HK1031679A - Method and device for supply of heat - Google Patents

Description

Method and device for supplying heat

The present invention relates to a device for supplying heat to body tissue according to the preamble of claim 1.

In certain conditions caused by disease, including unnatural hyperplasia of tissue, treatment with heat after treatment is more effective. The tissue may be heated to the point where it dies. Examples of such disease states are: certain types of cancer and Benign Prostatic Hypertrophy (BPH). When treatment is performed, certain portions of the tissue are heated so that tissue death occurs, while other portions of the tissue must or should be protected. The disease states discussed herein are primarily focused on disease states that arise in the tissue surrounding various cavities within the body. As examples of such diseases, in addition to the above-mentioned diseases, esophageal cancer, tracheal cancer, urethral cancer and intestinal cancer may be mentioned.

Corresponding disease states may also arise in animals, and the same treatment may be used. In particular, the treatment of domestic animals such as dogs can become a subject.

Different devices can be used to generate heat, commonly used are: laser, microwave and radio frequency antennas. In addition, a method of inserting a container containing a liquid into a body cavity is also known. The liquid expands the container and thus a good contact with the surrounding tissue can be obtained. The liquid may be heated by supplying hot liquid through a circulation system; or by supplying energy to a heating device within the container, from which heat is transferred in some way to the liquid and subsequently to the tissue.

Since the volume of tissue to be treated, and the heat absorption capacity of that tissue and the tissue adjacent to it that does not need to be treated, varies, it should be monitored continuously during the treatment. When the treatment is performed, the body tissue is heated. For best therapeutic effect, the heating should be within a certain temperature range. Too high a temperature may cause unnecessary excessive damage to the tissue; and too low a temperature may not achieve the desired therapeutic effect.

It is common practice to install some form of temperature sensor in the heating device, arranged on the induction heating element, in order to monitor the temperature of the adjacent tissue. A disadvantage of this arrangement is that the temperature sensor gives more information about the temperature of the element than about the temperature of the tissue.

An example of such a form of heating device is shown and described in EP 0370890. The device encloses a catheter that is housed in a microwave antenna that transmits radio energy to the tissue surrounding the antenna. The catheter is also provided with a cooling channel for cooling the tissue closest to the catheter. In the conduit, a temperature sensor is mounted which reads a temperature value of the conduit. Thus, the detected temperature is not consistent with the temperature of the tissue to be treated.

PCT/SE96/00649 shows and describes a more advanced temperature sensing method. In order to be able to directly record the temperature increase in the tissue to be treated, a first temperature detection instrument according to PCT/SE96/00649 is connected to a first carrier. The carrier passes through a passage in the conduit and is designed to extend through an opening in the conduit. In the opening of the catheter, a control device of the carrier is arranged to introduce the carrier into the tissue at a desired angle relative to the catheter. The treatment with the above-described microwave device is commonly referred to as JUMT (transurethral microwave thermotherapy).

Either the carrier or the temperature sensing device is provided with a pointed end to penetrate into the tissue. Typically, the temperature sensing device may be a resistive sensor or a semiconductor. The cables required for this form of sensor pass through the conduit. If an optical sensor is used, an optical fiber guide is placed through the channel of the catheter.

Using the above-described devices and other known techniques, the attending physician can generally determine the duration and temperature of the treatment. Although temperature can be continuously measured, there are problems in ensuring satisfactory treatment results during the course of treatment, as a course of treatment may take weeks or months. In addition, it is difficult to adapt the treatment to new conditions, such as pain, and to judge how to adapt the treatment to the current physical condition of the patient during the course of treatment.

It is an object of the present invention to provide a device for supplying heat to body tissue which substantially overcomes the above-mentioned disadvantages. This object of the invention is achieved by the features of claims 1-10.

