Improved heat transfer during ablation

Abstract

The present invention is titled "Improved Heat Transfer During Ablation Procedures". Embodiments described herein include an apparatus that includes an in vivo probe and an electrode coupled to a distal end of the in vivo probe. The electrode includes a flexible electrically insulating substrate that includes a substrate surface. The electrode further includes a conductive metal layer that covers at least a portion of the substrate surface. The electrode further includes a metal sheet that includes an inner sheet surface and an outer sheet surface, the outer sheet surface being shaped to define a plurality of recesses. The electrode further includes an adhesive that fills the recesses and bonds the outer sheet surface to the conductive metal layer. Other embodiments are also described.

Description

Technical Field

[0001] The present invention relates to an in vivo probe and its use during ablation procedures. Background Art

[0002] In some ablation procedures, an electrode disposed at the distal end of an in vivo probe is brought into contact with tissue, and then radiofrequency (RF) energy is transferred from the electrode into the tissue. The RF energy raises the temperature of the tissue, thereby creating an ablation lesion in the tissue.

[0003] U.S. Patent Application Publication 2018 / 0110562, the disclosure of which is incorporated herein by reference, describes a catheter that includes an insertion tube, a flexible substrate, and one or more electrical devices. The insertion tube is configured to be inserted into a patient's body. The flexible substrate is configured to wrap around the distal end of the insertion tube and includes electrical interconnects. The electrical devices are coupled to the flexible substrate and connected to the electrical interconnects. Summary of the Invention

[0004] According to some embodiments of the present invention, there is provided a device that includes an in vivo probe and an electrode coupled to the distal end of the in vivo probe. The electrode includes a flexible electrically insulating substrate that includes a substrate surface. The electrode further includes a conductive metal layer that covers at least a portion of the substrate surface. The electrode further includes a metal sheet that includes an inner sheet surface and an outer sheet surface, and the outer sheet surface is shaped to define a plurality of recesses. The electrode further includes an adhesive that fills the recesses and bonds the outer sheet surface to the conductive metal layer.

[0005] In some embodiments, the substrate and the sheet are shaped to define a lumen that is at least partially encapsulated by the inner sheet surface.

[0006] In some embodiments, the substrate and the sheet are shaped to define a cannula.

[0007] In some embodiments, the distal end of the probe includes a diverter configured to divert fluid received from the proximal end of the probe, and the inner sheet surface is coupled to the diverter such that the diverter is disposed inside the lumen.

[0008] In some embodiments, the substrate and the sheet are shaped to define a ring.

[0009] In some embodiments, the substrate and the sheet are shaped to define an arc.

[0010] In some embodiments, the sheet includes cobalt chromium.

[0011] In some embodiments, the conductive metal includes gold.

[0012] In some embodiments, each of the recesses has a circular perimeter.

[0013] In some embodiments of the present invention, there is also provided a method that includes forming a plurality of recesses in an outer surface of a metal sheet, and after forming the recesses in the outer surface, applying an adhesive between the outer surface and a conductive metal layer covering at least a portion of a substrate surface of a flexible electrical insulating substrate such that the adhesive fills the recesses and bonds the outer surface to the conductive metal layer. The method further includes, after applying the adhesive, coupling the metal sheet to a distal end of an in vivo probe.

[0014] In some embodiments, forming the recesses includes forming the recesses by:

[0015] coupling a mask shaped to define a plurality of openings to the outer surface of the metal sheet, and

[0016] placing the metal sheet in a chemical etching bath such that portions of the outer surface exposed by the openings are etched away.

[0017] In some embodiments, each of the openings is circular.

[0018] In some embodiments of the present invention, there is also provided an apparatus that includes an in vivo probe and an electrode coupled to a distal end of the in vivo probe. The electrode includes a flexible electrical insulating substrate that includes a substrate surface. The electrode further includes a conductive metal layer that covers at least a portion of the substrate surface. The electrode further includes a metal sheet that includes an outer sheet surface and an inner sheet surface, the outer sheet surface being bonded to the conductive metal layer and the inner sheet surface being shaped to define a plurality of protrusions.

[0019] In some embodiments, the substrate and the sheet are shaped to define an inner cavity that is at least partially enclosed by the inner sheet surface.

[0020] In some embodiments, the substrate and the sheet are shaped to define a cannula.

[0021] In some embodiments, the distal end of the probe includes a diverter configured to divert fluid received from a proximal end of the probe, and the inner sheet surface is coupled to the diverter such that the diverter is disposed inside the inner cavity.

[0022] In some embodiments, the substrate and the sheet are shaped to define a ring.

[0023] In some embodiments, the substrate and the sheet are shaped to define an arc.

[0024] In some embodiments, the sheet includes cobalt chromium.

[0025] In some embodiments, the conductive metal includes gold.

[0026] In some embodiments, the perimeter of each of the protrusions is rectangular.

[0027] In some embodiments, the perimeter of each of the protrusions is star-shaped.

[0028] According to some embodiments of the present invention, there is also provided a method that includes forming a plurality of protrusions on an inner surface of a metal sheet, and after forming the protrusions on the inner surface, bonding an outer surface of the metal sheet to a conductive metal layer that covers at least a portion of a substrate surface of a flexible electrical insulating substrate. The method further includes coupling the metal sheet to a distal end of an in vivo probe after bonding the outer surface of the metal sheet to the conductive metal layer.

[0029] In some embodiments, forming the protrusions includes forming the protrusions by:

[0030] coupling a plurality of masks to the inner surface, and

[0031] placing the metal sheet into a chemical etching bath such that one or more portions of the inner surface disposed between the masks are etched away.

[0032] In some embodiments, each of the masks is rectangular.

[0033] In some embodiments, each of the masks is star-shaped.

