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BACKGROUND OF THE INVENTION
The present invention relates to the locating of concrements in the body of
living beings for purposes of determining where the focal point of a shock
wave reflector right has to be positioned so that it may comminute the
concrement, and more particularly the invention relates to a system for
locating concrements under utilization of X-rays in combination with an
ultrasonic device.
German patent No. 23 512 47, see also U.S. pat. No. 3,942,531, discloses a
device for the comminution of concrements inside the body of a living
being, under utilization of a focusing chamber which is a portion of a
rotational ellipsoid, having two focal points. In one focal point a spark
discharge produces a highly concentrated point like shock wave which
propagates in all directions, is reflected by the focusing chamber and
refocused in the second focal point of this ellipsoid. That second point
must be positioned such that it coincides with the concrement. The
comminution of kidney stones without operative invasion and without
introduction of probes or the like into the body has been successfully
practiced with this technique. An extensive description of equipment and
therapeutic procedure is for example found in "Extra corporal shock wave
lithotripsy", Ch. Chaussy ed Munich 1982.
Before this shock wave comminution process can take place, it is necessary
to very accurately determine the location of, for example, the kidney
stone, so that the focusing chamber can be positioned for purposes of
having its second focal point as defined above coincide with the kidney
stone. For this one has used for example two X-ray systems, which operate
basically, on the principle of triangulation and are oriented to obtain
particular axes of observation that will pass through the concrement and
from the orientation of the X-ray system and their respective axes one can
then determine the location of the kidney stone vis-a-vis the X-ray
system. The focusing chamber is then positioned accordingly.
Obviously intensive exposure of the patient to X-rays have to be avoided so
that the number of X-ray images taken should be limited Nevertheless, the
known locating method is tied to two X-ray systems. Following the locating
of the kidney stone which in turn is followed by positioning of the
focusing chamber, the kidney stone is comminuted by the shock waves to
obtain a very fine grit, which is discharged from the body by natural
process.
The German patent No. 27 22 252, suggests a device for locating concrements
by means of ultrasonics. Satisfactory results for this approach
presupposes that the stone and the organs around it have a fixed, resting
position. However certain inherent motion of the stone and of the organ in
which the stone is lodged, for example on account of breathing will cause
the stone to move in and out of the plane of ultrasonic locating.
Therefore, the ultrasonic image will change continuously and the stone can
be identified only for a very short period of time, namely when it passes
through the locating plane to which the ultrasonic imaging system
adjusted.
As the focusing chamber is positioned so that its second focal point as
mentioned above, is made to coincide with a point in the imaging plane,
super imposed oscillatory motion of the stone, may in fact destroy the
locational information about the position of the stone and the entire
locating procedure may have to be repeated. This process is particularly
time consuming if the positioning of the concrement, for example by
shifting the patient in relation to a particularly adjusted and positioned
focusing chamber is carried out independently from the concrement locating
device, i.e. if there is no follow-up control involved. A more suitable
tracking device is suggested by one of us and others of copending patent
application now issued as U.S. Pat. No. 4,669,483.
DESCRIPTION OF THE INVENTION
It is an object of the present invention to provide a new and improved
method and equipment for locating concrements in a body of a living being,
in preparation of a comminution process using focused shock waves whereby
the locating of the concrement should be carried with certainty so that
the concrement can be placed with certainty and in a simple fast and
reliable manner into the one focal point of the reflector and maintaining
that adjusted position.
In accordance with the preferred embodiment of the invention it is
suggested to use two imaging systems for locating a concrement one being
an X-ray system, and the other one an ultrasonic imaging equipment and to
correlate the images such that a common dimension appears on the imaging
screens, or can be made by way of adjustment to so appear. Preferably the
adjustment is made such that any oscillatory movement of the concrement
occurs in one line or one image and in the display plane (screen) of the
other image. Generally speaking each image screen should have visible at
least one reference point or points. In the example explained with
reference to the drawings, the center of the X-ray screen and the center
on the ultrasonic screens are such reference points.
