Intraluminal 3D imaging method and medical system

Abstract

For improved image quality, a method is provided for intraluminal 3D imaging by means of a catheter device introduced into a hollow organ of an examination object, having an image recording device and a measuring device with an optical fibre, in particular multifunctional shape-sensing (= MFSS) fibre, during a movement of the catheter device through the hollow organ, the method comprising the following steps: recording at least two cross-sectional images using the image recording device at different recording positions within the hollow organ, and simultaneously with each cross-sectional image, carrying out at least one sensor measurement by the measuring device using the optical fibre, evaluating the sensor measurements by the optical fibre in such a way that a current orientation of the image plane of the cross-sectional images recorded by the image recording device is determined at the respective recording position, in particular relative to the hollow organ and / or the centre line of the hollow organ, and reconstructing the at least two cross-sectional images by the image recording device to form a 3D volume of the hollow organ taking into account the evaluated orientations of the image planes of the cross-sectional images.

Description

[0001] Description

[0002] Methods for intraluminal 3D imaging and medical systems

[0003] The invention relates to a method for intraluminal 3D imaging according to claim 1 and a medical system for carrying out such a method according to claim 10.

[0004] In minimally invasive examinations or procedures, e.g., supported by C-arm angiography systems, therapies and / or diagnoses are performed using instruments inserted into the body through small incisions, e.g., in the groin. To navigate to the region of interest, e.g., a vascular target, or to visualize catheters and other instruments, X-ray fluoroscopy (especially fluoroscopy) has typically been used. To minimize the radiation exposure, newer methods utilize 3D fiber optics, which can detect the shape and position of an inserted optical fiber using intrinsic light reflections. This allows, for example, the visualization of guide wires within the body by measuring their shape and position and virtually representing them in a model or image of the body.For example, the treatment of aortic aneurysms by inserting a stent graft is a specific therapy in which these instruments are useful. The inserted instrument, such as a guide wire or a catheter, has an optical fiber running along its length for localization purposes, which is permanently attached to the instrument.

[0005] Another way to examine and visualize larger hollow organs, such as blood vessels, is intraluminal imaging, for example, using imaging devices like IVUS (intravascular ultrasound) or OCT (optical coherence tomography). Here, the catheter device (for example, automatically or semi-automatically using a robotic device) is withdrawn in a controlled manner after insertion into the hollow organ, and cross-sectional images (2D) are acquired regularly using the imaging device. The cross-sectional images are then stitched together and reconstructed to form a volume. For the reconstructions, either the positions of the imaging device are additionally measured during the acquisition of the cross-sectional images, or it is assumed that the cross-sectional images were acquired equidistant from each other. However, distortions often occur during the reconstruction due to inaccurate position determinations and rotation or tilting of the imaging device, for example.by bending of the hollow organ. Optionally, the cross-sectional images are registered as externally acquired angiographic X-ray images to improve the quality of the reconstruction and, for example, to correct rotations of the imaging device around the centerline (see, e.g., C. Slager et al. “True 3-Dimensional Reconstruction of Coronary Arteries in Patients by Fusion of Angiography and IVUS (ANGUS) and its Quantitative Validation”, https: / / www.ahaioumals.org / doi / 10.1161 / 01.ClR.102.5.511; August 1, 2000).

[0006] It is an object of the present invention to provide a method for intraluminal 3D imaging which enables improved image quality; furthermore, it is an object of the invention to provide a device suitable for carrying out the method.

[0007] The problem is solved according to the invention by a method for intraluminal 3D imaging using a catheter device inserted into a hollow organ of an examination object according to claim 1 and by a medical system according to claim 10. Advantageous embodiments of the invention are the subject of the respective dependent claims.

