Imaging with asymmetric contrast enhancement

Abstract

The present application relates to imaging with asymmetric contrast enhancement. In a method of imaging, an image (B) is generated by means of an imaging device (1), which image images a vascular structure (7) of an object (4) to be imaged and / or a device (8) arranged in the object (4). A local asymmetric contrast enhancement algorithm is applied to the image (B) by means of a computing unit (5) in order to generate a filtered image (F), which filtered image is displayed by means of a display device (9).

Description

Technical Field

[0001] The invention relates to an imaging method, wherein an image is generated by means of an imaging device, which images a vascular structure of an object to be imaged and / or a device arranged in the object. The invention also relates to a corresponding imaging device and a computer program product. Background Art

[0002] Modern imaging methods, in particular X-ray-based imaging methods, such as fluorescence-assisted X-ray-based methods, are sometimes used to support interventions. During an intervention, tools or other devices introduced or inserted into a subject to be examined can be imaged and tracked within the subject, for example, in the subject's vascular structure.

[0003] To achieve the most accurate possible trackability of the device relative to the vascular structure and, therefore, the most accurate possible guidance of the device within the subject, it is desirable to achieve the highest possible image quality. In particular, in the context of X-ray-based imaging methods, it can be difficult to clearly identify the device and distinguish it from other image components, such as tissue or bone structure, or the display of vascular structures. A similar situation applies to the discernibility of vascular structures relative to other tissues, etc. Summary of the Invention

[0004] Against this background, the object of the present invention is to provide an improved concept for imaging, in particular for X-ray-based imaging, by means of which the image quality of the generated images can be improved.

[0005] The above technical problem is solved by the corresponding subject matter of the present invention. Advantageous refinements and preferred embodiments are the subject matter of the following description.

[0006] This improved design is based on the concept of applying a local asymmetric contrast enhancement algorithm to an image that images a device arranged in an object to be imaged and / or a vascular structure of the object, and displaying the filtered image to a user.

[0007] According to this improved design, an imaging method is provided, wherein an image is generated by an imaging device, the image representing a vascular structure of a subject to be imaged and / or a device disposed in the subject, particularly a device disposed in the vascular structure. A local asymmetric contrast enhancement algorithm is applied to the image by a computing unit, particularly a computing unit of the imaging device, to generate a filtered image. The filtered image is displayed to a user of the imaging device by a display device, particularly a display device of the imaging device.

[0008] The imaging device may, for example, include an imaging modality and a computing unit, wherein in various embodiments, the computing unit may also be considered part of the imaging modality. In particular, the imaging modality may be configured as an X-ray imaging device, ie, include an X-ray source and an X-ray-sensitive sensor.

[0009] The imaging method can be designed as a subtraction angiography method, for example. The image then corresponds in particular to a superposition of a mask (also called a reference image) and an examination image.

[0010] For example, the image includes a plurality of image points or pixels, which are associated with corresponding detectors of a sensor's detector array. In the case of digital X-ray imaging, the sensor includes, for example, an array of photodiodes, in particular a two-dimensional array, which is capable of detecting X-ray quanta emitted by an X-ray source and at least partially passing through the object, and generating corresponding detector signals. Accordingly, a signal intensity can be assigned to each image point. For example, the signal intensity can be encoded as a grayscale value or other brightness value for visual display, or as an intensity value. Thus, each image point has a corresponding intensity value.

[0011] The local contrast enhancement algorithm can be understood as a local digital filter algorithm, for example. That is, the contrast enhancement algorithm processes the corresponding input information or input image pixel by pixel or region by region.

[0012] The local contrast enhancement algorithm is designed as an asymmetric contrast enhancement algorithm. In other words, the contrast enhancement algorithm acts asymmetrically with respect to the local intensity threshold. In other words, the contrast enhancement algorithm affects intensity values ​​above the local intensity threshold neither in the same way nor in the opposite way as intensity values ​​below the local intensity threshold.

[0013] By applying a contrast enhancement algorithm, the recognizability of devices and / or vascular structures in filtered images can be improved compared to unfiltered images, thereby ultimately improving image quality. The asymmetric design of the contrast enhancement algorithm particularly allows for a stronger emphasis on image regions that are darker relative to the local surroundings than on image regions that are brighter relative to the local surroundings, or vice versa. Consequently, relevant image regions, particularly those corresponding to devices and / or vascular structures, are emphasized particularly strongly, while less relevant image regions are not emphasized or are emphasized less strongly.

