Boundary Detection in Ultrasonic Data

Abstract

A method for determining one or more tissue boundaries within ultrasound image data of an anatomical region is provided. The method is based on generating two separate images from identical input ultrasound data acquired within a single acquisition event. One image is generated with contrast enhancement to particularly visualize boundaries surrounding fluid-containing regions, while the second image is generated without this enhancement or with a different enhancement to particularly visualize boundaries surrounding tissue regions. An image segmentation procedure is then applied using a combination of both images as input to determine boundaries within the imaged region.

Description

Technical Field

[0001] The present invention relates to a method for detecting tissue boundaries in ultrasonic data.

Background Art

[0002] The depiction of tissue boundaries in ultrasonic image data has a wide range of applicability for various medical ultrasonic applications. Generally, such a depiction can be used to segment the boundaries of organs or other anatomical structures depicted in an ultrasonic data set.

[0003] One specific application example of boundary segmentation is in echocardiography.

[0004] In particular, despite the continuous improvement in image quality in echocardiography, the ability to accurately depict the endocardial boundary in an echocardiogram remains a problem in up to 20% of patients. To assist in boundary depiction, a technique known as left ventricular opacification (LVO) can be applied. This is a well-established method for enhancing the endocardial boundary in an echocardiogram with an appropriate contrast agent. Echocardiographic contrast agents have been developed and are available on the market in most regions of the world. The contrast agent significantly enhances the scattered signal from the blood pool and increases the backscattered signal by orders of magnitude compared to red blood cells. The contrast agent usually contains microbubbles that enhance echoreflection.

[0005] However, the tissue signal remains extremely strong even at harmonic frequencies, limiting the ability to visualize the endocardial boundary of the heart. To improve the effectiveness of ultrasonic contrast agents, techniques specialized for contrast have been developed with the goal of selectively suppressing the tissue signal. These techniques are known as contrast enhancement, and what is called a contrast-enhanced image is obtained.

[0006] As an example, these techniques may include generating a plurality of pulses for each scan line in a given image and incorporating a pulse scheme that can vary the amplitude, phase, or a combination of amplitude and phase for each pulse. The plurality of echoes received for each scan line are then combined to minimize the signal from the tissue while maintaining the signal from the contrast agent microbubbles.

[0007] For both echocardiogram images acquired with or without the aid of a contrast agent, model-based segmentation can be used to automatically fit a surface mesh to the anatomical structures of the heart visible in the image. In a series of adaptation steps, the algorithm detects the boundaries in the vicinity of each mesh triangle (using a specially trained boundary detector), and then adapts the mesh based on these detected image feature structures and further based on an internal energy derived from previous shape knowledge. This technique functions optimally when the image boundaries are clearly defined in all relevant structures in cardiac anatomy. The successful segmentation can then be used, for example, to derive ejection fraction measurements without the need for further user intervention.

[0008] The contrast imaging techniques described above significantly improve the visualization of endocardial boundaries and are often used in stress echocardiograms to assist in the detection of wall motion abnormalities. The technique is also used for the measurement of ejection fraction to assist in the assessment of cardiac function.

[0009] However, to date, reliable techniques for automating volume measurements for images acquired using contrast agents have remained lacking, and thus ejection fraction is often measured by manual tracing of the corresponding boundaries.

[0010] One important reason that it has been difficult to achieve this technical result is that the contrast agent within the left ventricular and left atrial cavities obscures the ability to determine where the ventricle ends and the atrium begins. In non-contrast images, the mitral valve (between the left ventricle and left atrium) can be seen as a bright structure. However, in contrast images, the bleed or blur of the strong contrast signal obscures the thin mitral valve (which would otherwise theoretically appear as a thin, dark interruption in the brightly contrast-enhanced region). The lack of a clearly defined image feature structure delineating the boundary between the left ventricle and left atrium can significantly impede the successful application of model-based segmentation.

[0011] More generally, this problem of strong contrast signal bleed or blur can affect the visibility of small feature structures located at the boundaries of contrast agent-containing regions in any imaged anatomical area.

[0012] The workaround is to acquire both contrast images (with contrast agent administered) and non-contrast images (without contrast agent). However, this is not satisfactory for many reasons. First, many of the parameters that one might attempt to measure using imaging may not be directly comparable in the two images (e.g., cardiac state, respiratory state, and the images may not be properly aligned due to transducer position and orientation misalignment). Therefore, alignment procedures are required, which can introduce errors or inconsistencies. This will likely degrade the quality of the results. Furthermore, the workflow becomes even more complex for clinicians who must acquire the two images with maximally overlapping fields of view. SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0013] An improved approach for boundary detection in ultrasonic data of anatomical regions would be valuable. MEANS FOR SOLVING THE PROBLEM

[0014] The present invention is defined by the claims.

[0015] According to an example according to one aspect of the present invention, a computer-implemented method for determining tissue boundaries within an imaged anatomical region is provided. The method comprises receiving ultrasonic data from an anatomical region containing an object of interest that includes one or more tissue boundaries, where the one or more tissue boundaries are adjacent to a fluid receiving region. The method further comprises applying a first image generation procedure to the ultrasonic data to generate a first image, where the first image generation procedure is adapted to suppress the visibility of tissue regions in the generated first image and / or enhance the visibility of fluid within the fluid receiving region in the generated first image. The method further comprises applying a second image generation procedure different from the first image generation procedure to the ultrasonic data to obtain a second image. The method further comprises applying an image segmentation procedure to both the first and second images. The method further comprises determining one or more tissue boundaries based on the segmentation procedure, or one or more tissue boundaries are determined as a result of the application of the segmentation procedure. The method further comprises generating a data output representing the determined one or more tissue boundaries.

[0016] The received ultrasonic data consists of data regarding a single data acquisition event or session (e.g., a single scan). A single acquisition event may mean, for example, data acquired from a single acquisition sequence, and a single acquisition sequence means a single continuous or unbroken sequence of one or more ultrasonic pulses and received echoes, or a series of acquisition scan lines, each of which may have one or more ultrasonic pulses.

[0017] When the general concept is to perform image segmentation based on two images generated from the same ultrasonic data acquired in a single acquisition event. One of these images is generated as a contrast-enhanced image in which tissue is suppressed and / or fluid is emphasized, and the other is generated without this same tissue suppression or fluid enhancement. Thus, the two provide different relative contrast representations of tissue and fluid, and the interface between them defines the tissue boundary.

