Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
  • A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
  • A61B18/12—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
  • A61B18/14—Probes or electrodes therefor
  • A61B18/1477—Needle-like probes

Definitions

• This invention relates generally to advances in medical systems and procedures for prolonging or improving human life. More particularly, this invention relates to an improved method and system for ablating clinical abnormalities such as tumors through the use of a high frequency electrode or a laser fiber that is passed within an endoscope in a bodily passageway and that trans-lumenally pierces the wall of the passageway.
• minimally invasive cannulae or endoscopes within the body reduces the trauma from surgery and enables access and visualization of internal structures without major surgical wounds. This is especially important in highly inaccessible areas such as in the gut, pancreas, abdomen, genitourinary tract, and so on. Access through a natural bodily opening or lumen such as the throat, rectum, urethra, or vessels saves further trauma.
• High energy or electrical current probes have been passed through an endoscope to coagulate structures on the surface of bodily lumens.
• hemorrhaging surfaces of the stomach have been treated by inserting an endoscope into the stomach through the throat.
• An electrical coagulation probe is passed through the endoscope and put in contact with the tissue that is bleeding Electrical current can be passed through the electrode to thereby coagulate the bleeding tissue and to stop the hemorrhage
• Endoscopes together with radio-frequency electrodes have been used to treat benign prostatic hyperplasia, which is an enlargement of the prostate that causes urethral obstruction
• TUNA trans-urethral needle ablation
• a radio-frequency (RF) instrument through a cystoscope (a rigid endoscopic device used for viewing in the urethra) into the urethra
• the cystoscope is first placed in the urethra for visualization of the urethral wall in the region of the prostate
• a radio-frequency electrode is passed inside the cystoscope to the position of the open end of the cystoscope near the urethral wall
• a tip of the radio-frequency electrode is pushed out along an off-axis path to pierce the urethral wall so that it passes into the prostatic tissue outside of the urethra
• Radio-frequency energy from an external generator system is then applied to the radio-frequency electrode tip in the prostatic tissue to ablate the tissue outside the urethral wall
• the TUNA cystoscope is a rigid tube It carries a straight fiber optic visualization channel so that the surgeon can view the scene directly ahead and slightly to the side of the opening at the distal end of the cystoscope It is through that opening that the radio-frequency electrode passes and then pierces the urethral wall to enter the prostatic tissue
• the radio-frequency electrode passes and then pierces the urethral wall to enter the prostatic tissue
• there is some degree of visualization intra-lumenally that is, before the electrode pierces the urethral wall, there is no trans-lumenal visualization of the electrode tip in its placement after the piercing of the urethral wall
• the TUNA procedure is a relatively blind procedure in the sense that the end of the
• a straight, rigid endoscope such as the urethral cystoscope
• a straight endoscope is inadequate 3
• the techniques described above are limited in that they are not well-adapted to performing RF ablation in deep-lying tumors.
• Among the limitations of these techniques are the restrictions of using a straight endoscope and the lack of extra-lumenal imaging to control positioning of a radio-frequency electrode. Accordingly, an effective technique for performing minimally invasive, trans-lumenal radio-frequency ablation with image guidance through a natural bodily lumen is desirable for the purposes of treating cancerous tumors and other clinical diseases associated with bodily organs.
• the present invention is directed to a system and procedure for trans-lumenal radio- frequency (RF) heat ablation of bodily tissue through and by the use of an RF electrode or a laser fiber that is passed through an endoscope.
• RF radio- frequency
• the system and procedure of the present invention are different than any of the systems and procedures discussed in the Background section above.
• the advantages of the present system and method reside, in part, in their superior ability to access non-superficial tumors and to provide image guidance.
• Image guidance mechanisms may be provided within the intra-lumenal endoscope itself or from an external image guidance apparatus to visualize the position of the RF electrode or laser fiber tip in the target tissue.
• a tumor of the pancreas can be effectively treated using the present minimally invasive system and technique.
• the technique of the present invention involves inserting a flexible endoscope through the throat to reach the region of the stomach wall.
