Abstract
A self-propelled device for locomotion through a lumen, comprising a set of serially arranged inflatable chambers, the end ones of which expand at least radially when inflated. Connecting passages provide fluid communication between each pair of adjacent chambers. A fluid source is attached to one of the end chambers. The connecting passages are such that the fluid inflates the chambers in a sequence, beginning with the chamber closest to the source, and ending with the chamber furthest from the source. The same sequence occurs when the chambers deflate, beginning with the chamber closest to the source, and ending with the chamber furthest from the source. The fluid source can either be a fluid supply tube, extending to a supply outside the lumen, or it can be built-in and carried by the device. The device can crawl either along the lumen wall or on an inserted guide wire.
Claims
1. A device for locomotion through a lumen, comprising: a set of serially arranged inflatable chambers; and a fluid source configured to supply fluid to said set of serially arranged inflatable chambers, such that said fluid inflates the chambers of said set of serially arranged inflatable chambers in a serial sequence, from a first end of said set to a second end of said set; wherein at least one chamber of said set of serially arranged inflatable chambers comprises an outer skin having at least one longitudinal section of greater rigidity than other sections of said outer skin, such that when said at least one chamber inflates, a bend is generated in said set of serially arranged inflatable chambers, at said at least one chamber.
2. A device according to claim 1, wherein said at least one longitudinal section is a reinforced section of said outer skin.
3. A device according to claim 2, wherein said reinforced section of said outer skin comprises one or more reinforcing strips.
4. A device according to claim 2, wherein said reinforced section of said outer skin is less flexible than the rest of the outer skin, such that said reinforced section is unable to stretch in the same manner as the other regions of said inflatable chamber.
5. A device according to claim 1, further comprising at least one connecting passage configured to provide fluid communication between each pair of adjacent chambers in said set of serially arranged inflatable chambers.
6. A device according to claim 1, wherein at least one chamber of said set of serially arranged inflatable chambers is configured to expand axially when inflated.
7. A device according to claim 1, wherein at least two chambers of said set of serially arranged inflatable chambers are configured to expand radially when inflated.
8. A device according to claim 7, wherein said at least two chambers are adapted to grip a wall of said lumen upon expanding radially.
9. A device according to claim 1, wherein said set of serially arranged inflatable chambers is configured to deflate in a serial sequence, from said first end of said set to said second end of said set, when said fluid flows out of said set of serially arranged inflatable chambers.
10. A device according to claim 9, wherein said device is configured to move along said lumen as the chambers of said set of serially arranged inflatable chambers inflate and deflate sequentially.
11. A device according to claim 1, further comprising: at least one tubular chamber disposed between said fluid source and said set of serially arranged inflatable chambers, said at least one tubular chamber being adapted to inflate radially so as to apply pressure to said lumen walls; and a pressure operated valve configured to close when a predetermined pressure higher than the pressure required to inflate said set of serially arranged inflatable chambers is applied thereto, said pressure operated valve being disposed between said tubular chamber and said set of serially arranged inflatable chambers, such that said set of serially arranged inflatable chambers is isolated from pressure applied to inflate said at least one tubular chamber.
12. A device for locomotion through a lumen, comprising: a set of serially arranged inflatable chambers; and a fluid source configured to supply fluid to said set of serially arranged inflatable chambers, such that said fluid inflates the chambers of said set of serially arranged inflatable chambers in a serial sequence, from a first end of said set to a second end of said set; wherein at least one chamber of said set of serially arranged inflatable chambers comprises an outer skin having at least one longitudinal section of greater rigidity than other sections of said outer skin, such that when said at least one chamber inflates, said set of serially arranged inflatable chambers is configured to transition to a bent state.
