METHOD FOR OPERATING AN X-RAY DEVICE

Abstract

A method and device for operating an x-ray device including an x-ray emitter and an x-ray detector are provided. An alternating magnetic field is produced and emitted at the x-ray emitter. At least two sensors are included for capturing at least one physical variable correlating with the alternating magnetic field. An alignment of the x-ray detector relative to the x-ray emitter is determined based on the measurement.

Claims

1. A method for operating an x-ray device, the x-ray device including an x-ray emitter and an x-ray detector, the method comprising: generating and emitting an alternating magnetic field by the x-ray emitter; measuring, by at least two sensors, at least one physical variable that correlates with the alternating magnetic field; and determining an orientation of the x-ray emitter relative to the x-ray detector based on the measurement.

2. The method of claim 1, wherein the at least one physical variable includes a magnetic field strength.

3. The method of claim 1, wherein the determining comprises: calculating a translation, a rotation, or a translation and rotation in at least one plane.

4. The method of claim 1, wherein the emitting comprises operating at least two transmitters for emitting the alternating magnetic field and arranged symmetrically with respect to one another, operating the at least two sensors, which are arranged symmetrically with respect to one another, or a combination thereof, wherein the measuring comprises measuring such that a ratio of the at least one physical variable as received by the at least two sensors is formed, and wherein the determining comprises determining the orientation of the x-ray emitter based on the ratio.

5. The method of claim 1, wherein the at least two sensors include at least four sensors arranged on the x-ray detector, wherein the measuring comprises ascertaining a position estimate, the ascertaining comprising relating physical variables received at a current time to a reference variable, and wherein the determining is based on the position estimate.

6. The method of claim 1, wherein the at least two sensors include at least one pair of sensors that are operated arranged orthogonal with respect to one another on the x-ray detector, wherein the measuring comprises ascertaining an angle of incidence based on the at least one physical variable between the at least one pair of sensors, the ascertaining comprising applying trigonometric functions, and wherein the determining comprises determining the orientation of the x-ray emitter based on the angle of incidence.

7. The method of claim 6, wherein the trigonometric functions include the arctangent.

8. The method of claim 6, wherein when the at least one pair of sensors includes more than one pair of sensors, an angle of incidence is determined for each pair of sensors; wherein the method further comprises determining a mean value from the angles of incidence of the pairs of sensors, and wherein the determining comprises determining the orientation of the x-ray emitter based on the mean value.

9. The method of claim 1, wherein the alternating magnetic field is generated with a frequency in a range between 75 kHz and 150 kHz.

10. The method of claim 9, wherein the alternating magnetic field is generated with a frequency of 125 kHz.

11. The method of claim 4, wherein the at least two transmitters include one-dimensional coils, two-dimensional coils, three-dimensional coils, or any combination thereof.

12. The method of claim 1, wherein the at least two sensors comprise 3-axis acceleration sensors, 3-axis rotational speed sensors, or 3-axis acceleration sensors and 3-axis rotational speed sensors.

13. An x-ray device comprising: an x-ray emitter comprising one or more transmitters configured to produce and transmit an alternating magnetic field; and an x-ray detector comprising at least two sensors each configured to measure at least one physical variable correlating with the alternating magnetic field, wherein the x-ray detector is configured to determine an alignment of the x-ray detector relative to the x-ray emitter based on the measurement.

14. The x-ray device of claim 13, wherein the x-ray device is further configured to calculate a translation, a rotation, or a translation and rotation in at least one plane.

15. The x-ray device of claim 14, wherein the transmission of the alternating magnetic field comprises operation of at least two transmitters for emission of the alternating magnetic field, the at least two transmitters being arranged symmetrically with respect to one another, operation of the at least two sensors, which are arranged symmetrically with respect to one another, or a combination thereof, wherein the measurement comprises a measurement in which a ratio of the at least one physical variable as received by the at least two sensors is formed, and wherein the determination of the orientation of the x-ray emitter is based on the ratio.

16. The x-ray device of claim 13, wherein the at least two sensors include at least four sensors arranged on the x-ray detector, wherein the measurement comprises ascertainment of a position estimate, the ascertainment comprising relation of physical variables received at a current time to a reference variable, and wherein the determination of the alignment of the x-ray detector is based on the position estimate.

17. The x-ray device of claim 14, wherein the at least two sensors include at least one pair of sensors that are arranged orthogonal with respect to one another on the x-ray detector, wherein the measurement comprises ascertainment of an angle of incidence based on the at least one physical variable between the at least one pair of sensors, the ascertainment comprising application of trigonometric functions, and wherein the determination of the orientation of the x-ray emitter is based on the angle of incidence.