[0034] According to some embodiments of the present invention, there is also provided a method that includes inserting an electrode into a subject's body, the electrode including: (i) a flexible electrical insulating substrate that includes a substrate surface; (iii) a conductive metal layer that covers at least a portion of the substrate surface; and (iii) a metal sheet that includes an outer sheet surface and an inner sheet surface, the outer sheet surface being bonded to the conductive metal layer and the inner sheet surface being shaped to define a plurality of protrusions. The method further includes passing an electric current between the electrode and another electrode after inserting the electrode into the subject's body such that heat is generated in the subject's tissue by the electric current and the heat is transferred to the protrusions. The method further includes flowing a fluid over a surface of the protrusions such that heat is transferred from the protrusions to the fluid.

[0035] In some embodiments, the fluid includes saline.

[0036] In some embodiments, the fluid includes the subject's blood.

[0037] In some embodiments, flowing the fluid over the surface of the protrusions includes flowing the fluid turbulently over the surface of the protrusions.

[0038] The present disclosure will be more fully understood in conjunction with the following detailed description of embodiments of the invention with reference to the accompanying drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of a system for ablating tissue of a subject according to some embodiments of the present invention;

[0040] Figure 2A Schematic diagram of an ablation electrode according to some embodiments of the present invention;

[0041] Figure 2B Schematic diagram of a hole passing through the surface of an ablation electrode according to some embodiments of the present invention;

[0042] Figure 3 Schematically shows a longitudinal cross - section of the ablation electrode shown in Figure 2A ;

[0043] Figure 4 and Figure 4 (Continued) Flowchart of a method for manufacturing an ablation electrode according to some embodiments of the present invention;

[0044] Figure 5 Schematic diagram of an ablation electrode before deformation according to some embodiments of the present invention;

[0045] Figure 6A Schematic diagram of a method for forming a recess in the surface of a support sheet according to some embodiments of the present invention;

[0046] Figure 6B Schematic diagram of a method for forming a protrusion in the surface of a support sheet according to some embodiments of the present invention; and

[0047] Figure 7 Schematically shows the transfer of heat into the ablation electrode according to some embodiments of the present invention. Detailed Description

[0048] Overview

[0049] As described in U.S. Patent Application 15 / 990,532, which is incorporated herein by reference, embodiments of the present invention include an ablation electrode that includes at least one flexible printed circuit board (PCB) bonded to a support metal sheet by an adhesive. (The support sheet may also be referred to as a "support structure.") The flexible PCB includes a flexible electrical insulating substrate that includes an outer surface and an inner surface, where the outer surface is coated with an outer layer of a conductive (and biocompatible) metal such as gold, palladium, or platinum, and the inner surface is coated with an inner layer of the same (and / or another) conductive metal. The inner surface may further support one or more electronic components electrically isolated from the inner metal layer, such as sensors (e.g., thermocouples) and traces. After depositing the electronic components, coating the substrate, and bonding the PCB to the support sheet, the flexible PCB (along with the support sheet) can be deformed into any suitable shape. For example, in some embodiments, the flexible PCB is deformed into a cannula-shaped electrode, which will be referred to hereinafter as a "tip electrode." The electrode is then coupled to the distal end of an in vivo probe.

[0050] During the ablation process, the outer metal layer is brought into contact with the tissue to be ablated, and then ablation current is passed through the outer metal layer into the tissue. When the ablation current is applied to the tissue, the sensor can obtain any relevant physiological readings from the tissue. Typically, a plated-through opening via in the electrode provides an electrical connection between the inner metal layer and the outer metal layer such that the ablation current can pass outward through the plated-through via, and an electrogram signal from the tissue can pass inward through the plated-through via. The electrical connection may also be provided by blind vias, each such via being formed by removing a portion of the substrate such that the outer metal layer directly contacts the underlying trace.

[0051] The aforementioned plated-through vias also provide fluid communication between the inner and outer surfaces of the electrode such that a flushing fluid (e.g., saline) can pass through the plated-through vias into the surrounding blood. The flushing fluid dissipates heat from inside the electrode into the blood and, additionally, dilutes the blood at the tissue-electrode interface, thereby reducing the likelihood of coagulation or carbonization. Given the fact that the plated-through vias provide a passage for the flushing fluid, the plated-through vias may also be referred to as "flushing channels" or "flushing holes."

[0052] Typically, a large number of small closed holes (hereinafter referred to as "heat dissipation holes") pass through the substrate. The heat dissipation holes increase the thermal connection between the inner and outer coatings of the substrate such that more heat can be transferred from the tissue-electrode interface to the interior of the electrode. However, despite the presence of the heat dissipation holes, the heat dissipated by the flushing fluid may be limited due to the lack of sufficient surface area for heat exchange between the support sheet and the flushing fluid. Additionally, the adhesive that bonds the PCB to the support sheet may provide significant heat resistance, thereby limiting the heat transferred to the support sheet.

[0053] To address this challenge, the embodiments described herein form the inner surface of the support sheet that contacts the flushing fluid to define a plurality of protrusions. Typically, the protrusions are formed by placing a mask pattern on the inner surface of the support sheet and then etching away portions of the inner surface between the masks. The protrusions provide an increased surface area for contact with the flushing fluid and also cause turbulence in the flow of the flushing fluid, thereby increasing the amount of time the flushing fluid contacts the inner surface. Thus, with the aid of the protrusions, more heat can be dissipated from the support sheet.

[0054] Alternatively or additionally, a plurality of recesses may be formed in the outer surface of the support sheet, the outer surface being bonded to the PCB. For example, a pattern of circular recesses may be formed by placing a mask shaped to define a pattern of circular holes on the outer surface and then etching away portions of the outer surface exposed by the holes. When the support sheet is bonded to the PCB, these recesses collect the adhesive, thereby improving the adhesion between the support sheet and the PCB while also reducing the amount of adhesive placed between the PCB outside the support sheet and the recesses. Thus, more heat can be transferred to the support sheet.

[0055] System Description

[0056] First refer to Figure 1 , which is a schematic diagram of a system 20 for ablating tissue of a subject 26 according to some embodiments of the present invention.

