Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~;~32053
1 STAND-OFF CELL FOR AN ULTRASONIC SCANNER HEAD.
The invention relates to a stand-off cell for an us-
trasonic scanner head which stand-off cell is mounted
so that it can be disconnected, on the scanner head
by a clutch facing and is in contact with the patient
through a contact surface and which furthermore has a
number of free surfaces.
In medical diagnostics one is often interested in
making a so-called biopsy. I.e. that one by means of
a needle takes a sample from the patient. The placing
of the needle is often critical, wherefore one is
interested in being able to determine this exactly.
This applies for example when taking samples of the
amniotic fluid.
The supervision of the placing of the needle has been
tried by means of ultrasonic scanning where emitted
ultrasonic impulses are reflected from the needle and
its surroundings and are used for making pictures
i.e. by means of a micro computer and a cathode ray
tube.
Ordinary scanner heads consist of a row of transducer
elements placed in line. As an example one can mention
the scanner head which is described in US Patent
Specification No. 4.346.717. Such scanner heads have
the drawback, when used for biopsy that one cannot
supervise the first 20-50 mm of the area into which
the needle is introduced. This is due to the fact
that the needle first has to be lead diagonally in
1~:3~ 3
under the scanner head before it gets into its super-
vision area.
In order to avoid this drawback it is known to
use special biopsy heads. They consist of an ordinary
linear scanner head through which a canal for intro-
during the needle has been made. However, in order to
make room for this canal one has to remove a number
of transducer elements in the center of the head.
This creates an area that the scanner head is unable
to supervise and this will often be inconvenient
when introducing the needle. These special biopsy
heads furthermore have the drawback that they are
very expensive. The even cost more than a normal
scanner head.
If one wishes to supervise an area ultrasonically,
which area lies close to the surface of the body, it
is furthermore known to use a spacer unit between the
scanner itself and the body.
The aim of the invention is to disclose a stand-off
cell for a conventional scanner head so that this will
be capable of supervising the whole course of the
needle in the patient at a biopsy and this is accord
ding to the invention achieved in that the stand-off
cell is provided with a slit for engaging a needle
or a hypodermic needle and that the slit extends be-
tweet the contact surface and one of the free surf-
cues.
~;~320S3
1 As the stand-off cell is made of a material with at-
most the same acoustic impedance as tissue it will be
possible to register the whole course of the needle
"through" this. Due to the slit the needle will first
penetrate into the patient in a place which lies
within the supervision area of the scanner head. In
that the needle is placed in a slit it is further-
more achieved that the scanner head with the stand-
off cell can be removed from the needle without put-
lying the needle out of the patient. This makes it posy
sidle to perform an easier biopsy just as it makes
it possible to utilize the scanner head better. This
is now only used during the placing of the needle
itself. The stand-off cell can in a simple manner be
made of a suitable plastics, and will therefore be
very cheap. Thus it becomes possible to be free to
dispose of a suitable number of stand-off cells
which makes it possible to use any scanner head
optimum for many different purposes.
A stand-off cell according to the invention is
characteristic in that the contact surface is penal-
lot with the clutch facing. For many purposes this is
a suitable and very simple execution of a stand-off
cell.
If the stand-off cell, as dealt with in claim 3, has
one or more reflection surfaces it becomes possible
to make stand-off cells where the ultrasonic wave
course is "broken" inside the stand-off cell. This
can be convenient where the biopsy has to be made in
places not very accessible.
A stand-off cell according to the invention can be,
~23;;~1)53
1 as dealt with in claim 4, characteristic in that the
contact surface stands at right angles to the clutch
facing. If the ultrasonic waves are now sent horizon-
tally against a reflection surface, which makes up an
angle of 45 at the contact surface, a 90 deflection
of the ultrasonic waves is obtained. Thus it becomes
possible to introduce a needle in the center of an
ultrasonic field under a large number of angles, and
for example also at a right angle to the contact sun-
face.
By mounting a guide organ, as dealt with on claim inn front of the needle a good control of this is ox-
twined.
By the in claim 6 referred to guide organs which can
be disconnected Andre adjustable it is obtained that
the needle easily can be placed in well-defined angles
in proportion to the contact surface, and that the
stand-off cell in a simple manner can be removed from
the needle.
It may be expedient as mentioned in claim 7 to make
the slit in a needle-guide organ which is secured to
the stand-off cell so that it can be disconnected, as
the scanner head 6 itself with the stand-off cell that
can easily be removed from the needle and the needle-
guide organ.
The invention will in the following be described more
closely with a reference to the drawing, where
fig. 1 shows a scanner head with a stand-off
cell according to the invention seen in
section,
~23%C)~3
1 fig. 2 shows a stand-off cell according to the
invention with guide organs for the
needle,
fig, 3 shows a second embodiment for a stand-off
cell according to the invention,
fig. 4 shows another embodiment for the invent
lion,
fig. 5 shows an embodiment for the invention,
where the scanner head forms an angle of
45 with the contact surface,
fig. 6 shows another embodiment for the invent
lion, and
fig. 7 shows a needle-guide organ seen in sea-
lion along the line VII-VII on fig. 6.
