Angiographic examination procedure of a vascular system in a body region of interest to a patient

Abstract

An angiographic examination procedure for generating at least one 2-D projection image of a vascular system (20, 23) in a body region of interest of a patient (6) with an angiography system (1 to 4) characterized by the following steps: S1 Acquisition of a volume dataset of the body region of interest including the vascular system (23), S2 Reconstruction of a 3-D volume (22) from the volume dataset with the vascular system (23), S3 forward projection (24) to generate a virtual projection (25) with the vessels (20), S4 Derivation of a binary vascular mask (26) from the virtual projection (25), S5 Acquisition of at least one recent 2-D image (27), S6 Combination of the binary vascular mask (25) with at least one current 2D image (27) to form a current mask (28), S7 Threshold calculation (29) of the current mask (28) to form a current binary mask (30), S8 Backprojection (31) of the current binary mask (30) into the 3-D volume (22) to form a mask volume (32), S9 Threshold segmentation (33) of the mask volume (32) to create a final virtual vessel volume (34) and S10 Subtraction of a projection of the vessel volume (34) from the current 2-D images (27) to generate a selective non-overlapping representation of the body region of interest with selectable parameters.

Description

[0001] The invention relates to an angiographic examination method for generating at least one 2D projection image of a vascular system in a body region of interest of a patient using an angiography system. This angiographic examination method enables a non-overlapping and multiparametric representation of, for example, the brain parenchyma. Such an angiography system is known, for example, from US 7,500,784 B2, which is based on the Fig. 1 is explained below.

[0002] For color-coded representation of the bolus arrival time (Time to Peak - TTP), 2D DSA series can be used, as described, for example, in "syngo iFlow / Dynamic Flow Evaluation / Answers for life" by Siemens AG, Medical Solutions, Angiography, Fluoroscopic and Radiography Systems, Order No. A91AX-20902-11C1-7600. Although the vascular tree can be visualized very well, it is sometimes important, for example in cases of stroke or vasospasm, to visualize only the perfusion or blood flow in the brain parenchyma. This is usually not possible because the large vessels overlay these areas and cannot be separated from them. It is not always desirable to perform a perfusion CT scan or a perfusion image using rotational angiography.

[0003] If segmentation of the parenchyma and vessels exists, a multi-component graphic overlay on the current DSA series in 2-D or 3-D can still be used as a navigation aid.

[0004] The Fig. Figure 1 shows an example of a monoplane X-ray system with a C-arm 2 held by a stand 1 in the form of a six-axis industrial or articulated robot, at the ends of which an X-ray source, for example an X-ray emitter 3 with X-ray tube and collimator, and an X-ray image detector 4 as an image acquisition unit are attached.

[0005] By means of the articulated robot known, for example, from US 7,500,784 B2, which preferably has six axes of rotation and thus six degrees of freedom, the C-arm 2 can be adjusted spatially as desired, for example, by rotating it about a center of rotation between the X-ray source 3 and the X-ray image detector 4. The angiographic X-ray system 1 to 4 according to the invention is rotatable, in particular, about centers of rotation and axes of rotation in the C-arm plane of the X-ray image detector 4, preferably about the center of the X-ray image detector 4 and axes of rotation intersecting the center of the X-ray image detector 4.

[0006] The well-known articulated robot has a base frame, which is, for example, fixed to a floor. A carousel is attached to this frame and can rotate around a first axis. A robot arm is mounted on the carousel and can pivot around a second axis. A robot arm is attached to the arm and can rotate around a third axis. A robot hand is mounted at the end of the robot arm and can rotate around a fourth axis. The robot hand has a mounting element for the C-arm 2, which can pivot around a fifth axis and rotate around a sixth axis of rotation perpendicular to it.

[0007] The implementation of the X-ray diagnostic system does not depend on an industrial robot. Conventional C-arm devices can also be used.

[0008] The X-ray image detector 4 can be a rectangular or square, flat semiconductor detector, preferably made of amorphous silicon (a-Si). However, integrating and possibly counting CMOS detectors can also be used.

[0009] In the beam path of the X-ray tube 3, a patient 6 is positioned on a tabletop 5 of a patient positioning table. A control unit 7 with an imaging system 8 is connected to the X-ray diagnostic device. This system receives and processes the image signals from the X-ray image detector 4 (operating elements are not shown). The X-ray images can then be viewed on displays of a monitor 10 suspended by a ceiling-mounted, longitudinally movable, swiveling, rotating, and height-adjustable support system 9. The control unit 7 also includes a device 11 in which the procedure described below can be carried out.

