Guide wire apparatus with location sensing member

The invention is directed to a guide wire apparatus and a method for detecting the location of a guide wire within the body of a patient. The apparatus includes a guide wire with an internally-housed sensing member. The guide wire assembly is structured to provide the response, maneuverability and tactile feel comparable to conventional guide wire devices. The apparatus is useful in medical treatments and diagnoses such as angioplasty or catheterization procedures, for detecting obstructions within a blood vessel of a patient, and the like.

BACKGROUND OF THE INVENTION 
Catheters are used in conjunction with various procedures to diagnose and 
treat systems of the body, particularly the vascular system. Guide wires 
are used to aid in the insertion of catheters into the body and to 
evaluate the vessel along which the catheter will travel. In general, a 
guide wire is inserted into a body system such as a blood vessel and the 
vessel is probed with the guide wire. The catheter is slipped over the 
guide wire and the guide wire is withdrawn. The catheter is then eased 
through the vessel to the desired location. 
For proper manipulation and control of the guide wire during insertion, the 
operator must be able to tactilely feel the end of the guide wire within 
the vessel. For selectively placing a guide wire in a particular corridor 
of a body system such as a blood vessel, guide wires with flexible end 
portions are employed. J-shaped guide wires are particularly useful for 
maneuvering through curves and junctures of branched portions of a body 
system. 
To position the guide wire at a particular location within the body, it is 
useful to have a means of detecting the location of the tip of the guide 
wire. To this end, guide wires may be marked at intervals along their 
length, wound with a dense metal such as platinum, gold or tungsten to 
provide radiopacity for detection by fluoroscopy, or other such marking 
technique. At present, however, there are no guide wires with 
self-contained sensor components that would permit determination of the 
location of the guide wire tip after it has been inserted into the patient 
without the use of fluoroscopy. 
It would be desirable to have a guide wire with an internally-housed sensor 
for locating the distal section of the guide wire within the body. It 
would also be desirable to design such a guide wire to have the tactile 
response to enable the operator to manipulate and sense the progress of 
the leading end of the guide wire during insertion and placement in the 
body, particularly through branched channels of a the cardiovascular 
system. 
Therefore, an object of the invention is to provide a guide wire apparatus 
with an internally-housed sensor element for detection of the guide wire 
position in the body, a further object is to provide a guide wire with a 
sensor that has the tactile response of a conventional non-sensor guide 
wire. Another object is to provide a method of using the guide wire 
apparatus for detecting obstructions in the body, as for example, the 
vascular system. 
SUMMARY OF THE INVENTION 
These and other goals are achieved by the present invention which is 
directed to a guide wire apparatus which will allow determination of its 
location when it is inserted within the body of a patient, and a method 
for its use. 
The guide wire apparatus of the invention includes a guide wire and sensing 
member for detecting the location of the guide wire distal end position in 
the body. The guide wire has a channel or lumen extending at least part of 
its length, and proximal, center and distal portions. The lumen of the 
guide wire is dimensioned to facilitate insertion and housing of the 
sensing member. 
The sensing member is an elongate metal core with proximal, center and 
distal sections, and a sensor element. Preferably, the metal core is 
tapered at the center section such that the diameter of about the midpoint 
of the center section is narrower than both the distal and proximal 
sections. The sensor element is formed by a current conducting wire 
wrapped around at least part of the metal core distal section. The sensing 
member may be coated with a protective covering material. 
The construction of the guide wire, the sensing member, or both, provides 
the guide wire apparatus with a flexibility factor such that the 
combination of the guide wire and sensing member results in a guide wire 
apparatus with a tactile feel, response and maneuverability within the 
body of a patient, particularly the vascular system, comparable to that of 
conventional guide wires without internally-housed sensors. Preferably, 
the desired tactile response and maneuverability of the guide wire 
apparatus may be provided by constructing the sensing member with a 
tapered area at the center section of the metal core. 
