Patent Publication Number: US-2021169523-A1

Title: Rail and/or anchor system for transjugular intrahepatic protosystemic shunt procedure

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of co-pending U.S. Provisional Patent Application Ser. No. 62/610,852 filed Dec. 27, 2017, which is incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure is generally directed to medical procedures, and more importantly to an improved Transjugular Intrahepatic Portosystemic Shunt (TIPS) procedure and system. 
     BACKGROUND OF THE INVENTION 
     A Transjugular Intrahepatic Portosystemic Shunt (TIPS) procedure includes connecting the portal vein (PV) to the hepatic vein (HV) in the liver. The purpose of the procedure is to divert blood from entering the liver, and may be executed on patients with cirrhosis and internal bleeding and/or ascites. 
     The most difficult portion of a TIPS procedure is accessing the portal vein from the hepatic vein. The device that is currently available requires significant expertise, and typically requires a 10 French sheath to be placed into the hepatic vein. A significant problem is that the 10 French sheath that is placed in to the hepatic vein often falls out of the hepatic vein and accessing the hepatic vein needs to be repeated. Also, aiming at the portal vein is usually performed blindly and aiming at and entering the portal vein can be difficult. 
     Existing TIPS devices are over 25 years old and do not have any provision for maintaining access in the hepatic vein or for performing repeat hepatic portal venography while attempting to create TIPS via the a same 10 French sheath that has been initially inserted into the hepatic vein during the procedure. 
     Therefore, there exists a need for a system and method to maintain access to the hepatic vein and also a system and method for allowing repeated portal venography. 
     SUMMARY OF THE INVENTION 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure. 
     As one example, disclosed is a rail and/or anchor system for transjugular intrahepatic portosystemic shunt procedures, the system comprising: 
     a rail and/or anchor line or stiff shaft configured for being anchored to surrounding tissue and/or stiff enough configured to guide the displacement of at least one of a needle and an outer sheath. 
     In another aspect, the rail and/or anchor line is a balloon catheter, and a balloon of the anchor line is configured to selectively anchor the anchor line to surrounding tissue by the balloon being inflated, and unanchor the anchor line to surrounding tissue by the balloon being deflated. If a shaft of the catheter is stiff or stiffened by a wire, it can be used as a rail with the balloon inflated or deflated. 
     In another aspect, the rail and/or anchor line is a balloon catheter configured for executing wedge venography by discharging a gas or contrast through the balloon catheter while a balloon of the balloon catheter is inflated. 
     In another aspect, the rail and/or anchor line is a balloon catheter configured for measuring pressure at a tip of the balloon catheter while the balloon is inflated. 
     In another aspect, the rail and/or anchor line includes one or more hooks for anchoring the anchor line to surrounding tissue. 
     In another aspect, the rail and/or anchor line includes one or more hooks for anchoring the anchor line to surrounding tissue, and the one or more hooks are selectively advanceable and retractable. 
     In another aspect, the rail and/or anchor line includes a balloon and one or more hooks to anchor the anchor line to surrounding tissue. 
     As another example, disclosed is a rail and/or anchor system for transjugular intrahepatic portosystemic shunt procedures, the system comprising: 
     an inner rail;
 
an outer sheath configured to be advanced and retracted over the inner rail;
 
a needle configured to be advanced between the inner rail and the outer sheath; and
 
the inner rail with or without an anchor, the anchor configured to anchor the inner rail to surrounding tissue.
 
     In another aspect, the inner rail includes a balloon catheter, and the anchor is a balloon of the balloon catheter, and the balloon is configured to anchor the inner rail to the surrounding tissue by being inflated and unanchor the inner rail to the surrounding tissue by being deflated. 
     In another aspect, the inner rail includes a balloon catheter for executing wedge venography by discharging a gas or contrast through the balloon catheter while a balloon of the balloon catheter is inflated. 
     In another aspect, the inner rail includes a balloon catheter for measuring pressure at a tip of the balloon catheter while the balloon is inflated. 
     In another aspect, the anchor includes one or more hooks to hook onto surrounding tissue. 
     In another aspect, the anchor includes one or more hooks to hook onto surrounding tissue, the one or more hooks being selectively advanceable and retractable. 
     In another aspect, the anchor includes a balloon and one or more hooks to anchor the inner rail to surrounding tissue. 
     As another example, disclosed is a method of performing a transjugular intrahepatic portosystemic shunt procedure, the method comprising: 
     advancing a rail and/or anchor line into a patient;
 
anchoring the anchor line to surrounding tissue or positioning the rail in the hepatic vein; and
 
guiding the displacement of at least one of a needle and an outer sheath via the rail and/or anchor line.
 
