WO2009097650A1

WO2009097650A1 - Expandable catheter

Info

Publication number: WO2009097650A1
Application number: PCT/AU2009/000128
Authority: WO
Inventors: Kurt Liffman; Ilija Denis Sutalo; Stuart Bateman; Qiang Yuan
Original assignee: Commonwealth Scientific And Industrial Research Organisation
Priority date: 2008-02-07
Filing date: 2009-02-05
Publication date: 2009-08-13

Abstract

The present invention provides an expandable catheter for percutaneous delivery of material. The catheter includes an elongated tube, having an internal passageway extending between proximal and distal ends of the tube, which is configured for radial expansion to enlarge a diameter of at least a portion of the internal passageway. The radial expansion of the elongated tube is responsive to a characteristic of a material being delivered percutaneously through the internal passageway of the elongated tube. For example, the elongated tube may be responsive to a characteristic of the material, such as a pressure of the fluid or some chemical or other agent in the fluid, so as to result in radial expansion of the elongated tube. Radial expansion of the elongated tube can provide for enlargement of a diameter of at least a portion of the internal passageway so as to enable percutaneous delivery of material, such as a contrast agent, at greater flow rates than fixed diameter catheters can safely achieve.

Description

EXPANDABLE CATHETER

FIELD

[01] The present invention relates to catheters for delivering fluids percutaneously to a patient. In particular, the present invention relates to a catheter that can be expanded after insertion to enable higher fluid flow rates in use.

BACKGROUND

[02] Catheters are frequently used for the percutaneous delivery of fluid to the interior of patient blood vessels for various purposes including for delivery of medicaments, radiopaque dye and implantable devices. Radiopaque dyes, also known as contrast agents, are used in diagnostic radiology to facilitate diagnosing conditions of blood vessels and other tissue structures.

[03] A catheter is a tube that can be inserted percutaneously into a blood vessel of a patient to allow delivery of fluids, such as radiopaque dyes from a source outside the patient to the interior of the blood vessel for subsequent distribution within the vascular system of the patient. Such radiopaque fluids or dyes are typically used for imaging a region of the blood vessel or some other body structure or tissue with an x-ray imaging device wherein the blood vessel or body structure or tissue does not normally contrast with its background to be clearly seen by x-ray imaging devices.

[04] Computed tomography (CT) scanning is a commonly used diagnostic tool that provides views of internal body structures. During a CT scan, multiple x-rays are passed through the body producing cross-sectional images, or "slices". Contrast agents are often used in CT scanning procedures to illuminate certain details of anatomy more clearly.

[05] Multislice CT scanners incorporate multiple x-ray detectors, as opposed to single detectors, which allows greater volumes to be imaged with higher resolution and in much less time than with earlier CT scanning devices. A major benefit of the increased speed of volume coverage associated with multi-slice CT scanners is that they allow large volumes to be scanned at the optimal time following intravenous contrast agent administration. This has particularly benefited CT angiography techniques which rely heavily on precise timing to ensure good demonstration of arteries.

[06] As a consequence of the greater volume coverages of multi-slice CT scanners, it is necessary to inject larger amounts of contrast medium intravenously at higher flow rates. In fact, contrast fluid injection rates of 3 to 4 millilitres per second are common for some vascular studies. Furthermore, the increasing use of multi-slice CT scanners is now envisaging injection flow rates approaching 7 to 8 millilitres per second.

[07] To facilitate intravenous delivery of contrast media, a catheter is inserted percutaneously into the interior of a patient blood vessel. The catheter has a distal end inserted into the interior of the blood vessel and a proximal end which is connected to a manual or computer controlled electronic or mechanical syringe for injecting the contrast media into the blood vessel at the required flow rate.

[08] One reason that existing catheters are favoured for percutaneously delivering contrast fluid at high flow rates is that their relatively small diameter makes them relatively easy to insert through the patient's skin and blood vessel wall. Using a larger diameter catheter requires use of a larger needle to gain percutaneous access to the blood vessel. This would involve significantly more pain and discomfort for the patient as a larger diameter hole is created through the patient's skin and blood vessel wall to accommodate the larger diameter catheter.

[09] In fact, because of the significance of the problems associated with using larger diameter catheters medical practitioners have preferred to use 1 mm diameter catheters to inject contrast media at fluid flow rates that are beyond the design limits of these existing catheters.

[10] Existing catheters that are used for percutaneously delivering contrast fluid to the interior of patient blood vessels have a diameter of 1 mm and are only designed to achieve flow rates of approximately 1 millilitre per second. Accordingly, when injecting contrast fluids into patient blood vessels at upwards of 1 millilitre per second there is a risk that existing catheters may fail resulting in breakage of the catheter inside the patient blood vessel. As a result, it is possible that small pieces of plastic may lodge in the heart, lungs or brain. Also, a greater than 1 millilitre per second flow of contrast fluid from a catheter having a diameter of 1 mm will involve the fluid travelling at a high speed and this may damage the blood vessel in which the catheter resides. Any subsequent leakage of potentially toxic fluids into the surrounding tissues as a result of damage to the blood vessel may produce wounds that take a long time to heal. Thus, there is a need for a catheter for percutaneously delivering contrast fluid to the interior of a patient blood vessel at the higher flow rates required by modern CT scanning devices.

[1 1 ] Accordingly, there is a need for a catheter for percutaneously delivering fluid to the interior of a patient blood vessel that is relatively easy to insert percutaneously into the patient blood vessel, which does not involve significantly more pain, discomfort or adverse complications than existing catheters, yet which is capable of achieving higher fluid flow rates or at least higher fluid flow rates than the fluid flow rates that existing catheters are designed to achieve.

[12] A reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission that that document or matter was known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims.

SUMMARY OF THE INVENTION

[13] Accordingly, in one aspect, the present invention provides a catheter for percutaneous delivery of material, the catheter including: an elongated tube having an internal passageway extending between proximal and distal ends of the tube; the elongated tube being configured for radial expansion to enlarge a diameter of at least a portion of the internal passageway; wherein the radial expansion of the elongated tube is responsive to a characteristic of a material being delivered percutaneously through the internal passageway of the elongated tube. [14] The present invention is advantageous in that it provides a catheter for percutaneously delivering material through an internal passageway of an elongated tube with a distal end that can be inserted through the skin into the interior of a patient blood vessel or other internal passage or space. This minimises patient discomfort levels and adverse side effects so that they are comparable with existing fixed diameter catheters used for similar purposes. Meanwhile, the catheter also provides for radial expansion of the elongated tube which in turn provides for enlargement of a diameter of at least a portion of the internal passageway for when percutaneously delivering a material through the internal passageway that enables delivery at greater fluid flow rates than the fluid flow rates that fixed diameter catheters can safely achieve.

[15] The present invention is also advantageous because the diameter of the elongated tube is responsive to a characteristic of a material being delivered percutaneously through the internal passageway of the elongated tube such as a pressure of the fluid being or some chemical or other agent in the fluid without requiring further instrumentation (eg. insertion of an elongated member into the interior of the elongated tube) to expand the diameter of the internal passageway. The elongated tube itself expands radially in response to a characteristic of the material being delivered through the internal passageway, such as a pressure applied by the material against the internal passageway resulting from a rate of flow of the material through the internal passageway. For example, where the material is a contrast agent, the elongated tube itself expands radially in response to a pressure applied by the contrast agent against the internal passageway at a rate of flow of the contrast agent through the internal passageway required by the medical practitioner for the procedure being conducted. Accordingly, the diameter of at least a portion of the internal passageway will only expand as much as is required for the fluid flow rates utilised during the procedure and might remain expanded for only an amount of time required for the amount of fluid to be delivered at the required fluid flow rate. This can be particularly advantageous in reducing the discomfort to the patient as well as reducing the amount of tissue damage which can be associated with inserting larger fixed diameter catheters percutaneously into the interior of blood vessels to deliver contract agents or other material at high flow rates.

