Patent Publication Number: US-2018042451-A1

Title: Single piece bending neck for an articulating ultrasound probe

Description:
This invention relates to ultrasonic imaging probes and, in particular, to bending necks for articulating ultrasound probes. 
     Some ultrasound probes are designed for imaging from within the body, including catheter probes and transesophageal echocardiography (TEE) probes. In these probes the imaging transducer is located at the tip of the probe, which is generally designed to be articulated by the operator so as to obtain the desired view. The preferred way to articulate the probe tip, particularly in the case of TEE probes, is by means of a distal section of the catheter or gastroscope referred to as a bending neck. The bending neck is formed by a series of links which are pivotally connected to each other. This enables each link to move slightly with respect to its adjoining links and hence the entire section of links can be made to controllably articulate over a substantial angle of bending. Control of the articulation is done by cables extending through the probe and the bending neck which are wrapped about the shaft or pulley of a control knob or motor in the control unit at the proximal end of the probe. As the operator turns a knob or actuates a motor, a desired cable is pulled, which bends the articulating neck section of the probe. Generally the pivot axis between links alternates by 90° from link to link so that some axes can bend in the 0°-180° directions while the others can bend in the 90°-270° directions. The use of two controls and control cables for these two axis directions enables the operator to articulate the bending neck in any of these directions or any direction in between. The links and hence the bending neck is hollow, enabling the wiring for the transducer at the distal tip as well as other items such as guide wires and surgical tools to pass through the probe for operation at or through the tip of the probe. 
     The fabrication and assembly of a bending neck for an articulating probe can be painstaking and costly. Each link of the neck must be individually formed, then the links are joined by pins or rivets so that they will pivot with respect to each other. It is desirable to have an easier and less costly way to build a bending neck, yet still have the wide range of articulation and articulation control which users demand. 
     In accordance with the principles of the present invention, a bending neck for a controllably articulating ultrasound probe is provided which is formed from a single tube or nested tube set. The tube is etched or machined to form individual, pivoting links. A groove formed in one of the tubes of the nested tube set, or indentations in a single tube provide the control cable passageway. The bending neck curvature is formed to be variable, as by the use of movable bending points, multiple control cable anchor points, varying pivot axis spacing, and multi-durometer neck sheaths. 
    
    
     
       In the drawings: 
         FIGS. 1 and 1A  illustrate a section of a bending neck formed from a single nested set of two tubes. 
         FIGS. 2 and 2A  illustrate a section of a bending neck formed from a single tube, including an integral control cable passageway. 
         FIG. 3  illustrates a bending neck of the present invention with a variable bending deflection point. 
         FIG. 4  illustrates a bending neck with varied link spacing to provide variable articulation. 
         FIG. 5  is a detailed view of a technique for determining the link-to-link articulation angle for a bending neck of the present invention. 
         FIG. 6  illustrates a variable durometer sheath which provides variable bending for a bending neck of the present invention. 
         FIGS. 7 and 8  illustrate the use of multiple control cable anchor points to controllably vary the bending of a bending neck of the present invention. 
         FIG. 9  illustrates a bending neck which can be controllably bent in two different planes through the use of differently anchored control cables. 
         FIGS. 10 a  and 10 b    illustrate a variably articulating bending neck which is controllable articulated by two bending sections in one plane. 
         FIGS. 11 a  and 11 b    illustrate a variably articulating bending neck which is controllable articulated by two bending sections in two planes. 
     
    
    
