Search

DE-102024212291-B3 - Reconstruction of an image in medical imaging

DE102024212291B3DE 102024212291 B3DE102024212291 B3DE 102024212291B3DE-102024212291-B3

Abstract

The invention relates to a method for reconstructing an image of an object (7) in medical imaging by - Providing (S1) a first truncated projection image (pi) of the object (7), which projects an area of the object to be mapped from a first projection source position (Ci) into a first projection plane, - Providing (S2) a 3D model (M) specific to the object (7) including a modeled area to be mapped which corresponds to the area to be mapped of the object (7), - Generating (S3) a first supplementary forward projection (ei1) of a first supplementary area of the 3D model (M), which extends beyond and borders the modeled area to be mapped, from the first projection source position (Ci) into the first projection plane and - Reconstructing (S6) the image on the basis of the first truncated projection image (pi) and the first supplementary forward projection (ei1) of the first supplementary area.

Inventors

  • Daniel Punzet
  • Robert Frysch
  • Georg Rose
  • Michael Manhart
  • Jessica Schulz

Assignees

  • Siemens Healthineers Ag

Dates

Publication Date
20260513
Application Date
20241223

Claims (7)

  1. Method for reconstructing an image of an object (7) in medical imaging, characterized by : - providing (S1) a first truncated projection image (pi) of the object (7), which projects an image area of the object from a first projection source position (Ci) into a first projection plane; - providing (S2) a 3D model (M) specific to the object (7), including a modeled image area corresponding to the image area of the object (7); - generating (S3) a first supplementary forward projection (ei1) of a first supplementary area of the 3D model (M), which extends beyond and adjoins the modeled image area, from the first projection source position (Ci) into the first projection plane, whereby the first truncated projection image (pi) and the first supplementary forward projection (ei1) are registered relative to each other; - generating a second supplementary forward projection (ei2) of a second supplementary area of the 3D model (M), which extends beyond the modeled area to be mapped and adjoins it, in particular on a side of the modeled area to be mapped opposite the first supplementary area, from the first projection source position (Ci) into the first projection plane, - Reconstructing (S6) the image on the basis of the first truncated projection image (pi) and the first supplementary forward projection (ei1) of the first supplementary area and the second supplementary forward projection (ei2) of the second supplementary area, wherein the two supplementary forward projections (ei1, ei2) correspond to a first pair, which is generated with respect to the first projection source position (Ci), analogously adjacent to a second truncated projection image (pj) in a second projection plane different from the first, a second pair of supplementary forward projections (ej1, ej2) is obtained by means of the 3D model (M) in the second projection plane, which is generated with respect to a second projection source position different from the first. (Cj) is generated, and the reconstruction of the image is performed based on both pairs of complementary forward projections (ei1, ei2, ej1, ej2) and both truncated projection images (pi, pj), wherein a first intermediate function is created for the first truncated projection image (pi) and the first complementary forward projection (ei1), and a second intermediate function is created for the second truncated projection image (pj) and a corresponding complementary forward projection (ej1, ej2), and an error between the two intermediate functions is calculated and optimized, and wherein epipolar lines (li, Ij) in the complementary forward projections (ei1, ei2, ej1, ej2) are used for calculating the respective intermediate function, and the epipolar lines (li, Ij) together with the two projection source positions (Ci, Cj) lie in one plane.
  2. Method for reconstructing an image of an object (7) in medical imaging, characterized by : - providing (S1) a first truncated projection image (pi) of the object (7), which projects an image area of the object from a first projection source position (Ci) into a first projection plane; - providing (S2) a 3D model (M) specific to the object (7), including a modeled image area corresponding to the image area of the object (7); - generating (S3) a first supplementary forward projection (ei1) of a first supplementary area of the 3D model (M), which extends beyond and adjoins the modeled image area, from the first projection source position (Ci) into the first projection plane, whereby the first truncated projection image (pi) and the first supplementary forward projection (ei1) are registered relative to each other; - generating a second supplementary forward projection (ei2) of a second supplementary area of the 3D model (M), which extends beyond the modeled area to be mapped and is adjacent to it, in particular on a side of the modeled area to be mapped opposite the first supplementary area, from the first projection source position (Ci) into the first projection plane, and - Reconstructing (S6) the image on the basis of the first truncated projection image (pi) and the first supplementary forward projection (ei1) of the first supplementary area and the second supplementary forward projection (ei2) of the second supplementary area, wherein the two supplementary forward projections (ei1, ei2) correspond to a first pair, which is generated with respect to the first projection source position (Ci), in an analogous manner adjacent to a second truncated projection image (pj) in a second projection plane different from the first, a second pair of supplementary forward projections (ej1, ej2) is obtained by means of the 3D model (M) in the second projection plane, which is generated with respect to a second projection plane different from the first. The projection source position (Cj) is generated, and the image is reconstructed based on both pairs of complementary forward projections (ei1, ei2, ej1, ej2) and both truncated projection images (pi, pj), wherein a first intermediate function is created for the first truncated projection image (pi) and the first pair of complementary forward projections (ei1, ei2), and a second intermediate function is created for the second truncated projection image (pj) and the second pair of complementary forward projections (ej1, ej2), and an error between the two intermediate functions is calculated and optimized, and wherein epipolar lines (li, Ij) in the complementary forward projections (ei1, ei2, ej1, ej2) are used for calculating the respective intermediate function, and the epipolar lines (li, Ij) together with the two projection source positions (Ci, Cj) lie in one plane.
  3. Procedure according to one of the Claims 1 or 2 , where values of the respective intermediate function are calculated for the respective complementary forward projections (ei1, ei2, ej1, ej2) before the respective projection images (pi, pj) of the object are provided.
  4. Method according to one of the preceding claims, wherein the 3D model (M) is based on previously obtained recordings of the object (7) or of another object of the same type as the object.
  5. Method according to one of the preceding claims, wherein the image to be reconstructed is a tomographic image or a 3D image.
  6. Imaging modality comprising a data processing unit and a control unit configured to perform a method according to any of the preceding claims.
  7. Computer program, comprising commands that are executed during the execution of the program by the imaging modality according to Claim 6 These cause the procedure to be carried out according to one of the Claims 1 until 5 to execute.