• One 4 portion of the stomach wall is in close proximity to the pancreas, which in this example contains a cancerous tumor identified by previous CT or MRI scanning
• a long radio-frequency electrode is passed through the flexible endoscope.
• the electrode has a pointed tip which emerges through an opening in the distal end of the endoscope thereby enabling piercing of the stomach wall to penetrate the pancreas.
• An ultrasonic imaging head is built into the distal end of the flexible endoscope to visualize the pancreatic tissue near the distal end.
• the position of the tip of the radio-frequency electrode can then be adjusted under direct ultrasonic visual guidance, so that it can be placed into the pancreatic tumor.
• the RF electrode is then connected to an RF generator external to the body, thereby producing a heat ablation of the pancreatic tumor.
• other visualization methods such as MRI, CT, or external X-ray or external ultrasound could be used to assist visualization of the electrode tip as its emerges from the endoscope.
• the RF electrode of the present invention has the advantage that it can be used to pierce the natural lumen wall; that is, it is used trans-lumenally It thus enables treatment and ablation of tumors which lie deep within tissue in the region of a portion of a natural lumenal passage in the body.
• the present invention procedure has the further advantage of being able to control the positioning of the RF electrode through intra-lumenal image guidance via ultrasound, or through external image guidance using ultrasound or other image modalities This reduces the risks associated with blind procedures such as the TUNA procedure cited above
• the present technique, system, and method has the advantage that it enables use of flexible endoscopes, not just the straight cystoscope employed in the TUNA procedure. This makes possible access to a much wider range of target sites and cancerous tumors. For example, tumors in the liver, kidney, spleen, and pancreas may be accessed through a flexible endotrachial endoscope. Such access may further be enhanced by endoscopic ultrasonography built into the endoscope itself.
• a bronchoscope enables access to the lung to perform RF ablation of tumors of the lung and mediastinum.
• a choledochoscope can be used to access the bile ducts for ablating tumors in the vicinity of the hepatic portal and biliary tree.
• Angioscopes can be used with RF electrodes according to the present system and invention to access organs through the vessels or arteries of the patient's body. Cranial endoscopes or flexible cranial endoscopes may access portions of the brain or endocranial cavity for this purpose.
• Ureteroscopes can be used for treating the upper genitourinary tract.
• FIGURE 1 is a schematic diagram showing a portion of a patient along with a system according to the invention for performing trans-lumenal radio-frequency (RF) ablation of the pancreas using a flexible endoscope passed into the stomach through the throat;
• RF radio-frequency
• FIGURE 2 illustrates a portion of an intra-lumenal ultrasonic imaging endoscope head with an optical viewing channel and a trans-lumenal radio-frequency electrode piercing a bodily lumen wall to penetrate a target volume outside the lumen;
• FIGURE 3 is a flowchart of the process employed in operating a system in accordance with the present invention.
• a flexible endoscope E is inserted into the stomach S of a patient through the patient's mouth M and throat T.
• the endoscope E has a flexible, elongated body 4 that can be manipulated to direct a distal end 7 of the endoscope E into the stomach S.
• the operating field of the endoscope may include organs within, near, or around the stomach S in this illustration.
• an ultrasonic scanner 10 having a scanning head 11 capable of scanning a field of view F demarcated by dashed lines 14 and 15.
• This field of view F may include an organ such 6 as the patient's pancreas P, which lies near the stomach.
• the ultrasonic scanner 10 is capable of scanning a portion of the wall of the stomach S and the nearby pancreas P.
• an RF electrode 106 having a stainless steel shaft 111 approximately one to several millimeters in diameter is partially covered with an insulating coating (illustrated by hatched lines 114 in Figure 2).
• the coating is one of many standard plastic insulative materials.
• the shaft 111 has a tip 121 that in various embodiments may be a sharpened cone, trocar, bevel, or other tissue-piercing structure.
• 18-gauge stainless steel tubing is used for the elongated shaft 111 of the electrode 106 in Figure 2.
• An exposed tip portion 117 of the electrode shaft 111 has a length between one millimeter and several millimeters or several centimeters, depending on clinical needs.