The inventive correlation of the two different locating systems two imaging
screens permit the rapid detection of a concrement at a higher degree of
certainty with regard to recognition, as well as simple observation of the
displacement excursions the concrement undertakes on account of breathing
by the patient. The correlation of the two locating systems in relation to
the positioning permits in fact a rapid follow-up and tracking of the
concrement so as to maintain it in the focal area of the shock wave
generator. The follow-up may be carried out by the operating personnel or
automatically through automated image processing, for example under
utilization of an interactive screen system. The utilization of at least
one ultrasonic locating system permits in particular the monitoring of the
movement of the concrement in real time and without any undue radiation
load. The shock waves can always be triggered whenever the stone does in
fact pass through the focus on account of the breathing by the patient,
which imparts the displacing oscillatory motion upon the stone. Obviously,
this increases the efficiency of the comminution and is beneficial for the
patient, also the total treatment time is shorter and the use life of the
sparking equipment is extended.
The combination of an ultrasonic system with an X-ray system in accordance
with the invention, combines the advantages of ultrasonics, namely no
damage to the patient, with advantages of X-ray's high resolution. The
combination actually is quite ideal, particularly in view of kidney stone
comminution but also gall stone comminution. In the case of a kidney stone
comminution, the advantages of X-ray become noticeable, particularly upon
evaluation the sequence of treatment and its success and while the
ultrasonic approach is used only for determining the depth and position of
the concrement.
In the case of gall stone comminution however, X-rays are used primarily
for preorienting and to generally find the position of a stone in order to
find an optimum section plane, so that now the advantages of ultrasonic
can be used to the fullest. It is possible for example to use the X-ray
system as an aid in the orientation of the ultrasonic locating system, B
scan. A single X-ray system generally will find only two out of three
spatial coordinates of the target. The X-ray image plane and the
ultrasonic image plane are preferably arranged at right angles to each
other to thereby determine the missing third coordinate of the X-ray from
the ultrasonic image.
Both systems moreover are arranged such that they establish a
representation for the second focal point of the ellipsoid (the first one
is the one, in which the spark is produced). In cases with insufficient
certainty about concrement recognition, one can use the X-ray locating
procedure for controlling the two out of three coordinates which of course
increases the certainty of recognition, or it is used primarily for
preadjusting the concrement in two dimensions and permits thereafter a
simpler and faster recognition of the third coordinate under utilization
of the ultrasonic system, to thereby determine this third coordinate for
purposes of positioning the focusing device.
Any periodic movements of the concrement, primarily induced by breathing,
can be observed in real time on the ultrasonic image. For better tracing
of such periodic movements one should provide the ultrasonic system such
that it can turn about an axis which runs through the center of the
ultrasonic oscillator itself as well as the focal point F2, this is also
called a Uo axis. As soon as the positioning is carried out in the stated
manner, a simple axial turning of the ultrasonic oscillator under
observation of the ultrasonic image permits orienting the ultrasonic image
plane parallel to the main axis and direction of oscillation of this
particularly moving target. This way one can operate without complex
variable coordinate transformation and still obtain a reliable target
acquisition in real time.
In a particular embodiment of practicing the invention, it is conceivable
to provide the ultrasonic system so as to rotate the detection plane about
two axes. Each rotation and rotational adjustment permits separate
adjustment such that the oscillation occurs within the plane. The
oscillator can thus be observed from different angles. In each case
therefore the stone is permanently on the ultrasonic image screen.
To have these two different situations available is representable by
different images for each of these two different rotations. The advantage
here is that in fact the stone becomes visible from different sides, and
its volume can therefore be calculated by means of an online calculator,
which is important information concerning accurate metering the shock wave
energy to be produced.
In a particular embodiment of the invention it is suggested to correlate
the positioning of the shockwave generator with the two locating systems.
This, for example, is obtained in that two coordinate directions are
caused to coincide with the ultrasonic imaging and detection plane and the
third coordinate is then at least approximately perpendicularly thereto.
By moving the patient in the direction of that third coordinate, the
target, i.e. the concrement will appear or disappear within the ultrasonic
image field, and with the aid of the two coordinates being visible as such
in the imaging plane of the ultrasonic monitoring screen, the particular
location of the concrement in that plane can easily be ascertained. Since
now only correction in the direction of these two image field coordinates
are necessary, the target is continuously visible and will not move out of
the field of view accidentally. This means that the locating process is
quite a speedy one. The locating procedure can be carried out considerably
faster and in real time and particularly larger correction can be provided
in coarse step for example through push button advance still remaining
fully under control, either by an operator or by automated equipment.