[0057] Figure 1 It is shown that a physician 28 performs an ablation procedure on a subject 26 using an in-vivo probe 22. During this procedure, the physician 28 first inserts an ablation electrode 40 disposed at the distal end of the probe 22 into the subject and then navigates the electrode 40 to the tissue to be ablated. For example, the physician may advance the electrode through the vasculature of the subject until the electrode contacts cardiac tissue belonging to the heart 24 of the subject. Next, when the electrode 40 contacts the tissue, the physician causes a radio frequency (RF) current to be transmitted between the ablation electrode and another electrode such that heat is generated in the tissue. For example, during a monopolar ablation procedure, the current may be transmitted between the ablation electrode and a neutral electrode patch 30 coupled to the outside of the subject (e.g., the back of the subject).

[0058] To facilitate navigation of the probe 22, the probe may include one or more electromagnetic position sensors that generate signals that vary with the position of the sensors in the presence of an external magnetic field. Alternatively or additionally, any other suitable tracking system may be used, such as, for example, an impedance-based tracking system. For example, both electromagnetic tracking and impedance-based tracking may be used, as described, for example, in U.S. Patent 8,456,182, the disclosure of which is incorporated herein by reference.

[0059] The probe 22 is connected proximally to a console 34, which includes, for example, a processor (PROC) 23, a pump 25, and a signal generator (GEN) 27. (The electrode patch 30 is typically also connected to the console 34 via a wire 42). During an ablation procedure, the signal generator 27 generates the ablation current described above. These currents are transmitted through the probe 22 to the electrodes 40 via one or more wires. Additionally, the pump 25 supplies a flushing fluid such as saline to the distal end of the probe, as further described below with reference to Figures 2A to 2B and Figure 3 further described.

[0060] The console 34 also includes a controller 35 that a physician can use to control the parameters of the ablation current. Specifically, in response to manipulation of the controller 35 by the physician 28, the processor 23 can adjust the parameters of the ablation current by outputting appropriate instructions to the signal generator 27 over any suitable wired or wireless communication interface. The processor 23 can similarly control the pump 25 via any suitable wired or wireless interface. Additionally, the processor can receive and process any relevant signals from the distal end of the catheter, such as signals received from any of the sensors described herein.

[0061] In some embodiments, the system 20 also includes a display 38 that can display relevant outputs to the physician 28 during the procedure.

[0062] Although Figure 1 a particular type of procedure is shown, it should be noted that the embodiments described herein can be applied to any suitable type of ablation procedure (such as otolaryngology or neurology ablation procedures), or any other process that requires heat transfer through a flexible PCB (such as heat dissipation from a circuit sheet into a surrounding fluid).

[0063] Ablation Electrode

[0064] Now referring to Figure 2A , which is a schematic diagram of an ablation electrode 40 according to some embodiments of the present invention. Also refer to Figure 3 , which schematically shows a longitudinal cross-section through the electrode 40 according to some embodiments of the present invention.

[0065] As described above with reference to Figure 1 the probe 22 includes at least one ablation electrode 40, such as shown in Figure 2A and Figure 3The tip electrode in []. The electrode 40 includes a plated flexible electrical insulating substrate 41, which is bonded to the support sheet 36 at the distal end of the probe 22 by an adhesive. The substrate 41 can be made of any suitable flexible electrical insulating material (such as a flexible polymer (e.g., polyimide) or a liquid crystal polymer (LCP)). The support sheet 36 can be made of any suitable rigid material (such as cobalt-chromium, stainless steel, or magnesium). For example, the support sheet can include a cobalt-chromium alloy, such as the L-605 cobalt-chromium-tungsten-nickel alloy.

[0066] Generally speaking, the electrode 40 can have any suitable shape. In some embodiments, as Figure 2A and Figure 3 shown, the electrode 40 is sleeve-shaped, which includes a cylindrical portion 40b capped by a dome-shaped portion 40a. Usually, the tab 47 located at the proximal end of the electrode includes a pad, on which a wire extending along the length of the probe can be welded to establish an electrical connection between the electrode and the proximal end of the probe. These pads are described in further detail below with reference to Figures 4 to 5

[0067] As Figure 2A shown in the "A-A" cross-section of [], the substrate 41 includes an inner surface 76 facing the support sheet 36 and an outer surface 45 facing away from the support sheet 36. Usually, the thickness T0 of the substrate (i.e., the distance between the inner surface and the outer surface of the substrate) is between 5 microns and 75 microns (e.g., between 12 microns and 50 microns). At least a part of the inner surface is covered by an inner layer 70 of a conductive metal (such as gold). Usually, the inner layer 70 has a thickness T1 between 10 microns and 50 microns. Similarly, at least a part of the outer surface 45 is covered by a metal outer layer 50. Usually, the outer layer 50 has a thickness T2 between 1 micron and 5 microns.

[0068] Usually, the outer layer 50 is discontinuous because the outer layer includes a main part 54 and one or more isolation parts, and the one or more isolation parts are electrically isolated from the main part 54 through the exposed part of the substrate. These isolation parts can include one or more "islands" serving as sensing microelectrodes 56. For example, the outer layer 50 can include 3 to 7 microelectrodes 56 distributed circumferentially around the distal end. Alternatively or additionally, the isolation part can include a sensing ring electrode 43, which can be arranged near the proximal end of the electrode 40, for example.

[0069] Corresponding conductive traces 78 electrically isolated from the inner layer 70 through the exposed part of the inner surface 76 are arranged under each sensing electrode. As described below with reference to Figure 4 ​Further described, prior to forming the sensing electrodes, holes (e.g., drilled) are formed in the substrate above the traces 78, which are herein referred to as blind holes 80. Subsequently, when the sensing electrodes are deposited onto the outer surface of the substrate, the sensing electrodes at least partially fill the blind holes 80, thereby contacting the traces. Thus, during surgery, the electrogram signals from the subject's heart tissue sensed by the sensing electrodes can be transmitted through the traces 78 to the wire passing through the probe 22 to the proximal end of the probe. The signals can thus be delivered to the processor 23 for analysis.

