Method for establishing compensation information to compensate for a bending of a couch in computed tomography, computed tomography facility, computer program and electronically readable data medium
One or more example embodiments provides a method for establishing compensation information to compensate for a bending of a couch of an object table, in particular patient table, of a computed tomography facility under the weight of an object to be recorded, in particular of a patient, wherein a target region image dataset of a target region of the examination object is recorded with the computed tomography facility at a recording position of the couch, wherein at least one marker visible in x-ray imaging is provided on or in the couch and a three-dimensional reference dataset of the marker is provided for a non-loaded couch, wherein the compensation information is established from a comparison between the reference dataset and the target region image dataset.
1 . A method for establishing compensation information to compensate for a bending of a couch of an object table of a computed tomography facility under a weight of an object to be recorded, wherein a target region image dataset of a target region of an examination object is recorded with the computed tomography facility at a recording position of the couch, the method comprising:
providing at least one marker visible in x-ray imaging at or in the couch;
providing a three-dimensional reference dataset of the marker for a non-loaded couch; and
establishing the compensation information from a comparison between the reference dataset and the target region image dataset, the comparison taking place in a projection space, the comparison including
establishing at least one comparison image with a recording geometry of an assigned projection image of the target region image dataset by forward projection from the reference dataset.
2 . The method of claim 1 , wherein the reference dataset is at least one of (i) established during an initial commissioning of the computed tomography facility with current couch characteristics or (ii) is provided from construction data of the object table.
3 . The method of claim 2 , wherein
the reference dataset is based on a reference height setting being selected such that the at least one marker is acquired in each projection image of a reference measurement for the reference dataset, wherein the reference dataset is shifted by this deviation in a height direction.
4 . The method of claim 1 , wherein at least one elongated marker element at least one of extending in a direction of movement of the couch in parallel to an axis of rotation of an x-ray source of the computed tomography facility or corresponding to a longitudinal direction of the couch is used as the marker.
5 . The method of claim 4 , wherein at least one of
at least one of the marker element extends at least one of over an entire length of the couch or the marker element is integrated into the couch, or
at least one of at least three parallel marker elements are used adjacent thereto, and/or at different heights within the couch.
6 . The method of claim 1 , wherein the reference dataset is established showing only the at least one marker.
7 . The method of claim 1 , wherein, the comparison of the reference dataset with the target region image dataset includes,
comparing the at least one comparison image with the assigned projection image for a number of projection images of the target region image dataset showing at least one of the at least one marker.
8 . The method of claim 7 , wherein the comparison images and the projection images are highpass filtered before the comparison using an identical filter.
9 . The method of claim 1 , further comprising:
establishing comparison images for different relative heights of the at least one marker from the reference dataset based on a recording geometry for the target region image dataset, and
determining an optimized relative height with a highest match between a corresponding comparison image and target region image of the target region image dataset as compensation information.
10 . The method of claim 9 , further comprising:
selecting the optimized height in an optimization algorithm for maximization of a match described by at least one of a measure of similarity or a correlation.
11 . The method of claim 1 , wherein, the establishing includes,
using a trained function using at least one part of the target region image dataset as input data, trained based on the reference dataset, to generate output data.
12 . The method of claim 11 , wherein, as training data for the function to be trained, training datasets, which comprise the reference dataset with at least one marker arranged at different relative heights, are created.
13 . A computed tomography facility for use in processes related to a target region of an object comprising:
an object table with a couch for the object able to be moved in at least one direction, wherein at least one marker visible in x-ray imaging is provided on or in the couch; and
a control facility, the control facility including,
a storage, in which a three-dimensional reference dataset of the marker for a non-loaded couch is stored,
a recording unit configured to record a target region image dataset showing the target region of the object at a recording position of the couch,
a compensation information establishment unit configured to establish compensation information to compensate for a bending of the couch at the recording position under a weight of the object to be recorded, wherein the compensation information establishment unit has a comparison subunit configured to establish the compensation information from a comparison of the reference dataset with the target region image dataset, the comparison taking place in a projection space, the comparison including establishing at least one comparison image with a recording geometry of an assigned projection image of the target region image dataset by forward projection from the reference dataset, and
a compensation facility configured to compensate for localization information relating to the target region.
14 . A non-transitory computer-readable medium including instructions, when executed by a control facility of a computed tomography facility, cause the computed tomography facility to perform the method of claim 1 .
15 . A non-transitory computer-readable medium including instructions, when executed by a control facility of a computed tomography facility, cause the computed tomography facility to perform the method of claim 2 .
16 . The method of claim 3 , wherein at least one elongated marker element at least one of extending in a direction of movement of the couch in parallel to an axis of rotation of an x-ray source of the computed tomography facility or corresponding to a longitudinal direction of the couch is used as the marker.
17 . The method of claim 16 , wherein at least one of
at least one of the marker element extends at least one of over an entire length of the couch or the marker element is integrated into the couch, or
at least one of at least three parallel marker elements are used adjacent thereto, and/or at different heights within the couch.
18 . The method of claim 16 , wherein the reference dataset is established showing only the at least one marker.
19 . The method of claim 18 , wherein, the comparison of the reference dataset with the target region image dataset includes,
establishing at least one comparison image with a recording geometry of an assigned projection image of the target region image dataset by forward projection from the reference dataset, and
comparing the at least one comparison image with the assigned projection image for a number of projection images of the target region image dataset showing at least one of the at least one marker.
20 . The method of claim 19 , wherein the comparison images and the projection images are highpass filtered before the comparison using an identical filter.