The shifting of the ultrasonic section plane may be automated, also, under
utilization of a computer. Evaluation in this case, may for example be
carried out through an interactive imaging screen, using for example a
light pen, the attending physician uses to point to the location of the
stone, and the positioning equipment will then automatically move for
example the patient or the patient rest so that the stone appears in the
center of the . image screen with oscillations occurring within the
imaging plane of the ultrasonic equipment. Alternatively the initial
location of the stone on the screen can be read through proper scales and
these coordinate values are then keyed into the calculator.
The most important aspect is that the invention reliably prevents that the
target appearing in the ultrasonic image screen will in fact escape so
that another time consuming search process has to begin. This mishap does
occur in uncorrelated system. The danger of unintended escape of the
target (concrement) from the screen in previous locating equipments was
specifically due to the fact that the ultrasonic image so to speak depicts
only a thin slice from the object field, and that a representation of the
target is possible only if the target is in some form correctly placed
within the coordinate system that is inherit in the ultrasonic system. In
the case the coordinate system for the patient positioning and the
coordinate system for the ultrasonic imaging are rotated in relation to
each other any position correction may cause the image of the concrement
to move in the sense that if a correction that is carried out in one
coordinate system may lead to an escape of the image from an ascertained
position in the other coordinate system.
Generally speaking one uses two imaging systems with image planes that are
oriented perpendicular to each other. In furtherance of the invention one
may use two ultrasonic systems. This is advantageous if one wishes to
track the concrement movement fully through automated follow-up control
and this can be carried out in fact in real time. In this case, the
located concrement will appear in both ultrasonic images, which means that
two out of three coordinate systems are in fact represented in each of the
ultrasonic systems. For example X and Y appear in system 1, Y and Z in
system 2. From the real time ultrasonic images now all requisite
corrections are directly ascertainable to provide follow-up control input
signal in real time whereby for example the direction of movement n three
coordinates, the speed and the acceleration are sufficiently fast detected
to permit tracking of the relatively slowly moving concrement. Servo
motors provide in effect correction of the concrement position, so that
the concrement is in fact maintained in the second focus of the shock wave
focusing and generating device. The ascertaining of corrective data in
respective two coordinates such as X, Y in system 1, can be carried out in
different ways, for example by means of image storage facilities;
correlation techniques, or by means of an automatic symbol recognition
device or through application of separate position 1 for each ultrasonic
system. This last 1 possibility is particularly simple, because such
position detectors are commercially available, and a movement of a defined
image point in two dimension can be acquired by these position detectors
as to direction, speed and acceleration. In connection with two ultrasonic
systems then one has therefore available all the requisite data for
correction. Finally it should be mentioned that a real time position
correction is possible for kidney stone comminution, as well as for gall
stone comminution.
DESCRIPTION OF THE DRAWINGS
While the specification concludes with claims, particularly pointing out
and 2 claiming the subject matter which is regarded as the invention, it
is believed that the invention, the objects and features of the invention,
and further objects, features and advantages thereof, will be better
understood from the following description taken in connection with the
accompanying drawings in which:
FIG. 1 is a somewhat schematic view of a system in accordance with the
preferred embodiment of the present invention for practicing the best mode
thereof; and
FIGS. 2, 3 and 4 are different X-ray and ultrasonic images for respective
three different situations as they arise during locating and positioning
of a concrement that moves in the body of a living being on account of
breathing.
Proceeding now to the detailed description of the drawings, FIG. 1
illustrates somewhat 2 and in cross section the body 2 of a patient and
reference numeral 4 denotes a concrement to be comminuted. Also
schematically shown is a shock wave reflector 6, of the type mentioned
above, having a first focal point F1, in which is situated the source of
shock waves. In other words spark discharges are produced in the focal
point F1, and are reflected and refocused by the reflector 6 in the second
focal point F2. The ultimate objective is the preparation phase for making
the concrement 4 coincide with that second focal point F2. Not shown in
the drawings are devices for relatively shifting and positioning the
patient body 2 vis-a-vis the reflector 6, it does not make any difference
in principle which (or who) is being moved, but for practical purposes,
one usually has the equipment 6 fixed and the body 2 is situated on a
suitable rest and the rest as a whole or portions of the rest are being
shifted for positioning the patient body in particular relation to the
reflector 6. The movement can be carried out manually. Also not shown are
structure for coupling and/or introducing the shock wave energy into the
body. Generally speaking it is advisable to have the focal chamber filled
with liquids, such as water and to provide in some form a water coupling
path between the device 6 and the body of the patient.