13. A device for locomotion through a lumen, comprising: a set of serially arranged inflatable chambers; and a fluid source configured to supply fluid to said set of serially arranged inflatable chambers, such that said fluid inflates the chambers of said set of serially arranged inflatable chambers in a serial sequence, from a first end of said set to a second end of said set; wherein at least one chamber of said set of serially arranged inflatable chambers comprises an outer skin having at least one longitudinal section of greater rigidity than other sections of said outer skin, such that when said at least one chamber inflates, those parts of said set of serially arranged inflatable chambers on either side of said at least one chamber, realign to have differently aligned axes.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which:
(2) FIG. 1 illustrates schematically a tip-propelled catheter device, constructed and operative according to a first preferred embodiment of the present invention;
(3) FIGS. 2A to 2I illustrates schematically how the fluid inflates the balloon cells of the device of FIG. 1 in a sequence that causes the device to move forward;
(4) FIG. 3A illustrates schematically a method of manufacturing the device of FIG. 1 using separate joined segments while FIGS. 3B and 3C illustrate further preferred embodiments of the device of FIG. 1 in which the fluid supply system is packed on board the device, thus providing an untethered device without a trailing fluid supply line;
(5) FIGS. 4A and 4B illustrate schematically a preferred embodiment of the device of FIG. 1, incorporating a passage for a central tube;
(6) FIGS. 5A to 5D illustrate schematically a further embodiment, which enables blood or another fluid to flow around the balloons of the device;
(7) FIGS. 6A to 6C illustrate schematically an embodiment in which some of the balloons in the device inflate and expand only axially, like a bellows;
(8) FIGS. 7A to 7C illustrate schematically an embodiment in which the device is constructed of one piece of flexible material with integral partitions and metal inter-balloon orifices;
(9) FIGS. 8A and 8B illustrate an embodiment similar to that of FIGS. 7A to 7C, but with the orifices formed in the material of the separator walls;
(10) FIG. 9 illustrates schematically an embodiment showing a Multiple Point Drive device enabling driving forces to be deployed along the whole device, which can thus be made longer than otherwise;
(11) FIGS. 10A and 10B illustrate schematically an embodiment similar to that of FIG. 9, but with an inflatable straight section operative as a dilator;
(12) FIGS. 11A to 11C illustrate schematically an embodiment of the present invention, which is able to turn or navigate round bends in the passage being negotiated;
(13) FIGS. 12A and 12B illustrate schematically an embodiment in which the locking occurs on an inside tube or guide wire;
(14) FIGS. 13A to 13D illustrate schematically an embodiment having a tapered tip able to force its way through partial blockages encountered;
(15) FIG. 14 illustrates an embodiment in which a turbine head is fitted to the front of the device, for burrowing its way through obstructions encountered;
(16) FIGS. 15A to 15B illustrate embodiments of the present invention, in which the device is utilized to determine parameters relating to the walls of a passageway negotiated by the device, such as internal diameter, and wall compliance; and
(17) FIG. 16 illustrates schematically an embodiment in which the device is used in a novel steering system in coordination with an internal steerable guide wire, the device being propelled on the guide wire or the outer walls of the passageway.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
(18) Reference is now made to FIG. 1, which illustrates schematically a tip-propelled catheter device 15 for traveling down a lumen 10, constructed and operative according to a first preferred embodiment of the present invention. The device preferably comprises a number of balloons 11 connected to each other by separators 12 with one or more small openings, preferably in the form of orifices 13 formed therein, such that all the balloons comprise a single volume. For ease of construction, the device can alternatively and preferably comprise a single inflatable balloon divided into separate balloon segments by separators with orifices such that the entire segmented balloon can be inflated through a single input. The balloon fabric is preferably held in place relative to the separators 12 by means of rings 17 or glued or molded to the separators. Whichever preferred construction is used, the device is connected by a single tube 16 to a fluid supply for inflating the balloons or the balloon segments. For the sake of simplicity, the operation of the device will be explained using the term balloon for each separate segment, although it is to be understood that the invention can equally be implemented using a single balloon segmented to form the separate segments. The inflation fluid used can be any one of a compatible gas or liquid.
(19) According to a further preferred embodiment of the present invention, the fluid supply can be taken from the passageway through which the device is moving, by means of an on-board pump, and ejected thereto after use, as more fully described herein below.