[16] In one form, the material being delivered through the internal passageway includes a fluid and the characteristic of the material is a pressure of the fluid.

[17] In another form, the radial expansion of the elongated tube is responsive to a threshold of the pressure of the fluid.

[18] In yet another form, the elongated tube is formed from an expandable material. This form of the invention is advantageous in that the material properties of the material forming the elongated tube facilitate radial expansion to enlarge a diameter of at least a portion of the internal passageway. Accordingly, the material properties of the elongated tube may facilitate radial expansion in response to a pressure of the flow of material, such as contrast agent, through the internal passageway of the tube. Such an arrangement can be relatively simple to manufacture such as by extrusion or moulding and may enable utilisation of existing manufacturing apparatus and equipment.

[19] In another form, the elongated tube is formed from a resiliently expandable material so that the elongated tube can radially expand in response to the characteristic of the material being delivered through the internal passageway and radially contract in response to a change in the characteristic of the material being delivered through the internal passageway. This form of the invention is advantageous in that the tube can radially expand in response to a characteristic of the material being delivered through the internal passageway, such as a pressure of the material, and contract in response to a change in the characteristic, such as a reduction in the pressure of the material. Where the material is a contrast agent, the tube can radially expand when the flow rate and pressure of the contrast agent increases and radially contract when the flow rate and pressure decreases, to a size that is more comfortable for the patient and easier to insert and remove through the patient's skin. [20] In one form, the material being delivered through the internal passageway includes a fluid and the characteristic of the material is a pressure of the fluid and the change in the characteristic of the material is a reduction in the pressure of the fluid

[21] In one form, the elongated tube has a sectional profile that is shaped to facilitate the radial expansion of the elongated tube. This form of the invention is advantageous in that the elongated tube may be shaped in a variety of ways to facilitate the radial expansion of the elongated tube, and, in turn, the diameter of the portion of the internal passageway, and need not completely rely on expandable or contractable properties of materials forming the elongated tube.

[22] In one form, the wall has a star-shaped sectional profile to facilitate the radial expansion of the elongated tube.

[23] In another form, the elongated tube has a wall including one or more folds that open to facilitate the radial expansion of the elongated tube.

[24] In one form, the wall has an external surface and a layer of flexible material is deposited on the external surface. An advantage of this form of the invention is that an external surface of the elongated tube, which may include an irregular surface, may be at least partially smoothed by filling in dips or troughs in the external surface with the layer of flexible material. This form of the invention is advantageous when the distal end of the elongated tube is inserted percutaneously into, say, the interior of a patient blood vessel because the flexible material presents a smoother surface against tissue surrounding the elongated tube. If the external surface presented against the surrounding tissue is irregular and not smoothed by the flexible material then material such as contrast agent or internal bodily fluids, such as blood, may seep out between the external surface of the elongated tube and the surrounding tissue.

[25] In one form, the elongated tube has a wall including one or more radially inwardly extending folds that each form a trough in an external surface of the wall and a layer of flexible material deposited on the external surface in each trough.

[26] In one form, the elongated tube has a wall that is twisted about a longitudinal axis of the elongated tube and the radial expansion of the elongated tube occurs by untwisting the elongated tube.

[27] In another aspect, the invention provides a device for delivery of material, the device including: an elongated tube having an internal passageway extending between proximal and distal ends of the tube; the elongated tube being configured for radial expansion to enlarge a diameter of at least a portion of the internal passageway; wherein the radial expansion of the elongated tube is responsive to a characteristic of a material being delivered through the internal passageway of the elongated tube.

[28] Other forms of the invention may also be used to deliver and retrieve stents or other surgical or implantable medical devices within the body.

BRIEF DESCRIPTION OF THE DRAWINGS

[29] The present invention will now be described with reference to the accompanying Figures illustrating preferred embodiments of the present invention, wherein:

Figure 1 is an illustration of an embodiment of a catheter of the present invention, the catheter including an elongated tube into which is being inserted a needle.

Figure 2 is an illustration of the needle fully inserted into the catheter of Figure 1 for insertion of the needle and catheter percutaneously into the interior of a patient blood vessel.

Figure 3 is a side view of a cross-section of the needle and catheter of

Figure 1 with the needle inserted into the elongated tube of the catheter.

Figure 4 is a perspective view of the catheter of Figure 1. Figure 5 is cross-sectional view of the catheter of Figure 1 in which the elongated tube is radially contracted.

Figure 6 is an illustration of a cross-sectional view of the catheter of Figure 1 wherein the elongated tube is radially expanded.

Figure 7 is an illustration of a perspective view of another embodiment of the catheter of the present invention in which the elongated tube is radially contracted in which a wall of the elongated tube includes a plurality of folds.

Figure 8 is a sectional view of the elongated tube of the catheter of Figure 7 in which the elongated tube is radially contracted and the wall of the elongated tube has a star-shaped sectional profile.

Figure 9 is a sectional view of the elongated tube of the catheter of Figure 7 wherein the elongated tube is in radially expanded.

Figure 10 is a sectional view of the elongated tube of another embodiment of the catheter of Figure 7 in which the elongated tube includes a layer of flexible material deposited on an external surface of the wall of the elongated tube.

Figure 1 1 is a sectional view of the elongated tube of the embodiment of the catheter illustrated in Figure 10 wherein the elongated tube is radially expanded.

Figure 12 is an illustration of a perspective view of the catheter of

Figures 10 and 1 1 wherein the layer of flexible material deposited on the external surface of the wall of the elongated tube forms a tapering portion at the distal end of the elongated tube.

Figure 13 illustrates a contrast agent injection system incorporating a catheter in accordance with the invention inserted percutaneously into a patient laying on a surface while a CT scanner scans the body of the patient.

Figure 14 illustrates a contrast agent injection system incorporating a catheter in accordance with the invention inserted through a blood vessel wall and delivering contrast agent to a site within the blood vessel. DETAILED DESCRIPTION

Referring to Figures 1 to 12, there is shown a catheter 10 including an elongated tube 20 having a proximal end 25 and a distal end 27 and an internal passageway 22 within the elongated tube 20 extending between the proximal end 25 and the distal end 27. In use, the distal end 27 of the elongated tube 20 is inserted into a blood vessel 30 as illustrated in Figure 14 so that a material 40 may be delivered via the internal passageway 22 to a site within the blood vessel 30. The material 40 may be a medicament, a contrast agent, or some other fluid or may include an implant or some other form of medical device. As shown in Figures 12 and 13, in use the catheter 10 may be inserted percutaneously into a blood vessel 30 within a body 95 of a patient laying on a surface 94 while a CT scanner including an x-ray emitter 96 and one or more detectors 97 scan the body 95 of the patient. Alternatively, the catheter 10 may be used for delivery of the material 40 into other internal bodily passages, tissues and organs other than blood vessels. However, for the sake of convenience, the catheter 10 is described herein in the context of its use for the purpose of delivering that material 40 into the blood vessel 30.