The inventive locating system is comprised of an X-ray locating system
including an X-ray tube 8 and an X-ray image receiver and amplifier 10,
being connected to an X-ray image monitor 12. The second locating system
is an ultrasonic system comprised of an ultrasonic transducer, i.e.
emitter/receiver head 14, being connected to an ultrasonic imaging monitor
and screen 16, responding to the return and reflection of ultrasonic
waves.
The correlation between the two monitors and indicators 12 and 16 is
denoted symbolically by the connection 20 and correlation can be
automated, but does not have to; the operative correlation can be provided
by an attending physician or technician. Decisive for the invention are
the facilities that permit correlation. FIG. 1 also contains in
superimposed relationship an alternative configuration using a correlation
computer or calculator 22, the output of which runs to adjusting motors
for the positioning device of the patient and his other rest as was
outlined above. The correlative procedure can thus be automated. In case
one uses a calculator 22, the coordinates are determined through a
scanning process of the two screens 12 and 16 i.e. of its information
content. Thus scanning may be a purely electrical one, involving amplitude
proceedings of the signals that are used to control and determine the
respective images.
In case of an error for example, it can be calculated whether or not the
positioning data are compatible, because two coordinate of the ultrasonic
system and two coordinates of the X-ray system together are redundant for
determining the three coordinates of the concrements. Therefore it is
quite possible to calculate whether or not the coordinate values as
provided in each of the two scanning systems are compatible with the
respective other one.
As far as the locating and positioning procedures are concerned, the
ultimate objective can be defined as follows: The reflector (6) axis is
defined by a line through the two focal points F1 and F2, the center line
18 of the X-ray beam and the center line U O of the ultrasonic
intersection plane bounded by U1 and U2 are supposed to intersect right in
focal point F2. However, all these three axes do not have to be situated
in a common plane; it is merely required that they intersect and, of
course, the concrement 4 has to be right in that point of intersection.
The ultrasonic sensor 14 being for example of the sector scan variety, or
having as a pick-up an array of ultrasonic transducers is provided to
obtain a two-dimensional image, generally known from medical diagnostics
as a B-scan. The ultrasonic system produces a range image by processing
and evaluating transit time of individual beams and transit time
differences. For this, a particular locating or section plane is scanned
being in effect limited by the beam U1 and U2. The screen 16 in FIG. 1
illustrates schematically the scanned plane as bounded by U1 and U2. The
axis Uo runs centrally in that plane. The screen 16 illustrates somewhat
schematically this particular scanning plane portion bounded by U1 and U2,
therefore what is imaged on the screen is a top elevation, which in this
case, is assumed to hold the concrement or stone 4.
The ultrasonic system is particularly adjusted such that the central beam
18, of the X-ray system runs in that plane, bounded otherwise by U1 and
U2. The center beam 18 of the X ray system is of course adjusted to
coincide with and run through the located concrement. This is particularly
illustrated in the screen picture of screen 12. One can also say that the
search for a concrement begins by this X-ray locating operation and the
first 4 in the composite locating and adjusting and positioning procedure
is to center the X-ray equipment vis-a-vis the patient such that the
concrement 4 appears in the middle of the screen 12. There may be a
suitable cross on the screen for obtaining manually this adjustment. The
screens 12 and 16 show the image correlation of concrement 4; it just be
on the center of either screen. This establishes the relative position of
the two locating systems. The focusing and shock wave producing device 6
must now be positioned that its focal point F2 coincides with the
adjustment center of the imaging devices which coincide with the
concrement. Procedure is explained in the above identified copending
application. From a different point of view, one can see that each of the
video screens depict a two dimensional representation. This means that one
dimension is redundant and this fact is used for purposes of correlating
the two images (or the video signal, representing these images. In FIG. 1
(and the others) the common dimension runs along line U o.
