Abstract:
A flexible guidewire comprising a hollow tube, having a proximal section and a distal section, the distal section having a distal tip, the outer diameter of the distal section gradually decreasing toward the distal tip, the outer diameter of the distal tip being larger than the smallest outer diameter of the distal section, the flexible guidewire further comprising a plug coupled with the distal tip of the hollow tube for creating a non-traumatic tip, and the flexible guidewire further comprising a tubular spring, being place around the distal section of the hollow tube for maintaining the outer diameter of the hollow tube over the length thereof and for supporting compressive loads.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/357,971 (“the 971 application”), filed Jan. 22, 2009, now pending, which claims the benefit of U.S. provisional patent application No. 61/028,665 (“the &#39;665 application”), filed Feb. 14, 2008, and of U.S. provisional patent application No. 61/023,007 (“the &#39;007 application”), filed Jan. 23, 2008. The &#39;971 application, the &#39;665 application, and the &#39;007 application are hereby incorporated by reference in their entireties as though fully set forth herein. 
     
    
     BACKGROUND 
       [0002]    a. Field of the Disclosed Technique 
         [0003]    The disclosed technique relates to guidewires, in general, and to methods and systems for including electronic components in guidewires and for making guidewires more flexible, in particular. 
         [0004]    b. Background of the Disclosed Technique 
         [0005]    Guidewires are employed in noninvasive operations, to enable the physician to navigate to a desired location within the lumen of the body of the patient, and then insert the catheter to the desired location, with the aid of the guidewire. Such guidewires are known in the art. One type of guidewire includes a sensor at the tip thereof, which is connected to an electronic unit, with a pair of wires which pass through a lumen within the guidewire. The guidewire includes a coil in front of the sensor, to enable maneuverability. Another type of guidewire includes a sensor at the tip thereof, which is connected to the electronic unit, with a pair of wires, which pass through the lumen within the guidewire. This guidewire is devoid of a flexible element to provide maneuverability. 
         [0006]    US Patent No. Re. 35,648 issued to Tenerz et al., and entitled “Sensor Guide Construction and Use Thereof,” is directed to a guidewire which includes a thin outer tube, an arched tip, a radiopaque coil, a solid metal wire, a sensor element, and a signal transmitting cable. The radiopaque coil is welded to the arched tip. The solid metal wire is formed like a thin conical tip, and it is located within the arched tip and the radiopaque coil. The solid metal wire successively tapers toward the arched tip. At the point where the solid metal wire joins the radiopaque coil, the thin outer tube commences. The signal transmitting cable extends from the sensor element to an electronic unit, through an air channel within the thin outer tube. 
         [0007]    U.S. Pat. No. 4,873,986 issued to Wallace, and entitled “Disposable Apparatus for Monitoring Intrauterine Pressure and Fetal Heart Rate,” is directed to an apparatus to monitor the fetal condition during labor and childbirth. The apparatus includes a cable, a pressure transducer, a plug, and a pair of wires. The pressure transducer is located within the leading edge of the cable. The plug is located at a proximal end of the cable. The signals from the pressure transducer are conveyed to the plug, by way of the pair of wires, which pass through a vent channel within the cable. 
         [0008]    U.S. Pat. No. 6,428,489 issued to Jacobsen et al and entitled “Guidewire System,” is directed to a catheter guidewire which includes an elongate solid body. Around this elongated solid body about, a catheter guided toward a target location in the vasculature system of a body. The elongate body includes a proximal end and a distal end, with the distal end being curved. Cuts are formed by either saw-cutting, laser cutting or etching at spaced-apart locations along the length of the body thereby increasing the lateral flexibility of the guidewire. Integral beams are also formed within the body to maintain its torsional strength. The relative location and size of cuts and beams may be selectively adjusted thereby determining the direction and degree of flexure, and the change in torsional stiffness relative to flexibility. 
       SUMMARY OF THE PRESENT DISCLOSED TECHNIQUE 
       [0009]    It is an object of the disclosed technique to provide a novel flexible guidewire. 
         [0010]    In accordance with the disclosed technique, there is thus provided a flexible guidewire including a hollow tube, a plug and a tubular spring. The hollow tube has a proximal section and a distal section. The distal section has a distal tip. The outer diameter of the distal section gradually decreases toward the distal tip. The outer diameter of the distal tip is larger than the smallest outer. diameter of the distal section. The spring is place around the distal section of the hollow tube for maintaining the outer diameter of the hollow tube over the length thereof and for supporting compressive loads. The plug is coupled with the distal tip of the hollow tube, for creating a non-traumatic tip. 
         [0011]    In accordance with another aspect of the disclosed technique, there is thus provided a method for forming a flexible guidewire. The method comprises the procedures of reducing the outer diameter of the distal section of a hollow tube and placing a tubular spring over the distal section of the hollow tube. The method further comprises the procedures of enlarging the distal end of the distal tip of the hollow tube, thereby creating a sensor housing, and inserting a plug onto the sensor housing. 
         [0012]    In accordance with a further aspect of the disclosed technique, there is thus provided a flexible guidewire including a grooved corewire, a plug and a tubular spring. The grooved corewire has a proximal section and a distal section. The distal section has a distal tip. The outer diameter of the distal section gradually decreases toward the distal tip. The grooved corewire has a groove engraved along the length thereof. The spring is place around the distal section of the hollow tube for maintaining the outer diameter of the hollow tube over the length thereof and for supporting compressive loads. The plug is coupled with the distal tip of the grooved corewire, for creating a non-traumatic tip. 