[0008] The inventive method for intraluminal 3D imaging using a catheter device inserted into a hollow organ of an object under investigation, comprising an image acquisition device and a measuring device with an optical, in particular multifunctional shape-sensing (=MFSS), fiber, during movement of the catheter device through the hollow organ, comprises the following steps: Acquisition of at least two cross-sectional images of the image acquisition device at different acquisition positions within the hollow organ, and simultaneously, for each 2D image, performance of at least one sensor measurement of the measuring device using the optical fiber, evaluation of the sensor measurements of the optical fiber such that a current orientation of the image plane of the cross-sectional image acquired by the image acquisition device at the respective acquisition position is determined.The method involves, in particular, the reconstruction of at least two cross-sectional images of the image acquisition device into a 3D volume of the hollow organ, taking into account the evaluated orientations of the image planes of the cross-sectional images. This method optimizes image quality simply and quickly, enabling improved diagnosis and correspondingly better patient treatment. This is achieved primarily through a more precise capture of the actual geometric relationships within the hollow organ with respect to any tilting of the image acquisition system relative to the centerline. Such tilting causes a tilted image plane of the respective cross-sectional image and thus a distortion of the 3D volume reconstructed from the cross-sectional images.When cross-sectional images are juxtaposed during reconstruction, they are incorrectly assumed to be parallel. This method takes this tilt into account by using the actual orientation of the image planes and their effect on the reconstruction, or by correcting the reconstruction to compensate for the tilt. The inventive method thus leads to higher image quality of the reconstructed volume and therefore to a significant improvement in patient care.

[0009] According to one embodiment of the invention, the measuring device consists of a fiber-optic shape detection system with at least one multifunctional shape-sensing fiber, and the sensor measurements measure a bending of the fiber, which is evaluated as the orientation of the image plane. Fiber-optic shape detection is prior art and allows, for example, the determination of the curvature and shape of an optical fiber in 2D and 3D. A typical fiber-optic shape detection system, such as the one that can be used in this method, consists of a sensor, a measuring device, and a processing unit with algorithms for evaluating the measured data. Essentially, the measurement determines the strain in the fiber by means of the interference of several light beams that are transmitted through and reflected in the fiber.In a fiber consisting of a bundle of multiple optical fibers, some of the outer fibers experience relative stress or compression relative to the central fiber, thus registering positive or negative induced strain changes. To calculate local curvature or the bending radius, the relative strains of the fibers are measured and processed. To determine the fiber's curvature profile, the measurements are processed using specialized reconstruction algorithms. These algorithms can determine not only bends around a point, but also radii of curvature, curvature directions, pressure, temperature, forces, and torsions.

[0010] Multifunctional shape-sensing fibers are known, for example, in the context of Pathfinder technology (The Shape-Sensing Company), see https: / / shapesensing.com / pathfinder-platform / and https: / / shapesensing.com / .

[0011] In a further embodiment of the invention, the image acquisition device is formed by an IVUS (intravascular ultrasound) device or an OCT (optical coherence tomography) device. Both devices are prior art and particularly suitable for intraluminal imaging. In a typical examination, a robotically driven catheter system with an IVUS or OCT device is inserted into the hollow organ, e.g., by means of a robot-assisted drive system, moved to a desired location, and then, during a smooth withdrawal movement, regular cross-sectional images are acquired, which are subsequently reconstructed.

[0012] According to a further embodiment of the invention, a multitude of cross-sectional images and simultaneous sensor measurements are recorded at a multitude of different positions within the hollow organ, evaluated, and reconstructed into a 3D volume of the hollow organ.