     Referring first to  FIG. 1 , a single piece bending neck  10  for an articulating ultrasound probe is shown which is formed of two concentric tubes, generally made of a metal such as stainless steel. The inner tube  10   b  fits tightly within the outer tube  10   a . Before insertion, two longitudinal grooves  12  are formed on opposite sides along the length of the outside of tube  10   b . These grooves form passageways for control cables that control the articulation of the bending neck as described below. The grooves  12  are clearly shown in the cross-sectional view of  FIG. 1A . With the two tubes concentrically positioned, they are then cut into separate links  11  by laser cutting toward the longitudinal axis of the tube or by another machining technique. The links are formed so as to remain movably connected to each other, as by lobes  14  extending from one link to the next and located on opposite sides of the links. These lobes and the spacing between the links formed by the machining process enable the adjacent links to move and pivot with respect to each other about axes extending through opposing lobes on opposite sides of the links. While each link may only pivot a small angle with respect to its neighbor, a number of successive links forming a bending neck may together bend in a considerable curve. This is the desired articulation, significant enough to be able to position the distal end of the probe where needed, but not sharp enough at any articular point so as to bind the wires, tools, and other items passing through the central lumen of the bending neck. 
       FIG. 2  illustrates a second implementation of a single piece bending neck, this time using just a single tube  10 . The tube  10  is machined into separate connected links as described above, the grooves  15  between separate links being shown in this drawing. Since the inner tube used for the control cable groove is not present in this single tube implementation, a series of ring-like indentations  16  are formed on opposite sides of the tube to convey the control cables through the bending neck. Two parallel cuts are made through the tube wall, then the area between the cuts is pressed inward, forming the indentations as clearly shown in the cross-sectional view of  FIG. 2A . The indentations are formed on the tube sides which are 90° around the tube from the lines of pivot lobes  14 , which are on the top and bottom and cannot be seen in the view of  FIG. 2 . As the control cables passing though the indentations on opposite sides of the tube are pulled after being anchored at the distal end of the bending neck. They will respectively cause the neck to bend into and out of the plane of the drawing of  FIG. 2 . 
     There are a number of ways that the bending of a bending neck of the present invention can be controlled and adjusted. One control technique is to control the deflection point from which the bending takes place.  FIG. 3  illustrates a technique in which a rigid member  18  is located in the bending neck with its distal end at the desired deflection point. In this case the rigid member is a tube  18  and this partially cut-away view shows links to the left of the tube  18  which are free to pivot about their pivot lobes, while the links through which the tube is located are immobilized from pivoting. The position of the deflection point is adjustable by adjusting the extension of the rigid member  18  into and out of the bending neck. 
     The angle subtended by the curvature of a section of the bending neck can be set by selectively determining the lengths of individual links as illustrated by the bending neck  10  of  FIG. 4 . In this implementation the links to the left with pivot lobes  14  are relatively short and the length of these links can bend with a relatively shorter radius of curvature. The larger links to the right with the pivot lobes  24  will bend maximally with a relatively larger radius of curvature. In addition, the different size links have different moments, which determine which set of links will bend first when commonly controlled. The smaller links with the pivot lobes  14 , having smaller moments, will bend first. This is useful, for instance, when the placement of a transducer at the distal tip of the smaller links (left side of the drawing) is being controlled. The articulation of both sections of the bending neck is set to approximately the desired position by pulling relatively forcefully on the control cables in the grooves  12  and thereby causing both sections to bend. With the transducer near its desired position, light pulling of the cables is used to move only the distal section of smaller links to finely adjust the final desired position of the transducer. 
     The degree of pivoting between adjacent links is a function of the groove that is machined through the tube to form separate links.  FIG. 5  is a partial side view of a portion of a bending neck where separate links  11  have been formed by machining groove  15  through the tube. The two links can pivot around pivot lobe  14  by the width of the groove  15 , opening and closing the groove 90° on either side of the axis of the pivot lobes. If greater pivoting is desired the groove can be machined with a tapered width with a maximum opening of theta above and below the pivot lobes. The relative pivoting of the adjacent links is thereby increased to the dimension of angle theta. 
     Another technique for providing variable bending of a bending neck is to enclose the bending neck in a sheath with a variable durometer.  FIG. 6  illustrates a sheath  20  over a bending neck with a variable durometer from the distal end to the left to the proximal end of the bending neck. The sheath is relatively stiffer (higher durometer) to the right, which becomes less stiff toward the distal end of the sheath. When the control cables are actuated to bend the bending neck, the distal end will bend first and more easily than the higher durometer proximal section of the bending neck. The durometer can be set by the choice of materials used along the length of the sheath. Another way to achieve the same result is to vary the thickness of the sheath material along the length of the sheath. The dashed lines  22  in  FIG. 6  indicate that the sheath  20  is thicker toward its proximal (right) end than it is toward and at the distal end. Yet another way to achieve the same result is through the way in which the sheath is affixed to the bending neck. In the example of  FIG. 6  the sheath  20  is tacked to the bending neck at closely spaced points  26  along the proximal portion of the bending neck, and is tacked to the bending neck at more widely spaced points  28  along the distal portion of the bending neck. This will cause the distal portion of the bending neck to bend more easily and readily than the proximal portion. 
