Note: Descriptions are shown in the official language in which they were submitted.
W096/08998 PCT~S94/10801
~21 9~ ~52
DESCRIPTION
DETERMINING POSITIONS OF CATHETERS AND PLACEMENT GUIDEWIRES
Field of the Invention
The present invention relates generally to a method
and apparatus for determining accurately the full-length
position of catheters, tubes, and placement guidewires
S inside biological tissue, particularly within veins and
arteries. This method is applicable to all catheter types
including implanted ports, but is especially useful for
central venous catheter placement applications. This
method is equally applicable for locating tubes inserted
into the body, such as enteral feeding tubes.
Backqround of the Invention
The placement of tubes and catheters in biological
tissue is generally accomplished by a blind technique
utilizing anatomical landmarks for guidance. Despite
strict adherence to protocol~ the catheter, or tube, may
deviate from the desired pathway for many different
reasons, some of which are within the control of the
technician and some that are not.
Methods and techniques for access to the central
venous system have been well established. Hemodynamic
monitoring and infusion of hyperosmolar solutions and
irritating drugs requires the positioning of the catheter
tip most commonly in the superior vena cava and less
commonly in the inferior vena cava. Aberrant positioning
of the catheter and catheter tip, either on insertion or
by spontaneous migration thereafter, may result in morbid
complications including venous or arterial thrombosis,
pericardial tamponade, retrograde cerebral perfusion with
neurotoxic symptomatology, venous perforation with
thoracic or mediastinal cavity perfusion, and arrhythmias.
W O 96/08998 PC~rAUS94/10801
0 2 1 9 9 9 5 ~
Gastric or intestinal positioning of various tubes are
also frequently placed by a blind approach. Malposition
of these tubes may result in severe consequence as well.
Current practice dictates visualization of catheters
or tubes during or following insertion by radiograph or
fluoroscopy. Most commonly the radiograph is taken
following catheter placement to confirm proper positioning
of the device, the tip in particular. Spontaneous
migration can presently only be determined by repeated
radiograph or fluoroscopy. Repeated exposure of the
patient and medical personnel to irradiation is
undesirable and costly. In addition, it is often
inconvenient to move a patient to an x-ray facility or
bring a portable x-ray unit to the patient either in the
hospital or home, and may result in prolonging initiation
of therapy.
Catheter tip-finding devices now in service can only
locate the catheter tip at the time of insertion of the
catheter by using a specially instrumented guidewire,
however, no system is available which can trace a
catheter's location after insertion. An example of such
a device is disclosed in U.S. Patent No. 4,905,698 issue
March 6, 1990, and assigned to Pharmacia Deltec Inc. of
St. Paul, MN. In the Pharmacia device the catheter is
inserted with a guide wire mounted internal to the
catheter. A part of the guidewire is a magnetic coil
pick-up device at the distal end of the guidewire located
within the distal end of the catheter. Once the
guidewire/ catheter combination is in place and the
technician is assured that it is in the correct location,
the guidewire is removed. To use the catheter of the
Pharmacia design the guidewire must first be removed. By
so doing the ability to locate the end of the catheter by
the magnetic method of Pharmacia is no longer possible
since the magnetic pick-up device for locating the end of
the catheter is attached to the distal end of the
guidewire.
W096/08998 PCT~S94/10801
021 9~ ~52
It would be advantageous to not only be able to locate
the tip of a placement guidewire upon insertion of the
guidewire/catheter combination, but to also be able to
determine the full length position upon insertion, and
equally important is the ability to continually be able to
monitor the location of the catheter at any time
thereafter in a diagnostic manner. The later function is
particularly desirable since there is no assurance that
the catheter will not migrate to another location while it
is still in use because of physical movements of the
patient. In addition, no device is presently available
which can locate the position of implanted port mounted
catheters. It is important to note that tubes (such as
enteral feeding tubes) inserted into the body are
physically very similar to catheters and it would be
advantageous to have a diagnostic location capability for
them upon insertion as well as after the fact since they
too can become malpositioned. The present invention
clearly has all of these capabilities.
Summary of the Invention
In accordance with the disclosed embodiments of the
present invention there is shown a method and apparatus
for continuous monitoring of the full-length path and
distal end position of catheters (including implanted port
models), tubes, and placement guidewires within a
patient~s body during initial insertion and at any time
thereafter.
Brief Description of Drawinqs
The illustrative embodiment of the present invention
may best be described by reference to the accompanying
drawings where:
Figure lA shows a diagrammatic view of a first
embodiment of a method and apparatus of the present
invention for determining the full length position of
catheters, tubes, and placement guidewires within
W096/08998 PCT~S94/10801
0 2 1 9 9 ~ 5 2
biological tissue before and after removal of the a
guidewire.
Figure lB schematically illustrates the use of a
transmitter/detector unit together with an implanted
catheter, tube or guidewire all designed according to the
present invention.
Figure lC illustrates the signal response of the
apparatus of the present invention produced in the
detector unit as it is swept over the patient in which a
catheter, tube or guidewire of the present invention has
been placed.
Figure lD shows a magnified view of the tip of one
guidewire of the present invention.