[0018] As described above, a problem with known contrast-enhanced imaging is that the strong contrast signal in the enhanced visibility region leads to blurring or bleeding outside the edges of these regions. This can obscure the view of particularly thin and small anatomical features or boundary regions, such as the mitral valve between the atria and ventricles of the heart. Therefore, by generating two images (one with enhanced contrast and one without enhanced contrast) from the same ultrasonic data set and performing segmentation based on both, complementary information is utilized in the segmentation, which achieves the advantage of the contrast-enhanced image (i.e., enabling the accurate identification of the interface boundary between tissue and fluid, such as the endocardium), while also enabling the identification of smaller anatomical structures or thin wall portions (such as the mitral valve).

[0019] The two above-mentioned images are generated using the same ultrasonic data. Therefore, there is an inherent spatial alignment between them.

[0020] The above image segmentation can be applied separately to the two images, and more preferably, can have a combined segmentation that utilizes both images. In other words, preferably, the segmentation is applied simultaneously to both the first and second images.

[0021] The first image generation procedure is an image generation step designed to yield a first image, which, when compared to an image generated from the ultrasonic data without these same steps, and in particular when compared to a second image, includes steps in which the visibility of tissue regions is suppressed and / or the visibility of fluid within a fluid receiving region is enhanced.

[0022] The first image generation procedure can include one or more post - processing steps, which are applied to the received ultrasonic data before generating an image from the post - processed data. These post - processing steps have the effect of suppressing the visibility of tissue and / or enhancing the visibility of fluid within a fluid receiving region in the resulting first image, as compared to an image generation procedure that is otherwise identical but lacks these post - processing steps.

[0023] The second image generation procedure is preferably not configured to suppress the visibility of tissue regions in the generated second image or to enhance the visibility of fluid within a fluid receiving region in the generated second image. Thus, the procedure is adapted to obtain a second image with higher visibility of tissue regions than the first image and lower visibility of fluid than the first image.

[0024] Optionally, the second image generation procedure can further have one or more ultrasonic data processing steps for achieving tissue enhancement and / or fluid suppression effects in the reconstructed image. However, this is not essential.

[0025] The fluid receiving region preferably contains a fluid containing a contrast agent.

[0026] Thus, the improved visibility of fluid in the first image corresponds to the improved visibility of the contrast agent in that image. As an example, the fluid receiving region can be a cardiac cavity and the fluid can be blood.

[0027] The contrast agent can include microbubbles. These produce strong ultrasonic reflections.

[0028] In at least one group of embodiments, the ultrasonic data includes each ultrasonic signal obtained from each of at least three consecutive ultrasonic pulses, two of these three pulses having a first power level and the third of these three pulses having a second power level different from the first power level. In particular, the received ultrasonic data in this example may include data corresponding to a plurality of transmission or scan lines. For each transmission line, the data may include a group of each ultrasonic signal obtained from each of at least three consecutive ultrasonic pulses.

[0029] Generally, a contrast agent in a fluid region may have a non-linear response as a function of the power of an ultrasonic pulse. This is especially true when the fluid contains a microbubble-based contrast agent. By varying the power level between pulses, due to the different power responses of tissue and contrast agent, this means that the source ultrasonic data includes information that enables a distinction between tissue regions and fluid regions within the ultrasonic data.

[0030] In at least one group of examples, the second power level can be twice the first power level, and the first image generation procedure has the step of generating a first image based on a combination of a signal from a third pulse having the second power level and at least one of the signals from two pulses having the first power level.

[0031] By generating a first image based on a combination of data obtained at two different power levels, fluid can be selectively emphasized and tissue suppressed.

[0032] By using three consecutive pulses from the same acquisition period or event, the inherent spatial alignment between the ultrasonic signals from these three pulses is ensured.

[0033] In at least one group of examples, the second image generation procedure includes generating a second image based on an ultrasonic signal from only one of the three pulses. In this way, the second image is, in effect, a linear image or a base image generated from ultrasonic data from a single one of the plurality of pulses without being combined with other received pulse signals.

[0034] In at least one group of examples, the second image generation procedure includes generating a second image based on an ultrasonic signal from a third pulse having a second power level. Thereby, the power of the third signal is maximized, and the overall visibility of the characteristic structure shown in the second image is maximized.

[0035] In at least one group of examples, the first image generation procedure includes: generating a sum signal by adding ultrasonic signals from two pulses having a first power level; determining a difference signal based on determining a difference between the sum signal and a signal from a third pulse; and generating a first image based on the difference signal.

[0036] Due to the different power-dependent responses of the tissue and the contrast agent-containing fluid, the sum signal provides a contrast response different from the signal from the third pulse. The difference signal represents the difference in this response and thus provides the maximum contrast between the tissue and the fluid.

[0037] The power levels of the different pulses can be configured by adjusting the amplitudes of the transmitted ultrasonic pulses.

[0038] According to one or more embodiments, the object of interest includes at least a part of a subject's heart. The one or more tissue boundaries may include an endocardium in a specific example, and the fluid receiving region includes a ventricle and / or an atrium.

[0039] According to the above embodiments, the method further includes a step of generating a display output for displaying both the first image and the second image on the display device, and preferably, further displaying the representation of one or more determined tissue boundaries. This configuration helps a clinician using the system to evaluate the heart structure and draw a diagnostic conclusion.

[0040] An example according to another aspect of the present invention provides a computer program product having code means which, when executed on a processor, are configured to cause the processor to execute a method according to any example or embodiment described above or below, or according to any claim of the present application.

[0041] An example according to another aspect of the present invention provides a processing device having an input / output unit; and at least one processor. The at least one processor is configured to receive, at the input / output unit, ultrasonic data representing an anatomical region including an object of interest including one or more tissue boundaries. The one or more tissue boundaries are adjacent to a fluid receiving region. The ultrasonic data consists of data regarding a single acquisition event. The at least one processor is configured to apply a first image generation procedure to the ultrasonic data to generate a first image, and the first image generation procedure is configured to suppress the visibility of tissue regions in the resulting first image and / or enhance the visibility of fluid within the fluid receiving region in the generated first image. The processing device is further configured to apply a second image generation procedure different from the first image generation procedure to the ultrasonic data to obtain a second image. The processing device is further configured to apply an image segmentation procedure to both the first and second images. The processing device is further configured to determine one or more tissue boundaries based on the segmentation procedure. The processing device is further configured to generate a data output representing the determined one or more tissue boundaries.