• the entire length of the RF electrode 106 may be several centimeters to as long as 200 or 300 centimeters or more, depending on which orifice and lumen the endoscope is designed for in the patient's body.
• Other materials may be used for the RF electrode shaft 111 and exposed tip 117, including
• the electrode shaft 111 is fabricated in a spiral configuration for greater flexibility, such as in a Seldinger wire.
• the shaft 111 comprises a wire construction coated by a catheter-like sheath, or alternatively, a catheter with a ring or helical coil external surface as part of its tip end. Examples of various electrode configurations can be seen in the article by E. R.
• the endoscope E itself may take any of various possible forms.
• the endoscope E is a flexible device used for upper gastrointestinal (GI) endoscopy.
• GI gastrointestinal
• Such devices are typically up to 1 meter long, and have a snake-like, flexible or steerable body 4 7
• the endoscope E is a gastroenterological endoscope for lower endoscopy in the rectum or bowel
• the endoscope is a cystoscope for urological applications, these are typically much shorter in length
• the endoscope may be a bronchoscope or a choledochoscope for applications in the lung, mediastinum, and upper thorax, or an endoscope which is capable of being inserted into a vessel in the vascular system, such as a vein or artery, or an endoscope which is capable of being inserted into the bile ducts, renal collecting system, and upper urinary tract
• the RF electrode 106 is inserted into a tumor 108 (the outline of which is indicated in a sectional view in Figure 2) Once the exposed tip 117 has been positioned in the tumor 108, as identified via the
• the high-frequency generator 37 is set to a frequency in the range of 500 kHz (see, e.g , some of the generators sold by Radionics, Inc , Burlington, Massachusetts)
• the RF electrode 106 has at least one temperature sensor 118
• a cooling system is employed to circulate coolant through the electrode to produce even larger-sized lesions without overheating the tissue near the exposed tip 117.
• lesions of up to several centimeters in diameter can be accomplished by using an approximately 18-gauge radio-frequency electrode tip 117 having a length of approximately 1 to 2 cm, raised to a temperature of around 90 °C and kept at that temperature for 30 seconds to several minutes.
• the electrode 106 can range in diameter from 0.1 to several millimeters, and its length can range from 3" to 30" (approximately 8 to 80 cm) or more, depending on the kind and size of endoscope used and the clinical application.
• the temperature, amount of power, and other system parameters are related to the size of the lesion desired. Desired heat lesion sizes may vary from several millimeters to several centimeters, depending on clinical considerations. RF generators with RF power output ranging from several hundred watts may be needed, depending on the power requirements to ablate a particular tumor volume.
• Monitoring of lesion parameters during the heating process is typical, and in one embodiment of the invention, includes monitoring tip temperature and RF power, current, volume, impedance, and time.
• an external imaging apparatus shown as an imager 90
• an imager 90 may be employed to guide or control the position of the RF electrode.
• a CT, MRI, X-ray, or ultrasonic scanner may be used to monitor the position of the distal end 7 of the endoscope E and the exposed RF electrode tip 117 in its placement within the target region.
• An MRI imager is capable of visualizing temperature isotherms, and ultrasound can identify cavitating boiling during such procedures.
• the flexible endoscope body 4 has a distal end 7 which includes within it an ultrasonic imaging head 11.