[0070] Now additionally refer to Figure 2B , which is a schematic view of a hole through the surface of the through electrode 40 according to some embodiments of the present invention. Figure 2B corresponding to the "B - B" cross - section indicated in Figure 2A .

[0071] The substrate 41 is shaped to define a plurality of channels including a plurality of narrower channels 46 and one or more wider channels 44, which pass between the inner and outer surfaces of the substrate. Generally, each channel tapers gradually along the length of the channel, where the cross - sectional area of the channel at the inner surface of the substrate is slightly larger than the cross - sectional area at the outer surface. The cross - sectional area (or average cross - sectional area) of each narrower channel 46 is less than the cross - sectional area (or average cross - sectional area) of each wider channel 44.

[0072] In some embodiments, the channels have a circular cross - section. In such embodiments, the average diameter d0 of each narrower channel can be less than 50% (e.g., less than 25%) of the average diameter d1 of each wider channel. Alternatively or additionally, the diameter d0 can be between 5 microns and 50 microns (e.g., between 5 microns and 30 microns), and / or the diameter d1 can be between 50 microns and 300 microns. In other embodiments, at least some of the channels can have a square shape or any other suitable shape of cross - section. (In such embodiments, the average cross - sectional area of each channel can correspond to the cross - sectional area implied by the ranges for d0 and d1 above.)

[0073] Generally, the electrode includes 30 to 100 wider channels. Each wider channel 44 is plated with a plating layer 52 of conductive metal, which connects the outer layer 50 to the inner layer 70. Thus, the plated wider channels provide electrical and thermal conductivity between the metal outer layer and the metal inner layer. Additionally, the plated wider channels provide fluid channels between the interior and exterior of the electrode, such that by the pump 25 ( Figure 1)The supplied flushing fluid 39 can flow therethrough. Thus, the wider plated channels can be referred to as "flushing holes" 72. (The diameter of each flushing hole is smaller than d1 by approximately half of the thickness of the plating layer 52.) The support sheet 36 is shaped to define an opening 62 aligned with the flushing hole 72 such that the support sheet does not block the flushing hole.

[0074] Typically, the number of the narrower channels 46 is relatively large. For example, the substrate 41 can be shaped to define at least 1,000, 5,000, 10,000, or 20,000 narrower channels. Alternatively or additionally, the ratio of the narrower channels to the wider channels can be at least 300:1. Alternatively or additionally, the total area of the corresponding outer openings of the narrower channels (i.e., the openings of the narrower channels at the outer surface of the substrate) can be at least 10%, 20%, or 30% of the area of the outer surface of the substrate. Thus, for example, if the area of the outer surface of the substrate (including the narrower channels) is 27 mm 2 , and each narrower channel includes a circular outer opening with a diameter of 25 micrometers (and thus an area of 0.0005 mm 2 ), then the number of the narrower channels can be approximately 16,500 (with a total area of 8.1 mm 2 ), such that the outer openings of the narrower channels cover approximately 30% of the outer surface.

[0075] Contrary to the wider channels, the narrower channels 46 are not merely plated but are filled with corresponding columns 48 of conductive metal, which connect the outer layer 50 to the inner layer 70. (Since, as described above, the narrower channels 46 do not necessarily have a circular cross-section, the columns 48 are not necessarily cylindrical. Additionally, as described above, the cross-sectional area of each column can vary along the length of the column. It should be noted that the outer layer 50, the inner layer 70, the plating layer 52, and the columns 48 can be collectively described as a single metal body covering the substrate.) Since the number of the channels 46 is large and each of these channels is filled, a large amount of heat can be transferred via the channels 46. Thus, the filled narrower channels can be referred to as "heat dissipation holes" 74. (For the sake of illustration, Figure 2A the heat dissipation holes are not shown in the "A - A" cross-section of

[0076] Notwithstanding the above, it should be noted that in some embodiments, similar to the wider channels, the narrower channels are not filled but are merely plated. Even in such embodiments, a large amount of heat can be transferred into the electrode.

[0077] Typically, the probe 22 includes a fluid delivery tube (not shown) that extends through the entire length of the tubular body 22m of the probe 22. The fluid delivery tube is coupled distally to a diverter 60 that is shaped to define one or more fluid flow openings 64. The diverter 60 diverts fluid 39 received via the fluid delivery tube from the proximal end of the probe through the fluid flow openings 64. In such embodiments, the electrode 40 can be coupled to the base 58 of the diverter 60 such that the diverter is disposed inside the lumen of the electrode. For example, a support sheet 36 can be bonded to the base 58. Alternatively or additionally, the base 58 can be shaped to define a plurality of protrusions and the support sheet 36 can be shaped to define a plurality of complementary holes such that the protrusions snap into the holes.

[0078] As described above with reference to Figure 1 during an ablation procedure, the physician 28 contacts the tissue of the subject 26 with the electrode 40, specifically, with the outer layer 50. While contacting the tissue with the outer layer 50, the physician delivers an electric current through the outer layer into the tissue. The electric current causes heat to be generated in the tissue such that an ablation lesion is formed in the tissue. This heat is transferred to the inner layer 70 via the heat dissipation holes 74 (i.e., via the posts 48). At the same time, the pump 25 ( Figure 1 ) pumps the flushing fluid 39 through the fluid delivery tube such that the fluid flows into the interior of the electrode through the fluid flow openings 64 of the diverter 60. The fluid then exits the electrode through the openings 62 and the flushing holes 72, thereby discharging the heat from the inner layer 70 into the subject's blood.

[0079] Manufacturing the Ablation Electrode

[0080] Now refer to Figure 4 which is a flow chart of a method 82 for manufacturing the electrode 40 according to some embodiments of the present invention. Now also refer to Figure 5 which is a schematic view of the electrode 40 before its deformation according to some embodiments of the present invention. ( Figure 5 The interior of the electrode 40 is shown, i.e., the various elements coupled to the inner surface of the substrate 41.)