         [0013]    In accordance with another aspect of the disclosed technique, there is thus provided a flexible guidewire including a flexible corewire, a sensor core for coupling a sensor therewith and a coupler. The sensor core exhibits a diameter substantially similar to the diameter of the flexible corewire. The sensor covers one portion of said sensor core. The other portion of the sensor core extends from at least one side of the sensor. The coupler exhibits the shape of a hollow tube with a part of the wall of said hollow tube removed along the length of the hollow tube. The inner diameter of the hollow tube is substantially similar to the diameters of the corewire and the sensor core. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The disclosed technique will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which: 
           [0015]      FIG. 1A  is a schematic illustration of a guidewire in a cross-sectional view, constructed and operative in accordance with an embodiment of the disclosed technique; 
           [0016]      FIG. 1B  is a schematic illustration showing the flexibility of a guidewire, constructed and operative in accordance with another embodiment of the disclosed technique; 
           [0017]      FIG. 2  is a schematic illustration of another guidewire, in a cross-sectional view, constructed and operative in accordance with a further embodiment of the disclosed technique; 
           [0018]      FIG. 3A  is a perspective illustration of a guidewire having a tip which exhibits substantially increased flexibility, constructed and operative in accordance with another embodiment of the disclosed technique; 
           [0019]      FIG. 3B  is an orthographic illustration, in top view, of the guidewire of  FIG. 3A , constructed and operative in accordance with a further embodiment of the disclosed technique; 
           [0020]      FIG. 3C  is an orthographic illustration, in front view, of the guidewire of  FIG. 3A , constructed and operative in accordance with another embodiment of the disclosed technique; 
           [0021]      FIG. 4  is a schematic illustration showing the procedures executed in forming the guidewire of  FIG. 3A , constructed and operative in accordance with a further embodiment of the disclosed technique; 
           [0022]      FIG. 5A  is a perspective illustration of another guidewire having a substantially flexible tip, constructed and operative in accordance with another embodiment of the disclosed technique; 
           [0023]      FIG. 5B  is an orthographic illustration, in top view, of the guidewire of  FIG. 5A , constructed and operative in accordance with a further embodiment of the disclosed technique; 
           [0024]      FIG. 5C  is an orthographic illustration, in front view, of the guidewire of  FIG. 5A , also showing cross-sections of the guidewire, constructed and operative in accordance with another embodiment of the disclosed technique; 
           [0025]      FIG. 6  is a schematic illustration showing the procedures executed in forming the guidewire of  FIG. 5A , constructed and operative in accordance with a further embodiment of the disclosed technique; 
           [0026]      FIG. 7  is a schematic illustration of a cross sectional view of a guidewire, constructed and operative in accordance with another embodiment of the disclosed technique; 
           [0027]      FIG. 8A  is a schematic perspective exploded illustrations of a guidewire, constructed and operative in accordance with a further embodiment of the disclosed technique; 
           [0028]      FIG. 8B  is a schematic perspective illustration of a guidewire, constructed and operative in accordance with a further embodiment of the disclosed technique, at an intermediate stage of assembly; 
           [0029]      FIG. 8C  is a schematic perspective illustration of a guidewire, constructed and operative in accordance with a further embodiment of the disclosed technique, at a final stage of assembly; 
           [0030]      FIG. 8D  is a schematic illustration of a cross sectional view of a guidewire, constructed and operative in accordance with another embodiment of the disclosed technique; 
           [0031]      FIG. 9A  is a schematic perspective exploded illustrations of a guidewire constructed and operative in accordance with a further embodiment of the disclosed technique; and 
           [0032]      FIG. 9B  is a schematic perspective illustration of a guidewire constructed and operative in accordance with a further embodiment of the disclosed technique, at a final stage of assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0033]    The disclosed technique overcomes the disadvantages of the prior art by providing a novel guidewire design and forming technique. The novel design enables electronic components, such as sensors and electrical wires, to be placed within the guidewire, in particular in the tip of the guidewire. Such electronic components allow for scalar and vector values to be measured at the guidewire&#39;s tip. The design also increases the flexibility of the guidewire, in particular at its distal end. The novel forming technique enables a guidewire to be formed having a substantially increased level of flexibility over prior art guidewires. Throughout the description, the guidewire of the disclosed technique is described in reference to medical guidewires. It is noted that the terms “position” and “location” are used interchangeably throughout the description and in general refer to the three dimension location of an object in a predefined coordinate system. 
         [0034]    Reference is now made to  FIG. 1A , which is a schematic illustration of a guidewire, in a cross-sectional view, generally referenced  100 , constructed and operative in accordance with an embodiment of the disclosed technique.  FIG. 1A  substantially shows the inside of guidewire  100 . Guidewire  100  includes a hollow tube  105 , a plug  110 , a sensor  112 , a twisted pair of wires  114  and a tubular spring  118 . Guidewire  100  can be coupled with an interconnect  116 . In general, guidewire  100  includes two sections, a distal section  102  and a proximal section  104 . Distal section  102  refers to the distal end of guidewire  100 , the end of guidewire  100  which is distant from interconnect  116 . Proximal section  104  refers to the proximal end of guidewire  100 , the end of guidewire  100  which is nearest to interconnect  116 . In  FIG. 1A , distal section  102  and proximal section  104  are separated by a set of lines  103 . Hollow tube  105  includes a walled section  106  and a hollow section  108 . Hollow section  108  can also be referred to as a cavity or a lumen. Twisted pair of wires  114 , referred to herein as twisted, pair  114 , are coupled with sensor  112  and with interconnect  116 . Plug  110  is coupled with the distal tip of guidewire  100 . As explained in further detail below, tubular spring  118  is placed around a particular section of distal section  102  of guidewire  100 . Sensor  112  and twisted pair of wires  114  are located inside hollow tube  105  in hollow section  108 . 
         [0035]    Sensor  112  is sensor capable of measuring scalar values such as pressure and temperature as well as vector values such as position and orientation of a magnetic field. For example, sensor  112  is a coil sensor capable of measuring the strength and orientation of a magnetic field. In general, micro-coil sensor can have a thickness on the order of a few hundred micrometers, such as 250 μm. Twisted pair  114  includes wires capable of transferring electrical signals from sensor  112  to interconnect  116 . The wires of twisted pair  114  can have a thickness on the order of tens of micrometers, for example, between 10-25 μm. Plug  110  can be made of metal or of a polymer bonded into guidewire  100 . Plug  110  may further be made of bonding material shaped into a hemispherical shape. Plug  110  is coupled to the distal tip of guidewire  100  by gluing, bonding, welding or soldering. Plug  110  can also just be glue. Tubular spring  118  is a tube exhibiting lateral flexibility (i.e., perpendicular to the central axis of the tube). Tubular spring  118  is, for example, a metal (e.g., Stainless Steel, Platinum, Iridium, Nitinol) coil spring a flexible polymer tube or a braided or coiled plastic tube. Tubular spring  118  maintains the outer diameter of guidewire  100  over the length  25  thereof (i.e., typically tubular spring  118  maintains diameter  132 ). Furthermore, tubular spring supports compressive loads and resists buckling of the section  122  without substantially increasing torsional and bending stiffness. Tubular spring  118  can also be made of a radiopaque material, which prevents radiation from passing there through. Interconnect  116  enables guidewire  100 , and in particular twisted pair of wires  114 , to be coupled with other devices, such as a computer, a power source, a device measuring magnetic field strength and orientation and the like. Guidewire  100  may be further covered by a thin elastic polymer layer (not shown) over sections  120  and  122 . This polymer layer is typically a heat shrink tube of a few microns thickness, which provides a slick, smooth and lubricious surface. 
         [0036]    As mentioned above, guidewire  100  can be used to measure various scalar and vector values and in particular scalar and vector values as detected and determined at the distal tip of guidewire  100 . When sensor  112  is a micro-coil sensor, sensor  112  and located in the distal tip of guidewire  100  guidewire  100  can be used to determine the strength and orientation of a magnetic field at the distal tip of guidewire  100 , which in turn can be used to determine the position and orientation of the distal tip of guidewire  100 . For example, if guidewire  100  is used in a medical application, where guidewire  100  is inserted inside a living object, such as a human or an animal, then guidewire  100  can determine the position and orientation of its distal tip based on the measurements of sensor  112 . In general, in such an application a magnetic field is generated in the vicinity of the living object and sensor  112  is capable of measuring the magnetic field strength and orientation. These measurements are provided as electrical signals from sensor  112  to twisted pair  114  which in turn provide the electrical signals to interconnect  116 . Interconnect  116  can be coupled with a computer capable of determining the position and orientation of the micro-coil sensor based on the electrical signals received. Since sensor  112  is located in the distal tip of guidewire  100 , the position and orientation of sensor  112  is substantially the position and orientation of the distal tip of guidewire  100 . 
         [0037]    In position sensing applications involving magnetic fields, magnetic interference, such as induced electrical currents, can cause errors and biases in the electrical signals provided from twisted pair  114  to interconnect  116 . In order to reduce the amount of magnetic interference, the wires located inside hollow section  108  are generally twisted, which reduces the amount of induced electrical current in the wires due to the presence of a magnetic field. Furthermore, tubular spring  118  may be made of a radiopaque material such that it can be seen on an X-ray. If guidewire  100  is used in a medical application where it is inserted inside a living object, and tubular spring  118  is made of a radiopaque material, then, tubular spring  118  will appear on an X-ray of the living object and therefore, distal section  102  of the guidewire will also appear on the X-ray image. This information can be used along with the measurements of sensor  112  to enhance the determination of the position and orientation of the distal tip of guidewire  100 . 
