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BACKGROUND OF THE INVENTION
(1) Field of the Invention
The invention relates to an endoscopic probe, in particular suitable for
use as a TEE probe.
(2) Brief Description of the Prior Art
An endoscopic probe is known from the article "An endoscopic
micromanipulator for multiplanar transesophageal imaging" by Roy W. Martin
et al. in Ultrasound in Med & Biol., Vol. 12, No. 12, pp. 965-975, 1986.
The known probe has a probe head with a slightly flattened part containing
an essentially flat transducer made up of a number of individual adjacent
elongated elements of piezoelectric material which can be excited
individually, and which together form a phased array. By exciting the
strip-type elements in a suitable sequence, it is possible to obtain a
beam which scans the environment to be examined and produces reflections
in a plane lying at right angles to the elongated elements, as described
in greater detail by J. C. Somer in "Echocardiography", N. Bom, published
by Martinus Nijhof in The Hague, 1977. Rotating the flexible tube, and
thus the probe head, about the longitudinal axis means that the
environment around the probe head can be scanned by an ultrasonic beam.
Pulling cables also extend through the flexible tube, by means of which
said head can be pulled forwards or backwards.
In the medical world there is a need for an endoscopic probe with which
more information can be obtained. In the past it was proposed that a
biplane TEE probe should be used for this purpose. Such a probe head has
two transducer arrays lying one after the other in the lengthwise
direction of the flexible tube and the head, each again composed of
adjacent elongated elements. The elements of one transducer extend at
right angles relative to the elements of the other transducer. With this
head it is therefore possible to obtain two scanning beams which can carry
out a scanning movement in directions extending at right angles to each
other.
A disadvantage of this known probe is that the scanning beams originate in
two different points. Another disadvantage is that the rigid head is
relatively long, which can lead to problems in practical use. Two separate
transducer arrays with the same definition per array also require twice
the number of control cables, which all have to be conveyed through the
flexible tube. However, the flexible tube has little or no space for
these.
In order to eliminate these problems, it was proposed in U.S. Pat. No.
4,543,960 that the transducer array should be fitted in the probe head so
that it is rotatable about an axis extending at right angles to the plane
of the array. For this, a transducer housing, bearing the transducer,
array and rotatable about a pin provided on the side of the transducer
housing facing away from the array, is fitted in a cavity in the probe
head. The elements of the transducer array are connected by means of
conductors formed on two flexible printed circuit boards to the different
cores of one or more electrical cables extending through the flexible
tube. The flexible printed circuit boards lie coiled around the transducer
housing.
It is not indicated in U.S. Pat. No. 4,543,960 whether, and if so in what
way, the cavity in which the transducer housing with the transducer is
situated is sealed off relative to the environment. A good seal with as
few seams and crevices as possible is, however, necessary from the point
of view of hygiene if the probe is intended for repeated use.
The object of the invention is therefore to provide an endoscopic probe
which meets the above mentioned requirement, and more generally to provide
a reliable endoscopic probe which is suitable for repeated use on
different patients, which is easy to clean externally, and by which the
human body can be examined internally by echography in the optimum manner.
SUMMARY OF THE INVENTION
For this, according to the invention an endoscopic probe of the
above-described type is characterised in that the cavity in the probe head
is sealed with an acoustically transparent head and the transducer is
coupled acoustically to the fixed cap by means of acoustic coupling means
which permit a rotation of the transducer relative to the fixed cap.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in greater detail below with reference to
the appended drawing of a number of examplary embodiments.
FIG. 1 shows schematically a cut-away top view of an examplary embodiment
of a probe head of a TEE probe according to the invention;
FIG. 2 shows schematically a cut-away side view of the probe head of FIG.
1;
FIG. 3 shows schematically a top view of the probe head of FIG. 1, in a
different working position;
FIG. 4 shows a detail of the probe of FIG. 1 and FIG. 2;
FIG. 5 is an example of a special printed circuit board which can be used
in a probe according to the invention;
FIG. 6 shows a modification of the printed circuit board of FIG. 5;
FIG. 7 shows schematically a first exemplary embodiment of a seal of the
probe head of a probe according to the invention: and
FIG. 8 shows schematically a second exemplary embodiment of a seal of a
probe head of a probe according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 1 to 3 show a TEE probe as an example of an embodiment of the
invention. A TEE (trans esophageal echocardiography) probe is a device
which can be used to examine the heart, or other parts of the body in the
region of the esophagus, by ultrasonic radiation from the esophagus
through the esophagus wall. The probe shown comprises a probe head 1 with
a housing 2, which connects to a flexible end part 3 of a flexible tube
which is not shown. Using Bowden cables 4, 5 extending through the
flexible tube, the probe head can be bent forwards (as shown in FIG. 2) or
backwards. This movement is made possible by the end part 3. If desired,
similar Bowden cables which permit a sideways swing of the probe head can
be present.