     In another aspect, the anchor line is a balloon catheter, and a balloon of the balloon catheter is configured to selectively anchor the anchor line to surrounding tissue by the balloon being inflated, and unanchor the anchor line by the balloon being deflated; and 
     the method further comprises inflating the balloon to anchor the anchor line. 
     Alternatively the catheter can be used as a rail if the catheter is stiffened either by a wire or by the catheter material. 
     In another aspect, the anchor line is a balloon catheter configured for executing wedge venography by discharging a gas or contrast through the balloon catheter while a balloon of the balloon catheter is inflated; and 
     wherein the method further comprises executing wedge venography via the balloon catheter. 
     In another aspect, the anchor line is a balloon catheter configured for measuring pressure at a tip of the balloon catheter while the balloon is inflated; and the method further comprises measuring pressure at the tip of the balloon catheter while the balloon is inflated. 
     In another aspect, the anchor line includes one or more hooks for anchoring the anchor line to surrounding tissue; and the method further comprises anchoring the anchor line via the one or more hooks. 
     In another aspect, the anchor line includes a balloon and one or more hooks to anchor the anchor line to surrounding tissue; and 
     wherein the method further comprises anchoring the anchor line via at least one of the balloon and the one or more hooks. 
     These and other objects, features, and advantages of the present invention will become more readily apparent from the attached drawings and the detailed description of the preferred embodiments, which follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The preferred embodiments of the invention will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the invention, where like designations denote like elements, and in which: 
         FIG. 1  schematically presents an exemplary method of performing a transjugular intrahepatic portosystemic shunt procedure, in accordance with aspects of the present disclosure; 
         FIG. 2  schematically presents an outer sheath, in accordance with aspects of the present disclosure; 
         FIG. 3  schematically presents an outer sheath receiving an anchor line, rail, and/or stiff shaft catheter, and a needle, in accordance with aspects of the present disclosure; 
         FIG. 4  schematically presents a balloon having been inflated, in accordance with aspects of the present disclosure; 
         FIG. 5  schematically presents an exemplary use of the disclosed system, where a balloon has been inflated and a needle is puncturing nearby tissue, in accordance with aspects of the present disclosure; 
         FIG. 6  schematically presents the anchor line with no hooks or retracted one or more hooks, and a deflated balloon, in accordance with aspects of the present disclosure; 
         FIG. 7  schematically presents the rail and/or anchor line with extended two hooks, and an inflated balloon, in accordance with aspects of the present disclosure; 
         FIG. 8  schematically presents the anchor line with extended two hooks, and a deflated balloon, in accordance with aspects of the present disclosure; 
         FIG. 9  schematically presents the anchor line with one extended hook, and a deflated balloon, in accordance with aspects of the present disclosure; and 
         FIG. 10  schematically presents an anchor line having a single hook, without a balloon, in accordance with aspects of the present disclosure. 
     
    
    