According to the invention, it is possible to regulate the heating in advance in different ways and to better predict the result. The device of the present invention can be used to calculate the temperature distribution throughout the prostate based on information measured at certain points inside the prostate and information on the distribution of energy absorption by body tissue from one or more energy sources. The temperature profile may be determined from the relationship between the temperature in the tissue, and the absorbed energy, blood flow and thermal conduction. By continuously measuring the temperature and the time of heating, and by continuously monitoring the relationship between the temperature profile and the information on the survival of cells exposed to heat, the amount of tissue destroyed at certain points in time during the exposure to heat can be determined.

In a preferred embodiment, the temperature distribution and the destruction of the tissue are displayed continuously in the form of images and documents on a display device; thus, the doctor can constantly understand the situation of the current treatment. Heat is supplied to the tissue until the regulated portion of the tissue is destroyed.

Other advantages and features of the present invention will become apparent from the following description, the accompanying drawings and the appended claims.

The invention will now be described in detail by means of specific embodiments with reference to the accompanying drawings.

FIG. 1 is a longitudinal cross-sectional view of a catheter for treatment that may be placed in an apparatus according to an embodiment of the present invention;

fig. 2 is a basic block diagram illustrating an apparatus according to an embodiment of the present invention.

As shown in fig. 1, a catheter 12 for treatment is inserted into the urethra such that a tip 23 penetrates into the bladder 28. A bladder or balloon 29 connected to the catheter 12 for treatment is inflated in the bladder 28 to prevent inadvertent withdrawal of the catheter for treatment during the course of treatment. Thus, the active part of the catheter for treatment is located in the center of the tissue to be treated, in this case the prostate 31. The catheter 12 for treatment is flexible and flexible in order to be inserted through the urethra to the treatment site.

The container 19 shown in figure 1 is expanded to its working volume by a liquid 20 introduced into it under pressure. According to the embodiment shown in fig. 1, the container 19 is pear-shaped in the longitudinal direction of the catheter for treatment, the section of which facing the bladder is larger; or the container 19 is relatively symmetrical in the axial direction. The shape of the receptacle 19 conforms to or can match the shape of this portion of the urethra. The container 19 is located outside the catheter for treatment and suitably a larger part of the catheter 19 is located on the underside of the catheter for treatment. When the container 19 is inflated, the catheter for treatment is lifted upwards, which in the body means that the distance between the heating device 10 located in the container 19 and the rectum increases. The liquid 20 passes through a channel 22 designed as a tube which passes through the catheter for treatment.

In order to be able to track the temperature changes in the tissue during the heating treatment, a first temperature sensor 11 is arranged on a carrier 24. The carrier 24 is designed to be advanced through a passage or tube 25 through the catheter for treatment. The carrier 24 or the temperature sensor 11 is preferably provided with a tip which can locally penetrate the membrane or wall of the catheter for treatment and can locally penetrate the tissue. The tube 25 is configured so that the carrier 24 with the temperature sensor 11 passes out of the catheter for treatment at a suitable angle and can extend radially from the catheter for treatment a suitable distance. In order to provide a suitable inclination of the temperature sensor 11, it is also possible to provide a specific angle of the instrument on the terminal section of the tube 25. The catheter 12 for treatment may also be provided with another temperature sensor 30. Temperature information in the tissue near the container 19 or very near the catheter 12 for treatment may be obtained from the second temperature sensor 30. In the embodiment shown in fig. 1 and 2, the device according to the invention may also be provided with a third temperature sensor 34. The third temperature sensor 34 is preferably located on the carrier 24 between the first temperature sensor 11 and the second temperature sensor 30, so that the temperature at a distance from the catheter 12 for treatment can be continuously measured.

There is also a fluid passage 26 within the catheter for treatment. Which leads to the above-mentioned balloon 29; when the catheter for treatment is inserted in place, fluid can pass through the fluid passage into the balloon 29 to inflate the balloon. The fluid channel 26 may also be used to evacuate the balloon 29 at the end of the treatment and before the catheter used for the treatment is withdrawn from the urethra. Preferably, a conventional syringe or similar device is used to inject the fluid into the balloon 29 and to evacuate the balloon 29.

