Surgical needle abstract
Transverse notches in a surgical needle provide an increased reflecting
area and enhanced response to ultrasonic probing to provide an enhanced
image on an ultrasonic echo sensor. Having the notch cut through
to the needle lumen entrains small air bubbles in the notch further
enhancing ultrasonic reflection and ultimate imaging of the needle's
Surgical needle claims
What is claimed is:
1. A surgical needle visible to ultrasound comprising:
a tubular sidewall defining a lumen and having an axis, said sidewall
having at least one transverse notch that intersects said sidewall
over less than 180.degree. of the circumference of the sidewall,
said notch having a first face, there being an acute angle relationship
between a substantial portion of said first face and lines parallel
to said axis.
2. The surgical needle of claim 1 wherein:
at least a portion of said notch extends through said sidewall
to said lumen of said needle to provide communication between said
notch and said lumen.
3. The surgical needle of claim 1 further comprising a plurality
of said notches.
4. The surgical needle of claim 2 further comprising a plurality
of said notches.
5. The surgical needle of claim 2 wherein: said notch intersects
the sidewall of the needle over less than 120.degree. of the circumference
of the needle.
6. The surgical needle of claim 4 wherein: each of said notches
intersects said sidewall of the needle over less than 120.degree.
of the circumference of the needle.
7. The surgical needle of claim 1 wherein: said notch has a second
face, there being an acute angle relationship between a substantial
portion of said second face and lines parallel to said axis.
8. The surgical needle of claim 7 wherein: each of said first and
second faces are flat faces and wherein said acute angle relationships
are between 15.degree. and 75.degree..
9. The surgical needle of claim 2 wherein: said notch has a second
face, there being an acute angle relationship between a substantial
portion of said second face and lines parallel to said axis.
10. The surgical needle of claim 9 wherein: each of said first
and second faces are flat faces and wherein said acute angle relationships
are between 15.degree. and 75.degree..
11. The surgical needle of claim 3 wherein: each of said notches
has a second face defining a surface having a substantial part thereof
that intersects a line parallel to said axis at an acute angle.
12. The surgical needle of claim 11 wherein: each of said first
and second faces are flat faces and wherein said acute angles are
between 15.degree. and 75.degree..
13. The surgical needle of claim 2 further comprising:
a finger actuated spring loaded stylet in said lumen of said tubular
14. The surgical needle of claim 13 wherein: said stylet has a
hub, said needle has a hub and said spring is positioned between
15. The method of enhancing the visibility of a surgical needle
having a lumen comprising the step of:
introducing air bubbles into the notch of claim 2.
16. The method of claim 15 wherein said step of introducing air
bubbles includes introducing a stylet into the lumen of the needle
after the needle is positioned.
Surgical needle description
BACKGROUND OF THE INVENTION
This invention relates to a medical device that provides enhanced
image and response to an ultrasound signal and more particularly
to a surgical needle having geometric features that provides an
enhanced image and response.
Ultrasonic imaging has long been used in medical practice to provide
images not only of body organs and parts but also of the medical
instruments and in particular needles that are used in connection
with various medical procedures.
For example, ultrasonic imaging is used to guide a medical needle
into a body part to effect a biopsy, to access fluid collection
for sampling or drainage, to obtain vascular access and to access
the urinary and biliary tracts. Ultrasonic imaging is also used
to place a needle at a tumor or other body structure for subsequent
A major limitation on the ultrasonic guided intervention or procedures
are the inability to image the medical instrument or needle adequately
in many circumstances. The visibility of the needle is strongly
dependent on the particular geometrical relationship between the
transducer that provides the ultrasonic beam and the reflective
surface of the instrument. The amount of ultrasonic energy reflected
from the instrument toward the transducer (an ultrasonic echo sensor)
determines the quality of the image of the instrument on the monitor.
If the needle is in the plane of the interrogating ultrasonic beam
and horizontal to the face of the sensing transducer, or perpendicular
to the direction of the incident beam, the reflected energy is optimized
and a usable visible image is obtained. However, as the needle becomes
less perpendicular to the direction of the incident beam, lesser
amounts of ultrasonic energy are reflected to the sensor and the
instrument is imaged poorly or not at all.
The optimal geometric relationship is difficult to maintain in
all but fairly limited applications of ultrasonic guided interventions.
It becomes nearly impossible to maintain the optimum geometry in
many instances because of intervening organs or structures. This
results in poor visualization of the instrument, procedure time
is lengthened and complexities are created which would not be present
if the needle were easily seen.
Multiple passes with a needle may have to be made before it can
be visualized causing tissue damage within adjacent organs or structures
and creating the potential of bleeding and other complications.
There are times when the physician is able to visualize the target
lesion quite well but not the needle or other instrument. Moving
the sensing transducer can result in the needle being imaged but
the image of the target lesion is lost. A series of trial and error
maneuvers are employed. Breathing motion of the patient further
complicates the process.
This problem has been addressed by a large number of proposed designs,
including those shown in U.S. Pat. No. 4869259 No. 4977897
No. 5048530 No. 5081997 No. 5213569 No. 5221269 No.