     Like reference numerals refer to like parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the described embodiments or the application and uses of the described embodiments. As used herein, the word “exemplary” or “illustrative” means “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” or “illustrative” is not necessarily to be construed as preferred or advantageous over other implementations. All of the implementations described below are exemplary implementations provided to enable persons skilled in the art to make or use the embodiments of the disclosure and are not intended to limit the scope of the disclosure, which is defined by the claims. For purposes of description herein, the terms “upper”, “lower”, “left”, “rear”, “right”, “front”, “vertical”, “horizontal”, and derivatives thereof shall relate to the invention as oriented in  FIG. 2 . Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. 
     Disclosed herein is a rail and/or anchor system  200  ( FIGS. 2-10 ) and method  100  ( FIG. 1 ) for transjugular intrahepatic portosystemic shunt procedures. As shown in  FIG. 3 , system  200  may include a rail and/or anchor line  302  configured for being anchored or secured (held in place) by its stiff shaft to surrounding tissue and configured to guide the displacement of at least one of a needle  304  and an outer sheath  306  (e.g. a needle  304  and/or an outer sheath  306 ). For example, the anchor line  302  may allow the sheath to pass through itself, or outside itself in between an outer wall of the anchor line  302  and an outer sheath  306 . 
     In one example, turning to  FIG. 4 , the anchor line  302  is, or includes, a balloon catheter. A balloon  402  of the balloon catheter may be configured to selectively anchor the anchor line  302  to surrounding tissue by the balloon  402  being inflated ( FIG. 5 ). The balloon may unanchor the anchor line  302  to surrounding tissue by the balloon  402  being deflated ( FIG. 6 ). The balloon catheter may be configured for executing wedge venography by discharging a gas or contrast through the balloon catheter while a balloon  402  of the balloon catheter is inflated ( FIG. 5 ). The balloon catheter may be configured for measuring pressure at a tip of the balloon catheter while the balloon  402  is inflated or deflated. The balloon catheter may be configured to function as a rail without an anchor if it is stiff shafted by means of wall stiffness or stiff wire. 
     The anchor line  302  may include one or more hooks  702  ( FIG. 7 ) for anchoring the anchor line  302  to surrounding tissue. The one or more hooks  702  may be selectively advanceable and retractable ( FIGS. 6 and 7 ). The anchor line  302  may include a balloon  402  and one or more hooks  702  together, to anchor the anchor line  302  to surrounding tissue. 
     As another example, the system  200  includes an inner rail  302  and an outer sheath  306  configured to be advanced and retracted over the inner rail  302 . The inner rail may include none or one or more features and elements of the anchor line  302  described above. The outer sheath  306  may be a 10 Fr sheath, for example. But any appropriate sheath may be included for enabling the features of the present disclosure. The system may include a needle  304  configured to be advanced between the inner rail  302  and the outer sheath  306 . The inner rail  302  may include an anchor  404 . The anchor  404  may be configured to anchor the inner rail  302  to surrounding tissue. 
     The inner rail  302  may include a balloon catheter, and the anchor  404  may be a balloon  402  ( FIG. 4 ) of the balloon catheter. The balloon  402  may be configured to anchor the inner rail  302  to the surrounding tissue by being inflated. The balloon  402  may be configured to unanchor the inner rail  302  to the surrounding tissue by being deflated. 
     The inner rail  302  may include a balloon catheter for executing wedge venography by discharging a gas or contrast through the balloon catheter while a balloon  402  of the balloon catheter is inflated. The inner rail  302  may include a balloon catheter for measuring pressure at a tip of the balloon catheter while the balloon  402  is inflated. 
     The anchor  404  may include one or more hooks  702  ( FIG. 7 ) to hook onto surrounding tissue. The one or more hooks  702  may be selectively advanceable and retractable. The anchor  404  may include a balloon  402  and one or more hooks  702 , together, to anchor the inner rail  302  to surrounding tissue. 
     Further disclosed is a method  100  of performing a transjugular intrahepatic portosystemic shunt procedure. The method  100  may generally include advancing a rail and/or anchor line  302  into a patient, anchoring the anchor line  302  to surrounding tissue or using the rail positioned in the hepatic vain, and guiding the displacement of at least one of a needle  304  and an outer sheath  306  via the anchor line  302 . 
