Patent Application
20090069876
The present invention relates in general to application of thermal energy to tissues in percutaneous surgery and endoluminal therapy. More particularly the present invention relates to devices for thermally treating tissues providing for contact heating and/or cooling the tissue by means of fluids.
Devices used for treating interstitial tissues thermally (e.g., thermotherapy, tissue coagulation and ablation) operate employing direct electrical heating, irradiating with ultrasonic radiation, or electromagnetic radiation in the frequency ranges of radio frequency or microwave, or by laser during percutaneous surgery are known in the art. The heat transferred to the targeted tissue in such processes must compensate for the accumulated rates of competing dissipation processes of heat transferred to surrounding layers or tissues. Excessive heating power may lead to undesirable boiling of fluids and/or charring of the targeted tissue. On the other hand, insufficient heat will not produce the desired results of coagulation, tissue forming and/or ablation. Typically such treatments are considerably painful for the patient, requiring him/her to remain motionless for a long period and therefore involve general anesthesia.
Therefore a method and system providing for thermal treatment during percutaneous surgery and/or endoluminal therapy, in which the treated tissue is homogeneously heated and/or cooled such that hot/cold spots are respectively avoided; that necessitate only local anesthesia; do not require an infrastructure such as normally present in operating rooms; can be conducted in doctors' clinics, and therefore are more convenient to the patient as well as to the surgeon are called for.
In accordance with the present invention a system and method for thermally treating tissues in percutaneous surgery and/or endoluminal therapy are provided. A system of the invention includes the following units and items: (a) one or more catheters for thermally treating a tissue; (b) a hydraulic subsystem for delivering cooled and or heated fluids to, and evacuating them from these catheters; (c) control station for operating the system and displaying data related to the processes to the operator; and (d) accompanying accessories, such as introduction needles, dilator sheathes, trocards, guide wires and guiding rods, some of which are grouped in various combinations into prepackaged kits.
The method according to the present invention implements contact heating and/or cooling of a tissue such that heat is transferred from, or to, a fluid flowing through the catheters. Blood circulation to and from cooled or thawing tissue is significantly lower as compared to the respective rates in the same tissue subjected to normal temperatures. Furthermore, the efficiency of the thermal treatment applied increases as the temperature of the targeted tissue is considerably lowered prior to its heating. Therefore cooling and heating a tissue are successively applied at the same location within a tissue such that a heating phase follows a cooling phase or successive heating phases are interleaved with cooling phases. Alternatively, cooling and heating are applied concomitantly at different locations. For example, cooling a peripheral region of a concomitantly heated location, or heating the periphery of a concomitantly cooled location. Cooling and/or freezing are accomplished according to the present invention by conducting heat from the tissue to a fluid cooled to a temperature considerably lower than the body temperature, which is within a range of 5° C. down to a temperature closely above the freezing point of the fluid employed. Optionally, cooling is induced by common freezing means while the treated tissue is further or concomitantly contact heated or cooled by means of catheters through which fluid having respective temperatures is delivered. Heating of the tissue is accomplished according the invention by conducting heat from heated fluids pressurized into the catheter of the invention. Alternatively, heating is accomplished by means of common heating probes while the treated tissue is contact heated or cooled by one or more catheters of the invention as is further described infra.
System for Thermally Treating a Tissue
Reference is first made to
Systems of the invention are characterized by their capability to sequentially circulate heated and/or cooled fluids through the same CTT and/or circulating a heated fluid through one CTT while a cooled fluid is concomitantly circulated through additional CTTs. For this purpose respective pumps, directional valves and temperature sensors and piping, not shown, are used between the inlet and the outlet of a pump and the respective containers. At this stage the fluids instead of being fed to the respective CTT are fed back to a respective container. When the temperature of such connected pump reaches the respective predefined value the directional valves are switched to a stage providing for feeding the respective CTT. Alternatively, fluids are stored in one container having an outlet channel that is respectively either heated or cooled to a predefined temperature. In such a case the fluids evacuated from a CTT are returned into this container and the respective directional valves may be avoided.
