ITFI20080176A1 - "METHOD AND DEVICE FOR ECOGRAPHIC TREATMENT AND MONITORING THROUGH PERCUTANEOUS LASER ABLATION" - Google Patents

Description

Method and device for ultrasound treatment and monitoring by percuteal laser ablation

Description

Technical field

The present invention relates to the sector of electromedical equipment. More particularly, the present invention relates to the field of equipment for the treatment of percutaneous ablation of tissues by means of a laser.

Basis of the invention

The necrosis of a tumor tissue can today be achieved with numerous techniques, which are distinguished by the degree of invasiveness, by the effectiveness, by the reproducibility of the volumetric and morphological characteristics of the lesion produced, by the possibility of performing in day-hospital, for patient tolerability and reduced costs. These factors together with the technological developments recently achieved allow the development of a series of therapeutic applications unified by a common denominator: microinvasiveness.

Therefore, this group includes all those therapies defined as "percutaneous", since the applicators are inserted through the patient's skin, inside fine needles, until they reach the center of the lesion to be treated.

Among the potential benefits of these methods are included the possibility of destroying the pathological zone "in situ" in inoperable subjects or at high surgical risk, the reduction of side effects and hospitalization times when compared with that of traditional surgery.

The induction of tissue necrosis can occur by coagulation through the use of different energy sources, such as laser, radiofrequency, or through the injection of pure ethanol (so-called PEA technique, Percoutaneous Ethanol Ablation).

The use of lasers in thermotherapy seems to be elective for some districts and in some pathologies thanks to its effectiveness due to greater control of the energy delivered and the extension of the region of necrosis produced. Especially in thyroid pathologies, both benign (goiter) and malignant, the laser technique has undoubted advantages of effectiveness compared to other treatment techniques. The ultrasound-guided laser ablation technique drastically reduces the complications, sometimes even serious, typical of PEA and radiofrequency ablative treatments which can damage parts of organs that are still functional or even extend into extra-glandular regions. The use of fine needles for treatment reduces pain for the patient and avoids the risks of general anesthesia.

The new laser equipment allows multiple outputs for optical fibers with a partial power delivery system. This allows a multi-focal type treatment to be performed with a single session to ensure a greater volume of the induced lesion.

In the current laser ablation therapeutic procedure, the parameters of the laser treatment (power and duration, duty cycle) are set by the operator before the start based on the ultrasound appearance (B-mode) of the region of interest or other diagnostic information coming from the patient's clinical path. The treatment ends within the previously scheduled times regardless of the actual achievement of the expected result in terms of extension of the necrotized region. Only at a subsequent follow-up evaluation will it be decided whether to proceed with a new treatment to necrotize any residual parts.

Attempts have been made (see US patents 6865412, 7171253) to create systems that provide useful data for treatment with the measurement of the temperature in the tissues carried out by inserting thermocouple sensors. This causes the invasiveness of the technique to increase (more needles to be inserted) and does not guarantee a correct description of the lesion produced because the volume of necrosis is extrapolated from the temperature measurement in some points.

Currently, the ultrasound semblance of the B-Mode image shows its limits for some pathologies (both in the identification and in the typing) and during the treatment difficulties arise in monitoring when the gases developed diffuse into the surrounding tissues creating a fog and cone effect. shadow in the rear area.

To overcome these problems, a series of spectral analysis algorithms of the ultrasound signal have been developed (US6066098, EP1341003, WO2005033738). With these algorithms it is possible to extract quantitative information on the progress of the treatment and act on the laser source in order to manage the treatment during its course. The same part of intervention planning and post-intervention evaluation is enhanced and efficient.

These techniques allow first the identification of the pathology and then the positioning of the applicators and the monitoring of the lesion produced during the treatment itself. Not only that: they can also act as feed-back by controlling and partializing the optical power that comes out of each applicator in order to "model" the destroyed tissue region on the pathological one planned in the intervention. The 3D reconstruction ultrasound techniques allow the prospective evaluation of the pathological area to be treated and therefore can be an aid to the positioning of the needles and to the pre-intervention planning of the treatment.

Summary of the invention

The invention is located in the field of laser therapy and ultrasound diagnostics. According to one aspect, the invention aims to create an innovative apparatus designed to offer the possibility of collecting information before, during and after the treatment and to use them to guide the treatment, in order to obtain the maximum effectiveness of the same. For this purpose, according to some embodiments, the apparatus is equipped with a multiple partializable applicator, whose partialization of the emitted power can give rise to an arbitrary volume of coagulative necrosis.