Figure lE shows a magnified view of the tip of one
catheter of the present invention.
Figure 2A is a longitudinal cross-sectional view of a
first embodiment guidewire assembly of the present
invention.
Figure 2B is a longitudinal cross-sectional view of a
first embodiment catheter or tube assembly of the present
invention.
Figure 3 is an electrical schematic representation of
the detector unit of Figure 1.
Figure 4 shows a diagrammatic view of a second
embodiment of a method and apparatus of the present
invention for determining the full length position of
catheters, tubes, and placement guidewires within
biological tissue before and after removal of the
guidewlre .
Figure 4A shows a magnified view of the tip of a
second guidewire of the present invention.
Figure 4B shows a magnified view of the tip of a
second catheter of the present invention.
Figure 5A is a longitudinal cross-sectional view of a
second embodiment guidewire assembly of the
present invention.
W O 96/08998 PCTrUS94/10801
0 2 1 99 ~ 5~
Figure 5B is a longitudinal cross-sectional view of a
second embodiment catheter or tube assembly of the present
invention.
Figure 6A is diagrammatic view of an implanted port
and catheter assembly of the present invention for
determining the full length position of implanted port
mounted catheters.
Figure 6B is a longitudinal cross-sectional view of
the in situ implanted port catheter assembly of Figure 6A
placed underneath the skin of a patient.
Figure 6C is a longitudinal cross-sectional view of
the port access needle assembly of the implanted port
catheter of the present invention for connecting the
implanted port catheter assembly of Figures 6A and 6B to
the external detector unit described in Figures lA and 4.
Figure 6D is a longitudinal cross-sectional view of
the port access needle assembly of Figure 6C inserted
through the patients' skin and into the implanted port and
catheter assembly of Figure 6B.
Figure 7A is a diagrammatic view of an infusion needle
assembly of the present invention for use with the
implanted port of Figure 6B to simultaneously allow
infusion of fluid into the implanted port catheter
assembly and determination of the full length position of
2 5 the implanted port assembly catheter of the present
invention.
Figure 7B is a longitudinal cross-sectional view of
the infusion needle assembly of Figure 7A, including an
enlarged view illustrating key needle details.
Figure 7C is a longitudinal cross-sectional view of
the infusion needle assembly and the implanted port
catheter of the present invention with the needle inserted
through the skin of a patient into the implanted port
catheter assembly and the alternative interface between an
3S infusion syringe and infusion drip line components.
All figures are drawn for ease of explanation of the
basic teachings of the present invention only; the
WO9~J~899b PCT~S94/10801
0 2 1 9 9 0 ~ 2
extensions of the figures with respect to number,
position, relationship, and dimension of the parts to form
the preferred embodiment will be explained or will be
within the skill of the art after the following teachings
of the present invention have been read and understood.
Further, the exact dimensions and dimensional proportions
to conform to specific force, weight, strength, and
similar requirements will likewise be within the skill of
the art after the following teachings of the present
invention have been read and understood.
The same numerals designate the same or similar parts
where used in the various figures.
Descri~tion of the Preferred Embodiments
Referring first to Figure lA there is shown the
component parts of the first embodiment of the present
invention which make it possible to determine the position
of a catheter during insertion, immediately after
insertion, and at any future time when the guidewire has
been removed and the catheter is in use. There are three
basic components to the first embodiment of the present
invention: transmitter/detector unit 2 which is common to
each embodiment of the present invention, guidewire
assembly 22, and catheter assembly 30. This system allows
a technician to determine the position, both along the
entire length and the tip, of percutaneous catheters,
tubes, and placement guidewires or catheters that are part
of an implantable access system within veins, arteries, or
other internal areas of a patient.
It is important to note that tubes (such as
enteral feeding tubes) inserted into the body are
physically very similar to catheters and need to be
carefully positioned and that position monitorable since
they too can become malpositioned. For purposes of this
application any discussion of catheters also applies to
tubes as a subset of catheters.
W O 96/08998 PC~rAUS94/10801
021 99 ~52
Generally, as will be described more fully below,
transmitter/detector unit 2 includes a main housing having
attached to the top side thereof an antenna 14 for
transmitting an RF signal to be radiated to an antenna, or
antennas, that are part of guidewire assembly 22 or
catheter assembly 30.
Transmitter/detector unit 2 also contains an internal
RF alternating current (AC) generator with it's RF signal
being applied to antenna 14. Internal to the housing of
transmitter/detector unit 2 there is also a signal
strength monitoring circuit and an annunciating device
that is coupled to the antennas of either the guidewire
assembly 22 or the catheter assembly 30 via cable 16 and
clip 18 for monitoring the signal strength and announcing
it to the technician as antenna 14 is passed over the skin
of the patient in an effort to locate guidewire
assembly 22 or catheter assembly 30.
As is typically done in the placement of a catheter or
a tube within a vein, artery or other internal area of a
patient, a guidewire, that has a smaller outer diameter
than the internal diameter of the catheter or tube to be
placed within the patient, is initially inserted into the
catheter or tube. This is done to provide added rigidity
to the catheter during the insertion procedure since
catheters are generally made of a very pliable material to
permit them to follow the natural internal paths through
veins, arteries and other paths. In the first embodiment
of the present invention, that procedure is also followed.