[0014] According to at least one embodiment of the imaging method, intensity values ​​below a local intensity threshold are reduced and / or intensity values ​​above the local intensity threshold are increased by applying a contrast enhancement algorithm, wherein the contrast enhancement algorithm acts asymmetrically with respect to the local intensity threshold.

[0015] For example, intensity values ​​below a local intensity threshold may be reduced, and intensity values ​​above the local intensity threshold may be neither reduced nor increased, or substantially neither reduced nor increased. Alternatively, intensity values ​​above the local intensity threshold may be increased by an amount where the increase in intensity values ​​above the local intensity threshold is less pronounced than the decrease in intensity values ​​below the local intensity threshold at the same distance from the intensity threshold; that is, the increase is less pronounced than the decrease. This results in an asymmetric effect of the contrast enhancement algorithm.

[0016] This has the effect, in particular, that a device consisting of a less radiopaque material stands out more strongly than the surroundings of the corresponding image point, in particular the tissue of the object.

[0017] In the case of devices that are less radiopaque than the surrounding tissue, the asymmetric effect of the contrast enhancement algorithm may be reversed.

[0018] According to at least one embodiment, for applying the contrast enhancement algorithm, a blurred input image is generated based on an input image related to the image by means of a computing unit. A contrast image is generated by subtracting the blurred input image from the input image, and a contrast-enhanced image is generated by superimposing the input image and the contrast image or an image related to the contrast image.

[0019] The contrast-enhanced image can then be regarded as the result of a contrast enhancement algorithm, for example.

[0020] The input image related to the image can be, for example, the image itself, or a deformation of a pre-processed image, or the result of another filtering algorithm.

[0021] For example, a low-pass filter, a local Gaussian filter, a box kernel filter or a multiscalar filter can be used to blur the image. This can also be referred to as soft focus. Because the blurred input image corresponds to a deformation of the input image with reduced contrast, subtracting the blurred input image from the input image produces a contrast image in which the parts of the input image that contribute to its contrast have been extracted. In other words, the parts of the input image that are not present in the blurred input image correspond to the contrast image.

[0022] For example, a contrast-enhanced image can be generated as the sum of an input image and a contrast image, or as the sum of an input image and an image related to the contrast image. This results in a partial increase in the contrast of the input image. Ultimately, this leads to better recognition of device and / or vascular structures in the filtered image.

[0023] According to at least one embodiment, the contrast image is modified locally asymmetrically with respect to a local intensity threshold value by means of a calculation unit, and the contrast-enhanced image is generated by superimposing the input image with the modified contrast image.

[0024] Characterizing the modification as asymmetric is to be understood in this context to mean, in particular, that the modification occurs neither symmetrically nor antisymmetrically with respect to the intensity threshold value.

[0025] For example, the local intensity threshold can be different for different image points of the input image or for a region of image points in the input image. In particular, the local intensity threshold can be determined by the calculation unit as the average intensity value of a predefined environment of the image points in the input image. To apply the contrast enhancement algorithm, for example, all image points in the input image are considered, and the corresponding intensity threshold is calculated as the corresponding average intensity value, and the asymmetric modification of the contrast image is based on this.

[0026] According to at least one embodiment, when the intensity value of an image point in the contrast image is less than an intensity threshold, the intensity value of the image point in the contrast image is reduced by the computing unit to modify the contrast image. Alternatively or additionally, when the intensity value of an image point in the contrast image is greater than the intensity threshold, the intensity value of the image point in the contrast image may be increased by the computing unit to modify the contrast image.

[0027] However, in both cases the reduction and / or increase is performed asymmetrically with respect to the intensity threshold value. In particular, the described reduction or increase of the intensity values ​​of the image points can be performed for all image points of the contrast image to generate a modified contrast image.

[0028] Increasing intensity values ​​correspond to brightening of the corresponding image point, while decreasing intensity values ​​correspond to darkening of the image point. By reducing the intensity of image points whose intensity values ​​are less than the intensity threshold, the tendency is to further darken the dark portions of the contrast image. In such embodiments, while darkening the dark portions, the brighter portions of the contrast image are not further brightened, or are brightened less strongly. In other words, in this way, the more radiopaque devices are more strongly emphasized in the modified contrast image, and accordingly, the more radiopaque devices are also emphasized more strongly in the contrast-enhanced image.

