Method for ascertaining a time for a calibration, x-ray device and computer program

Patent metadata

Field	Value
Publication number	US-10499875-B2
Application number	US-201715430727-A
Country	US
Kind code	B2
Filing date	Feb 13, 2017
Priority date	Feb 12, 2016
Publication date	Dec 10, 2019
Grant date	Dec 10, 2019

Abstract

A method ascertains a time for a fresh calibration for ascertaining up-to-date calibration parameters of an x-ray device. The x-ray device has multiple degrees of freedom of movement for its recording arrangement. X-ray images of a calibration phantom are recorded for recording positions of the recording arrangement and are evaluated to ascertain the calibration parameters allowing ascertainment of geometry parameters. In multiple operating phases, situated between two calibrations, of a further x-ray device of identical design to the x-ray device, a piece of use information describing the accumulated use of the degrees of freedom of movement during the operating phase and a piece of difference information describing the difference in the calibration parameters between the calibrations delimiting the operating phase, is ascertained and used or determining the time for a fresh calibration.

First claim

The invention claimed is:

1. A method for ascertaining a time for a fresh calibration for ascertaining up-to-date calibration parameters of an x-ray device, the x-ray device having multiple degrees of freedom of movement for a recording configuration containing an x-ray emitter and an x-ray detector, which comprises the steps of:
recording x-ray images of a calibration phantom for at least some of possible recording positions of the recording configuration;
evaluating the x-ray images to ascertain calibration parameters allowing ascertainment of geometry parameters, describing a recording geometry, from position data of the recording configuration being based on the degrees of freedom of movement;
ascertaining in multiple operating phases, situated between two calibrations, of at least one further x-ray device of identical design to the x-ray device, a piece of use information containing use data describing an accumulated use of the degrees of freedom of movement during an operating phase and a piece of difference information describing a difference in the calibration parameters between the calibrations delimiting the operating phase; and
determining the time for the fresh calibration from a relationship, determined by collective evaluation of all the use information, between the use data and the difference information on a basis of the use data recorded since a last calibration.

2. The method according to claim 1 , which further comprises determining the time on the basis of the use information only when the use information is available for a number of the operating phases for the or all of the x-ray devices that exceeds a threshold value, wherein fixed intervals of time are used beforehand for spacing the calibrations.

3. The method according to claim 1 , which further comprises:
recording the use data in a manner resolved according to the degrees of freedom of movement and/or trajectories used for the recording configuration; and/or
ascertaining the difference information as a sum of absolute values of differences based on individual features of the calibration phantom.

4. The method according to claim 3 , wherein the use data used are a length of movement along each degree of freedom of movement, and/or the use data based on the trajectories are taken into consideration in a manner weighted with the length of movement along all the degrees of freedom of movement, and/or the trajectories have associated degrees of freedom of movement information, so that the use data based on the degrees of freedom of movement are derived from the use data based on the trajectories.

5. The method according to claim 1 , wherein a collection of the use information for multiple x-ray devices involves the use information being transmitted from the x-ray device recording it to a central computation device, where at least part of the evaluating is performed.

6. The method according to claim 1 , which further comprises updating the relationship whenever there is a new piece of use information available.

7. The method according to claim 1 , which further comprises ascertaining the relationship by virtue of training of a mathematical model described by at least one model parameter.

8. The method according to claim 7 , which further comprises ascertaining the relationship by virtue of a nonparametric multivariate adaptive regression splines method.

9. The method according to claim 1 , which further comprises ascertaining the time by using the relationship to ascertain a piece of predicted difference information from the use data recorded since a last calibration and evaluating the predicted difference information using a recalibration criterion.

10. The method according to claim 1 , wherein in a case of a piece of difference information being broken down according to different differences, a piece of predicted difference information ascertained by means of the relationship from the use data recorded since a last calibration is used for plausibilizing the relationship in an event of the fresh calibration and/or for preadaptation of the calibration parameters and/or restriction of a selection of positions and/or trajectories of the recording configuration before the fresh calibration, namely the fresh calibration shifted to a later time.

11. The method according to claim 1 , which further comprises ascertaining the relationship by virtue of training of a mathematical model described by at least one model parameter, namely by virtue of a fit process.

12. A control system for at least one x-ray device, the control system comprising:
a further x-ray device; and
a control device configured for performing a method for ascertaining a time for a fresh calibration for ascertaining up-to-date calibration parameters of the x-ray device, the x-ray device having multiple degrees of freedom of movement for a recording configuration containing an x-ray emitter and an x-ray detector, the method comprises the steps of:
recording x-ray images of a calibration phantom for at least some of possible recording positions of the recording configuration;
evaluating the x-ray images to ascertain calibration parameters allowing ascertainment of geometry parameters, describing a recording geometry, from position data of the recording configuration being based on the degrees of freedom of movement;
ascertaining in multiple operating phases, situated between two calibrations, of the at least one further x-ray device of identical design to the x-ray device, a piece of use information containing use data describing an accumulated use of the degrees of freedom of movement during an operating phase and a piece of difference information describing a difference in the calibration parameters between the calibrations delimiting the operating phase; and
determining the time for the fresh calibration from a relationship, determined by collective evaluation of all the use information, between the use data and the difference information on a basis of the use data recorded since a last calibration.

13. A non-transitory computer medium carrying computer executable instructions to be executed on a processor, the computer executable instructions programmed to perform a method according to claim 1 .

Assignees

• Siemens Healthcare Gmbh

Inventors

• Fieselmann Andreas
• Jerebko Anna

Classifications

• A61B6/584 Primary

  determining position of components of the apparatus or device using images of the phantom · CPC title

• A61B6/586

  Detection of faults or malfunction of the device · CPC title

• A61B6/4464

  the source unit or the detector unit being mounted to ceiling · CPC title

• A61B6/4458

  the source unit or the detector unit being attached to robotic arms · CPC title

• A61B6/0407

  Supports, e.g. tables or beds, for the body or parts of the body · CPC title