Apparatus and method for evaluating dark field images

Abstract

An apparatus and method for evaluating dark-field images. The present invention relates to the use of dark-field X-ray images in the ablation treatment of tumors. By acquiring dark-field X-ray images showing the region of interest targeted during ablation treatment, information that allows for decisions regarding the termination of the ablation treatment can be derived. A set of dark-field X-ray images, acquired at different times and including the region of interest, is received (101). The set of dark-field X-ray images is compared (102) for example by identifying differences between individual images. If a change in the dark-field X-ray image over time is detected in the region of interest during this comparison, a signal indicating that a change has occurred is generated (103). This signal may indicate that healthy tissue, rather than a tumor, is being affected, and therefore the ablation treatment should be terminated.

Description

Technical Field

[0001] This invention generally relates to the field of methods and apparatus for monitoring dark-field X-ray images obtained during ablation treatment. Background Technology

[0002] Lung cancer is known to be a leading cause of cancer death. In most cases, lung cancer diagnosed at an advanced stage has a poor prognosis. There is a continuous tendency for it to progress.

[0003] A common treatment option for lung cancer is transbronchial or transthoracic radiofrequency ablation, which uses heat generated by an applied radiofrequency signal to ablate portions of the tumor's electrical conduction system. For transbronchial intervention, a bronchoscope with a needle is guided through the bronchus towards the tumor, and the needle tip is inserted into the tumor tissue. For transthoracic treatment, a needle is inserted into the tumor tissue through the pleural cavity. Subsequently, radiofrequency energy deposition is used to destroy the tumor.

[0004] A specific challenge in tumor ablation is ending the procedure at the right time. If the treatment ends too early, the tumor will not be completely destroyed. On the other hand, if it stops too late, healthy surrounding tissue will be damaged.

[0005] Therefore, more information is needed that can serve as a basis for deciding when to stop the ablation treatment. Summary of the Invention

[0006] The purpose of embodiments of the present invention is to provide a method for obtaining an indication of when to end the ablation process.

[0007] The above objectives are achieved by the solution according to the present invention.

[0008] In a first aspect, the present invention relates to an apparatus configured to acquire a set of dark-field X-ray images, including at least the region of interest, at two or more time points during an ablation procedure targeting a specific region of interest. It is possible to detect changes in the region of interest over time by monitoring the evolution of the thus acquired dark-field X-ray images. When a change is detected when comparing the acquired set of dark-field X-ray images, a signal indicating the occurrence of said change is generated. The presence of this signal can be used as a basis for determining the termination of the ablation procedure.

[0009] In another aspect, the present invention relates to a corresponding method.

[0010] The proposed solution does indeed allow for the acquisition of relevant information to determine whether to continue the ablation procedure. This invention utilizes the acquisition of dark-field X-ray images of the region of interest (e.g., tumor and surrounding tissue) during the ablation procedure. Such dark-field imaging is a modality that has recently gained attention due to its recognized potential for diagnostic purposes. The inventors have found that the application of dark-field X-ray imaging also provides benefits in the context of interventional procedures. More specifically, in the context of tumor treatment, the dark-field image of the tumor shows little or no change when ablation is performed. However, healthy lung tissue shows changes in its dark-field image once it has been heated during the procedure. Therefore, when using dark-field X-ray imaging, the differences in effect can be made visible. Thus, the proposed method provides useful information regarding the appropriate time to terminate the ablation procedure.

[0011] In embodiments of the invention, when comparing images, the determination of difference images between at least some of the dark-field X-ray images in the set is performed. The difference images provide a quantitative measure of any changes (if any) and thus allow for a decision regarding the termination of the procedure. Optionally, a specific threshold level may be set, and if the difference image contains one or more pixels exceeding that threshold level, a signal can be generated to indicate the change. The presence of such a signal can contribute information to the decision of whether to terminate the ablation procedure.

[0012] In this embodiment, segmentation of regions corresponding to the region of interest is performed within a set of dark-field X-ray images. This increases the accuracy of the comparison. Segmentation algorithms are well known in the art and are readily available.