• the imaging head 11 has an ultrasonic transmission and detection element 104 pointing toward one surface of the distal end 7
• the detection element 104 is capable of imaging ultrasonic signals in an angular slice between the dashed lines 14 and 15 (as in Figure 1)
• This field of view of the ultrasonic scanner 10 preferably includes the tumor 108
• the field of view also typically includes a portion of the lumenal wall 100, as well as the tissue near it between the dashed lines 14 and 15
• a graphics display 67 presents representations of the ultrasonic scanning image
• the graphics display 67 is a CRT display, on which a rendering 70 of a radio-frequency tip 20 within the tissue is shown together with a rendering 71 of the tumor 108 ( Figure 2)
• a hub
• the distal end 7 may include a portion of the components of an MRI scanner to produce MRI images of tissue near the distal end
• This portion of components could comprise, for example, a sensing coil as the detection element 104 operating in cooperation with an external imaging apparatus 90 to produce MRI images through the controller 60 and the display 67
• an optical viewing element 130 which in a preferred embodiment is a fiber optic illumination and viewing channel At its distal end is a viewing port 133, typically a lens
• the optical viewing element 130 provides visual information on the passage of the exposed electrode tip 117 through the wall of the stomach S during its passage to the tumor 108
• the hub 24 of the endoscope E ( Figure 1) also has a port 74 through which the fiber optic channel 77, which transmits a visual image from the viewing element 130 to the outside world, is passed
• a fiber optic light source and image processor 80 enables visual representations to be displayed on fiber optic display 84
• the fiber optic display 84 is a CRT display capable of showing a rendering 85 of the electrode 20
• the display 84 may show a representation of the actual electrode 106 as it passes out through a port 124 at the distal end 7 of the endoscopic head, as shown in Figure 2
• the embodiment of Figure 1 includes a high-frequency generator 37 10
• the generator 37 is a radio-frequency generator providing an electrical output
• the generator 37 is a power source for the generation of laser signals and an accompanying power output.
• a set of controls 40 for the high-frequency generator 37 may comprise knobs, levers, or other control facilities enabled to control, for example, the power output from the generator 37
• the controls 40 allow the power output to be raised or lowered, started or stopped, or automatically or manually regulated
• a readout 47 is also provided; in various embodiments it may comprise signal readouts or representations of the output parameters and other parameters associated with the generator 37
• the associated parameters displayed on the readout 47 would preferably include indications of power, current, voltage, time, impedance, or other parameters associated with the radio-frequency output to the electrode 20
• the readout 47 would preferably include indications of laser energy, frequency, and so on.
• a satellite temperature monitor 150 with an associated readout and control system 154.
• this apparatus includes a secondary temperature probe which can be inserted into, for example, the pancreas P, to monitor the temperature of tissue in the vicinity of the heat ablation region
• a radio-frequency current is applied to the exposed electrode tip 117
• an ablative temperature zone may be indicated by a dashed line 110.
• the ablative temperature zone 110 is the isotherm corresponding to approximately 45 °C.
• the temperature monitor 150 which in one embodiment is a thermocouple temperature probe, is placed in the pancreas P (as an example) at a point adjacent to very critical structures such as nerves, vessels, or adjacent organs
• the temperature sensor can be used to thereby ensure that the temperature of that region does not exceed a dangerous temperature during the course of heat 11 ablation of the target.
• the control and readout element 154 may be associated with the control and readout elements 40 and 47 ( Figure 1), and in a preferred embodiment is integrated with them.
• the procedure starts by inserting the desired endoscope into the appropriate body lumen (step 200).
• the endoscope may be either flexible or rigid, and is of a correct size and length to accommodate the clinical need.
• the endoscope may be inserted into the appropriate body lumen such as the throat, bronchi, bile ducts, rectum, lung cavity, upper urinary or lower urinary system, vagina, heart, or arterial or venous vessels, etc.
• This positioning step 200 of the endoscope may include the use of external or internal imaging.
• the endoscope may incorporate an internal ultrasonic head, as illustrated in Figures 1 and 2, and this can be used to achieve a desired position relative to the wall of the lumen in which it is inserted.
• a high frequency electrode is passed through the endoscope channel (step 204).
• the electrode has a tissue-piercing point; it punctures the lumenal wall for its trans-lumenal course into a target volume. This process is visualized (step 207) by way of an internal ultrasonic head within the endoscope, as illustrated above.
• External visualization using ultrasound, X-ray, MR, or CT may also be employed in addition to, or as an alternative to, intra-lumenal ultrasonic applications. These internal and/or external imaging methods may be continued during and after making the heat lesion to help in determining the adequacy of the ablation size and when to stop the heating process.
• the positioning of the RF electrode tip to the desired target volume is performed based on the intra-lumenal imaging apparatus or the external imaging apparatus.
