Integration of Medical Imaging and Position Tracking

Abstract

The present invention is entitled "Integration of Medical Imaging and Position Tracking". It relates to a position tracking system that maps an anatomical structure in a first coordinate system to a fixed position within a medical imaging system, and the position tracking system captures 3D images in a second coordinate system. According to a first coordinate transformation, the 3D images are converted into a standardized format in a third coordinate system and stored in the standardized format. The first 3D image captured by the imaging system is registered with the first coordinate system so as to generate a second coordinate transformation. The first coordinate transformation and the second coordinate transformation are combined so as to derive a third coordinate transformation between the first coordinate system and the third coordinate system. A second 3D image of the body of a subject captured by the imaging system is processed so as to extract image features in the third coordinate system. The extracted image features are combined with the position data captured by the position tracking system by applying the third coordinate transformation.

Description

Technical Field

[0001] The present invention relates generally to medical devices, and in particular, to combining images from multiple medical imaging and tracking devices. Background Art

[0002] In medical imaging, a region of a subject is imaged by a medical imaging device. In some cases, such as in heart disease diagnosis, the same region is mapped using a position tracking system. The resulting images and maps can be presented in the coordinate system of the imaging or mapping device, as well as in standardized formats and coordinate systems such as DICOM (Digital Imaging and Communications in Medicine). Various third-party programs can be used to further analyze medical images.

[0003] Various methods of comparing images and maps from different devices are described in the patent literature. For example, US Patent Application Publication 2015 / 0178448 describes a method of sending a data request from a first medical device to a second medical device using a communication protocol that includes messages for conveying medical measurements.

[0004] As another example, US Patent Application Publication No. 2007 / 0014453 describes a method for registering a measured MRI volume image with an appropriate atlas of anatomical and blood supply regions so that Atlas information can be mapped onto the measured MRI volume image.

[0005] As another example, US Patent Application Publication No. 2006 / 0159323 describes systems and methods for automatically registering intraoperative electrophysiological (EP) points of a three-dimensional (3D) preoperative image of an anatomical structure with a 3D electroanatomical (EA) image of the anatomical structure.

[0006] As another example, US Patent Application Publication No. 2009 / 0088628 describes systems and methods related to enhanced medical workflow.

[0007] US Patent 9,474,466, the disclosure of which is incorporated herein by reference, describes a positioning pad including a housing having a planar surface and a plurality of field generators The plurality of field generators are secured to the housing and are configured to generate respective magnetic fields having respective axes perpendicular to the planar surface.

[0008] U.S. Patent No. 9,638,820 describes an apparatus including a detector assembly, a positioning unit, and interface circuitry, the disclosure of which is incorporated herein by reference. The detector assembly includes an array of a plurality of magnetic field detectors. The positioning unit is configured to fix the detector assembly at one or more known positions relative to a positioning pad that generates a magnetic field for performing position measurements on the in-vivo magnetic field detectors using a positioning system. The interface circuitry is configured to output an electrical signal generated by the magnetic field detectors of the detector assembly when the detector assembly is fixed at the known positions, so as to calibrate the results of the position measurements performed by the positioning system. SUMMARY OF THE INVENTION

[0009] Embodiments of the present invention described below provide improved methods for analyzing medical images.

[0010] Accordingly, embodiments of the present invention provide a method for registering images. The method includes installing a position tracking system configured to map an anatomical structure in a first coordinate system to a fixed position within a medical imaging system, the position tracking system capturing a three-dimensional (3D) image of the anatomical structure in a second coordinate system. The 3D image is converted to a standardized format in a third coordinate system and stored in the standardized format according to a first coordinate transformation between the second coordinate system and the third coordinate system. A first 3D image captured by the imaging system is registered with the first coordinate system so as to generate a second coordinate transformation between the first coordinate system and the second coordinate system. The first coordinate transformation and the second coordinate transformation are combined so as to derive a third coordinate transformation between the first coordinate system and the third coordinate system. A second 3D image of a subject's body captured by the imaging system is processed so as to extract image features in the third coordinate system. The extracted image features are combined with position data captured by the position tracking system by applying the third coordinate transformation.

[0011] In the disclosed embodiments, the position tracking system includes a magnetic tracking system, and registering the first 3D image with the first coordinate system includes inserting a fixture including a calibration target into the medical imaging system, capturing the fixture in the first 3D image, and measuring the position of the calibration target.

[0012] In some embodiments, the medical imaging system includes a magnetic resonance imaging (MRI) system or a computed tomography (CT) system.

[0013] In the disclosed embodiments, the third coordinate system is defined according to the Digital Imaging and Communications in Medicine (DICOM) protocol, and processing the second 3D image includes reading and processing the second 3D image by a software application compliant with the DICOM protocol.