[0013] In some embodiments, the method for evaluating dark-field X-ray images includes performing motion compensation on one or more of the dark-field images prior to the comparison. In this way, the effect of motion can be reduced or even eliminated before the actual comparison is performed. Motion can be caused, for example, by the breathing of a patient from whom the dark-field X-ray images are acquired. Reducing or eliminating this effect contributes to obtaining a more accurate comparison of the dark-field images.

[0014] The present invention also relates to a program executable on a programmable device containing instructions that, when run, perform the methods as described, and to a computer-readable medium on which the program is stored.

[0015] In one aspect, the present invention relates to a method for managing ablation procedures directed toward a region of interest, the method comprising:

[0016] -Initiate the ablation treatment of the region of interest.

[0017] - Acquire dark-field X-ray images including the region of interest during the ablation procedure.

[0018] -As previously described, evaluate the acquired dark-field X-ray images obtained at at least two different times.

[0019] - Receive in the control device a signal indicating the occurrence of changes in the region of interest of the dark-field X-ray image, the changes being detected during the evaluation.

[0020] - The ablation process is terminated via the control device.

[0021] In another aspect, the present invention relates to an apparatus for evaluating dark-field X-ray images acquired during ablation treatment, the ablation treatment being directed toward a region of interest present in the dark-field X-ray images. The apparatus includes:

[0022] - An image receiver for receiving a set of dark-field X-ray images acquired at a first time and at least a second time, including the region of interest.

[0023] - A comparator for performing a comparison of the dark-field X-ray images of the set at the first time point with those at least at the second time point.

[0024] - A signal generator for generating a signal indicating the occurrence of a change if a change is detected in the region of interest in the dark-field X-ray images acquired at the first time and at least the second time during the comparison.

[0025] For the purpose of summarizing the invention and the advantages achieved relative to the prior art, certain objects and advantages of the invention have been described above. It should be understood, of course, that not all of these objects or advantages may necessarily be achieved according to any particular embodiment of the invention. Therefore, for example, those skilled in the art will recognize that the invention may be implemented or practiced in such a way as to achieve or optimize one or more advantages as taught herein, rather than necessarily achieving other objects or advantages as can be taught or suggested herein.

[0026] The above and other aspects of the invention will become apparent from the embodiments described below, and will be illustrated with reference to the embodiments described below. Attached Figure Description

[0027] The present invention will now also be described by way of example with reference to the accompanying drawings, wherein similar reference numerals denote similarities.

[0028] Figure 1 The illustration shows the use of gratings in dark-field X-ray imaging.

[0029] Figure 2The illustration shows the appearance of the tumor and surrounding tissue before and after ablation.

[0030] Figure 3 A flowchart illustrating a method according to an embodiment of the present invention is shown.

[0031] Figure 4 An embodiment of an apparatus for evaluating dark-field X-ray images according to the present invention is illustrated.

[0032] Figure 5 The illustration shows a needle visible in a transmission image (top) obtained together with a dark-field X-ray image or in the dark-field X-ray image itself (bottom). Detailed Implementation

[0033] The invention will be described with reference to specific embodiments and certain accompanying drawings, but the invention is not limited thereto, but is defined only by the claims.

[0034] Furthermore, the terms "first," "second," etc., used in the specification and claims are used to distinguish similar elements and are not necessarily used to describe an order in time, space, sequence, or any other way. It should be understood that the terms thus used are interchangeable where appropriate, and embodiments of the invention described herein can operate in other orders than those described or illustrated herein.

[0035] It should be noted that the term "comprising" as used in the claims should not be construed as limited to the modules listed below; it does not exclude other elements or steps. Therefore, it should be interpreted as specifying the presence of features, integers, steps, or components as mentioned in the statements, but not excluding the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Thus, the scope of the expression "device comprising modules A and B" should not be limited to a device consisting solely of components A and B. This means that for the purposes of this invention, the only relevant components of the device are A and B.