(20) Reference is now made to FIGS. 2A to 2I which illustrates schematically how the fluid inflates the balloon cells in a sequence that causes the proximal one to inflate first, increasing its diameter as well as its length. Being inflated, it locks itself against the inside walls of the tube, but at the same time, its increase in length advances the other cells which are not fully inflated yet and hence are not locked on the inside walls of the tubes. The cell are inflated in a sequence until the distal cell locks against the inner tube walls, but at a position further along the tube than that of the un-inflated balloon distal cell initial position. This situation is reached in FIG. 2E. The timing and order of the sequence is mandated by the fluid flow dynamics through the orifices, and the dynamics of the balloon inflation. Disconnecting the supply and allowing the fluid pressure to drop at this point, or pumping out the fluid, as shown in FIG. 2F, causes the proximal cell to deflate first reducing both its length and diameter. Since the distal cell and all of the intermediary cells, are at this point still fully inflated, they are still locked against the inner walls of the tube, thus pulling the proximal cell inward as the balloon deflates and decreases its length.
(21) The sequential motion series is repeated inducing motion of the entire device as can be seen in FIGS. 2A to 2I. The locomotion sequence is composed of two phases: inflation and deflation, with the arrows at the entrance of the inflation tube indicating the direction of fluid flow. The dynamics of the sequential inflation is as follows:
(22) The flow through an orifice is proportional to the square root of pressure difference across the orifice, and the square of the diameter of the orifice, such that the orifice sizes can be selected to provide specific inflation dynamics.
(23) Inflation phase: Initially, the pressure is equal in each balloon and is equal to the outside pressure, therefore the balloons are in deflated condition, as in FIG. 2A. When the pressure in the supply tube rises, the fluid begins to flow through the first orifice into the first (proximal) balloon, as in FIG. 2B. The pressure difference between the first and second balloons is now lower than the pressure difference between the supply tube and the first balloon, such that the flow rate in the second orifice is slower and the second balloon inflates more slowly than the first one. By this means, the pressure propagates in a controlled and gradual manner to the last (distal) balloon until the pressure in all the balloons is equal, as shown in FIG. 2E.
(24) Deflation phase: Now the pressure in the supply tube is reduced to the outside pressure, or the fluid is pumped out of the inflation tube, and there is then a pressure drop between the supply line and the first balloon. The fluid begins to flow out of the first balloon, as in FIG. 2F. Again, since the pressure difference between the supply tube and the first balloon is greater than between the rest of the balloons, the first balloon deflates first, then deflates the second, and so on until the last balloon is deflated, as in FIG. 2I.
(25) In a variation of the actuation sequence, it is possible to initiate the cycling process even before the last cell is fully deflated. In such a case there will always be a base point anchored to the passageway and hence will prevent unwanted slippage in the case of external forces. Furthermore, different orifices sizes, or different numbers of orifices, can be used between different positioned balloons to improve the locomotion and speed of the device, all according to the dynamics of the fluid flow in to, out of, and between balloons. Furthermore, the viscosity of the inflation fluid can be chosen to improve the locomotion dynamics.
(26) Reference is now made to FIG. 3A which illustrates schematically an alternative and preferred method of manufacturing the device, in which each section 31 is manufactured separately and sections are connected by separators 30 which act as clips for the balloon segments, with or without glue. Throughout this application, the use of the terms set or series of chambers which make up the structure of the device of the present invention, are understood to be applicable, and are thus wise claimed, whether the chambers are separate structural segments connected together, as shown in the preferred embodiment of FIG. 3A, or whether they are constructed of a single one piece structure separated into separate chambers by means of mechanical partitions, as shown in the preferred embodiment of FIG. 1.
