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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a therapy apparatus for treating a
patient with focused acoustic waves.
2. Description of the Prior Art
Therapy systems which employ acoustic waves are utilized, for example, for
treating stone complaints (lithotripsy), tumors and bone pathologies
(osteorestoration). These therapy systems usually are in the form of
completely equipped work stations which, in addition to comprising a
source of focused acoustic waves with application means for introducing
the generated acoustic waves into a patient to be treated, include a
locating system and a patient supporting device, whereby the source and
the patient supporting device are adjustable relative to one another.
During the treatment, the region of the patient to be treated is first
localized with the locating system, and the region to be treated is then
positioned by adjusting the patient supporting device with the patient
thereon and the source relative to one another so that this region is
situated in the focus of the acoustic waves. The region to be treated is
then charged with acoustic waves in the required way. Although therapy
systems having a locating system functioning exclusively on the basis of
ultrasound are suitable and are frequently used, therapy systems are
normally preferred that have an x-ray locating system, since it is
desirable in nearly all applications (and indispensable in many
applications) to be able to locate a region to be treated with
x-radiation. Some therapy systems have an x-ray locating system, in
addition to an ultrasound locating system, since the latter is capable of
supplying additional information.
Therapy systems having an x-ray locating system are extremely expensive.
This does not represent a disadvantage when the clinic in which the
therapy system is operated has an adequately large number of patients in
order to enable an economical operation of the therapy system. In the
interests of the patient, however, it would be desirable to be able to
have a high-performance therapy system of the type described above in
smaller clinics or in a doctors's office as well. In the case of a therapy
system equipped with an x-ray locating device, however, the comparatively
high price thereof does not allow an economical utilization of the therapy
system under those conditions.
SUMMARY OF THE INVENTION
An object of the present invention is to offer a simple and economic
therapy system that allows a high-grade work station with x-ray locating
to be installed in small clinics and potentially even in doctors' offices.
This object is achieved in accordance with the principles of the present
invention in a therapy system for treating a patient with focused acoustic
waves having a source of focused acoustic waves with which the focused
acoustic waves can be introduced into an acoustic propagation medium,
these waves converging in a focus lying on the acoustic axis of the
source, the source having an x-ray-transparent region through which the
acoustic axis of the source proceeds; application means for introducing
the focused acoustic waves generated with the source into a patient to be
treated; an x-ray impermeable mark arranged on the acoustic axis; and
acoustic means for identifying the distance of a region to be treated with
focused acoustic waves from the source.
The invention is based on the assumption that an x-ray device having a
patient support table, adjustable at least in a plane intersecting the
central ray of the x-ray emission at a right angle, but preferably fully
spatially adjustable is present in all smaller clinics and even often in
doctors' offices, or at least a simple x-ray device, for example a C-arm
device, and a spatially adjustable patient bearing table, for example an
operating table or urological table, are available. When the therapy
device of the invention and the x-ray device are aligned relative to one
another such that the central ray of the x-ray device coincides with the
acoustic axis of the source, this creates the conditions for adjusting the
position of the patient on the support table under x-ray supervision, so
that the acoustic axis of the source proceeds through a region to be
treated. To that end, the patient must merely be displaced relative to the
source with the patient support table so that the image of the x-ray
impermeable mark coincides in the x-ray image with the image of the region
to be treated. Thereupon, the patient and the focus of the acoustic waves
must be shifted relative to one another in the direction of the acoustic
axis, using the means for identifying the distance of the region to be
treated from the source, so that the distance of the region to be treated
from the source of acoustic waves is equal to the distance of the focus of
the acoustic waves from the source of acoustic waves. The region to be
treated is then located in the focus of the acoustic waves, whereupon the
treatment with acoustic waves can ensue in the required way.