The invention may further include a means for generating and measuring an 
electromagnetic current in the sensor element. The generation is 
accomplished by an external means for producing an electromagnetic energy 
field. The measurement is accomplished by an electronic controller which 
measures the sensor current generated by the field. The apparatus may 
further include means for transmitting current (e.g., alternating current) 
to the electromagnetic energy field generating means. In one embodiment, 
the electronic controller may measure the intensity or amplitude of the 
current in the sensor element. With this embodiment, the location of the 
distal section of the guide wire within the body is determined by 
detecting the strength or magnitude of the sensor current as the external 
means for generating the field is moved over the body (see, for example, 
U.S. Pat. No. 4,173,228 to Van Steenwyk, the disclosure of which is 
incorporated herein by reference). In an alternative embodiment, the 
electronic controller may be designed to detect a phase transition of the 
sensor current as the external means for generating the field is moved 
over the approximate location of the guide wire distal section within the 
body (see, for example, U.S. Pat. No. 4,905,698 to Strohl et al., 
incorporated by reference herein (issued Mar. 6, 1990), subject of a 
Reexamination issued Oct. 1, 1991. 
The invention further includes a method of detecting the location of a 
guide wire and/or an obstruction in the body of a patient using the guide 
wire apparatus described herein. The method includes inserting the guide 
wire apparatus into the body of the patient, advancing the apparatus to 
the desired site within the body, and detecting the location of the sensor 
element of the guide wire apparatus. An obstruction is sensed by the 
tactile response of the guide wire as it is advanced within the body. The 
location of the obstruction is determined by detecting the location of the 
sensor element.

DETAILED DESCRIPTION OF THE INVENTION 
The guide wire apparatus of the invention is made of a guide wire portion, 
and a sensing member for locating the distal end of the guide wire in the 
body. 
The guide wire has proximal, center and distal portions, and a lumen 
extending at least part of the length of the guide wire. Preferably, the 
guide wire is a helically coiled wire with elongate proximal and center 
portions, and a shorter distal portion. In the coiled configuration, the 
guide wire may include an internal safety wire, with a diameter of about 
0.05 to 0.5 mm, preferably about 0.08 to 0.2 mm, extending the length of 
the guide wire and coupled at the distal and proximal ends of the guide 
wire to prevent longitudinal elongation of the coiled wire. 
The distal portion of the guide wire is the leading end of the guide wire 
and is constructed to be easily flexed. The distal portion is the end of 
the guide wire to be inserted into the body of a patient. Consequently, 
when the guide wire apparatus is advanced within the body and encounters a 
peritoneal blood vessel, the tip of the guide wire does not cause puncture 
or perforation of the blood vessel wall. Preferably, the tip of the guide 
wire is rounded. The resiliency of the distal portion also allows the 
guide wire apparatus to be readily maneuvered through curves and branches 
within the body system in which the apparatus is used. The proximal and 
center portions of the guide wire are capable of flexing but are 
comparatively stiffer than the distal portion. To provide these differing 
levels of stiffness, the proximal and center portions of the guide wire 
may be formed, for example, of more tightly coiled wire than the distal 
portion, of wire that has less flexibility than that forming the distal 
portion, or wire that has a larger diameter than that of the distal 
portion. 
Although there is no precise juncture between the proximal and center 
portions, in general, these two portions of the guide wire are 
approximately equal in length. The proximal and center portions have a 
combined length effective for the distal portion of the guide wire to 
reach a desired site within the body system being examined. Preferably, 
the combined length of the proximal and center portions is about 70 to 80 
cm, more preferably about 75 cm. The juncture between the center and 
distal portions of the guide wire may be gradual or abrupt. The distal 
portion of the guide wire has a length effective to facilitate maneuvering 
of the guide wire by the operator through curves and branches of a body 
system. The length of the distal portion of the guide wire is preferably 
about 0.5 to 3 cm long, more preferably about 1 to 2 cm long. 
The distal or leading end of the guide wire may be of any shape suitable to 
allow the guide wire to be inserted into the body of the patient and 
advanced within the body system to the desired site. The distal end may 
have a configuration that is straight, J-shaped, L-shaped, and the like, 
with a J-shaped configuration being preferred. 
The sensing member of the guide wire apparatus includes a sensor element 
formed of a current conducting wire wound around a metal core. The metal 
core has a proximal, central and distal section. In cross-section, the 
metal core may be flat, round, octagonal, or other shape, and may be solid 
or hollow. Preferably, the metal core is a solid wire. 
The metal core of the sensing member may be made of any suitable 
magnetically permeable metal material which will interact with the 
electromagnetic field flux to cause a strong generated current within the 
sensor element. Examples of suitable materials for the metal core include 
iron, nickel, cobalt, manganese, chromium, stainless steel, and the like, 
alone or in combination. Preferably, the metal core is composed of a 
stainless steel that has magnetic properties as a result of the presence 
of ferritic particles. A suitable example would be an American Iron and 
Steel Institute (AISI) 400 series stainless steel. The stainless steel 
core may also be covered with an outer layer of iron to further enhance 
its magnetic properties. In another embodiment, the metal core may have a 
distal section formed of an iron core that is bonded to a stainless steel 
core forming the center and proximal sections. 