[0013] In a further embodiment of the invention, the orientations of the image planes of the cross-sectional images acquired by the image-taking device are determined relative to the center line of the hollow organ, for example, as a tilt angle of the normal of the image plane of the cross-sectional image to the center line. This angle is then checked, for example, by comparing it with a threshold value. If the tilt angle is significant, for example, more than 5°, measures are taken, such as a correction of the reconstruction. The correction can, for example, be carried out by checking or correcting the sequence of the cross-sectional images or parts of the cross-sectional images if the tilt has caused an overlap of the image planes of adjacent cross-sectional images. The correction can also (additionally or alternatively) consist of filling gaps in the reconstructed volume caused by the tilt.Interpolation can bridge gaps, or closely spaced or overlapping areas can be corrected by superimposition. To determine the precise geometric relationships, the distances between the image planes of any two adjacent cross-sectional images in the region of the hollow organ wall can be determined and used to correct the reconstruction. A particularly precise method for determining such distances between the image planes of any two adjacent cross-sectional images in the region of the hollow organ wall can be expressed as follows: dupper = d - (r*sin Qi + r*sin O2) and di. ower = d + (r*sin Qi + r*sin 02) , where d is the distance between two cross-sectional images in the region of the centerline, r is the radius of the cross-sectional images, a1 is the tilt angle of the image plane of the first cross-sectional image, and a2 is the tilt angle of the image plane of the second cross-sectional image relative to the centerline. If one of the distances is negative, this means that an overlap of the cross-sectional images is to be expected. According to a further embodiment of the invention, projection images of the hollow organ are simultaneously acquired using an externally arranged X-ray device and used for reconstruction. In this way, registration of the catheter device to the hollow organ and thus verification of the acquisition positions is possible.

[0014] The invention further comprises a medical system for carrying out a method described above, comprising a catheter device with a catheter and an image acquisition device, a measuring device comprising a multifunctional shape-sensing fiber which is arranged at least partially in the area of ​​the image acquisition device on the catheter device, a measuring unit and an evaluation unit for evaluating the sensor measurements of the optical fiber in such a way that a current orientation of the image plane of the cross-sectional images recorded by the image acquisition device is determined at the respective recording position, and an image processing unit for reconstructing the cross-sectional images of the image acquisition device taking into account the evaluated orientations of the image planes of the cross-sectional images.In order to ensure that the catheter device can be withdrawn evenly and thus simplify reconstruction, the medical system advantageously includes a robotic control system with a drive device and a control unit for moving and controlling the robotically controlled catheter device through a hollow organ of a patient.

[0015] According to one embodiment of the invention, the medical system includes a calculation unit for calculating the distances between the image planes of any two adjacent cross-sectional images in the region of the hollow organ wall. The calculation can be performed according to the corresponding formulas as described above.

[0016] The medical system may also include an X-ray machine with a control system for capturing X-ray images during the procedure. The X-ray machine, for example a C-arm X-ray machine, angiography X-ray machine, or CT scanner, can simultaneously capture X-ray images alongside cross-sectional images and use them for registration, positioning, and / or orientation.

[0017] The invention and further advantageous embodiments according to the features of the dependent claims are explained in more detail below with reference to schematically illustrated exemplary embodiments in the drawing, without thereby limiting the invention to these exemplary embodiments. Figure 1 shows a sequence of steps of a method for intraluminal 3D imaging using a catheter device inserted into a hollow organ of an examination subject;

[0018] FIG 2 shows a section through a natural hollow organ and the positions for taking cross-sectional images;

[0019] FIG 3 a straightened view of the hollow organ of FIG 2;

[0020] FIG 4 shows an arrangement with overlapping image planes of two cross-sectional images;

[0021] FIG 5 shows a section through a natural hollow organ and the orientation of the cross-sectional images to the centerline;

[0022] FIG 6 shows a straightened view of the hollow organ of FIG 5;

[0023] FIG 7 shows a geometric representation of the tilt angle of the normal of the image plane of the cross-sectional images to the centerline;

[0024] FIG 8 shows the distances between the image planes of any two adjacent cross-sectional images in the region of the hollow organ wall; and

[0025] FIG 9 a medical system for carrying out the procedure.