A high-grade work station for treating a patient with focused acoustic
waves, which offers x-ray locating, can be realized with the therapy
system of the invention and equipment which is already present. This
equipment, i.e. an x-ray device with an adjustable patient support table
or a C-arm device and a patient support table, can continue to be employed
for their conventional purposes as needed, since no permanent connection
whatsoever is produced to the therapy system of the invention. The
distance identifying means can be a pressure sensor, an ultrasound
applicator, or some other type of acoustic device. Even if an ultrasound
applicator is not used as the distance identifying means, an ultrasound
applicator can still be introduced into the x-ray-transparent region, so
that there is the possibility of obtaining additional information about
the region to be treated.
Although European Application 0 372 119 discloses a therapy system for
treating a patient with focused acoustic waves that includes a source of
focused acoustic waves having an x-ray transparent region, and application
means for introducing the focused acoustic waves into the patient to be
treated, the locating of a region to be treated ensues herein with an
x-ray locating system that forms a component part of the therapy means.
The x-ray radiation proceeds through the x-ray transparent region of the
source. The locating of a region to be treated ensures in such a way that
the x-ray locating system is pivoted around an axis in order to
transirradiate the patient to be treated from two different directions. On
the basis of the x-ray images obtained in this way, the region to be
treated is aligned such that it lies at the intersection of the central
rays belonging to the two transirradiation directions. Subsequently, the
source is set such that the focus of the acoustic waves is located in the
intersection. Moreover, an ultrasound locating system is provided that can
be introduced into the x-ray-transparent region. There is no suggestion,
however, that the x-ray locating system and the ultrasound locating system
be applied in combination in such a way for locating a region to be
treated that only the distance of the region to be treated from the source
is identified with the ultrasound locating system, and the locating
otherwise ensues exclusively using the x-ray locating means.
German Gebrauchsmuster 90 17 441 discloses an aiming device for a
lithotriptor, wherein the locating of a calculus to be disintegrated
ensues exclusively with an x-ray locating system that transirradiates the
patient to be treated from different angles. The aiming device has a
plurality of x-ray impermeable marks that allow the x-ray locating means
(which is a conventional C-arm x-ray system separate from the
lithotriptor) and the lithotriptor to be aligned relative to one another
in the required way. The x-ray impermeable marks also allow the patient to
be adjusted relative to the lithotriptor so that the calculus to be
treated is located in the focus of the lithotriptor. Acoustic means for
identifying the distance of the calculus to be disintegrated are not
provided. On the contrary, the locating ensures exclusively on an x-ray
basis.
As noted above, the means for identifying the distance of the region to be
treated from the source can be a diagnostic ultrasound applicator
according to one version of the invention, this being introducible into
the x-ray transparent region of the source. Such an ultrasound applicator
can be used exclusively for distance measuring (i.e., not for imaging
purposes) or for imaging, or both. The focus of the acoustic waves and the
body of the patient can be easily shifted relative to one another in the
direction of the acoustic axis of the source on the basis of the marking
on the picture screen of the ultrasound display device, connected to the
ultrasound applicator, which indicates the position of the focus of the
acoustic waves in the ultrasound image. The patient and the focus are
shifted relative to one another such that the image of the region to be
treated coincides with the marking in the ultrasound image visible on the
picture screen. The ultrasound applicator is preferably a B-scan
applicator that, when introduced into the x-ray-transparent region,
assumes such a position that the plane of the body of the patient scanned
with the ultrasound applicator contains the acoustic axis of the source.
It is especially advantageous that the ultrasound applicator and the
associated ultrasound display device can be employed for other purposes
independently of the therapy system of the invention.