[0014] In some embodiments, processing the second 3D image includes at least one of rotating the image and segmenting the image.

[0015] In addition or alternatively, the position data captured by the position tracking system includes the position of the distal end of the catheter within the anatomical structure in the body.

[0016] Still in addition or alternatively, combining the extracted image features with the position data includes simultaneously displaying the extracted image features and the position data on a display.

[0017] Embodiments according to the present invention also provide a device for displaying registered images. The device includes a position tracking system configured to map an anatomical structure in a first coordinate system. A medical imaging system in which the position tracking system is mounted in a fixed position is configured to capture a three-dimensional (3D) image of the anatomical structure in a second coordinate system. The 3D image is converted into a standardized format in a third coordinate system and stored in the standardized format according to a first coordinate transformation between the second coordinate system and the third coordinate system.

[0018] A processor is configured to register a first 3D image captured by the imaging system with the first coordinate system so as to generate a second coordinate transformation between the first coordinate system and the second coordinate system. The processor combines the first coordinate transformation and the second coordinate transformation so as to derive a third coordinate transformation between the first coordinate system and the third coordinate system, and processes an image of the subject's body captured by the imaging system so as to extract image features in the third coordinate system. It combines the extracted image features with the position data captured by the position tracking system after applying the third coordinate transformation to the position data.

[0019] With reference to the accompanying drawings, the present invention will be more fully understood through the following detailed description of embodiments of the present invention, in which: Description of the Drawings

[0020] Figure 1 Is a schematic diagram of a system according to an embodiment of the present invention, the system including a position tracking system in cooperation with a medical imaging system;

[0021] Figure 2 Is a schematic diagram of a registration jig according to an embodiment of the present invention;

[0022] Figure 3 Is a schematic diagram of a registration assembly according to an embodiment of the present invention;

[0023] Figure 4 Is a schematic pictorial view of three coordinate systems according to an embodiment of the present invention;

[0024] Figure 5 Is a block diagram schematically showing three coordinate systems according to an embodiment of the present invention;

[0025] Figure 6 A block diagram schematically showing a process for combining medical images and location data processed by a third - party application according to an embodiment of the present invention; and

[0026] Figure 7 A flowchart schematically showing a process for combining and displaying medical images and location data according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] Overview

[0028] In - vivo probes such as catheters are used in a variety of therapeutic and diagnostic medical procedures. The catheter is inserted into a patient's living body and navigated to a target region within a body cavity in order to perform a medical procedure. In a magnetic - field - based position - tracking system, an external magnetic field is applied to the patient's body. The magnetic field is generated by a plurality of magnetic - field generators (e.g., field - generating coils), which are typically fixed in a positioning pad near the patient. Sensors mounted in the distal end of the catheter respond to the magnetic field by generating electrical signals. The tracking system then uses this signal to locate the position and orientation of the catheter within the patient's body.

[0029] Magnetic positioning tracking of the catheter can be performed in or near a medical imaging system, as described, for example, in the references cited above in the background section. The combination of these two systems enables, in particular, the joint display of magnetic position - tracking and medical imaging data.

[0030] DICOM (Digital Imaging and Communications in Medicine) is a standard protocol for storing medical images among other things. Many third - party applications that allow the manipulation and / or analysis of the stored medical images are available, typically operating in the Visualization Toolkit (VTK) format. For example, such applications can be used to rotate and segment the images. Displaying magnetic position - tracking data (such as the position of the catheter) along with the rotated and segmented images would be very useful for medical professionals manipulating the catheter. However, generally speaking, this joint display can only be performed offline because the manipulated and / or analyzed images are stored in the DICOM coordinate system, while the position - tracking system operates in a coordinate system typically defined by the positioning pad of the system.

[0031] Embodiments of the present invention described herein solve the above problems by providing a simple and seamless registration between a position tracking system and a standard coordinate system used in medical image processing applications such as the DICOM coordinate system. This registration is initially performed between the position tracking system and a medical imaging system such as an MRI scanner, and then applied to derive a coordinate transformation between the position tracking system and the image processing coordinate system. The initial registration generally needs to be performed only once, but the derived transformation can be reused thereafter, enabling the position tracking results to be integrated with a variety of different applications using the standard image processing coordinate system in both real-time and offline applications.

[0032] In the disclosed embodiments, a position tracking system that maps the position of an anatomical structure in a positioning coordinate system is installed at a fixed position within a medical imaging system, which captures a three-dimensional (3D) image of the anatomical structure in a device coordinate system. The 3D image is converted to a standardized format such as DICOM and stored in the patient coordinate system according to a first coordinate transformation between the device coordinate system and the patient coordinate system. A second coordinate transformation between the locator coordinate system and the device coordinate system is derived by registering the 3D image captured by the imaging system with the locator coordinate system. The first coordinate transformation and the second coordinate transformation are then combined to derive a third coordinate transformation between the locator coordinate system and the patient coordinate system.