(27) According to the above-described embodiments of the present invention, the supply line is attached externally to a fluid supply, and its control system, this being known as a tethered application. According to further preferred embodiments of the present invention, schematically illustrated in FIGS. 3B and 3C, the fluid actuation system can be packed on board the device, thereby obviating the need for a supply line to the outside. In the embodiment of FIG. 3B, a pump 35 is located on the device, pumping in the fluid through an opening 36 from its surrounding environment within the passageway, and expelling the fluid thereto also. If the device is operating, for example, in the vascular system, the fluid used is blood; if in a gas pipe, for example, it can use the gas to inflate and deflate the balloons; if in a regular tunnel or pipe, the fluid is the air within that tunnel or pipe. The actuation system can have an internal power source preferably in the form of a battery, or an external power source, such as an induced electromagnetic field or any other kind of induced power source. The device then moves forward unattached to any fluid supply line and solely under the control of commands transmitted to it from the outside.
(28) Alternatively and preferably, in a different untethered embodiment, as illustrated schematically in the embodiment of FIG. 3C, the inflating fluid is in the form of a gas, and is supplied to the inflatable balloons from an on-board reservoir 33 of the compressed gas. The inflation gas is therefore contained in a closed circuit, isolated from the fluid of the surrounding environment, and is returned to the reservoir 33 when the balloons are deflated, preferably by means of a small recycling compressor 34. The inflation fluid can then be of any suitable type of gas, independent of the fluid flowing through the passageway.
(29) Reference is now made to FIGS. 4A and 4B which illustrate schematically a further preferred embodiment of the present invention, in which a central passage 49 has been incorporated into the device, preferably running through the central region of each of the balloons and the separators. The orifices 43 for the sequential pressure regulation are then offset in the separator walls 42. The central passage can be used for inserting an optional optical fiber, a guide wire, electronic leads to a camera mounted in the nose of the device, or similar. Although not apparent because of the scale of the drawing of FIGS. 4A and 4B, the central passage is of such a size that there is a small space between the inner surface 49 of the balloons and the internally inserted wire or other internally threaded item 48, so that the wire or other item can move freely through the device. In the embodiment of FIG. 4B, an inner spring 47 has been added to the structure to support the inner tube 49 from collapsing on the guide wire 48 or other internally threaded item, and locking the tube onto it, when the balloon is inflated. Alternatively and preferably, the central passage can be used to allow a continuous flow of blood or other vital fluid through the lumen being negotiated by the device, so that the balloons of the device do not block such flow.
(30) FIGS. 4A and 4B describe the incorporation of a central passage for threading wire-like elements in a self-propelled locomotion device of the type of the previously mentioned embodiments of FIGS. 1 to 3 of the present invention. However, it is to be understood that the central passage described in the embodiments of FIGS. 4A and 4B, and the benefits arising therefrom, can also be advantageously incorporated in any of the prior art inflatable chamber self-propelling devices, and the present invention is meant to include also such embodiments.
(31) Reference is now made to FIGS. 5A to 5D which illustrate schematically a further preferred embodiment of the present invention, which enables blood or another fluid to flow around the balloons 51. This is useful in locomotion along arteries or tubes 50 where the fluid flow can not be stopped by the presence of the device, and bypasses are required. According to this embodiment, the balloons are constructed such that they do not have a circular shape when inflated. A longitudinal section of the outer skin of the balloon is constructed to be less flexible than the rest of the outer skin, preferably by the addition of longitudinal reinforcing strips 53 along the balloon length, such that the balloon does not expand to its full size, if at all, along these sections. FIG. 5B illustrates schematically a cross section of an uninflated balloon, while FIG. 5C shows an inflated balloon, showing the clear regions 59 through which the body fluid flow can continue uninterrupted. FIG. 5D shows an isometric view of the device with one balloon inflated.
(32) FIGS. 5A to 5D describe the incorporation of a fluid bypass section in the balloons of a self-propelled locomotion device of the type of the previously mentioned embodiments of the present invention, using serial chambers with automatic inflation sequencing. However, it is to be understood that the fluid bypass section described in the embodiments of FIGS. 5A to 5D, and the benefits arising therefrom, can also be advantageously incorporated in any of the prior art inflatable chamber self-propelling devices, and the present invention is meant to include such embodiments also.
