beyond the opening portion may also be varied. In this way, the shape of the operating region can preferably be changed.

Drawings

Other features and advantages of the tissue gap antenna according to the invention will become more apparent from the following description, given with reference to the accompanying drawings, which illustrate but do not limit the invention, by way of example only, and in which:

FIGS. 3 and 4 show an axial section of an application device for a tissue gap antenna according to the invention;

FIGS. 5 and 6 show axial cross-sections of a tissue gap antenna according to the present invention;

FIG. 7 shows an axial cross-sectional view of another illustrative embodiment for the applier device of FIG. 3;

fig. 8 exemplarily shows a possible use of the tissue gap antenna of fig. 5 and 6.

Detailed Description

In fig. 3, an application device 1 according to the invention is shown in axial section, for example a metal needle or a plastic tube, the thickness of which at the end 2 of the free end gradually increases to form a substantially inclined guide 3 terminating in a side opening 4 formed on the application device 1. In this way, a tissue gap antenna 10 is formed by the coaxial tube with the outer conductor 7, the insulated cable 9 and the central conductor 8 embedded in the insulated cable 9 insulating it from the outer conductor 7 (fig. 6). The antenna 10 can be placed into the target tissue along an action direction forming an angle alpha with the introduction direction.

With reference to fig. 4, in order to introduce the cable 9 into the target tissue along the action direction, a metallic flexible mandrel 5 is provided, which is suitable to be shaped so as to slide in the application device 1 and to be able to protrude therefrom through the side opening 4, in order to create an entry hole in the tissue for treatment according to the action direction forming an angle α with the introduction direction.

Then, once the hole has been made in the action direction, mandrel 5 is taken out of application device 1 and replaced with cable 9, which is inserted in the hole previously made by mandrel 5 by the appropriate length for correct operation (fig. 6).

In particular, the calculated isothermal surface obtained by the antenna is represented in fig. 6 by a curved dashed line 12, whereas the actual isothermal surface (i.e. the mass of tissue actually coagulated) is contained within a curve 13, since the end of application device 1 is electrically connected to outer conductor 7, thus increasing its active area.

When the treatment area reaches a predetermined temperature, cable 9 is withdrawn and, after rotating application device 1 by a certain angle or after moving it along the introduction direction, it is placed again without forming further inlet holes 11, as shown in fig. 8. It is sufficient to repeat the above operations through the mandrel 5 and then through the cable 9. In this way, the treatment trauma can be significantly reduced, avoiding the need to increase the number of operations required to treat a large lesion 20 with a single conventionally designed antenna 100 (fig. 2A) and the use of an antenna array (fig. 2B), which requires a single but larger diameter hole.

Moreover, the antenna 10 according to the invention allows to heat lesions located laterally with respect to the application device 1 without the holes having to pass through these lesions. This feature allows treatment of lesions 21 extending near large blood vessels 25, which cannot be treated with prior art antennas (fig. 2A), otherwise there would be a risk of penetration of the blood vessel 25.

In fig. 7, another illustrative embodiment for application device 1 is shown. This embodiment proposes that the metal needle or plastic tube 1 is associated with a hard material (e.g. metal) blocking piece 6, this blocking piece 6 having a side opening 4, a conical inner surface forming the inclined guide 3 and a sharp outer surface. The needle 1 and blocking member 6 are releasably engaged, for example by a threaded coupling 1a-1 b. In this way, simply replacing the blocking member 6 to adjust the angle α of the direction of action with respect to the direction of introduction makes it possible to vary the shape of the operating zone as desired.

The foregoing description of the specific embodiments will so broadly disclose the invention that others can, by applying current knowledge, modify and/or adapt for various applications such embodiments without further research and without parting from the invention, and it is therefore to be understood that such adaptations and modifications will have to be considered as equivalent to the specific embodiments. In this regard, the apparatus and methods for performing the various functions described herein may be of varying nature without departing from the scope of the invention. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Claims (4)

1. A microwave device for interstitial, percutaneous, laparoscopic, endoscopic and surgical applications in medicine and surgery, in particular for acute hyperthermia in oncology, comprising:

an inner conductor;

an insulating layer covering the entire length of the inner conductor;

an outer conductor coaxially covering a portion of the insulating layer except for an end portion and forming a coaxial antenna together with the insulating layer and the inner conductor;

a tubular application device for introducing the antenna coaxially along an introduction direction into the target tissue,

characterized in that the application device has, in its end, a side opening and an inclined guide which guides the antenna through the side opening to the target tissue in an action direction forming an angle a with the application device.

2. The microwave device for tissue gap applications according to claim 1, characterized in that the applicator device is a metal needle or a plastic tube with a hard blocking material in the end, such as a metal, having a conical inner surface forming the inclined guide and a sharp outer surface.

3. The microwave device for tissue gap applications according to claim 1, wherein the applicator device is a hollow needle, the end of which is blind and has the side opening, wherein the thickness at the side opening is gradually increased to form the inclined guide.

4. The microwave device for interstitial application according to claim 1, wherein for the introduction of the antenna into the target tissue along the action direction a metallic flexible mandrel is provided, which slides in the application device before the introduction of the antenna and is adapted to protrude therefrom through the side opening to form an inlet hole in the tissue according to the action direction for the treatment.