18. The x-ray device of claim 17, wherein when the at least one pair of sensors includes more than one pair of sensors, an angle of incidence is determined for each pair of sensors; wherein the x-ray detector is configured to determine a mean value from the angles of incidence of the pairs of sensors, and wherein the determination of the orientation of the x-ray emitter is based on the mean value.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0020] FIG. 1 depicts an x-ray device arrangement in accordance with the prior art.

[0021] FIG. 2 depicts an embodiment that highlights the application according to a spherical model as a measurement principle.

[0022] FIG. 3 depicts schematically an embodiment including a gradient model as a measurement principle.

[0023] FIG. 4 depicts a flowchart of an embodiment of operating an x-ray device.

DETAILED DESCRIPTION

[0024] FIG. 1 depicts, in a simplified manner, an x-ray device arrangement.

[0025] The x-ray device arrangement includes an emitter (e.g., an x-ray emitter) and a detector (e.g., an x-ray detector), between which a person to be examined is placed.

[0026] Depicted further is the way in which the orientation of the x-ray detector may change such that the x-ray detector has an offset in relation to the emitter that is immovable.

[0027] There may be a displacement of the detector in the xy-plane (e.g., a translation offset). The detector may also be effected such that the detector is rotated about one of the three xyz axes in space.

[0028] The orientation of the detector emerging may be determined manually and leads to disadvantages.

[0029] In an embodiment, the disadvantages are rectified by providing an automated capture of the offset.

[0030] The embodiment in FIG. 2 depicts the use of transmitters (denoted by the lines on the edge of the emitter) Tx1 . . . Tx4, that are placed on the emitter, and the use of receivers (symbolically depicted by “x” at the edge of the detector) Rx1 . . . Rx4. As depicted, the placement may be symmetric among the transmitters/receivers with respect to one another and may also be configured such that, for example, the receivers are attached orthogonally with respect to one another. Alternatively, use may also be made of more than 4 receivers Rx1 . . . Rx4.

[0031] The rotational angle and the position for the conceivable offset possibilities may be determined.

[0032] The transmitters produce an alternating magnetic field and the receivers are configured as coils. The received voltages are ascertained by at least two orthogonal reception coils. The angle of incidence between the two reception coils may be determined with the aid of the arctangent trigonometric function if linearly emitted magnetic fields are assumed. The mean value of the estimated rotational angle is determined in the case of a plurality of reception coil pairs. The orientation may be determined in general by trigonometric functions if three reception coils are used (e.g., there is no restriction to the arctangent). The accuracy of the estimate is dependent on: a homogeneous field distribution produced by the transmission coils, orthogonality of the reception coils (e.g., coupling, installation), and the signal-to-noise ratio.

[0033] A tilt or rotation in space (e.g., yaw, pitch, roll) about one axis only may be measured via two reception coils (Rx1, Rx2) that are crossed by 90°. The installation locations are on the main axes of the detector. Yaw reception coils lie in the x′y′-plane. Pitch reception coils lie in the x′z′-plane. Roll reception coils lie in the y′z′-plane. The estimated angle=a tan(measurement at Rx1/measurement at Rx2). In an embodiment, a 3D reception coil is used to capture a tilt about two axes. There is a calibration of the reception coils prior to an angle estimate.

[0034] An angle measurement using a trigonometric function may only be applicable in the case of a homogeneous phase in space.

[0035] The position of the detector in the given initial situation may be ascertained by the use of measurement principles, for example, a spherical model and a gradient model/gradient method. The spherical model includes estimating the position of the detector relative to the transmitter using a spherical model. The depicted four receivers are used for estimating the x, y, z position of the detector. The spherical model is based on an empirical model. The empirical model is based on measurements of the field strengths that are ascertained once in the case of relevant distances between transmitter and detector and in a relevant region in the case of a constant distance. A cost function for each receiver is minimized for each measured value.

[0036] The following equations describing/modeling the conditions of the x-ray arrangement are used in the spherical model:

r.sub.Rx1=√{square root over ((x+x.sub.1).sup.2+(y+y.sub.1).sub.2+(z+z.sub.1).sup.2)}

r.sub.Rx2=√{square root over ((x+x.sub.2).sup.2+(y+y.sub.2).sub.2+(z+z.sub.2).sup.2)}

r.sub.Rx3=√{square root over ((x+x.sub.3).sup.2+(y+y.sub.3).sub.2+(z+z.sub.3).sup.2)}

r.sub.Rx4=√{square root over ((x+x.sub.4).sup.2+(y+y.sub.4).sub.2+(z+z.sub.4).sup.2)}

[0037] The model equations for the four receivers are provided herewith. The Euler matrix M with

[00001]$\left(\begin{array}{c}{x}_n\\ y_n\\ z_n\end{array}\right)=M.Math.\left(\begin{array}{c}{x}_{\mathrm{Rxn}}\\ y_{\mathrm{Rxn}}\\ z_{\mathrm{Rxn}}\end{array}\right)$

[0038] is provided for a receiver with an offset from the center point of the detector and with xn, yn, zn, depending on the spatial angles yaw α, roll β, and pitch γ. In the case of a rotation about the z-axis, as depicted in the figure (with a value of the angle α=45°), the matrix would emerge as follows from which the rotational angle may be determined.