[0081] Figure 4 It is assumed that at least the inner surface of the substrate is initially coated with a layer of copper. Thus, the method 82 begins with an etching step 84 in which all of the other copper on the inner surface is etched away except for the copper traces 114 that will be connected to the sensing electrodes on the outside of the electrode. (Any copper on the outer surface is also etched away.) For example, this etching can be performed by placing a mask over the copper portions designated for the traces 114 and then chemically removing the exposed copper. Alternatively, if the inner surface of the substrate is initially exposed, the copper traces 114 can be deposited on the inner surface.

[0082] Subsequently, at trace deposition step 86, a constantan trace 118 for the thermocouple is deposited onto the inner surface of the substrate. The trace deposition step 86 can be performed, for example, by physical vapor deposition (PVD) such as sputter deposition. For example, a mask can be placed on all inner surface portions except those portions on the inner surface designated for the constantan traces 118. Subsequently, a seed layer of a base metal such as titanium-tungsten can be sputtered onto the substrate. Finally, constantan can be sputtered onto the base metal.

[0083] Generally, to minimize the required wiring, the constantan traces terminate at a common constantan trace pad 120. In some embodiments, holes (or "via studs") are drilled through the substrate at the location of the pads 120 prior to depositing the constantan. Subsequently, the deposited constantan fills the holes, and then pads 120 are formed above the holes. Alternatively, recesses can be drilled into the substrate such that the deposited constantan fills the recesses rather than drilling completely through the substrate. In either case, the pads 120 are "studded" to the substrate by the constantan beneath the pads. (To facilitate filling the holes or recesses, a draft angle can be used to taper the holes or recesses, as described immediately below for the narrower channels and the wider channels.)

[0084] Next, at drilling step 88, multiple narrower channels and one or more wider channels 44 are drilled through the substrate, typically using laser drilling techniques. ( Figure 5 The wider channels can be seen in, but the narrower channels cannot be seen). Generally, the channels are drilled from the inner surface of the substrate, with a draft angle such that the channels taper as they approach the outer surface; this facilitates collecting metal onto the walls of the channels during subsequent sputtering processes. Additionally, blind holes 80 can be drilled (e.g., laser drilled) through the substrate from the outer surface at those portions of the outer surface designated for the sensing electrodes, where the copper traces 114 are used as apertures. (In other words, the portions of the substrate disposed on the copper traces can be removed, thereby exposing the copper traces.) Generally, a draft angle is used for the blind holes such that the blind holes taper as they approach the inner surface of the substrate; this facilitates collecting metal onto the walls of the blind holes.

[0085] Next, at the first masking step 90, a mask is applied to the copper traces, the constantan traces, and the isolation regions 91 designated to isolate these traces (i.e., the exposed portions of the inner surface of the substrate). (The mask is not applied to the portions of the constantan traces designated for the thermocouple junctions.) A mask is also applied to additional isolation regions designated to isolate the gold traces that will intersect the constantan traces (thereby forming constantan-gold thermocouples). Additionally, a mask is applied to the isolation regions on the outer surface designated to isolate the sensing electrodes.

[0086] Subsequently, at deposition step 92, a thin gold layer is deposited onto the inner and outer surfaces of the substrate and into the channels. The deposition step 92 can be carried out, for example, by physical vapor deposition (PVD) such as sputter deposition. (Typically, a seed layer of a base metal such as titanium-tungsten is sputtered onto the substrate prior to sputtering gold.) By means of a mask, gold is not deposited onto the traces or isolation regions.

[0087] The deposited gold includes an initialization layer for the inner layer 70, outer layer 50, plating layer 52, and posts 48. The deposited gold also includes gold traces 122 that cover the constantan traces at the thermocouple junctions 124. Each gold trace 122 terminates at a corresponding gold trace pad 126. The deposited gold also includes corresponding copper trace pads 116 for each copper trace. In some embodiments, the copper trace pads 116 and / or the gold trace pads 126 are staked to the substrate as described above for the constantan-trace pads. The deposited gold also includes at least one gold pad 128 that is connected to the inner layer 70. The gold pad 128 can also be staked to the substrate.

[0088] After deposition, at mask removal step 93, the mask (and any gold deposited on the mask) is removed. Subsequently, at a second masking step 94, a mask is applied to the traces, the inner surface isolation regions surrounding the traces, and the entire outer surface of the substrate.

[0089] After the second masking step 94, while keeping the traces and the outer surface masked, at a first plating step 98, the substrate is plated in a gold plating bath for a first time interval. The plating of the substrate fills any gaps in the gold and further increases the thickness of the gold such that, for example, the thickness of the inner layer 70 reaches 5 microns to 40 microns, and the diameter of the wider channels is reduced to between 30 microns and 200 microns. Additionally, the narrower channels may be completely filled.

[0090] Typically, the plating of the substrate is electrochemical, whereby the flow of current through the gold that has already been coated on the substrate causes the gold to attract gold ions in the plating bath. The amplitude and duration of the current can be controlled such that the gold reaches the desired thickness.

[0091] After the first plating step 98, at a demasking step 100, the inner and outer surface portions of the substrate are demasked except for the isolation regions that are designated for isolating the sensing electrodes as described above. Next, at an application of surface protection layer step 101, at least one surface protection layer 130 is applied over the traces and the inner surface isolation regions. (In some embodiments, as Figure 5 shown in the inserted portion, the surface protection layer 130 is transparent or nearly transparent.)

[0092] Typically, the proximal portion of the cover tab 47 of the table protection layer 130 is shaped to define a window 132 that exposes the pad, such that the pad can be thickened during a subsequent plating process. (An additional cover 142 having a window aligned with the window 132 may cover the proximal portion of the table protection layer.) Typically, the pad is not fully exposed but remains "tethered" by the table protection layer 130, as one or more edges of each pad are covered by the edges of the window 132. Thus, the table protection layer 130 helps to hold the pad on the substrate 41 during a subsequent soldering process.