As a result of the heat loss, the supply cable 21, which connects the heating device 10 with an energy source, is heated. To avoid damaging tissue outside the treatment area, e.g., the sphincter surrounding the urethra outside the prostate, the supply cable 21 is cooled. This may be done by providing a cooling channel within the catheter 12 for treatment, preferably around the supply cable 21. In one embodiment of the invention, the cooling channel has a limiting wall that returns the cooling liquid circulating therein. In this way, cooling of the heating device 10 itself can be avoided, which in turn means that less energy needs to be supplied from the energy supply assembly 13. When the energy level is lower, the risk of improper treatment and damage to healthy tissue is reduced.

Thus, by heating the liquid in the container which radiates heat directly to the adjacent tissue, the tissue which is at a close distance from the catheter for treatment can be locally heated; tissue at a greater distance from the catheter for treatment can be locally heated by electromagnetic radiation. The total treatment area with this heating method is larger than with the usual heating method, which means that a larger piece of tissue can be treated.

At high temperatures of 90 ℃ to 150 ℃, the tissue hardens and forms a crust. The hard shell can prevent or reduce problems caused by prostate swelling due to treatment. Since the temperature is highest in the tissue closest to the reservoir 19, the portion of the urethra that passes through the prostate at the treatment zone will be most affected and damaged. However, this portion of the urethra recovers relatively quickly.

In a preferred embodiment of the invention, the heating device 10 comprises a microwave antenna. The microwave antenna is very well suited to the tissue, since the urethra is completely filled in the treatment area without free space. The liquid in the container 19 should be selected such that: i.e. the liquid has substantially or exactly the same properties as the prostate tissue for the propagation of microwaves. The impedance matching between the microwave antenna and the tissue is also very good, which may reduce the size of the microwave antenna and the energy supply assembly and facilitate the regulation of the microwave energy.

When the treatment is over, the supply of energy to the heating means 10 is stopped, at which point the container can be emptied and returned to normal body temperature. As long as the container 19 has such a temperature that it will cause damage when it passes through the body, it is not appropriate to remove the catheter for treatment. Therefore, the temperature of the container 19 must be continuously monitored and once the desired temperature is reached, the catheter for treatment can be withdrawn.

In the case of treatment involving the prostate or the bladder, since the catheter for treatment 12 having a tip is inserted into the bladder 28, urine and possibly other liquids can be discharged through a discharge channel provided in the catheter for treatment 12. The drainage channel runs the entire length of the catheter 12 for treatment and has an opening 27 at its end adjacent to the catheter 12 for treatment. For certain types of treatment, the catheter 12 may be suitably left in the body for a period of time after treatment. At this point, urine and other fluids may be expelled from the bladder through the drainage channel.

The treated and dead tissue can be reabsorbed or rejected and disposed of with the urine. A cavity in the prostate created by the removal of tissue ensures the passage of urine. The cavity has a shape at the beginning corresponding to the shape of the container 19 at the time of treatment.

In addition to, or as part of, the heat treatment method described above, a number of drugs may be added to the container 19. In this case, the liquid container 19 is modified so that the medicine can pass through. Preferably, the reservoir 19 is configured to allow diffusion of the drug through the walls of the reservoir 19; however, weep channels or the like may also be provided in the container wall. According to one treatment method, an analgesic may be added to the liquid. Other drugs that have a direct therapeutic effect may also be used.

According to another embodiment of the invention, the container 19 may be absent. In this embodiment, direct heating may be provided by the heating device 10, in which case the heating device is arranged to radiate energy that can be absorbed by the tissue. Preferably, the heating device 10 comprises an antenna, by means of which the microwave radiation of the heating device is utilized. Lasers and other forms of radiation sources may also be used.

Fig. 2 shows a block diagram schematically illustrating different functional blocks comprised in a treatment device with a catheter for treatment according to the invention. As described above, the heating apparatus 10 is powered by the power supply assembly 13. The central control unit 14 is connected to the power supply unit 13, a display unit 33 and a liquid supply device 32. In addition, the control unit 14 is connected to an input device in the form of a keyboard 16. The control assembly 14, keyboard 16 and display assembly 33 may also be included in a typical computer with a monitor and keyboard.

