Patent Description:
A device and a method for localizing stones and for targeting a shock wave source of a lithotripter is disclosed in <CIT>. Here a shockwave generator, a patient table and an ultrasound targeting device are provided with optical markers for tracking with a pair of infrared cameras. The body or parts of the body of a patient move slightly during breathing. This causes kidneys and other organs to move slightly such that they may move out of the focal volume of a shock wave source.

<CIT> discloses a lithotripter which is synchronized to the signal of a respiration sensor. This allows only for short treatment periods with a comparatively low repetition frequency corresponding to the respiration frequency.

<CIT> discloses a shock wave therapy device with dynamic target tracking. <CIT> discloses an optimized therapeutic energy delivery.

The problem to be solved by the invention is to provide a shock wave device, which allows treatment of organs or areas within organs independent of respiration. The shock wave device should be comparatively simple and avoid complex and expensive mechanics.

Solutions of the problem are described in the independent claim.

The dependent claims relate to further improvements of the invention.

In an embodiment, a shock wave device, which may be a lithotripter includes a shock wave source and may further include a patient table. The shock wave source may be of any type suitable for generating shock waves. It may include a shock wave generator and/or transducer, which may include at least one of a coil, a spark gap or a Piezo transducer. The shock wave generator/transducer may be partially enclosed by a reflector. Depending on the type of transducer, the reflector may have a parabolic or half-elliptic shape. The shock wave source may have a focal volume which is distant from the shock wave source and normally around a center axis of the shock wave source. The focal volume may be defined as a volume, where the maximum shock wave intensity is maintained with a deviation of maximal -<NUM> dB or -<NUM> dB. If the focal volume is defined with a <NUM> dB deviation, the pressure at the limit of the zone is half of the maximum pressure inside the zone. The focal volume may have an elliptical shape with a length in an axial direction (defined by the center axis) of the shock wave source axis of <NUM> to <NUM> and a diameter between <NUM> and <NUM>. The focal volume normally is spaced from the shock wave generator and/or transducer.

The patient table may have a basically planar surface defining a longitudinal axis. It is configured for accommodating a patient. The shock wave source may be mounted below the patient table. In general, a shockwave source may be mounted in alternative ways, e.g. on a stand or support.

Due to movements of a patient's body, e.g. by respiration or heartbeat, an object to be treated may move out of the focal volume. For example, a movement of the chest causes a movement of the kidneys in a cranio-caudal direction, which is approximately parallel to the surface of the patient table accommodating the patient. The amplitude of displacement of the kidneys normally is in the range of <NUM> to <NUM>. As the center axis of a normal shock wave generator is approximately orthogonal to the surface of the patient table, a kidney stone may easily move out of the focal volume. The respiration frequency of an anesthetized person may be in the range of <NUM> to <NUM>.

In an embodiment, a shock wave source is arranged tiltable around at least one tilt axis which may be approximately parallel to a plane defined by a surface of a patient table, where a deviation in parallelism may be of +/- <NUM>°. Further, the tilt axis may be orthogonal to a longitudinal axis of the patient table, where deviation in orthogonality of +/- <NUM>° may be possible. The maximum angle of tilt may be in a range between <NUM>° and <NUM>°. It may be in a range between <NUM>° and <NUM>° or between <NUM>° and <NUM>°. A number of tests have shown that a typical angle of <NUM>° is sufficient to track typical stone movements, whereas for larger movements an angle of <NUM>° may be sufficient. Tilting of the shock wave source may be achieved by tilting the whole shock wave source including the shock wave generator/transducer and the reflector or only by tilting the shock wave generator/transducer. Tilting may be done by a tilting motor or a tilting drive, which may be a linear drive or any other suitable means. Tilting is synchronized to the motion of the patient body, which may be sensed by a motion sensor or by a respiration sensor. A respiration sensor may be a sensor configured for at least one of a chest movement of the patient due to respiration, a change of chest volume and/or size of the patient due to respiration, a change of position of an internal organ like kidney or heart by using ultrasound-imaging, a change of center of gravity of the patient and/or organ of interest which may be a kidney to be treated. Herein, for simplicity, such a sensor may be called a respiration sensor. The signal of the movement sensor/respiration sensor may be amplified with a variable gain. Further, an offset may be added to generate a tilt control signal defining the tilt angle. By this, a coupling of the tilt angle to the body movement and therefore to the movement of the kidney stone may be achieved.

As the position of the focal volume moves in synchronicity with the kidney stone, generating of shock wave pulses at any time will result in a high energy coupling into the stone and a high treatment efficiency.

For heart treatment, respiration and heartbeat may be considered. This may require a tilting movement about two different axes with different frequencies. Basically all parts of a body may be treated by compensating any movement by a tilting movement.

A fine adjustment of the amplitude of the tilting movement may either be made manually by a user who may watch the imaging system and an indication of the focal volume. Further, adjustment of the amplitude may be made automatically, for example by a computer system, analyzing the images of the imaging system.

A display may be provided indicating an image from an imaging system, like an x-ray image or and ultrasound image, which may further indicate the focal volume. Based on this, a user may estimate the quality of adjustment and treatment.

Due to the body movement or respiration tracking of the shock wave source, any shock wave repetition frequency, may be selected independent of the respiration frequency.

Due to the simple tilting movement of the shock wave source, only one movable axis is required, keeping the systems comparatively simple and efficient.

In an embodiment, the shock wave source may be rotated around the center axis about an angle in a range between +/- <NUM>° to +/- <NUM>°. The range may be between +/- <NUM>° and +/- <NUM>°. In a typical application, a range of +/-<NUM>° would meet most requirements. Usually, kidneys and kidney stones have a slightly outward movement in addition to the movement parallel to the patient table, which may be compensated by such a rotation around the center axis. In a very simple embodiment, there may be only two discrete angle settings, for example at + <NUM>° and at - <NUM>°, one for the left kidney and the other for the right kidney, which would suit most patients. In another embodiment, a larger number of positions may be provided. Alternately, a drive like a motor may be provided to adjust the angle.

The basic concept explains herein at the example of a kidney stone may also be applied to a urethra stone or other concrements in a body.

The shock wave device or lithotripter may also include a linear drive for the shock wave source, which may be operating in <NUM>, <NUM> or <NUM> axes. Such a drive may be used for general adjustment of the relative position of the shock wave source relative to the patient.

The methods of operation disclosed are not explicitly recited by the wording of the claims but are considered useful for understanding the invention.

A method of focusing a shock wave source to a kidney stone comprises the steps of:.

The tilt axis may be an axis in a plane essentially parallel to a plane of a patient table and essentially orthogonal to a longitudinal axis of the patient table, including deviations in parallelism and/or orthogonality of +/- <NUM>°.

The method may further include the steps of rotating the shock wave source around its center axis or a fixed angle before performing the steps a to c.

In <FIG>, a first embodiment is shown. A shock wave device, which may be a lithotripter <NUM> may include a patient table <NUM> and a shock wave source <NUM>. The shock wave source <NUM> may be arranged below the patient table <NUM>, such that a patient (not shown here) may be accommodated on top of the patient table. The patient table may have a longitudinal axis <NUM>. There may be a hole or cutout in the patient table at the position of the shock wave source. The shock wave source <NUM> may be tiltable in a direction of tilt <NUM> around a tilt axis <NUM>. The shock wave source may be held by a tilt shaft <NUM> and operated by a tilt drive motor <NUM>. In another embodiment, a linear tilt drive <NUM> may be provided and configured for a linear movement in a linear tilt drive direction <NUM> to perform a tilt of the shock wave source <NUM>. Basically, any kind of suspension and drive may be used, as long, as a tilt may be performed. This may also be a tripod drive. Further, the shock wave source <NUM> may have a center axis <NUM>, and it may be rotatable in a rotation direction <NUM> around the center axis <NUM>.