According to some aspects, the invention proposes equipment that improves the application of minimally invasive laser ablation techniques thanks to the combined use of the laser source and monitoring tools. In these applications, the use of an imaging method for the correct positioning of the laser radiation applicators in the region to be treated and for real-time monitoring of the treatment is extremely important if you want to ensure a high number of procedure successes.

Among the imaging methods currently available, ultrasounds seem to have some important advantages such as ease of use, non-harmfulness for the patient and real-time imaging.

The equipment object of the present invention is born from the fusion of two pre-existing technologies: laser technology and ultrasound technology, which give rise to a new integrated system with joint diagnosis-therapy and monitoring features.

The ultrasound system as well as the laser apparatus feature innovative technical developments implemented specifically for the application of percutaneous laser ablation (PLA: Percutaneous Laser Ablation). Both devices (laser and ultrasound) controlled by a control unit that manages and resets the parameters of both.

According to an embodiment, the invention provides an apparatus comprising:

3⁄4 a laser generator with at least one module for delivering a laser beam <through an optical fiber towards a needle dispenser or the like;>

3⁄4 an ultrasound system capable of producing images of the area of <interest;> in real time

3⁄4 a control unit programmed to execute at least one control algorithm of the percutaneous ablation treatment, based on information obtained from the signal obtained from the ultrasound system.

Preferably the apparatus comprises a plurality of laser modules and a plurality of laser outputs for corresponding optical fibers that can be associated with respective needles or other percutaneous applicators. In this way, a larger volume of tissue can be treated quickly, for example to cause necrosis of large tumor lesions. Furthermore, according to some preferred embodiments of the invention, each laser module can be controlled independently from the others, to modulate the delivered power, or even interrupt the delivery of laser power from one or the other of the needles, depending on the treatment needs, all under the control (manual or automatic) made possible by the combination of the laser sources with the ultrasound equipment, on which an algorithm is implemented to verify the possible occurrence of excessive irradiation conditions for a correct treatment of the tissue.

According to one aspect, the invention relates to a percutaneous laser thermo-ablation apparatus, comprising in combination: a laser device with at least one power supply module and an applicator; an ultrasound device with at least one ultrasound transducer; a monitor; a user interface; a control unit connected to said interface, to said monitor, to said laser device and to said ultrasound device to superimpose on an ultrasound image of the tissue being treated a visual indication representative of the progress of the thermo-ablation process. In some embodiments, the indication is provided by a chromatic map superimposed on the ultrasound image, for example a B-mode image.

When the apparatus comprises a plurality of independent laser delivery modules, each of them can be equipped with at least one applicator. By applicator we mean a generic set of organs suitable for conveying the laser energy from the source contained in the delivery module to the point inside the tissue to be treated. Such applicators generally comprise a waveguide, typically an optical fiber, with a connector to the laser source and a terminal connector, i.e. to the distal zone, through which the fiber or other waveguide is interfaced to an organ that crosses the fabrics guiding the end of the fiber up to the volume of fabric to be treated. This organ is typically a cannula or a patent needle. In the context of the present description, the term needle means any element suitable for guiding the optical fiber from the epidermis towards the interior of the tissue to be treated.

Advantageously, according to some embodiments the applicators comprise a coding system, to distinguish one applicator from the other. Preferably, the applicator needles have differentiated echogenicity characteristics to allow the individual needles to be identified by means of the ultrasound signal. For example, each needle may have a surface processing that alters the ultrasound signal generated by the needle. By working superficially in a different way one needle from the other, it is possible to distinguish the needles. The recognition of the needles can be carried out by the operator who manages the ablation process manually or partially manually. In some particularly advanced and advantageous embodiments of the invention, the control unit is able to recognize the individual needles so as to be able to intervene automatically on the delivery conditions of the individual laser modules based on the information provided by the ultrasound system on the development of the ablation process or more generally on the interaction between laser radiation and tissue. This allows, for example, to automatically choke, i.e. reduce, the power emitted by each individual module to avoid overheating, vaporization and / or carbonization of the treated fabrics. This is in order to avoid the onset of conditions that generate shadow cones in the volume of treated tissue, which can hinder, slow down or completely prevent the treatment of the affected tissue. The use of a plurality of needles also allows to increase the treated volume. It is in fact possible, for example, to modulate the power and / or delivery time of one or the other fiber as a function of the volume to be treated. The control obtainable through the use of the ultrasound probe allows to avoid tissue carbonization and therefore increase the delivery time and / or power without risk of carbonization, consequently increasing the overall volume affected by the laser radiation.