For TUMT treatment and similar treatments, the temperature of the tissue is largely determined by three different processes, namely: (i) generating heat by absorbing microwave energy or another radiant energy source; (ii) heat distribution due to thermal conduction of tissue; and (iii) caused by blood flowHeat loss of (2). The parameters of the treatment apparatus (i) are determined by the catheter being used for treatment; (ii) is calculable; and (iii) is patient dependent and unknown. The relationship of the parameters can be given by the well-known biological thermal equation:

in the formula: rho (kg. m)^-3) Is the density of the prostate; c (Jkg)^-1K^-1) Specific heat of the prostate; t (. degree. C.) is the prostate temperature at time T (seconds); lambda (Wm)^-1K^-1) Is the thermal conductivity of the prostate; Δ is the laplace operator; omega_bIs the perfusion rate (m) of the tissue³kg^-1s^-1)；ρ_b(kg.m^-3) Is the density of the blood; c. C_b(Jkg^-1K^-1) Is the specific heat of blood; t is_aIs arterial temperature (. degree. C.); q_s(Wm^-3) Heat generated for absorbing microwaves; and Q_m(Wm^-3) Is the heat generated by the metabolism. During heat treatment Q_mThe items may be ignored. The thermal properties of prostate tissue can be calculated from its water content, which is assumed to be 80%. The equations and corresponding data may be stored in memory 15 so that the equations may be solved continuously during heating.

Since it can be assumed that the absorption of the microwave is symmetric in the radial direction, cylindrical geometry can be used for the numerical solution of equation (1). The equation can be solved using finite difference methods. Q in equation (1)_sTerms may be determined using the specific absorption rate (SAR, W/kg) in a certain catheter 12 for treatment. One practical way to determine the specific absorption rate is to place a TUMT catheter in a tissue-like body, for example made of TX-150 material, and then measure the temperature distribution in the body after 60 seconds of heating with microwaves at 50W output. One method for measuring SAR is described in detail in "journal of urology in England" stage 78 (1996), page 564-.

In a first memory 15 with appropriate equations and dataA table or similar form stores some known data regarding cell survival at different cell temperatures during different durations of treatment. The first memory 15 is formed so that the stored data can be supplemented; and, if necessary, corrections can also be made to the data as new results of treatment are collected. The tissue damage caused by this procedure can be described mathematically according to the following Arrhenius equation:

in the formula: Ω is the cumulative damage to the tissue during the treatment time t; a is an Alinies constant (3.1X 10)⁹⁸S^-1) (ii) a Ea is the activation energy of the cell (6.3X 10)⁵Jmol^-1)；R(Jmol^-1K^-1) Is the universal gas constant; and T (k) is the temperature of the tissue. It is assumed that when Ω ≧ 1, the tissue is destroyed.

A suitable measure is to collect data at regular intervals after treatment, for example monthly over a period of time. In the first memory 15, data is stored of blood flow and other factors affecting the heat absorption and dissipation of the tissue being treated. With these accurate data, information that can form a model of the tissue in close proximity to the actual tissue relative to the various factors described above can be stored in the memory 15. Preferably, the data is continuously supplemented and modified after treatment has been performed.

Prior to the heat treatment, several current physical factors are determined, such as the size of the prostate, the degree of narrowing of the prostate, and the distance between the prostate and the rectum. With this information of the body state, the appropriate catheter form for treatment and the appropriate treatment temperature can be determined. Instead of the duration of the treatment, which is a decisive factor according to previous devices, the value of volume/weight required for the tissue to be treated to reach destruction can be determined. The volume/weight value is set so that the control assembly 14 can use, for example, input the value via an input device. Preferably, the highest temperature value, or the average value of the treatment temperature, or a temperature range is also given. The device may also be provided with reservoirs for storing the above-mentioned volume/weight and treatment temperature combinations. In this case, the standard value of the treatment temperature can be automatically selected.