         [0038]    As described in more detail in  FIG. 1B , distal section  102  of guidewire  100  is flexible which provides increased maneuverability to guidewire  100 . Increased maneuverability enables a user of guidewire  100  to more easily maneuver the guidewire when it is inserted into a living object. The flexibility of the distal end of guidewire  100  is achieved by changing the outer diameter of walled section  106  of hollow tube  105  as, further described. In general, to increase the flexibility of hollow tube  105 , it is required to reduce the outer diameter thereof, while maintaining the ability of hollow tube  105  to withstand compressive loads, buckling and kinking Hollow tube  105  is generally made of a metal, such as Stainless Steel or Nitinol. In the embodiment shown in  FIG. 1A , hollow tube  105  is made from a single piece of metal. The fact that hollow tube  105  is made of metal provides twisted pair  114  with shielding from electromagnetic interferences. Thus, twisted pair  114  may be an unshielded twisted pair, thereby reducing the thickness of twisted pair  114  to the order of tens of micrometers. Hollow tube  105  can be defined by the diameter of hollow section  108 , known as the inner diameter, as well by the diameter of walled section  106 , known as the outer diameter. In  FIG. 1A , both the inner and outer diameters of hollow tube  105  are measured from a centerline  150 . The inner diameter, as shown by an arrow  134 , is substantially on the order of hundreds of micrometers, such as 100 μm. In cardio-logical applications, the inner diameter, shown by an arrow  134 , is substantially on the order of tens of micrometers. As can be seen in  FIG. 1A , the inner diameter of hollow tube  105  does not change along the length of guidewire  100 . The outer diameter, as can be seen in  FIG. 1A , changes along the length of guidewire  100 , as shown by an arrow  132 , an arrow  136  and an arrow  138 . Hollow tube  105  can also be described in terms of the thickness of walled section  106 . For example, as the outer diameter of hollow tube  105  reduces, the thickness of walled section  106  also reduces, as shown by an arrow  140 , an arrow  142  and an arrow  144 . The outer diameter shown by arrow  132  represents the original diameter of hollow tube  105 , which is substantially on the order of hundreds of micrometers, such as 350 μm. In general, the outer diameter of distal section  102  of guidewire  100  is reduced, in a step-like, gradual manner, using various techniques such as grinding and drawing. 
         [0039]    As can be seen in  FIG. 1A , a first section  130  represents the shape of hollow tube  105  over a majority of the length of guidewire  100 . Recall that lines  103  represent a break between the distal and proximal sections of guidewire  100  wherein the dimensions of the guidewire do not change and remain fixed. Guidewire  100  can measure, for example up to  200  centimeters. Section  130  can measure, for example, up to  160  centimeters. Adjacent to first section  130  is a first transition section  128 , where the outer diameter of walled section  106  is gradually tapered until a first predetermined reduced outer diameter, such as the outer diameter defined by arrow  136 . Adjacent to first transition section  128  is a second section  126 , where the dimensions of the guidewire do not change and remain fixed. Adjacent to second section  126  is a second transition section  124 , where the outer diameter of walled section  106  is gradually tapered until a second predetermined reduced outer diameter, such as the outer diameter defined by arrow  138 . Adjacent to second transition section  124  is a third section, which is subdivided into a floppy section  122  and a sensor housing section  120 . This third section is characterized in that the thickness of walled section  106  does not change and remains fixed as can be seen from arrow  144  and an arrow  146 , both of which are the same size. In general, the length of the distal section, over which the diameter of the guidewire is reduced (i.e., sections  120 ,  122 ,  124 ,  126  and  128 ) is between 20-40 centimeters. 
         [0040]    In general, the thickness of walled section  106  in the third section is substantially on the order of tens of micrometers, such as 25 μm, meaning that the outer diameter in floppy section  122 , as shown by an arrow  138 , is substantially on the order of hundreds of micrometers, such as 125 μm. At an outer diameter of hundreds of micrometers, floppy section  122  and sensor housing section  120  of guidewire  100  have increased flexibility and maneuverability. In general, floppy section  122  can typically measure between 40 mm to 300 mm. As floppy section  122  is flexible and not rigid, tubular spring  118  is placed around this section to strengthen the distal tip of guidewire  100  while at the same time not reducing its flexibility. Sensor housing section  120 , which initially had an inner diameter similar to the inner diameter of floppy section  122 , as shown by arrow  134 , is enlarged to an inner diameter as shown by an arrow  148  such that sensor  112  can be inserted into sensor housing section  120 . When sensor  112  is a micro-coil sensor, the thickness of sensor  112  may be on the order of hundreds of micrometers, such as 250 μm, meaning that the inner diameter of the distal tip of guidewire  100 , in this example, is substantially doubled, from approximately 100 μm to 200 μm. The outer diameter of sensor housing section  120  can be increased by drawing the distal tip of guidewire  100  over a mandrel. In general, sensor housing section  120  can typically measure between 1 mrn and 5 mm. It is noted that the dimensions of the general configuration, as shown in  FIG. 1A , can be changed and varied so as to provide increased flexibility, pushability, torque response and tactile feel. For example, more transitions sections or fewer transition sections could have been present in guidewire  100 . The number of transition sections, as well as their respective lengths can be determined and altered by one skilled in the art according to the needs of a particular application, user or both. Alternatively, the outer diameter of guidewire  100  may decrease continuously, either linearly or according to a determined function (e.g., the outer diameter may decrease exponentially). 
         [0041]    Reference is now made to  FIG. 1B , which is a schematic illustration showing the flexibility of a guidewire, generally referenced  170 , constructed and operative in accordance with another embodiment of the disclosed technique. Guidewire  170  is substantially similar to guidewire  100  ( FIG. 1A ). Guidewire  170  is constructed from a hollow tube  172 . As in  FIG. 1A , the distal and proximal sections of guidewire  170  are separated by a set of lines  173 . As in  FIG. 1A , hollow tube  172  is characterized by an outer diameter and an inner diameter, whereby the outer diameter of the hollow tube is reduced at the distal end of the guidewire. Guidewire  170  includes a first section  174 , which represents the shape of hollow tube  172  over a majority of the length of guidewire  170 . In first section  174 , the dimensions of the guidewire do not change and remain fixed. Adjacent to first section  174  is a first transition section  176 , where the outer diameter of hollow tube  172  is gradually tapered until a first predetermined reduced outer diameter. Adjacent to first transition section  176  is a second section  178 , where the dimensions of the guidewire do not change and remain fixed. Adjacent to second section  178  is a second transition section  180 , where the outer diameter of hollow tube  172  is gradually tapered until a second predetermined reduced outer diameter. Adjacent to second transition section  172  is a third section, which is subdivided into a floppy section  182 A and a sensor housing section  184 A. This third section is characterized in that the thickness of the walled section of hollow tube  172  (not shown) does not change and remains fixed. 