According to some advantageous embodiments, the control unit is programmed to detect through the ultrasound signal a movement generated in the tissue being treated by the heating caused by the laser energy. This detection can be performed with a Doppler Color Flow technique, or Power Doppler or on the basis of other algorithms suitable for detecting the movements caused by the onset of microbubbles or local microcontractions of the tissues being treated, due to the thermal effect. Some of these algorithms will be described below by way of example only, it being understood that the invention is not limited to the methods and algorithms described. On the contrary, it includes any system capable of extracting from an ultrasound signal useful information for determining the conditions of interaction between laser radiation and tissue, in particular information relating to conditions of excessive or correct heating of the tissues.

In general, the control unit of the apparatus of the present invention can be programmed to perform one or more of the following functions through the signal acquired by the ultrasound device: detecting the extent of a pathological tissue to be treated; detect the progress of the tissue treatment during the irradiation of the laser energy; signal a condition of excessive heating of the tissue being treated; modify the conditions of delivery of laser energy according to the heating conditions of the tissue being treated; check the extent of the treated area.

Further advantageous features and embodiments of the apparatus will be described below with reference to some non-limiting embodiments of the invention and are indicated in the attached claims.

Brief description of the drawings

The invention will be better understood by following the description and the attached drawing, which shows practical embodiments of the invention. More specifically, in the drawing they show:

Fig.1 is a block diagram of a device according to the invention;

Fig.2 is an illustrative diagram of the operation of a so-called "wall filter" to extract the signal components due only to the moving parts;

Fig.3 is a representation on a monitor of an ultrasound image with a superimposed chromatic map representative of the movements of the tissue and / or of the bubbles generated in the tissues, obtained by applying the Color Flow algorithm to a laser thermo-ablation treatment;

Fig.4 the temporal evolution of hepatic tissue treatment by laser thermoablation;

Fig.5 is a further diagram of the behavior of a "wall" filter;

Fig.6 an ultrasound image with superimposed chromatic map obtained by using the Power Doppler signal filtered through the filter of Fig.5;

Fig.7 is a block diagram illustrating an algorithm based on the processing of the radiofrequency ultrasonic signal to obtain information on the formation of bubbles in the area where a percutaneous laser thermal ablation is performed; Fig.8 ultrasound traces relating to the same line of sight but acquired at a temporal distance of 30 milliseconds, on which the algorithm of Fig.7 can be applied;

Figures 9 and 10 illustrative block diagrams of further algorithms according to the invention;

Fig.11 the B-mode images of a liver tissue subjected to laser thermo ablation treatment, the same image processed with the system according to the invention and the superimposition of the B-mode image on the image obtained by processing;

Fig. 12 B-mode images and processed with a spectral characterization algorithm to highlight the areas of pathological tissue to be treated before and after treatment by laser thermo ablation; And

Fig. 13 shows the time course of the denaturation of tissues treated by laser thermo ablation, by superimposing a chromatic code on the B-mode image.

Detailed description of forms of implementation of the invention

In summary, according to some embodiments, the apparatus of the present invention <comprises in combination ::>

• A kit of needles for laser thermo-ablation consisting of optical fibers and a guide system for inserting the needles, made for example as described in WO-A-2008/068789. For this purpose, according to a possible embodiment, the invention provides an optical fiber kit for the percutaneous ablative treatment comprising at least two optical fibers, each of which is equipped with a connector to a laser source and, near the distal end of the fiber (from which the laser radiation is emitted), of a binding device to a patent needle or cannula. According to the invention, the fibers of the kit are characterized by a coding system that allows to characterize, in other words to distinguish one fiber from the other. This allows the operator to intervene more quickly when changes to the operating conditions of each fiber must be made, since the various fibers can be more <easily identified.>

• An ultrasound system capable of producing multi-parametric images of the area of interest in real time, equipped with appropriate processing software, described in greater detail below. The real-time representation takes place in composite images, where a color code resulting from data processing is superimposed on a conventional B-Mode image which contains information on the anatomical structures useful for the doctor for positioning the ultrasound probe. This system supports the implementation of spectral analysis algorithms of the RF signal as described in (US6066098, EP1341003, WO2005033738).