     More particularly, with reference to  FIG. 1 , the method may include: at  102 , advancing a sheath into a hepatic vein, at  104  advancing a balloon catheter through the sheath, at  106  expanding the balloon for pressure measurement, at  108  obtaining a portal venogram, at  110  advancing a needle to a tip of the sheath (either within the balloon catheter or between the balloon catheter and the sheath), at  112  retracting the sheath to the IVC, at  114  retracting the needle and/or the sheath while balloon remains anchored or positioned in hepatic vein to a desired level for attempt at PV entry, at  116  advancing the needle to puncture the hepatic vein and enter the portal vein, at  118  determining if the portal vein has been entered by the needle, at  118 N if the portal vein is not entered by the needle retracting the needle into the sheath and readvancing the sheath into the hepatic vein over the balloon catheter, rail, and/or anchor, at  118 Y ending the method if the portal vein has been entered by the needle, the balloon catheter, anchor, and/or rail is removed, the TIPS procedure then proceeds as usual. Step  118  and  118 N may be repeated until the needle has entered the portal vein. After  118 N, the method goes back to step  110  and is repeated. 
     In another example, the method includes removing a dilator after the sheath is advanced into the hepatic vein. Next, the balloon catheter may be advanced to a tip of the sheath. Next, free hepatic vein pressure may be measured, and next the balloon may be expanded to measure wedge pressure. Next, portal venography may be executed. For example, wedge portal venography may be performed while the needle is in the liver parenchyma to determine the position of the needle&#39;s tip in relation to the portal vein, Next, the a needle may be advanced to the tip of the sheath. Next, the sheath may be retracted while the balloon catheter and the needle remain in place. Next the needle may be retracted while the balloon remains anchored (or positioned) in the hepatic vein. When the needle is advanced to a desired point in the hepatic vein, the needle may be advanced to puncture the hepatic vein with the aim of entering the liver parenchyma and the portal vein. Next, if the portal vein was entered by the needle, the balloon catheter and/or anchor may be removed and the TIPS procedure may be subsequently completed. 
     If the portal vein is not entered by the needle, the needle may be retracted into the sheath, and the sheath may be re-advanced into the hepatic vein over the balloon catheter, anchor, and/or rail, and the needle may be re-advanced to the tip of the sheath. Next, the sheath may be retracted and the above described wedge portal venography and subsequent steps may be re-performed or re-attempted until the needle enters the liver parenchyma and portal vein. 
     In the method  100 , the rail and/or anchor line  302  may be a balloon catheter, and a balloon  402  of the balloon catheter may be configured to selectively anchor the anchor line  302  to surrounding tissue by the balloon  402  being inflated, and unanchor the anchor line  302  by the balloon  402  being deflated. The method  100  may further include inflating the balloon  402  to anchor the anchor line  302 . Alternatively, the rail and/or anchor line  302  can be used as a rail without anchoring if the catheter is positioned and maintained in the hepatic vein and the catheter was stiff or stiffened by a stiff wire. 
     In the method  100 , the anchor line  302  may be a balloon catheter configured for executing wedge venography by discharging a gas or contrast through the balloon catheter while a balloon  402  of the balloon catheter is inflated. The method may further include executing wedge venography via the balloon catheter. 
     In the method  100 , the anchor line  302  may be a balloon catheter configured for measuring pressure at a tip of the balloon catheter while the balloon  402  is inflated. The method  100  may further include measuring pressure at the tip of the balloon catheter while the balloon  402  is inflated. 
     In the method  100 , the anchor line  302  may include one or more hooks  702  for anchoring the anchor line  302  to surrounding tissue. The method  100  may further include anchoring the anchor line  302  via the one or more hooks  702 . 
     In the method  100 , the anchor line  302  may include a balloon  402  and one or more hooks  702 , together, to anchor the anchor line  302  to surrounding tissue. The method may further include anchoring the anchor line  302  via at least one of the balloon  402  and the one or more hooks  702 . 
     In other words, the disclosed TIPS system and method primarily maintains access in the hepatic vein and also limits the need for multiple passes through the parenchyma of the liver. For example, a stiff wire (inner rail  302  or anchor line  302 ) in a sheath (outer sheath  306 ) may maintain access of the hepatic vein while attempts at entering the portal vein can be made anywhere along the hepatic vein (even at the hepatic vein IVC junction without falling out of the hepatic vein). Maintaining access of the hepatic vein without the fear of the sheath falling out would allow the operator to puncture the hepatic vein close to the IVC which may be a preferred location for the puncture. 