[0010] Instead of the in Fig. The X-ray system shown in Figure 1, for example, with the stand 1 in the form of the six-axis industrial or articulated robot, can be used, as in Figure 1. Fig. 2 In simplified terms, the angiographic X-ray system also has a normal ceiling- or floor-mounted bracket for the C-arm 2.

[0011] Instead of the C-arm 2 shown, for example, the angiographic X-ray system can also have separate ceiling- and / or floor-mounted brackets for the X-ray tube 3 and the X-ray image detector 4, which are, for example, electronically rigidly coupled.

[0012] The X-ray source 3 emits a beam 12 from a focus point of its X-ray source, which strikes the X-ray image detector 4. If 3D datasets are to be created using the so-called DynaCT method, a rotational angiography technique, the rotatably mounted C-arm 2 with X-ray source 3 and X-ray image detector 4 is rotated such that, as the Fig. Figure 2, shown schematically in a top view of the axis of rotation, illustrates that the X-ray source 3, represented here by its beam focus, and the X-ray image detector 4 move around an object 13 to be examined, located in the beam path of the X-ray source 3, on an orbit 14. The orbit 14 can be traversed completely or partially to create a 3D dataset or volume dataset.

[0013] The C-arm 2 with X-ray source 3 and X-ray image detector 4 moves, according to the DynaCT method, preferably through an angular range of at least 180°, for example 180° plus fan angle, and rapidly acquires projection images from different projections. Reconstruction can only be performed from a subset of these acquired data.

[0014] The object to be examined, 13, could be, for example, an animal or human body, but also a phantom body.

[0015] The X-ray source 3 and the X-ray image detector 4 each move around the object 5 in such a way that the X-ray source 3 and the X-ray image detector 4 are located on opposite sides of the object 13.

[0016] In normal radiography or fluoroscopy using such an X-ray diagnostic device, the medical 2-D data of the X-ray image detector 4 are temporarily stored in the image system 8 and then displayed on the monitor 9.

[0017] A method for vascular navigation is known from German patent application DE 103 59 431 A1. A series of consecutive images is taken of an area of ​​interest to track the distribution of a contrast agent in blood vessels over time. A mask with maximum contrast is then determined from these images. Another image is taken during a surgical procedure and depicts, for example, an instrument within a vessel. Areas of no interest can be masked out by subtracting the mask.

[0018] German patent application DE 10 2005 062 445 A1 discloses a method for generating an X-ray image. Two X-ray images are taken and combined to form a composite image. A maximum contrast image is also created if necessary.

[0019] Furthermore, document US 2008 / 0247503 A1 discloses a method for measuring blood volume. This involves subtracting 3D volumes from one another. A 2D mask is optionally used to mask out blood vessels.

[0020] The invention is based on the objective of developing an angiographic examination method of the type mentioned above in such a way that a superimposition-free representation of the brain parenchyma can be achieved in 2-D-DSA series.

[0021] The problem is solved according to the invention for an angiography system of the type mentioned above by the features specified in claim 1. Advantageous embodiments are specified in the dependent claims.

[0022] The problem is solved for an angiographic examination method according to the invention by the following steps: S1 Acquisition of a volume dataset of the body region of interest including the vascular system, S2 Reconstruction of a 3-D volume from the volume dataset with the vascular system, S3 forward projection to generate a virtual projection with the vessels, S4 Derivation of a binary vessel mask from the virtual projection, S5 acquisition of at least one current 2D image, S6 Combination of the binary vascular mask with at least one 2D image to create an up-to-date mask, S7 Threshold calculation of the current mask to form a current binary mask, S8 Backprojection of the current binary mask into the 3-D volume to form a mask volume, S9 threshold segmentation of the mask volume to create a final virtual vessel volume and S10 Subtraction of a projection of the vessel volume from the current 2-D images to generate a selective, non-overlapping representation of the body region of interest with selectable parameters.

[0023] This allows users to choose whether to view only brain parenchyma, only blood vessels, or a combination of both. Furthermore, it is possible to combine different parameters in a single visualization.

[0024] Advantageously, the acquisition of a volume data set according to procedure step S1 can be carried out using rotational angiography.