(33) Reference is now made to FIGS. 6A to 6C which illustrate schematically a further preferred embodiment of the present invention, in which some of the balloons in the device are constructed to inflate and expand only axially, like a bellows, thereby providing a longer reach per motion cycle. In the preferred embodiment of FIG. 6A, balloons 61A and 61C are regular balloons which expand radially and axially when inflated, as shown in FIG. 6B, such that they perform the wall gripping functions of the device, while balloons 61B and 61D have reinforcing rings 62 built into their envelope, such that when they inflate, as shown in FIG. 6C, they generate significant axial expansion but little if any radial expansion.
(34) Reference is now made to FIGS. 7A to 7C which illustrate schematically a further preferred embodiment of the present invention, in which the device is constructed of one piece of flexible material with integral partitions 72 at the balloon segment dividers, and metal jet structures 70 inserted into the centers of these partitions to act as the orifices between successive balloon chambers 71. Such construction reduces the manufacturing costs of the device. Alternatively and preferably, a multiple orifice insert can be used.
(35) Reference is now made to FIGS. 8A and 8B which illustrate schematically a further preferred embodiment of the present invention, similar to that of FIGS. 7A to 7C, except that the orifices themselves 83 are formed in the material of the separator walls 82, thereby lowering construction costs even more. The material between sections is preferably made wider or stiffer to keep a constant orifice diameter. The supply pipe 86 can also preferably be manufactured as part of the same piece of material.
(36) Reference is now made to FIG. 9 which illustrates schematically a further preferred embodiment of the present invention, showing a Multiple Point Drive device. Groups 95 of driving balloons 91, or even individual driving balloons 91 can be separated with non inflatable tabular sections 94. This enables driving forces to be deployed along the whole device, resulting in a better traction and higher stroke per inflating sequence. This is very useful for moving through very long and curved passages, such as arteries or intestines or the like in medical applications. The device operates as a very long inchworm with propulsion forces along the whole body. An advantage of this embodiment, or of any embodiment using balloons over the complete length, over an embodiment using balloons only at the tip is that the crawling speed is higher since the effective stroke length is longer, and the pressure is distributed more evenly along the inner walls.
(37) Reference is now made to FIGS. 10A and 10B which illustrate schematically a further preferred embodiment of the present invention, which has some similarities to that of FIG. 9, except that the straight sections 109 are constructed of a material that does inflate under a predefined pressure. The balloon section 104 is propelled as explained above. A pressure valve 103 is built into the entrance to the balloon section 104, and is adapted to close when the pressure 106 is raised to some higher value than that used during normal inflation operation of the balloon propulsion section 104.
(38) This increased pressure can be used for expanding the straight chamber 109 of the device, which thus acts as a dilator section 105, available for producing therapeutic effects, without the increased inflation pressure damaging the balloon propulsion units. When the balloon propulsion units 104 have brought the device to its desired target position, the pressure 106 is increased, the valve 103 closes and the dilator 105 can be inflated with high pressure to perform its desired function. The valve 103 keeps the high pressure 106 out of the propulsion balloons. Alternatively and preferably, if the propulsion balloons 104 are made in such a way or of such a material that their inflation is limited, then no valve 103 is required.
(39) When the therapeutic procedure is complete, pressure is lowered, the valve 103 opens again, and the device can again be operated normally. The high pressure can be used to open a partially blocked artery for example, or for expanding a stent located in its collapsed state over the section 105, or for injecting a drug from the device into the passageway being traversed, or for any other action requiring the application of a localized mechanical pressure.
(40) The fluid supplied for propulsion can preferably be an X-Ray opaque fluid, so that it will be possible to observe the device using X-Ray imaging during insertion and propulsion.