[0033] Subsequently, when a 3D image of a subject's body is captured by the imaging system and then converted into a standardized patient coordinate system and processed, for example, to extract image features, the extracted image features can be combined with the position data generated by the position tracking system within the subject by applying the same (third) coordinate transformation. Thus, the initial one-time derivation of this transformation enables the use of any one of a variety of third-party applications to display the manipulated and / or processed medical image while viewing in real-time the information provided by the position tracking system. This capability can be used, for example, to overlay an icon representing a catheter tracked by the position tracking system or electrophysiological mapping data collected by the catheter on a medical image.

[0034] System Description

[0035] Figure 1 FIG. 13 is a schematic illustration of a system 20 according to an embodiment of the present invention, the system including a position tracking system in conjunction with a medical imaging system. Figure 1 And the following description is based in part on the above-mentioned U.S. Patent No. 9,638,820.

[0036] In the illustrated embodiment, the position tracking system includes a magnetic position tracking system 21, and the imaging system includes a magnetic resonance imaging (MRI) scanner 22. However, the principles of the present invention can be similarly applied to other types of medical imaging systems, such as computed tomography (CT) scanners, and other types of position tracking systems, such as impedance-based tracking systems and ultrasound tracking systems, which will be apparent to those skilled in the art. All such alternative embodiments are considered to be within the scope of the present invention.

[0037] The magnetic tracking system 21 can be implemented as, for example, the 3 system manufactured by Biosense Webster of 33 Technology Drive, Irvine, CA 92618, USA. The MRI scanner 22 can be implemented as, for example, the MAGNETOM Aera manufactured by Siemens Healthcare GmbH of Henkestrasse 127, 91052 Erlangen, Germany.

[0038] The magnetic tracking system 21 includes an in-vivo probe 24, such as a catheter, and a console 26. An operator 30, such as a cardiologist, navigates the catheter 24 through the vascular system of a patient 32 via the skin such that the distal end 34 of the catheter 24 enters a body cavity, which is assumed herein to be a heart cavity. The catheter 24 can be used, for example, to register the electrical potential in the chambers of the heart 28 of the patient 32, where a plurality of electrodes are disposed near the distal end 34 of the catheter 24 and contact the tissue of the heart cavity at multiple points. In an alternative embodiment, with the necessary modifications, the catheter 24 can be used for other therapeutic and / or diagnostic functions in the heart or other body organs.

[0039] The console 26 uses magnetic position sensing to determine the orientation and position coordinates of the distal end 34 of the catheter 24 inside the heart 28. The console 26 operates a drive circuit 36 that drives one or more magnetic field generators 39 in a positioning pad 38 under the patient's torso on a workbench 37 as shown in the dashed-line inset 72 in the Figure 1 upper right corner. Alternatively, the positioning pad 38 can have a different shape and be positioned at a different location, such as above the patient 32, to conform to the spatial requirements of a particular MRI scanner 22.

[0040] In response to the magnetic field generated by the positioning pad 38, a position sensor mounted in the distal end 34 generates an electrical signal, enabling the console 26 to determine the position and orientation of the distal end relative to the positioning pad and thus the position and orientation within the heart 28 of the patient 32.

[0041] The MRI scanner 22 includes a magnetic field coil 29, which includes field gradient coils, and the magnetic field coil and the field gradient coils together generate a spatially-varying magnetic field. The spatially-varying magnetic field provides spatial localization for radiofrequency (RF) signals generated by the scanner. In addition, the scanner includes a transmit / receive coil 31. In the transmit mode, the coil 31 radiates RF energy into the patient 32, and the RF energy interacts with the nuclear spins of the patient tissue and thus realigns the magnetic moments of the nuclei away from their equilibrium positions. In the receive mode, as the tissue nuclei relax to their equilibrium state, the coil 31 detects the RF signals received from the patient tissue.

[0042] Figure 1 The MRI scanner 22 shown includes a structure that opens along one side of the patient 32. Alternatively, the MRI scanner 22 can have a different tubular structure, such as, for example, the previously mentioned Siemens MAGNETOM Aera scanner.

[0043] The table 37 in the MRI scanner 22 generally supports the patient 32, as shown in the illustration 72. However, in the illustrated embodiment, the registration fixture 70 is placed on the table 37 to register the coordinate system of the MRI scanner 22 with the coordinate system of the magnetic catheter tracking system, as described in the aforementioned U.S. Patent No. 9,638,820. Details of the registration process will be further described below. The fixture 70 is placed on the table 37 above the positioning pad 38 within the MRI scanner 22, in a position that is generally the same as the area where the torso of the patient 32 would be positioned on the table 37.