[0042] The fluid receiving region preferably contains a fluid containing a contrast agent. Preferably, the method does not include the step of administering a contrast agent.

[0043] In at least one group of embodiments, the ultrasonic data includes ultrasonic signals each obtained from each of at least three consecutive ultrasonic pulses, two of these three pulses having a first power level and the third of these three pulses having a second power level different from the first power level.

[0044] In at least one example, the second power level can be twice the first power level, and the first image generation procedure has the step of generating a first image based on a combination of a signal from the third pulse having the second power level and at least one of the signals from the two pulses having the first power level.

[0045] Another aspect of the present invention provides an ultrasonic system comprising: an ultrasonic probe having a transducer array for acquiring ultrasonic data; a display device; and a processing device according to any example or embodiment described above or below, or according to any claim of the present application.

[0046] These and other aspects of the present invention will become apparent from and be elucidated with reference to the embodiments described hereinafter.

[0047] For a better understanding of the present invention and to more clearly show how the present invention is implemented, the accompanying drawings will be referred to by way of example only. BRIEF DESCRIPTION OF THE DRAWINGS

[0048]

Figure 1

Figure 2

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[0049] The present invention will be described with reference to the drawings.

[0050] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, system and method, are for the purpose of illustration only and are not intended to limit the scope of the invention. These and other features, aspects and advantages of the apparatus, system and method of the present invention will be better understood from the following description, appended claims and accompanying drawings. It should be understood that the figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the drawings to indicate the same or similar parts.

[0051] The present invention provides a method for determining one or more tissue boundaries in ultrasonic data of an anatomical region. This method is based on generating two separate images from the same input ultrasonic data acquired in a single acquisition session. One image is generated with contrast enhancement to make the boundaries surrounding fluid-containing regions particularly visible, while the second image is generated without or with other enhancements to make the boundaries surrounding tissue regions particularly visible. Then, the combination of both images is used as an input and an image segmentation procedure for determining the boundaries within the imaging region is applied.

[0052] In other words, embodiments of the present invention propose to improve the determination of related anatomical structures by simultaneously applying segmentation to two different images generated from data acquired in a single scan. The first image is constructed, for example, while suppressing tissue signals, for the purpose of maximizing the signal from the contrast agent-containing region. The second image is derived from the ultrasonic data, particularly in the context of LVO (see above description) with respect to the visibility of the mitral annulus, for the purpose of providing a greater relative visibility of the tissue signals.

[0053] By exploring the boundary feature structures in both images during the mesh adaptation process, complementary information of the two images can be used for improved segmentation and thus for more accurate determination of cardiac measurements such as ejection fraction.

[0054] Steps of an exemplary computer-implemented method 10 according to one or more embodiments are shown in FIG. 1.

[0055] Method 10 has a step 12 of receiving ultrasonic data from an anatomical region including an object of interest including one or more tissue boundaries adjacent to a fluid receiving region.

[0056] Method 10 further has a step 14 of applying a first image generation procedure to the ultrasonic data to generate a first image, the first image generation procedure being adapted to suppress the visibility of tissue regions in the generated first image and / or enhance the visibility of fluid within the fluid receiving region in the generated first image.

[0057] Method 10 further has a step 16 of applying a second image generation procedure different from the first image generation procedure to the ultrasonic data to obtain a second image.

[0058] Method 10 further has a step 18 of applying an image segmentation procedure to both the first and second images. The one or more tissue boundaries are determined based on the segmentation procedure, or one or more tissue boundaries may be determined as a result of the segmentation procedure. Preferably, the image segmentation procedure is a combined segmentation that uses both images in combination to achieve segmentation. As will be described in more detail later, the image segmentation can be automatically adapted based on information derived from the mesh shapes of both images.

[0059] Method 10 further has a step 20 of generating a data output representing the determined one or more tissue boundaries.

[0060] The received ultrasonic data is composed of data from a single acquisition event or session (e.g., a single scan). A single acquisition event can mean data obtained from a single acquisition sequence, for example, a single continuous or non - interrupted sequence of one or more ultrasonic pulses and received echoes, or a series of acquisition scan lines (each of which can have one or more ultrasonic pulses).

[0061] The fluid receiving region preferably contains a fluid containing a contrast agent. The method can be performed after the contrast agent is administered. In a preferred embodiment, the method does not include the step of administering a contrast agent.

[0062] The ultrasonic data can be received in real - time from an ultrasonic imaging device or from an ultrasonic transducer unit. Alternatively, the ultrasonic data can also be received from a data store in which data was recorded in a previous data acquisition session. The ultrasonic data can be ultrasonic echo data, for example, RF echo data. As another example, the ultrasonic data can be partially post - processed data, for example, beam - formed RF data. The data is not yet in the form of a reconstructed image.

[0063] The first image generation procedure can have a series of post - processing steps applied to the received ultrasonic data and a series of image reconstruction steps for then creating an image from the processed data. The above - mentioned post - processing steps have the effect of enhancing (highlighting) the visibility of the fluid within the fluid receiving region and / or suppressing the visibility of tissue in the resulting (first) image as compared to an image generated from the received ultrasonic data without these post - processing steps. The visibility of these regions is emphasized / suppressed as compared to a second image that would be generated by a second image generation procedure.

[0064] The second image generation procedure has a step of generating a second image from the received ultrasonic data. The second image generation procedure may or may not include a post - processing step applied to the received ultrasonic data before reconstructing the image. If the procedure includes such steps, these steps are configured to have the effect of emphasizing the tissue region and / or suppressing the fluid within the fluid receiving region in the resulting (second) image as compared to the image reconstruction performed on the received ultrasonic data without these steps and as compared to the first image.

[0065] To avoid ambiguity, the images are referred to as the first and second images, but it should be noted that this does not constrain the order in which these images are generated. For example, the second image may be generated before the first image.

[0066] The segmentation procedure will be described in detail below. The procedure may have a step of generating a 3D mesh representing the position of one or more boundaries within the received ultrasonic data.

[0067] Here, features according to a group of preferred embodiments are outlined.