[00002]$M=\left(\begin{array}{ccc}\cos .Math..Math.\alpha & -\sin .Math..Math.a& 0\\ \sin .Math..Math.\alpha & \cos .Math..Math.\alpha & 0\\ 0& 0& 1\end{array}\right)$

[0039] The position (e.g., the displacement in accordance with the illustration by x=y=10 cm) of the detector from the center point with respect to all transmitters Txn is estimated from the reception voltages at all receivers Rxn.

[0040] For estimating the xy-translation by the spherical equation, the xy estimate is based on a polynomial. For the polynomial, the field distribution is not symmetrical, a polynomial determines the mean value of all curves, a radius is assigned with the aid of the polynomial of each measured reception voltage, and at least three reception coils are therefore sufficient for the estimation (e.g., because or if the z-distance is constant and known). An estimation error is minimized if further receivers are used. If the polynomials are used for the estimation, the error is suitable for relatively small displacements as measurement errors increase with increasingly large displacements. The estimation principle is also applicable for a rotation of the detector. The mean Euclidean distance may be 1.7 cm.

[0041] The accuracy achieved by one-dimensional reception coils is sufficient and offers an expedient solution. More accurate results may also be obtained by the use of two-dimensional or three-dimensional coils.

[0042] By contrast, the gradient method, as depicted in FIG. 3, indicated on the basis of an initial situation (e.g., a purely translational displacement) includes where the xy-displacement is determined by a gradient. The displacement may be determined via a reception ratio of a symmetrical transmission and reception configuration. The displacement is applicable if no rotation/tilt is present. The gradient may be valid for a distance. The principle that a displacement is present if two opposing receivers do not detect the same reception field strength is used. The mean Euclidean distance may be 0.3 cm.

[0043] Further, a suitable polynomial may be determined for the estimation in accordance with an embodiment, taking into account the following points.

[0044] The measured reception voltages depend on the position of the reception coils on the detector (e.g., Rx1 and Rx2 have a greater distance from the detector center than Rx3 and Rx4).

[0045] For a rough estimate of the distance, a polynomial that is based on the addition of the voltages from all reception coils is determined.

[0046] For estimating the distance accurately, a polynomial emerging from the voltages from reception coils having an identical distance from the center of the detector may be determined.

[0047] The corresponding polynomial is assigned to each reception coil depending on the position thereof on the detector plate. The assignment provides a good correlation of radii to reception voltages at various distances.

[0048] Since a spherical equation may also be established by a polynomial for each receiver in accordance with an alternative embodiment, there may also be an estimate by the spherical model, where the z-component may be estimated very well if the estimated x- and y-components correspond to 0.

[0049] FIG. 4 depicts a flowchart of an embodiment. At act 51, an initial state “start” is followed by a calibration in act S2. The calibration ascertains a voltage and angle offset as a result in act S3 by virtue of a measurement carried out at a defined position of the transmitter and of the detector (e.g., such that the transmitter and detector are situated directly over one another. The reception voltage at each receiver and angles between the individual reception coils are determined.

[0050] Approximate positioning is then carried out in act S4. At act S5, the rotational angle is estimated.

[0051] At act S6, the spatial angles yaw/pitch/roll are output. At step S7, the detector is rotated to the zero position (e.g., with any translation).

[0052] The z-translation is estimated at act S8. The z-coordinate is outputted at act S9. A model is selected at act S10. The model is used in act S11 to estimate the xy-translation and carry out a displacement of the detector/transmitter to the zero position in act S12.

[0053] An evaluation is carried out at act S13 as to whether n-iterations have been reached. The method is completed in the affirmative and proceeds to the “stop” state in at act S14.

[0054] If n-iterations have not been reached, acts S5 . . . S11 are repeated.

[0055] The approach described in this document is not restricted to the examples explained. For example, the orientation of objects in space and the position thereof are accomplished with the aid of a selection of sensors, homogeneous in respect of type, from a selection, possible in principle, of a plurality of sensor types (e.g., acceleration sensor, gyro, etc.) that are used in a comparable way to the orientation control of aircraft, which is not in the art.

[0056] It is to be understood that the elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present invention. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims may, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent, and that such new combinations are to be understood as forming a part of the present specification.

[0057] While the present invention has been described above by reference to various embodiments, it may be understood that many changes and modifications may be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.