[0044] In Figure 1 the illustrated embodiment, the processor 40 has multiple functions. First, the processor 40 is configured to receive the electrical signals induced in the position sensor at the distal end 34 of the catheter in response to the magnetic field generated by the positioning pad 38 via an interface circuit (not shown). The processor 40 uses the received electrical signals to locate the catheter within the patient.

[0045] Second, the processor 40 operates the MRI scanner 22 by: using circuitry to control the MRI coil 29, including forming the required magnetic field gradients, and using other circuitry to operate the transmit / receive coil 31 around the patient 32. The processor 40 acquires the volume of interest 308 ( Figure 4MRI data within (as shown) will be described below. For example, the volume of interest 308 may include the heart 28 of the patient 32. The processor 40 uses the MRI data to display an image 44 of the heart 28 to the operator 30 on the display 42. The position of the catheter 24 acquired by the magnetic tracking system 21 may be superimposed on the image 44 of the heart 28 on the display 42 acquired by the MRI scanner 22. As will be further described below, the operator 30 may use a third-party application to process the MRI data and display the processed medical image 446 with the image of the catheter 24 superimposed thereon ( Figure 6 ).

[0046] The processor 40 generally includes a general-purpose computer that is programmed with software to implement the functions described herein. For example, the software may be downloaded electronically into the processor 40 via a network, or the software may be provided on a non-transitory tangible medium such as an optical storage medium, a magnetic storage medium, or an electronic storage medium. Alternatively, some or all of the functions of the processor 40 may be implemented by dedicated or programmable digital hardware components, or by using a combination of hardware and software elements.

[0047] Alternatively, the functions of the processor 40 may be divided among two or more processors. For example, one processor manages the magnetic position tracking system and another manages the MRI scanner. More generally, Figure 1 the embodiments shown are presented for purposes of conceptual clarity only and are in no way limiting of the embodiments of the present invention. The MRI scanner 22 and the magnetic tracking system 21 may have separate processors for each system rather than being shared as in the embodiment shown in system 20. A single or separate display may be used for the MRI scanner 22 and the magnetic tracking system 21.

[0048] Registration of the Coordinate Systems of the MRI Scanner and the Magnetic Tracking System

[0049] Figure 2 is a schematic illustration of a registration fixture 70 according to an embodiment of the present invention. The registration fixture 70 includes a positioning unit 210 having a plurality of slots 220 that are separated by a fixed predetermined distance between adjacent slots. The fixture 70 is disposed above the positioning pad 38, as Figure 1 shown. For other configurations and positions of the positioning pad 38, the fixture 70 may be placed in different positions. For example, for a positioning pad 38 positioned against the inner top plate of the MRI scanner 22, the fixture 70 may be placed below it.

[0050] The registration assembly 200 is also referred to as a shelf and includes an array of cubic containers 230. Other forms of containers 230 are also applicable, as will Figure 3As shown. The registration assembly 200 can be inserted into any one of the slots 220 in the positioning unit 210. The plurality of slots in the positioning unit 210 are configured to fix the registration assembly 200 at one or more known positions relative to the positioning pad 38. In Figure 2 In the embodiment shown, the slot 220 controls the position (e.g., height) of the registration assembly 200 relative to the positioning pad 38.

[0051] The substrate 250 of the positioning unit 210 is connected to a conformable adapter 260, which is configured to conform to and be shaped to fit the shape of the positioning pad 38, such that the array of containers 230 will be located in the X-Y plane at a fixed distance above the positioning pad and orthogonal to the Z-axis. X 1 、Y 1 and Z 1 axes are the coordinate axes of the Cartesian first coordinate system 252. The adapter 260 can be formed or machined by any suitable method to conform to the curvature of the positioning pad 38. The positioning pad 38 is shown here as an example and is described in more detail in the above-mentioned U.S. Patent 9,638,820. Alternatively, other types of positioning pads and calibration jigs can be used for the purposes of the present invention, which will be apparent to those skilled in the art after reading this specification.

[0052] Figure 3 is a schematic diagram of a registration assembly 202 according to an embodiment of the present invention. The registration assembly 202 serves the same purpose as the Figure 2 registration assembly 200 and can be similarly used in the jig 70.

[0053] The registration assembly 202 includes an 8×8 array of containers 230, each having a conical protrusion 232 at its center. The containers 230 are filled with an MRI-detectable fluid, such as water, and serve as MRI image reference markers. All or a subset of the containers 230 are filled with fluid. Filling an asymmetric subset of the containers 230 will facilitate uniquely determining the orientation of subsequent MRI images. The fluid can be sealed in the volume of the container by any suitable procedure. Alternatively, the containers 230 can remain unsealed. Still alternatively, the reference markers can include MRI-detectable fluid-filled spheres having a known radius, as described in the above-mentioned U.S. Patent 9,638,820.