In the second embodiment the guidewire is inserted in the
patient first and when it's location has been determined
to be correct the catheter is inserted by slipping it over
the guidewire and when it is in the proper position the
guidewire is withdrawn. It is also a common practice to
insert some catheters without the aid of a guidewire. In
that situation all of the monitoring functions that are
split between the guidewire and the catheter in the above
discussion are performed using the catheter alone to the
W O 96/08998 P~r~US94/10801
~21 9~ ~52
extent possible. In any event, the actual location of the
catheter will be monitorable upon insertion and at any
time thereafter to confirm position of the catheter.
The construction details of the first embodiment of
guidewire assembly 22 and catheter assembly 30 of the
present invention can be seen by referring to Figures lA,
lD and 2A, and Figures lA, lE and 2B, respectively. As
shown in the figures, guidewire assembly 22 includes a
pliable shaft 23 of polyurethane or a similar material
(however, it would be possible to use a coiled stainless
steel guidewire with the antennas being electrically
insulated from the coil), and a terminal section 48.
Shaft 23 has a cross-sectional size and shape along it's
smallest dimension that can easily be accommodated by the
interior bore of the catheter tube 34, as well as having
molded therewithin two internal fine wire antennas. A
first antenna 28 is an unshielded wire that extends along
substantially the full length of shaft 23. Since antenna
28 is unshielded it can pick-up radiation along it's
entire length when an RF signal is received thus making it
possible to detect the position of guidewire assembly 22
along it's entire length. When antenna 28 is receiving
radiation it can be used in combination with transmitter/
detector unit 2 as discussed below for determining the
path and position of guidewire shaft 23 and the
surrounding catheter tube 34. The second antenna within
shaft 23 includes a shielded wire 26 that extends from
terminal section 48 to substantially the distal end of
shaft 23. At the distal end of shaft 23, shielded wire 26
is connected to a conductive mass 24. Since wire 26 is
shielded it only receives minimal radiation when exposed
to it. However, since conductive mass 24 is not shielded
or connected to the shield of wire 26, it can conduct
radiation that it is exposed to. Since the combination of
wire 26 and conductive mass 24 only receives radiation at
the distal end of shaft 23, it allows for the accurate
determination of the placement of the end of shaft 23, and
W096/08998 PCT~S94/10801
021 99 ~52
therefore the end of tube 34 that surrounds it. When
conductive mass 24 is receiving a radiated signal it can
be used in combination with transmitter/ detector unit 2,
as discussed below, for confirming the placement of the
tip of guidewire shaft 23.
Catheter/tube assembly 30 includes a pliable, thin
walled elongated tubular section 34 typically of
polyurethane, silastic, or a similar material, and a
terminal section 42. Molded within the elongated tube
section 34 is an unshielded fine wire antenna 32 that
extends longitudinally along substantially the entire
length thereof. Since antenna 32 is unshielded it will
receive radiation along it's entire length when an RF
signal in it's vicinity. When antenna 32 is receiving a
radiated signal it can be used in combination with
transmitter/detector unit 2 as discussed below for
determining the entire path and position of catheter tube
34. It is intended that antenna 32 will be used in post
catheter/tube insertion after guidewire 22 has been
removed from the interior of tube 34, however, it could
also be used with guidewire 22 still in place thus making
antenna 28 unnecessary. Since the use of guidewire
antenna 24 and catheter antenna 32 would require the
movement of clip 18, as will be seen when terminal
sections 42 and 48 are discussed more completely below, it
is more convenient to use the two antennas associated with
guidewire 22 for the initial placement of catheter
assembly 30.
It is important to note that catheters may also be
constructed with both a full length antenna and a shielded
wire and conductive tip pair as for the guidewire
described above without departing from the scope of the
present invention.
Referring now specifically to Figure 2A, antenna 28
and the wire within shield 40 each typically have a
diameter in the range of 0.006 inches (0.152 mm), and
conductive mass 24 at the distal end of shaft 23 is
W O 96/08998 PCTrUS94/10801
0 2 1 9 ~ ~ 5 2
typically a disk of a conductive material with a diameter
is in the range of 0.020 (0.508 mm). While a fine wire is
the preferred antenna implementation, a thin strip of
conductive film or foil could alternatively be used with
equal effect. Connected to the proximate end of shaft 23
is terminal section 48 to provide a platform to which to
connect clip 18 of transmitter/detector unit 2 to couple
RF signals received by antennas 28 and 24 thereto. To
interface with the jaws 20 of clip 18, terminal section 48
has formed therein two opposing notches sized and shaped
to receive the two opposing jaws 20 of clip 18. In this
illustrated view there is a first conductive pad 46
mounted in the notch on the top of terminal section 48
with first conductive pad 46 electrically interconnected
to the proximate end of antenna 28 within shaft 23.