[0026] Figure 1 shows a sequence of steps in the procedure for intraluminal 3D imaging using a catheter device inserted into a hollow organ of the subject. For imaging, for example, a known IVUS or OCT imaging technique can be used. IVUS is intravascular ultrasound, in which an ultrasound probe is used as the imaging device; OCT is optical coherence tomography, in which an infrared light probe is used. With known intraluminal 3D imaging techniques, it is always assumed that the image plane of the cross-sectional images is orthogonal to the centerline of the hollow organ; however, since this is often not exactly the case, the reconstruction of the cross-sectional images into a volumetric image results in a partially or completely inaccurate representation of the interior of the hollow organ. Figures 2 to 4 illustrate this problem in more detail.Figure 2 shows a section through a curved hollow organ H with a corresponding centerline C. Cross-sectional images are acquired at a multitude of different imaging positions P along the centerline. The actual image plane 21 of the cross-sectional images does not always correspond to the orthogonal O to the centerline C at the respective imaging position P. In Figure 3, the hollow organ H from Figure 2 is depicted as a straightened tube, making it even clearer that in some cases the actual image plane 21 of the respective cross-sectional image differs significantly from the orthogonal O to the centerline C. Figure 4 shows that the image planes of the cross-sectional images can overlap, particularly in the region of the (inner) hollow organ walls (or even before). The described method corrects these problems and ensures improved image quality of the resulting volume images.

[0027] Figure 9 shows a medical system that can be used to perform the procedure. The catheter device 29 has a catheter 30 which can be moved through the hollow organ by means of a robotic drive 33 and a robot controller 34, optionally including a guide wire. An image acquisition device 31, such as an ultrasound probe or an infrared light probe, is arranged on the distal end of the catheter 30, for example, for acquiring cross-sectional images of the hollow organ at imaging positions. Additionally, at least one or more multifunctional shape-sensing fibers 32 are arranged on the catheter 30, for example, in the area of ​​the image acquisition device or partially or completely along the catheter 30 or guide wire. These fibers are part of a fiber-optic shape-sensing system.The fiber-optic shape detection system additionally includes a measuring device 35 and a processing unit 36 ​​with algorithms for evaluating the measured data. The fiber 32 can be rigidly connected to the catheter device 29, e.g., in the area of ​​the catheter 30. The shape detection system is designed to measure any bending of the fiber(s) 32, so that the orientation of the image acquisition device 31 with respect to the centerline of the hollow organ can be determined from the measurements. The cross-sectional images of the image acquisition device 31 can be reconstructed into a volume image by means of an image processing unit 37, which is designed to take into account the orientation of the cross-sectional images during the reconstruction and its effects. Furthermore, the medical system includes a control unit 38, which controls the execution of the procedure.

[0028] In a first step 10 (see FIG. 1), at least two cross-sectional images are acquired using the image acquisition device arranged on the catheter device, which is located in a hollow organ. The cross-sectional images (2D images) are acquired at different acquisition positions P within the hollow organ H. This can be carried out, for example, while the catheter 30 of the catheter device moves through the hollow organ H, for example, in the form of a controlled retraction movement driven by the robotic drive / robot controller. The acquisition positions P can be arranged, for example, at regular intervals within the hollow organ H, although irregularly distributed acquisition positions P are also possible. In general, it is assumed that the acquisition positions P are located in the region of the centerline C of the hollow organ H, but this is not always the case and is not strictly necessary.The cross-sectional images are 2D images whose image plane depends on how the catheter device 29, and thus the image acquisition device 31 attached to it, is positioned or oriented (e.g., tilted / inclined with respect to the centerline) within the (e.g., curved) hollow organ at the time of acquisition. To maintain the orientation of the image plane of the cross-sectional image, at least one sensor measurement is simultaneously acquired for each of the acquired cross-sectional images using (at least) one multifunctional shape-sensing fiber 32 (or associated fiber-optic shape detection system).

[0029] In a second step 11, the corresponding orientation of the image plane of the cross-sectional image is determined from the sensor measurements for each recording position. For example, using a known method, a (two- or three-dimensional) bend of the fiber(s) at the respective recording position is evaluated from the sensor measurements using the fiber-optic shape detection system and related to the (two- or three-dimensional) bend of the hollow organ or its centerline C. The relative orientation can be specified, for example (simplifying because it is two-dimensional), as a tilt angle α of the normal N of the image plane 21 to the centerline C of the hollow organ H at the respective recording position P, as shown in Figures 5 to 7. The relative orientation can also be specified spatially (i.e., using two tilt angles in different planes, etc.). The position / shape and / or orientation of the hollow organ can be determined using various methods.whose centerline additionally uses pre-op or live recorded X-ray images (2D or 3D).

[0030] In a third step 12, the cross-sectional images from the image acquisition device are then reconstructed into a 3D volume of the hollow organ, taking into account the evaluated relative orientations of the image planes of the cross-sectional images (e.g., relative to the centerline). This consideration can, for example, involve checking for overlaps of the image planes of the cross-sectional images based on these orientations, thus preventing the erroneous assumption that the image planes of the cross-sectional images are parallel. If adjacent cross-sectional images overlap—see FIG. 4—the reconstruction is corrected accordingly. This may, for example, include taking into account that some depicted areas may need to be swapped in terms of their order.Figure 8 shows how distances between image planes of adjacent cross-sectional images in the region of hollow organ walls can be determined, which provide an indication of possible overlaps of the image planes of adjacent cross-sectional images. Previously, the tilt angle, for example, was determined based on the evaluations. Thus, at an nth imaging position P. n an nth tilt angle a n the normal of the image plane of the nth cross-sectional image, at an n+1th recording position P n +i an n+1-th tilt angle a n +i of the normal to the image plane of the n+1-th cross-sectional image. The distance d between the image planes at both recording positions, of the n-th recording position P n and the n+1th recording position P n +i, in the region of the centerline C, d is the distance where r is the radius. The following formulas are then used to calculate the upper distance d. up per and the lower distance di ower of the image planes in the area of ​​the hollow organ walls is determined: dupper = d - (r*sin an + r*sin an+1) diower = d + (r*sin an + r*sin an+1)

[0031] This allows the identification of overlapping image planes in the area of ​​the hollow organ wall – in which case one of the (upper or lower) distances will be negative, for example. If a distance is approximately 0, the image planes touch in the corresponding area of ​​the hollow organ wall.

[0032] Considering the evaluated relative orientations of the image planes of the cross-sectional images to the centerline can additionally or alternatively involve filling in identified gaps (e.g., upper or lower distances that are significantly larger than the distance d between the image planes in the area of ​​the centerline C, e.g., at least 20%). Such filling can be performed, for example, by interpolation, such as linear or spline interpolation. For very small upper or lower distances (e.g., 50% smaller than distance d in the area of ​​the centerline C) or overlaps (negative upper or lower distances), the reconstruction can be corrected by superimposing, averaging, or merging the adjacent cross-sectional images.The reconstructed volume exhibits high image quality; errors and inaccuracies caused by an incorrect sequence of cross-sectional images, and thus incorrect positioning of anatomical features, are avoided. Improved diagnosis is possible.

[0033] Additionally, a known correction can also be performed, which compensates for rotation in the axis of the centerline (see article “True 3-Dimensional Reconstruction of Coronary Arteries in Patients by Fusion of Angiography and I US (ANGUS) and its Quantitative Validation” above).

[0034] The hollow organ in question could be, for example, a blood vessel in a human or animal patient, or it could be a bronchial branch. The problem described occurs particularly in larger hollow organs such as the iliac artery or aorta, as tilting of the imaging device is more likely in these cases.

[0035] Information on the recording positions can also be determined using sensor measurements from the optical fiber or other position measurements or obtained from robot information (robotic drive, etc.).

[0036] In particular, the fiber-optic shape acquisition system is registered to an X-ray system, so that the intraluminal cross-sectional images are registered with simultaneously acquired X-ray images. Registration with previously acquired pre-operative X-ray images (volume images) is also possible.

[0037] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

[0038] The invention can be summarized as follows: For improved image quality, a method for intraluminal 3D imaging is provided using a catheter device inserted into a hollow organ of an examination object, comprising an image acquisition device and a measuring device with an optical, in particular multifunctional shape-sensing (=MFSS), fiber, during movement of the catheter device through the hollow organ, comprising the following steps: Acquisition of at least two cross-sectional images of the image acquisition device at different acquisition positions within the hollow organ, and simultaneously, for each cross-sectional image, performance of at least one sensor measurement of the measuring device using the optical fiber, evaluation of the sensor measurements of the optical fiber such that a current orientation of the image plane of the cross-sectional images acquired by the image acquisition device is determined.in particular relative to the hollow organ and / or the centerline of the hollow organ and / or to each other, at the respective recording position, and reconstruction of the at least two cross-sectional images of the image acquisition device into a 3D volume of the hollow organ taking into account the evaluated orientations of the image planes of the cross-sectional images.

Claims

Patent claims 1. Method for intraluminal 3D imaging using a catheter device inserted into a hollow organ of an object under investigation, comprising an image acquisition device and a measuring device with an optical, in particular multifunctional shape-sensing (=MFSS), fiber, during movement of the catheter device through the hollow organ, comprising the following steps: • Recording at least two cross-sectional images of the image recording device at different recording positions within the hollow organ, and simultaneously performing at least one sensor measurement of the measuring device using the optical fiber for each cross-sectional image, • Evaluation of the respective sensor measurement of the optical fiber in such a way that a current orientation of the image plane of the cross-sectional image recorded by the image acquisition device is determined at the respective recording position, in particular relative to the hollow organ and / or the centerline of the hollow organ and / or relative to the image plane of another cross-sectional image, and • Reconstruction of at least two cross-sectional images of the image acquisition device into a 3D volume of the hollow organ, taking into account the evaluated orientations of the image planes of the cross-sectional images.

2. The method of claim 1, wherein the image acquisition device is formed by an IVUS device or an OCT device.

3. Method according to one of the preceding claims, wherein a plurality of cross-sectional images and simultaneous sensor measurements are recorded at a plurality of different recording positions within the hollow organ, evaluated and reconstructed to a 3D volume of the hollow organ.

4. Method according to one of the preceding claims, wherein the orientations of the image planes of the cross-sectional images taken by the image-taking device are determined relative to the centerline of the hollow organ.

5. Method according to one of the preceding claims, wherein distances of the image planes of each two adjacent cross-sectional images in the region of the hollow organ wall are determined and used to determine the sequence of the cross-sectional images during reconstruction.

6. Method according to claim 5, wherein projection images of the hollow organ are simultaneously recorded using an externally arranged X-ray device and used for reconstruction.

7. Method according to one of the preceding claims, wherein the measuring device is formed by a fiber optic shape detection system with at least one multifunctional shape-sensing fiber and the sensor measurements measure a bending of the fiber.

8. Method according to claim 5, wherein distances in the region of the hollow organ wall (d up per and di owe r) can be determined from the two shooting positions and the associated orientations of the image planes, in particular using the following formulas: dupper = d - (r*sin a n + r*sin a n +i) diower = d + (r*sin a n + r*sin a n +i), where d is the distance between two cross-sectional images in the region of the centerline, r is the radius of the cross-sectional images, a n: the tilt angle of the image plane of the nth cross-sectional image and a n +i is the tilt angle of the image plane of the n+1-th (i.e., adjacent to n) cross-sectional image.

9. Method according to one of the preceding claims, wherein the reconstruction is corrected using determined distances.

10. Medical system for carrying out a method according to any one of claims 1 to 9, comprising • a catheter device with a catheter and an image acquisition device, • a measuring device comprising a multifunctional shape-sensing fiber, which is arranged at least partially in the area of ​​the image acquisition device on the catheter device, a measuring unit and an evaluation unit for evaluating the sensor measurements of the optical fiber in such a way that a current orientation of the image plane of the cross-sectional images recorded by the image acquisition device is determined at the respective recording position, and • an image processing unit for reconstructing the cross-sectional images of the image acquisition device, taking into account the evaluated orientations of the image planes of the cross-sectional images.

11. Medical system according to claim 10, comprising a robotic control system with a drive device and a control unit for moving and controlling the robotically controllable catheter device through a hollow organ of a patient.

12. Medical system according to claim 10 or 11, comprising a calculation unit for calculating the distances between the image planes of any two adjacent cross-sectional images in the region of the hollow organ wall.

13. Medical system according to one of claims 10 to 12, comprising an X-ray device with a system control for taking X-ray images during the procedure.

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