[0054] In an alternative embodiment including different types of medical imaging systems, the registration assembly 202 can include reference markers of different substances. For example, for an embodiment in which the medical imaging system includes an x-ray-based imager (such as a computed tomography (CT) system), the reference markers can be filled with a substance that is opaque or partially opaque to x-rays, such as calcium.

[0055] When the registration assembly 202 is placed in the positioning unit 210, the MRI scanner 22 images the registration array of the fluid-filled container 230, and the processor 40 registers the known positions of these containers in the system 20 relative to the positioning pad 38. Then, the known positions of the fluid-filled containers 230, which act as MRI reference markers, are used to register the coordinate systems of the MRI scanner 22 and the magnetic tracking system 21. In other words, the processor 40 uses an array of multiple MRI reference markers 230 that are fixed in at least one known position relative to the positioning pad 38 by the positioning unit 210 to register the coordinate systems.

[0056] To improve resolution, the positioning unit can be configured to continuously change the known position of the assembly within the separation distance between adjacent slots 220 after the assembly is fixed in a particular slot, so as to continuously fine-tune the height in the Z Figure 2 -direction as shown in 1 -direction. For example, one or more turning screws 270 can be embedded in the conforming adapter 260 and oriented in the Z 1 -direction such that rotating the turning screw 270 moves the substrate 250 or jacks up the substrate 250, and thereby adjusts the Z 1 -position of the unit 210 relative to the conforming adapter 260.

[0057] Figures 2 to 3 The embodiments shown in

[0058] Coordinate System

[0059] Figure 4 are shown for purposes of conceptual clarity only as examples of devices and methods that can be used to register the tracking system 21 and the MRI scanner 22, and are not limiting of the embodiments of the present invention. After reading this specification, other kinds of registration devices and methods will be apparent to those skilled in the art and are considered to be within the scope of the present invention.

[0060] 1. The first coordinate system 252 marked by axes X 1 、Y 1 and Z 1 (shown in Figure 2 ) is the coordinate system of the magnetic tracking system 21. This coordinate system is also referred to as the locator coordinate system (LCS). The coordinate system 252 is oriented such that its Z 1 -axis is perpendicular to the workbench 37, and the Y 1 -axis is oriented along the long axis of the workbench. Depending on the position and orientation of the positioning pad 38, the Z 1The axis points up or down. The origin 300 of the first coordinate system 252 is located at a user-defined point on the reference positioning pad 38.

[0061] 2. The second coordinate system 302 is the coordinate system of the MRI scanner 22, also known as the Device Coordinate System (DCS). It is oriented such that its Z 2 axis is along the long axis of the worktable 37, and its Y 2 axis is perpendicular to the worktable. Its origin 304 is located at the isocenter of the MRI scanner 22, where the isocenter is the center of symmetry of the scanner's magnetic field and is known to the scanner. Thus, the second coordinate system 302 is permanently fixed to the MRI scanner 22.

[0062] 3. The third coordinate system 306 is the Patient Coordinate System (PCS). The third coordinate system 306 is aligned with the sides of the volume of interest 308 (usually a rectangular parallelepiped), and its origin is centered within the volume of interest. The volume of interest 308, shown in dashed inset 312, is defined by the operator 30 using the console 26 with reference to a low-resolution MRI scan, where the volume of interest encompasses the anatomical volume to be imaged at high resolution, such as the heart 28 for example. Thus, the third coordinate system 306 is stored in the processor 40 together with the second coordinate system 302. Both the volume of interest 308 and the third coordinate system 306 are typically shifted and rotated by known amounts with respect to the second coordinate system 302 as recorded by the processor 40. The third coordinate system 306 is the system used by the DICOM protocol and is thus used by third-party applications to manipulate medical images stored as DICOM files.

[0063] The three coordinate systems are summarized in Table 1 below.

[0064] Table 1: Summary of Coordinate Systems

[0065] Coordinate System Marker Reference Structure Alternative Name DICOM Coordinates First Coordinate System 252 Magnetic Tracking System 21 Location Coordinate System (LCS) No Second Coordinate System 302 MRI Scanner 22 Device Coordinate System (DCS) No Third Coordinate System 306 Volume of Interest 308 Patient Coordinate System (PCS) Yes

[0066] Coordinate Transformation

[0067] Figure 5 A block diagram schematically showing the coordinate transformation between the above-mentioned coordinate systems according to an embodiment of the present invention.