Description

The present invention relates to a method for reconstructing an image of an object in medical imaging. Furthermore, the present invention relates to a computed tomography method, an imaging modality, and a computer program. For the unambiguous reconstruction of tomographic images from projections, the projection data must completely depict the entire cross-section (in the lateral direction) of the object or patient. If the projections are not complete but truncated, this is called truncation. Truncated projection data occur in medical imaging, for example, when the patient is too large for the detector or when the projections were deliberately only partially acquired (e.g., by collimating the beam path), for example, to minimize radiation dose (volume-of-interest (VO1) imaging). To obtain usable reconstruction results, the truncated projections are typically extended (extrapolated) using established methods with a heuristic extrapolation model to minimize the resulting image artifacts. Approaches to this are shown in the following two articles: Sourbelle, K., Kachelriess, M., Calendar, WA Reconstruction from truncated projections in CT using adaptive detruncation. Eur Radiol 15, 1008-1014 (2005 ). https://doi.org/10.1007/s00330-004-2621-9 and Hsieh, J., Chao, E., Thibault, J., Grekowicz, B., Horst, A., McOlash, S., Myers, TJ (2004): A novel reconstruction algorithm to extend the CT scan field-of-view. In Medical physics 31 (9), pp. 2385-2391. DOl: 10.1118/1.1776673 . However, a previous volumetric dataset (e.g., a planning CT scan) of the patient often already exists. This can be used for further imaging procedures, for example, to reduce radiation exposure. For this, newly acquired 2D projection data must be registered onto the existing 3D volumetric dataset. The goal of registering 2D projection data and 3D volume data of an object with respect to each other is to determine a suitable geometric transformation that establishes a common spatial relationship between both datasets. An overview of the topic can be found in van de Kraats, EB, Penney, GP, Tomazevic, D., van Walsum, T., Niessen, WJ "Standardized evaluation methodology for 2-D-3-D registration," in IEEE Transactions on Medical Imaging, vol. 24, no. 9, pp. 1177-1189, Sept. 2005, doi: 10.1109/TMI.2005.853240 to find. In 2D-3D registration of projection and volume data, two datasets are available: 2D projections of a specific area of the object (ideally the entire object) and a 3D volume dataset of the same object or patient. To transform both datasets into a common spatial reference system, forward projections of the volume dataset (so-called Digitally Reconstructed Radiographs (DRRs)) are typically simulated repeatedly. The parameters of the geometric transformation that result in the smallest error compared to the given projections, in terms of a similarity metric, are determined through optimization. Applying a geometric transformation with these calculated parameters to the given data then performs the determined registration. In the case of truncated projection data (i.e., the object was only partially mapped), this approach becomes difficult because, as a rule, only feature-based similarity metrics can be used to compare DRR and existing projection data. From the article by D. Kolditz et al., “A Volume-of-interest (VOI) imaging in C-arm flat-detector CT for high image quality at reduced dose”, Medical physics, 2010, vol. 37, no. 6, pp. 2719-2730 A method for reconstructing an image of an object in flat-panel detector computed tomography is known, in which a complete low-dose overview (OV) scan and a local high-dose scan of a volume of interest (VOI) are combined. (From the article by...) J. Wiegert et al. “Projection Extension for Region Of Interest Imaging in Cone-Beam CT”, Academic radiology, 2005, Volume 12, No. 8, pp. 1010-1023 A method for extending truncated projections to avoid truncation artifacts in C-arm-based 3D ROI imaging is known, which utilizes prior knowledge by combining forward projections of a previously acquired, untruncated 3D reference image with the truncated ROI projections. US 2007/0195923 A1 A method for reconstructing an image created using a cone beam CT is known, in which truncations are corrected. The object of the present invention is to improve the quality of image reconstruction in medical imaging. This problem is solved according to the invention by the subject matter of the independent claims. Solved. Advantageous further developments of the invention are set out in the dependent claims. According to the invention, a method for reconstructing an image (e.g., a tomographic image or 3D image) of an object in medical imaging is provided. The object can be a patient, a part of a patient, or an object within a patient. Such an object would be, for example, a catheter or an implant. Medical imaging can be performed using computed tomography, angiography, and the like. The basis of the respective medical imaging is