In a preferred embodiment of the invention, the means for identifying the
distance of a region to be treated from the pressure pulse source include
a pressure sensor, means for the pulsed operation of the source and means
for measuring a time span of acoustic wave travel, corresponding to the
distance of the region to be treated from the source. This time span ends
with the appearance of an output signal of the pressure sensor that
corresponds to the echo arising by reflection from the region to be
treated of the acoustic wave that arose on the basis of the pulsed
actuation of the source. Given the arrangement of the pressure sensor in
the propagation path of the acoustic waves, for example, a time span can
be measured for this purpose that elapses between two pulsed output
signals of the pressure sensor that appear following the pulsed actuation
of the source. The two pulse-like output signals of the pressure sensor
are respectively caused by a signal arising upon passage of the generated
acoustic wave through the pressure sensor on its way from the source to
the region, and by the weaker signal that arises when the parts of the
generated acoustic wave reflected at the region to be treated pass through
the pressure sensor. The time elapsing between the pulse-like output
signals of the pressure sensor thus represent a measure for the distance
of the region to be treated from the pressure sensor. Since the distance
of the pressure sensor from the source or from the focus of the acoustic
waves is known, shifting the patient to be treated and the focus of the
acoustic waves relative to one another in the direction of the acoustic
axis of the source makes it easily possible to assure that the time
between the two pulse-like output signals of the pressure sensor is equal
to the transit time that a pressure pulse requires for covering the
distance (in more exact terms, for covering twice the distance) of the
pressure sensor from the focus of the acoustic waves. When these times
coincide, this means that the region to be treated lies in the focus of
the acoustic waves, as desired. Since this adjustment procedure can make
it necessary to repeatedly actuate the source in pulsed fashion, it can be
expedient in the interests of patient comfort to actuate the source for
pulsed operation so that it generates acoustic waves of diminished
intensity. Since it is not only the distance of the pressure sensor from
the focus of the acoustic waves but also the distance of the focus from
the source that are known, it is also possible to measure the pulse-like
output signal arising upon passage of the parts of the generated acoustic
wave reflected at the region to be treated through the pressure sensor. In
this case, it is adequate that the pressure sensor be arranged in the
propagation path of the reflected parts of the acoustic waves. It can then
be assured by shifting the patient to be treated and the focus of the
acoustic waves relative to one another in the direction of the acoustic
axis of the source that the time between the pulse-like actuation of the
source and the output signal of the pressure sensor to be taken into
consideration is equal to the transit time that a pressure pulse requires
for covering the sum of the distance of the source from the focus of the
acoustic waves and the distance of the focus of the acoustic waves from
the pressure sensor.
As has already been mentioned, the region to be treated is introduced into
the focus of the acoustic waves by shifting the patient and the focus of
the acoustic waves relative to one another in the direction of the
acoustic axis of the source. This, for example, can occur by moving the
patient support table in this direction. According to an advantageous
embodiment of the invention, however, the source is provided with means
for displacing the focus of the acoustic waves along the acoustic axis of
the source. This displacement means, for example, can be fashioned such
that the source is adjustable in the direction of its acoustic axis
relative to the applicator housing as disclosed in European Application 0
328 943, corresponding to U.S. Pat. No. 4,947,830. It is especially
advantageous, however, when the means for displacing the focus of the
acoustic wave contain an acoustic lens with variable focal length
according to one version of the invention. It thus becomes possible to
achieve a relatively large displacement range of the focus along the
acoustic axis of the source in a space-saving way.
Preferably a control means is provided that automatically sets the means
for displacing the focus of the acoustic waves on the basis of the output
signals of the means for identifying the distance of the region to be
treated from the source, such that the distance of the region to be
treated from the source is equal to the distance of the focus of the
acoustic waves from the source. When, thus, the patient has been aligned
relative to the therapy system so that the image of the region to be
treated coincides with the image of the x-ray impermeable mark, the focus
of the acoustic waves is automatically displaced with reference to the
output signals of the pressure sensor such that the focus is located in
the region to be treated. Treatment with acoustic waves then follows.
In order to facilitate the alignment of the x-ray device and the therapy
system relative to one another, a second x-ray impermeable mark can be
arranged at the distance of the x-ray impermeable mark on the acoustic
axis in a further version of the invention. The correct alignment of the
therapy system and the x-ray device relative to one another can then be
simply recognized from the fact that the two marks coincide.