The apparatus comprises two different technologies as a whole: the ultrasound technology, which allows in a non-invasive way to produce images in real time of the anatomical parts, and the laser technology which allows the emission of a laser type electromagnetic field ( Light Amplification by Stimolated Emission of Radiation) with the properties of directivity, monochromaticity, coherence.

The ultrasound technology allows to excite a piezoelectric probe which generates an acoustic field that propagates in the underlying tissues. The echo coming from the tissues is received by the same transducer and an electrical signal called Radio Frequency signal is reconstructed for each line of sight. By generating a contiguous series of lines of sight, a two-dimensional image called ultrasound frame is obtained with correspondence between delay time in the received signal and tissue depth considering the constant ultrasound speed. The ultrasound frame can be processed according to different algorithms. The simplest involves the extraction of the envelope, that is, of a signal that follows the crests of the RF signal and is therefore connected to its amplitude. The envelope signal is then used for the realization of B-MODE images. Other types of excitation of the ultrasonic probe that use other physical phenomena for image formation (for example the Doppler effect) provide for the realization of images of different types such as Color Flow, Power Doppler. The ultrasound system has, inside, a series of modules for processing these signals in order to produce parameters and indices useful for controlling the thermo ablation process.

In Fig. 1 the apparatus is schematically represented in the form of a block diagram, indicated as a whole by 2. With 1 is indicated the ultrasound device, interfaced with a control unit 3, in turn equipped with a user interface 5. With 7 a piezoelectric probe connected to the ultrasound device 1 is generally indicated.

The apparatus 2 also comprises a laser device 9 constituted, in this embodiment, by four independent laser modules 11, managed by a digital type electronics incorporated in the control unit 3. The power for each output can vary depending on the example from zero to 10 W in steps of 0.5W. This allows the complete programmability of the system through the interface 5. The Laser system interacts with the ultrasound device 1 through proprietary communication protocols. 13 indicates a monitor connected to the control unit 3, for viewing the ultrasound images and 15 indicates a foot switch. Each laser module 11 is connected to an optical fiber 17 which carries, at its distal end, a connector generally indicated with 19 and a needle 21 for the penetration of the optical fiber into the tissue to be treated. The configuration of the optical fiber, the connector and the needle are known per se (see for example the patent literature cited above) and will not be described in greater detail here.

The four independent laser modules 11 are able to work in two modes: 1. continuous wave: in which the total power of the source is varied

2. pulsed mode: in which the average power is varied by controlling three parameters: peak power; duty cycle and pulse repetition frequency. Through the digital control the treatment parameters can be changed also during the treatment through the interface 5 and this allows to manage the treatment law over time. The treatment law is a curve over time that describes the delivery of both pulsed and continuous power. By changing the law of treatment, different coagulation results are obtained in terms of volume, necrosis and coagulation induced in the tissues.

This system can work in two ways:

1. in full control of the user

2. with ultrasound support and operator supervision

In the first mode, the power and energy data delivered by each fiber during treatment are set by the operator, while in the other mode they are determined by the treatment monitoring system under external supervision.

According to some embodiments, the processing software executed through the control unit 3, or other logical processing unit, is composed of several modules with the following characteristics:

1. software module for evaluating the position and anatomical extension of the lesion to be treated; this module can be realized according to what is described for example in US2003 / 0167003 or in US2006 / 0277998, the content of which is incorporated in the present description;

2. intervention planning software module which gives information to the operator on how to insert the needles and on the energy doses to be delivered for each 3. software module for monitoring the coagulation trend of the tissues during treatment.

This last software module allows to modify (automatically or through the intervention of the operator) the progress of the ablation process, avoiding, for example, the overheating of certain areas of the tissue being treated, so as to prevent the formation of vapors or charred areas that hinder or even prevent the correct continuation of the tissue necrosis process.

In some embodiments, the software module for monitoring the coagulation trend, or other desired process caused by the interaction between laser radiation and tissue, is based on an algorithm that processes the Doppler signal.

The Doppler signal from the treatment region is closely correlated with the thermal agitation of the tissues and the formation of gaseous microbubbles, which are generated by excessive heating of the tissue region with subsequent evaporation of cellular and intercellular liquids. The dehydration of the tissues produced by excessive heating can even cause tissue carbonization, which limits the transmission of laser radiation to the surrounding regions, thus limiting the effectiveness of the treatment.