If a catheter of this type is used for treatment, the control unit 14, after these inputs, initiates treatment by feeding liquid into the reservoir 19 and subsequently sends a control signal to the energy supply unit 13 to initiate the heating device 10 to emit energy to heat the tissue to be treated. The liquid supply 32 may be used when the container 19 is to be filled and inflated. The control assembly 14 may control the filling of the container 19 so that the pressure and associated compression of the prostate tissue is appropriately increased. The above-mentioned first temperature sensor 11, and preferably also the second temperature sensor 30 and the third temperature sensor 34, provide continuous information about the current treatment temperature in the treated tissue in the vicinity of the heating device 10 and at a distance from the heating device.

The control unit 14 is connected to the temperature sensor 11 and preferably to the temperature sensors 30 and 34 and controls the energy supply unit 13 in accordance with the current temperature of the treatment area so that a suitable output is provided to the heating device 10. In this way, the temperature of the liquid container 19, and thus of the surrounding tissue, can be raised reliably and very safely, so that the treated tissue dies in the desired manner. The temperature data from the temperature sensors 11 and 30 may be continuously displayed on the display assembly 33. The amount of output energy of the heating device 10 can also be indicated by means of the input device 16, or it can be derived from the energy supply assembly 13. The amount of this output energy affects the temperature received by the tissue and, in some cases, also the level of pain experienced by the patient.

A computing instrument 17 continuously compares the data from the temperature sensors 11, 30 and 34 with the data stored in the first memory 15 and in this way the control unit 14 can continuously calculate the temperature changes in the prostate tissue at different distances from the catheter 12 for treatment. The calculating instrument 17 can also in this way continuously calculate the volume/weight of the tissue that has been treated in the desired manner and judge the desired treatment effect that has been achieved in this tissue.

The calculated information is continuously sent to the display module 33, so that the doctor can see the image of the progress of the treatment, in addition to the numerical data relating to the volume/weight of the treated tissue. One suitable method is to display an image similar to that shown in fig. 1 on a display device. Preferably, data concerning the prostate to be treated is suitably collected beforehand, using for example X-rays, ultrasound or MR, so that the image displayed on the display unit 33 corresponds to the actual situation. Preferably, an image corresponding to the catheter to be used for the treatment is superimposed on the image of the tissue.

The temperature of different parts of the prostate tissue can be calculated continuously from the measured temperatures and the current temperature is shown in the prostate image, for example with a marker of a different color. At the same time, different graphs and/or tables are displayed regarding temperature, blood flow and volume/weight of the treated tissue. In this way, the physician can track the course of treatment and continuously obtain information as to how much tissue has been treated and which portion of the prostate tissue has died.

A timer 18 connected to the control unit 14 continuously sends out time information to correlate the measured data with the treatment time. When one of the volume/weight values of the treated tissue calculated by the calculating instrument 17 coincides with the preset value, the treatment is automatically interrupted. With the display device or another display device, it may alternatively be displayed that the set value has been reached; in this way, the doctor can interrupt the heating. If the measured or calculated temperature of a certain portion of the tissue exceeds a threshold value, or other input data, such as the temperature in the rectum or bladder, indicates that there is a risk to the patient, a corresponding interrupt or display may be performed.

It is also possible to change certain set points during the treatment, such as the desired treatment temperature or the microwave input, without affecting or needing to change the set volume/weight value of the treated tissue. Instead, the duration of treatment is affected. The duration of the treatment can be varied considerably in accordance with individual physiological differences, without decisively influencing the outcome of the treatment, in comparison with previously used treatment methods.

The container 19 is completely closed and contains a quantity of liquid 20 with suitable heat transfer characteristics. Examples of such liquids are silicone oils and water. The container 19 is made of elastic silicon or other material, such as latex, with corresponding elastic properties. The catheter 12 and balloon 29 for treatment may also be made of silicon or similar materials.