In order to preclude disturbing influences of the acoustic propagation
medium on the image quality of the x-ray images serving the purpose of
x-ray locating, an x-ray transparent tube can be provided in an embodiment
of the invention that displaces the acoustic propagation medium from the
x-ray transparent region at least during passage of the x-ray radiation
through the x-ray transparent region of the source. At least one
x-ray-impermeable mark is applied to the x-ray transparent tube. In an
especially advantageous embodiment of the invention, at least the source
and the applicator are combined to form a therapy head that is attached to
a carriage displaceable on the floor. A compact structure of the therapy
device is thus achieved. The carriage can also contain the units required
for the operation of the therapy system.
In order to enable above-table as well as under-table applications of the
therapy system, a further embodiment of the invention the therapy head is
attached to the carriage pivotable by 180.degree. around an essentially
horizontal axis. It is self-evident that the patient support table must
have an adequately large opening or interruption for the application of
the applicator to the body of the patient to be treated in the case of
under-table application.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view of a therapy system constructed in
accordance with the principles of the present invention, interacting with
an x-ray examination device, in a schematic representation.
FIG. 2 is a schematic illustration of a longitudinal section through the
therapy head of the therapy system of FIG. 1.
FIG. 3 is a block circuit diagram of the therapy system according to FIGS.
1 and 2.
FIG. 4 is a schematic illustration of a partial, longitudinal section
through the therapy head according to FIG. 2, in another operating
condition.
FIGS. 5 and 6 respectively show a part of the therapy head according to
FIG. 2 in a section along the lines V--V and VI--VI in FIG. 2.
FIG. 7 is a side elevational view of a therapy device of the invention in
collaboration with a C-bend x-ray device and an operating table.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows the therapy device of the invention generally referenced 1,
interacting with an x-ray examination system, generally referenced 2. The
latter includes a patient support table 3, an x-ray radiator 4 arranged
thereabove and an x-ray image intensifier 5 arranged under the patient
support table 3. The image of the output luminescent screen of the x-ray
image intensifier 5 is picked up with a video camera in a known way and is
displayed at a monitor 7, mounted in adjustable fashion at the ceiling of
the examination room with a bracket 6. The x-ray radiator 4 and the x-ray
image intensifier 5 are secured to a carrier 8 lying opposite one another,
this carrier 8 being aligned such that the central ray Z of the x-ray beam
emanating from the x-ray radiator 4 proceeds vertically. The carrier 8 and
the patient support table 3 are attached to a stand 9. The patient support
table 3 is adjustable in the direction of the three spatial axes x, y, z,
preferably by motor drive. At least the movements in the x and z
directions, i.e. in the direction of the longitudinal axis of the patient
support table 3 and transversely relative thereto, ensue independently of
the carrier 8 and, thus, of the x-ray radiator 4 and the x-ray image
intensifier 5. By adjusting the patient support table 3 in these two
directions, the central ray Z of the x-ray beam can be made to proceed
through different body regions of a patient lying on the patient support
table 3. An x-ray device of the described type is distributed, for
example, by Siemens under the name "UROSKOP B2".
The therapy device 1 has a therapy head, generally referenced 10, that is
secured via a holder 11 to a carriage 12 that can be moved on the floor of
the treatment room. The carriage 12 contains all units required for the
operation of the therapy head 10. A control panel 13 that has a keyboard
and a monitor (see FIG. 3) that are required for operating the therapy
device, which contains the control electronics for the therapy device 1,
is also on the carriage 12. The therapy head 10 contains a central,
x-ray-transparent region (indicted with broken lines in FIG. 1) and is
aligned relative to the x-ray examination system 1 (as described below)
such that the central ray Z thereof proceeds through the x-ray-transparent
region. The therapy head 10 presses against the body surface of the
patient P with an x-ray-transparent application cushion 14 so as to
introduce the focused acoustic waves generated with the therapy device 1
into the body of the patient P.