[0068] Block 400 refers to the magnetic tracking system 21 with its first coordinate system 252. Block 402 refers to the MRI scanner 22 with its two coordinate systems: the second coordinate system 302 and the third coordinate system 306. Arrow 404 represents the third coordinate system 306 defined by the volume of interest 308 according to the DICOM protocol. The spatial relationship between the second coordinate system 302 and the third coordinate system 306 is known to the processor 40 respectively, and thus the processor calculates the first coordinate transformation TX 1(shown as double arrow 406), which is a transformation between the second coordinate system and the third coordinate system.

[0069] The second coordinate transformation TX shown as double arrow 408 2 is a transformation between the first coordinate system 252 and the second coordinate system 302. It is calculated by the processor 40 based on the above registration procedure.

[0070] The third coordinate transformation TX shown as double arrow 410 3 is calculated by the processor 40 as the product between the first coordinate transformation TX 1 and the second coordinate transformation TX 2 . The third coordinate transformation TX 3 transmits the transformation between the first coordinate system 252 and the third coordinate system 306, that is, the transformation between the coordinates of the magnetic tracking system 21 in the LCS and the coordinates according to the DICOM protocol in the PCS.

[0071] The algorithm applied by the processor 40 to the coordinate transformation is based on a 4×4 matrix, where each matrix implements a specific action. The individual 4×4 matrices and their effects are listed in Table 2 below.

[0072] Table 2: Individual Coordinate Transformation Matrices

[0073]

[0074]

[0075] Each coordinate transformation matrix in Table 2 or their product affects the coordinate transformation by multiplying a 4×1 vector where the first three elements are the xyz coordinates, and the fourth element is necessary for the translation operation. Thus, the coordinate transformations TX 1 and TX 2 are 4×4 matrices, and the coordinate transformation TX 3 is the matrix product of the first two matrices.

[0076] Figure 6 is a block diagram schematically showing the process for combining a medical image 440 and position data 442 processed by a third-party application in, for example, a DICOM coordinate system according to an embodiment of the present invention.

[0077] The MRI scanner 22 generates a medical image 440 of the patient 32 in a third coordinate system 306, i.e., in the DICOM coordinate system. The medical image 440 is processed by the processor 40 using a third-party application indicated by the arrow 444, resulting in a processed medical image 446, which is also represented in DICOM coordinates. Processing of the medical image 440 includes, for example, rotating and / or segmenting the image. The magnetic tracking system 21 generates position data 442 of the catheter 24 in a first coordinate system 252. A third coordinate transformation TX 3 is applied by the processor 40 to the position data 442, thereby transforming the position data from the first coordinate system 252 into the third coordinate system 306, i.e., into the DICOM coordinate system.

[0078] The processor 40 then presents on the display 42 a combined image 448 of the catheter 24 superimposed on the processed medical image 446. To register the coordinate systems 252 and 306, no recalibration or re-registration is required because the previously calculated transformation can be used for this purpose. The same method can be used to display other types of data provided by the magnetic tracking system 21, such as marking or coloring the processed medical image 446 to show electrophysiological data collected by the catheter.

[0079] Figure 7 FIG. 500 is a flow chart that schematically shows a process for combining and displaying medical images and position data according to an embodiment of the present invention.

[0080] The preparation phase 540 starts with a registration step 502, in which the MRI scanner 22 and the magnetic tracking system 21 are registered with each other, as described above. In a second coordinate transformation step 504, the processor 40 calculates a second coordinate transformation TX 2 .

[0081] In a patient insertion step 506, the patient 32 is inserted into the MRI scanner 22. In a volume of interest step 508, a low-resolution scan of the patient 32 is performed with the MRI scanner 22, and the operator 30 uses the console 26 to define a volume of interest 308 as the volume for a subsequent high-resolution MRI scan. In a first coordinate transformation step 510, a first coordinate transformation TX 1 is calculated between the second coordinate system 302 (device coordinate system, DCS) and the third coordinate system 306 (patient coordinate system, PCS, in DICOM coordinates).

[0082] In a third coordinate transformation step 512, a third coordinate transformation TX 3 is calculated between the first coordinate system 252 (LCS) and the third coordinate system 306 (PCS) as TX 1and TX 2 The product of step 512 completes the preparation stage 540.

[0083] In start step 514, imaging and position tracking of patient 32 are started, although not necessarily simultaneously, as detailed below. In MRI scan step 516, the volume of interest 308 is scanned by an MRI scanner with high-resolution scanning, so that in image generation step 518, a medical image 440 is generated in the third coordinate system 306. In read step 520, the medical image 440 is read by a processor running a third-party software application, and in processing step 522, it is further processed by the application to produce a processed image 446.