[0093] Subsequently, at the second plating step 102, the substrate is plated in a plating bath for a second time interval such that any gaps in the outer layer 50 are filled and the inner layer, outer layer, and plating layer are all thickened. For example, the second plating may increase the thickness of the inner layer to be between 10 microns and 50 microns while reducing the diameter of the wider channels to be between 15 microns and 150 microns. Typically, the final thickness of the inner layer is the same as the thickness of the table protection layer in order to obtain a smooth inner surface. (To avoid any confusion, the term "inner surface" is used herein to refer to the surface formed by the table protection layer and the inner gold layer, while the term "inner face" is used to refer to the lower surface of the substrate.) Additionally, if the narrower channels were not fully filled during the first plating step 98, these channels are fully filled during the second plating step 102. As in the case of the first plating step 98, the amplitude and duration of the current in the plating bath can be controlled such that the desired thickness is obtained.

[0094] (In some embodiments, a mask is applied to the outer surface prior to the deposition step 92 such that no gold is deposited on the outer surface during the deposition step 92. In such embodiments, after the demasking step 100 and prior to the second plating step 102, a thin gold layer is deposited on the outer surface.)

[0095] After the second plating step 102, at the drill opening step 104, an opening 62 is drilled through the support sheet 36. (As an alternative to drilling, any other suitable technique (such as chemical etching) can be used to form the opening.)

[0096] Now additionally refer to Figure 6A , which is a schematic diagram of a method for forming a recess in the surface of a support sheet 36 according to some embodiments of the present invention. Also refer to Figure 6B , which is a schematic diagram of a method for forming a protrusion on another surface of a support sheet 36 according to some embodiments of the present invention.

[0097] After the drill opening step 104, as Figure 6AAs shown in -B, a plurality of recesses 144 are formed in the outer surface 146 of the support sheet 36 (i.e., the surface of the sheet designated for bonding to the PCB), and / or a plurality of protrusions 148 are formed on the inner surface 150 of the sheet. To form the recesses 144, an outer mask 152 shaped to define a plurality of mask openings 154 is coupled to the outer sheet surface 146. Subsequently, the sheet is placed in a chemical etching bath and held in the bath for a predetermined duration such that the portions of the outer sheet surface 146 exposed by the mask openings 154 are etched away. Similarly, to form the protrusions 148, a plurality of inner masks 156 are coupled to the inner sheet surface 150, then the sheet is placed in a chemical etching bath, and it is held in the bath for a predetermined duration such that the portions of the inner surface disposed between the masks 156 are etched away.

[0098] Generally, both the recesses 144 and the protrusions 148 are formed. In some embodiments, the recesses and the protrusions are formed simultaneously. (In such embodiments, the height of the protrusions is approximately equal to the depth of the recesses). For example, returning to Figure 4 , at the third masking step 105, the outer mask 152 can be coupled to the outer surface of the sheet, and the inner mask 156 can be coupled to the inner surface of the sheet. Subsequently, at the chemical etching step 107, the sheet can be placed in the bath such that both the recesses and the protrusions are formed. After forming the recesses and the protrusions, the sheet is removed from the bath at the sheet removal step 109.

[0099] In other embodiments, the recesses and the protrusions are formed at different times. For example, during the first chemical etching step, the outer surface of the sheet can be masked by the outer mask 152 while the inner surface of the sheet is fully masked such that the recesses rather than the protrusions are formed. Subsequently, during the second chemical etching step, the inner surface of the sheet can be masked by the inner mask while the outer surface of the sheet is fully masked such that the protrusions are formed. Advantageously, this technique facilitates forming a protrusion height different from the depth of the recesses because the respective durations of the two chemical etching steps can be different from each other.

[0100] In some embodiments, each mask opening 154 is circular such that each recess 144 has a circular perimeter. In such embodiments, the diameter L2 of each mask opening can be between 0.01 and 0.2 mm. Alternatively, some or all of the mask openings can have any other suitable shape.

[0101] The mask openings 154 (and thus, the recesses 144) can be arranged in a grid pattern or any other suitable arrangement. For example, as Figure 6AAs shown, multiple circular mask openings can be arranged in a closely packed pattern, where the distance L3 between the respective centers of adjacent mask openings is between 0.05 mm and 0.5 mm. In some embodiments, L3 is approximately twice L2.

[0102] In some embodiments, each inner mask 156 is rectangular such that each protrusion 148 (inner surface) has a rectangular perimeter. For example, each inner mask can be square, having a length L0 between 0.01 mm and 0.2 mm. Alternatively, some or all of the inner masks can have any other suitable shape. For example, each inner mask can be star-shaped such that the perimeter of each of the protrusions (inner surface) is star-shaped. Examples of such shapes (which provide a relatively large surface area for contact with the flushing fluid and a large number of edges for generating turbulence) include the shape of an N-sided star, where N is three or more.

[0103] The inner masks 156 (and thus the protrusions 148) can be arranged in any suitable arrangement, such as a grid pattern. For example, multiple square inner masks can be arranged in a grid where the distance L1 separating adjacent squares is between 0.05 mm and 0.5 mm. In some embodiments, the distance between adjacent squares is approximately equal to the length of each square, i.e., L1 is approximately equal to L0.

[0104] Generally, the area of each opening 154 is less than the area of each inner mask 156, and the inner mask is aligned with the outer mask such that the entire perimeter of each opening faces the corresponding inner mask. (This reduces the risk of accidentally forming vias during the chemical etching process). Due to this sizing and alignment, each of the recesses is completely opposite a protrusion (as shown below Figure 7 as shown).

[0105] As an alternative to chemical etching, other techniques such as laser etching can be used to form the protrusions 148 and / or the recesses 144.