Similarly, in the notch on the bottom of terminal section
48 there are second and third conductive pads 50 and 52
connected to shield 40 and wire 26, respectively, at the
proximate end of shaft 23. A thin-film plastic insulator
electrically isolates wire 26 from the conductive foil of
shield 40.
Similarly, referring now specifically to Figure 2B
antenna 32 typically has a diameter in the range of 0.002
inches (0.051 mm), and it can be seen that the proximate
end of catheter tube 34 is connected to terminal section
42 to provide a platform to which to connect clip 18 of
transmitter/detector unit 2 to couple RF signals to
antenna 32. Since in the preferred embodiment there is
only one antenna in catheter assembly 30 only one
conductive pad must be provided to interface with clip 18.
This is illustrated by conductive pad 44 mounted in the
notch on the top of terminal section 42. Pad 44 is
connected to the proximate end of antenna 32 within tube
34. Since terminal section 42, as does terminal section
48 of guidewire assembly 22, interfaces with jaws 20 of
clip 18 even though catheter assembly 30 only has one
conductive pad 44, terminal section 42 must 5 also have
W096t08998 PCT~S94/10801
i3 2 ~ ~ 9 9 5 2
11
two opposing notches sized and shaped to receive the two
opposing jaws 20 of clip 18. Additionally, terminal
section 42 must have a centrally located hole therethrough
to permit the insertion of shaft section 23 of guidewire
5 assembly 22 into the central bore of catheter tube section
34 prior to insertion of catheter assembly 34 into the
patient.
Since shaft section 23 of guidewire assembly 22 is to
be inserted into the internal bore of tube section 34 of
catheter assembly 30 through terminal section 42, the
length of shaft section 23 must be at least as long as,
and usually longer than, the combined length of tube
section 34 and terminal section 42 so that the distal end
of shaft section 23 at least aligns with, and typically
15 protrudes from, the distal end of tube section 34 at the
time of insertion of catheter assembly 30 into the
patient.
Alternatively, the RF signal could be applied to
antennas 24, 28 and 32 instead of being radiated from
20 antenna 14 and the same results would be achieved.
However, for safety reasons it is probably more
advantageous to apply the RF signal to antenna 14 and to
detect the radiation with the implanted antennas as
discussed above.
Antenna 14 ( see Figure lA) is designed to transmit an
AC magnetic field with the preferred form of antenna 14
being a coil in a "U"-shaped enclosure that extends
outward from the body of transmitter/detector 2.
Typically antenna 14 will radiate a signal in the range of
one-half to one watt at a preferred frequency in the lO0
kilohertz to 150 megahertz range with sections of antenna
14 being shielded and grounded to tailor and/or confine
the transmitted RF field.
In use, as shown in Figure lB, antenna 14 is
35 positionable near the surface of the patient's skin with
the magnetic flux lines 36 projecting radially into the
patient's body. As antenna 14 is passed over the
W096/08998 PCT~S9~/10801
021 9~ ~2
12
patient's skin surface the RF field 36 is detected by
either of the guidewire antennas 24 and 28 or
catheter/tube antenna 32, depending on whether clip 18 is
connected to terminal section 48 or 44.
Clip 18 and cable 16 are provided to couple any RF
signals received by the antenna(s) to which it is
connected to transmitter/detector 2. Any received RF
signals are then processed to provide visual and audible
signals as to the relative spatial proximity of the
transmitter antenna 14 and antennas 24, 28 or 32.
Transmitter/detector 2 in the most usable
configuration will take the form of a self-contained
handheld unit that contains RF transmitter and detector
circuits, operator user interfaces, and a rechargeable
power supply system and batteries. As stated above,
antenna 14 in such a unit is mounted externally in a
"U"-shaped fashion. This shape of antenna 14 thus emits
a cylindrical field 36, and also effectively lessens
hazards posed by a single, rod type antenna.
Alternatively, antenna 14 could be a hand-held unit that
is connected to a fixed-base transmitter/detector unit by
an interconnecting cable.
In use, as illustrated in Figures lB and lC, antenna
14 of transmitter/detector 2 is passed over the surface of
the patient's skin and RF field 36 radiates into the
tissue of the patient. As that radiation is received by
the antennas in either guidewire shaft 23 or catheter tube
34 a signal is conducted to the detector circuit within
transmitter/detector 2 by clip 18 and cable 16. The
detector circuit then in response to the received signal
generates a visual and an audible indication which varies
as does the characteristic signal response curve 38 as
illustrated in Figure lC, with a peak audible or visual
response that coincides with the sharp signal peak
generated when antenna 14 is directly above guidewire
assembly 22 or catheter/tube assembly 30. When the peak
is reached and then begins to drop again, transmitter/
W096/08998 PCT~S94/10801
~21 99 952
13
detector 2 can be moved back and forth to find the point
at which the peak signal is discovered. By discovering the
peak signal location the user knows that the guidewire or
catheter is directly beneath that point on the surface of
the patient's skin.