[0068] According to this at least one group of embodiments, the general objective is to generate two images by a dual-path processing approach from a group of received ultrasonic pulses transmitted and received during a single acquisition process and use both of them as inputs for model-based segmentation. Hereinafter, a first image, which may be called a contrast (contrast-enhanced) image, may be based on a typical pulse scheme used for contrast agent imaging. This is designed such that the signal from the contrast agent (e.g., contrast agent microbubbles) is enhanced while the tissue signal is minimized. A second image, which may be called a linear image, is constructed for the purpose of achieving a strong tissue signal. Using both images results in complementary information. The above linear image can be used to detect the boundaries of tissue portions of small dimensions (e.g., thinner) that may otherwise become unclear due to blurring or bleeding outside the boundaries of a strong contrast-enhanced signal.

[0069] As an example, in a specific pre- and post-situation of an echocardiogram (e.g., the left ventricular contrast imaging (LVO) described above), the (first) image with enhanced contrast enables a clear depiction of the endocardial boundary, while the linear image (the second image) can be used to determine the position of the mitral valve annulus that defines the boundary between the left ventricle and the left atrium.

[0070] In the segmentation procedure, both images can be used in parallel to detect boundaries.

[0071] This is schematically shown in Figure 2, which shows a processing apparatus 32 adapted to execute a computer-implemented method according to an embodiment of the present invention. As a result of applying first and second image generation procedures to received ultrasonic data, a first image 42 and a second image 44 are generated. Figure 2 shows an example of these two images for received data representing the left ventricle (shown as LV in the image) and the left atrium (LA). The first image is a contrast-enhanced image, and it can be seen that the cardiac cavities (containing blood with contrast agent) appear bright while the tissue region 46 appears dark. The second image 44 is a linear (second) image, and it can be seen that the tissue 46 appears brighter while the fluid region appears darker. The solid grey lines schematically show strong visible depictions between adjacent structures, while the dotted grey lines correspond to weak depictions. It can be seen that the boundary between the left ventricle (LV) and the left atrium (LA) is not visible at all in the first image 42.

[0072] Figure 2 further shows an exemplary boundary surface mesh 54 generated by segmentation applied to both the first image 42 and the second image 44 together.

[0073] By using both images 42, 44 as inputs, it is possible to achieve segmentation that benefits from distinct endocardial image feature structures specific to contrast agent microbubbles while accurately identifying the boundary between the left ventricle and the atrium. This facilitates more accurate automatic derivation of cardiac measurements such as ejection fraction.

[0074] Here, one exemplary approach for generating the first and second images is outlined.

[0075] In this approach, it is assumed that the subject's blood contains a contrast agent, for example a microbubble-containing contrast agent.

[0076] Generally, contrast imaging techniques are based on the property that tissue exhibits a more linear response to ultrasound than microbubbles of a contrast agent. One such technique in contrast imaging is called power modulation and utilizes the relatively linear response of tissue when the mechanical index or output acoustic amplitude is varied. Power modulation is composed of three or more transmit pulses (as part of a single transmit sequence) all along the same acoustic path.

[0077] In particular, the received ultrasound data in this example includes data corresponding to a plurality of transmit or scan lines. For each transmit line, the data includes a group of ultrasound signals obtained from each of at least three consecutive ultrasound pulses. Two of the three pulses have a first power level. The third of the three pulses has a second power level different from the first power level. The power level can be changed by changing the acoustic amplitude of the signal. These pulses are labeled as first, second, and third, but this does not constrain the order in which these pulses are generated. After each ultrasound pulse, a corresponding echo signal is received, so the received ultrasound data for each transmit line has a set of three consecutive echo signals.

[0078] By varying the power level between pulses and according to the different power responses of tissue and fluid, this means that the source ultrasound data contains information that enables the tissue and fluid to be distinguished within the ultrasound data.

[0079] In at least one group of embodiments, the second power level can be set to twice the first power level. This can be approximately twice, for example, twice + / - 5% or + / - 10%. The first image generation procedure can include generating a first image (contrast-enhanced image) based on a combination of a signal from the third pulse having the second power level and at least one of the signals from the two pulses having the first power level.

[0080] By generating a first image based on a combination of data acquired at two different power levels, it is possible to selectively enhance the fluid and suppress the tissue. Further, by using three consecutive pulses from the same acquisition period or event, the inherent spatial alignment between the ultrasonic signals from the three pulses is ensured.

[0081] The first and second pulses are effectively at half amplitude, and the third pulse is at full amplitude. This set of embodiments proposes constructing two separate images by processing this group of pulses in a dual-path approach.

[0082] Regarding the first image (contrast-enhanced image), the image can be constructed by adding the first and second pulses of each scan line and subtracting this result from the third pulse.

[0083] In other words, the first image generation procedure may include: generating a sum signal by adding ultrasonic signals from two pulses having a first power level for each scan line; determining a difference signal based on determining the difference between the sum signal and the signal from the third pulse for each scan line; and generating a first image based on the difference signal for a plurality of scan lines.

[0084] Since the tissue is much more linear than the contrast agent, the tissue signal is mostly suppressed, leaving only the much more non-linear contrast agent signal.

[0085] Regarding the second image (linear image), the second image generation procedure may include generating the second image based on the ultrasonic signal from only one of the three pulses for each scan line, for example, the ultrasonic signal from the third pulse having a second power level. In other words, the linear image is derived from simply a single pulse (e.g., the third pulse having full amplitude) for each scan line, thus resulting in an unsuppressed tissue signal.

[0086] Since both images are constructed from the same set of pulses for each scan line, these images are spatially aligned and thus no additional alignment step is required. This approach is in contrast to an approach that, for example, required generating data in two acquisition sessions, one before and one after administration of a contrast agent. In this case, misalignment between the two fields of view is expected due to the delay period between the first and second acquisition sessions.

[0087] In the above embodiment, the second image is generated from the data of only a single ultrasound pulse, but this is not essential. In other variants, the second image generation procedure may include a processing procedure applied to the received ultrasound data to selectively enhance the visibility of tissue and / or selectively suppress the visibility of fluid.

[0088] When the first and second images are generated, the method further has a step of applying an image segmentation procedure to both of these images. The procedure is preferably an integrated or combined segmentation procedure from which a single segmentation is derived from a combination of both the first and second images.