Control station 8 includes controller 30, a power supply unit and an operator interface unit, the latter two not shown. Controller 30 activates pump 12 and the directional valves as well as the heating and cooling devices, not shown, respectively installed in hot container 16 and cold container 18. Activating signals are transmitted from controller 30 to these devices by means of output discrete lines such as line 32 connecting between controller 30 and one of these devices. Analog and/or discrete signals received from various sensors embedded in hydraulic subsystem 8, not shown, such as temperature sensing devices, sensors for measuring the capacity of fluids fed into catheter 10 and/or evacuated from it, pressure sensors, as well as statuses of the pump and/or the directional valves and the level of fluids contained in each container are read into controller 30 by means of analog and discrete input lines such as line 34. Optionally signals generated by temperature sensors inserted within the targeted tissue, not shown, are input into controller 30 by means of analog input lines such as line 36. Link 38 to a remote computer, not shown, provides for uploading measurement and status data currently stored in the memory of controller 30 and/or for downloading working parameters and/or for remote programming of controller 30. The operator interface unit, not shown, provides for manually inputting or modifying working parameters of the system by, and for displaying process related data to, the operator and for activating the system and/or its processes.
Monitoring probe 40 provides for monitoring processes of the thermal treatment applied. Any common endoscopic means may be used for probe 40, which can be accommodated to the specific organ within the human body including the targeted tissue. Optionally, medical imaging systems such as ultrasonic, X rays or magnetic resonance imaging, are employed instead of, or in addition to, monitoring probe 40. Such endoscopic means are included in a non limiting list including means for performing tracheoscopy, bronchoscopy esophagoscopy, hysteroscopy, gastroscopy, urethroscopy, endoscopy of the vascular system, endoscopy of the small bowel, laparoscopy, thorascopy and arthroscopy.
Catheters and Accompanying Accessories
A CTT according to the invention is a slender body having an operational tip disposed at its distal end. The operational tip has a lumen and an operational face whose temperature closely equals the temperature of a fluid contained within this lumen. The external surface of a CTT except for its operational face is thermally insulated. Two fluid passages typically connect between the lumen of the operational tip and inlet and outlet apertures respectively disposed at the proximal end of the CTT. An optional tubular cavity is coaxially disposed within the CTT providing for threading of a guide wire through its lumen such that it distally and/or proximally extends from the respective open end of the cavity. Such cavity or alternatively one of the fluid passages optionally provides for introducing a guiding rod for pushing the CTT into a tissue. Catheters of the invention are characterized by their capability to withstand relatively high pressures and extreme high and low temperatures of the fluids circulated through them. The slender body can be made of elastic materials such that it is bendable providing for its introduction through curved or tortuous tracks as may be required for endoluminal therapy. A flexible CTT provided with a sharpened tip disposed at its distal end can be interstitially inserted by pushing a guiding rod inserted into its cavity. Following the placement of the CTT in the targeted location the guiding rod is removed and the CTT can be easily bended providing for relieving some of the pains involved.
Reference is now made to
The insulating sheath enclosing CTTs of the invention provides for securing tissues and layers adjacent to the treated tissue from hazards of thermal injuries. The insulating sheath is made of any thermally insulating materials that are comprised of, or coated with, biocompatible materials such as Teflon. Similarly an optional gripping handle disposed close to the proximal end of the CTTs as well as the piping and their connectors are thermally insulated providing for conveniently being held or touched by an operator or a patient. Encapsulating the external surface of a CTT with a hollow vacuumed body or with a tubular body whose surface is thermally conducting, however its temperature is controlled, is in accordance with the present invention.
CTT 67, is schematic description of a preferred embodiment of the invention, is shown in
In
In
Reference is now made to
Operating CTTs
Introducing a CTT into a tissue according to the present invention is accomplished as follows: first a guide wire threaded through thin introducing needle is placed at the targeted location, then the tract originated by the introducing needle is widened by means of a dilating sheath while the guide wire is retained in place, then the CTT in which this guide wire is threaded through its cavity is introduced by forcing its tip into the tissues along the guide wire up to the targeted location. Alternatively, introduction needles accommodated to enclose the operational tip of the CTT including those having expandable caps, can be used for forcing a CTT into a tissue. CTTs such as those described with reference to
Normally such introduction and placement of a CTT are monitored by means of common medical imaging methods such as ultrasonic, X rays or magnetic resonance imaging, and/or other common endoscopic methods accommodated to the targeted area within the human body. Therefore properly placing the operational tip can be accomplished.
