# US 9,519,949 B2 · Determining transformation between different coordinate systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,519,949 B2 - Document ID: US9519949B2 - Status: Granted - Kind: B2 - Application number: 14/656,765 - Filed: 2015-03-13 - Published: 2016-09-15 - Granted: 2016-12-13 - Earliest claimed: 2015-03-13 - Assignees: Koninklijke Philips N.V. - Applicants: Koninklijke Philips N.V. - Inventors: Stéphane Allaire; Alexandra Groth; Juergen Weese - Web page: https://patentgrep.com/patent/US9519949B2 ## CPC - G06T 7/33: using feature-based methods - G06F 18/22: Matching criteria, e.g. proximity measures - G06T 3/00: Geometric image transformations in the plane of the image - G06T 7/0012: {Biomedical image inspection} - G06T 2207/10072: Tomographic images - G06T 2207/10132: Ultrasound image - G06T 2207/30048: Heart; Cardiac - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) ## Abstract A system (100) is provided for determining a transformation between different coordinate systems associated with different medical data. In determining the transformation, the system (100) makes use of a third set of anatomical landmarks (040) defined in a reference coordinate system to match a first set of anatomical landmarks (010) defined in a first coordinate system to a second set of anatomical landmarks (020) defined in a second coordinate system. Effectively, the third set of anatomical landmarks is used as an intermediary in obtaining the transformation between both input sets of coordinate systems. As the third set of anatomical landmarks includes the anatomical landmarks of both input sets, it is not needed for both input sets to be identical or even to overlap. Rather, even in case both input sets are entirely disjunct, i.e., not-overlapping, it is still possible to determine the transformation between the different coordinate systems. ## Claims ### Claim 1 A system for determining a transformation between different coordinate systems associated with different medical data, comprising: a landmark input for obtaining first coordinates representing a first set of anatomical landmarks in a first coordinate system and second coordinates representing a second set of anatomical landmarks in a second coordinate system; a matching subsystem configured for: providing reference coordinates representing a third set of anatomical landmarks in a reference coordinate system, the third set of anatomical landmarks comprising the first set of anatomical landmarks and the second set of anatomical landmarks; and determining a transformation between the first coordinate system and the second coordinate system by: i) determining a first intermediate transformation between the first coordinate system and the reference coordinate system by matching the first set of anatomical landmarks to the third set of anatomical landmarks; ii) determining a second intermediate transformation between the second coordinate system and the reference coordinate system by matching the second set of anatomical landmarks to the third set of anatomical landmarks; and iii) combining the first intermediate transformation and the second intermediate transformation to obtain the transformation. ### Claim 2 (depends on 1) The system according to claim 1, wherein the third set of anatomical landmarks is defined with respect to a deformable model such that the reference coordinates representing the third set of anatomical landmarks is defined in a reference coordinate system associated with the deformable model, the deformable model being arranged for fitting an anatomical structure in a medical image. ### Claim 3 (depends on 2) The system according to claim 2, wherein the deformable model represents a mean shape of the anatomical structure across a plurality of patients, or a patient adapted model adapted for the anatomical structure of a patient. ### Claim 4 (depends on 2) The system according to claim 2, wherein the deformable model is represented by model data defining geometry of the anatomical structure in the medical image, and wherein the third set of anatomical landmarks is encoded in the model data. ### Claim 5 (depends on 1) The system according to claim 1, wherein each landmark of the first set of anatomical landmarks, the second set of anatomical landmarks and the third set of anatomical landmarks is constituted by a coordinate and an anatomical label, and wherein the matching subsystem is configured for matching sets of anatomical landmarks by matching anatomical labels of the sets of anatomical landmarks. ### Claim 6 (depends on 5) The system according to claim 5, wherein the matching subsystem is configured for differently weighting matching anatomical landmarks when obtaining the first intermediate transformation and/or the second intermediate transformation. ### Claim 7 (depends on 1) The system according to claim 1, wherein the first set of anatomical landmarks is defined with respect to a first medical image and the second set of anatomical landmarks is defined with respect to a second medical image. ### Claim 8 (depends on 7) The system according to claim 7, wherein the matching subsystem is configured for using the transformation to mutually align the first medical image and the second medical image. ### Claim 9 (depends on 8) The system according to claim 8, further comprising a display subsystem for simultaneously displaying the first medical image and the second medical image after said mutually aligning. ### Claim 10 (depends on 1) The system according to claim 1, wherein the matching subsystem is configured for using the transformation to complement the first set of anatomical landmarks with one or more anatomical landmarks of the second set of anatomical landmarks. ### Claim 11 (depends on 1) The system according to claim 1, wherein the first set of anatomical landmarks is defined with respect to a first mesh, the second set of anatomical landmarks is defined with respect to a second mesh, and wherein the matching subsystem is configured for using the transformation to mutually align the first mesh and the second mesh. ### Claim 12 (depends on 1) The system according to claim 1, wherein the first set of anatomical landmarks and the second set of anatomical landmarks are non-identical or disjunct sets. ### Claim 13 (depends on 1) Workstation or imaging apparatus comprising the system according to claim 1. ### Claim 14 A method for determining a transformation between different coordinate systems associated with different medical data, comprising: obtaining first coordinates representing a first set of anatomical landmarks in a first coordinate system; obtaining second coordinates representing a second set of anatomical landmarks in a second coordinate system; providing reference coordinates representing a third set of anatomical landmarks in a reference coordinate system, the third set of anatomical landmarks comprising the first set of anatomical landmarks and the second set of anatomical landmarks; and determining a transformation between the first coordinate system and the second coordinate system by: i) determining a first intermediate transformation between the first coordinate system and the reference coordinate system by matching the first set of anatomical landmarks to the third set of anatomical landmarks; ii) determining a second intermediate transformation between the second coordinate system and the reference coordinate system by matching the second set of anatomical landmarks to the third set of anatomical landmarks; and iii) combining the first intermediate transformation and the second intermediate transformation to obtain the transformation. ### Claim 15 (depends on 14) A non-transitory computer-readable medium storing computer program product comprising instructions for causing a processor system to perform the method according to claim 14.