[0089] By way of example, segmentation based on an anatomical model can be used. One skilled in the art will be aware of a number of different model-based segmentation algorithms in the art.

[0090] In some examples, the combined application of segmentation to both the first and second images can be achieved using known multi-modal segmentation methods, such as those used in the combined analysis of CT and MRI images and the like. One example is outlined, for example, in the publication: Buerger C., Peters J. et al. (2014) Multi-modal Vertebra Segmentation from MR Dixon for Hybrid Whole-Body PET / MR. In: Yao J., Klinder T., Li S. (eds) Computational Methods and Clinical Applications for Spine Imaging. Lecture Notes in Computational Vision and Biomechanics, vol 17. Springer, Cham.

[0091] Details of exemplary multi-modal segmentation methods can also be found in the document WO2015 / 189160.

[0092] In summary, the segmentation procedure has a step of fitting a boundary mesh within the image data by searching for a boundary feature structure and adapting the mesh shape to match the boundary feature structure. When searching for a boundary feature structure for a given mesh triangle, intensity profiles can be sampled along the normal of the triangle in both the first and second images. If a sufficiently strong feature structure is found in either of the two images, this can be used to pull the mesh towards that point. Optionally, the relative weights of the boundary feature structures in the two images can be determined, which is used, for example, as a further parameter (hyperparameter) within the segmentation procedure.

[0093] According to the above-described embodiments, when the imaging region is the heart, particularly the left ventricle and atrium, the method may further include determining one or more hemodynamic parameters based on the determined tissue boundaries. For example, the cardiac output can be determined based on tracking the change in left ventricular volume over a single cardiac cycle. The change in left ventricular volume can be determined by tracking the change in the outer perimeter of the left ventricle that can be determined from the segmentation. The received ultrasonic data may include data at a series of time points over at least one cardiac cycle. The method described in the present disclosure can be repeatedly applied to the data for each of these different time points.

[0094] The method further includes generating a data output representing the determined one or more tissue boundaries. This output can simply be a data package that transmits data representing the derived boundaries, such as the coordinates of a group of triangles of a mesh. Additionally or alternatively, the output can be an output for providing a visual representation of the identified one or more boundaries.

[0095] For example, according to at least one group of embodiments, the method may include generating a display output for displaying the determined one or more boundaries on a display device. This output can be superimposed or overlaid, for example, on one or both of the first and second images. Each of the first and second images more clearly shows different boundary feature structures. That is, the first one more clearly shows the internal boundary of the heart cavity, while the second one more clearly shows the mitral valve. By presenting both the first and second images on the display with the generated boundary mesh superimposed on each of them, the user can identify / locate both different types of boundary feature structures within the relevant images.

[0096] The display device can be a display unit and a user interface having user input means as an option.

[0097] The user interface may include a function that enables the user to manually adjust the derived segmentation. For example, in the case of an echocardiogram, there may be a function that enables the user to adjust the position of the mitral valve surface that can be (mainly) seen in a linear image where tissue signals are not suppressed.

[0098] As described above, a preferred application is for segmenting the boundaries of heart cavities and structures. Thus, in this case, the object of interest represented in the ultrasonic data includes at least a part of the subject's heart.

[0099] The one or more tissue boundaries can include the endocardium, and the fluid-containing region can include ventricular cavities and / or atrial cavities.

[0100] However, other applications are also possible. Generally, any region containing a fluid-receiving cavity or lumen surrounded by tissue boundaries can be a valuable application area for embodiments of the present invention. Examples can include the colon or small intestine, the stomach, or some other fluid-receiving organ.

[0101] An example according to another aspect of the present invention provides a computer program product including code means configured to cause a processor to execute, when executed on the processor, a method according to any example or embodiment described above or below, or according to any claim of the present application.

[0102] An example according to another aspect of the present invention provides a processing apparatus having an input / output unit and at least one processor, the processor being: - receiving, at the input / output unit, ultrasonic data representing an anatomical region including an object of interest including one or more tissue boundaries, where the tissue boundaries are adjacent to a fluid-receiving region, and the ultrasonic data consists of data regarding a single acquisition event; - Apply a first image generation procedure to the ultrasonic data to generate a first image, where the first image generation procedure is adapted to suppress the visibility of tissue regions in the resulting first image and / or enhance the visibility of fluid within the fluid receiving region in the generated first image; - Apply a second image generation procedure to the ultrasonic data to obtain a second image, where the second image generation procedure is different from the first image generation procedure; - Apply an image segmentation procedure to both the first and second images; - Determine one or more tissue boundaries based on the segmentation procedure; and - Generate a data output representing the determined one or more tissue boundaries; configured to be as follows.

[0103] The implementation options and details regarding each of the features of the above processing device can be understood and interpreted according to the descriptions and explanations provided above regarding aspects of the method of the present invention. Any of the examples, options, features or details of the embodiments described above regarding the method can be applied, combined or incorporated into the aspects of the present processing device of the invention with the necessary modifications.

[0104] Figure 3 schematically shows the components of an exemplary system that may be provided according to another aspect of the present invention. The system includes a processing device 32 according to any of the examples or embodiments described above or below, or according to any of the claims of the present application. The processing device 32 includes an input / output unit 34 and a processor 36 operably coupled to the input / output unit. The processing device is configured to receive ultrasonic data from an ultrasonic transducer unit 62 operably coupled to the input / output unit 34. The ultrasonic transducer unit may include, for example, an ultrasonic probe. The ultrasonic transducer unit includes one or more ultrasonic transducers for acquiring ultrasonic data, for example, a transducer array. A display device 64 operably coupled to the input / output unit is also further provided.

[0105] According to any of the above aspects and embodiments of the present invention, the ultrasonic data may be received in real time from an ultrasonic imaging device, or may be received after acquisition from, for example, a data store in which acquired ultrasonic data is recorded. In the former case, the method may include a step of acquiring ultrasonic data. To further assist in understanding the present invention, for example, data acquisition and / or image reconstruction, the general operation of an exemplary ultrasonic system will be described herein with reference to FIG. 4.

[0106] The system includes an array transducer probe 104 having a transducer array 106 for transmitting ultrasonic waves and receiving echo information. The transducer array 106 may have CMUT transducers; piezoelectric transducers formed from materials such as PZT or PVDF; or some other suitable transducer technology. In this example, the transducer array 106 is a two-dimensional array of transducers 108 that can scan either a 2D plane or a three-dimensional volume of the region of interest. In other examples, the transducer array may be a one-dimensional array.