[0106] After forming the recesses and / or protrusions, at the bonding step 106, an adhesive is applied between the outer sheet surface 146 and the smooth inner surface formed by the surface protection layer 130 and the inner layer 70. The adhesive fills the recesses and bonds the outer sheet surface 146 to the inner surface of the PCB. Generally, the support sheet is bonded to the inner surface such that the opening 62 is aligned with the flushing hole 72. Generally, the area of the opening is larger than the area of the flushing hole to compensate for any minor misalignment that occurs when bonding the support sheet.

[0107] Next, at deformation step 108, the electrode 40 is deformed into a desired shape. For example, the electrode can be inserted into a forming jig that forms the electrode around a suitable mandrel. After inserting the electrode into the jig, the jig is placed in an oven. Subsequently, the oven heats the electrode to a suitable temperature while applying pressure to the electrode. The combination of heat and pressure causes the electrode to bond itself into the desired shape.

[0108] Generally speaking, the substrate and the support sheet can be deformed into any desired shape. However, typically, during deformation step 108, the substrate and the support sheet are formed to define a lumen that is at least partially enclosed by the inner surface of the sheet. For example, as referred to above with reference to Figure 2A and Figure 3 the substrate and the support sheet can be formed to define a cannula.

[0109] Typically, to facilitate the manufacture of a cannula-shaped electrode, the substrate 41 includes two portions that are continuous with each other: a distal circular portion 41a and a proximal rectangular portion 41b. Similarly, the support sheet 36 includes two portions that are continuous with each other: a distal support portion 36a, which typically includes a plurality of spokes 134 radiating from a central hub 136; and a proximal support portion 36b. During bonding step 106, the distal support portion 36a is bonded to the inner surface of the circular portion 41a, and an adhesive is applied to the outer surface of the spokes 134. (These surfaces are opposite the surfaces shown in Figure 5 .) Additionally, the proximal support portion 36b is bonded to the inner surface of the rectangular portion 41b, leaving some distal portions of this inner surface exposed. An adhesive is applied to the outer surface of the overhanging tab 138 of the proximal support portion 36b, which overhangs the side of the rectangular portion 41b. (The proximal support portion 36b can also overhang the proximal end of the rectangular portion 41b.)

[0110] Subsequently, during deformation step 108, the distal support portion 36a and the circular portion 41a are folded over the top of the mandrel, while the proximal support portion 36b and the rectangular portion 41b are rolled around the mandrel. To maintain this configuration, the outer surface of the spokes 134 is bonded to the exposed distal portion of the inner surface of the rectangular portion 41b, and the outer surface of the tab 138 is bonded to the opposite end of the proximal support portion 36b. (Additionally, the inner surface of at least one spoke can be bonded to the tab 138.) Thus, the distal support portion 36a and the circular portion 41a are formed into a dome-shaped portion 40a ( Figure 2A ), while the proximal support portion 36b and the rectangular portion 41b are formed into a cylindrical portion 40b.

[0111] Subsequently, at welding step 110, the wire is welded to the pad. Specifically, the delivery from the generator 27 ( Figure 1The wire for the RF current of ( ) is welded to the gold pad 128, and the other wires for delivering signals to the processor 23 are welded to other pads.

[0112] Finally, at the coupling step 112, the electrode is coupled to the probe. For example, the proximal support portion 36b can be bonded to the base 58 of the shunt ( Figure 3 ). Alternatively or additionally, as described above with reference to Figure 3 , the protrusion belonging to the base 58 can be snapped into the complementary hole 140 in the proximal support portion 36b. Subsequently, the shunt can be coupled to the fluid delivery tube belonging to the probe. (Alternatively, the shunt can be coupled to the fluid delivery tube before coupling the electrode to the shunt).

[0113] In other embodiments, the substrate and the support sheet are shaped to define a ring or an arc. In some embodiments, a plurality of such annular electrodes and / or arcuate electrodes are coupled to each other at the distal end of the probe so as to define a sphere. By means of the space between the rings and / or arcs, blood can flow through the sphere during the ablation process. Therefore, the heat generated by ablation can be directly transferred from the protrusion 148 to the blood of the subject.

[0114] Generally speaking, any suitable masking technique can be used at each step where a mask is required. Examples of suitable masks include liquid and film photoresists.

[0115] As an alternative or supplement to the traces described above, any other suitable electrical or electronic components can be deposited on the inner surface of the substrate. Such components can include a thermistor for measuring tissue temperature, a pressure sensor for measuring the pressure applied to the distal end of the catheter, and / or an electromagnetic sensor for navigating the probe. Whenever such a masking or covering operation is required, these components (as well as the appropriate surrounding isolation zones) can be masked or covered, as described above for the traces.

[0116] Note that the scope of the present disclosure includes any suitable modifications to the method 82 with respect to the order of performing steps and / or with respect to the various materials used, which will be obvious to those skilled in the art. For example, any suitable conductive metal can be used instead of copper, gold, or constantan.

[0117] Heat Transfer

[0118] Now refer to Figure 7 , which schematically shows the transfer of heat into the electrode 40 according to some embodiments of the present invention.

[0119] As described above with reference to Figure 4As described above, the adhesive 158 bonds the support sheet 36 to the inner surface of the PCB. Advantageously, the adhesive 158 fills the recess 144, thereby improving the adhesion of the support sheet to the PCB while also reducing the amount of adhesive between the non-recessed portion of the outer sheet surface and the PCB. In other words, by virtue of the adhesive gathered in the recess, the outer sheet surface 146 can contact or nearly contact the inner surface of the PCB. Therefore, more heat can be transferred to the support sheet and, specifically, to the protrusion 148.

[0120] As further described above, during and / or after the application of the ablation current, the fluid 39 is made to flow over the surface of the protrusion 148. By virtue of the large surface area provided by the protrusion and / or by virtue of the turbulence generated by the protrusion, a large amount of heat is transferred from the protrusion to the fluid 39. As referred to above Figure 4 as described, in some embodiments, the blood of the subject rather than the fluid 39 flows over the surface of the protrusion, such that heat is transferred directly from the protrusion to the blood.