When the sensing member is assembled into the lumen of the guide wire, the 
resulting guide wire apparatus possesses a level of flexibility yet 
stiffness comparable to the response, maneuverability and tactile feel of 
a guide wire without an internal sensor housed therein, like those of the 
traditional or conventional guide wire devices used in diagnostic and 
treatment procedures. In particular, the guide wire apparatus has an 
appropriate combination of stiffness and bendability to provide the 
desired control and flexibility for use in medical applications, such as 
angioplasty or catheterization procedures, for detecting obstructions 
within a channel of a body organ such as a blood vessel of a patient. 
It is preferred that the desired tactile response and maneuverability is 
provided in part by the construction of the guide wire, the sensing 
member, or both. Preferably, the metal core of the sensing member is 
constructed to provide the guide wire apparatus with the desired 
flexibility. For example, the center section of the metal core of the 
sensing member may be tapered so that the diameter of about its mid-point 
is less than the diameter of either the distal or proximal sections of the 
metal core. The tapered configuration of the metal core provides the 
sensing member with a flexibility or bendability factor to provide, at 
least in part, the desired level of flexibility and stiffness in the guide 
wire apparatus. 
A current conducting wire is preferably wound around the distal section of 
the metal core in one or more overlying layers, preferably two layers, to 
form the sensor element. The current conducting wire is composed of a fine 
wire with a diameter of about 0.04 to 0.08 mm, with about 0.05 mm being 
preferred. The distal section of the metal core is of a length suitable to 
accommodate an effective amount of the conducting wire to form the sensor 
element. In a preferred embodiment, the sensor element includes about 
250-300 winds, more preferably about 280 winds, of the conducting wire in 
a double layer over the distal section. The current conducting wire may be 
composed of any suitable material capable of conducting a current, as for 
example, the noble metals such as copper, silver, gold, platinum, 
palladium, or other like material, copper being most preferred. The ends 
of the current conducting wire are connected by two lead wires to the 
electronic controller. Preferably, the ends of the current conducting wire 
extend along the length of the metal core and connect with the lead wires 
at the proximal end of the apparatus. 
To protect the sensor element from damage, the sensing member may be coated 
with a protective covering material, preferably a flexible, non-toxic, 
insulating material. Suitable coating materials include polymer materials 
such as polyurethane, polyethylene, polyvinyl chloride, nylon (polyamide), 
teflon (Tetrafluoroethylene (TFE) fluorocarbon polymers, an example of 
which is polytetrafluoroethylene (trademarked as Teflon, a registered mark 
of The du Pont Company, Wilmington, Del. (polyperfluorolefin), or a 
polyester material. The polymer material may be applied by any suitable 
method which will provide a thin covering layer, preferably about 0.05 to 
0.2 mm thick, more preferably about 0.1 to 0.15 mm thick, on the surface 
of the sensing member without altering or damaging the sensor element. 
The diameters of the proximal, center and distal sections of the metal core 
are adapted to fit the sensing member having an applied coating layer 
within the lumen of the guide wire. In a preferred embodiment, the 
diameter of the distal section of metal core with a layer of conducting 
wire is about 0.3 to 1 mm, more preferably about 0.5 to 0.8 mm; and the 
diameter of the proximal core section is about 0.2 to 0.8 mm, more 
preferably about 0.3 to 0.5 mm. In a preferred embodiment of the sensing 
member, the diameter of the mid-point of the center core section of the 
metal core is about 0.1 to 0.4 mm, more preferably about 0.2 to 0.3 mm. 
The sensing member is housed within the lumen of the guide wire, preferably 
with the proximal end of the sensing member co-terminus with the proximal 
end of the guide wire. The lengths of the metal core and of the lumen of 
the guide wire are sufficient to place the sensor element in the area of 
the center portion of the guide wire at or near the adjoining distal 
portion. 
A first embodiment of the guide wire assembly in accordance with the 
invention is illustrated in FIGS. 1 through 3, and designated generally by 
the numeral 100. In general, the guide wire assembly 100 includes a 
J-shaped guide wire 110 and an internally-housed sensing member 120. 