[0036] Throughout this specification, references to "an embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the invention. Therefore, the appearance of the phrase "in one embodiment" or "in an embodiment" in various places throughout this specification does not necessarily refer to the same embodiment, but may refer to it. Furthermore, particular features, structures, or characteristics may be combined in one or more embodiments in any suitable manner, as will be apparent to those skilled in the art based on this disclosure.

[0037] Similarly, it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, drawing, or description thereof in order to simplify this disclosure and aid in understanding one or more of the various aspects of innovation. However, this approach of the disclosure should not be construed as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the following claims, the innovative aspects lie in fewer features than all of the features in a single foregoing disclosed embodiment. Therefore, the claims that follow the detailed description are hereby expressly incorporated into this detailed description, wherein each claim is an independent embodiment of the invention.

[0038] Furthermore, although some embodiments described herein include some but not others of features included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments, as will be understood by those skilled in the art. For example, any of the claimed embodiments in the following claims may be used in any combination.

[0039] It should be noted that the use of specific terms when describing certain features or aspects of the invention should not be construed as implying that the term is redefined herein to be limited to include any specific characteristic of the feature or aspect of the invention associated with that term.

[0040] Numerous specific details are set forth in the description provided herein. However, it should be understood that embodiments of the invention can be practiced without these specific details. In other examples, well-known methods, structures, and techniques have not been shown in detail to avoid obscuring the description.

[0041] This invention extends the application of dark-field X-ray imaging technology to interventional settings. More specifically, this invention proposes the use of dark-field X-ray imaging in the context of monitoring the treatment of diseases (e.g., lung diseases), and more specifically for obtaining information about when to terminate tumor ablation treatment.

[0042] Because the benefits of applying dark-field imaging for diagnostic purposes have been recognized, this technology has been successfully applied to the diagnosis of lung diseases such as chronic obstructive pulmonary disease (COPD), pulmonary fibrosis, and lung cancer.

[0043] Dark-field X-ray imaging relies on the use of a Talbot-Lau interferometer, in which multiple gratings are added to the X-ray beam path. Figure 1An illustration is provided. In the example shown, three gratings are inserted into the optical path. Typically, G0 and G2 are absorber gratings, and G1 is a phase grating. The dark-field image signal is generated by changes in refractive index at the micrometer scale. For lung imaging, the dark-field X-ray signal is primarily generated by the air-tissue interface in the alveoli. The X-ray dark-field signal is quantified by small-angle scattering occurring in the lung at the air-tissue interface. This allows dark-field imaging to be used for the diagnosis of lung diseases that alter the properties or concentration of alveoli in the lungs.

[0044] Dark-field X-ray imaging provides a tool for assessing structural changes in a region of interest under consideration, as contrast is generated by ultra-small-angle scattering at microstructures. Dark-field X-ray imaging is highly sensitive, for example, to distortions in the natural microanatomical structure of the lung. In healthy lung tissue, the prominent air-tissue interface causes significant X-ray scattering. However, in cancerous tissue, the air-tissue volume ratio is reduced due to uncontrolled cell proliferation and loss of alveolar space, and therefore X-ray scattering is greatly reduced. Information about the scattering properties of the lung can be retrieved by evaluating the setting of a specific interference pattern. Thus, when applying dark-field imaging techniques, a solid tumor produces negative contrast in the surrounding lung tissue, which scatters a great deal as a highly structured material. This observation forms the basis for the method proposed in this invention for evaluating dark-field images. Figure 2 Illustrations are provided. At the bottom, a schematic cross-section of the lung is shown at the start of the intervention, while on the right, the condition is depicted when the surrounding tissue is damaged and filled with fluid. Above, the appearance in dark-field images is shown. In the upper left, the tumor is shown as a dark spot in the lung. If the surrounding tissue is damaged, the dark spot increases in size and becomes even darker in the center.

[0045] In embodiments of the present invention, dynamic dark-field image acquisition is used to monitor the progress of ablation procedures targeting a specific region of interest. Figure 3 The document provides a flowchart of an embodiment of the proposed method 100 for evaluating dark-field X-ray images. In 101, a set of dark-field X-ray images acquired at at least two different times during an ablation procedure and including the region of interest is received. In 102, the dark-field images in the set are compared, and in 103, a signal indicating the occurrence of changes detected in the images over time is generated.