(41) Reference is now made to FIGS. 11A to 11C which illustrate schematically a further preferred embodiment of the present invention, in which a reinforced area, preferably in the form of one or more strips 112, has been provided asymmetrically in the outer skin or wall of one or more of the balloons 111. When a balloon with such a reinforced area is inflated, the region where the reinforcement is located is not able to stretch in the same way as the other regions of the balloon, and a bending effect is generated, which can be used for turning or navigation of the device when a bend or a junction 115 in the lumen is reached, as in FIG. 11B. Such reinforcing strips can equally well be added to successive balloons of the device in order to generate a more gradual turn along the length of the device.
(42) FIGS. 11A to 11C describe the incorporation of a reinforced section for generating a turning effect in the balloons of a self-propelled locomotion device of the type of the previously mentioned embodiments of the present invention, using serial chambers with automatic inflation sequencing. However, it is to be understood that such a reinforced section for generating a turning effect as described in the embodiments of 11A to 11C, and the benefits arising therefrom, can also be advantageously incorporated in any of the prior art inflatable chamber self-propelling devices, and the present invention is meant to include such embodiments also.
(43) Reference is now made to FIGS. 12A and 12B which illustrate schematically a further preferred embodiment of the present invention, in which the locking occurs on an inside tube or guide wire 128. This is accomplished by making the outer surface of the balloon stiffer than the inner surface, either by using an intrinsically stiffer material for the outer skin, or, as shown in FIGS. 12A and 12B, by incorporating reinforcing ribs 121 in the outer wall. In FIG. 12A showing the balloons uninflated, though not visible in the drawing, there is a small gap between the inner passage of the balloons and the internally inserted tube or guide wire 128, so that the tube or wire or other threaded item can move freely through the uninflated device. As the balloons are inflated, the inner surface expands inwards, and eventually locks against the inner guide wire or tube, as shown in FIG. 12B. The inner surface of the balloons may preferably be fitted with fins 129, so that the balloon grips the inner tube or guide wire at narrow points, thereby increasing the pressure of the grip. Since the central axis of the device is occupied by the central tube or guide wire, the orifices 124 connecting the various balloons have to be offset from the center. Alternatively and preferably, a number of orifices can be used spread angularly around the central tube. As with the previous embodiment of FIGS. 6A to 6C, some of the sections can have essentially circular balloons, and other sections can be cylindrical axially extending balloons.
(44) FIGS. 12A and 12B describe the incorporation of a central passage for threading wire-like elements in a self-propelled locomotion device of the type of the previously mentioned embodiments of the present invention, using serial chambers with automatic inflation sequencing. However, it is to be understood that the central passage described in the embodiments of FIGS. 12A and 12B, and the benefits arising therefrom, can also be advantageously incorporated in any of the prior art inflatable chamber self-propelling devices, and the present invention is meant to include such embodiments also.
(45) Reference is now made to FIGS. 13A to 13C which illustrate schematically a further preferred embodiment of the present invention, in which the device is provided with a tapered tip 138 which, as the device advances through the passageway, is able to force its way through partial blockages 137 encountered. The tip partially compresses the blockage material against the wall of the passageway. Additionally, the device can preferably be fitted with a dilator section 136, as in the embodiment of FIGS. 10A and 10B, to complete the operation of clearing the partial blockage 137.
(46) Reference is now made to FIG. 13D which illustrates schematically a further preferred embodiment of the present invention, similar to that shown in the embodiment of FIGS. 13A to 13C, but in which the tip 134 is made inflatable by means of fluid connection to the most distal balloon. The front end 135 of the tip forces its way into the blockage 137 as the device crawls forward, and when the most distal balloon has filled up, the inflatable tip head also inflates, thus packing the blockage material against the internal wall of the passageway. Since inflation of the tip occurs automatically when the distal balloon has inflated, this embodiment is simpler than that of FIGS. 10A and 10B, where additional valving and pressure monitoring is required.
(47) According to further preferred embodiments of the present invention, in the arrangements shown in FIGS. 13A to 13D, where only some of the balloons are used for motion purpose, the rest of the balloons and the head can be used for other therapeutic purposes besides dilation.