     In some implementations it may be desirable to controllably bend a section of a bending neck at some times, and lock it in an unbent configuration at others.  FIG. 7  illustrates an implementation of this feature using the embodiment of  FIG. 4 . In this case there are two sets of control cables,  40 - 42 ′ and  42 - 42 ′, extending through the control cable passageways  12 . The ends of cables  40 - 40 ′ are anchored by attachment to the distal link (leftmost) of the bending neck  10  as shown by anchor points  32  and  34  in  FIG. 8 . In  FIG. 8  the inner tube  10   b  has been removed for clarity of illustration. The ends of the other set  42 - 42 ′ of cables are anchored to link  11 ′, the first link following those with pivot lobes  24 , as shown by anchor points  36  and  38 . When each pair of cables is pulled and relaxed in complementary fashion, the corresponding section of the bending neck is bent in the plane of the drawing, cable set  40 - 40 ′ controlling the distal (small link) section and cable set  42 - 42 ′ controlling the proximal (larger link) section. But when both of cables  42 - 42 ′ are pulled in unison, the links of the proximal section are pulled together and locked into a straight configuration as shown in  FIG. 7 . The distal section of the bending neck can still be controllably articulated by use of cables  40 - 40 ′. When cables  40  and  40 ′ are pulled in unison, the entire bending neck is locked in a straight configuration. Thus, by using multiple control cables and selected anchor points, different sections of a bending neck can be locked or articulated. 
     In the implementation of  FIG. 7  the pivot lobes are all on the front and back of the bending neck, which allows both articulating sections to be curved in the same plane, the plane of the drawing. A single set of control cable passageways  12  accommodates both sets of cables for this articulation.  FIG. 9  illustrates an implementation in which pivot lobes  14  are formed in the front and back sides of the tube and hence their pivot axes are all normal to the plane of the drawing. The pivot lobes  24  of the proximal section of the bending neck, however, are formed on the top and bottom of the tube and have their pivot axes parallel to the plane of the drawing. This means that the distal section with pivot lobes  14  can be curved in the plane of the drawing whereas the proximal section of links can be curved orthogonally into and out of the drawing plane. To control these different actions different sets of control cables are used. Cables  42  and  42 ′ extend through cable passageways  12  and are anchored at the ends at anchor points  32  and  34 . These cables control the articulation of the distal (leftmost) section of the bending neck. The control cables  40  and  40 ′ for the proximal section of the bending neck are oriented 90° around the circumference of the tube from cables  42  and  42 ′. These control cables must pass through their own, differently positioned control cable passageways oriented 90° relative to passageways  12 . These control cables  40  and  40 ′ are anchored at the distal end of the section of links they control as shown by cable  40  anchored at anchor point  36  in the cutaway view of  FIG. 9 . (Cable  40 ′ and its anchor point are cut away in this view.) When cables  42 - 42 ′ are pulled the distal section of links is articulated or locked, and when cables  40 - 40 ′ are pulled the proximal section of links is controlled. 
       FIGS. 10 a -10 b    are perspective views of an articulating ultrasound probe of the present invention. This probe has two straight, non-articulating sections  60  and  62  and two articulating sections  70  and  72 . Like the implementation of  FIG. 7 , the articulating sections  70  and  72  articulate in the same plane, the horizontal plane H of the drawings. In  FIG. 10 a    the short articulating section  70  is curved by control of its cables anchored at the distal end of section  70 . In  FIG. 10 b    the cable set anchored at the distal end of section  72  has been used to articulate section  72 . Since all articulation is in the same plane, the pivot lobes of both sections are on the same sides of the section, and only a single pair of cable passageways is necessary for the control cables of both sections. 
       FIGS. 11 a -11 b    are perspective views of another articulating ultrasound probe of the present invention, this one implementing articulation in two planes as in the case of  FIG. 9 . Like  FIG. 9 , the articulating section  72  of  FIG. 11 a    has its pivot lobes, pivot axes, and control cable passageways oriented 90° around the circumference of the tube as compared with those of articulating section  70 . As  FIGS. 11 a  and 11 b    illustrate, the distal section  72  can be controllably articulated up and down in the vertical (V) direction. 
     Other variations of the above concepts will readily occur to those skilled in the art. The pivot lobes may be formed in other shapes and sizes, and pivoting between links can be provided by other, more complicated pin or rivet configurations. However, the implementations illustrated herein have the advantage of being wholly formed from a single or concentric pair of tubes. Instead of sections of identically oriented links, an articulating section can be interspersed with links pivoting at 90° with respect to each other, giving an articulating section the ability to be curved in almost any direction.