The housing 2 connects by means of a connecting piece 6 with round
cross-section to the end part 3 of the flexible tube, but itself has an
essentially rectangular cross-section with rounded edges which widens out
slightly to a holder 8 which is shut off at the free end by a semicircular
wall 7 and in which an ultrasonic transducer of the phased array type is
placed. The holder 8 is provided with a circular aperture 9 in an
essentially flat top wall. Situated in and behind the aperture is the
transducer which, as can be seen in FIG. 2, comprises an essentially flat
transducer 11 lying on a backing layer 10. The transducer 11 is made up of
a number of adjacent, but separate strip-type transducer elements which
can be for example, piezoelectric elements, and which in the situation
shown in FIG. 1 extend, parallel to the longitudinal axis H of the probe
head. The backing layer absorbs ultrasonic vibrations which are radiated
towards the interior of the probe head and which, if not absorbed, would
lead to disturbing reflections. The backing layer 10 is confined inside an
electrically insulating frame 12 which can be made of, for example, a
suitable plastic.
Above the array 11 is an acoustic lens 13, which will be described in
greater detail below. In a suitable manner phasedly exciting the
individual strip-type transducer elements makes it possible to obtain an
ultrasonic beam which can scan an area the shape of a sector of a circle
in a plane at right angles to the strip-type elements. This technique,
which is known per se, can therefore be used to scan the environment of
the probe head with a swinging beam, but the swing can take place in only
one plane.
The lens 13, the transducer 11, the frame 12 and the backing-layer 10 are
placed in a transducer housing 14 which is an essentially cylindrical
shape. The transducer housing 14 is sealed at the level of the aperture 9
by the lens 13, and in the example shown also has a bottom 15 which is
supported on a pin 16 fitted in a bore in the wall of the housing of the
probe head opposite the aperture 9. The central axis of the pin coincides
with the central axis H2 of the transducer housing and the centre point of
the circular opening lies on said central axis H2, so that the transducer
housing is rotatable about the pin. In the examplary embodiment shown, the
transducer housing is rotatable from the rest position shown in FIG. 1
both clockwise and anticlockwise through approximately 90 degrees. FIG. 3
shows the probe head with the transducer 11 rotated through 90 degrees.
The total rotation range is therefor 180 degrees, which means that a
spatial area the shape of a sector of a sphere can be scanned completely
with one and the same disc-type transducer made up of strips, without
changing the position of the probe head itself.
In order to make the transducer housing 14 rotate, a belt 17 is passed
around the transducer housing, the two free ends 18, 19 of which belt are
connected to pulling cables 20, 21. The pulling cables are again in the
form of Bowden cables, the outer cables of which are shown at 22, 23 The
belt 17 can be a spring steel belt which is connected at one point, for
example by a single spot weld, to the transducer housing 14. The
connection in the rest position is on or near the longitudinal axis H1 of
the probe head, as shown at 24 in FIG. 1, and FIG. 4.
All this is shown again in FIG. 4. An interposed metal strip is indicated
by 25 and is connected in a suitable manner to the transducer housing.
This prevents the pulling belt from slipping over the transducer housing.
For the electrical connection between the transducer elements and the
electrical cables passed through the flexible tube, use is made of a
flexible printed circuit board on which conductor tracks, connected at one
side to the individual transducer elements and at the other side to the
cores of the electric cable, are provided.
A number of cables are indicated by 30-33 in FIG. 1. The flexible printed
circuit board is indicated by 34, 35. The flexible printed circuit board
extends from a supporting plate 36 situated in the part of the probe head
1 connecting to the flexible tube and reaches into the transducer housing
14. For this purpose, the transducer housing is provided with a recess 37
extending through approximately 180 degrees along the periphery and being
the height of the width of the flexible printed circuit board. Fitted in
the transducer housing 14 under the backing layer are two pins 38, 39
which are fixed on the bottom 15 and/or in the backing layer 10. A strip
of the flexible printed circuit board is passed around each of the pins
38, 39. Each strip extends in a loop under the backing layer towards
connecting electrodes fitted on one end of the striptype transducer
elements. The flexible printed circuit boards thus do not take up any
space round the transducer housing.