[0029] If, for example, a tool is used that is less radiopaque than the surrounding tissue, the modification of the contrast image may comprise brightening the lighter areas of the contrast image and not darkening or less intensely darkening the darker areas.

[0030] Overall, the asymmetric nature of the contrast enhancement algorithm makes it possible to enhance only particularly interesting components of the device image, ie, in particular the device and / or vessel structures.

[0031] According to at least one embodiment, a reference image and a test image are generated by means of an imaging device, wherein the test image shows the device arranged in the object, while the reference image does not show the device arranged in the object. An image is generated by means of a computing unit as a subtraction image of the test image and the reference image.

[0032] The image thus images the device and, if necessary, also the vascular structures. If no contrast agent is used for generating either the reference image or the test image, the device does not image the vascular structures or only images them in a greatly reduced manner.

[0033] According to at least one embodiment, an examination image is generated using a contrast agent, which can therefore also be referred to as a contrast agent image. A reference image is generated without using a contrast agent, which can also be referred to as a mask image, for example.

[0034] That is, in particular, when the device is arranged in the object, an examination image can be generated using a contrast agent, and before the device is arranged in the object, a reference image can be generated without using a contrast agent, that is, the reference image in particular does not image the device.

[0035] In various embodiments, the generation of the subtracted image may also include registration of the test image with the reference image.

[0036] That is, the subtraction image can be generated by, for example, subtracting the reference image and the inspection image from each other, or registering them and then subtracting them from each other. In this case, the subtraction can be performed pixel by pixel.

[0037] In this context, the reference image specifically displays the surroundings of the device, such as the vessel structure and its surroundings. The examination image also displays the vessel structure and its surroundings, but the application of a contrast agent increases the image contrast between the region corresponding to the vessel structure and other regions compared to the reference image. In other words, by generating a subtraction image, portions of the examination image not highlighted by the application of the contrast agent are removed or at least attenuated by subtracting the reference image. The generated subtraction image thus displays the vessel structure particularly clearly, while other surrounding structures and / or tissue components are not displayed or are only significantly reduced in their visibility. This improves the recognizability of the vessel structure in the image, and ultimately in the filtered image.

[0038] The examination image and the reference image can in particular correspond to corresponding x-ray recordings.

[0039] In particular, the examination image and the reference image are recorded with the same imaging parameters of the imaging modality, in particular the X-ray source and the sensor. This makes it possible to reduce or mitigate artifacts in the subtracted image.

[0040] According to at least one embodiment, a reference image is generated by the imaging device without the use of a contrast agent, and a test image is generated with the use of a contrast agent, wherein the test image shows the vascular structure. An image is generated by the computing unit as a subtraction image of the test image and the reference image.

[0041] For example, the device may not be imaged in either the reference image or the inspection image.

[0042] That is, in the corresponding embodiment, three variations of subtraction images are provided. In all three variations, the reference image does not image the device. Also, in all three variations, the reference image is generated without using a contrast agent.

[0043] In a first variation, the examination image is generated without the use of a contrast agent, and the examination image images the device. The subtraction image then essentially shows only the device. This can be advantageous, for example, for examining the status of the device. In a second variation, the examination image is generated with a contrast agent, and the examination image images the device. The subtraction image then shows not only the device but also the vascular structure. This can be advantageous, for example, for determining the position of the device relative to the vascular structure. In a third variation, the examination image is generated with a contrast agent, and the examination image does not image the device. The subtraction image then essentially shows only the vascular structure.

[0044] According to at least one embodiment, a plurality of further images are generated by means of the imaging device, wherein each of these further images images the vessel structure and / or a device arranged in the subject. The image and each of these further images are generated using a different recording angle.

[0045] In this case, in corresponding embodiments, the inspection image and the reference image are generated, if necessary, at the same recording angle in order to generate the image.

[0046] In other words, the recording angle is gradually varied to generate the image and the further image accordingly. The recording angle can correspond to the angle of the recording direction in three-dimensional space relative to a predefined reference axis. The recording direction can, for example, be parallel to a straight line connecting the X-ray source to the detector array of the sensor.

[0047] The variability of the recording angle can be achieved, for example, by using a C-arm X-ray imaging modality.

[0048] According to at least one embodiment, a three-dimensional reconstruction is generated by means of the computing unit based on the image and on a plurality of further images. The reconstruction is displayed to a user by means of a display device and / or by means of a further display device of the imaging device.