         [0042]    In  FIG. 1B , a tubular spring  186 A is placed around floppy section  182 A in order to strengthen the third section while also maintaining the flexibility of this section. Two additional positions of the floppy section and the sensor housing section of guidewire  170  are shown using broken lines, demonstrating the flexible nature of the third section. In a first additional position, shown by a floppy section  182 B, a sensor housing section  184 B and a tubular spring  186 B, the distal end of guidewire  170  is displaced by an amount shown as an arrow  188 A. In a second additional position, shown by a floppy section  182 C, a sensor housing section  184 C and a tubular spring  186 C, the distal end of guidewire  170  is displaced by an amount shown as an arrow  188 B. Due to the reduced outer diameter of the floppy section and the sensor housing section of guidewire  170 , the two additional positions shown in  FIG. 1B  are possible. Also, because the tubular spring applies a restoring force when the distal end of guidewire  170  is in either of the two additional positions shown in  FIG. 1B , the distal end of guidewire  170  maintains a certain amount of rigidness as the tubular spring is always trying to maintain the floppy section in the position of floppy section  182 A. 
         [0043]    Reference is now made to  FIG. 2 , which is a schematic illustration of another guidewire, in a cross-sectional view, generally referenced  220 , constructed and operative in accordance with a further embodiment of the disclosed technique. Guidewire  220  is substantially similar to guidewire  100  ( FIG. 1A ) and includes a distal section  226 , a proximal section  228  and a set of lines  230  separating the two. Unlike the embodiment of the guidewire shown in  FIG. 1A , guidewire  220  is constructed from two hollow tubes of different inner and outer diameters, a thicker hollow tube  224  and a thinner hollow tube  222 . Thicker hollow tube  224  and thinner hollow tube  222  can both be hypotubes. In general, thinner hollow tube  222  is shorter in length than thicker hollow tube  224 . For example, thinner hollow tube  222  may typically measure between  5  and  30  centimeters, whereas thicker hollow tube  224  may typically measure between  160  and  170  centimeters. As in  FIG. 1A , guidewire  220  includes a tubular spring  238  and a plug  252 , which is placed over the distal end of guidewire  220  in the direction of an arrow  254 . Guidewire  220  has a lumen  236 , where a sensor (not shown) can be placed, and a hollow section  232 , where a twisted pair of wires (not shown) can be placed, which are coupled with the sensor. Guidewire  220  can also be coupled with an interconnect (not shown). Similar to guidewire  100  ( FIG. 1A ), guidewire  220  may be also be covered by a thin elastic polymer layer (not shown) over sections  240  and  242 . 
         [0044]    As in  FIG. 1A , guidewire  220  has an initial outer diameter which is tapered in distal section  226  to enable the distal section of guidewire  220  to have increased flexibility. As shown in  FIG. 2 , guidewire  220  includes a first section  250 , which represents the shape of thicker hollow tube  224  over a majority of the length of guidewire  220 . In first section  250 , the dimensions of the guidewire do not change and remain fixed. Adjacent to first section  250  is a first transition section  248 , where the outer diameter of thicker hollow tube  224  is gradually tapered until a first predetermined reduced outer diameter. Adjacent to first transition section  248  and partially overlapping is a second section  246 , where the dimensions of the guidewire do not change and remain fixed. The second section represents the initial shape of thinner hollow tube  222 . Adjacent to second section  246  is a second transition section  244 , where the outer diameter of thinner hollow tube  222  is gradually tapered until a second predetermined reduced outer diameter. Adjacent to second transition section  244  is a third section, which is subdivided into a floppy section  242  and a sensor housing section  240 . This third section is characterized in that the thickness of the walled section of thinner hollow tube  222  does not change and remains fixed as shown by arrows  260  and  262 . 
         [0045]    In general, the outer and inner diameters of both thicker hollow tube  224  and thinner hollow tube  222  are on the order of hundreds of micrometers. For example, the inner and outer diameters of thicker hollow tube  224  may respectfully be 180 μm and 350 μm, whereas the inner and outer diameters of thinner hollow tube  222  may respectfully be 100 μm and 180 μm. The inner diameter of thinner hollow tube  222  is shown as an arrow  259 . In general, the outer diameter of the thinner hollow tube is selected such that it is substantially similar to the inner diameter of the thicker hollow tube. In the embodiment shown in  FIG. 2 , thicker hollow tube  224  is coupled with thinner hollow tube  222  by either welding, bonding or gluing. As shown in  FIG. 2 , the area which is coupled between the two hollow tubes is where first transition section  248  and second section  246  overlap. 
         [0046]    In this embodiment, the initial thickness of the walled section of each hollow tube, as shown by an arrow  256  and an arrow  258 , is reduced and tapered by reducing the outer diameter of the walled section of each hollow tube. As mentioned above, the outer diameter can be reduced by grinding or drawing. In one embodiment, the outer diameters of thicker hollow tube  224  and thinner hollow tube  222  are both reduced after they have been coupled together. In another embodiment, the outer diameters of thicker hollow tube  224  and thinner hollow tube  222  are both reduced before they are coupled together. In a further embodiment, the outer diameters of thicker hollow tube  224  and thinner hollow tube  222  are both reduced before they are coupled together and after they are coupled together. It is noted that in this embodiment, sensor housing section  240  can be formed (i.e., the distal end of guidewire  220  can be enlarged) before tubular spring  238  is placed on floppy section  242 . This can be achieved by first enlarging the distal end of guidewire  220  before thicker hollow tube  224  and thinner hollow tube  222  are coupled together. Once the distal end has been enlarged, tubular spring  238  can be placed over floppy section  242  and then thicker hollow tube  224  and thinner hollow tube  222  can be coupled together, thereby trapping tubular spring  238  between the larger outer diameters of sensor housing section  240  and first section  250 . In another embodiment, the two hollow tubes can first be coupled together, then tubular spring  238  can be placed over floppy section  242  and finally, sensor housing section  240  can be enlarged to fit the sensor. As mentioned above in conjunction with  FIG. 1A , the dimensions of the general configuration, as shown in  FIG. 2 , can be changed and varied so as to provide increased flexibility, pushability, torque response and tactile feel. For example, more transitions sections could have been present in guidewire  220 . The number of transition sections, as well as their respective length can be determined and altered by one skilled in the art according to the needs of a particular application, user or both. 
         [0047]    Reference is now made to  FIG. 3A , which is a perspective illustration of a guidewire having a tip which exhibits substantially increased flexibility, generally referenced  280 , constructed and operative in accordance with another embodiment of the disclosed technique. In general, the flexibility of the hollow tubes illustrated in  FIGS. 1A and 2  are determined by the thickness of the walled section of each guidewire near the distal end, as shown by arrows  144  ( FIG. 1A) and 146  ( FIG. 1A ) for guidewire  100  ( FIG. 1A ), and as shown by arrows  260  ( FIGS. 2) and 262  ( FIG. 2 ) for guidewire  220  ( FIG. 2 ). The flexibility is also determined by the inner diameter of each guidewire, as shown by arrow  134  ( FIG. 1A ) for guidewire  100  and by arrow  259  for guidewire  220 . By reducing the thickness of the walled sections of these guidewires near, the distal end and by reducing the inner diameter, the flexibility of these guidewires can be increased. This flexibility is limited by two factors, the first being the minimal size of the inner diameter of each guidewire such that a twisted pair of wires can be threaded through. The second is the minimal thickness of the walled section of each guidewire such that the general form of the guidewire is maintained and that the walled section of each guidewire does not break or tear during use. In  FIG. 3A , the distal end of guidewire  280  is formed, according to the disclosed technique, in a manner such that it exhibits increased flexibility over the flexibility of guidewires  100  and  220 . Thus the distal tip of guidewire  280  exhibits substantial maneuverability. 