[0046] During ablation, a dataset of dark-field X-ray images at different times is acquired, whereby each image includes at least the region of interest. In some embodiments, automatic 2D registration of the acquired images can be provided. In some embodiments, fluorescence fluoroscopy acquisition is performed, thereby obtaining a continuous stream of X-ray images of at least the region of interest. For example, a sliding window dark-field acquisition can be employed, wherein a continuous sequence of images is acquired using periodic grid movement. For example, a step-grate can periodically move 0 / 3, 1 / 3, and 2 / 3 of its grating period or 0 / 5, 2 / 5, 4 / 5, 1 / 5, and 3 / 5 of its grating period (compared to a reference position). Alternatively, it can move 0 / 8, 3 / 8, 6 / 8, 1 / 8, 4 / 8, 7 / 8, 2 / 8, 5 / 8, or other sequences. In other embodiments, the set of dark-field images at different times is obtained from multiple separate, non-continuous images.

[0047] The common model for the measured x-ray intensity as a function of the grating position x is

[0048] I(x)=TI0(1+DV0cos(φ+ψ0+x / p))

[0049] Here, T, D, and φ are the transmission, dark field, and differential phase signals caused by the object, respectively, and I0, V0, and ψ0 are the blank scan intensity, fringe visibility, and fringe phase, respectively. All these quantities are typically variations on a per-pixel basis. Finally, p refers to the grating period. Since the blank scan parameters are obtained by measurement without the object, these are known during the intervention, and the task of phase retrieval is to estimate the parameters T, D, and φ. Three measurements at three different grating positions are sufficient to estimate these parameters, for example, at position 0, 1 / 3 of the grating period, and 2 / 3 of the grating period. If these grating positions are used periodically, then any three subsequent projections can be used for phase retrieval. Typically, some additional grating positions are obtained (e.g., 5 or 8 – see also above) to stabilize the estimation process.

[0050] The image receiver (2) of the device (1) used for evaluating dark-field X-ray images (see...) Figure 4The array is arranged to receive (101) a set of dark-field X-ray images. The comparator (3) then performs a comparison (102) of the acquired dark-field X-ray images. In some embodiments of the invention, this involves determining a difference image between the dark-field X-ray images in the set. In embodiments of the invention, the difference image is obtained directly by calculating a subtraction image of two dark-field X-ray images. By creating a difference image between pairs of images acquired at different times, possible changes in the region of interest over time can be readily observed. In other embodiments, a purely visual inspection of each image is performed to monitor the evolution of the region of interest in the X-ray image over time. In yet another embodiment, each image is evaluated independently, for example, by estimating the lesion size, and then a comparison is performed on the estimated lesion size to examine changes in the lesion size over time.

[0051] Changes at two (or more) time points can be, for example, changes in the size of the lesion in a dark-field image, such as differences in size exceeding a predetermined threshold. As mentioned above, when treated, the dark-field signal of the tumor shows almost no change because it is solid and remains solid. In contrast, once the ablation procedure begins to destroy healthy lung tissue, the affected lung tissue generates less dark-field signal. The destruction of lung tissue causes damage to the thin walls of the alveoli, fluid inflow, and therefore alveolar collapse. Consequently, the damaged tissue no longer generates a dark-field signal, and the size of the lesion in the dark-field image increases. Therefore, by acquiring and evaluating dark-field X-ray images during ablation, information about the correct timing for ending treatment can be obtained. This information about the change in lesion size can then be used with other available information to make a final decision about ending treatment.

[0052] The change can also be a shift in the shape of an object (e.g., a tumor) within the region of interest. For example, this could occur in the case of a blood vessel passing through a heated tumor, thereby damaging lung tissue along the vessel as the heat is carried away. This could result in linear structures connected to the tumor. Again, a threshold level can be used to define the presence of a change that should be indicated from which shape differences exist. The threshold level can be expressed based on one or more parameters indicating the shape of the object.