[0049] According to at least one embodiment, a contrast enhancement algorithm is applied to each of these further images by means of a computing unit to generate corresponding further filtered images. These further filtered images are displayed to a user by means of a display device.

[0050] In particular, the filtered image and the further filtered image are displayed separately, ie, these images are not processed with respect to one another in the sense of a three-dimensional reconstruction.

[0051] In addition to the three-dimensional reconstruction, the filtered image or further filtered images also offer the user valuable possibilities for orientation during an intervention or examination.

[0052] Since the reconstruction requires the original image and the original further images, i.e., in particular, the reconstruction is produced independently of the filtered image and independently of the further filtered images, the direct display of the filtered image or the further filtered images (if necessary additionally) provides significant added value for the user.

[0053] Therefore, in various embodiments, the reconstruction is displayed in addition, for example simultaneously with the filtered image and / or the further filtered image, for example side by side.

[0054] As a result, the user can be particularly effectively and efficiently informed of different types of information, including the reconstruction on the one hand and the filtered image or further filtered images on the other hand.

[0055] According to at least one embodiment, the filtered image and the further filtered image are displayed sequentially, in particular by means of a display device, so that at any point in time, exactly one of the filtered image or the further filtered image is displayed.

[0056] Thus, for example, a temporally dynamic display of filtered images and further filtered images can be achieved according to the sequence of the set recording angles. The display frame rate can be predefined by the user, for example. This means that effective 3D display can be achieved without performing additional 3D reconstruction.

[0057] According to at least one embodiment, a corresponding additional reference image and a corresponding additional examination image are created for each additional image of the plurality of additional images. The additional reference image accordingly does not show the device arranged in the object. The corresponding additional image is generated by means of a computing unit as a subtraction image of the corresponding examination image and the corresponding reference image.

[0058] Depending on the embodiment, as described with respect to the examination images, additional examination images may be generated with or without the use of a contrast agent. Depending on the embodiment, as described with respect to the examination images, additional examination images may or may not image the device.

[0059] In this case, in particular, a corresponding examination image for generating one of the further images and a further reference image for generating the same further image are generated using the same recording angle.

[0060] For example, the reference image and the further reference image can each be generated first without using a contrast agent and without imaging the device. Subsequently, the examination image and the further examination image can each be generated with the use of a contrast agent and / or with the device positioned in the subject. In both operations, the angles are varied or recorded in the same manner to obtain corresponding matching pairs for subtraction.

[0061] According to this improved design, an imaging device comprising an imaging modality is also given. The imaging device, in particular the imaging modality, further comprises a computing unit. The imaging modality is designed to generate at least one sensor data set which is related to a vascular structure of an object to be imaged and / or a device arranged in the object, in particular in the vascular structure. The computing unit is designed to generate an image which images the vascular structure and / or the device on the basis of the at least one sensor data set. The computing unit is designed to generate a filtered image by applying a local asymmetric contrast enhancement algorithm to the image. The imaging device further has a display device which is coupled to the computing unit in order to display the filtered image to a user of the imaging device.

[0062] The display device in particular comprises a display or a monitor for displaying the filtered image, wherein the display device can be controlled accordingly by the computing unit for this purpose.

[0063] In particular, the at least one sensor data set can comprise an examination image or the computing unit can be designed to generate an examination image on the basis of the at least one sensor data set. For example, the at least one sensor data set can also comprise a reference image or the computing unit can be designed to generate a reference image on the basis of the at least one sensor data set.

[0064] The imaging modality in particular is designed as an X-ray imaging modality, for example as a digital X-ray imaging device, in particular as a C-arm X-ray imaging modality. Thus, the imaging modality in particular comprises an X-ray source and a sensor unit. The sensor unit may, for example, comprise an optical detector, in particular a detector array of photodiodes, in particular a two-dimensional detector array, which can generate the at least one sensor data set.

[0065] Further embodiments of the imaging device according to this improved design follow the different design approaches of the imaging method according to this improved design and vice versa. In particular, the imaging device according to this improved design can be designed to carry out the method according to this improved design or it carries out such an imaging method.

[0066] According to this improved design, a computer program product having instructions is also given. When the instructions are executed by the imaging device according to this improved design, in particular by the computing unit of the imaging device, the instructions cause the imaging device to carry out the imaging method according to this improved design.