         [0048]    Guidewire  280  is substantially similar to guidewire  100 . Guidewire  280  has a distal section  284  and a proximal section  286 . Guidewire  280  is constructed from a hollow tube  282 . Guidewire  280  can be coupled with an interconnect (not shown). Also, guidewire  280  has a sensor (not shown) and a twisted pair of wires (not shown) threaded through the lumen (not shown) of hollow tube  282 . The outer diameter of guidewire  280  is tapered in distal section  284  and the distal end of guidewire  280  is enlarged to enable the sensor to be placed therein. As in guidewire  100 , the inner diameter of hollow tube  282  remains constant along the length of the guidewire. Guidewire  280  has a first section  288 , where the outer diameter of the guidewire remains fixed and constant along a majority of the length of the guidewire. Adjacent to first section  288  is a floppy section  290 , where the outer diameter of guidewire  280  is reduced to a predetermined reduced outer diameter and then kept constant at the predetermined reduced outer diameter. A tubular spring (not shown) can be placed around floppy section  290 . Adjacent to floppy section  290  is a sensor housing section  292  where the sensor is placed. As can be seen in  FIG. 3A , sensor housing section  292  is enlarged to enable the sensor to fit in. Similar to guidewire  100  ( FIG. 1A ), guidewire  280  may be also be covered by a thin elastic polymer layer (not shown) over sections  290  and  292 . 
         [0049]    In guidewire  280 , a part of the walled section of hollow tube  282 , in floppy section  290 , is completely removed, thereby exposing the lumen of hollow tube  282 . This is illustrated in  FIG. 3A  as an opening  296  and an opening  298 . Openings  296  and  298  are located at opposite sides of hollow tube  282 , thereby increasing the flexibility of guidewire  280  in a horizontal plane, as shown by an arrow  299 . An area  297  represents the walled section of hollow tube  282  which is visible once a part of the walled section in floppy section  290  has been removed. The walled section removed in floppy section  290  can be removed by either grinding or cutting by laser. Besides removing a part of the walled section in floppy section  290 , hollow tube  282  is split in two in a vertical plane, as shown by an arrow  295 , from the beginning of sensor housing section  292  to substantially the end of floppy section  290 . This splitting generates two distal ends (i.e., two prongs) in distal section  284 , a distal end  300 A and a distal end  300 B. This is more clearly illustrated in  FIG. 3B . It is noted that other embodiments of the construction of distal section  284  are possible. For example, instead of removing the upper and lower sides of the walled section of floppy section  290 , the lateral sides of the walled section of floppy section  290  can be removed. In this embodiment, the sensor housing section and the floppy section would be split into two in a horizontal plane. 
         [0050]    Once distal section  284  has been constructed as shown in  FIG. 3A , the sensor is placed inside an opening  294 , and the twisted wire pair, coupled with the sensor, are threaded through the lumen of hollow tube  282 . Openings  296  and  298  may be filled with a glue to prevent the twisted pair of wires from moving and being exposed. However, when the glue affects the flexibility of distal section  284 , glue may be applied only at selected locations along distal section  284  to prevent the twisted pair of wires from moving. Also distal ends  300 A and  300 B can be glued to the sensor to keep the sensor in place. A plug (not shown) can be placed over opening  294  to seal the sensor in. Similar to guidewire  100  ( FIG. 1A ), guidewire  320  may be also be covered by a thin elastic polymer layer (not shown) over sections  290  and  292 . 
         [0051]    Reference is now made to  FIG. 3B , which is an orthographic illustration, in top view, of the guidewire of  FIG. 3A , generally referenced  320 , constructed and operative in accordance with a further embodiment of the disclosed technique. As can be seen in  FIG. 3B , guidewire  320  is constructed from hollow tube  322 , which is substantially similar to hollow tube  282  ( FIG. 3A ). Guidewire  320  has a proximal section  324  and a distal section  326  as well as a first section  332 , a floppy section  330  and a sensor housing section  328 . First section  332 , floppy section  330  and sensor housing section  328  are respectively substantially similar to first section  288  ( FIG. 3A ), floppy section  290  ( FIG. 3A ) and sensor housing section  292  ( FIG. 3A ). As can be seen from the top view of  FIG. 3B , sensor housing section  328  and floppy section  330  are split into two distal ends, a distal end  336 A and a distal end  336 B. A hollow  334  is where a sensor (not shown) is placed, in between distal end  336 A and  336 B. 
         [0052]    Reference is now made to  FIG. 3C , which is an orthographic illustration, in front view, of the guidewire of  FIG. 3A , also showing cross-sections of the guidewire, generally referenced  350 , constructed and operative in accordance with another embodiment of the disclosed technique. As can be seen in  FIG. 3C , guidewire  350  is substantially similar to guidewire  280 . Guidewire  350  has a proximal section  354  and a distal section  356  as well as a first section  366 , a first transition section  364 , a floppy section  362 , a second transition section  360  and a sensor housing section  358 . First section  366 , floppy section  362  and sensor housing section  358  are respectively substantially similar to first section  288  ( FIG. 3A ), floppy section  290  ( FIG. 3A ) and sensor housing section  292  ( FIG. 3A ). A first transition section and a second transition section are shown in both  FIGS. 3A and 3B  but are not specifically numbered. 
         [0053]    In  FIG. 3C , dash-dot lines  368   1 ,  368   2 ,  368   3 ,  368   4  and  368   5  represent cut-away cross-sections of guidewire  350 . In first section  366 , a cross-section  370  shows that the hollow tube forming guidewire  350  has an initial outer diameter and is completely closed. In first transition section  364 , the cross-sections  372 A and  372 B show that the outer diameter has been reduced and that the hollow tube of the guidewire is not completely closed and is split into two sections. As can be seen, the outer diameter of cross-sections  372 A and  372 B is smaller than the outer diameter of cross-section  370 . It should be noted that in first transition section  364 , a minority amount of the walled section of the hollow tube has been completely removed, as this represents the beginning of the area of guidewire  350  where the walled section of the hollow tube is removed. In floppy section  362 , the cross-sections  374 A and  374 B show that the outer diameter has been further reduced from that of cross-sections  372 A and  372 B, and that the majority of the walled section of the hollow tube of the guidewire has been completely removed. In second transition section  360 , the cross-sections  376 A and  376 B show that the outer diameter now remains constant, as the outer diameter of these cross-sections is substantially similar to the outer diameter as shown in cross-sections  374 A and  374 B. These cross-sections also show that only a minority of the walled section of the hollow tube of the guidewire has been completely removed, as this represents the end of the area of guidewire  350  where the walled section of the hollow tube is removed. In sensor housing section  358 , the cross-sections  378 A and  378 B show that the outer diameter is still constant, as the outer diameter of these cross-sections is substantially similar to the outer diameter as shown in cross-sections  374 A,  374 B,  376 A and  376 B. Also, these cross-sections show that the hollow tube is cut in a vertical plane and split into two sections which are not coupled (i.e., two prongs). 
         [0054]    Reference is now made to  FIG. 4 , which is a schematic illustration showing the procedures executed in forming the guidewire of  FIG. 3A , generally referenced  400 , constructed and operative in accordance with a further embodiment of the disclosed technique. In a first procedure  402 , a hollow tube  410  having a fixed inner and outer diameter is selected. In a second procedure  404 , the outer diameter of a distal section  414  of a hollow tube  412  is reduced in a step-like, gradual manner. The outer diameter of a proximal section  416  of hollow tube  412  remains constant. As mentioned above, the outer diameter can be reduced by grinding or by drawing. In procedure  404 , a sub-section  415  of distal section  414  may be further grounded, or cut by a laser, to completely remove a part of the walled section of hollow tube  412  in sub-section  415 , as shown as openings  296  and  298  (both in  FIG. 3A ) in  FIG. 3A . Also, in procedure  404 , distal section  414  is cut all the way through in a vertical plane, thereby generating two distal ends (not shown). 