[0107] The transducer array 106 is coupled to a microbeamformer 112 that controls the reception of signals by the transducer elements. The microbeamformer enables at least partial beamforming of signals received by sub-arrays (commonly referred to as "groups" or "patches") of transducers, as described in U.S. Patent Nos. 5,997,479 (Savord et al.), 6,013,032 (Savord), and 6,623,432 (Powers et al.).

[0108] Note that the above microbeamformer is generally entirely optional. Further, the system can incorporate the microbeamformer 112 and switch the array between transmit and receive modes, and includes a transmit / receive (T / R) switch 116 that protects the main beamformer 120 from high energy transmit signals when the microbeamformer is not used and the transducer array is operated directly by the beamformer of the main system. Transmission of the ultrasonic beam from the transducer array 106 is directed by the T / R switch 116 and a transducer controller 118 coupled to the microbeamformer by the main transmit beamformer (not shown), which controller can receive input from user operations of a user interface or control panel 138. The controller 118 can include a transmit circuit configured to drive the transducer elements of the array 106 (either directly or via the microbeamformer) during the transmit mode.

[0109] The functions of the control panel 138 in this exemplary system can be facilitated by an ultrasonic controller unit according to an embodiment of the present invention.

[0110] In a typical line-by-line imaging sequence, the beamforming system in the probe operates as follows. During transmission, the beamformer (either a microbeamformer or the main system beamformer depending on the configuration) activates the transducer array or a sub-aperture of the transducer array. A sub-aperture can be a one-dimensional line of transducers or a two-dimensional patch of transducers within a larger array. In the transmit mode, focusing and steering of the ultrasonic beam generated by the array or the sub-aperture of the array are controlled as described below.

[0111] When a backscattered echo signal is received from a subject, the received signal undergoes beamforming processing (described below) to align the received signal. When sub-apertures are used, the sub-apertures are then shifted, for example, by only one transducer element. The shifted sub-apertures are then activated, and the process is repeated until all transducer elements of the transducer array are activated.

[0112] For each line (or sub-aperture), the total received signal used to form the relevant line of the final ultrasonic image will be the sum of the voltage signals measured by the transducer elements of a given sub-aperture during the reception period. The line signal as a result after the following beamforming process is usually called radio frequency (RF) data. Each line signal (RF data set) generated by various sub-apertures then undergoes additional processing to generate the lines of the final ultrasonic image. The change in the amplitude of the line signal over time contributes to the change in the brightness of the ultrasonic image with depth, in which case a high-amplitude peak will correspond to a bright pixel (or set of pixels) in the final image. Peaks appearing near the start of the line signal represent echoes from shallow structures, while peaks appearing increasingly later in the line signal represent echoes from increasingly deeper structures within the subject.

[0113] One of the functions controlled by the transducer controller 118 is the direction in which the beam is steered and focused. The beam can be steered straight forward (orthogonal to) from the transducer array, or at various angles for a wider field of view. The steering and focusing of the transmit beam can be controlled as a function of the drive time of the transducer elements.

[0114] In general ultrasonic data acquisition, two methods can be distinguished, namely plane wave imaging and "beam steering" imaging. These two methods are distinguished by the presence of beam forming processing in the transmission mode ("beam steering" imaging) and / or the reception mode (plane wave imaging and "beam steering" imaging).

[0115] First, looking at the focusing function, by activating all transducer elements simultaneously, the transducer array generates a plane wave that diverges as it passes through the subject. In this case, the ultrasonic beam remains unfocused. By introducing a position-dependent time delay in the activation of the transducer, the wavefront of the beam can be focused at a desired point (referred to as the focal zone). The focal zone is defined as the point where the lateral beam width is less than half of the transmitted beam width. In this way, the lateral resolution of the final ultrasonic image is improved.

[0116] For example, if the time delay activates the transducer elements in a sequence (order) starting from the outermost elements of the transducer array and ending at the central element, the focal zone will be formed at a given distance from the probe along the central element. The distance of the focal zone from the probe varies depending on the time delay between subsequent rounds of activation of the transducer elements. After the beam passes through the focal zone, the beam begins to diverge and forms a far-field imaging region. Note that for a focal zone located close to the transducer array, the ultrasonic beam diverges rapidly in the far field, resulting in beam width artifacts in the final image. Usually, the near field located between the transducer array and the focal zone shows little detail because of the large overlap of the ultrasonic beams. Thus, changing the position of the focal zone can cause a significant change in the quality of the final image.

[0117] Note that in the transmission mode, only one focus can be defined unless the ultrasonic image is divided into multiple focal zones (each of which can have a different transmission focus).

[0118] Furthermore, when receiving echo signals from within a subject, the reverse of the above-described process can be executed to perform reception focusing. In other words, an incoming signal can be received by a transducer element and an electronic time delay can be applied before being passed to the system for signal processing. The simplest example of this is called delay-and-sum beamforming. It is possible to dynamically adjust the reception focusing process of the transducer array as a function of time.

[0119] Turning now to the function of beam steering, by correctly applying a time delay to the transducer elements, a desired angle can be imparted to the ultrasonic beam as it leaves the transducer array. For example, by activating the transducers on the first side of the transducer array in an order that the remaining transducers follow and end on the opposite side of the array, the wavefront of the beam will be tilted towards the second side. The magnitude of the steering angle with respect to the normal of the transducer array depends on the magnitude of the time delay during the activation of the subsequent transducer elements.

[0120] Furthermore, it is also possible to focus the steered beam, in which case the total time delay applied to each transducer element is the sum of both the focusing and steering time delays. In this case, the transducer array is called a phased array.

[0121] In the case of CMUT transducers that require a DC bias voltage for activation, the transducer controller 118 can be coupled to control a DC bias control unit 145 for the transducer array. The DC bias control unit 145 sets the DC bias voltage applied to the CMUT transducer elements.