[0067] Here, the computer program product can be designed as a computer program having instructions. The computer program product can also be designed as a computer-readable storage medium which stores the computer program having instructions. BRIEF DESCRIPTION OF DRAWINGS

[0068] The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown individually in the figures, can be used not only in the combination respectively indicated, but also in other combinations without departing from the scope of the present invention. The following embodiments and feature combinations may also be considered disclosed, which do not have all the features of the originally drafted independent claims and / or exceed or differ from the feature combinations stated in the cited claims.

[0069] in:

[0070] Figure 1 A schematic diagram showing an exemplary embodiment of an imaging device according to an improved design;

[0071] Figure 2 A schematic flow chart showing an exemplary embodiment of an imaging method according to an improved design;

[0072] Figure 3 shows a schematic diagram of processing intensity values ​​according to another exemplary embodiment of the imaging method according to the improved design;

[0073] Figure 4 shows a schematic diagram of processing intensity values ​​according to another exemplary embodiment of the imaging method according to the improved design;

[0074] Figure 5 shows an image and a filtered image according to another exemplary embodiment of the imaging method according to the improved design; and

[0075] Figure 6 Schematic diagram showing the impact of an asymmetric local contrast enhancement algorithm on human visual perception. DETAILED DESCRIPTION

[0076] Figure 1 An exemplary embodiment of an imaging device 1 according to an improved design is schematically shown, which is designed as an X-ray imaging device, for example. Figure 1 The example in FIG shows the structure of an X-ray imaging device based on the principle of a C-arm arrangement. The C-arm arrangement includes a rotatable and movable C-arm 6 that can be rotated and moved accordingly to image an object 4 from different directions, i.e., at different recording angles. However, the imaging device 1 according to the improved design can also be constructed according to other structures. In particular, the improved design is not limited to X-ray-based imaging methods in principle.

[0077] therefore, Figure 1The imaging device 1 includes, for example, an X-ray source 2, which is designed to generate X-ray beams and emit them in the direction of an object 4. A sensor 3 of the imaging device 1 is arranged on the side of the object 4 opposite the X-ray source 2 and includes, for example, a detector array of photodiodes in order to be able to detect X-ray quanta that have passed through the object 4. The sensor 3 can then transmit corresponding detector signals, for example, to a computing unit 5 of the imaging device 1 for further processing.

[0078] The imaging device 1 can be designed in particular for example to perform a rotational angiography method based on the principle of subtraction angiography. In this case, the computing unit 5 can generate a plurality of two-dimensional projections recorded from different angles and calculate a three-dimensional reconstruction therefrom.

[0079] Reference is now made to different design approaches for the imaging method according to the improved design, in particular to Figures 2 to 6 The mode of operation of the imaging device 1 is explained in more detail.

[0080] Figure 2 An exemplary embodiment of an imaging method according to an improved design is schematically shown, which is designed as a rotational angiography method based on the principle of subtraction angiography.

[0081] exist Figure 2 In the upper region of , a time bar is shown, which schematically illustrates two recording phases P1, P2 as a function of time t. The recording phases P1, P2 do not necessarily follow each other directly.

[0082] For example, in a first stage P1, a plurality of reference images RB, RB′, RB″ of a region of the object 4 are generated. The reference images respectively show the vessel structure 7 (see Figure 5 ) and the corresponding tissue environment of the vascular structure 7. The reference images RB, RB', RB" can also be called masks. Here, when applying the above-mentioned function of the C-arm 6, different reference images RB, RB', RB" are generated at different recording angles.

[0083] In a second phase P2 following the first phase P1, a corresponding examination image UB, UB', UB" is generated for each reference image RB, RB', RB" at the same recording angle. The examination images UB, UB', UB" show the same area of ​​the object 4 as the reference images RB, RB', RB". Although the reference images RB, RB', RB" are not generated using a contrast agent, the examination images UB, UB', UB" can be generated using a contrast agent, i.e., as contrast agent images.

[0084] For example, a contrast agent is introduced into the vascular structure 7 during the second phase P2 or between the first phase P1 and the second phase P2, so that the examination images UB, UB′, UB″ each show the vascular structure 7 in a highlighted manner. Depending on the contrast agent used and the processing of the generated images, the vascular structure 7 can appear brighter or darker than the surrounding tissue. However, the administration of the contrast agent itself should not be considered as part of the method according to the improved design.

[0085] Furthermore, unlike the reference images RB, RB', RB", the inspection images UB, UB', UB" are displayed by the display device 8 (see Figure 5 ), which, after generating the reference images RB, RB′, RB″, is introduced into the object 4, in particular into the vascular structure 7. However, in this case, the introduction of the device 8 into the object 4 or the movement of the device 8 in the object 4 should not be considered as part of the method according to the improved design. Therefore, the examination images UB, UB′, UB″ show both the vascular structure 7 and, if necessary, the surroundings as well as the device 8.