[0121] In some embodiments, the height H1 of each protrusion and / or the depth H2 of each recess is between 5% and 60% of the thickness H0 of the sheet. (As referred to above Figure 4 as described, by forming the recess and the protrusion in two separate chemical etching steps, the depth of the recess can be made different from the height of the protrusion.) For example, if H0 is between 0.025 and 0.2 mm, then each of H1 and H2 can be between 0.00125 and 0.12 mm.

[0122] Generally speaking, the embodiments described herein can be combined with any of the embodiments described in U.S. Patent Application Publication 2018 / 0110562 or U.S. Patent Application 15 / 793126, the disclosures of each of these patents being incorporated herein by reference.

[0123] Those skilled in the art should understand that the present invention is not limited to what is specifically shown and described above. On the contrary, the scope of the embodiments of the present invention includes both combinations and sub-combinations of the various features described above, as well as variations and modifications that are not within the scope of the prior art that those skilled in the art would think of upon reading the above description. The documents incorporated by reference into this patent application are considered an integral part of this application, except that if any terms defined in these incorporated documents conflict with the definitions explicitly or implicitly given in this specification, only the definitions in this specification should be considered.

Claims

1. An apparatus for an ablation procedure, comprising: an in-vivo probe; and an electrode coupled to a distal end of the in-vivo probe, the electrode comprising: a flexible electrically insulating substrate comprising a substrate surface; a conductive metal layer covering at least a portion of the substrate surface; a metal sheet comprising an inner sheet surface and an outer sheet surface, the outer sheet surface being shaped to define a plurality of recesses; and an adhesive filling the recesses and bonding the outer sheet surface to the conductive metal layer.

2. The apparatus according to claim 1, wherein the flexible electrically insulating substrate and the metal sheet are shaped to define a lumen, the lumen being at least partially encapsulated by the inner sheet surface.

3. The apparatus according to claim 2, wherein the flexible electrically insulating substrate and the metal sheet are shaped to define a cannula.

4. The apparatus according to claim 2, wherein the distal end of the probe comprises a diverter configured to divert fluid received from a proximal end of the probe, and wherein the inner sheet surface is coupled to the diverter such that the diverter is disposed inside the lumen.

5. The apparatus according to claim 1, wherein the flexible electrically insulating substrate and the metal sheet are shaped to define a ring.

6. The apparatus according to claim 1, wherein the flexible electrically insulating substrate and the metal sheet are shaped to define an arc.

7. The apparatus according to claim 1, wherein the metal sheet comprises cobalt-chromium.

8. The apparatus according to claim 1, wherein the conductive metal layer comprises gold.

9. The apparatus according to claim 1, wherein each of the recesses has a circular perimeter.

10. A method of manufacturing an apparatus for an ablation procedure, comprising: forming a plurality of recesses in an outer surface of a metal sheet; after forming the recesses in the outer surface, applying an adhesive between the outer surface and a conductive metal layer covering at least a portion of a substrate surface of a flexible electrically insulating substrate such that the adhesive fills the recesses and bonds the outer surface to the conductive metal layer; and after applying the adhesive, coupling the metal sheet to a distal end of an in-vivo probe.

11. The method according to claim 10, wherein forming the recesses comprises forming the recesses by: coupling a mask shaped to define a plurality of openings to the outer surface of the metal sheet, and placing the metal sheet in a chemical etching bath such that portions of the outer surface exposed by the openings are etched away.

12. The method according to claim 11, wherein each of the openings is circular.

13. An apparatus for an ablation procedure, comprising: an in-vivo probe; and an electrode coupled to a distal end of the in-vivo probe, the electrode comprising: a flexible electrically insulating substrate comprising a substrate surface; a conductive metal layer covering at least a portion of the substrate surface; and A metal sheet, the metal sheet including an outer sheet surface and an inner sheet surface, the outer sheet surface being bonded to the conductive metal layer, and the inner sheet surface being shaped to define a plurality of protrusions.

14. The apparatus according to claim 13, wherein the flexible electrically insulating substrate and the metal sheet are shaped to define a lumen, the lumen being at least partially encapsulated by the inner sheet surface.

15. The apparatus according to claim 14, wherein the flexible electrically insulating substrate and the metal sheet are shaped to define a sleeve.

16. The apparatus according to claim 14, wherein the distal end of the probe includes a diverter configured to divert fluid received from the proximal end of the probe, and wherein the inner sheet surface is coupled to the diverter such that the diverter is disposed inside the lumen.

17. The apparatus according to claim 13, wherein the flexible electrically insulating substrate and the metal sheet are shaped to define a ring.

18. The apparatus according to claim 13, wherein the flexible electrically insulating substrate and the metal sheet are shaped to define an arc.

19. The apparatus according to claim 13, wherein the metal sheet includes cobalt chromium.

20. The apparatus according to claim 13, wherein the conductive metal layer includes gold.

21. The apparatus according to claim 13, wherein the perimeter of each of the protrusions is rectangular.

22. The apparatus according to claim 13, wherein the perimeter of each of the protrusions is star-shaped.

23. A method of manufacturing an apparatus for an ablation procedure, comprising: forming a plurality of protrusions on an inner surface of a metal sheet; after forming the protrusions on the inner surface, bonding an outer surface of the metal sheet to a conductive metal layer that covers at least a portion of a substrate surface of a flexible electrically insulating substrate; and after bonding the outer surface of the metal sheet to the conductive metal layer, coupling the metal sheet to a distal end of an in-vivo probe.

24. The method according to claim 23, wherein forming the protrusions includes forming the protrusions by: coupling a plurality of masks to the inner surface, and placing the metal sheet in a chemical etching bath such that one or more portions of the inner surface disposed between the masks are etched away.

25. The method according to claim 24, wherein each of the masks is rectangular.

26. The method according to claim 24, wherein each of the masks is star-shaped.

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