Patent Application
20150032094
The invention relates to electrodes for use in medical applications. More particularly, the invention relates to tri-mode electrodes with integral temperature sensing.
In general, devices designed to desiccate tissue may use radio frequency (RF) electrical conduction through tissue to create the heat necessary to cause cellular damage. This requires that the tissue be sufficiently conductive. However, some tissue types, for example fatty tissue or mesenteric tissue, do not conduct RF energy well. To treat these poor conducting types of tissues, complex tuning of the RF generator and/or high RF voltages are required which may lead to electrical arcing and other detrimental effects. It would be advantageous to provide a device for desiccating these poor conducting tissue types without the need for complex tuning of the RF generator and/or very high RF voltages.
An embodiment of the invention provides a device for desiccating tissue. The device includes an electrode assembly having a heating element, a metal electrode, and a temperature sensor. The device also includes a radio frequency (RF) generator, coupled to the metal electrode, having a signal generator for generating an electrical signal, and switch for selecting between a first mode, second mode and third mode of operation. In the first mode, the electrical signal is directed to the metal electrode and applied to the tissue. In the second mode, the electrical signal is directed to the heating element such that heat produced by the heating element is applied to the tissue. In the third mode, the electrical signal is directed to the metal electrode and the heating element, for applying the electrical signal and the heat to the tissue.
Applicants have developed a method and apparatus for desiccating a wide variety of tissue types without requiring complex radio frequency (RF) tuning and/or power control. In one embodiment, electrodes are used which include a ceramic substrate formed over a heating element. The ceramic substrate may be coated and/or plated on the outside with a metal layer that forms an active electrode that comes into contact with the tissue. The ceramic substrate may also include an integral temperature sensor which may be embodied as a thermistor, thermal-couple junction or other temperature sensing device in order to measure the temperature of the metal electrode during the desiccation process.
In one embodiment, generator module 10 may be controlled and monitored by controller 18. Specifically, controller 18 may monitor and/or control switch module 13. Controller 18 may also monitor and/or control signal generator 11 and a temperature sensor 19 via electrical line 25. It is noted that controller 18 may be implemented as any processor known in the art, such as microprocessor, Field Programmable Gate Array (FPGA), Application Specific Integrated Circuit (ASIC).
A structural perspective view of tri-mode electrode 12 is shown in Applicants'
Tri-mode electrode 12 may also include a non-conductive substrate 22 covering a portion or completely enveloping heating element 26. This non-conductive substrate ensures that the electrical current flowing through the heating element does not pass to metal electrode 20 or into the tissue of the patient during the desiccation process.
In
Also shown in
Tri-mode electrode 12 in
It is also contemplated in
Integrated temperature sensor 19 of tri-mode electrode 12 may be embodied by a current sensing resistor, a current transformer, or any other relevant current sensor. It is also noted that, in one example, the tri-mode electrode 12 may not include an integrated temperature sensor. An external temperature sensor may be implemented. For example, an optical sensor may monitor the surface temperature of metal electrode 20 from another location (e.g., at another location on the overall electrode assembly).
As described above, metal electrode 20 comes into contact with the tissue of the patient. In one embodiment (as shown in
In the example shown in
Tri-mode electrode 12 may be electrically connected to module 10 via electrical lines 21, 24 and 25. Return electrode 33 may also be electrically connected to module 10 via return electrical line 35. If return electrode 33 is also an active electrode, then return electrode 33 may have additional electrical connections to the heating element and a temperature sensing sensor if available (not shown).
In general, during operation, power supply 30 would supply power to the various components of module 10 including signal generator 11 which generates the RF signal applied to the electrodes 12 and 33. Controller 18 would control switch module 13, signal generator 11 and user interface 31 in order to apply the proper RF treatment and/or heat treatment to tissue 34. User interface 31 may allow a user (e.g., a surgeon) to manually control the RF treatment and/or heat treatment being applied to tissue 34. More details of the overall control of switching between the various modes will be described with respect to
The two smaller tri-mode electrodes 12 may be controlled independently of one another to apply RF treatment and/or heat treatment to different portions of tissue 34. In general, controller 18 may control both of the tri-mode electrodes 12 to apply RF and/or heat to tissue 34 simultaneously, or at different times, or in a particular sequence. The return current from tri-mode electrodes 12 may be fed back to module 10 via return electrode 33 and return electrical line 35.
As already described, the user interface 31 may be utilized by the surgeon in order to manually control the application of RF energy and/or heat to tissue 34 of the patient. However, this control may also be performed automatically by controller 18. More specifically, the application of RF energy and/or the application of heat may be automatically controlled based on the measured impedance of tissue 34 during the desiccation process. Furthermore, the voltage, current, frequency, and phase of the RF signal may also be automatically and/or manually selected based on the impedance of tissue 34.
In one example, the current and voltage being applied to the tri-mode electrode may be monitored by controller 18, thereby allowing the impedance of the tissue to be computed at any point in time during the desiccation process. Controller 18 may then compare the instantaneous value of the impedance, a statistical value of the impedance or the gradient of the impedance to various thresholds in order to determine when to switch between applying RF energy (first mode), applying heat (second mode) or applying both RF energy and heat (third mode).
For example,
Once the impedance reaches threshold Z1, controller 18 may determine that the impedance is too low which may lead to high current in order to obtain the power required for desiccation. In this example, heat may be applied simultaneously (third mode) to dehydrate the tissue (i.e. increase the impedance) and reduce the time T2 to reach impedance threshold Z1. Once the impedance of the tissue is increased above threshold Z1, the RF and heat may continue to be applied simultaneously (third mode). If the voltage, which is required to reach the necessary RF energy for desiccation becomes too high (e.g. at time T3), the RF can be switched off, and only heat is applied to the tissue for the final part of the desiccation process (second mode).
Overall, controller 18 is able to control tri-mode electrodes 12 by selecting between three different modes (a first mode where only RF energy is applied, a second mode where only heat applied and a third mode where both RF energy and heat is applied to the tissue). Controller 18 may then measure and/or compute the impedance of tissue 34, analyze the impedance, and then either continue to maintain the selected mode or switch to a different mode depending on which best suits the tissue. An example of this control is shown in the flow chart of Applicants'
As shown in Applicants'
In general, once an initial mode is selected, then either the RF is applied (step 61), the heat is applied (step 63) or both the RF and heat are applied (step 62). Regardless of the mode that is selected, the controller 18 may then measure the impedance of the tissue as it is being desiccated (step 64). This measured impedance is then analyzed (step 65). Specifically, the impedance may be analyzed and compared to impedance thresholds, gradients, and other statistical values in order to allow controller 18 to make an intelligent decision on which mode is more appropriate for desiccating tissue 34 at any given point in time. Depending on this analysis, controller 18 may then select either the first mode, second mode or third mode, at which point the overall flow process would be repeated.
Although
Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.