[0086] The device 8 is typically an object with a higher X-ray density than the surrounding tissue. Depending on the processing of the output image, the device 8 can therefore appear darker than the surrounding tissue. The device 8 can, in particular, consist of a metal, such as platinum, stainless steel, or gold. The device 8 can fulfill different functions. For example, the device 8 can be part of a vascular catheter, a guidewire (also called a guidewire) or a part thereof, part of a vascular prosthesis or stent, a marker, etc. However, the device 8 can also consist of a material that is less X-ray opaque than the surrounding environment, such as CO2, in particular dry ice.

[0087] The calculation unit 5 combines each of the reference images RB, RB', RB" with the respectively related examination images UB, UB', UB" produced at the same recording angle to obtain the corresponding image RB, RB', RB", which is also called a subtraction image or a superposition image. For example, the combination of the reference image RB, RB', RB" with the related examination image UB, UB', UB" can include a corresponding alignment. In addition, the combination includes subtracting the corresponding reference image RB, RB', RB" from the related examination image UB, UB', UB" or the corresponding registered image or vice versa. Additionally, the combination can include further processing of the subtraction image. In other words, the image B can be expressed as B=P(UB-RB), where P represents an arbitrary processing function.

[0088] Contrast agent selection and processing of the images RB, RB', RB", UB, UB', UB" are usually performed such that the images B, B', B" show the device 8 darker than the tissue surroundings and in particular darker than the vascular structures 7 (see Figure 5 ). However, this is not necessarily the case.

[0089] The computing unit 5 applies a local asymmetric contrast enhancement algorithm to each of the images B, B', B" to obtain a respective filtered image F, F', F" as a result.

[0090] Each image B, B', B" is here provided by a plurality of pixels, which respectively correspond to intensity values. The spatial position of each pixel can be given by a respective two-dimensional spatial coordinate. In Figures 3 to 6 The functional way of the asymmetric contrast enhancement algorithm is exemplarily shown in

[0091] Figure 3 The generation of a contrast image based on an input image is shown. The input image can correspond to one of the images B, B', B" or an image related thereto. Figure 3 An input signal E is shown, which corresponds to the intensity values in a region of the input image as a schematic spatial variation. The input signal E has a more or less steep step, which corresponds to a transition from a material which is less X-ray opaque to a material which is more X-ray opaque, for example a transition from tissue to the device 8. The computing unit 5 generates a spatially blurred signal E' from the input signal E or the entire input image, for example by a convolution with a Gaussian filter or a box kernel filter, which can also be called a soft focus signal. Alternatively, for example a multi-scalar filter method can also be applied. Here, the size of the filter kernel, i.e. the size of the final local environment, can be parameterized by the user, for example. Thus, an optimized result can be achieved for different dimensions of the relevant objects, i.e. the device 8 and / or the vessel structure 7.

[0092] Then, the blurred input signal E' is subtracted from the input signal E, for example by the computing unit 5, to generate a contrast signal KS. Alternatively, the process can be understood as subtracting the blurred input image from the input image to generate a contrast image.

[0093] Now the contrast signal KS or the contrast image is modified asymmetrically by means of the computing unit, as Figure 4 is shown. As a result, a modified contrast signal KS' or a respective modified contrast image is obtained.

[0094] Since in X-ray images, materials which are more X-ray opaque, for example guide wires, stents, platinum markers, iodine, etc., are often used as devices, these materials are contained in the input image with a negative or dark contrast compared to the surrounding environment. Therefore, the contrast signal KS can be processed by the modification such that positive values, i.e. bright values, in the contrast signal KS are attenuated, while negative values, i.e. dark values, in the contrast signal KS are amplified. This can be achieved, for example, by a parameterizable look-up table or other pre-given function, as for example depicted on the right-hand side of Figure 4 .

[0095] The modified contrast signal KS' is then superimposed on, for example, the input image E. Accordingly, in the input image, by applying the asymmetric contrast enhancement algorithm, dark parts are locally enhanced, i.e., their brightness is further reduced, while bright parts are not locally enhanced or are enhanced less than dark parts.