(48) Reference is now made to FIG. 14 which illustrates schematically a further preferred embodiment of the present invention, in which a drilling head 143, such as a turbine or propeller, is fitted to the front of the device, such that it can burrow its way through obstructions 147 encountered during its progress down the passageway. The head is preferably hydraulically powered with the power preferably coming from a paddle 141 or similar, driven by the inflating fluid, or from another external hydraulic source. Alternatively and preferably, electric power can be used, which can preferably come from a battery. Alternatively and preferably, the head can be powered from a rotating guide wire inserted through the center bore of the device.
(49) FIGS. 13A to 13D and FIG. 14 describe the incorporation of various tip embodiments for enabling a self-propelled locomotion device of the present invention using serial chambers with automatic inflation sequencing, to force its way through partial blockages encountered in its path. However, it is to be understood that such tip embodiments as described in the embodiments of 13A to 13D and FIG. 14, and the benefits arising therefrom, can also be advantageously incorporated in any of the prior art inflatable chamber self-propelling devices, and the present invention is meant to include such embodiments also.
(50) Reference is now made to FIGS. 15A and 15B, which illustrate schematically further preferred embodiments of the present invention, in which the device is utilized to determine a number of parameters relating to the walls of the passageway through which the device passes. In particular, the device is able to provide information regarding the passageway internal diameter, and the compliance of the passageway walls. The device and this method of operating it is thus particularly useful for profiling the condition of a subject's blood vessels or any other passageway at remote locations in his/her body. The device, according to this embodiment, requires the addition of a pressure monitor at the fluid input, and of a flow meter to determine the volume of inflation fluid required to fill the balloons of the device.
(51) FIG. 15A illustrates a balloon, in this exemplary case, the proximal balloon 150, of the device of the present embodiment, at three different preferred locations along the length of a passageway, which, for the purposes of illustrating this preferred embodiment, will be regarded as a blood vessel. The blood vessel is shown having varying wall thicknesses, and hence a varying internal diameter. At point P3, the blood vessel inner diameter is large, at point P1 it is intermediate, and at point P2, it is a minimum. Correspondingly, the volume of fluid used to inflate the proximal balloon 150 is larger at point P3, less at point P1 and least at point P2. Measurement of the volumes required for inflation enables the blood vessel internal diameter to be determined at each cyclical point of the progress of the device through the vessel, once an initial calibration process has been performed to relate balloon volume to blood vessel diameter.
(52) Continuous monitoring of the flow of inflation fluid during sequential filling of the balloons of the device enables a determination to be made of which balloon is being filled as a function of time, since there is a noticeable pressure change as each successive balloon begins to fill up, and monitoring these pressure changes allows the balloon being filled to be determined. It is thus possible to relate continuous volume and pressure measurements as a function of time, to the particular balloon being filled at any time. Since the filling volume is related to the blood vessel internal diameter, it is thus possible to obtain an estimation of this internal diameter at each point along the length of the device. This can be repeated at different positions of the device as it progresses along the vessel, such that a complete diameter profile of the blood vessel may be obtained. This is illustrated in FIG. 15B, which is a schematic graph showing a plot of the inflation volume V, as determined from the flow rate into the device, as a function of position along the device, which itself is determined from the pressure changes noted as a function of time. Since each inflated balloon volume is a function of the vessel diameter, d, the ordinate is designated V(d). As is seen from the graph, a correlation is shown between the inflation volume of each balloon and the vessel diameter at each point P1, P2, P3.
(53) However, in addition to the use of the filling pressure to ascertain which balloon is currently being filled, this pressure can also be used in order to provide information about the compliance or rigidity of the vessel walls at points along its length. The position is known from the knowledge of which of the balloons is being filled at the time the pressure is measured, as explained above for the volume measurement. The vessel diameter at each point is also known from the method of FIG. 15B. There is a correlation between the vessel compliance, which is to be determined, and the pressure build-up and flow rate which can be measured, and hence the vessel wall compliance can be deduced from the corresponding time history of the pressure build-up and flow rate. Characterizing and calibrating measurements must first be performed in order to implement this correlation.