[0053] If a change over time is detected in a dark-field X-ray image of the region of interest during the procedure, a signal is generated in the signal generator (4) to indicate the occurrence of that change. This signal can be transmitted to the device (6) that controls the ablation procedure. Based on the reception of the signal, the control device (6) can then take necessary steps to terminate the ablation process. Alternatively or continuously, the signal can be transmitted to another device that, upon receiving the signal, can provide information (such as an image or text on a display or sound from a speaker), thereby allowing a decision on whether to continue the ablation process. This other device can also be a control device or integrated with a control device.

[0054] In embodiments of the invention, region-of-interest (ROI) segmentation in the dark-field image is performed before comparison begins. This can be beneficial for improving the accuracy of the comparison. Dark-field image segmentation can be automated, for example, manipulated by a software program.

[0055] When dark-field images are acquired while a patient is undergoing ablation, the patient's breathing may cause some motion in the acquired X-ray images. Therefore, in some embodiments of the invention, it may be advantageous to perform motion compensation on one or more of the dark-field X-ray images before performing a comparison. Such motion compensation may include alignment of a reference in the region of interest. The reference may be the tumor prior to the start of the treatment.

[0056] In some embodiments, the X-ray images are dark-field computed tomography (CT) images. CT combines a series of X-ray images acquired from different angles and uses computer processing to produce a cross-sectional image. Furthermore, in these embodiments, a grating-based approach can be employed, thereby introducing a three-grating interferometer into the X-ray beam path, making the signal measured at the X-ray detector sensitive to X-rays.

[0057] In one aspect, the invention also relates to a method for managing ablation procedures directed at a region of interest. The method includes initiating ablation procedures on the region of interest. The region of interest includes the tumor to be treated and some surrounding tissue. The tumor can be identified in various ways, such as by biplane radiography, 3D computed tomography, magnetic resonance imaging, etc. It can also begin with 2D-3D registration of X-ray images with 3D images (CT, MR).

[0058] Optionally, collimation is performed using a collimation unit to confine the X-ray beam to the region of interest. Suitable gratings, such as two absorber gratings and a phase grating between the absorber gratings, can be inserted.

[0059] Before initiating the intervention, a suitable set of angles can be selected to detect tumors in the surrounding lung, and a series of angles to be acquired during ablation can be implemented. Suitable angles are single or multiple angles that show the tumor in the dark-field image with good contrast and are well depicted relative to the surrounding lung tissue. When using multiple angles, they are selected in a way that well represents the 3D shape of the tumor in different projections (e.g., selecting sufficient angular distances between multiple angles).

[0060] The actual ablation treatment of the region of interest can then begin. A safety margin can be set for safe tumor destruction before intervention. For example, the ablation can be radiofrequency (RF) ablation or laser ablation. Alternatively, cryoablation can be applied, thereby using extreme cold to destroy the tumor or tissue.

[0061] By acquiring dark-field X-ray images during ablation, the tumor can be visualized in 2D projection. This allows for fine-tuning of the needle and bronchoscope position, which have been guided to the tumor via the bronchial system, during treatment. Therefore, dark-field imaging fluorescence fluoroscopy enables real-time guidance of the procedure. Figure 5 A transmission image, which always appears alongside a dark-field image, is shown. In this image, the needle is readily visible. Therefore, it can be segmented and blended into the dark-field image. The needle can also be shown directly in the dark-field image, as illustrated in the bottom portion of the figure.

[0062] Once a set of dark-field X-ray images has been collected, the evaluation methods described above can be applied to the available dark-field X-ray images. If appropriate, i.e., if a change over time is detected in the region of interest, a signal is generated to indicate that the change has effectively occurred. This signal is received in a control device, which then decides to terminate the ablation procedure. Additionally, an autoprojection-based estimate of the tumor margins destroyed during ablation can be determined.

[0063] In one aspect, the present invention discloses a software program executable on a programmable device containing instructions that, when run, perform the methods as previously described, and discloses a computer-readable medium on which the program is stored.