5383466 No. 5490521 No. 5611345 No. 5766135 and No. 5769795.
The devices shown in the above referenced patents are intended
to enhance ultrasonic visibility. Some of these devices are complex
and expensive to manufacture. Some of these devices are difficult
to manipulate within the patient such as the square rectangular
shaped needle suggested in U.S. Pat. No. 5611345. Furthermore,
many of the devices only marginally enhance ultrasonic visibility.
Accordingly, it is an object of this invention to provide a design
for a medical instrument and in particular a needle which will provide
enhanced imaging in a wide range of orientations between the axis
of the needle and the ultrasonic echo sensor.
It is a further and related object of this invention to provide
this enhanced imaging in a design that is simple and inexpensive
to manufacture and relatively simple to operate.
These two objects are important in order to assure maximum usage
of the invention in a large number and a wide variety of applications
where an ultrasonically identified needle is important.
Furthermore, it is another related purpose of this invention to
provide the above objectives in a design which provides no additional
risk of trauma to tissue.
There are inevitable trade-offs to the design considerations to
achieve the above interrelated objectives. Addressing all of these
considerations calls for some tradeoff between the objectives.
Accordingly, it is a major object of this invention to provide
an enhanced ultrasonically visible needle which achieves the objectives
of low cost, simple structure, high visibility, high degree of safety
and avoids complicated procedures or new techniques with which medical
personnel are not familiar.
Most particularly, it is an object of this invention to achieve
all of these objects with an enhanced trade-off value for the combined
In brief, one embodiment of this invention is a surgical needle
manufactured of stainless steel or some other material which provides
an interface with human tissue that results in an ultrasonic echo.
One or more transverse notches are cut into the sidewall of the
needle. In one tested embodiment, the transverse notch intersects
the circumference of the needle over approximately 100.degree..
Thus the notch cuts through to the lumen. The notch is a wedge-shaped
notch defining first and second oblique walls in the sidewall of
the lumen. Where these walls are planar, the plane of each wall
intersects the axis of the needle at an acute angle. The acute angle
may range from 15.degree. to 75.degree. and in a preferred embodiment
are each 45.degree.. The walls created by the notch provide a large
amount of reflective surface area.
In operation, when the needle is inserted into a patient, the surface
of the needle will reflect incident ultrasonic energy in directions
that are determined by the needle sidewall and the two notch walls.
The result is to reflect ultrasonic energy at a substantial range
of angles. When the needle is inserted into a patient, sufficient
air is inevitably entrained so as to provide small air bubbles which
form on or are trapped in the notches. These air bubbles provide
a further sound velocity contrast with tissue so as to enhance wide
angle reflection of an incident ultrasonic energy pulse. In this
fashion, the ultrasonic echo sensor can have a wide variety of spatial
orientations relative to the needle and yet receive a strong enough
ultrasonic echo to provide a usable and useful image of the needle.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a longitudinal sectional view of one embodiment of this
invention showing a particular notch arrangement at the distal portion
of a needle; the planes of the notch faces 18 and 20 being at 450
to the lumen axis.
FIG. 2 is a plan view of the FIG. 1 needle.
FIG. 3 is a longitudinal view similar to that of FIG. 1 showing
a second embodiment in which the plane of the notch faces are at
different angles to the axis of the lumen.
FIG. 4 is a plan view of the FIG. 3 needle.
FIG. 5 is a mechanical schematic showing the arrangement of a manually
operable spring loaded stylet that can be employed within the needle
of this invention to assure the trapping of air bubbles in the notch.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The FIG. 1 embodiment shows a surgical needle 10. A series of transverse
notches 12 near the distal end of the needle extend around substantially
less than half the circumference of the needle. Each notch 12 is
cut deep enough so that over a small distance, there is an opening
14 which provides communication between the lumen 16 of the needle
and the zone defined by the notch.
The notch 12 is cut with the two notch walls at an angle of 90.degree.
to one another. The plane of each of the notch walls 18 20 are
at an angle of 45.degree. to the axis of the lumen 16. These two
wall faces 18 20 provide a relatively significant area to reflect
incidence of ultrasonic energy and thus create an ultrasonic echo
that can be received over a substantial area. It has an amplitude
significant enough to provide the desired image on an appropriate
monitor or other imaging device.
In addition, the opening 14 tends to permit a certain amount of
air to be trapped within the notch. Thus air, trapped as small bubbles
of air, causes a further significant ultrasonic reflection to the
sensor that substantially enhances the image as presented to the
In the FIG. 3 embodiment, notches 26 are cut to provide a first
notch wall 28 having an angle of 15.degree. with the lumen axis
and a second notch wall 30 having an angle of 75.degree. with the
lumen axis. The notch wall 30 faces proximally so that energy reflected
from the wall 30 will be directed toward an echo sensor transducer
placed near the hub of the needle.
The relative angles of the two notch wall faces may be established
as a function of the particular application of the invention and,
most significantly, as a function of the location of the sensor
that receives the ultrasonic echo.