     The method  100  may include using an occlusion balloon type catheter (including balloon  402 ) through the sheath to act as an anchor (e.g. anchor  404 ) and also allows one to perform repeated balloon occlusion venography to allow the operator to target a visualized portal vein (i.e. visualized via the venography). A balloon occlusion gives the advantages of allowing a proximal hepatic vein puncture and an added advantage of being able to perform repeated wedge portal venography. 
     As a non-limiting example, the disclosed system may be provided as a kit, including a stiff guidewire, Robust 10 Fr Sheath, a TIPS needle, and an occlusion balloon, or any appropriate element described herein. The stiff guidewire (inner rail  302  or anchor line  302 ) maintains access in the hepatic vein. The 10 Fr sheath is advanceable over the guidewire into the hepatic vein. An occlusion balloon may be inserted through the sheath over the guidewire or directly and the guidewire may be removed. It is to be understood that removing the guidewire may be optional, and the guidewire may or may not include the herein disclosed hook anchors. The needle may be advanced through the sheath into the hepatic vein. The sheath may be withdrawn over the guidewire, catheter, and/or rail to expose the needle. The needle may be retracted to the desired location in the hepatic vein and exit the hepatic vein and enter the liver parenchyma anywhere along the hepatic vein without fear of losing access due to the disclosed innovation of anchoring the inner rail  302  or anchor line  302  or by means of a stiff shaft catheter (no anchors). The balloon catheter may be used for repeat wedged venography. 
     When a balloon is inflated and obstructs the flow in the hepatic vein, the pressure reading at the tip of the catheter will read the pressure in the portal vein, where this pressure may be referred to as wedge pressure. Wedge pressure may reflect a true portal pressure that is measured directly in the portal vein. One issue in the prior art is that repeat portal venography is not possible once entry into the portal vein is attempted. It may be important to know the pressure before an attempt is made to insert the needle into the portal vein. This pressure may be obtained by a pressure reading at a tip of the balloon catheter while the balloon is inflated. The wedge pressure may be determined while the balloon is inflated, because the balloon obstructs outflow through the hepatic vein, and the portal venous pressure is transmitted through the liver parenchyma to the tip of the balloon catheter. 
     Therefore, the balloon catheter may be used for at least two functions during the TIPS procedure. One function of the balloon catheter is to execute repeat portal venograms at any point during the procedure and a second function is to maintain access of the hepatic vein so that the TIPS sheath used to access the hepatic vein does not fall out of the hepatic vein and the sheath can be pulled back into the IVC or right atrium and then re-advanced back into the hepatic vein over the balloon catheter if needed. A stiffened balloon catheter may be used to add both stiffness to the device during insertion and to effect repeated portal venograms and to advance the sheath over it as a rail even if the sheath is retracted into the IVC or Right Atrium. In a wedge portal venogram, the balloon may be inflated and contrast or carbon dioxide gas may be injected to show the portal vein. 
     The carbon dioxide gas may be any appropriate gas, without departing from the scope of this disclosure. The carbon dioxide gas is discharged distally with respect to the balloon and its respective catheter (e.g. the gas may be discharged from a tip of the balloon catheter). In some examples, the carbon dioxide gas may be injected through the outer sheath (e.g. 10 fr sheath), external to the balloon catheter. In yet another example, carbon dioxide gas may be proximally located with respect to an inflated balloon, without departing from the scope of the present disclosure. It is to be understood that the term proximal refers to a general area or direction away from a working tip of the device, and distal refers to a general area of direction toward a working tip of the device. 
     In one example, the required stiffness of the device (e.g. for advancing the sheath into the hepatic vein) may be provided solely, or majorly, by a selected material of the 10 Fr sheath, or by a selected material of the balloon catheter, or by a selected material of guide wire, or a combination thereof. The stiffness of the device is to be adjusted, selected, or configured to prevent herniation during inserting the device or advancement of the sheath over the catheter. 