[30] In the catheter 10 illustrated in each of the Figures, the elongated tube 20 has a longitudinal axis X extending between the proximal end 25 and the distal end 27 of the elongated tube 20. The elongated tube 20 is formed from a wall 62 which has an internal wall surface 60 which defines the internal passageway 22. The wall 62 radially surrounds the longitudinal axis X of the elongated tube 20 and the internal wall surface 60 faces towards the longitudinal axis X. At least part of the wall 62 forming the elongated tube 20 is configured for radial expansion. When at least part of the wall 62 radially expands at least part of the internal wall surface 60 also radially expands. The radial expansion of at least part of the internal wall surface 60 which defines the internal passageway 22 results in enlargement of the diameter at least part of the internal passageway 22. Thus, at least part of the wall 62 forming the elongated tube 20 is configured for radial expansion so as to enlarge a diameter of at least part of the internal passageway 22. In the catheter 10 illustrated in each of the Figures, the radial expansion of the elongated tube 20 is responsive to a characteristic of the material 40 being delivered percutaneously through the internal passageway 22 of the elongated tube 20. Where the material 40 is a fluid 40, such as a contrast agent, then the characteristic of the material 40 may include the pressure of the fluid. Alternatively, the characteristic of the material 40 may include an agent in the material 40 that reacts with material forming part or the entire wall 62 of the elongated tube 20 to elicit the radial expansion of the elongated tube 20. For the sake of convenience, the catheter 10 is described herein in the context of its use for the purpose of delivering material 40 in the form of a fluid contrast agent. However, it is to be appreciated that the catheter may have broader application in relation to the delivery of other materials.

[31] In order to insert the distal end 27 into the interior of the blood vessel 30 a needle 50 is insertable into the internal passageway 22 within the elongated tube 20. The needle 50 is an elongated shaft 51 having a proximal end 55 and a distal end 57 wherein the distal end 57 has a sharpened tip 58. As is shown in Figure 1 , the distal end 57 of the needle 50 is first inserted into the internal passageway 22 of the elongated tube 20 at the proximal end 25 and is progressively slid within the internal passageway 22 until the distal end 57 of the needle 50 reaches the distal end 27 of the internal passageway 22 of the elongated tube 20 and exits through an opening 28 at the distal end 27 of the elongated tube 20. Thus, the sharpened tip 58 at the distal end 57 of the needle 50 protrudes out of the opening 28 at the distal end 27 of the elongated tube 20. Furthermore, the proximal end 25 of the elongated tube 20 moves towards and surrounds the proximal end 55 of the needle 50.

[32] Figure 3 illustrates in more detail the needle 50 inserted within the internal passageway 22 of the elongated tube 20. The needle 50 is mounted to a base portion 52 which may be formed out of a plastic, metal or any other suitable material. The proximal end 55 of the needle 50 extends longitudinally through the base portion 52. The needle 50 may be solid or it may have a hollow passageway there-through and may be formed out of any suitable material including surgical stainless steel or any other suitable biocompatible material. The purpose of the needle 50 is such that when it is required to locate the distal end 27 of the elongated tube 20 within the blood vessel 30, as shown in Figure 14, the sharpened tip 58 of the needle 50 punches a hole through the skin of the patient and subsequently punctures a hole through the blood vessel wall 32. The elongated tube 20 is formed out of material that is sufficiently hard or resilient that the distal end 27 of the elongated tube 20 follows the sharpened tip 58 of the needle through the holes in the skin and blood vessel wall 32 punctured by the sharpened tip 58 of the needle 50. Thus the distal end 27 is thereby located in the interior of the patient blood vessel 30 while the proximal end 25 of the elongated tube 20 remains outside at least the interior of the patient blood vessel and outside the skin of the patient as well.

[33] Although, as described above, the catheter 10 of the invention may in use be positioned such that the distal end 27 is located in the interior of the patient blood vessel 30 and the proximal end 25 outside the blood vessel 30 and outside the skin of the patient, the catheter 10 could also be used in such a way that the proximal end 25 is located on the interior of the patient's skin. For example, in a procedure where an incision has been made in the patient's skin the proximal end 25 of the catheter 10, or indeed the entire catheter 10, may be located on the inside of the patient's skin via the incision.

[34] The proximal end 25 of the elongated tube 20 is mounted to a base member 15. The base member 15 may take any suitable form or configuration.

In the embodiment illustrated in Figure 3, the base member 15 has a proximal end 16 formed in a frustoconical shape with a hollow interior volume 9 for receiving a distal portion 53 of the base portion 52 of the needle 50. Although the proximal end 16 has a frustoconical shape in the embodiment illustrated in Figure 3 it is to be appreciated that the shape could be any suitable shape including elliptical, cylindrical, cuboid or a rectangular, hexagonal or octagonal prism shape to name but a few.

[35] The proximal end 16 of the base member 15 has an inner surface 17 defining the hollow interior volume 9 and an outer surface 18. The outer surface 18 of the proximal end 16 also has a frustoconical shape in the embodiment illustrated in Figure 3, however, it is to be appreciated that the shape could be any suitable shape including elliptical, cylindrical, cuboid or a rectangular, hexagonal or octagonal prism shape. The outer surface 18 has a proximal terminal end 19 and the outer surface 18 is inclined in the direction towards the proximal terminal end 19. The outer surface 18 extends distally from the proximal terminal end 19 to a point where the outer surface 18 meets an external surface 21 of an intermediate portion 14 of the base member 15. The external surface 21 of the intermediate portion 14 may have any suitable shape or configuration. For example, the external surface 21 of the intermediate portion 14 may, as illustrated in the Figures, have a cylindrical shape or it may elliptical or it may be faceted so that, for example, the external surface 21 has a cuboid, rectangular, octagonal or hexagonal prism shape to name but a few.

[36] The inner surface 17 of the proximal end 16 of the base member 15 also has a frustoconical shape in the embodiment illustrated in Figure 3, however, it is to be appreciated that the shape could be any suitable shape including elliptical, cylindrical, cuboid or a rectangular, hexagonal or octagonal prism shape. The inner surface 17 connects to the outer surface 18 at the proximal terminal end 19 and the inner surface 17 is inclined in the direction towards the proximal terminal end 19. The inner surface 17 extends distally from the proximal terminal end 19 to a point where the inner surface 17 meets an internal surface 24 of the intermediate portion 14 of the base member 15. The internal surface 24 of the intermediate portion 14 has a frustoconical shape in the embodiment illustrated in Figure 3, however, it is to be appreciated that the shape could be any suitable shape including elliptical, cylindrical, cuboid or a rectangular, hexagonal or octagonal prism or star shape.

[37] The internal surface 24 defines an internal hollow space 13 within the intermediate portion 14 of the base member 15. The hollow space 13 within the intermediate portion 14 of the base member 15 is capable of receiving the distal end 53 of the base portion 52 of the needle 50 therein. The hollow space 13 extends distally from the inner surface 17 of the proximal end 16 to a hollow passageway 12 through the intermediate portion 14 of the base member 15. The hollow passageway 12 through the intermediate portion 14 of the base member 15 is capable of receiving the proximal end 55 of the shaft 51 of the needle 50 there-through when the shaft 51 of the needle 50 is fully inserted into the internal passageway 22. The intermediate portion 14 extends from the proximal end 16 to a distal end 1 1 of the base member 15. The distal end 11 of the base member 15 connects to the proximal end 25 of the elongated tube 20.

[38] The hollow space 13 within the intermediate portion 14 of the base member 15 is shaped and formed out of a material capable of receiving the distal portion 53 of the base portion 52 of the needle 50 in a manner that retains the distal portion 53 within the hollow space 13. For example, the hollow space 13 may be shaped to receive the distal portion 53 in a friction or interference fit. In this case, either the material forming the distal portion 53 or the intermediate portion 14 or both may be a flexible or resilient material such as a resilient elastomer.

[39] In Figures 4 to 6, an embodiment of the catheter 10 is illustrated wherein the elongated tube 20 is formed out of a material having properties whereby the internal diameter of the internal passageway 22 within the elongated tube 20 is capable of, as illustrated in Figure 5, being relatively smaller and, as illustrated in Figure 6, is capable of being enlarged. It is to be appreciated that where reference is made to the smaller and enlarged diameter states of the internal passageway 22 of the elongated tube 20 this may equate with, respectively, a relatively smaller mean cross-sectional diameter and relatively larger mean cross-sectional diameter of part or the entire internal passageway 22. The small and enlarged diameter state of the internal passageway 22 of the elongated tube 20 may also equate with, respectively, a smaller cross-sectional area and relatively larger cross sectional area of the internal passageway 22.

[40] The internal passageway 22 is defined by the internal wall surface 60 of the wall 62 forming the elongated tube 20. The internal wall surface 60 of the elongated tube 20 extends from the hollow passageway 12 of the intermediate portion 14 at the distal end 1 1 of the base member 15. The internal wall surface 60 of the elongated tube 20 extends distally from the hollow passageway 12 to the distal end 27 of the elongated tube 20. The internal wall surface 60, in the embodiments illustrated in Figures 4 to 6, has a generally cylindrical shape and a substantially circular cross-section throughout. However, the internal wall surface 60 may have an oval or otherwise curved cross-section. The internal wall surface 60 may also have a faceted cross- section such as, for example, a square, hexagonal, octagonal cross section to name but a few examples of faceted cross-sections.

[41] The wall 62 forming the elongated tube 20 also has an external wall surface 64 opposite the internal wall surface 60. The external wall surface 64 extends distally from the external surface 21 of the intermediate portion 14 at the distal end 1 1 of the base member 15. The external wall surface 64 extends distally from the external surface 21 of the intermediate portion 14 to the distal end 27 of the elongated tube 20. The external wall surface 64 and the internal wall surface 60 are connected by a planar surface 29 surrounding the opening 28 at the distal end 27 of the elongated tube 20.

[42] In the embodiments illustrated in Figures 3 and 4 the external wall surface 64 and the internal wall surface 60 are connected by a planar surface 29 surrounding the opening 28 at the distal end 27 of the elongated tube 20. The planar surface 29 is annular and lies in a plane that is substantially perpendicular to the longitudinal axis X of the elongated tube 20. At the distal end 27 of the elongated tube 20 the thickness of the wall 62 is substantially reduced compared to the thickness of the wall 62 at the proximal end 25. Thus, the thickness of the wall 62 tapers at the distal end 27 of the elongated tube 20 thereby forming a tapered portion 31 of the elongated tube 20. The annular planar surface 29 has an inner edge and an outer edge. The diameter of the inner edge is substantially the same as the diameter of the internal wall surface 60 of the proximal end 25 of the elongated tube 20. In contrast, the outer edge of the annular planar surface 29 has a diameter that is less than the diameter of the external wall surface 64 at the proximal end 25 of the elongated tube 20. Thus, as can be seen in Figures 3 and 4, in the tapered portion 31 the thickness of the wall 62 tapers inwardly towards the longitudinal axis X of the elongated tube 20. Accordingly, the tapered portion 31 facilitates ease of insertion of the distal end 27 of the elongated tube 20 through the holes in the skin and blood vessel wall 32 punctured by the sharpened tip 58 of the needle 50.

[43] When, as shown in Figure 14, the fluid 40 is passed through the internal passageway 22 of the catheter 10 from the proximal end 25 to the distal end 27 and out the opening 28 for delivery to the interior of the blood vessel 30, molecules of the fluid 40 exert pressure on the internal wall surface 60 defining the internal passageway 22. At least part of the wall 62 forming the elongated tube 20 is configured for radial expansion in response to pressure exerted on the internal wall surface 60 defining the internal passageway 22. The wall 62 forming the elongated tube 20 may also be configured for radial expansion in response to a threshold level of the pressure of the fluid 40 within the internal passageway 22. For a given rate of flow of the fluid 40 through the internal passageway 22 a respective magnitude of fluid pressure is applied against the internal wall surface 60 in an outward direction which may be a substantially radially outward direction from the longitudinal axis X.

[44] As illustrated in Figure 5, when there is no fluid 40 flowing or where there is a relatively low rate of flow of the fluid 40 through the internal passageway 22 at least part of the wall 62 forming the elongated tube 20 is not radial expanded. Alternatively, where the material properties of the material forming the wall 62 are such that the material is resiliently expandable then at least part of the wall 62 forming the elongated tube 20 may radially contract from a radially expanded state when there is no fluid 40 flowing or where the rate of flow of the fluid 40 through the internal passageway 22 is reduced. Both the non-radially expanded and radially contracted states of the elongated tube 20 correspond to a relatively smaller diameter of at least a portion of the internal passageway 22 as opposed to the enlarged diameter of the internal passageway 22 associated with the radial expansion of the elongated tube 20.

[45] When the internal passageway 22 is in the relatively smaller diameter state the internal wall surface 60 defining the internal passageway 22 and the external wall surface 64 of the elongated tube 20 have a relatively small diameter. The smaller diameter state of the internal passageway 22 is useful for when the distal end 27 of the elongated tube 20 is being inserted through a patient's skin and blood vessel wall 32 into the interior of the blood vessel 30.

This is because punctures need only be made through the patient's skin and the wall 32 in the patient's blood vessel 30 having smaller respective diameters that enable the distal end 27 of the elongated tube 20, in the non- radially expanded state, to be inserted percutaneously into the interior of the blood vessel 30.

[46] The diameter of the internal passageway 22 and/or the external wall surface 64 of the elongated tube 20 may be any suitable size when the elongated tube 20 is in the non-radially expanded state. For example, the diameter of the internal passageway 22 or the external wall surface 64 when the elongated tube 20 is in the non-radially expanded state may be up to 1 mm or up to 2mm or greater than 2mm. The diameter of the internal passageway 22 and the external wall surface 64 of the elongated tube 20 may be similar to the diameters of existing catheters in use by medical practitioners.

[47] When the distal end 27 of the elongated tube 20 is inserted percutaneously into the interior of the blood vessel 30 the needle 50 may be withdrawn from the internal passageway 22 within the elongated tube 20. A first end 72 of a flexible tube 70 may be inserted into the hollow space 13 within the intermediate portion 14 and fixed in position by any suitable means. For example, the first end 72 of the flexible tube 70 may include a coupling that is shaped and configured to removably and sealingly connect with the hollow space 13 within the intermediate portion 14 so as to provide a sealed fluid connection between the flexible tube 70 and the hollow passageway 12 through the intermediate portion 14 of the catheter 10. A second end 74 of the elongated tube 70 is connected to a manual or computer controlled electronic or mechanical syringe 76 for injecting the fluid 40 through the elongated tube 70 and the internal passageway 22 of the catheter 10 into the blood vessel 30 at rate required by the medical practitioner for the procedure being conducted. The flexible tube 70 may have a diameter larger than the diameter of the internal passageway 22 of the elongated tube 20 when in the radially expanded or contracted states. [48] When the catheter 10 is positioned with the distal end 27 of the elongated tube 20 inserted percutaneously into the interior of the blood vessel 30 the rate of flow of the fluid 40 through the internal passageway 22 may commence or increase to a rate desired by the medical practitioner. When the rate of flow of the fluid 40 through the internal passageway 22 to the interior of a patient blood vessel 30 is increased for the purpose of the fluid 40 acting as a contrast agent when, for example, conducting a CT scan of a portion of the patient's vascular system or other bodily tissue the flow of the fluid 40 through the internal passageway 22 exerts an outward force against the internal wall surface 60 of the elongated tube 20 that is relatively greater in magnitude to when there is no flow or only a small rate of flow of the fluid 40. As mentioned above, the material properties of the wall 62 are such that at different flow rates of the fluid 40 involving different magnitudes of pressure on the internal wall surface 60, the material of the wall 62 expands under this pressure such that the elongated tube 20 radially expands and the diameters of the internal wall surface 60, the external wall surface 64 and the internal passageway 22 enlarge.

[49] Enlargement in the diameter of the internal passageway 22 of the elongated tube 20 enables greater fluid flow rates and greater quantities of fluid 40 to be delivered through the internal passageway 22 of the catheter 10 at lower flow speeds and lower pressure compared with when the diameter of the internal passageway 22 is not enlarged. Accordingly, when the catheter 10 is positioned with the distal end 27 of the elongated tube 20 inserted percutaneously into the interior of the blood vessel 30 the enlargement in the diameter of the internal passageway 22 of the elongated tube 20 enables greater fluid flow rates and greater quantities of fluid 40 to be delivered to the interior of the blood vessel 30 over a given period of time. As the diameter of the internal passageway 22 increases and as the diameter of the external wall surface 64 of the elongated tube 20 also increases the external wall surface 64 will tend to stretch the skin and tissue surrounding the holes punctured through the patient's skin and wall 32 of the patient's blood vessel 30. However, the resilience of human skin and tissue is such that this expansion will typically not result in tearing or significant damage beyond the damage initially caused by the insertion of the distal end 27 of the elongated tube 20 percutaneously into the blood vessel 30 through the blood vessel wall 32. Thus, the diameter of the puncture hole through the patient's skin and the wall 32 in the patient's blood vessel 30 for the catheter 10 and the needle 50 is smaller than if used a larger fixed diameter conventional catheter is used in conjunction with a similarly larger diameter needle.

[50] As mentioned above, the material properties of the material used to form the wall 62 of the elongated tube 20 may be such that the material is expandable or resiliently expandable. Thus, when the rate of flow of the fluid 40 through the internal passageway 22 of the elongated tube 20 is reduced or stopped all together, the material properties of the wall 62 may be such that an associated reduction in pressure on the internal wall surface 60 of the elongated tube 20 results in the radial contraction of the elongated tube 20 and an associated reduction in the diameters of the internal passageway 22 and the external wall surface 64 of the elongated tube 20. The radial contraction of the elongated tube 20 may be such that the diameter of the internal passageway 22 of the elongated tube 20 reverts to the original non-radially expanded state of the elongated tube 20 prior to the application of fluid pressure against the internal wall surface 60. Alternatively, the radial contraction of the elongated tube 20 may be such that the diameter of the internal passageway 22 of the elongated tube 20 reverts to a magnitude that is at least less than it was when the flow rate of the fluid 40 through the internal passageway 22 was greater.

[51] When it is no longer required to inject the fluid 40 into the interior of the blood vessel 30 the rate of the fluid 40 through the internal passageway 22 may be reduced. This results in the radial contraction of the elongated tube 20 and an associated reduction in the diameters of the internal passageway 22 and the external wall surface 64 of the elongated tube 20. Also, the patient's skin, blood vessel wall 32 and other tissue surrounding the external wall surface 64 of the elongated tube 20 may relax from their stretched condition as a result of the reduction in the diameter of the external wall surface 64 of the elongated tube 20. [52] In the embodiments described above, the material forming the wall 62 of the elongated tube 20 may include any suitable expandable material. Some materials which can be used include polymeric materials showing strain (expansion) hardening behaviour requiring increasing fluid flow rates to sustain expanded diameter states for the internal passageway 22. Furthermore, the material may have properties so as to be stiffer at lower temperatures compared with higher temperatures when the material may become more flexible and the elongated tube 20 may become more expandable. The wall 62 of the elongated tube 20 may be formed out of a material that at ambient temperatures would behave like a conventional thermoplastic with relatively high resilience, hardness or stiffness to facilitate insertion of the distal end 27 of the elongated tube 20 into the blood vessel 30, whereas, at around 37⁰C the material would exhibit more elastomer like behaviour requiring a relatively low force to be applied on the internal wall surface 60 of the wall 62 for the wall 62 for the elongated tube 20 to radially expand. The material forming the wall 62 of the elongated tube 20 may have properties so as to expand due to a combination of the temperature of the material and properties of the fluid 40 delivered through the internal passageway 22. Such properties of the fluid 40 may include the pressure of the fluid 40 against the internal wall surface 60 or a chemical in the fluid 40 that reacts with the material forming the wall 62.

[53] The material used to form the wall 62 may exhibit strain hardening, or in other words, a reduction in ductility at approximately 100% expansion thereby allowing a 1 mm diameter catheter to expand to 2mm in diameter and also to prevent the elongated tube 20 from ballooning or expanding uncontrollably. Some materials that could be used to form the wall 62 include polyolefins or modified polyolefins including (polyolefin co-polymers or grafted polyolefins) such as low density polyethylene (LDPE), high density polyethylene (HDPE) and linear low density polyethylene (LLDPE), polyesters, polyamides, halogenated polymers, silicones and segmented polyurethane based materials, blends or composites thereof may also be used to form the material of the wall 62 when they have the necessary mechanical characteristics.

[54] Furthermore, the material forming the wall 62 may be selected from a group of materials exhibiting glass transition characteristics having a glass transition temperature just below body temperature to facilitate a relatively stiff material for the wall 62 of the elongated tube 20 when inserting the elongated tube 20 into the blood vessel 30 and a relatively softer mechanical properties once inserted into the blood vessel 30. An advantage of the material forming the wall 62 exhibiting glass transition characteristics having a glass transition temperature just below body temperature is that radial expansion of the elongated tube and the corresponding enlargement in the diameter of the internal passageway 22 are facilitated as is a reduction in irritation to the tissue of the patient surrounding the puncture through which the elongated tube 20 is inserted. Furthermore, the material forming the wall 62 of the elongated tube 20 may also be selected from a group exhibiting haemo-compatibility characteristics.

[55] Examples of suitable materials for forming the wall 62, which may exhibit some or all of the above characteristics include polyurethane thermoplastic elastomer (PUTPE), polyesters (polybutylene terephthalate (PBT), polyamides (nylon 12), functionalised polyolefins (ethylene acrylic acid, ethylene vinyl acetate (EVA)), fluorinated polymers (fluorinated ethylene propylene (FEP and PTFE)) , silicone elastomers. Any other suitable materials meeting the requirement of the material of the wall 62 whereby the elongated tube 20 is radially expandable in response to a characteristic of the material 40 being delivered through the internal passageway 22 will fall within the scope of the invention. For example, any material may be used to form the wall 62 if, as a result, elongated tube 20 is radially expandable in response to outwardly directed pressure applied to the internal wall surface 60 of the elongated tube 20 by a flow of the fluid 40 through the internal passageway 22

[56] The catheter 10, and in particular the elongated tube 20, can be manufactured by, for example, extrusion, casting or moulding. Particularly preferred is extrusion whereby one or more layers of plastic material can be processed (co-extruded) into the elongated tube 20.

[57] Referring to Figures 7 to 9 there is shown another form of the catheter 10 of the invention. Instead of a smooth cylindrically shaped wall 62 of the elongated tube 20, the embodiment illustrated in Figures 7 to 9 has an elongated tube 20 having a wall 62, which in the non-radially expanded state, has a plurality of folds 80,82 about its circumference. As shown in Figure 8, when the internal passageway 22 of the elongated tube 20 non-radially expanded state the wall 62 has a star-shaped sectional profile. Each one of the folds 80,82 may extend longitudinally along substantially the entire length of the elongated tube 20. When the internal passageway 22 is in the non- radially expanded state shown in Figure 8 the internal passageway 22 defined by the internal wall surface 60 of the wall 62 has a relatively smaller sectional area than when the elongated tube 20 is radially expanded as illustrated in Figure 9.

[58] The material forming the wall 62 is such that when the distal end 27 of the tube 20 is inserted percutaneously into the interior of the blood vessel 30 and when the fluid 40 is delivered through the internal passageway 22 the pressure of the fluid 40 against the internal wall surface 60 causes the folds 80,82 to open. When the folds 80,82 open the wall 62 assumes a substantially circular sectional profile as illustrated in Figure 9. Alternatively, the folds 80,82 may partially open so that the folds 80,82 partially remain but are less pronounced than the folds 80,82 in the illustration in Figure 8.

[59] In each embodiment of the catheter 10, the proximal end 25 of the elongated tube 20 may be connected to, or integrally formed with, the distal end 11 of the base member 15 by any suitable means. The distal end 1 1 of the base member 15 may include an opening into which the proximal end 25 of the tube 20 may be inserted and retained therein. The diameter of the opening in the distal end 1 1 of the base member 15 may be equivalent to the enlarged diameter of the external wall surface 64 of the elongated tube 20 when the elongated tube 20 radially expanded. Alternatively, the diameter of the opening in the distal end 1 1 of the base member 15 may enlarge along with the enlargement in the diameter of the external wall surface 64 of the elongated tube 20 due to radial expansion of the elongated tube 20. This is so that the diameter of the internal passageway 22 at the proximal end 25 of the elongated tube 20 will not constricted by the opening at distal end 1 1 of the base member 15 and will not act as a bottle-neck for the fluid 40 being delivered through the internal passageway 22. [60] When the elongated tube 20 is not radially expanded, as in the embodiment illustrated in Figures 7 and 8, the external wall surface 64 at the proximal end 25 of the elongated tube 20 has an uneven surface with a series of consecutive peaks 84 and troughs 86. Each of the peaks 84 is associated with an outward fold 80 in the wall 62 while each one of the troughs 86 is associated with an inward fold 82 in the wall 62. To seal the space between each trough 86 and the opening in the distal end 1 1 of the base member 15 a filling material in the form of a compressible or flexible material may be used to fill the space and prevent ingress or egress of fluid through the space between each trough 86 and the opening in the distal end 11 of the base member 15. The material used to seal the space between the trough 86 and the opening in the distal end 1 1 of the base member 15 may be chosen so as not to prevent the folds 80,82 from opening under the action of the pressure of the fluid 40 against the internal wall surface 60 of the elongated tube 20.

[61] The filling material that seals the space between each trough 86 and the opening in the distal end 1 1 of the base member 15 may be compressed between the external wall surface 64 of the elongated tube 20 and the opening in the distal end 1 1 of the base member 15 when the elongated tube 20 radially expands. As the elongated tube 20 further expands radially the filling material is further compressed and also progressively increases its resistance to compression. As a result the filling material that seals the space between each trough 86 and the opening in the distal end 11 of the base member 15 may also limit the extent of radial expansion of the elongated tube 20 to a predetermined magnitude by providing a progressively increasing resistance the further radial expansion of the elongated tube 20.

[62] The material used to form the wall 62 of the elongated tube 20 may be any suitable material that is capable of being formed with a plurality of the folds 80,82 to provide the wall 62 with the plurality of consecutive peaks 84 and troughs 86 as illustrated in Figure 8. The material should also exhibit properties such that pressure of the fluid 40 applied against the internal wall surface 60 of the wall 62 during delivery of the fluid 40 through the internal passageway 22 causes the folds 80,82 to open partially or completely as required to provide the radial expansion of the elongated tube 20 and an enlargement of the diameter of the internal passageway 22. The material forming the wall 62 of the elongated tube 20 should also exhibit properties such that the radial expansion of the elongated tube 20 and the enlargement of the diameter of the internal passageway 22 can be achieved without risk, or at least with reduced risk, of the wall 62 of the elongated tube 20 breaking under the action of the pressure of the fluid 40 against the internal wall surface 60, particularly at high flow rates of 1 or more millilitres per second and as much as up to 3 or 4 millilitres per second and as much as up to 7 or 8 millilitres per second and as much as up to 30 or 40 millilitres per second.

[63] Figures 10 and 1 1 illustrate another form of the catheter 10 of the invention similar to the embodiment described above and illustrated in Figure 8 wherein the wall 62 has a plurality of inwardly extending folds 82 and outwardly extending folds 80 respectively providing a plurality of troughs 86 and peaks 84 in the wall 62. However, in the embodiment illustrated in Figures 10 and 1 1 , an external layer of flexible material 90 is deposited on and may be adhered to the external wall surface 64 of the elongated tube 20. The external layer 90, in the embodiment illustrated in Figures 10 and 11 , substantially fills the spaces associated with each trough 86 immediately adjacent the exterior of the external wall surface 64. By filling the troughs 86, the flexible material 90 provides a smooth external surface 92 for the elongated tube 20 instead of the relatively uneven external wall surface 64 of the embodiment illustrated in Figures 7 to 9.

[64] The smooth external surface 92 of the elongated tube 20 is advantageous during and after the distal end 27 of the elongated tube 20 is inserted percutaneously into the interior of the blood vessel 30 because the skin, blood vessel wall 32 and other tissue of the patient surrounding the smooth external surface 92 of the elongated tube 20 is in substantially uniform contact with the smooth external surface 92 of the elongated tube 20. Thus, the smooth external surface 92 surrounding the uneven external wall surface 64 of the wall 62 is advantageous in providing a substantial seal between the elongated tube 20 and the skin, blood vessel wall 32 and other tissue of the patient surrounding the puncture through which the distal end 27 of the elongated tube 20 is inserted. By providing a substantial seal between the elongated tube 20 and the skin, blood vessel wall 32 and other tissue of the patient surrounding the puncture through which the distal end 27 of the elongated tube 20 is inserted the flexible material 90 may prevent the ingress or egress of the fluid 40 or any other material through gaps between the skin, blood vessel wall 32 and other tissue of the patient and the elongated tube 20 when the elongated tube 20 is inserted through the patient's skin and into the interior of the patient's blood vessel 30.

[65] In the embodiments illustrated in Figures 7 to 1 1 the external wall surface 64 and the internal wall surface 60 are connected by a planar star shaped surface 29 surrounding the opening 28 at the distal end 27 of the elongated tube 20. The planar star shaped surface 29 is annular and lies in a plane that is substantially perpendicular to the longitudinal axis X of the elongated tube 20.

[66] Figure 12 illustrates a variation of the catheter 10 of Figures 7 to 11 wherein the flexible material 90 surrounding the external wall surface 64 of the elongated tube 20 forms the tapering portion 31 at the distal end 27 of the elongated tube 20 similar to the embodiments illustrated in Figures 3 and 4. In the tapering portion 31 of the embodiment shown in Figure 12 the smooth external surface 92 and the internal wall surface 60 of the elongated tube 20 are connected by the planar surface 29 surrounding the opening 28 at the distal end 27 of the elongated tube 20. The planar surface 29 has a circular outer edge and a star shaped inner edge and lies in a plane that is substantially perpendicular to the longitudinal axis X of the elongated tube 20. Accordingly, the distal end 27 of the elongated tube 20 is formed with a tapered portion 31 that facilitates ease of insertion of the distal end 27 of the elongated tube 20 through the holes in the skin and blood vessel wall 32 punctured by the sharpened tip 58 of the needle 50. The flexible material 90 may also help retain the shape of the elongated tube 20 during insertion percutaneously into the interior of the blood vessel 30 and/or to help restrict the overall radial expansion of the elongated tube 20.

[67] The material that is used to form the layer of flexible material 90 surrounding the external wall surface 64 of the elongated tube 20 is such that when the pressure of the fluid 40 against the internal wall surface 60 of the elongated tube 20 causes radial expansion of the elongated tube 20, as illustrated in Figure 1 1 , the external flexible layer 90 flexes or stretches along with the wall 62 of the elongated tube 20. The external flexible layer 90 may flex or stretch so as to present a substantially smooth and continuous external surface 92 to the skin, blood vessel wall 32 and other tissue of the patient surrounding the external surface 92 of the external flexible layer 90 surrounding the external wall surface 64 of the elongated tube 20. As a result, the external surface 92 of the flexible layer 90 continues to provide and maintain a substantial seal between the external surface 92 of the flexible layer 90 and the skin, blood vessel wall 32 and other tissue of the patient surrounding the external surface 92 even as the elongated tube 20 radially expands or radially contracts.

[68] Methods of forming the layer of flexible material 90 onto the external wall surface 64 of an extruded or otherwise formed elongated tube 20 include dip or spray coating of polymers from solution or polymer precursors optionally from solution prior to forming a continuous overcoat layer(s) via the process of drying or the action of a polymerisation trigger such as the application of light (photo-polymerisation), heat (thermal polymerisation) moisture or time.

[69] Suitable chemistries for the layer of flexible material 90 include elastomers based on urethane or silicone (silane) chemistries, and those including points of unsaturation (eg acrylate). Under the optimal processing conditions, the elastomer material forming the layer of flexible material 90 would fill the troughs 86 between consecutive peaks 84 without significant increase to the overall diameter of the elongated tube 20.

[70] One method to form the tapering portion 31 at the distal end 27 of the elongated tube 20 is periodic fluctuation of the speed of the take-off units during extrusion. Different elongated tube 20 profile perimeters can be obtained by varying the take-off speed for a constant extruder throughput rate. The tapering portion 31 can also be formed using thermal orientation, laser ablation or a secondary process. [71] Each of the embodiments of the catheter 10 described above and illustrated in the attached Figures include a form of the elongated tube 20 having the internal passageway 22 extending between the proximal end 25 and the distal end 27 of the elongated tube 20 wherein the elongated tube 20 is configured for radial expansion to enlarge the diameter of at least a portion of the internal passageway 22. Furthermore, in some embodiments, the delivery of the fluid 40 or other material through the internal passageway 22 results in a pressure of the fluid being applied against the internal wall surface 60 of the wall 62 of the elongated tube 20 that causes radial expansion of the elongated tube 20 and enlargement of the diameter of internal passageway 22 by magnitudes that are proportional to the pressure of the fluid 40 being delivered through the internal passageway 22. Thus, the diameter of internal passageway 22 of the elongated tube 20 of the catheter 10 is proportional to the magnitude of the pressure of the fluid 40 within the internal passageway 22 and, hence, the rate of flow of the fluid 40 being delivered through the internal passageway 22 to the interior of the patient blood vessel 30.

[72] In another embodiment, the elongated tube 20 may be formed or configured such that the material forming the wall 62 of the elongated tube 20 includes a combination of the characteristics of the wall 62 of each of the embodiments described above. That is, the material forming the wall 62 may be an expandable material or a resiliently expandable material that is formed with one or more of the folds 80,82 such that the diameter of the internal passageway 22 expands under the action of fluid being delivered through the internal passageway 22 either as a result of the expandable properties of the material forming the wall 62 or as a result of the structural shape of the cross- section of the wall 62 or as a result of a combination of both.

[73] Furthermore, another embodiment may also include forming the wall 62 from an expandable material or a resiliently expandable material with one or more of the folds 80,82 wherein the flexible layer 90 is deposited on and adhered to the external wall surface 64 of the elongated tube 20.

[74] Yet another embodiment, not illustrated, may include the elongated tube 20 being formed with a wall 62 that is twisted about the longitudinal axis X of the elongated tube 20. In this embodiment, the wall 62 of the elongated tube

20 is twisted about a longitudinal axis of the elongated tube 20 and radial expansion of the elongated tube 20 occurs by untwisting the wall 62 of the elongated tube 20. When the fluid 40 or other material is delivered through the internal passageway 22 the elongated tube 20 is responsive to a characteristic of the fluid 40 or other material, such as a pressure of the fluid 40 against the internal wall surface 60 of the tube member 20, such that the wall 62 of the elongated tube 20 untwists to provide the radial expansion of the elongated tube 20 and enlargement of the diameter of the internal passageway 22.

[75] As can be appreciated, the structural shape or configuration of the wall 62 forming the elongated tube 20 may take any suitable form and still fall within the scope of the invention if the result of that shape or configuration is such that the internal passageway 22 can radially expand to enlarge the diameter of the internal passageway 22 in response to a characteristic of the fluid 40 or other material being delivered through the internal passageway of the elongated tube 20.

[76] Although the embodiments of the catheter 10 described above have been described in the context of their use in relation to the percutaneous delivery of material to, say the blood vessels of humans, it is to be appreciated that the catheter 10 may also have application in relation to the percutaneous delivery of the fluid 40 or other material to the interior of blood vessels or other organs or tissues of animals.

[77] Furthermore, the invention may also be applicable in relation to devices for delivering material through membranes or other barriers. In such applications, the properties of the elongated tube 20 of being configured for radial expansion to enlarge a diameter of at least a portion of the internal passageway 22 in response to a characteristic of the material being delivered through the internal passageway 22 may enable greater rates of delivery of the material through the membrane while only requiring a smaller initial hole to be made through the membrane or other barrier to enable the distal end 27 of the elongated tube 20 to be inserted through the membrane or other barrier. [78] Radial expansion of the elongated tube 20 of the catheter 10 may also provide a safety valve functionality (i.e., exhibited safety valve characteristics) whereby the internal passageway 22 may enlarge in diameter in response to an increase in pressure of the fluid 40 within the internal passageway 22 due to a partial blockage in the internal passageway 22. The expansion in diameter of the internal passageway 22 may free the blockage and allow the pressure of the fluid 40 within the internal passageway 22 to subside and allow the flow of the fluid 40 to resume.

[79] The catheter 10 can also be used to deliver anticancer drugs or other drugs to the heart or other organs or parts inside the body. The catheter may also have applications in relation to the delivery and retrieval of stents or other implantable or surgical medical devices within the body. The stent or other implantable or surgical medical device may be placed within the internal passageway 22 of the elongated tube 20 and radially expanded or contracted as required for, for example, depositing, receiving and holding the stent or other implantable or surgical medical device for delivery and retrieval from within the body.

[80] In one preferred form of the invention, the diameter of the elongated tube 20 of the catheter 10 may exhibit radial expansion as a function of pressure within the elongated tube 20 in the order of magnitude shown in Figure A below. As can be seen from Figure A below the diameter of the elongated tube 20 remains at 1 mm until the pressure within the elongated tube 20 reaches in excess of 100 mmHg. At this pressure, the diameter of the elongated tube 20 begins to radially expand. As the pressure within the elongated tube 20 continues to increase the diameter of the elongated tube 20 continues to radially expand until reaching 2mm or some other predetermined diameter. In Figure A, the diameter of the elongated tube 20 reaches 2mm when the pressure within the elongated tube 20 reaches approximately 140mmHg. The properties of the elongated tube 20 of the catheter 10 are such that as the pressure within the elongated tube 20 continues to increase beyond 140mmHg the diameter of the elongated tube 20 remains 2mm. In other words, the diameter of the elongated tube 20 will expand to a maximum size, in this case 2mm, and will remain at the maximum size irrespective of any further increase in pressure within the elongated tube 20 beyond 140mmHg.

Diameter (mm)

Figure A

[81] Examples of forms of the invention and materials and methods for use with the invention will now be provided. In providing these examples, it is to be understood that the specific nature of the following description is not to limit the generality of the above description.

[82] Experiments were conducted on 5 catheters each formed with an elongated tube with a star shaped sectional profile with 8 radially outwardly projecting peaks, an overall external diameter of ~1.5mm and a wall thickness of 0.12mm. Each of the 5 catheters was formed out of a different catheter material to determine the characteristics of each material when formed into a catheter with the above structural characteristics. The five materials included polyurethane (PU1595A, PU550D, PU560D), Nylon and high density polyethylene (HDPE).

[83] PU550D catheter material is softer with more compliance at body temperature (37.5^QC) than at ambient temperature. This is favourable in terms of reducing the discomfort to the patient when the catheter is in the vein. PU550D is stiffer at ambient temperature which is favourable for inserting the catheter into the vein. Accordingly, the catheter formed out of PU550D was tested at ambient temperature and at body temperature. [84] Figures B and C below show experimentally measured radial expansion of the five elongated tubes versus the pressure of fluid within the internal passageway of the elongated tube.

40 80 120 160 200 240

Expansion Rate [%]

Figure B

[85] Figure B above shows the static pressure versus expansion rate measurements for star-shaped sectional profile catheters made from polyurethane (PU), high density polyethylene (HDPE) and nylon (NY).

20 40 60 80 100 120

Expansion rate (%)

Figure C [86] Figure C above shows the pressure versus expansion rate measurements for water injected through the internal passageway of the elongated tube of the catheter with a medical power injector into a simulated vein for star-shaped sectional profile catheters made from polyurethane (PU) and high density polyethylene (HDPE).

[87] Experiments were conducted on 3 catheters each formed with an elongated tube with a star shaped sectional profile with 8 radially outwardly projecting peaks, an overall external diameter of the elongated tube of ~1.5mm and a wall thickness of 0.12mm. Each of the three catheters was formed from a different type of polyurethane material.

[88] Table A below shows the radial expansion of the overall external diameter of the elongated tube of each of the three catheters when water was injected through the internal passageway of the elongated tube at a rate of 40 ml/s.

[89] Table A also shows the radial expansion of the overall external diameter of the elongated tube of each of the three catheters after the injection of water at a rate of 40 ml/s is reduced to a rate of 0 ml/s. The radial expansion of the overall external diameter of the elongated tube is expressed as a percentage of the overall external diameter of the elongated tube prior to expansion.

[90] The data in Table A shows that the overall external diameter of the elongated tube of the catheter showed significant radial expansion during injection. Also, the overall external diameter of the elongated tube of the catheter showed significant radial contraction close to the original diameter when the rate of injection was reduced to nil. [91] Experiments were conducted on 4 catheters each formed with an elongated tube with a circular shaped sectional profile, an overall external diameter of the elongated tube of ~1.5mm and a wall thickness of 0.12mm. Each of the 4 catheters was formed out of polyurethane (PU) or polyurethane (PU) + 1 , 2 or 3wt%M 44'-diphenylmethane diisocyanate (MDI).

[92] Figure D below shows the static pressure versus expansion rate measurements for 4 catheters each formed with an elongated tube with a circular shaped sectional profile catheter prepared from polyurethane (PU) or polyurethane (PU) + 1 , 2 or 3wt%M 44'-diphenylmethane diisocyanate (MDI)

10 20 30 40 50 60

Expansion Rate [%]

Figure D

[93] Other modifiers, for example those which alter the chemical structure of the polymeric material used in the wall of the elongated tube of the catheter to increase the number of chemical and/or physiochemical interactions between polymer chains can be employed. Examples of these reagents include di- or multi-functional isocyanates (PBDT = PoIy(1 , 4-butandiol), toluene- 2,4diisocyanate), di- or multi-functional oxazolines, di- or multi-functional anhydrides, di-or multifuinctinal-epoxides or combinations thereof and particulates such as organo-functional nano- and micro-scale clays and other such inorganic filler materials. [94] Catheters formed with an elongated tube with a circular shaped sectional profile prepared from polyurethane and the cross-linker MDI were found to readily expand to -35% before strain hardening made further increases in expansion more difficult (e.g., constrained expansion) and the final expansion reached was over 50%.

[95] Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all such variations and modifications which fall within the spirit and scope.

[96] Future patent applications may be filed on the basis of or claiming priority from the present application. It is to be understood that the following provisional claims are provided by way of example only, and are not intended to limit the scope of what may be claimed in any such future application. Features may be added to or omitted from the provisional claims at a later date so as to further define or re-define the invention or inventions

Claims

Claims:

1. A catheter for percutaneous delivery of material, the catheter including:

an elongated tube having an internal passageway extending between proximal and distal ends of the tube;

the elongated tube being configured for radial expansion to enlarge a diameter of at least a portion of the internal passageway;

wherein the radial expansion of the elongated tube is responsive to a characteristic of a material being delivered percutaneously through the internal passageway of the elongated tube.

2. The catheter of claim 1 , wherein the material being delivered through the internal passageway includes a fluid and the characteristic of the material is a pressure of the fluid.

3. The catheter of claim 2, wherein the radial expansion of the elongated tube is responsive to a threshold of the pressure of the fluid.

4. The catheter of claim 1 , wherein the elongated tube is formed from an expandable material.

5. The catheter of claim 1 , wherein the elongated tube is formed from a resiliently expandable material so that the elongated tube can radially expand in response to the characteristic of the material being delivered through the internal passageway and radially contract in response to a change in the characteristic of the material being delivered through the internal passageway.

6. The catheter of claim 1 , wherein the elongated tube has a sectional profile that is shaped to facilitate the radial expansion of the elongated tube.

7. The catheter of claim 6, wherein the wall has a star-shaped sectional profile.

8. The catheter of claim 1 , wherein the elongated tube has a wall including one or more folds that open to facilitate the radial expansion of the elongated tube.

9. The catheter of claims 6 to 8, wherein the elongated tube is formed out of material that resiliently deforms to facilitate the radial expansion of the elongated tube in response to the characteristic of the material being delivered through the internal passageway and radial contraction in response to a change in the characteristic of the material being delivered through the internal passageway.

10. The catheter of claim 5 or claim 9, wherein the material being delivered through the internal passageway includes a fluid and the characteristic of the material is a pressure of the fluid and the change in the characteristic of the material is a reduction in the pressure of the fluid

1 1. The catheter of claim 1 , wherein the wall has an external surface and a layer of flexible material is deposited on the external surface.

12. The catheter of claim 1 , wherein the elongated tube has a wall including one or more radially inwardly extending folds that each form a trough in an external surface of the wall and a layer of flexible material deposited on the external surface in each trough.

13. The catheter of claim 1 , wherein the elongated tube has a wall that is twisted about a longitudinal axis of the elongated tube and the radial expansion of the elongated tube occurs by untwisting the elongated tube.

14. A device for delivery of material, the device including:

wherein the radial expansion of the elongated tube is responsive to a characteristic of a material being delivered through the internal passageway of the elongated tube.