         [0055]    In a third procedure  406 , once the outer diameter of a distal section  420  has been reduced and distal section  420  of a hollow tube  418  has been split into two, a tubular spring  422 A such as a coil spring is placed over distal section  420  in the direction of an arrow  424 . The tubular spring is placed over distal section  420  until it is in the location of a tubular spring  422 B. In a fourth procedure  408 , the distal end of a hollow tube  426  is enlarged, for example, by of drawing or pulling hollow tube  426  over a mandrel, or stamping the tip over a mandrel between two die sections thereby generating a sensor housing section  428 . Section  428  may further be reinforced by a small section of thin tube placed there over there by holding the split section. A tubular spring  434  is essentially trapped in a floppy section  430 , as the diameters of a first section  432  and sensor housing section  428  are larger than the diameter of tubular spring  434 . The diameter of sensor housing section  428 , as shown by an arrow which represents the full diameter of sensor housing section  428  and not the inner or outer diameter of that section, is large enough that a tubular spring (not shown) can be inserted. In a fifth procedure  409 , once the general configuration of the guidewire has been prepared, a sensor coupled with a twisted pair of wires  438 , referred herein as twisted pair  438 , are threaded into the guidewire, in the direction of an arrow  446 , through a sensor housing section  442 . It is noted that twisted pair  438  may be long, as represented by set of lines  440 . Once sensor  436  and twisted pair  438  are threaded through the guidewire, a plug  444  is inserted over the opening of sensor housing section  442  in the direction of an arrow  448 . As mentioned above, a sensor  436  may be glued or bonded to the inner sides of sensor housing section  442 . Also, the floppy section (not shown) of the guidewire may be covered with a glue to cover any section of twisted pair of wires  438  which are exposed. Twisted pair  438  can then be coupled with an interconnect, thereby generating a finished, functional guidewire, substantially similar in configuration to guidewire  280  ( FIG. 3A ) and in functionality to guidewire  100  ( FIG. 1A ). Additionally, an elastic polymer layer may be applied to the distal end of the guidewire. This elastic polymer layer is typically a heat shrink tube having a thickness in the order of a few microns, which provides a slick, smooth, lubricious surface. 
         [0056]    Reference is now made to  FIG. 5A , which is a perspective illustration of another guidewire having a substantially flexible tip, generally referenced  470 , constructed and operative in accordance with another embodiment of the disclosed technique. In  FIG. 5A , the distal end of guidewire  470  is formed, according to the disclosed technique, in a manner such that it exhibits increased flexibility over the flexibility of guidewires  100  ( FIG. 1A) and 220  ( FIG. 2 ). Thus, the distal tip of guidewire  470  exhibits substantial flexibility, similar to the flexibility of guidewire  280  ( FIG. 3A ). Guidewire  470  is substantially similar to guidewire  100 . Guidewire  470  has a distal section  474  and a proximal section  476 . Guidewire  470  is constructed from a hollow tube  472 . Guidewire  470  can be coupled with an interconnect (not shown). Also, guidewire  470  has a sensor (not shown) and a twisted pair of wires (not shown) threaded through the lumen (not shown) of hollow tube  472 . The outer diameter of guidewire  470  is tapered in distal section  474  and the distal end of guidewire  470  is enlarged to enable the sensor to be placed therein. As in guidewire  100 , the inner diameter of hollow tube  472  remains constant along the length of the guidewire. Guidewire  470  has a first section  478 , where the outer diameter of the guidewire remains fixed and constant along a majority of the length of the guidewire. Adjacent to first section  478  is a floppy section  480 , where the outer diameter of guidewire  470  is reduced to a predetermined reduced outer diameter and then kept constant at the predetermined reduced outer diameter. A tubular spring (not shown) can be placed around floppy section  480 . Adjacent to floppy section  480  is a sensor housing section  482  where the sensor is placed. As can be seen in  FIG. 5A , sensor housing section  482  is enlarged to enable the sensor to fit in. Similar to guidewire  100  ( FIG. 1A ), guidewire  470  may be also be covered by a thin elastic polymer layer (not shown) over sections  488  and  488 . 
         [0057]    In guidewire  470 , a part of the walled section of hollow tube  472 , in floppy section  480 , is completely removed, thereby exposing the lumen of hollow tube  472 . This is illustrated in  FIG. 5A  as an opening  486 . As opposed to the configuration of guidewire  280  ( FIG. 3A ), guidewire  470  has an opening on only one side of hollow tube  472 . Opening  486  is located on the upper side of hollow tube  472 , thereby giving guidewire  470  an increase in flexibility in a vertical plane, as shown by an arrow  483 . An area  487  represents the walled section of hollow tube  472  which is visible once a part of the walled section in floppy section  480  has been removed. The walled section removed in floppy section  480  can be removed by either grinding or cutting by laser. Unlike the configuration in  FIG. 3A , floppy section  480  and sensor housing section  482  are not split into two separate ends. It is noted that other embodiments of the construction of distal section  474  are possible. For example, instead of removing the upper side of the walled section of floppy section  480 , the lateral side or the lower side of the walled section of floppy section  480  can be removed. Once distal section  474  has been constructed as shown in  FIG. 5A , the sensor is placed inside an opening  484 , and the twisted pair of wires coupled with the sensor are threaded through the lumen of hollow tube  472 . Opening  486  can be filled with a glue to prevent the twisted pair of wires from being exposed. A plug (not shown) can be placed over opening  484  to seal in the sensor. 
         [0058]    Reference is now made to  FIG. 5B , which is an orthographic illustration, in top view, of the guidewire of  FIG. 5A , generally referenced  500 , constructed and operative in accordance with a further embodiment of the disclosed technique. As can be seen in  FIG. 5B , guidewire  500  is constructed from hollow tube  502 , which is substantially similar to hollow tube  472  ( FIG. 5A ). Guidewire  500  has a proximal section  504  and a distal section  506  as well as a first section  512 , a floppy section  510  and a sensor housing section  508 . First section  512 , floppy section  510  and sensor housing section  508  are respectively substantially similar to first section  478  ( FIG. 5A ), floppy section  480  ( FIG. 5A ) and sensor housing section  482  ( FIG. 5A ). As can be seen from the top view of  FIG. 5B , a part of the walled section of floppy section  510  is completely removed. Unlike the guidewire shown in  FIG. 3B , sensor housing section  508  is not split into two distal ends. Similar to guidewire  100  ( FIG. 1A ), guidewire  470  may be also be covered by a thin elastic polymer layer (not shown) over sections  508  and  510 . 
         [0059]    Reference is now made to  FIG. 5C , which is an orthographic illustration, in front view, of the guidewire of  FIG. 5A , also showing cross-sections of the guidewire, generally referenced  530 , constructed and operative in accordance with another embodiment of the disclosed technique. As can be seen in  FIG. 5C , guidewire  530  is substantially similar to guidewire  470 . Guidewire  530  has a proximal section  534  and a distal section  532  as well as a first section  546 , a first transition section  544 , a floppy section  542 , a second transition section  540  and a sensor housing section  538 . First section  546 , floppy section  542  and sensor housing section  538  are respectively substantially similar to first section  478  ( FIG. 5A ), floppy section  480  ( FIG. 5A ) and sensor housing section  482  ( FIG. 5A ). A first transition section and a second transition section are shown in both  FIGS. 5A and 5B  but are not specifically numbered. 