The control algorithm, therefore, processes the Doppler signal from the region of interest and produces an index of the presence and / or formation of gaseous microbubbles and thermal agitation of the tissues. This indication is then used by the control unit 3 to control the power emitted by each applicator 17, 19, 21, therefore by each module 11. In a technologically advanced version of the control system, the segmentation of the ultrasound image with relative Doppler content in distinct portions based on the location of the applicators. This allows each module 11 to be managed individually by reducing - if necessary - the power emitted. In other simpler but less advantageous embodiments, the software can limit itself to generating an image superimposed on the ultrasound image on the monitor 13, so that the operator can intervene manually to reduce the power emitted by one or the other of the modules. 11, or to completely stop the emission, for example by zeroing the power transmitted to the fiber concerned or simply by disconnecting the relative optical fiber 17 from the laser module 11. For this purpose, the individual applicators (17, 19, 21) can have a system of coding to quickly identify which of the individual applicators requires a partialization intervention, that is, a reduction in the delivered power, or interruption of the delivery. Examples of coding systems for this purpose are described for example in WO-A-2008/068789, the content of which is incorporated in the present description.

A possible algorithm that uses the Doppler signal to highlight the onset of microbubble generation phenomena is described below.

The technique used is that of Color Flow which uses correlation algorithms between ultrasonic signals. This technique employs a sequence of pulses for each line of sight by which changes between two successive ultrasound traces are detected. In stationary conditions there are no variations between two ultrasound signals for the same line of sight over time and therefore no signal is detected. In conditions of tissue movement there is a net signal useful for the formation of the Color Flow (CF) image. The techniques proposed in the literature are many, such as that of Namekawa et al. "Real-time bloodflow imaging system utilizing auto-correlation techniques", in Ultrasound'82 Eds LA Lersky, PMorley, Pergamon, New York (1982), Kasai et al. "Realtime two-dimensional blood flow imaging using an autocorrelation technique", in IEEE Trans. Sonics Ultrasonic SU-32, 458-464 (1985).

In reality, however, the ultrasound signals are affected by a noise called “clutter noise” due to the physiological movement of the tissues or to movements of the probe. This noise must be removed in order to produce CF images consistent with the movements of the tissues produced by the development of heat.

Some techniques for the removal of clutter noise are reported in the literature, for example in P.A. Magnin “A review of Doppler flow mapping techniques,”, in IEEE Ultras. Symp, vol. 2, pp. 969-977, 1987. Most of them employ a filter called wall filter that operates in the Doppler domain and removes the signal components from the clutter noise. The operation of the "wall filter" is schematically represented in Fig.2.

The result of applying the Color Flow algorithm to the laser thermo ablation treatment is shown in Fig.3. The image shown in this figure is obtained when the measurement apparatus is set with high amplification gains (High measurement sensitivity). The hot scale (shades of red) represents the speed map of the points approaching the probe while the cold map (shades of blue) represents the speed scale of the points moving away from the probe. The mosaic of colors that can be seen superimposed on the B-Mode image is the result of the application of CF to the area subject to PLA treatment.

In this area, the development of heat inside the tissues due to the absorption of laser radiation by the same produces movement of the tissues with the formation of gaseous microbubbles if the temperature is too high. Microbubbles spread to neighboring tissues. For this reason there is no privileged direction of movement of the tissues (the predominance of red or blue color is not observed), but only a certain thermal agitation which results in a speckled map of red and blue colors in the image. CF.

The CF algorithm is revised in some parts and adapted to the case of tissue ablation. The conventional CF signal is generally used in the cardiovascular field and is a signal coming from vessels (a very low signal in amplitude). The ultrasound system processes this signal within a range of well-known amplitude and adapted to that type of application. On the other hand, in the case of laser thermo ablation, the signals that develop during the treatment (especially if in the presence of gas formation) are very large and therefore the whole reception chain (including the analog part) must be reviewed and adapted to these new intervals. signal.

Fig. 4 shows a sequence of ultrasound images in CF mode extracted during an entire PLA treatment. Note the colored areas that indicate thermal agitation of the tissues with the formation of gas microbubbles. More specifically, the images refer to liver tissue subject to PLA treatment. In the initial stages, the Doppler Color Flow signal indicates the formation of gaseous microbubbles and thermal agitation of the tissues. When the Doppler CF signal ceases, it means that the treatment has reached its final stage for that portion of tissue.