[0096] In an alternative embodiment, brighter values ​​in the contrast signal KS can also be amplified, while darker values ​​can be suppressed. This can be advantageous for better separation of less dense materials, such as CO 2 , from the surroundings.

[0097] exist Figure 5 The left side of FIG shows an image B by way of example, and the right side shows the corresponding filtered image F'. In contrast, the device 8 can be seen more clearly in the superimposed image RMB using the local asymmetric contrast enhancement algorithm.

[0098] Optionally, if, in various embodiments, the modified contrast signal KS' is weighted with a measure of the local gradient strength, the sharper highlighting of the device 8 can be further enhanced. For example, the local gradient strength can be calculated using a Sobel operator.

[0099] In particular, compared with traditional local or global contrast enhancement algorithms, the special effect of the asymmetric local contrast enhancement algorithm is schematically shown in Figure 1 Here again the input signal E and the modified comparison signal KS' are shown, as in Figure 3 and Figure 4 As described. Human perception of adjacent image areas of different brightness is deceived by the asymmetrical exaggeration at the border (which is indicated, for example, in the contrast signal KS') according to a variant of the so-called Cornsweet effect, so that the average brightness difference to the left and right of the border appears greater than it actually is. In other words, the darker areas appear to be darker more, i.e. not only directly at the border. The resulting perceptual change in brightness KS" is also Figure 6 This is shown below. Through the improved design, this effect is used to more strongly enhance the relevant areas in the filtered images F, F', F".

[0100] The filtered images F, F', F'' can then be displayed on 09 in sequence, in particular in the order of the recording angles, at a defined, possibly variable frame rate. This allows the effect of a three-dimensional display, in particular of the device 8 in the object 4.

[0101] In addition to the filtered images F, F', F", the calculation unit 5 can calculate a three-dimensional reconstruction R from the unfiltered images B, B', B". The reconstruction R can advantageously be displayed on the display device 9 or another display device (not shown) simultaneously with the temporal dynamic display of the filtered images F, F', F'". The user can then preferably obtain at a glance the two-dimensional filtered images F, F', F" and the three-dimensional reconstruction R. It has been shown that in this way the user can record the information provided by the filtered images F, F', F" and the reconstruction R extremely effectively and efficiently.

[0102] The application of the contrast enhancement algorithm to the subtracted image is described in particular with respect to the figures. However, the contrast enhancement algorithm can also be applied directly to the inspection image in a similar manner to save computing time and inspection time.

[0103] Furthermore, the contrast enhancement algorithm can be applied only to a portion of the subtraction image or the inspection image. To this end, the region of interest can be identified manually or, for example, with the aid of a trained model, and only this region can be filtered accordingly. This can thus reduce the computational effort.

Claims

1. An imaging method, comprising: An image (B) is generated by means of an imaging device (1), said image imaging a vascular structure (7) of an object (4) to be imaged and / or a device (8) arranged in the object (4); Applying a local asymmetric contrast enhancement algorithm to the image (B) by means of a calculation unit (5) to generate a filtered image (F), wherein applying the local asymmetric contrast enhancement algorithm comprises: generating a blurred input image based on an input image related to the image (B); generating a contrast image by subtracting the blurred input image from the input image, wherein the contrast image is modified locally asymmetrically with respect to a local intensity threshold, wherein, for modifying the contrast image, when the intensity value of the image point of the contrast image is less than the intensity threshold, the intensity value of the image point of the contrast image is reduced by a reduction degree to modify the contrast image; and / or when the intensity value of the image point of the contrast image is greater than the intensity threshold, the intensity value of the image point of the contrast image is not increased or is increased by an increase degree that is smaller than the reduction degree; generating a contrast-enhanced image by superimposing the input image and the modified contrast image; and The filtered image (F) is displayed to a user of the imaging device (1) by means of a display device (9).

2. The imaging method according to claim 1, It is characterized in that - generating a reference image (RB) and an examination image (UB) by means of the imaging device (1), wherein the reference image (RB) does not show the device (8) arranged in the object (4), while the examination image (UB) shows the device (8) arranged in the object (4); and The image (B) is generated by means of the computing unit (5) as a subtraction image of the examination image (UB) and the reference image (RB).

3. The imaging method according to claim 2, It is characterized in that The examination image (UB) is generated using a contrast agent, and the reference image (RB) is generated without using a contrast agent.