         [0060]    In  FIG. 5C , dash-dot lines  548   1 ,  548   2 ,  548   3 ,  548   4  and  548   5  represent cut-away cross-sections of guidewire  530 . In first section  546 , a cross-section  550  shows that the hollow tube forming guidewire  530  has an initial outer diameter and is completely closed. In first transition section  544 , the cross-section  552  shows that the outer diameter has been reduced and that the hollow tube of the guidewire is not completely closed. As can be seen, the outer diameter of cross-section  552  is smaller than the outer diameter of cross-section  550 . It should be noted that in first transition section  544 , a minority amount of the walled section of the hollow tube has been completely removed, as this represents the beginning of the area of guidewire  530  where the walled section of the hollow tube is removed. In floppy section  542 , the cross-section  554  shows that the outer diameter has been further reduced from that of cross-section  552 , and that the majority of the walled section of the hollow tube of the guidewire has been completely removed thereby creating a single prong. In second transition section  540 , the cross-section  556  shows that the outer diameter now remains constant, as the outer diameter of this cross-section is substantially similar to the outer diameter as shown in cross-section  554 . This cross-section also show that only a minority of the walled section of the hollow tube of the guidewire has been completely removed, as this represents the end of the area of guidewire  530  where the walled section of the hollow tube is removed. In sensor housing section  538 , the cross-section  558  shows that the outer diameter is still constant, as the outer diameter of this cross-section is substantially similar to the outer diameter as shown in cross-sections  556  and  554 . Also, this cross-section shows that the hollow tube is completed, as in cross-section  550 . 
         [0061]    Reference is now made to  FIG. 6 , which is a schematic illustration showing the procedures executed in forming the guidewire of  FIG. 5A , generally referenced  580 , constructed and operative in accordance with a further embodiment of the disclosed technique. In a first procedure  582 , a hollow tube  594  having a fixed inner and outer diameter is selected. In a second procedure  584 , the outer diameter of a distal section  598  of a hollow tube  596  is reduced in a step-like, gradual manner. The outer diameter of a proximal section  600  of hollow tube  596  remains constant. As mentioned above, the outer diameter can be reduced by grinding or by drawing. In a third procedure  586 , a sub-section  606  of the distal section may be further grounded, or cut by a laser, to completely remove a part of the walled section of a hollow tube  602  in sub-section  606 , as shown as opening  486  ( FIG. 5A ) in  FIG. 5A . The area of the distal section cut out to generate sub-section  606  is shown as a dotted line in procedure  586 . As can be seen, the diameter of sub-section  606  is smaller than the diameter of another sub-section  604 . 
         [0062]    In a fourth procedure  588 , once the outer diameter of a distal section  612  has been reduced, a tubular spring  614 A is placed over distal section  612  in the direction of an arrow  616 . The tubular spring is placed over distal section  612  until it is in the location of a tubular spring  614 B. In a fifth procedure  590 , the distal end of a hollow tube  618 , is enlarged, thereby generating a sensor housing section  620 . A tubular spring  626  is essentially trapped in a floppy section  622 , as the diameters of a first section  624  and sensor housing section  620  are larger than the diameter of tubular spring  626 . The diameter of sensor housing section  620 , as shown by an arrow  628 , which represents the full diameter of sensor housing section  620  and not the inner or outer diameter of that section, is large enough that a tubular spring (not shown) can be inserted. In a sixth procedure  592 , once the general configuration of the guidewire has been prepared, a sensor  630 , coupled with a twisted pair of wires  632 , referred to herein as twisted pair  632 , are threaded into the guidewire, in the direction of an arrow  640 , through a sensor housing section  636 . It is noted that twisted pair  632  may be long, as represented by set of lines  634 . Once sensor  630  and twisted pair  632  are threaded through the guidewire, a plug  638  is inserted over the opening of sensor housing section  636  in the direction of an arrow  642 . As mentioned above, the floppy section (not shown) of the guidewire may be covered with a glue to cover any section of twisted pair of wires  632  which are exposed. Twisted pair of wires  632  can then be coupled with an interconnect, thereby generating a finished, functional guidewire, substantially similar in configuration to guidewire  470 , ( FIG. 5A ) and in functionality to guidewire  100  ( FIG. 1A ). Additionally, an elastic polymer layer may be applied to the distal end of the guidewire. This elastic polymer layer is typically a heat shrink tube having a thickness in the order of a few microns, which provides a slick, smooth, lubricious surface. 
         [0063]    Reference is now made to  FIG. 7 , which is a schematic illustration of a cross sectional view of a guidewire generally referenced  660 , constructed and operative in accordance with another embodiment of the disclosed technique. Guidewire  660  includes a grooved corewire  662 , a plug  664 , a sensor  666 , a twisted pair of wires  668 , referred to herein as twisted pair  668 , a tubular proximal end  670  and a tubular spring  672 . Grooved corewire  662  is made of metal (e.g., Stainless Steel, Nitinol). Sensor  666  is sensor capable of measuring scalar values such as pressure and temperature as well as vector values such as position and orientation of a magnetic field. For example, sensor  66  is a coil sensor capable of measuring the strength and orientation of a magnetic field. Guidewire  660  can be coupled with an interconnect  674 . Twisted pair  668  are coupled with sensor  666  and with interconnect  674 . Plug  664  is coupled with the distal tip section  688  of guidewire  660 . Tubular spring  670  is placed around distal sections  688  and  690  of guidewire  660 . Grooved corewire  662  is coupled with tubular proximal end  670  (e.g., by bonding or welding). 
         [0064]    In  FIG. 7 , dash-dot lines  676   1 ,  676   2 ,  676   3 ,  676   4  and  676   5  represent lateral cross-sections of guidewire  660 . Along section  694 , the diameter of grooved corewire  694  remains substantially constant and is in the order of hundreds of micrometers. In first cross-section  678 , the diameter of grooved corewire  662  has an initial outer diameter and is inserted into tubular proximal end  670 . Twisted pair  668  are placed within a groove along grooved corewire  662 . It is noted that although twisted pair  668  is an unshielded twisted pair, tubular spring  672  may provide electrical shielding for twisted pair  668 . In second cross-section  680  the diameter of grooved corewire  662  has an initial outer diameter and twisted pair  668  are placed within a groove along grooved corewire  662 . However, grooved corewire  662  is no longer within tubular proximal end  670 . 
         [0065]    Along section  692  of guidewire  660 , the diameter of grooved corewire  662  is gradually reduced. Furthermore, the shape of the lateral cross-section of grooved corewire  662  gradually changes. In third cross-section  682  the shape of the lateral cross-section of grooved corewire  662  is that of a semi-circle. Furthermore, in third cross-section  682 , the diameter of grooved corewire  662  is smaller than in first and second cross-sections  678  and  680 . Along section  690 , the diameter of grooved corewire  660  is substantially constant, however, this diameter is smaller than the diameter shown in cross-section  682 . In forth cross-section  684  the shape of lateral cross-section of grooved corewire  662  is that of circular segment. Fifth cross-section  686  is a cross section of the distal tip of guidewire  670  (i.e. section  688 ). Along section  188  the residual volume between sensor  666  and tubular spring  672  is filled with a polymer bond  665 , thus securing the sensor in place. In  FIG. 7 , the distal end of guidewire  670  is formed, according to the disclosed technique, in a manner such that it exhibits increased flexibility over the flexibility of guidewires  100  and  220 . Thus the distal tip of guidewire  670  exhibits substantial maneuverability. 