In the examplary embodiment shown, the connecting electrodes for all
strip-type elements are on the front side of the probe head. It is,
however, also possible, for example, to fit the electrodes for the
even-numbered elements on the front side and the electrodes for the
odd-numbered elements on the opposite side of the transducer.
The pins 38, 39 are preferably placed in such a way that the flexible
printed circuit boards extend essentially through the axis of rotation H2
of the transducer housing not only in the rest position shown in FIG. 1,
but also on rotation of the transducer housing. Rotation of the transducer
housing 14 therefore does not lead to a change in the space required for
the flexible printed circuit boards. The parts of the flexible printed
circuit boards extending outside the transducer housing-change position
only to a very small extent during rotation of the transducer housing, as
can be seen from a comparison of FIGS. 1 and 3.
The pins 38, 39 can be positioned as shown on both sides of the
longitudinal axis H just past the centre line extending at right angles to
the longitudinal axis.
The supporting plate 36 in this example bears on both sides printed circuit
boards 43, 44 with conductor tracks to which the ends of the cables 30 to
33 are connected. The connecting point between the conductors of the
printed circuit boards 43, 44 and the conductors of the flexible printed
circuit board is indicated at 45.
FIG. 5 shows schematically a flat blank of a flexible printed circuit board
50 which can be used in the device described. The printed circuit board
shown has two wing strips 34, 35 which together form an approximately
V-shaped flat blank. Each wing 34, 35 has an elongated part 60, 61 which
has a first end 62, 63 for connection to the printed circuit boards 43,
44. Each wing also has a short transverse part 64, 65 which in the fitted
state rests against the frame 12 at the front side (in FIG. 1 or FIG. 2).
The transverse parts each have an end strip 66, 67. The end strips of the
two transverse parts are connected to each other at 68, and thus form the
connection between two wing strips. The end strips in the fitted state are
folded over approximately at right angles, and at the bottom side lie
against the connecting electrodes of the transducer elements. The
connecting electrodes can be, for example, gold electrodes, and the
connection can be made with conducting adhesive.
It is pointed out that the width of the elongated parts of the wing strips
of the flexible printed circuit board described together with the
thickness required for the backing layer largely determines the minimum
height of the probe head. According to a further development of the idea
of the invention, the elongated parts 60, 61 in the fitted state are
folded double about a fold line extending in the lengthwise direction.
An example of a flat blank for a flexible printed circuit board used for
this purpose is shown in FIG. 6. The conductor tracks extending in the
lengthwise direction of the elongated parts 60, 61 of the wing strips 34,
35 of the flexible printed circuit board are in each case divided into two
groups 70, 71 and 72, 73 lying on both sides of a fold line 74, 75. The
height required for the flexible printed circuit board is thereby greatly
reduced.
When a flexible printed circuit board with double-folded elongated parts of
the wing strips is used, if one or more printed circuit boards 43, 44 are
again used for the connecting elements between the flexible printed
circuit board and the cables 30 to 33, the printed circuit board 43 and/or
44 can be provided with conductor tracks on both sides. In this case each
side of a printed circuit board 43 or 44 can, for example, correspond to
one of the parts 70 to 73.
In principle, two (or more) individual flexible printed circuit boards
could also be used. The use of a single printed circuit board sides the
advantage that the position of the tracks, in particular in the end
strips, is determined accurately. With the correct selection of the
centre-to-centre distance of the tracks these can also be placed
accurately in line with the gold electrodes of the transducer elements
and, after correct positioning of a printed circuit board, a shifting of
any second printed circuit board cannot take place.
FIG. 7 shows schematically in longitudinal section a part of a probe head
of an endoscopic probe according to the invention. The ultrasonic
transducer 11 of the phased array type is shown. The transducer again lies
on the backing layer 10 which is situated inside the frame 12. The
transducer is connected in the manner already described at the front side
and at the bottom side to the end strip 67 of the transverse part 65 of
the flexible printed circuit board. An earth connection, connected at 80
to the top side of the transducer, is also shown.
A hard concave acoustic lens 81 which rotates along with the transducer is
fitted on the transducer and can be, for example, glued on the transducer.