[0122] For each transducer element of the transducer array, an analog ultrasonic signal (usually called channel data) is input into the system via a receive channel. In the receive channel, a partially beamformed signal is generated from the channel data by the microbeamformer 112 and then passed to the main receive beamformer 120, where the partially beamformed signals from the individual patches of the transducer are combined into a fully beamformed signal (referred to as radio frequency (RF) data). The beamforming process performed at each stage can be carried out as described above or can include additional functions. For example, the main beamformer 120 can have 128 channels, each of which receives a partially beamformed signal from a patch of dozens or hundreds of transducer elements. In this way, signals received by thousands of transducers in the transducer array can efficiently contribute to a single beamformed signal.

[0123] The beamformed received signal is coupled to the signal processor 122. The signal processor 122 can process the received echo signal in various ways such as bandpass filtering; decimation; I and Q component separation; and harmonic signal separation; etc., and the harmonic signal separation acts to separate linear and non-linear signals to enable the identification of non-linear (harmonics of the fundamental frequency) echo signals returned from tissue and microbubbles. The signal processor can also perform additional signal enhancement such as speckle reduction, signal synthesis, and noise removal. The bandpass filter in the signal processor can be a tracking filter, and its passband slides from a higher frequency band to a lower frequency band as the depth from which the echo signal is received increases, thereby removing higher frequency noise from greater depths that usually lack anatomical information.

[0124] The beamformers for transmission and reception can be implemented with different hardware and can have different functions. Of course, the receive beamformer is designed taking into account the characteristics of the transmit beamformer. In FIG. 4, for simplicity, only the receive beamformers 112, 120 are shown. A complete system would also include a transmit chain with a transmit microbeamformer and a main transmit beamformer.

[0125] The function of the microbeamformer 112 is to provide an initial combination of signals in order to reduce the number of analog signal paths. This is typically performed in the analog domain.

[0126] The final beamforming is performed by the main beamformer 120, typically after digitization.

[0127] The transmit and receive channels use the same transducer array 106 with a fixed frequency band. However, the bandwidth occupied by the transmit pulse can vary depending on the transmit beamforming used. The receive channel can capture the entire transducer bandwidth (this is the classical approach), or by using bandpass processing, extract only the bandwidth containing the desired information (e.g., the harmonics of the main harmonic).

[0128] The RF signal can then be coupled to a B-mode (i.e., luminance mode, or 2D imaging mode) processor 126 and a Doppler processor 128. The B-mode processor 126 performs amplitude detection on the received ultrasonic signal for imaging structures within the body such as organ tissue and blood vessels. In the case of line-by-line imaging, each line (beam) is represented by a related RF signal, the amplitude of which is used to generate a luminance value to be assigned to a pixel within the B-mode image. The exact position of a pixel within the image is determined by the position of the related amplitude measurement along the RF signal and the RF signal line (beam) number. A B-mode image of such a configuration can be formed in a harmonic or fundamental image mode, or a combination of both, as described in U.S. Patent No. 6,283,919 (Roundhill et al.) and U.S. Patent No. 6,458,083 (Jago et al.). The Doppler processor 128 processes temporally different signals resulting from tissue movement and blood flow for the detection of moving substances such as the flow of blood cells within the image field. The Doppler processor 128 typically includes a wall filter having parameters set to pass or block echoes returned from selected types of substances within the body.

[0129] The structural and motion signals generated by the B-mode processor and the Doppler processor are coupled to a scan converter 132 and a multi-planar reformatter 144. The scan converter 132 arranges the received echo signals of the spatial relationship in a desired image format. In other words, the scan converter acts to convert the RF data from a cylindrical coordinate system to a Cartesian coordinate system suitable for displaying an ultrasonic image on the image display 140. In the case of B-mode imaging, the luminance of a pixel at a given coordinate is proportional to the amplitude of the RF signal received from that position. For example, the scan converter can arrange the echo signals in a two-dimensional (2D) sector format or a pyramidal three-dimensional (3D) image. The scan converter can superimpose a color corresponding to the movement at each point in the image field on the B-mode structural image, in which case the Doppler estimated velocity generates a given color. The synthesized B-mode structural image and the color Doppler image depict the movement of tissue and blood flow within the structural image field. The multi-planar reformatter converts the echoes received from points in a common plane in a volume region of the body into an ultrasonic image of the plane, as described in U.S. Patent No. 6,443,896 (Detmer). The volume renderer 142 converts the echo signals of the 3D data set into a projected 3D image as viewed from a given reference point, as described in U.S. Patent No. 6,530,885 (Entrekin et al.).

[0130] 2D or 3D images are combined from the scan converter 132, multi-planar re-formatter 144, and volume renderer 142 to the image processor 130 for further enhancement, buffering, and temporary storage for optional display on the image display 140. The image processor can be adapted to remove specific imaging artifacts from the final ultrasonic image, such as acoustic shadows caused by strong attenuation or refraction; post-enhancement caused by, for example, weak attenuation; reverberation artifacts when, for example, highly reflective tissue interfaces are located in the immediate vicinity; etc. Further, the image processor can be adapted to perform specific speckle reduction functions to improve the contrast of the final ultrasonic image.

[0131] In addition to being used for imaging, the blood flow values generated by the Doppler processor 128 and the tissue structure information generated by the B-mode processor 126 are combined to the quantification processor 134. The quantification processor generates measurement values of different flow states, such as the flow rate of blood flow, in addition to structural measurements such as the size of the organ and the gestational age. The quantification processor can receive inputs from the user control panel 138, such as points within the anatomical structure of the image on which the measurement is to be made.

[0132] The output data from the above-described quantification processor is coupled to the graphics processor 136 to reproduce the measurement graph and values along with the image on the display 140 and to perform audio output from the display device 140. The graphics processor 136 can also generate a graphic overlay for display along with the ultrasonic image. These graphic overlays can include standard identification information such as patient name, image date and time, imaging parameters, etc. For these purposes, the graphics processor receives an input such as the patient name from the user interface 138. The user interface is also coupled to the transmission controller 118 to control the generation of ultrasonic signals from the transducer array 106 and thus the images generated by the transducer array and the ultrasonic system. The transmission control function of the controller 118 is only one of the functions to be executed. The controller 118 also takes into account the operating mode (given by the user) and the corresponding required transmission configuration and bandpass configuration in the analog / digital converter of the receiver. The controller 118 can be a state machine having a fixed state.

[0133] The user interface is also coupled to a multi-planar re-formatter 144 for selection and control of the planes of a plurality of multi-planar re-format (MPR) images that can be used to perform the measurements quantified in the image field of the MPR images.