As may be seen from FIG. 2, the therapy head 10 contains a pressure pulse
generator, generally referenced 15, as the source of focused acoustic
waves. This pressure pulse generator 15 includes an electromagnetic
pressure pulse source 16 (not shown in detail) and an acoustic positive
lens, generally referenced 17. The positive lens 17 focuses the pressure
pulses emanating from the pressure pulse source 16 onto a focus F, which
is a three-dimensional focal zone in practice. The focus F lies on the
acoustic axis A of the pressure pulse generator 15 that corresponds to the
middle axis M (FIG. 2) of the pressure pulse generator 15. The pressure
pulse generator 15 is fashioned approximately rotationally-symmetrically
relative to the axis M. The pressure pulse source 16 and the lens 17 are
accepted in a housing 18, having an end remote from the pressure pulse
source 16 closed liquid-tight with an elastic-flexible application cushion
14. The pressure pulse source 16, for example, is an electromagnetic
pressure pulse source as disclosed in European Application 0 188 750,
corresponding to U.S. Pat. No. 4,697,588 and European Application 0 301
360, corresponding to U.S. Pat. No. 4,928,672 in terms of structure and
function. At its other end neighboring the pressure pulse source 16, the
housing 18 has a mounting flange 19 that serves the purpose of securing
the therapy head 10 to a mounting ring 20 of the carrier 11 by screws,
only the center lines of two screws being indicated with broken lines in
FIG. 2. A tube 22 having a closed lower end is introduced into the bore of
the inside wall 21, this tube 22 being formed of an x-ray-transparent
material, for example Plexiglass.RTM.. The tube 22 is accepted in the bore
of the inside wall 21 in axially displaceable fashion and liquid-tight.
Sealants, not shown in FIG. 2, can be provided. The space situated between
the pressure pulse source 16 and the positive lens 17 as well as the space
situated between the positive lens 17 and the application cushion 14 are
respectively filled with water 23 and 24 as an acoustic propagation
medium.
The region of the therapy head 10 situated within the inside wall 21
represents an x-ray-transparent region from which the water 24 can be
displaced with the tube 22 in order to avoid negative influences on the
image quality. When the therapy head 10 is applied to the body surface of
the patient P indicated in FIG. 2, the tube 22 is thereby introduced into
the bore of the inside wall 21 to such an extent that its base 25 presses
against the body surface of the patient P with the application cushion 14
therebetween.
The positive lens 17 is composed of a solid lens 26 and a liquid lens
generally referenced 27. The solid lens 26 is biconcavely shaped and is
formed of a material, for example polystyrol, wherein the acoustic
propagation speed is higher in the water 24 provided as the acoustic
propagation medium. The solid lens 26 consequently acts as positive lens.
The inner edge of the annular solid lens 26 is introduced liquid-tight
into a channel in the outer surface of the inside wall 21. The solid lens
26 has an outer circumference introduced liquid-tight into the housing 18.
The liquid lens 27 has a lens fluid 29 enclosed between an entry wall 28
and that side of the solid lens 26 facing toward the pressure pulse source
16. The outer edge of the entry wall 28 formed, for example, of
polymethylpentene (TPX) or of polytetrafluorethylene (PTFE) is accepted
liquid-tight in a circumferential channel of a retaining ring 30. The
retaining ring 30 is accepted in axially non-displaceable fashion between
the pressure pulse source 16 and the solid lens 26, whereby the solid lens
26 is held axially non-dislocatable with a snap ring 31. The outer surface
of the retaining ring 30 presses liquid-tight against the housing 18. The
inner circumferential edge of the entry wall 28 is accepted in a
circumferential channel of a sleeve 32 surrounding the inside wall 21 in
liquid-tight fashion. The sleeve 32 is longitudinally displaceable on the
inside wall 21 with a schematically indicated adjustment mechanism 33,
which can be an electric motor with suitable gearing. The adjustment
mechanism 33 is in communication with a drive unit 35 (see FIG. 3) via a
line generally referenced 34. The focal length of the liquid lens 27 and,
thus, the overall focal length of the positive lens 17 can be varied by
displacing the sleeve 32 between an ultimate position shown with solid
lens in FIG. 2 and another ultimate position indicted with broken lines in
FIG. 2.