The concave lens can be an acrylic lens or an anamorphotic type of lens
made of hard epoxy resin. The lengthwise direction of the cavity
corresponds to that of the individual elements of the transducer. The
cavity of the lens in the example shown is filled with a so-called flat
filler 82 which together with the lens forms a plane-parallel unit. The
use of a flat filler is not, however, strictly necessary. A suitable
screening foil, for example of aluminium capton.TM. (polyimide) can also
be placed between the flat filler and the concave acoustic lens. The lens
fits preferably in a sealing manner with its peripheral edge in the
aperture 9 of the probe head. If desired, the lens can be provided along
the peripheral edge with an O-ring, as indicated at 89. Fitted above the
lens in the aperture 9 is a ring 83, which is fixed in the aperture 9 in a
sealing manner, e.g. by gluing, as indicated at 84. An ultrasonic
sound-transmitting cap 85 is fitted, also in a sealing manner, in the ring
83. The cap 85 is preferably made of hard material such as methylpentene
copolymer silicone rubber, and in the example shown is glued to the ring
83, as indicated schematically at 86. The ring 83, which can be made of,
e.g. glass ceramic material, lies with the bottom axial plane against the
lens 81. Between the cap and the lens is a chamber 87 which along the
periphery is bounded by the ring 83 and which is filled with an
electrically non-conducting degassed fluid.
A groove 88, in which a sealing means is placed, is formed in the bottom
face of the ring 83. A rubber ring can be used as the sealing means, but
the groove 88 can also be filled with a suitable grease.
The axial seal can, if desired, also be supported by exerting a slight
spring pressure on the housing not shown in FIG. 7. For this, a spring
element can be fitted between the lower wall 15 (see FIG. 2) of the
housing 14 and the corresponding wall of the probe head, for example one
or more cup springs or a so-called sine spring.
The structure shown and described provides a completely closed probe head
without inconvenient seams or crevices which are difficult to clean, while
the transducer can still rotate freely, at least with little friction,
together with a lens about the axis of rotation H2.
FIG. 8 shows a variant of FIG. 7, in which a cap 90 is glued at 84 directly
in the aperture 9 without the interposition of a ring. A hard concave lens
91, which can be of the same type as the lens 81, and which is also
provided with a flat filler 92, lies against the bottom side of the cap
90.
The fixed cap and the probe head, at least the front part thereof, can be
made of the same material and can then be made, for example, of one piece.
Between the cap 90 and the lens 91 a capillary gap is present, in which a
liquid for reducing the friction, e.g. coupling oil, is present. Through
the capillary action of the gap, the coupling oil does not flow away. If
desired, an additional axial and/or radial seal can, however be used with
the aid of O-rings and or with a grease-filled groove, as shown in FIG. 7.
The lens can again be made of perspex or a hard epoxy resin. Like the cap
85 of FIG. 7, the cap 90 can preferably be made of a mechanically sturdy,
but in acoustic respects aqueous material, so that in acoustic respects a
good adjustment to human tissue is obtained. Suitable materials are e.g.
methylpentene copolymers.
In the examplary embodiment shown in FIG. 8 also, the housing 14 can again
if desired be under a slight upward pre-tension, so that the lens is held
against the cap in all circumstances.
It is pointed out that, after the above, various modifications are obvious
for the expert. For example, instead of the belt 17 a circular pulling
cable, provided with a nipple falling into a cavity of the transducer
housing, can be used. The belt 17 could also be replaced by yet another
transmission mechanism such as a toothed rack which can be shifted by a
pulling cable in the lengthwise direction, and which engages on a toothed
wheel coupled directly or indirectly to the transducer housing. In that
case it would be possible to make do with one pulling cable. Springs,
which press the transducer housing back to a predetermined rest position
can also be used.
Instead of a single flexible printed circuit board, as already stated, two
or more flexible-printed circuit boards or one or more bunches of wires
connected between the connectors 40, 41 and to the cables 30 to 33 could
be used.
The belt 17 can also be made narrower and is preferably slightly recessed
in a groove in the transducer housing.
The transducer, which in the example shown is essentially flat and
hexagonal, can also be, for example, round or rectangular and slightly
convex or even concave.
It is also pointed out that the probe described can also in principle be
used for examination through body cavities other than the esophagus.
These and similar modifications are considered to fall within the scope of
the invention.
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