The ultrasonic transducer head 14 should be arranged to avoid damage from
the shock wave generator, therefore the head 14 should be placed, so to
speak, in the shadow of the reflector and shock wave generator 6. The
ultrasonic equipment is now adjusted so that likewise the concrement image
appears in the center of monitor screen 16. The ultrasonic imaging plane
is superimposed in sections on the X-ray monitor screen 12.
FIGS. 2, 3 and 4 illustrate three different situations of locating a
concrement. FIG. 2 is basically similar to the situation, used as a
representation for images in FIG. 1, except that it is now assumed that
the concrement moves on account of breathing which movement will occur
visible on the X-ray screen 12, as well as on the ultrasonic screen 16.
The concrement 4 in particular moves back and forth within the plane
bounded by lines U1, U2 from position A to position A' and back. It is
assumed moreover, that a translatory movement can be provided to move the
stone from A to B. This would mean that its oscillatory motion from B to
B' runs through the focal point F2. In order to avoid undue X-ray load,
the movement of the image of the concrement can be observed by the
ultrasonic equipment. The image of the concrement will remain visible on
the X-ray screen, but that is redundant so that the X-ray equipment can be
switched off.
In FIG. 3, the lefthand portion illustrates that the concrement oscillates
on account of breathing through the focal point but the excursions runs
between positions above and below the ultrasonic detection plane. In the
ultrasonic image as per screen 16, one will simply see briefly the stone
image appear and disappear again. The X-ray equipment will show these
excursions, but the objective is to reduce X-ray exposure time.
If now the ultrasonic head 14 is rotated about the axis Uo and by the angle
visible initially on the X-ray screen 12, one will now cause the
concrement to oscillate within the ultrasonic detection plane which is
beneficial twofold. Once the oscillation of the concrement in the X-ray
screen does no longer move at an angle to the ultrasonic section and
detection plane, but its movement coincides therewith, the ultrasonic
image of the conrement will not longer appear and disappear on screen 16,
but remain permanently visible and oscillates just analogous to the
situation shown in FIG. 2. As stated this redundancy of detection is not
necessary, which means that the X-ray equipment can be turned off, in
order to remove the X-ray load from the patient, one simply has to observe
the appearance and disappearance of the ultrasonic image of the concrement
Q on the ultrasonic screen 16. Upon rotating the ultrasonic plane, the
concrement should permanently appear visible on screen 16 in one adjusting
position of ultrasonic section plane rotation and once this has been
achieved, the locating procedure is completed. Conceivable a lateral
translatory motion has to be provided in addition which is analogous to
the situation explained with reference to FIG. 2. In other words FIG. 3
and 2 represent sequential operations in some case.
The example shown in FIG. 4, it can be regarded as the general case, which
means that initially the stone is not visible at all on the ultrasonic
image screen. The X-ray screen shows that the stone oscillates between
positions C and C' both outside and on one side of the ultrasonic
detection and section plane. The patient will now be moved translatorily
until the stone oscillates through the ultrasonic plane, which occurs by
shifting from C to D. This then establishes the situation explained above
with reference to FIG. 3. After rotating the ultrasonic image plane and
after another translatory shift (FIG. 2) the oscillation passes through
the focal point F2.
It should be noted that the ultrasonic plane is either rotated about the
axis 18 or analogously to FIG. 3, about the axis Uo. Until the oscillation
occurs fully in the ultrasonic plane. Further procedure is thus carried
out just as described earlier with reference to the other figures. It
should be noted, that this explanation given here of the adjustment
operations can be carried out manually but in view of the particular
definitiveness of image representation, automatic video signal scanning
can be employed, in other words the oscillatory motion and the particular
location of that motion of the concrement can readily be acquired through
a data process input structure, so that objective data are available,
which in turn permit the patient to be automatically positioned until the
desired situation, as depicted in FIG. 1 is maintained.
The invention is not limited to the embodiments described above, but all
changes and modifications thereof, not constituting departures from the
spirit and scope of the invention, are intended to be included.
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