(54) Reference is now made to FIG. 16, which illustrates schematically a further preferred embodiment of the present invention, in which the device is used as a novel steering system in coordination with an internal pre-bent guide wire. In the prior art, steerable internal guide wires are generally used alone for negotiating curved passageways in the subject's body. However, such a steerable guide wire, in which the tip can be bent in the direction of a curve in the passageway being traversed, has the disadvantages that the tip can cause injury to the tissue of the internal wall of the passageway as it negotiates its way through the passageway, as can the trailing guide wire on curves in the passageway. According to this preferred embodiment of the present invention, the steerable guide wire 168 is used as an internal member of the inflatable device as shown in the embodiments of FIGS. 4A-4B, or in the embodiments of FIGS. 12A-12B, where the inflatable device propels itself forward on the internal guide wire. In FIG. 16, the configuration of FIGS. 4A-4B is used to illustrate this embodiment. The steerable guide wire 168 is kept retracted within the crawling device as it moves forward, except when a curve 162 in the subject's passageway is to be negotiated, or a Y-junction is reached when the tip has to be directed to one branch or the other, in either of which cases the steerable tip 165 of the guide wire is allowed to protrude by a small distance from the front end in order to direct the front end of the device at the bifurcation. The small protrusion length prevents the tip from damaging the passageway wall because of the protection of the front balloon surrounding the guide wire tip and keeping it centrally located in the passageway. Alternatively and preferably, the steerable guide wire tip can be left just inside the tip of the device, without protruding at all, and steered from within, such that it directs the tip of the device round the curve without becoming exposed at all outside of the device. Progress through the lumen is thus primarily made by the tip of the inflatable device rather than the tip of a guide wire, thereby increasing the safety of use.
(55) In the embodiments of the present invention using a central guide wire, such as are described in FIGS. 4A-4B and 12A-12B, the guide wire or central tube is generally inserted right to the end of the passage to be negotiated, and the device is allowed to crawl along it. However, there may be difficulties in inserting the guide wire all the way to its target, and in the process, the walls may be damaged by the tip, or by friction from the trailing guide wire, or dangerous plaque may be dislodged unintentionally. According to a further preferred embodiment of the present invention, a method of use of the device is provided whereby the internal guide wire is first inserted a short distance into the passageway to be traversed, typically of the order of 5 cm for passage down a blood vessel, is held in place externally, and the inflatable device is allowed to crawl along the passageway, as described in the embodiment of FIGS. 4A-4B, towards the tip of the guide wire. When the inflatable device has progressed sufficiently so that the steerable tip of the guide wire is preferably just enclosed within the device, the device is locked against the passage walls, and the guide wire is pushed forward a further short distance into the passage, and again held in place externally. The inflated device is then deflated to free it from the passage walls, and is then allowed to crawl forward until it again covers the exposed portion of the guide wire. This process is repeated until the guide wire reaches its target point. By this means, the guide wire is advanced within the passageway largely protected by the surrounding inflatable device, such that the likelihood of damage to the tissues of the passageway is greatly reduced.
(56) As an alternative to the device climbing the walls of the passage, and anchoring itself on the walls as the guide wire is advanced, this method can also be used with the embodiment described in FIGS. 12A-12B, in which the device climbs along the internal guide wire itself, without applying pressure on the walls. In this case, the guide wire is pushed forward when the device is deflated without it being anchored, with the trailing inflation tube providing the small amount of resistance to hold the device in place while the guide wire is being advanced. Once the guide wire has been advanced a small distance, it is held in place externally, while the device crawls along it until has covered that small distance, at which point it releases itself from the guide wire, enabling the guide wire to be advanced another small distance, the whole process repeating itself until the target is reached.
(57) It is appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and sub combinations of various features described hereinabove as well as variations and modifications thereto which would occur to a person of skill in the art upon reading the above description and which are not in the prior art.