It is believed that the larger the face of the notch wall that
looks back to the sensor, the more effective the invention will
be in providing a useful image to the physician. It could well be
that a curved notch wall would be effective providing that the surface
of the curvature defined by the notch wall intersects the axis of
the lumen at an acute angle; where the acute angle is sufficiently
small to assure a substantial reflecting wall surface that faces
toward the sensor being employed.
The position of the transducer and the direction of the sonar pulses
will not usually be uniquely determined with respect to the axis
of the needle. Accordingly, it is presently preferred to have the
walls of each of the two notches 18 and 20 to be at an angle of
45.degree. to the axis of the needle; in particular, one is at an
angle of plus 45.degree. and the other is at an angle of minus 45.degree..
This should provide the needle with the greatest range of reflection.
However, in order to increase the angles covered by the reflected
beams, it is contemplated that multiple notches might be employed
in which the angle of the sidewalls of the notches will differ from
notch to notch so that one sidewall may be at 15.degree. to the
axis, another at 30.degree. and another at 45.degree..
As shown in FIG. 5 a spring 34 placed between the hub 36 of the
needle and the hub 38 of a stylet 40 permits the stylet to be pumped
with finger pressure. The pumping motion will cause turbulence in
the fluid surrounding the needle which is immediately adjacent to
the notches thereby enhancing the image provided to the physician.
The opening 14 has the advantage of providing air bubbles. This
advantage may be further enhanced by removing and reinserting the
stylet 40 to thereby push trapped air into the notches.
The nature of the opening 14 is sufficiently small and can be made
sufficiently small so that liquid administered through the needle
or aspirated from the needle will not come through the opening 14.
This opening 14 provides the appreciable advantage of permitting
the trapping of air in the notch to enhance visibility without creating
any risk of compromising the performance of the needle.
It is generally desired to keep the circumferential arc of the
notches 12 26 to as little as possible to be consistent with providing
the small opening 14. In this fashion, the sidewall strength of
the needle is minimally compromised.
The circumferential arc over which the notch is cut is essentially
a function of the outer radius R of the needle and the wall thickness
T of the needle. A notch cut to communicate to the lumen is a function
of the ratio: (R-T)/R. Specifically, the circumferential arc that
provides a notch which just meets the lumen, is an angle that is
twice the angle having the cosine (R-T)/R. The bigger the wall thickness
T, the smaller the ratio and the bigger the angle having that cosine.
In formula terms, the circumferential arc angle "A" which
must be exceeded to communicate with the lumen is:
For example, a 22 gauge needle will have an O.D. of 28 mils (0.028
inches) and thus an R of 14 mils. It may have a wall thickness T
of 4 mils. This provides a ratio of (14-4)/14 which equals 0.7143.
The angle having a cosine of 0.7143 is about 44.5.degree.. Thus
the notch for such a needle will encompass an arc of needle circumference
greater than 89.degree.. Generally, the embodiments of this invention
will have notches that encompass less than 120.degree. of needle
circumference in order to insure communication with the lumen.
It may even be desirable to cut the notch with a laser beam so
as to provide a somewhat curved obliquely positioned notch in the
sidewall with an optimum trade-off of as much reflective surface
area as possible with as little needle strength compromised as possible.
Experimental needles having notches in accordance with the teachings
of this invention have been tested in a laboratory situation and
found to have sufficient rigidity so that the structural integrities
are not compromised by the notches. It is believed that any notch
which would extend close to 180.degree. around the circumference
of the sidewall would tend to reduce structural integrity.
As indicated above, by incorporating multiple air bubbles in the
notches, there would be a substantially expansion on the angles
covered by the reflective surfaces.
Although tests have been made showing the effectiveness of a needle
having the design shown herein, it is believed that it is the combination
of the angle or oblique sidewalls together with the air bubbles
in the notch that provide the highest enhancement of imagery.
As may be appreciated, for the reasons indicated above, the structure
of this invention provides an optimized trade-off of providing enhanced
echo image while minimizing degradation to either the structural
strength of the needle or the functional performance of the needle.
Although this invention has been described in connection with particular
embodiments, it should be understood that there would be variations
on the embodiment shown which would provide the advantage of the
invention that are included in the teachings herein.
For example, reference is made throughout the specification in
claims to a needle. However, it is conceivable that there may be
certain situations in which some cannula other than a needle would
advantageously employ the arrangement of this invention. It should
be understood herein that a needle is defined to include such cannulas.
Although the two notch walls are shown at an angle of 90.degree.
to one another, they need not be at 90.degree. to each other in
order to provide the effect of this invention. Nor, need the notch
wall angles equal one another. The angle of each of the two notch
walls to the lumen axis is selected to optimize reflecting ultrasonic
The preferred embodiments show communication of the notches 12
and lumen 16 through the opening 14. However, it is contemplated
that the notch itself, even if not cut through to the lumen, will
provide enhanced ultrasonic visibility because of the surface area
of the notches and the oblique angling of those surfaces.
The introduction of air into the notches 12 might be accomplished
by placing a diaphragm with a small hole in it over the entry to
the lumen at the hub. The physician could place a thumb on the hole
and pump air within the lumen into the notches.