[0025] Further processing is facilitated if process step S2 includes segmentation of the vascular system.

[0026] It has proven advantageous if the virtual projection according to procedure step S3 is a virtual 2-D-DSA.

[0027] According to the invention, the current 2D images can be derived from a current measured 2D DSA series.

[0028] Advantageously, the 2D images currently acquired according to process step S5 can be maximum pacification images of a 2D DSA series.

[0029] According to the invention, an adjustment of intensities and optimization can take place before process step S10.

[0030] The visibility of individual image components can be increased if, for selective, non-overlapping display of the body region of interest, the transmission levels of the components to be superimposed are adjustable, in particular separately adjustable.

[0031] It has proven advantageous if adjusting means are provided for the separate adjustment of the transmission levels and are designed in such a way that transmission bars characterizing the setting can be displayed.

[0032] According to the invention, the adjusting means can be designed such that the transmission levels can be adjusted by moving the sliders with the mouse.

[0033] The visibility of the setting can be increased if a digital percentage display is assigned to the transmission bars to show the proportions to be superimposed.

[0034] The invention is explained in more detail below with reference to exemplary embodiments shown in the drawing. The drawing shows: Fig. 1 a known C-arm angiography system with an industrial robot as a support device, Fig. 2 a schematic representation of the geometric relationships in rotational angiography with the C-arm angiography system according to Fig. 1, Fig. 3 a mask picture, Fig. 4 a fill image as well as Fig. 5. A DSA image to illustrate the normal DSA principle, Fig. 6 a projection to form a virtual binary mask, Fig. 7 a description of the process steps for forming a volume adapted to and representing the state of the current 2-D DSA series, Fig. 8 a brain parenchyma representation, Fig. 9 a vascular image and Fig. 10 a composition image according to the invention with a graphic overlay with fading indicator.

[0035] Based on the Fig. The DSA principle is now explained in sections 3 to 5. First, a mask image 15 of a head is acquired, in which the entire anatomy 16, such as skull bones, is included. Subsequently, after an injection of contrast medium, a filling image 17 ( Fig. 4) generated, in which, besides an anatomical background 18, the anatomy 16 according to Fig. 3, now also the parenchyma 19 and the vessels 20 are visible. If these two images are now subtracted from each other, one obtains a Fig. 5 DSA image 21 shown, which shows only the areas filled with contrast medium, the parenchyma 19 and the vessels 20.

[0036] A reconstructed 3D volume 22 with a vascular tree or vascular system 23, for example from computed tomography angiography (CTA) or rotational angiography, is converted by forward projection 24 into a virtual vascular projection 25 (2D-DSA - digital subtraction angiography), in which the vascular tree with the vessels 20 may already be segmented. From this, a virtual binary vascular mask 26 is determined.

[0037] This binary vascular mask 26, which represents the entire vascular tree, is combined with images from the current measured 2D-DSA series—ideally the maximum ocpacification image 27, if an iFlow combination is desired later. The maximum ocpacification image 27 is described in the aforementioned publication. It shows the maximum opacity due to a contrast agent for each pixel during the entire filling phase.

[0038] From this combination, a mask 28 is formed, which is converted into a binary mask 30 by thresholding 29. By backprojecting 31 this binary mask 30 into the reconstructed 3D volume 22, a mask volume 32 is obtained, which is then post-processed with threshold segmentation 33 to create a final virtual vessel volume 34. This corresponds to a volume adapted to and representing the state of the current 2D DSA series.

[0039] Subsequently, intensity adjustments and optimization can be performed by starting from the acquisition of the reconstructed 3-D volume 22 (fl) for a viewing angle α and recording the DSA series 27 p(α) for iFlow evaluation, creating the final virtual vessel volume 34 (f2) according to the description based on the Fig. 6 and Fig. 7 is generated. A forward projection of f2(α)→p2(α) with iterative minimization, for example by gradient descent X(p2(α))−[p(α)∗M2]→min, in which factor X is adjusted.

[0040] The factor X is a parametric basis function, e.g. polynomial, for adjusting the forward-projected intensities, but in its simplest form it is a scaling factor (scalar).

[0041] X(p2(α)) is used to subtract only the vessels 20: - Since X(p2(α)) is a volume, this can be done for any angulations or subseries. - A partial subtraction of the vessels 20 is also possible by adjusting the volume accordingly.