     This new system simplifies the TIPS procedure. The guidewire or occlusion balloon will maintain hepatic vein access. The needle will be able to be advanced (e.g. bareback) through the 10 Fr sheath. In some examples, the needle may need to be protected by a 10 Fr dilator to advance it safely through the 10 Fr sheath. The 10 Fr sheath may need to be strengthened so as to allow the needle (e.g. needle  304 ) to be advanced bareback. A wire and/or balloon will be specific for this application so that the wire/balloon would fit the 10 Fr sheath. In addition an appropriate balloon catheter to dilate the liver parenchyma and a covered stent may be required to complete the TIPS procedure. 
     It is anticipated that various other configurations may anchor the catheter, sheath, or generally the device, in the hepatic vein to thereby implement a rail for the sheath to move up and down the rail. The balloon catheter can be used as an anchor, a catheter (without a balloon) can be used as an anchor, or just a wire with an anchor element, such as a hook, can be used as an anchor. In another example, a wire that is stiff enough can be used as an anchor. It is to be understood that the term “hook” may refer to any appropriate structure that selectively (or temporarily) attaches to tissue, and it may be a J-shaped or L-shaped structure having a pointed or sharp distal end. 
     A balloon catheter may have an inflatable and deflatable balloon. Anchor elements such as hooks or spokes, similar to spokes or ribs of an umbrella, may be selectively deployed from the catheter to anchor into hepatic tissue and can be selectively released from the hepatic tissue to remove the catheter. The anchor may be a balloon, and/or have one or more hooks. In one example, the balloon may be eliminated from the anchor, such that a wire has an anchor mechanism without a balloon. The hook anchor may be retractable within its respective catheter. 
     It is to be understood that reference to a balloon catheter and/or a guide wire may refer to the above referenced anchor line  302  and/or inner rail  302 . Therefore, a needle may pass through the balloon catheter, or through a sheath that holds a wire having one or more hooks. The needle may also pass along an outer portion of the balloon catheter between the balloon catheter and an outer sheath (e.g. 10 fr sheath). In one example, the device includes a balloon catheter and a needle passing within the balloon catheter, or through a hole in a wall of the balloon catheter. 
     It is anticipated that, without departing from the scope of this disclosure, that a stiff shaft balloon catheter/sheath may have a side hole allowing for needle exit from the catheter/sheath. Such an aperture may be approximately 4 cm from the distal end of the catheter/sheath. The needle may exit the hole either by advancing the needle from a hub (proximal) end all the way out, or the needle may be built into the catheter/sheath and advanced out into the liver. The end 4 cm will anchor the catheter/sheath and be used for contrast or carbon dioxide portography. 
     Furthermore, it is anticipated that the disclosure may be used with an intravascular echo type catheter having a built in needle. The echo may visualize the portal vein from the hepatic vein. When the portal vein is in sight the needle may be advanced through a window in the catheter directly into the portal vein under echo visualization. The intravascular echo has the advantage of being over a wire allowing proximal hepatic vein puncture and the advantage of direct visualization of the portal vein and direct visualization of the needle as it tracks through the liver parenchyma into the portal vein. Incorporating this echo technique may allow a simpler method for creating TIPS. This echo technique may be executed by a kit, where the kit includes an intravascular echo device having a needle window. The intravascular echo may be inserted over the wire through the 10 Fr sheath and the needle can be advanced under direct visualization anywhere along the hepatic vein without losing access of the hepatic vein. If the intravascular echo device with a side hole for a needle is used there will be the added benefit of direct visualization of the portal vein while the needle is advanced. 
     ICE (intracardiac echo) catheters that are currently available will require significant non-obvious modifications that will allow a needle to be advanced through a window that is directed at the portal vein. This can be made by using ICE catheters and creating a side channel. Currently an IVUS catheter (not ICE) which is available as a reentry tool for vascular dissections are in use. The disclosed device will be similar but specifically designed as an ICE device anchored in the hepatic vein for direct visualized portal venous access. 
     In conclusion, the disclosed system allows a simpler method of performing a TIPS procedure by anchoring a guide device and/or rail that guides and positions a needle and/or an outer sheath. 
     Since many modifications, variations, and changes in detail can be made to the described preferred embodiments of the invention, it is intended that all matters in the foregoing description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents.