DETERMINING A MOVEMENT OF AN OBJECT, AND THERAPY APPARATUS

Abstract

The movement of an object, in particular of an organ during histotripsy treatment is determined specifically for repositioning purposes. This is done by producing bubbles in or at the object. The bubbles are detected, and their movement is recorded. The movement of the object is estimated from their movement. If applicable, a focal point of a therapy apparatus may be repositioned in accordance with the movement of the object.

Claims

1. A method for determining a movement of an object, the method comprising: producing bubbles in or at the object; detecting the bubbles in or at the object; recording a movement of the bubbles; and obtaining an estimated value for the movement of the object from the movement of the bubbles.

2. The method of claim 1, wherein producing the bubbles is carried out by introducing energy into or onto the object.

3. The method of claim 2, wherein introducing energy includes beaming in electromagnetic waves.

4. The method of claim 3, wherein the electromagnetic waves comprise at least one of radio waves, microwaves, or ultrasound waves.

5. The method of claim 1, wherein producing the bubbles is carried out by injecting the bubbles or by using a chemical reaction.

6. The method of claim 2, wherein a first portion of the energy is focused at a focal point in or at the object, and a second portion of the energy that differs from the first portion, produces the bubbles at another site away from the focal point without therapeutic effect.

7. The method of claim 6, wherein the focal point is repositioned or switched on/switched off according to the estimated value for the movement of the object.

8. The method of claim 2, wherein the energy is applied at a first power density in a first phase for producing the bubbles, and at a second power density in a second phase, wherein the first power density is less than the second power density.

9. The method of claim 8, wherein the energy is defocused at a defined location in the first phase and is focused at the defined location in the second phase.

10. The method of claim 1, further comprising: controlling an ultrasound apparatus or an exposure apparatus according to the estimated value for the movement of the object.

11. A recording apparatus for determining a movement of an object. the recording apparatus comprising: a production device for producing bubbles in or at the object; a detection device for detecting the bubbles in or at the object; a recording device for recording a movement of the bubbles; and an analysis device for obtaining an estimated value for the movement of the object from the movement of the bubbles.

12. The recording apparatus of claim 11, wherein a component of a therapy apparatus is controlled according to the estimated value for the movement of the object.

13. The recording apparatus of claim 12, wherein the therapy apparatus comprises a histotripsy apparatus, a thermal ablation apparatus, or a lithotripsy apparatus.

14. The recording apparatus of claim 11, further comprising: an imaging device configured for creating images of the object, wherein the detection device for detecting the bubbles for determining the movement of the object is integrated in the imaging device.

15. A non-transitory computer readable storage medium comprising a set of computer-readable instructions stored thereon for determining a movement of an object, the computer-readable instructions which, when executed by at least one processor cause the at least one processor to: cause a production device to produce bubbles in or at the object; detect the bubbles in or at the object; record a movement of the bubbles; and obtain an estimated value for the movement of the object from the movement of the bubbles.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0032] FIG. 1 depicts a schematic view of a therapy apparatus for histotripsy according to an embodiment.

[0033] FIG. 2 depicts an acquisition of histotripsy bubbles according to an embodiment.

[0034] FIG. 3 depicts a schematic flow diagram of an embodiment of a method.

DETAILED DESCRIPTION

[0035] FIG. 1 depicts a patient 1 on a couch 2. The liver 3 of the patient 1 is being treated by histotripsy. For this purpose, a histotripsy transducer 4 is placed on the abdomen or ribcage of the patient 1. The histotripsy transducer 4 is approximately in the shape of a pot. In the region of the base and wall of the pot is a coupling segment 5 of the histotripsy transducer 4. On the side of the histotripsy transducer 4 that faces away from the patient 1 is arranged the actual ultrasound transducer 6 effectively as a pot lid. The ultrasound transducer 6 is designed to focus the emitted ultrasound waves in a focal region 7. In the present example, the focal region 7 lies at that site of the liver 3 that is to be treated.

[0036] The histotripsy transducer 4 may include an imaging probe 8, that may be used to obtain images from the focal region 7 and, if applicable, the area surrounding it. The imaging probe is a sonography instrument, for instance. It may be arranged in the center of the ultrasound transducer 6, and likewise acoustically coupled to the patient 1 via the coupling segment 5.

[0037] In the present example, the ultrasound transducer 6 constitutes at least a part of the emission device, that transmits waves (in this case ultrasound waves) into the liver 3 of the patient 1. The liver 3 therefore constitutes the object, the movement of which is meant to be determined. The movement of the liver 3 results, for instance, from the breathing and heartbeat of the patient 1. It may be the case, however, that movements of the liver originate from motor movements of the patient 1. If the patient specifically does not remain still in one spot during the treatment, but changes their position, for instance on the couch 2, then the position of their liver 3 with respect to the histotripsy transducer 4 also changes.

[0038] In the example of FIG. 1, both the actual ultrasound transducer 6 and the imaging probe 8 are controlled by a shared control device 9. The control device 9 may include a screen as an output unit 10. In addition, the control device has a detection device (not explicitly shown) and an analysis device (likewise not explicitly shown). The signals from the imaging probe 8 may be analyzed by the detection device in order to detect bubbles in or at the object (liver 3 in this case). The bubbles identified by the detection device are analyzed by the analysis device in terms of their movement. For example, movements of the bubbles that take place relative to the histotripsy transducer 4 are recorded. Purely a change in size of the bubbles is usually ignored here. As soon as the analysis device records a movement of the bubbles, this movement may be used as an estimated value for the movement of the object intended for therapy (liver 3 in this case). The movement of the object is thus registered indirectly by the bubbles. Additional equipment or an additional probe for recording the movement of the object is not necessary with the design. Instead, for example, the signals from a standard histotripsy apparatus that includes imaging may be used also to establish movements of the object intended for therapy. This design of the histotripsy apparatus including histotripsy transducer 4 and control device 9 may be applied to other therapy apparatuses as well, for instance those for lithotripsy, thermal ablation and the like.

[0039] FIG. 2 depicts an image of a focal region 7, that was obtained, for example, by the imaging probe 8 or a sonography instrument. Inside the focal region 7 may be seen numerous bubbles, that in the present case were produced by the histotripsy transducer 4. The focal region 7 is clearly demarcated from the surrounding area. Bubbles 11 also appear outside the focal region 7. The bubbles 11 outside the focal region 7 are generally smaller than inside the focal region 7. The reason for this is that the power density of the ultrasound waves is lower outside the focal region 7. Nonetheless, even the smaller bubbles 11 outside the focal region 7 may be detected and tracked. For example, for example, their movement relative to the focal region 7 may be recorded. Whereas large bubbles tend to appear and also disappear again only inside the focal region 7, small bubbles are produced outside the focal region 7 for a lower power density. With a movement of the organ or object, the small bubbles 11 also move relative to the focal region 7. Hence the small bubbles also move relative to the waves or to their direction of propagation, and also relative to the emission device (the histotripsy transducer in this case).

[0040] FIG. 3 is a schematic flow diagram of an embodiment of the method. In a first step S1, waves are transmitted into or onto an object. The waves may be ultrasound waves or may be electromagnetic waves such as radio waves or microwaves.

[0041] In a subsequent step S2, bubbles are produced in or at the object (by the waves). For example, the waves may be focused, so that there is a higher power density inside a focal region compared with a region outside the focal region. Nonetheless, as soon as a cavitation threshold, for instance in histotripsy, is exceeded, cavitation bubbles are expected to form in the region outside the focal region as well.

[0042] In a step S3, bubbles are detected in or at the object. These may be the bubbles outside the focal region.

[0043] In a step S4, a movement of the bubbles is recorded. For example, this movement may be recorded relative to the focal point or to the histotripsy transducer or to the particular therapy apparatus. Whereas the bubbles inside the focal region do not move detectably, the bubbles outside the focal region generally move with the object.

[0044] In a step S5, an estimated value for the movement of the object is obtained from the movement of the bubbles. Since the bubbles outside the focal region practically do not move relative to the object, the movement of the bubbles may be used as the estimated value for the movement of the object.

[0045] In an optional step S6, the focal point of the waves is repositioned according to the estimated value for the movement of the object. This repositioning may be performed using a robot arm (not shown in FIG. 1), that moves the histotripsy transducer 4 relative to the patient 1 or to their liver 3. This movement may be controlled by the control device 8. In this manner, the histotripsy transducer may be repositioned in accordance with the movement of the object (the liver 3 in this case). The repositioning in accordance with the movement may be performed irrespective of the cause of the movement (breathing, heartbeat, motor movement, etc.).

[0046] For a specific example, embodiments propose producing microbubbles outside a focal region or target area by unfocused histotripsy ultrasound that lies slightly above the cavitation threshold. For treating a tissue, for instance a tumor, by collapsing bubble cavitations, focused histotripsy ultrasound may be directed onto the relevant target area. Monitoring the bubble cloud produced in the focused histotripsy would not be sufficient to distinguish a movement of the tissue/organ relative to the histotripsy ultrasonic probe or histotripsy transducer because the bubble cloud and the ultrasound focal point remain stationary in relation to the ultrasonic probe. Microbubbles may be produced by using non-focused ultrasound outside the target area. The position of the microbubbles does not depend on the position/orientation of the ultrasonic probe because they are produced by unfocused ultrasound. When the tissue/organ moves inside the patient, the microbubbles move with the tissue/organ relative to the ultrasonic probe. Online motion-correction may be carried out by monitoring the position of the microbubbles relative to the ultrasonic probe, for instance by the imaging ultrasound probe. Advantageously, the focal point of the histotripsy ultrasound may be adjusted according to the ascertained microbubble position.

[0047] Embodiments thus advantageously provide for online motion-correction during a histotripsy treatment, in which the motion data, i.e., the detected microbubble position, is inherently registered with the histotripsy ultrasound probe.

[0048] It is to be understood that the elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present invention. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that the dependent claims may, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent, and that such new combinations are to be understood as forming a part of the present specification.

[0049] While the present invention has been described above by reference to various embodiments, it may be understood that many changes and modifications may be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.