Since antennas 24, 28 or 32 are generally in the "near
field" region of the signal transmitted from antenna 14,
the received signal strength varies approximately as the
cube of the distances between the transmitting and
receiving antennas. An additional crucial benefit is that
the orientation of the catheter, tube, or guidewire
segment at any point may be inferred by rotating antenna
14 longitudinally above the patient's skin. The detected
signal strength will be at a maximum when antenna 14 is
aligned with the antenna mounted in the catheter, tube, or
guidewire. In this way, transmitter/detector 2 provides
not only the full length path determination, but
individual segment orientation information of the
guidewire or catheter as well.
By performing this technique while monitoring the
signal from guidewire antenna 28 or catheter antenna 32,
the actual location of the entire path of the guidewire or
catheter can be determined. Similarly, if this technique
is performed while monitoring the signal received by
guidewire antenna 24 the position on the surface of the
skin beneath which the end of the guidewire is located can
be determined.
Figure 3 is a schematic illustration of a circuit that
can be used for the transmitter and detector functions of
transmitter/detector 2 with that circuit enclosed within
a dotted-outline. Included is a battery power source
which is indicated as +V which may also include a
recharger for the battery. The power from the battery is
applied to the circuitry by closure of switch 4 which
causes the illumination of LED 6 to indicate that the
power has been turned on. Below the dotted-outline for
transmitter/detector 2, shown schematically are cable/clip
W096/08998 PCT~S94/10801
0 2 1 9 ~ ~ 5 2
14
combination 16 and 18, catheter assembly 30 with included
antenna 32, and guidewire assembly 22 with included
antenna 28 and shielded cable 26 with attached tip antenna
24, and the possible connection between the various
antennas and clip 18 shown in dotted lines. Internal to
transmitter/detector 2 is a switch 2 for selecting between
the two antennas within guidewire assembly 22 for the
detection of the received signal.
In general, the circuit of transmitter/detector 2 can
be considered to have two sections: the first section
including an RF transmitter; and the second section
including detection circuitry and an amplifier for driving
the indicators for operator use in determining the
location of the guidewire or catheter.
The first section is RF Transmitter device 13 that can
be any convenient low power transmitter that meets with
FCC approval. For example, that transmitter could
transmit on a frequency of 46 MHz at an input power of no
more than 2 watts. Such a transmitter is used in a SONY
Model No. NTM-l transmitter, or similar circuit, which was
found to be satisfactory.
The second section receives the RF energy detected by
one of antennas 32, 28, and 24 via cable/clip 16/18 and
single-pole double throw (SPDT) analog switch S2. For the
guidewire arrangement, S2 switches between the full-length
and tip antennas for locating the transmitter antenna path
and tip, respectively. For catheter/tube antenna 32, S2
remains in the position shown, and for guidewire antennas
24 and 28, S2 must be set to the position that corresponds
to the antenna which the user wishes to monitor depending
on what information the user is interested in. While not
shown here, it may be appreciated that S2 can be automated
with a digital switch to automatically switch between
full-length and tip-finding modes of the guidewire
assembly to provide real-time path and tip location
determination. From S2, the received RF signal passes
through blocking capacitor C3 which serves as a high-pass
W096/08998 ~CT~S94/10801
~ 2 ~ 5 2
filter to block DC signal amplification. The RF signal is
detected by inductor Ll and sampled by diode Dl, which
rectifies the AC of the RF signal to DC and feeds it to
the negative input of op-amp Ul (e.g. Motorola type 1458).
Op-amp Ul then produces an output voltage that is
proportional to the signal strength of the received RF
signal. This voltage is then applied to the positive
input of op-amp U2 (e.g. Fairchild type 741 wired in a
non-inverting mode) and a voltage to frequency converter
chip 53 (e.g. Analog Devices type AD537). Converter chip
53 produces an audible frequency signal the frequency of
which is proportional to the input voltage. The audible
frequency signal from chip 53 is then applied to speaker
12 to enable the technician to hear the tone. For
simplicity, the tone volume and frequency controls for
varying same have been omitted from this circuit, however
they are well known in the art. Op-amp U2 has been
included to process the signal from op-amp Ul to provide
the visual display information of the received signal.
The gain of op-amp U2 is set by resistors R4 and R5, with
resistor R5 being variable and used as gain control 10.
In the preferred embodiment of his circuit, the maximum
gain setting is in the range of 25 which produces
approximately a +5 Volts full-scale on the output terminal
of op-amp U2. This voltage is then applied to LED driver
chip 55 (e.g. National Semiconductor type 3914 Dot/Bar
Display Driver). Chip 55 compares the output voltage from
op-amp U2 to an internal reference voltage and
proportionally illuminates a display of a plurality of
devices, or one that is capable of indicating signal
relative strength, for example by means of a plurality of
LEDs or LCDs or a bar graph, with the intensity of the
display being directly proportional to the strength of the
received signal.
Two signaling methods are provided for the operator:
a linear LED array 8 and an audible tone from speaker 12.
The linear LED array 8 is moderated by variable gain
W096/08998 PCT~S94/10801
0 2 ~ 9 ~ ~ 5 2
16
control resister R5 to which knob 10 is affixed and
displays the detected signal strength, and hence the
relative proximity of transmitting antenna 14 to the
receiving antennas 24, 28 and 32. As antenna 14 is
brought closer to the receiving antennas being monitored,
a varying number of LEDs in array 8 are illuminated in
sequence in a bar graph fashion, and extinguish
sequentially as antenna 14 passes away from the receiving
antenna being monitored. Similarly, speaker 12 emits a
tone whose frequency varies as a function of the proximity
of antenna 14 to the receiving antenna being monitored.