4. The imaging method according to claim 1, It is characterized in that - generating a reference image (RB) without the use of a contrast agent and generating an examination image (UB) with the use of a contrast agent by means of the imaging device (1), wherein the examination image (UB) shows the vessel structure (7); and The image (B) is generated by means of the computing unit (5) as a subtraction image of the examination image (UB) and the reference image (RB).

5. The imaging method according to claim 1, It is characterized in that - generating a plurality of further images (B', B") by means of the imaging device (1), wherein each of the further images (B', B") images a vascular structure (7) and / or a device (8) arranged in the object (4); - generating each of said image (B) and said further images (B', B") using a different recording angle, respectively; - applying the contrast enhancement algorithm to each of the further images (B', B") by means of the calculation unit (5) to generate a corresponding further filtered image (F', F"); and - displaying the further filtered images (F', F") to a user by means of a display device (9).

6. The method according to claim 5, It is characterized by: The filtered image (F) and the further filtered images (F', F") are displayed sequentially so that at any point in time exactly one of the filtered image (F) or the further filtered images (F', F") is displayed.

7. The method according to claim 5, It is characterized by: A three-dimensional reconstruction (R) is generated based on the image (B) and the plurality of further images (B', B") by means of the computing unit (5), and the reconstruction (R) is displayed by means of a display device (9) and / or by means of a further display device.

8. The method according to claim 7, It is characterized by: The reconstruction (R) is produced independently of the filtered image (F) and independently of the further filtered images (F′, F″).

9. The imaging method according to claim 1, It is characterized by: The local intensity threshold is determined by means of the calculation unit (5) as an average intensity value of a predefined environment of a pixel in the input image.

10. The imaging method according to any one of claims 1 to 8, It is characterized by: - reducing intensity values ​​below a local intensity threshold and / or increasing intensity values ​​above a local intensity threshold by applying said contrast enhancement algorithm; - wherein the contrast enhancement algorithm acts asymmetrically with respect to a local intensity threshold.

11. The imaging method according to claim 10, It is characterized by: The contrast enhancement algorithm reduces intensity values ​​below a local intensity threshold by a reduction degree and does not increase, or increases by a smaller degree than the reduction degree, intensity values ​​above the local intensity threshold.

12. An imaging device (1), comprising: a sensor configured to generate at least one sensor data set relating to a vascular structure (7) of an object (4) to be imaged and / or a device (8) arranged in the object (4); as well as a computing unit (5) configured to generate an image (B) based on the at least one sensor data set, the image imaging the vessel structure (7) and / or the device (8) arranged in the object (4); - the computing unit (5) is further configured to generate a filtered image (F) by applying a local asymmetric contrast enhancement algorithm to the image (B), wherein applying the local asymmetric contrast enhancement algorithm comprises: generating a blurred input image based on an input image related to the image (B); A contrast image is generated by subtracting the blurred input image from the input image, wherein the contrast image is modified locally asymmetrically with respect to a local intensity threshold, wherein, for modifying the contrast image, when the intensity value of the image point of the contrast image is less than the intensity threshold, the intensity value of the image point of the contrast image is reduced by a reduction degree to modify the contrast image; and / or when the intensity value of the image point of the contrast image is greater than the intensity threshold, the intensity value of the image point of the contrast image is not increased or is increased by an increase degree that is smaller than the reduction degree; and generating a contrast-enhanced image by superimposing the input image and the modified contrast image; and The imaging device (1) has a display device (9) coupled to the calculation unit (5) in order to display the filtered image (F) to a user of the imaging device (1).

13. The imaging device according to claim 12, It is characterized by: - generating a reference image (RB) and an examination image (UB) by means of the imaging device (1), wherein the reference image (RB) does not show the device (8) arranged in the object (4), while the examination image (UB) shows the device (8) arranged in the object (4); and The image (B) is generated by means of the computing unit (5) as a subtraction image of the examination image (UB) and the reference image (RB).

14. The imaging device according to claim 13, It is characterized by: The examination image (UB) is generated using a contrast agent, and the reference image (RB) is generated without using a contrast agent.

15. The imaging device according to claim 12, It is characterized by: - generating a reference image (RB) without the use of a contrast agent and generating an examination image (UB) with the use of a contrast agent by means of the imaging device (1), wherein the examination image (UB) shows the vessel structure (7); and The image (B) is generated by means of the computing unit (5) as a subtraction image of the examination image (UB) and the reference image (RB).

16. A computer program product having instructions which, when executed by the imaging device (1) according to claim 12, cause the imaging device (1) to perform the imaging method according to any one of claims 1 to 11.

Images