<FIG> shows a side view. In this figure, a patient <NUM> is positioned on top of the patient table <NUM>. The patient may have a kidney <NUM> with a kidney stone <NUM>. Below the table <NUM>, the shock wave source <NUM> is shown in a sectional view. It may have a shock wave generator <NUM> which may be a coil as shown herein and which is at least partially enclosed by a reflector <NUM>. Further, the center axis <NUM> is marked as a dashed line and a tilted center axis <NUM> of a tilted state of the shock wave source is marked as a second dashed line. Normally, the interior of the reflector and the space between the source and the patient is filled with a liquid like water or another shockwave conducting medium. To contain the water within the volume, a coupling bellow <NUM> may be provided.

<FIG> shows focal volume positions with tilting in a side view. On the left side, a first focal volume <NUM> is shown around the center axis <NUM> in a first state. When tilting the shock wave source about an angle, this focal volume is displaced to second focal volume <NUM> around a tilted center axis <NUM>. In this figure, a tilt angle of approximately <NUM>° is shown. It can be seen that the first focal volume from a normal state and the second focal volume from a tilted state together cover roughly twice the volume at the center of the focal volumes. A kidney stone <NUM>, which may be centered to the center axis <NUM> in a first state, may move by respiration movement in a direction <NUM> to a second position, which then may be close to the tilted center axis <NUM>. As the tilt of the shock wave source is synchronized with the respiration movement and therefore with the movement of the kidney <NUM> and with the movement of the kidney stone <NUM>, the kidney stone is always approximately at the center axis of the shock wave source and therefore within the focal volume. This ensures a high energy coupling into the stone at any time.

<FIG> shows a top view. As the kidneys not only move roughly parallel to the longitudinal axis <NUM> of the body and therefore of the patient table, but also move slightly sidewards, the shock wave source may be rotated around the center axis <NUM> in a first direction, such that the tilt results in movement in a first tilt direction <NUM> under an angle to the longitudinal axis <NUM>. Alternatively, the shock wave source may be rotated into an opposing second position, resulting in a tilting movement in a second tilt direction <NUM>. The focal volume covered during the tilt movement is indicated with reference number <NUM> for the first tilt direction <NUM> and with reference number <NUM> for the second tilt direction <NUM>.

<FIG> shows a block diagram. A respiration sensor <NUM> produces a respiration signal or a signal related to respiration. Such a respiration signal may be a signal indicating the air flow into the body and/or out of the body, and/or a signal related to a movement of the body. For example, a sensor measuring the circumference of the chest may be used to generate a signal for such an indication. The signal is coupled into a signal amplifier <NUM> which may further receive a gain signal <NUM> and an offset signal <NUM>. The gain signal and the offset signal may either be manually set by an operator and/or may be set by a controller/computer <NUM>. This signal allows to modify the amplitude of the signal received by the respiration sensor and to add an offset if desired. The output signal of the signal amplifier <NUM> may be fed to a computer/controller <NUM>. It may also be fed to a motor controller <NUM> which generates a control signal for a tilt motor <NUM>. The tilt motor <NUM> may tilt the shock wave source around the tilt axis <NUM>. As mentioned above, it may be a rotating motor or a linear drive, depending on the mechanical design. In an embodiment, there may be a linear relationship between the input signal into the motor controller <NUM> and the tilt angle, further resulting in a linear relationship between the respiration sensor signal and the tilt angle. To prevent excessive tilt angles, the motor controller <NUM> and/or the signal amplifier <NUM> may have a limiter to limit the output signal.

Claim 1:
A shock wave device (<NUM>) comprising a shock wave source (<NUM>),
characterized in, that
the shock wave source (<NUM>) being coupled to a tilt drive (<NUM>, <NUM>) and configured for a tilting movement (<NUM>) around at least one tilt axis (<NUM>), the tilt drive (<NUM>, <NUM>) being coupled to a movement sensor (<NUM>) and configured for a tilting movement (<NUM>) as a function of a movement sensor signal (<NUM>) from the movement sensor (<NUM>), and the movement sensor (<NUM>) is at least one of a respiration sensor or a heart pulse sensor.