According to other embodiments, the software module for monitoring the progress of the tissue coagulation treatment uses a different ultrasound signal, namely the Power Doppler signal.

In fact, the Power Doppler signal also contains useful information for monitoring the treatment of PLA. In the Power Doppler technique, the intensity of the chromatic scale superimposed on the B-Mode image is linked to the amplitude of the Doppler signal that is let through by the wall filter regardless of the Doppler shift it possesses. In this technique the speed helps to separate the contributions between the still tissues and those put in thermal agitation, but the chromatic result depends on the intensity of the signal and not on its position in the doppler frequency.

Fig.5 shows the representation of the Wall filter in this case and Fig.6 the B-mode image with the chromatic map obtained from the Power Doppler signal filtered with the aforementioned Wall filter superimposed.

A third algorithm has been developed to highlight the areas in which the alteration is induced during the treatment. This algorithm is based on a multi-pulse technique and more precisely on the processing of the RF ultrasonic signal and is described in the flow chart of Fig.7.

The Subtraction module performs a point-by-point subtraction on the RF signal (in general this operation will be filtering over time). The absolute value module performs an amplitude extraction (with a straightening operation or an envelope operation). The next module performs a spatial smoothing on the image through a sliding window operation and finally a thresholding according to a threshold of an appropriate value. The image that comes out of this last module is ready to be displayed through an overlay operation with the relative B-Mode.

Fig. 8 shows, in the upper diagram, two ultrasound traces relating to the same line of sight, but acquired at a temporal distance of 30 ms. The difference signal for the same two ultrasound traces is shown in the lower diagram of Fig. 8.

In a possible embodiment, the algorithm can be implemented as follows: considered a sequence of ultrasound frames coming from a temporal acquisition during the treatment, the subtraction of two contiguous RF ultrasound frames is performed. The resulting signal is different from zero when there has been a relative movement between the ultrasound signals and a new signal linked to the phase difference is produced in this condition. The proposed algorithm determines the elimination of the parts of the signal in which there has been no movement (areas not affected by the heat treatment) while the parts in relative movement (thermal agitation, heating, formation of micro-bubbles that perfuse the tissues) are self-enhanced. giving rise to a clear signal. A parameter of interest that can be extracted from this new signal is undoubtedly the amplitude that provides information on the intensity of the phenomenon produced. In order to extract this information, an absolute value or envelope operation can be used. In Fig. 9 the algorithm just described is schematically represented. Subsequent pairs of ultrasound frames are subtracted from each other to obtain, from a sequence of RF ultrasound frames, a sequence of subtracted frames.

In a broader generalization, more than two successive frames can also be considered. In this case, one can think of optimizing the high-pass filter by moving its cut-off frequency to higher values (the subtraction in the case of two successive frames is nothing more than a high-pass filtering with two coefficients) so that also the slower movements of the tissues (due for example to the movement of the heartbeat) can be rejected and do not produce artifacts on the final image. The filter can be schematically represented as in Fig. 10, where the filter coefficients are indicated with h0, h1, h2, hk

In Fig. 11, relating to a thermoablation treatment on the liver, the lesion produced by the treatment is evident in the B-Mode image (left). On the right is the result of the processing with the areas of fabric subject to thermal alteration and the formation of micro-bubbles of steam. Below the final image with the superimposition of a color code on the B-Mode image.

In addition to the three software modules mentioned above, the device may have a fourth software module for evaluating the actual outcome of the treatment. This module can be based, like the first, on algorithms of the type described in US2003 / 0167003 or in US2006 / 0277998. This software performs spectral processing of the RF signal and produces composite images with indications on the tissue structure. In this application it can work in two modes.

In other embodiments, the software modules can be three. In fact, the spectral analysis algorithm of the radio frequency ultrasonic signal, thanks to its ability to characterize tissues, can be used for different purposes, before, during and after treatment. First, to identify the pathology and position the needles, during to evaluate the development of necrosis and the destruction of the pathology and after treatment to evaluate the actual necrosis produced in the hours following the treatment.