[0084] Position tracking of catheter 24, for example, is started in tracking step 524 by means of a magnetic tracking system 21. The position tracking can be delayed until after the completion of MRI scan step 516 to avoid interference of the magnetic field of the MRI scanner 22 with the position tracking. In position data step 526, the position tracking generates position data in the first coordinate system 252. In transformation application step 528, the coordinate transformation TX 3 is applied to the position data from position data step 526, thereby transforming the position data into DICOM coordinates.

[0085] In combination step 530, the processed image 446 from processing step 522 and the position data in DICOM coordinates from transformation application step 528 are combined to create a combined image 448, which can be displayed on the display 42 and viewed by the operator 30. In all steps 518, 520, 522, 528, and 530, both the medical image data and the position data are represented in DICOM coordinates so as to enable the use of third-party applications and the joint display of the image data and the position data.

[0086] In decision step 532, the operator 30 decides whether he / she wishes to modify the processed image 446 by a third-party application, for example, by rotating the image or segmenting the image. In decision step 532, the operator 30 can also decide to move the catheter 24 and thus obtain new position data. Modifying the processed image 446 and moving the catheter 24 both reactivate steps 522 and 524 respectively. The loop from decision step 532 to steps 522 and 524 can occur in a continuous manner. For example, the operator 30 can continuously move the catheter 24 and observe the changing position of the catheter on the combined image 448. The operator 30 can also, for example, continuously rotate the processed image 446 while observing the position of the catheter 24 in the rotated image. The operator 30 can also continuously change the position of the processed image 446 and the catheter 24 and observe these changes in the dynamically changing combined image 448.

[0087] The medical procedure being performed by the operator 30 can, for example, change the shape and dimensions of the anatomical details observed within the volume of interest 308 by performing surgery on an organ within the volume of interest. Based on the operator's experience and observations, he / she may decide that the medical image needs to be updated. In such a case, the operator 30 can initiate a new MRI scan, as indicated by the dashed arrow 536. When the MRI scanner 22 is acquiring a new scan during the MRI scan step 516, position tracking can be stopped. Once the scan is completed, the process returns to the two paths starting at steps 518 and 524.

[0088] The procedure ends with a final step 534.

[0089] It should be understood that the above-described embodiments are cited by way of example, and the present invention is not limited to what has been specifically shown and described above. On the contrary, the scope of the present invention includes combinations and sub-combinations of the various features described above, as well as their variations and modifications, which would occur to those skilled in the art upon reading the above description and which are not disclosed in the prior art.

Claims

1. A method for registering images, the method comprises: Installing a position tracking system configured to map an anatomical structure in a first coordinate system to a fixed position within a medical imaging system, the medical imaging system capturing a three-dimensional (3D) image of the anatomical structure in a second coordinate system, wherein the 3D image is converted to a standardized format in the third coordinate system and stored in the standardized format according to a first coordinate transformation between the second coordinate system and the third coordinate system; Registering a first 3D image captured by the imaging system with the first coordinate system to generate a second coordinate transformation between the first coordinate system and the second coordinate system; Combining the first coordinate transformation and the second coordinate transformation to derive a third coordinate transformation between the first coordinate system and the third coordinate system; Processing a second 3D image of the subject's body captured by the imaging system to extract image features in the third coordinate system; and Combining the extracted image features with position data captured by the position tracking system by applying the third coordinate transformation, The method further comprises the following steps: A registration step, wherein an MRI scanner and the position tracking system are registered with each other, A second coordinate transformation step, wherein a processor calculates the second coordinate transformation between the second coordinate system and the first coordinate system, wherein the second coordinate system is a device coordinate system and the first coordinate system is a position coordinate system, A patient insertion step, wherein the subject's body is inserted into the MRI scanner, A volume of interest step, wherein a low-resolution scan of the subject's body is performed using the MRI scanner, and an operator defines a volume of interest as the volume for subsequent high-resolution MRI scans using a console, A first coordinate transformation step, wherein the first coordinate transformation is calculated between the second coordinate system and the third coordinate system, wherein the third coordinate system is a patient coordinate system, A third coordinate transformation step, wherein the third coordinate transformation is calculated between the first coordinate system and the third coordinate system as the product between the first coordinate transformation and the second coordinate transformation, A start step, wherein imaging and position tracking of the subject's body are started, An MRI scan step, wherein the volume of interest is scanned by the MRI scanner with high-resolution scanning, An image generation step, which includes generating a medical image in the third coordinate system, A reading step, wherein the medical image is read by the processor, A processing step, wherein the medical image is further processed to produce a processed image, A tracking step, wherein position tracking of a catheter by the position tracking system is started, A position data step, wherein the position tracking generates position data in the first coordinate system, A transformation application step, wherein the third coordinate transformation is applied to the position data from the position data step, and the position data is transformed into medical digital imaging and communications (DICOM) protocol coordinates, and Combination step, wherein the processed image from the processing step and the position data in the medical digital imaging and communications (DICOM) protocol coordinates from the transformation application step are combined to create a combined image.