• the position of the exposed electrode tip 117 can be adjusted based on the intra-lumenal scanning image on the display 67 ( Figure 1) to achieve the appropriate positioning of the electrode tip within a tumor.
• the exposed RF electrode tip 117 When the exposed RF electrode tip 117 ( Figure 2) is in its proper position within the tumor, it is connected to the external generator 37, and high frequency power is delivered through 12 the electrode tip 117 to the tissue to ablate the tumor (step 214).
• This step can involve elevating the voltage, current, or power applied by the high frequency generator 37 to the electrode and therefore to the tumor tissue.
• the generator 37 may have manual controls such as knobs or levers, or other elements to control its output levels that can be actuated at this point.
• the process may be automated with an initial power setting or temperature level predetermined by the operator. The generator can then, under automatic or semi-automatic control, achieve the pre-selected parameter (such as temperature) and lock onto it by a feedback or control system within the generator 37.
• the step of adjusting and setting the output values may include setting the RF power, voltage, or current levels, among other parameters.
• this step includes achieving a desired temperature as recorded at the RF electrode tip 117 or at the satellite temperature monitor 150 placed elsewhere within the target volume or neighboring the operative field as illustrated in Figure 2.
• the time of RF power application may also be monitored.
• a pre-determined exposure time for high-frequency power to the electrode may also be desirable, depending on clinical needs, or may depend on the reading of temperature sensors in the RF ablation electrode at various positions.
• multiple temperature sensors e.g., 118 are placed along the RF electrode tip 117 to monitor the temperature at various positions within the target volume, and these temperatures can be read out on a temperature monitoring system 44 ( Figure 1).
• a desired ablation volume can be achieved with a certain electrode geometry by applying a known value of RF power, current, or voltage, or alternatively by achieving a known temperature as recorded in one or more temperature monitors within the RF electrode or in surrounding tissue.
• RF power current, or voltage
• a known temperature as recorded in one or more temperature monitors within the RF electrode or in surrounding tissue.
• These parameters may be monitored during the ablation process to influence the decision of the clinician to terminate or continue the process according to experience and parameter values.
• measurement of such parameters is illustrated by the RFG-3C lesion generator systems of Radionics, Inc. (Burlington, Massachusetts).
• the duration and parameter settings used to achieve the desired RF 13 heat ablation volume or effect may, depending on the position and type of target to be ablated, determine the time at which the heating process is stopped (step 221). The decision to stop the procedure when it is believed that the tumor volume or other target structure of interest is adequately ablated is made at this time.
• the use of internal and/or external imaging or diagnostic detection methods may be involved in this step.
• the use of ultrasonic scanning or MRI imaging may enable visualization of the heat ablation volume as it is being made or after it has been made.
• An ultrasound scan can identify gas bubble formation in the heated region and MRI can visualize thermal distributions, both of which may be an indication of actual lesion volume.
• the clinician may choose an
• the RF electrode tip geometry of a certain size, diameter, and length. He may know from experience that the insertion of an electrode trans-lumenally in a particular clinical site and delivering RF power to raise the tissue temperature near the electrode tip to a certain level will produce a known and adequate ablation volume. These criteria may be used by the clinician to induce sufficient ablation sizes.
• the RF electrode may not have a temperature sensor.
• the correlation of ablation size desired for a given electrode tip geometry may be determined by considering RF parameters such as power, output, voltage, and current. Generally, it may be known that RF power or current levels greater than certain values for a known electrode geometry will produce a desired size of ablation volume. In that case, the clinician may select the criteria of power and time to determine a desired ablation effect. Variations of the use of such parameters are embodied in the process set forth in Figure 3.
• CT, MR, X-ray, or ultrasound images are used to monitor the ablation size, then they may be used to decide an adequate ablation size.
• certain MR images can represent thermal distribution around the electrode and thus indicate the ablation zone. This may be used as exemplary criteria in determining when to terminate the ablation process, as in step 221.