Operating the STTs
The thermal treatment according to the method of the present invention subjects the targeted tissue to repetitive thermal cycles. Each cycle is preferably composed of a cooling or freezing phase and one or more heating phases successively following it. The same CTT or CTTs are successively employed for both cooling and heating phases. Namely, the treated tissue is subjected to one or more cycles including intermittently repeated cooling phases and heating phases. The operator places a CTT within the targeted tissue or changes the location in which a CTT is placed within the tissue preferably prior to a cooling or freezing phase. Optionally, a multiplicity of CTTs placed at different locations within a tissue is either simultaneously or independently operated for cooling and or heating.
For cooling and/or heating a tissue onto which an operational face of a CTT of the invention has been pressed a fluid having a predefined temperature is pressurized into this CTT. Feeding the CTT with such fluid continues until one, some, or the first, of the following events occurs: (a) a temperature measured at a predefined location or locations within the treated tissue reaches a predefined threshold; (b) the time elapsed equals a predefined time interval, and/or (c) a predefined event is detected by the operator who visually monitors the targeted tissue by means of a monitoring probe. Such a predefined event is an expansion of an “ice ball” visualized by mean of an ultrasonic imaging of a frozen tissue. The predefined time intervals are in the range of a few minutes.
The rates of heat transferred to or from the targeted tissue according to the method of the present invention are controlled by controlling: (a) the area of the operational faces of the CTTs involved, such as by expanding catheters' caps or by proximally sliding an insulating sheath of a CTT thereby exposing an extended segment of the surface enclosing the fluid contained within the CTT, (b) selecting a temperature of the fluids fed into, or circulated through, the CTTs, (c) controlling the rate of flow of the fluids through the catheters, such as by varying the pressure of the fluid, and (d) improving the contact between the operational
Optionally a CTT of the invention is used in combination with a common freezing apparatus for freezing the tissue. Exemplary freezing apparatuses normally employed are of the type utilizing liquid nitrogen or the type in which cooling is effected by an expansion of gas such as argon. In such cases the CTTs employed have an expandable cap such as of the CTT described with reference to
In order to heat tissue the temperatures of the heated fluid and the lengths of the heating time intervals are selected in accordance with the specific process to be applied (e.g. thermal forming, coagulation and/or ablation of the targeted tissue). Optionally, heating tissue is accomplished by means of a CTT of the invention in combination with a heating probe of a common heating apparatus such as a laser fiber. CTTs employed in such cases are similar to the CTT described with reference to
The temperature of tissue is monitored as is known, such as by means of thermocouples inserted into the targeted tissue at a vicinity, preferably close, to the operational face of a CTT. The heating and the cooling are further monitored by means of the monitoring probe and/or the imaging systems employed.
The controller of a STT automatically monitors the quantities of fluids entering and emerging each CTT. In cases in which these quantities differ and the difference exceeds a predefined threshold an alarm is automatically activated simultaneously with turning off the pump of the hydraulic subsystem thereby pressurizing fluid into a CTT is automatically stopped. Therefore hazards that might be caused by spilled fluids within a tissue, such as tissue dehydration or a spillage of a toxic fluid, during a thermal treatment according to the present invention are substantially minimized.