The first method is to identify the tissue to be treated before starting the treatment. In this mode, the indication of the effectiveness of the ablative treatment is provided to the doctor by the disappearance of the color code indicating the pathology to be treated. This modality is particularly useful in the case in which the pathology is very extensive and more treatments are needed to cover the desired volume (Evaluation by image negative). Fig. 12 shows a thyroid pathology (thyroid goiter) undergoing a treatment of PLA. Before starting the treatment, the software highlights the Goiter tissue to be eliminated. In the upper left image the B-mode image of the tissue is represented and in the right image the same image is represented with overlapping of the color map obtained with the software in question, which highlights the presence of the pathological tissue to be eliminated.

In the lower image of Fig. 12, obtained after laser ablation treatment, we note the formation of previously absent ultrasound patterns and the lack of the pattern that signals the pathological anatomical structure. This allows us to conclude that the entire pathology was altered by the heat treatment.

The same software module can be used with a different selection of processing parameters, appropriately selected to highlight the treated tissue (dehydration / coagulation / necrosis), that is, the alteration of the tissue induced by temperature. In this mode, the result of the processing is a color code that follows the denaturation of the tissues during and after the treatment. Fig. 13 shows the temporal evolution of the necrosis treatment through a sequence of three B-mode ultrasound images on which a chromatic code indicative of the coagulated tissue is superimposed. This increases as the treatment progresses.

The three images relate to three successive time instants for the same thermal ablation treatment (in vitro). The color code, relating to a very precise configuration of parameters of the spectral analysis algorithm, represents a tissue altered by the treatment (coagulated) in which there is also the formation of vapor which gives rise to an ultrasound pattern that is however very precise.

Furthermore, the same algorithm can be used (in a different parameter configuration) a few minutes after the end of the treatment to evaluate the actual area of necrosis once the vapors have been reabsorbed into the tissues due to the draining effect of the microcirculation. (in "in vivo" treatments the body's ability to reabsorb the vapor microbubbles produced is undoubtedly increased, facilitating their monitoring)

The same algorithm in a different configuration of its parameters can follow the trend of tissue coagulation in the event that the partialization of the power or the use of particular types of optical diffusers prevent the vaporization of the tissues.

Claims (11)

Method and device for ultrasound treatment and monitoring by percuteal laser ablation Claims 1. A percutaneous laser thermo-ablation apparatus, comprising in combination: a laser device with at least one power delivery module and an applicator; an ultrasound device with at least one ultrasound transducer; a monitor; a user interface; a control unit connected to said interface, to said monitor, to said laser device and to said ultrasound device to superimpose on an ultrasound image of the tissue being treated a visual indication representative of the progress of the thermo-ablation process. 2. Apparatus as per claim 1, wherein said visual indication comprises a chromatic map. 3. Apparatus as per claim 1 or 2, wherein said laser device comprises a plurality of independent laser delivery modules, each equipped with at least one applicator. 4. Apparatus as per claim 3, wherein said applicators comprise a coding system, to distinguish one applicator from the other. 5. Apparatus as per claim 4, in which said applicators each comprise a needle and in which said needles have characteristics of differentiated echogenicity to allow the individual needles to be identified by means of the ultrasound signal. 6. Apparatus as per claim 5, in which said control unit is programmed to modify the emission conditions of each module according to the progress of the thermo-ablation process, identifying each individual applicator on the basis of the characteristics of differentiated echogenicity. 7. Apparatus according to one or more of the preceding claims, in which said control unit is programmed to execute an algorithm for monitoring the progress of the interaction process between laser energy and tissue. 8. Apparatus according to claim 7, wherein said control unit is programmed to detect through the ultrasound signal a movement generated in the tissue being treated by the heating caused by the laser energy. 9. Apparatus as per claim 8, in which said control unit is programmed to detect, through the ultrasound signal, the generation of microbubbles and / or microcontractions in the tissue being treated. 10. Apparatus according to one or more of the preceding claims, in which said control unit is programmed to perform one or more of the following functions by means of the signal acquired by the ultrasound device: detecting the extent of a pathological tissue to be treated; detect the progress of the tissue treatment during the irradiation of the laser energy; signal a condition of excessive heating of the tissue being treated; modify the conditions of delivery of laser energy according to the heating conditions of the tissue being treated; check the extent of the treated area. 11. Apparatus according to one or more of the preceding claims, in which said control unit is programmed to monitor the progress of the interaction between the tissue being treated and the laser radiation, providing an alarm signal when an excessive generation is detected in the tissue microbubbles and / or microcontractions.