Claims (14)

1. An apparatus for supplying heat to body tissue, the apparatus comprising a heating device (10) and a first temperature sensor (11) insertable into the body tissue, the heating device (10) being connected to an energy supply unit (13) controlled by a control unit (14) via a catheter (12) insertable into a body cavity for treatment, said first temperature sensor (11) being connected to the control unit (14), characterized in that:

said control unit (14) being connected to a first memory device (15) for storing data corresponding to the survival of cells as a function of cell temperature and time;

an input device (16) is connected to the control assembly (14) for inputting data such as the volume/weight of desired body tissue to which heat is to be supplied to cause tissue cell death;

the control unit (14) is also connected to a computing device (17) for determining the volume and weight of such body tissue whose cells die as a function of the temperature in the tissue at a distance from the heating device (10).

2. Device according to claim 1, characterized in that the control unit (14) is connected to a time measuring device (18) for continuously determining the point in time at which the tissue at a distance from the heating device (10) reaches a certain temperature.

3. A device as claimed in claim 1, characterized in that the first memory means (15) are designed to store data from a certain body tissue concerning the heat-dissipating capacity of the tissue.

4. The device according to claim 1, characterized in that said first temperature sensor (11) is insertable through and into the tissue to which heat is to be supplied.

5. Device according to claim 1, characterized in that a second temperature sensor (30) for measuring the temperature in the tissue close to the catheter (12) for treatment is provided in the vicinity of the heating device (10).

6. Device according to claim 5, characterized in that the third temperature sensor (34) is designed to be passed through and inserted in the tissue into which heat is to be supplied at a distance from the catheter (12) for treatment and is located between the first temperature sensor (11) and the second temperature sensor (30).

7. Device according to claim 1, characterized in that the heating device (10) comprises a microwave antenna for heating the surrounding tissue.

8. Device according to claim 7, characterized in that the heating means (10) are located in a container (19) containing a liquid (20) for heating said liquid (20) and surrounding tissue.

9. The apparatus of claim 2,

the control unit (14) is connected to a display unit (33) for displaying the temperature in different parts of the tissue to be treated; and

the calculation means (17) are intended to determine the displayed temperature from the signal coming from the first temperature sensor (11) and by means of a calculation based on the variation over time of the temperature of the tissue in which the first temperature sensor (11) is inserted.

10. A method for supplying heat to body tissue by means of a heating device (10) and a first temperature sensor (11) insertable into the body tissue, the heating device (10) being connected to an energy supply unit (13) controlled by a control unit (14) via a catheter (12) insertable into a body cavity for treatment, said first temperature sensor (11) being connected to the control unit (14); the method is characterized in that:

the temperature distribution in the body tissue is determined from the measured temperature information in the tissue and the distribution information of the energy absorption in the tissue;

measuring the time of heat supply to the tissue;

calculating the amount of tissue destroyed by energy absorption based on the measured time and the determined temperature profile; and

when the damaged body tissue reaches the required amount, the heat supply is stopped.

11. A method of supplying heat as claimed in claim 10, wherein:

the images of the body tissue are successively displayed on a display unit (33); and

the temperature distribution in the tissue is continuously calculated and displayed on the displayed image.

12. A method of providing heat according to claim 11 wherein the temperature in any tissue outside the treatment area exceeding a predetermined value is indicated by an alarm signal.

13. A method of supplying heat according to claim 12, wherein the temperature in the tissue outside the treatment region exceeding a predetermined value causes the control unit to automatically interrupt the supply of heat.

14. A method of supplying heat as claimed in claim 10, wherein:

data corresponding to the survival of the cells is stored in a first memory (15) connected to the control unit (14), the survival of the cells varying with the temperature and time of the cells;

inputting data corresponding to the volume and weight of the desired body tissue heated to cell death of the tissue into an input device (16) connected to the control assembly (14); and

the values corresponding to the volume and weight of the body tissue, the cells of which die as the temperature in the tissue at a distance from the heating device (10) changes, are determined in a computing device (17) connected to the control unit (14).