As antenna 14 approaches the receiving antenna being
monitored, the frequency of the tone increases, and as
antenna 14 moves away from the receiving antenna being
monitored the frequency of the tone decreases, both in
proportion to the proximity of antenna 14 to the receiving
antenna being monitored.
Once the guidewire/catheter combination is in the
desired position, guidewire assembly 22 may simply be
withdrawn from catheter assembly 30 by pulling on terminal
section 48 of the guidewire assembly and then disposed of.
To diagnostically monitor the post-insertion catheter or
tube location, the operator merely connects the removable
clip 18 to the exposed catheter terminal section 42 and
sweeps antenna 14 over the patient as in the guidewire
method. Specifically the operator may start at catheter
terminal section 42 and sweep outward along the expected
catheter/tube path, or sweep specific areas of interest to
ensure that the catheter or tube has not migrated from its
intended position. This diagnostic method is advantageous
because it is non-invasive and may be performed without
unduly disturbing the catheter.
The second embodiment guidewire and catheter 30
assemblies 22' and 34' are shown in detail in Figures 4,
4A, 4B, 5A and 5B. In each case they are substantially
the same as their first embodiment equivalents except for
the fact that catheter/tube assembly 34' can be inserted
W096/08998 PCT~S94/10801
021 99 ~52
17
over guidewire assembly 22' after guidewire assembly 22'
has been placed in the desired tissue location. The
differences between th~ two embodiments are strictly to
permit that operation, otherwise the general features of
each are the same. To enable that technique, terminal
portion 48 of the first embodiment guidewire has been
replaced with terminal portion 48' and terminal portion 42
of the first embodiment catheter has been modified to
terminal portion 42' to accept a modified clip 18' which
has been modified to interface with modified guidewire
terminal portion 48'.
Since the modifications to the guidewire terminal
portion are controlling of the other modifications,
attention is first directed to Figure 5A where the
specific details of the second embodiment of guidewire
assembly 22' are shown. As can be seen by comparing
Figures 2A and 5A the only differences are in the
configuration of terminal portion 48'. As can be seen in
Figure 5A terminal portion 48' is of the same diameter of
shaft 23 with three concentric parallel conductive rings
46', 50' and 52' which in function correspond to contacts
46, 10 and 52 in Figure 2A. To mate with rings 46', 50'
and 12~ the conductive pads (not shown) within jaws 20' of
clip 18' will have to be oriented to mate with them (e.g.
the contacts in jaws 20' might be oriented such that rings
46' and 52' are mated with by the top jaw and ring 50'
mate with by the bottom jaw). Additionally, terminal
portion 48' must extend from the proximate end of modified
catheter terminal portion 42', as shown in Figure 5B,
after catheter tube 34' is slid over guidewire 22' and
thereby inserted into the tissue of the patient. This is
necessary so that clip 18' can be connected to terminal
portion 48' when both the catheter and the guidewire are
in place.
By comparing Figures 2B and 5B it can be seen that
only terminal portion 42' has been modified to except the
modified jaws 20' of clip 18~ so that the same contact pad
W096/08998 PCT~S94/10801
~ 2 ~
18
in top jaw 20' mates with conductive pad or ring 44' which
is in the same location on terminal portion 42' as is ring
46' on modified guidewire terminal portion 48'.
To enable the technician to align the distal end(s) of
said catheter/tube 30' with the distal end of said
guidewire 22' when catheter/tube 30' is inserted into the
patient by sliding it over said guidewire 22' ruled guide
stripes 25 are molded into or printed onto the external
surfaces at regular intervals to show the relative segment
lengths of the inserted guidewire and catheter so that the
detected end of guidewire 22~ will correspond to the end
of catheter/tube 30'. Alternatively, a line 60 could be
included near the proximate end of guidewire 22' so that
the length of guidewire 22' from it's distal end to line
60 is substantially the same as the combined length of
catheter 34' and terminal portion 42'. In this
configuration to align the distal ends of guidewire 22'
and catheter tube 34' as catheter 30' is insert over
guidewire 22', the proximate end 62 of terminal portion
42' of catheter/tube 30' must be substantially aligned
with line 60 near the proximate end of guidewire 22'.
The rest of the features of the second embodiment are
the same as those of the first embodiment and function in
the same way.
Referring now to Figures 6A-6D and 7A-7C there is
shown an implanted port and associated component parts
which make it possible to determine the position of an
implanted port and corresponding catheter during inser-
tion, immediately after insertion, and at any future time
the port/catheter is in use.