[0134] The above-described embodiments of the present invention use a processing device. The processing device may generally have a single processor or multiple processors. The processing device may be disposed within a single housing device, structure, or unit, or may be distributed among multiple different devices, structures, or units. Thus, a reference to the processing device being adapted or configured to perform a particular step or task may correspond to the step or task being performed by any one or more of a plurality of processing components, either alone or in combination. Those skilled in the art will understand how such a distributed processing configuration may be implemented. The processing device includes a communication module or input / output section for receiving data and outputting the data to other components.

[0135] One or more processors of the above processing device can be implemented in various ways using software and / or hardware to perform the various necessary functions. A processor typically uses one or more microprocessors that can be programmed with software (e.g., microcode) to perform the necessary functions. A processor can be implemented as a combination of dedicated hardware for performing some functions and one or more programmed microprocessors and associated circuitry for performing other functions.

[0136] Examples of circuits that can be used in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application-specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs).

[0137] In various implementations, the processor can be associated with one or more storage media such as volatile and non-volatile computer memories like RAM, PROM, EPROM, and EEPROM. The storage media can be encoded with one or more programs that perform the necessary functions when executed on one or more processors and / or controllers. The various storage media may be fixed within the processor or controller, or may be portable such that one or more stored programs can be loaded into the processor.

[0138] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, by considering the drawings, the disclosure, and the appended claims. In the claims, the term "comprising" does not exclude other elements or steps, and the singular does not exclude the plural.

[0139] A single processor or other unit can perform the functions of several items recited in the claims.

[0140] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0141] A computer program can be stored / distributed not only by a suitable medium such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but also in other forms, such as via the Internet or other wired or wireless communication systems.

[0142] Note that when the term "adapted" is used in the claims or the description, it is intended that the term "adapted" be equivalent to the term "configured".

[0143] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. An operating method of a processing device having an input / output unit and at least one processor for determining tissue boundaries within an imaged anatomical region, the operating method comprising: a step in which the at least one processor receives ultrasonic data from an anatomical region including an object of interest including one or more tissue boundaries, the one or more tissue boundaries being adjacent to a fluid receiving region, and the ultrasonic data consisting of data regarding a single acquisition session; a step in which the at least one processor applies a first image generation procedure to the ultrasonic data to generate a first image; a step in which the at least one processor applies a second image generation procedure different from the first image generation procedure to the ultrasonic data to obtain a second image; a step in which the at least one processor applies an image segmentation procedure to both the first and second images; a step in which the at least one processor determines the one or more tissue boundaries based on the image segmentation procedure; a step in which the at least one processor generates a data output representing the determined one or more tissue boundaries and wherein the first image generation procedure results in suppressing the visibility of tissue regions in the generated first image as compared to the visibility of tissue regions in the second image and / or enhancing the visibility of fluid in the fluid receiving region in the generated first image as compared to the visibility of fluid in the fluid region in the second image; Operating method.

2. The operating method according to claim 1, wherein the fluid receiving region contains a fluid containing a contrast agent.

3. The operating method according to claim 2, wherein the ultrasonic data includes each ultrasonic signal acquired from each of at least three consecutive ultrasonic pulses, two of the at least three consecutive ultrasonic pulses having a first power level and a third of the at least three consecutive ultrasonic pulses having a second power level different from the first power level.

4. The second power level is twice the first power level. The first image generation procedure includes a step of generating the first image based on a combination of a signal from the third pulse having the second power level and at least one of the signals from the two pulses having the first power level. The operating method according to claim 3.

5. The operating method according to claim 4, wherein the second image generation procedure includes a step in which the at least one processor generates the second image based on the ultrasonic signal from only one of the at least three consecutive ultrasonic pulses.

6. The operating method according to claim 5, wherein the second image generation procedure includes a step in which the at least one processor generates the second image based on the ultrasonic signal from the third pulse having the second power level.

7. The first image generation procedure includes a step in which the at least one processor generates a sum signal by adding the ultrasonic signals from the two pulses having the first power level, a step in which the at least one processor determines a difference signal based on determining a difference between the sum signal and the signal from the third pulse, and a step in which the at least one processor generates the first image based on the difference signal The operating method according to any one of claims 4 to 6.

8. The operating method according to any one of claims 1 to 7, wherein the object of interest includes at least a part of the heart of the subject.

9. The operating method according to claim 8, wherein the one or more tissue boundaries include an endocardium, and the fluid receiving region includes a ventricle and / or an atrium.

10. The operating method according to any one of claims 1 to 9, wherein the at least one processor further includes a step of generating a display output for displaying both the first image and the second image on a display device.

11. The operating method according to claim 10, wherein the at least one processor further includes a step of generating a display output for further displaying a representation of the determined one or more tissue boundaries on a display device.

12. A computer program having code means for causing a processor to execute each step of the operating method according to any one of claims 1 to 11 when executed on the processor.

13. A processing device having an input / output unit and at least one processor, wherein the at least one processor: receives ultrasonic data representing an anatomical region including an object of interest including one or more tissue boundaries at the input / output unit, wherein the one or more tissue boundaries are adjacent to a fluid receiving region, and the ultrasonic data consists of data regarding a single acquisition session, applies a first image generation procedure to the ultrasonic data to generate a first image, applies a second image generation procedure different from the first image generation procedure to the ultrasonic data to obtain a second image, applies an image segmentation procedure to both the first and second images, determines the one or more tissue boundaries based on the image segmentation procedure, generates a data output representing the determined one or more tissue boundaries, wherein the first image generation procedure results in suppressing the visibility of the tissue region in the generated first image as compared to the visibility of the tissue region in the second image, and / or enhancing the visibility of the fluid in the fluid receiving region in the generated first image as compared to the visibility of the fluid in the fluid region in the second image, a processing device.

14. The processing device according to claim 13, wherein the fluid receiving region contains a fluid containing a contrast agent.

15. The ultrasonic data includes each ultrasonic signal obtained from each of at least three consecutive ultrasonic pulses, two of the at least three consecutive ultrasonic pulses having a first power level, and a third pulse of the at least three consecutive ultrasonic pulses having a second power level different from the first power level. The processing device according to claim 13 or 14.

16. An ultrasonic probe having a transducer array for acquiring ultrasonic data, a display device, and the processing device according to any one of claims 13 to 15 An ultrasonic system having.

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