         [0066]    Reference is now made to  FIGS. 8A ,  8 B and  8 C, which are schematic perspective illustration of a guidewire, generally reference  750 , constructed and operative in accordance with a further embodiment of the disclosed technique.  FIG. 8A  a schematic perspective exploded illustrations of the guidewire  750 . Guidewire  750  includes a corewire  752 , a sensor  754 , a sensor core  756  and a coupler  758 . Sensor  754  is coupled with a sensor core  756 . The length of sensor core  756  is larger than the length of sensor  754 . Thus, when sensor  754  is coupled with sensor core  756 , sensor  754  covers only a portion of sensor core  756  such that sensor core  756  extends from one side of sensor  754 . The lengths of sensor  754  and sensor core  756  are on the order of a few millimeters. In  FIGS. 8A ,  8 B and  8 C, sensor  754  is a coil sensor capable of measuring the strength and orientation of a magnetic field. In general, coil sensor can have a thickness on the order of a few hundred micrometers (e.g., 250 μm). Corewire  752  and sensor core  756  exhibit substantially the same diameter (e.g., on the order of hundreds of micrometers). Coupler  758  is a hollow tube with a part of the wall thereof removed along the length of coupler  758 . The inner diameter of coupler  758  is substantially similar to the diameters of corewire  752  and sensor core  756 . 
         [0067]      FIG. 8B  a schematic perspective illustration of the guidewire  750  at an intermediate stage of assembly. In  FIG. 8B , corewire  752  is inserted into one side of coupler  754 . The portion sensor core  756  that is not covered by sensor  754  is inserted into the other side of coupler  754 .  FIG. 8C  a schematic perspective illustration of the guidewire  750  at a final stage of assembly. In  FIG. 8C , a twisted pair of wires  758  are coupled with sensor  754  by a coupling material  760 . Twisted par  758  may be coupled, at the proximal end of the guidewire with an interconnect (not shown) which enables twisted pair  758 , and thus sensor  754 , to be coupled with other devices, such as a computer, a power source, a device measuring magnetic field strength and orientation and the like. Guidewire  750  may be further covered with a thin elastic polymer layer (not shown) over a portion of the length thereof. This polymer layer is typically a heat shrink tube of a few microns thickness, which provides a slick, smooth and lubricious surface. 
         [0068]    A tubular spring (not shown) may be placed around a portion the distal section of guidewire  750 . This tubular spring is a tube exhibiting lateral flexibility (i.e., perpendicular to the central axis of the tube) made of a metal (e.g., Stainless Steel, Platinum, Iridium, Nitinol), a flexible polymer tube or a braided or coiled plastic tube. The tubular spring maintains the outer diameter of guidewire  750  over the length thereof and supports compressive loads and resists buckling of the guidewire without substantially increasing torsional and bending stiffness. 
         [0069]    Reference is now made to  FIG. 8D  which is a schematic illustration of a cross sectional view of a guidewire, generally reference  780 , constructed and operative in accordance with another embodiment of the disclosed technique. Guidewire  780  includes a core wire  786 , a sensor  782 , a sensor core  784 , a coupler  788 , a twisted pair of wires  790  and an interconnect  792 . Sensor  782  is coupled with sensor core  784 . The length of sensor core  784 , delineated by a bracket  794 , is larger than the length of sensor  782 , delineated by a bracket  796 . Thus, when sensor  782  is coupled with sensor core  784 , sensor  754  covers only a portion of sensor core  756 . The portion of sensor core  784  that is not covered sensor  782 , delineated by a bracket  798 , extends from one side of sensor  782 . Corewire  786  and sensor core  784  exhibit substantially the same diameter (e.g., on the order of hundreds of micrometers). Coupler  788  is a hollow tube with a part of the wall thereof removed along the length of coupler  788 . The inner diameter of coupler  788  is substantially similar to the diameters of corewire  786  and sensor core  784 . 
         [0070]    Corewire  786  is inserted into one side of coupler  788 . The portion of sensor core  756  delineated by bracket  798  (i.e., the portion of sensor core  784  that is not covered by sensor  782 ) is inserted into the other side of coupler  788 . Twisted pair of wires  790  are coupled with sensor  782  and with an interconnect  780  which enables twisted pair  790 , and thus sensor  782  to be coupled with other devices. As described above (i.e., in conjunction with  FIG. 8A ,  8 B and  8 C regarding guidewire  750 ), guidewire  780  may be further covered with a thin elastic polymer layer (not shown). Furthermore, a tubular spring (not shown) may be placed around a portion the distal section of guidewire  780 . 
         [0071]    Reference is now made to  FIGS. 9A and 9B , which are schematic perspective illustrations of a guidewire, generally referenced  800 , constructed and operative in accordance with a further embodiment of the disclosed technique.  FIG. 9A  a schematic perspective exploded illustrations of the guidewire  800 . Guidewire  800  includes a first corewire  806 , a second corewire  808 , a sensor  802 , a sensor core  804  a first  5  coupler  810  and a second coupler  812 . Sensor  808  is coupled with a sensor core  804 . The length of sensor core  804  is larger than the length of sensor  802 . Thus, when sensor  802  is coupled with sensor core  804 , sensor  802  covers only a portion of sensor core  756  such that sensor core  804  extends from both sides of sensor  802 . The lengths of sensor  802   10  and sensor core  802  are on the order of a few millimeters. In  FIGS. 9A and 9B  sensor  802  is a coil sensor. However, sensor  802  may be any other type of sensor capable of measuring scalar of vector values. 
         [0072]    First and second corewires  806  and  808  and sensor core  804  exhibit substantially the same diameter (e.g., on the order of hundreds of micrometers). First coupler  810  is a hollow tube with a part of the wall thereof removed along the length of first coupler  810 . Second coupler  812  is a whole hollow tube. The inner diameters of first coupler  810  and second coupler  812  are substantially similar to the diameters of first and second corewires  806  and  808  and the diameter of sensor core  804 . 
         [0073]      FIG. 9B  is a schematic perspective illustration of the guidewire  800  at a final stage of assembly. In  FIG. 9B , a twisted pair of wires  814  are coupled with sensor  802  by a coupling material  816 . First corewire  806  is inserted into one side of first coupler  810 . One side of sensor core  804  is inserted into the other side of first coupler  810 . The other side of sensor core  804  is inserted into one side of second coupler  812 . Second corewire  808  is inserted into the other side of coupler  812 . Thus, sensor  802  is positioned anywhere along the length of guidewire  800 . 
         [0074]    Twisted pair  814  may be coupled, at the proximal end of the guidewire with an interconnect (not shown) which enables twisted pair  814 , and thus sensor  802 , to be coupled with other devices. Similarly to as describe above, guidewire  800  may also be covered with a thin elastic polymer layer (not shown) over a portion of the length thereof. Furthermore, a tubular spring (not shown) may be placed around a portion the distal section of guidewire  800 . 
         [0075]    It will be appreciated by persons skilled in the art that the disclosed technique is not limited to what has been particularly shown and described hereinabove. Rather the scope of the disclosed technique is defined only by the claims, which follow.