[0064] Although the invention has been illustrated and described in detail in the accompanying drawings and the foregoing description, such illustrations and descriptions are to be considered illustrative or exemplary, and not restrictive. The foregoing description details certain embodiments of the invention. However, it will be appreciated that the invention can be practiced in many ways, regardless of how detailed the foregoing is presented herein. The invention is not limited to the disclosed embodiments.

[0065] By studying the accompanying drawings, the disclosure, and the claims, those skilled in the art can understand and implement other variations of the disclosed embodiments in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the words "a" or "an" do not exclude a plurality. A single element or other unit may perform the function of several items recited in the claims. Although specific measures are recited in dissimilar dependent claims, this does not imply that combinations of these measures cannot be advantageously used. Computer programs may be stored / distributed on suitable media, such as optical storage media or solid-state media provided with or as part of other hardware, but computer programs may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems. Any reference numerals in the claims should not be construed as limiting the scope.

Claims

1. An apparatus for evaluating dark-field X-ray images acquired during ablation treatment, the ablation treatment targeting a region of interest present in the dark-field X-ray images, the apparatus comprising: - An image receiver for receiving a set of dark-field X-ray images acquired at a first time point and at least a second time point, including the region of interest. - A comparator for performing a comparison of dark-field X-ray images in the set at the first time point and at least the second time point. - A signal generator for generating a signal indicating the occurrence of a change if a change is detected in the region of interest in the dark-field X-ray images acquired at the first time point and at least the second time point during the comparison.

2. The apparatus for evaluating dark-field X-ray images according to claim 1, wherein, The comparator is configured to compare the dark-field X-ray images of the set using the determination of a difference image between the dark-field X-ray images in the set at the first time and at least the second time.

3. The apparatus for evaluating dark-field X-ray images according to claim 1 or 2, further comprising a segmenter for segmenting the region of interest in the set of dark-field X-ray images.

4. The apparatus for evaluating dark-field X-ray images according to claim 1 or 2, wherein, The change refers to a change in the size or shape of the object in the region of interest.

5. The apparatus for evaluating dark-field X-ray images according to claim 1 or 2, further comprising a motion compensator for performing motion compensation on one or more of the dark-field X-ray images prior to the comparison.

6. The apparatus for evaluating dark-field X-ray images according to claim 5, wherein, The motion compensation includes the alignment of objects within the region of interest.

7. The apparatus for evaluating dark-field X-ray images according to claim 1 or 2, wherein, The dark-field X-ray image is a dark-field computed tomography image.

8. The apparatus for evaluating dark-field X-ray images according to claim 1 or 2, wherein, The set of dark-field X-ray images was acquired using multiple gratings.

9. The apparatus for evaluating dark-field X-ray images according to claim 1 or 2, wherein, The ablation treatment is laser ablation, radiofrequency ablation, or cryoablation.

10. A system comprising an ablation device, a dark-field imaging device, and a device for evaluating dark-field images according to claim 1, wherein, The dark field image was acquired via the dark field imaging device during the ablation process performed using the ablation device.

11. The system according to claim 10 further includes a control device.

12. The system according to claim 10 or 11, wherein, The ablation device is configured to trigger the dark-field imaging device.

13. A method for evaluating a dark-field X-ray image acquired during an ablation procedure, the ablation procedure being directed toward a region of interest present in the dark-field X-ray image, the method comprising: - Receive a set of dark-field X-ray images acquired at a first time point and at least a second time point, including the region of interest. - Perform a comparison of the dark-field X-ray images in the set at the first time point and at least the second time point. - If a change is detected in the region of interest in the dark-field X-ray images acquired at the first time point and at least the second time point during the comparison, a signal indicating the occurrence of the change is generated.

14. A program executable on a programmable device containing instructions, which, when run, perform the method of claim 13.

15. A program executable on a programmable device comprising instructions, which, when run, control the features of the device according to any one of claims 1 to 6 and / or the features of the system according to claim 10 or 12.

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