On fig. 1 an ordinary scanner head 1 is seen. To this
there is attached a stand-off cell 2 according to the
invention at the clutch facing 5. Between the stand-
off cell 2 and the scanner head 1 a thin layer of a
suitable paste has been put, which ensures a good
acoustic clutching between the parts. The same paste
can suitably be used between the stand-off cell 2 and
the patient.
The stand-off cell 2 is made of a plastics with an
acoustic impedance, which essentially is the same as
that of the patient's tissue. The plastics must
furthermore have a poor damping of the ultrasonic
waves. It has thus turned out that elastic materials
123~0S3
1 often have a too large damping of the ultrasonic waves
wherefore the stand-off cell can be made of a possibly
liquid-filled plastics. So one can obtain an efficient
transmission of acoustic energy without inconvenient
reflections at the transition between the surfaces.
The biopsy needle 4 is lead through the slit 3 which
is designed between the free side face 9 and the
contact surface 7. As can be seen from fig. 1 the
needle first enters the patient in the supervision
area of the scanner head which is defined by the
lines 8 and 8' on fig. 1. The slit 3 furthermore sup-
ports the needle 4 during its introduction into the
patient. When the needle 4 is fully introduced one
can without further measures remove the scanner head
1 and the stand-off cell 2 as the needle can be no-
moved through the slit.
The shape of the stand-off cell can be very simple,
which makes a very cheap production of it possible,
e.g. by machining processes. Moreover, it will be Sims
pie to produce stand-off cells for any conceivable
scanner head.
On fig. 2 it can be seen how a stand-off cell 2
according to the invention can be supplied with
needle-guide organs 10. These can e.g. consist of a
tube with a strap for supporting the needle. Hereby
a very safe guiding of the biopsy needle is made posy
Sibley The guide organs 10 can be adjustable at
various angles with the contact surface, and can of
course be made in many other ways than the one shown
here. If the needle-guide organs 10 are connected to
the stand-off cell 2 in such a manner that they can
be released, said stand-off cell will be capable of
~Z321~S3
1 being released for other use without removing the
biopsy needle from the patient.
On fig. 3 a stand-off cell is seen, where the contact
surface 7 and the clutch facing 5 stand at right an-
lies to each other.
With different presentation of the slit 3 a large
area of variation can be obtained for the angle of the
needle by the patient. As the acoustic impedance in
air is very different to the acoustic impedance in
the stand-off cell, an area, which is turned horizon-
tally against the clutch facing 5 will be deflected
90 of the reflection surface 11. The ultrasonic area
will thus be directed vertically down into the pat-
tent and it becomes possible to lead the needle Yen-
tidally down in the center of the sound area. This
gives a very precise and efficient control of the
needle, and at the same time this embodiment is very
material saving.
On fig. 4 and 5 stand-off cells 2 are seen where the
sound area is reflected one or a number of times at
the reflection surfaces 12, 13 and 14. It is simple
to manufacture such reflection surfaces as they can
consist of surfaces for air chambers, openings or
metal surfaces. The difference of the acoustic imp
penance will so ensure total reflection. One can thus
manufacture special stand-off cells for places that
are difficult to reach or where accuracy is portico-
laxly important. It also becomes possible to give the
area a favorable direction and to let the needle 4
follow this.
12320S3
1 On fig. 6 and 7 it is seen how the needle can be
lead in a needle-guide organ 15, which is secured
to the stand-off cell 2 by means of taps or six
miter mounting means, which can be disconnected.
If it is necessary or required to use a sterile
cover of the stand-off cell 2, said stand-off cell
can be placed inside a thin sterile latex casing or
the like, after which the needle-guide organ 15 can
be mounted at the outside of the casing and be fixed
to said casing.
Hereafter the hypodermic needle can be operated
in a sterile way apart from the stand-off cell it-
self without any risk of transmission of infections the casing can be removed and replaced by a new
one before being used next time.
The stand-off cell according to the invention may
possibly be made in innumerable ways according to
the task the stand-off cell to be used is to per-
form. The stand-off cell can also easily be adjusted
to any scanner head. Thus, it will be possible for
a hospital ward to own a large number of scanner
heads so that every biopsy can be done quickly and
precisely and with a minimum of malaise and risk for
the patient.
Finally, it can be added that one could also make use
of the fact that the ultrasonic waves at the transit
lion between the stand-off cell and the patient will
change course - be refracted - due to the difference
in acoustic impedance between the stand-off cell and
the tissue. This refraction can be used in such a way
~Z3ZOS3
1 that the transducer itself can form an angle which
is different from ~0 with the patient's skin even
if one wishes the ultrasonic waves to penetrate
fairly perpendicular into the patient.
Hereby, it becomes possible to lead a hypodermic
needle into the patient precisely in the center of
the sound area without the needle having to pass
through the transducer itself and thus disturb the
picture.