2. The method according to claim 1, wherein the position tracking system comprises a magnetic tracking system.

3. The method according to claim 2, wherein registering the first 3D image with the first coordinate system comprises inserting a fixture including a calibration target into the medical imaging system, capturing the fixture in the first 3D image, and measuring the position of the calibration target.

4. The method according to claim 1, wherein the third coordinate system is defined according to the medical digital imaging and communications (DICOM) protocol.

5. The method according to claim 4, wherein processing the second 3D image comprises reading and processing the second 3D image by a software application compliant with the DICOM protocol.

6. The method according to claim 1, wherein processing the second 3D image comprises at least one of rotating the image and segmenting the image.

7. The method according to claim 1, wherein the position data captured by the position tracking system comprises the position of the distal end of a catheter within an anatomical structure in the body.

8. The method according to claim 1, wherein combining the extracted image features with the position data comprises simultaneously displaying the extracted image features and the position data on a display.

9. A device for displaying registered images, the device comprising: A position tracking system configured to map an anatomical structure in a first coordinate system; A medical imaging system, the position tracking system being mounted at a fixed position within the medical imaging system, and the medical imaging system being configured to capture a three-dimensional (3D) image of the anatomical structure in a second coordinate system, wherein the 3D image is converted to a standardized format in the third coordinate system and stored in the standardized format according to a first coordinate transformation between the second coordinate system and the third coordinate system; A processor configured to: Register a first 3D image captured by the imaging system with the first coordinate system to generate a second coordinate transformation between the first coordinate system and the second coordinate system; Combine the first coordinate transformation and the second coordinate transformation to derive a third coordinate transformation between the first coordinate system and the third coordinate system; Process a second 3D image of a subject's body captured by the imaging system to extract image features in the third coordinate system; and Combine the extracted image features with position data captured by the position tracking system after applying the third coordinate transformation to the position data, wherein the device is configured to utilize in the execution of the following steps: A registration step, wherein an MRI scanner and the position tracking system are registered with each other, A second coordinate transformation step, in which the processor calculates the second coordinate transformation between the second coordinate system and the first coordinate system, where the second coordinate system is the device coordinate system and the first coordinate system is the position coordinate system, a patient insertion step, in which the body of the subject is inserted into the MRI scanner, A volume of interest step, in which a low-resolution scan of the body of the subject is performed using the MRI scanner, and in which the operator uses a console to define a volume of interest as the volume for subsequent high-resolution MRI scans, A first coordinate transformation step, in which the first coordinate transformation is calculated between the second coordinate system and the third coordinate system, where the third coordinate system is the patient coordinate system, A third coordinate transformation step, in which the third coordinate transformation is calculated between the first coordinate system and the third coordinate system as the product between the first coordinate transformation and the second coordinate transformation, A start step, in which imaging and position tracking of the body of the subject are started, An MRI scan step, in which the volume of interest is scanned by the MRI scanner with high-resolution scanning, An image generation step, which includes generating a medical image in the third coordinate system, A reading step, in which the medical image is read by the processor, A processing step, in which the medical image is further processed to produce a processed image, A tracking step, in which position tracking of the catheter by the position tracking system is started, A position data step, in which the position tracking produces position data in the first coordinate system, A transformation application step, in which the third coordinate transformation is applied to the position data from the position data step, where the position data is transformed into medical digital imaging and communications (DICOM) protocol coordinates, and A combination step, in which the processed image from the processing step and the position data in the medical digital imaging and communications (DICOM) protocol coordinates from the transformation application step are combined to create a combined image.

10. The apparatus according to claim 9, wherein the position tracking system includes a magnetic tracking system.

11. The apparatus according to claim 10, wherein the first 3D image is registered with the first coordinate system by inserting a jig including a calibration target into the medical imaging system, capturing the jig in the first 3D image, and measuring the position of the calibration target.

12. The apparatus according to claim 11, wherein the third coordinate system is defined according to the medical digital imaging and communications (DICOM) protocol.

13. The apparatus according to claim 12, wherein the processor is configured to read and process the second 3D image using software compliant with the DICOM protocol.

14. The apparatus according to claim 9, wherein processing the second 3D image includes at least one of rotating the image and segmenting the image.

15. The device according to claim 9, wherein the position data captured by the position tracking system includes the position of the distal end of the catheter within the anatomical structure in the body.

16. The device according to claim 9, wherein the processor is configured to simultaneously display the extracted image features and the position data on a display.

Images