[0042] Thus, starting from the filling image 17 of the DSA, one arrives at the following Fig. 4 to one in Fig. 8 shown superimposed brain parenchyma representation 34 of the parenchyma 19, which can be used very well for post-processing, for example with syngo iFlow.

[0043] Based on the filling image 17 of the DSA according to Fig. 4. However, in addition to separating the parenchyma 19, one can also extract only the vessels 20 and represent them in a vascular image 33, as is done by the Fig. 9 shows.

[0044] To enable further improved visualization, allowing users to choose whether to view only parenchyma 19, only vessels 20, or a combination thereof, transmission bars 38 to 40 can be provided. Bar 38 would indicate the transmission level for brain parenchyma, bar 39 for anatomical background, and bar 40 for vessels. Furthermore, transmission bars 38 to 40 could be implemented as sliders 41, allowing the transmission levels to be adjusted separately. This would enable numerous combinations of different parameters to be easily achieved, for example, by moving the sliders 41 with the mouse. Additionally, a digital percentage display 42 could be assigned to transmission bars 38 to 40.

[0045] In the one based on the Fig. A key component of the inventive method described in sections 3 to 7 is the creation of a vessel volume f2 using the original 3D volume f1, e.g., a 3D rotational angiography or a computed tomography angiography (CTA), and the current DSA series. The volume f2 includes only the vessels that are also found in the DSA. The differences between 2D and 3D could be manifold, e.g., different injections, injection sites, contrast agent concentrations, etc.

[0046] A 3D scan that is as close as possible to the 2D series is recommended; alternatively, an intravenous 3D rotational angiography can be performed, in which as many vessels (arteries and veins) as possible are visualized according to the procedure as described above. Fig. 6 and Fig. 7 can be selectively removed.

[0047] The vessel segmentation in the 3D volume is inherent to the nature of 3D datasets, especially in 3D DSA. A forward projection 24 creates a virtual vessel projection 25, which exhibits a different vessel configuration than the current series. From the virtual vessel projection 25, a vessel mask 26 is created and combined with the current DSA series, ideally a maximum occlusion image 27 (if an iFlow combination is desired later). This results in mask 28, which is then binaryized to mask 30. The binary mask 30 is backprojected into volume 22 and subsequently post-processed with threshold segmentation 33 to create the final virtual volume 34. This volume corresponds to and represents the state of the current 2D DSA series.

[0048] Since the intensities are not adjusted and the intensities or attenuation caused by the vessels are to be selectively subtracted later, the described adjustment of intensities and optimization must be applied. This minimizes intensity differences that could arise, for example, from a different contrast agent concentration or different blood flow conditions. The basic function X is used as a correction function to subsequently make the subtraction of the vessels at the intensity level as accurate as possible.

[0049] Subsequently, the subtraction can be performed to extract only the parenchyma 19 according to Fig. 8 to represent, whereby partial subtractions e.g. only arteries or only veins are also possible by additional segmentation or selection in X(p2(α)).

[0050] The starting point for an inventive superimposition of a multiparametric representation of the vascular geometry, the anatomical background and the brain parenchyma within a DSA series is a successful segmentation of the parenchyma and the vascular configuration, as can be achieved, for example, by means of the Fig. 6 and Fig. 7. Additionally, 3D segmentation of the vessels can be used for vessel configuration, which is projected forward in 2D for the corresponding geometry, similar to the procedure according to syngo iPilot, which is briefly described in the flyer “syngo iPilot - Effective guidance during interventional procedures”, Siemens AG, Medical Solutions, 2005 / 11, Order No. A91AX-20004-11C-1-76, or “CaseStudies / Redefining 3D imaging during intervention / syngo DynaCT / syngo InSpace 3D / syngo iDentify / syngo iPilot”, Siemens AG, Medical Solutions, Order No. A91AX-20009-11C1-7600, CC AX 20009 WS 10063, 10.2006.

[0051] The vessels are superimposed as an overlay onto the parametric map of the dynamic 2D angiography (2D-DSA). This can be a color-coded representation of the mean transit time (MTT) or time to peak (TTP), which can be calculated from the dynamic data. The vessel geometry can be displayed and varied in another visualization format, such as rendering, as needed. This can be either the vessels from the segmentation or the 3D data from a 3D angiography dataset, similar to the application of syngo iPilot.