Any liquid that is biocompatible and the freezing point of which is considerably lower than 0° C. and the boiling temperature of which exceeds 45° C. can be utilized as an operative fluid according to the present invention. Suitable are aqueous solutions, due to their relatively high heat capacity. Preferable are aqueous solutions of non-toxic alcohols such as ethanol, which retain a liquid phase considerably below 0° C. down to −100° C. and lower. Similarly,
freezing point depressants such as some glycoprotein are preferable as well. Applicable are aqueous solutions of compositions normally utilized as anti freezing agents, such as dimethylsulfoxide (DMSO) or polyethylene glycol or concentrated aqueous salt solutions. Organic compositions or hydrocarbons having short carbon chains of 1-8 atoms, such mixtures and solutions whose freezing temperature is below 0° C., are less favorable due to toxicity. Pure aqueous solutions, such as saline are preferable for heating tissue. In cases in which the same fluid is employed both for heating and cooling its boiling temperature must exceed 450 and preferably 50° C.
Potential Applications
The system and method of the present invention provide for a variety of thermal treatment in subcutaneous surgery including but not limited to the following: ablating liver tumors in which CTTs are introduced through the abdominal wall, ablating prostate tumor, ablating the uterine mucosa (endometrium) in cases of excessive uterine bleeding, ablating benign prostate hyperplastic tissue close to the urethra mucosa, ablating esophageal tumors close to the esophageal mucosa, ablating dysplastic esophageal mucosa in cases of gastro-esophageal reflux, ablating endocardial tissue in cases of cardiac rhythm disorder such as atrial fibrillation, ablating endovascular atheromatous lesions, ablating the uterine cervix mucosa in cases of carcinoma in situ, remodeling the tissue close to the urethra or close to the neck of the urinary bladder in cases of urinary incontinence, remodeling tissues close to the lower esophageal sphincter in cases of gastro-esophageal reflux, etc.
An exemplary process of thermal ablation of the prostate for treating prostate cancer is described herein below with reference to
CTTs following their introduction and placement within the prostate are further connected to the piping of a STT, not shown, and phases of freezing followed heating the tissue are applied as described hereinabove. A freezing phase starts according to the method of the invention by first pressurizing cooled fluid to inflate the caps of the inserted CTTs and retaining them at the same pressure and at a temperature, which is lower than 0° C., for a period (up to a few minutes). The freezing process is monitored by means of the TRUS. Thereafter Alternatively, introducing needles capable for encompassing a CTT are employed and the use of the guide wires is avoided.
An exemplary process of ablating the benign prostate hyperplasia (BPH) according to another preferred embodiment of the present invention is described below. The patient is positioned in a lithotomy position with legs supported with stirrups as described hereinabove in example 1. A CTT such as described with reference to
Alternatively CTTs having expandable cap and a cavity for the insertion of guide wires or trocards such as shown in
Exemplary procedure for ablating the lining of the uterine cavity is hereinafter described with reference to
Laboratory experiments have been conducted for the purpose of demonstrating the method for controlling the rate in which heat is transferred to and/or from a tissue by contact heating or cooling according to the present invention. An exemplary experiment is hereby described with reference to
Initially, two CTTs were introduced into the tissue and the insulating sheaths enclosing tube 84 of each CTT were respectively pulled out of the tissue each by 2.5 cm; thereby the operational faces of the CTTs were expanded. Then fluid at −10° C. was pressurized at a pressure of 13 atmospheres (atm) into the inlet apertures of both CTTs. The time elapsed from the moment in which the pump was turned on until a freezing phase has been completed was approximately 10 minutes (min). The temperature decreased slowly in the first minute and then dropped in considerable slopes as read by both thermocouples along the following 4 min. Then the first thermocouple reached 0° C. after additional 8 min whereas the second reached 5° C. about 2 min later. Freezing occurred after about 12 min. The criteria for the end of the freezing phase were the following: (a) an almost constant reading of the first thermocouple for 20 seconds of a temperature of 0° C.; (b) the expansion of ice balls to have a diameter of about 5 mm extending outwards from the distal ends of both CTTs as was visualized by means of the USID.
By the conclusion of this cooling phase a heating phase in which the two CTTs were simultaneously employed, was applied. Both CTTs were fed by the same fluid, which has been heated to 80° C., and pressurized at 13 atm. Plot 150 shown in
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IL07/00029 | 1/9/2007 | WO | 00 | 7/8/2008 |
| Number | Date | Country | |
|---|---|---|---|
| 60757015 | Jan 2006 | US |