Referring to FIG. 1, guide wire 110 includes a proximal portion 114, a 
center portion 116, and a distal portion 118, a proximal end 115, a distal 
end 117. Guidewire 110 also includes a lumen 112 into which sensing member 
120 is inserted. As shown in FIG. 2, sensing member 120 includes a metal 
core 122 that has a proximal section 124, a center section 126, and a 
distal section 128. As depicted, sensor element 132 is formed of a current 
conducting wire 134 wound around distal section 128 of metal core 122 in a 
double layer. As further illustrated, protective coating layer 135 covers 
sensing member 120 to protect sensor element 132 from damage. It is 
understood, however, that sensing member 120 need not be covered with 
protective coating layer 135. 
Sensing member 120 is located within guide wire 110 so that distal section 
128 with sensor element 132 are positioned in the area of center portion 
116 at or near adjoining distal portion 118 of guide wire 110. A safety 
wire 113 may be housed within lumen 112 and attached to guide wire 110 at 
proximal end 115 and distal end 117. 
In the first embodiment depicted in FIGS. 1 and 2, center section 126 of 
metal core 122 is tapered so that the diameter of about its mid-point 130 
is less than the diameter of either distal section 128 or proximal section 
124 of the metal core 122. As illustrated in FIG. 4, in a second 
embodiment of a guide wire assembly, designated generally by the numeral 
200, metal core 222 of sensing member 220 is not constricted at center 
section 226. Center section 226 provides a gradation in diameter from 
distal section 228 to proximal section 224 of metal core 222. 
In use, as depicted in FIG. 3, guide wire apparatus 100 is inserted into 
the body of a patient 150, and advanced according to standard placement 
procedures to a desired location 152 where sensor element 132 may be 
detected. For example, guide wire apparatus 100 may be inserted into a 
blood vessel and advanced until an obstruction or constriction is sensed 
by touch, and the location of distal portion 118 of guide wire 110 
detected. As depicted, current conducting wire 134 is connected by two 
lead wires 136, 137 to an electronic controller 140. To detect sensor 
element 132 of guide wire apparatus 100 in situ in the body, electronic 
controller 140 is activated to generate an alternating current to external 
field generator 146, positioned against the skin 154 of patient 150, which 
produces an electromagnetic (electromagnetic) energy field. The 
intersection of the electromagnetic energy field and sensor element 132 
may be determined by measurement of the variation of signal amplitude as 
the field generator 146 nears the location of sensor element 132. The 
construction and arrangement of the electromagnetic energy field relative 
to sensor element 132, and the function for the signal amplitude 
determination follow the methods of Van Steenwyk in U.S. Pat. No. 
4,173,228, the disclosure of which is incorporated herein by reference. 
The interaction of the electromagnetic energy field and sensor element 132 
may alternatively be determined by measurement of the phase transition of 
the current generated in sensor element 132 as the electromagnetic energy 
field moves over sensor element 132. In this embodiment, the construction 
and arrangement of the electromagnetic energy field relative to sensor 
element 132 and the function of the phase transition follow the method of 
Strohl et al. in U.S. Pat. No. 4,905,698 to Strohl et al.), the disclosure 
of which is incorporated by reference herein. Briefly, when field 
generator 146 is positioned to produce an electromagnetic energy field 
perpendicular to the long axis of sensor element 132, phase transition can 
be measured. As field generator 146 approaches sensor element 132, a 
voltage of a certain phase is produced in sensor element 132 by field 
generator 146. When field generator 146 is directly above sensor element 
132, a phase transition occurs whereby no voltage is momentarily produced. 
As field generator 146 passes beyond sensor element 132, voltage is again 
produced but is completely out of phase with the earlier voltage or with 
the alternating current operating field generator 146. The phase 
transition produces a series of visual and/or audio signals to indicate 
location. 
The construction of guide wire 110 and/or sensing element 132, 
advantageously provides a guide wire apparatus 100 that can internally 
house a location sensing device yet retain the flexibility and tactile 
response needed for maneuvering within branched systems, such as the 
vascular system, within the body of a patient similar to traditional guide 
wires. The guide wire apparatus of the invention, in general, is 
particularly useful in angioplasty or catheterization procedures, for 
detecting obstructions within a branched channels of a body system such as 
a blood vessel of a patient, and determining the location of the 
obstruction and distal end portion of the guide wire within such a body 
system. 
The invention has been described with reference to various specific and 
preferred embodiments and techniques. However, it should be understood 
that many variations and modifications may be made while remaining within 
the spirit and scope of the invention.