• extra-lumenal RF electrodes in combination with endoscopes and endoscopic ultrasonography has the advantages of making accessible target volumes such as tumors in organs that are near body lumens and cavities.
• the present system and method thereby enable image- 14 guided control of radio-frequency ablation with minimal invasion. Tumors of the pancreas, liver, intestines, lungs, spleen, kidney, and upper and lower digestive system may be reached in this way, and accurate placement of ablation volumes can be made without the need for major surgery.
• image-guided control such as endoscopic ultrasonography as described above, monitoring of the process and electrode placement becomes more accurate.
• a further advantage of the present invention is that it enables precise control of the placement of electrodes in organs which otherwise may not be amenable to open surgery. For example, with ultrasound combined in the endoscope, visualization of the heat ablation of the tumor can be gauged in a visual and quantitative way. Because most bodily tissues remain intact, the visualization of the tumor by imaging remains largely undisturbed by the minimal invasion of the RF electrode. This is in contrast to open surgery, in which large position shifts can take place during surgical incision and retraction.
• a further advantage of the present system and method over previous use of coagulation through endoscopes is that it is not limited to coagulation or burning of the lining of the lumenal structure.
• the present invention greatly expands the scope of, for example, radio-frequency ablative coagulation to much deeper structures within the organs near to the lumenal structure.
• Yet a further advantage of the present system and method is that it minimizes risk to the membranes or the mucosal structures of the lumen through which the RF electrode is passed.
• the RF electrode or other delivery means is sufficiently small-gauged so that it will not cause hemorrhage or permanent damage to the lumenal surface.
• the placement of the exposed RF electrode tip for example, can be deep enough and away from the lumenal lining to prevent destruction of the lumenal lining from the RF heat itself.
• the minimally invasive nature of the present invention is better tolerated by patients who may be otherwise too weak to withstand surgery, a wider population of patients will be suitable for this method.
• the minimally invasive character of the treatment will also reduce 15 side effects such as bleeding, the need for heavy anesthetics, prolonged hospitalization and recuperation, and convalescent care. All of these advantages have the potential to reduce hospital and medical reimbursement expenses.
• an electrode may be pre-shaped in a curved configuration to permit aiming the electrode in a desired direction once it has projected beyond the opening of the endoscope.
• Different geometries of electrode may be suitable for different clinical needs or target sites, and these can be developed by those skilled in the art without departing from the scope of the invention.
• Electrode structures having multiple electrode tips to fan out into the tumor volume may also be used.
• bipolar electrodes can be used, in which one or more separate electrical conductive surface areas are present on or along the elongated electrode shaft.
• the different electrode areas can be raised to different high frequency voltages at the same or different times to alter or grade the shape of the heat ablation region.
• the high frequency electrode can be cooled internally or by ejection of a fluid out of the tip region.
• cooled saline injected into the proximal hub 24 ( Figure 1) runs through a channel inside the endoscope E and flows out of the distal end 7 near the electrical contact so as to cool the tissue near the tip 117
• the RF generator 37 may employ various frequency ranges. For example, low radio-frequency signals in the range of 10 to 50 kHz, intermediate radio-frequency signals between 50 and 1,000 kHz (1 MHz), or high radio-frequency into the microwave range of tens or hundreds of megahertz may be used, all without departing from the scope of the invention.
• other elements analogous to the electrode 20 in Figure 1 may be used within the flexible endoscope, using endoscopic ultrasonography to produce extra-lumenal ablation.
• the radio-frequency electrode could be replaced by a laser fiber.
• This may transmit optical energy from a laser generator (replacing the high-frequency 16 generator 37 of Figure 1) through a carrier 30, which may include fiber optic bundles to deposit energy in the region of the tumor 108 ( Figure 2).
• a carrier 30 may include fiber optic bundles to deposit energy in the region of the tumor 108 ( Figure 2).
• the ablator or ablative element used with the flexible endoscope and in combination with image-guided ultrasonography and other imaging means may be considered generally as one of several known ablation systems.
• the device may include, therefore, electrical current and power, or optical current and power, or microwave antennas to produce the heat ablation of the target volume.

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