[0052] Additionally, the decoupled images can display different parameters. For example, the vascular overlay can show the TTP values ​​and the underlying parenchyma representation can show the MTT.

[0053] At the same time, the anatomical background, e.g., the bony structures, is captured as a third independent image and also used as an overlay, so that a triple overlay image with different blend ratios can be created, as is the case, for example, in the Fig. 10 is shown.

[0054] The following are achieved through the method according to the invention: - a "vessel"-free DSA representation, for example for a parametric and color-coded representation, - use as an iFlow image for calculating blood flow parameters in the (brain) parenchyma, for example in TTP (Time to Peak) visualizations, - also applicable to other body regions when movements and / or other major changes need to be compensated for, - a possible partial subtraction to represent only certain parts of the brain without blood vessels, - any angulation selection via 3-D and / or an iterative adjustment of the intensities to avoid subtraction artifacts.

[0055] Furthermore, the inventive method enables: - a combined presentation of angiography and parenchymal imaging, - an overlay of vessels on parametric maps as a "roadmap" function, - a decoupling of macroscopic and microscopic blood flow, so that different parameters can be calculated and visualized, - a fading in and out of the vascular structure, - 3D integration through a combination with, for example, syngo iPilot and / or - a triple overlay functionality.

Claims

[1] Angiographic examination method for generating at least one 2-D projection image of a vascular system (20, 23) in a body region of interest of a patient (6) using an angiography system (1 to 4) characterized by the following steps: S1 Acquisition of a volume dataset of the body region of interest including the vascular system (23), S2 Reconstruction of a 3-D volume (22) from the volume dataset with the vascular system (23), S3 forward projection (24) to generate a virtual projection (25) with the vessels (20), S4 Derivation of a binary vascular mask (26) from the virtual projection (25), S5 Acquisition of at least one recent 2-D image (27), S6 Combination of the binary vascular mask (25) with at least one current 2D image (27) to form a current mask (28), S7 Threshold calculation (29) of the current mask (28) to form a current binary mask (30), S8 Backprojection (31) of the current binary mask (30) into the 3-D volume (22) to form a mask volume (32), S9 Threshold segmentation (33) of the mask volume (32) to create a final virtual vessel volume (34) and S10 Subtraction of a projection of the vessel volume (34) from the current 2-D images (27) to generate a selective non-overlapping representation of the body region of interest with selectable parameters. [2] Angiographic examination method according to claim 1, characterized by that the acquisition of a volume data set according to procedure step S1 is carried out using rotational angiography. [3] Angiographic examination method according to claim 1 or 2, characterized by , that the procedure step S2 includes a segmentation of the vascular system (20, 23). [4] Angiographic examination method according to any one of claims 1 to 3, characterized by , that the virtual projection (25) according to procedure step S3 is a virtual 2-D-DSA. [5] Angiographic examination method according to any one of claims 1 to 4, characterized by , that the current 2-D images (27) are from a current measured 2-D DSA series. [6] Angiographic examination method according to claim 5, characterized by , that the 2-D images currently acquired according to procedure step S5 are maximum pacification images (27) of a 2-D DSA series. [7] Angiographic examination method according to any one of claims 1 to 6, characterized by , that an adjustment of intensities and optimization takes place before process step S10. [8] Angiographic examination method according to any one of claims 1 to 7, characterized by, that the transmission levels of the components to be superimposed (16, 35, 36) can be adjusted for the selective, non-overlapping representation of the body region of interest. [9] Angiographic examination method according to claim 8, characterized by , that the transmission coefficients of the components to be superimposed (16, 35, 36) can be adjusted separately. [10] Angiographic examination method according to claim 8 or 9, characterized by , that adjusting means are provided for the separate adjustment of the transmission levels and are designed in such a way that transmission bars (38 to 40) characterizing the setting can be displayed. [11] Angiographic examination method according to claim 10, characterized by , that the transmission bars (38 to 40) are designed in the form of sliders or sliders (41). [12] Angiographic examination method according to claim 10 or 11, characterized by, that the adjustment means are designed in such a way that the transmission coefficients are adjusted by moving the sliders (41) with the mouse. [13] Angiographic examination method according to any one of claims 9 to 12, characterized by , that a digital percent display (42) is assigned to the transmission bars (38 to 40) to show the proportions to be superimposed (16, 35, 36).

Images