Figure 6A is an isometric external view of an
implanted port assembly 64 of the present invention. Port
assembly 64 includes a port body 66 made of polyurethane,
or a similar material, on which is mounted a domed cover
68 made of silicone rubber, or a similar material. Domed
cover 68 is provided to allow insertion of a needle, or
similar device, to infuse liquids into port body 66 while
W096108998 PCT~S94110801
5 2
19
also maintaining a seal to preclude bodily fluids from
entering the port body 66 during infusion and after the
infusion needle is withdrawn. Attached to port body 66 is
an external coupling 70 which is made of polyurethane, or
5 similar material, for rigidly coupling a catheter 72
thereto. Catheter 72 thus serves as a conduit to transfer
infused fluids from port body 66 to selected locations
within the body of the patient. Mounted integral within
the wall of port catheter 72 is a fine antenna wire 74
that runs substantively the full length of port catheter
72 with antenna 74 being of a design that is similar to
the previously discussed antenna embodiments.
Referring next to Figure 6B there is shown a
cross-sectional view of an implanted port assembly 64
15 placed beneath a patient's skin 76. Additional features
of the port assembly of the present invention can be seen
in this figure, including the internal cavity of port body
66 being in the shape of a round well, however, it can be
in any convenient shape. At the bottom of the well is a
20 layer of a fine conductive mesh 80 made of copper,
stainless steel, or a similar material. Above the layer
of conductive mesh 80 is a sealant layer 78 of silicone
rubber, or similar material, to prevent infused liquids
from coming into contact with the layer of conductive mesh
25 80. Through the wall of port body 66 and external
coupling 70, conductive mesh layer 80 is electrically
connected to catheter antenna wire 74 by a transfer wire
82 of shielded copper, or a similar material.
Next, in Figure 6C there is shown a cross-sectional
view of a port access needle 84 of the present invention.
Port access needle 84 includes a cylindrical conductive
core 88 having a sharp-tipped distal end with core 88 made
of stainless steel, or a similar material, housed within
a non-conducting insulator sheath 86 made of Teflon, or a
similar material. The proximate end of insulator sheath
86 is capped by a button 92 with sheath 86 made of
polyurethane, or a similar material, with button 92 being
W096/08998 PCT~S94/10801
021 9~ ~52
provided to aid the technician in the gripping and
inserting of port access needle 84 into the well of port
body 66. Electrically connected to conductive core 88 and
extending outward through insulator sheath 86, j ust below
button 92, is shielded signal cable 90. The other end of
cable 90 plugs into the transmitter/detector unit 2 in a
similar fashion as the conductive clip assembly 18 and
cable 16 as in Figure lA as discussed above.
The view in Figure 6D is similar to that of Figure 6B
with the addition of port access needle 84 inserted
through the patient's skin 76 and into port assembly 64.
This is done to determine the positioning of catheter 72
that is attached to implanted port assembly 64 in much the
same way as discussed above for the first two embodiments
15 of the present invention. On insertion, the tip of the
port access needle 84 penetrates skin 76, pierces domed
cover 68, passes through sealant layer 78, and terminates
within conductive mesh layer 80. In this way, the
detector circuit of transmitter/detector 2 is connected
20 electrically connected to catheter antenna wire 74, in
sequence through signal cable 90, conductive core 88,
conductive mesh 80, and transfer wire 82. Hence, the
detector of transmitter/ detector unit 2 is free to
receive RF energy from transmitter antenna 14 mounted on
25 the transmitter/detector unit 2 in an identical manner as
the previously discussed catheter and guidewire mounted
antenna embodiments. The method for locating implanted
port mounted catheters is identical to the method
previously discussed for locating catheters, tubes, and
placement guidewires.
Referring to Figures 7A-7C there is shown an infusion
needle assembly 94 for use with implanted port assembly
64, both of the present invention. As will be seen in the
following discussion, the infusion needle a','assembly 94
makes it possible to simultaneously infuse liquids into
the implanted port catheter assembly 64 /72 and to
determine the full length position of the implanted port
W096/08998 PCT~S94/10801
0 2 1 9 9 ~ 5 2
21
mounted catheter 72 during insertion and at any time
thereafter.
Referring first t~ Figure 7A there is shown an
isometric view of a port infusion needle assembly 94 of
the present invention. The component parts of the
assembly are needle 96 connected to the distal end of "L"-
shaped fluid tube 98 which is mounted on the placement pad
100 in the central portion of tube 98. Placement pad 100
is optional, however, if it is utilized it can aid in the
stabilization of infusion needle 96 when it is installed.
Between the central portion and the proximate end of fluid
tube 98 there is a conductive ring 102, and at the
proximate end of tube 98 there is a tube receptacle 104.
As described more completely below, conductive ring 102
provides the interconnection site between transmitter/
detector 2 and catheter antenna 74 via conductive clip 18
and cable 16 (see Figure lA).