When, as in the case of the illustrated exemplary embodiment, the lens
fluid 29 is a liquid wherein the acoustic propagation speed is lower than
in the water 23 provided as acoustic propagation medium (for example,
Flutec.RTM. EP 3 or Fluorinert.RTM. FC 75), the liquid lens 27 functions
as a positive lens at the ultimate position shown with solid lens in FIG.
2. As the sleeve 32 is gradually displaced in the direction toward its
other ultimate position, the focused effect of the liquid lens 27
diminishes and gradually changes into a slightly defocusing effect. The
liquid lens 27 thus acts as a dispersion lens in its ultimate position
indicated with broken lines. The effect on the position of the focus of
the pressure pulses generated with the pressure pulse source 16 and
focused with the positive lens 17 is that the focus F1 situated closer to
the pressure pulse source 16 is obtained at the ultimate position shown
with solid lines in FIG. 2 and the focus F2 at a greater distance
therefrom is obtained at the ultimate position indicated with broken
lines. The focus F of the pressure pulses can be displaced with continuous
variation between these two ultimate positions dependent on the position
of the sleeve 32 along the acoustic axis A of the pressure pulse generator
15. The adjustment mechanism 33 contains a position generator (not shown),
for example an inductively acting position generator, that generates a
signal corresponding to the position of the sleeve 32, and thus to the
position of the focus F that has been set, via a line generally referenced
36.
Since, when adjusting the sleeve 32, the volumes respectively situated
between the pressure pulse source 16 and the entry wall 28 and, between
the entry wall 28 and the solid lens 26 change, respective connecting
branches 37 and 38 (schematically shown) are provided. The branches 37 and
38 respectively connect the aforementioned volumes to schematically
indicated compensation vessels 39 and 40 that contain water or lens fluid.
This permits a volume compensation to ensue in the required way both with
respect to the water 23 as well as with respect to the lens fluid 29. Such
a volume compensation can also ensue with respect to the water 24 when the
volume situated between the solid lens 26 and the application cushion 14
changes upon introduction of the tube 22, when the application cushion 14
is pressed against the patient P, since a further connecting branch 41
with an associated compensating vessel 42 are also provided.
A pressure sensor 43 is attached to that side of the solid lens 26 facing
away from the pressure pulse source 16. The pressure sensor 43, for
example, is a sensor formed of a piezoelectrically activated polymer foil
that is distributed by Pennwalt, Great Britain, under the name
"Kynar.RTM.-Piezo-Film SDT 1-028k". The pressure sensor 43 is in
communication with an evaluation circuit 45 (FIG. 3) via a line generally
referenced 44. The pressure pulse source 16 connected, via a schematically
indicated high-voltage cable 46, to a high-voltage pulse generator 47
(FIG. 3) situated in the carriage 12. When the pressure pulse 16 is
charged with a high-voltage pulse from the pulse generator 47 for
outputting a pressure pulse, the pressure sensor 43 generates two
successive, pulse-like signals. The first of these signals arises as the
pressure pulse emanating from the pressure pulse source 16 passes through
the pressure sensor 43 on its path to the focus and the second, weaker of
these signals arises as the parts of the pressure pulse reflected at the
region to be treated, for example a calculus, a bone or a tumor, inside
the body of the patient P pass through the pressure sensor 43.
The block circuit diagram of the therapy device 1 is shown in FIG. 3. An
electronic control unit 48 is provided for controlling the functions of
the therapy device 1, a keyboard 49 that serves the purpose of operating
the therapy device 1 being connected to this electronic control unit 48.
The drive unit 35 is connected to the control unit 48, this drive unit 35
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