Figure 7B is provided to show a longitudinal cross-
sectional view of the infusion needle assembly 94 on the
left side, and an enlarged inset of a cross-sectional view
of needle 96 on the right side. It can be seen that
needle 96 includes an electrically conductive core 106
made from stainless steel, or similar material, that,
except for the distal tip, is coated on the exterior with
a non-conductive sheath 110 of Teflon, or similar
material. In the center of conductive core 106 and
extending longitudinally along about three-quarters of the
length thereof toward the tip, there is a central cavity
114 that is disposed to be connected to the distal end of
fluid tube 98. Additionally, central cavity 114 is in
communication with a needle port 116 at the furthest
distance from fluid tube 98 that extends outward through
conductive core 106 and non-conductive sheath 110 to the
side of needle 96 about one-quarter of the distance from
the tip thereof. The interior of central cavity 114 and
needle port 116 is coated on the interior with Teflon, or
similar material, 112 and seals with non-conductive sheath
W096/08998 PCT~S94110801
22
110 on the exterior of needle 96. Thus, in this
configuration, the outer surface of needle 96 is only
electrically conductive at its tip at the distal end, in
much the same manner as port access needle 84 described
previously. To interconnect needle 96 with
transmitter/detector 2, conductive core 106 is
electrically connected to conductive ring 102 via transfer
wire 108 which is shielded copper, or similar material,
that travels along the length of the exterior of fluid
tube 98 and is connected to conductive core 106 interior
to non-conductive sheath 110.
Then in Figure 7C there is shown infusion needle
assembly 94 with needle 96 inserted through both the
patient's skin 76 and dome 68 extending into the interior
well of implanted port assembly 64. To stabilize infusion
needle 96, tube 98 can be taped in place on the skin of
the patient, or, if placement pad 100 is used it is placed
in contact with the patient's skin and a piece of adhesive
tape placed over it to prevent needle 96 from moving or
becoming dislodged from implanted port assembly 64.
To infuse liquids into the patients' body once needle
96 is in place, the technician may attach an infusion
syringe 118 or a drip line 120 to tube receptacle 104
introducing fluid into port assembly 64 via tube 98 and
needle 96. This occurs as the fluid travels through fluid
tube 98 and central cavity 114 and exits needle 96 to the
side through needle port 116 into the well of infusion
port assembly 64. The infused fluid then travels outward
from the well of port body 66, through external coupling
~0 70 and then through catheter 72 to the desired location
within the patients' body. The fluid flow 122 is shown
illustratively in Figure 7C by means of the arrows within
the well of infusion port assembly 64 and from the end of
catheter 72.
To determine the location of catheter 72 once infusion
needle assembly 94 is in place, the technician places clip
18 onto conductive ring 102, in much the same manner as
W096/08998 PCT~S94/10801
0 2 1 9 9 9 5 2
23
for the catheter and guidewire contacts for the first and
second embodiments described previously. The technician
then sweeps the body with transmitter/detector unit 2 in
a similar fashion to that described previously for the
other embodiments of the present invention.
In keeping with the theme of the present invention it
should be obvious that the present invention includes the
possibility of threading a wire down the internal cavity
of an implanted catheter, some distance which maybe less
than the full length of the catheter, and using that wire
to either radiate or detect an RF signal to make it
possible to locate the catheter position using the
equipment and method of the present invention. Therefore
such a threaded wire is to be included in the definition
of a guidewire as discussed above. When discussing the
relative motion between the radiating and detecting
antennas it should be understood that motion can be
created be mechanical motion between the antennas or by
making one of the antennas be an antenna array with the
signal switched electrically through the array to make it
appear that there is physical motion between the antennas,
therefore this is included in the definition of providing
relative motion between the antennas. Additionally, the
discussion above has generally referred to full length
antennas or the detection of the end of the catheter or
guidewire from a conductive mass at the distal end
thereof. The same technology and equipment that has been
modified slightly can be used to detect the position with
an antenna that is less than the full length of the
catheter or guidewire, or from conductive masses that are
placed at selected locations along the catheter or
guidewire, e.g. at locations that are l/4, l/2, or 3/4 of
the full length. These too should be considered to be part
of the method and apparatus of the present invention and
included in the definition of catheter and guidewire of
the present invention. Still further, the catheter and
tube that were described above where of the type that have
W096/08998 PCT~S94/10801
~ 2 ~ 2
24
a central hole extending longitudinally therethrough, and
there are some catheter and tube designs that have a blind
end with exit ports through the side walls. The same
techniques described above are also applicable to
catheters and tubes of that design. Finally, there may be
a need to exchange a catheter once it has been installed
since they sometimes become infected. To perform that
exchange a guidewire that is at least a few centimeters
longer than the catheter is inserted into the catheter
that is to be withdrawn and they both are withdrawn
leaving several centimeters of the guidewire in place
following the removal of the catheter and then the new
catheter is inserted over the guidewire and the
combination inserted in the same way that the original
catheter was inserted. In this situation, or in any
insertion situation, it might be desirable to check the
location of a portion of the catheter or guidewire before
it is fully inserted. That operation is also part of the
present invention and the claims are to be interpreted to
cover that situation as well.
Thus since the invention disclosed herein may be
embodied in other specific forms without departing from
the spirit or general characteristics thereof, some of
which forms have been indicated, the embodiments described
herein are to be considered in all respects illustrative
and not restrictive. The scope of the invention is to be
indicated by the broadest interpretation of the appended
claims, rather than being limited to the embodiments shown
and discussed in the foregoing description, and all
changes which come within the meaning and range of
equivalency of the claims are intended embraced therein.
