Computed tomography scanner with improved data transmission

Abstract

A gantry of a computed tomography scanner is rotated relative to a fixed base body of the computed tomography scanner. During rotation of the gantry, digital data is transmitted between the gantry and the base from the data source to the data receiver via the modulator, the transmission channel, and the demodulator. A transmission signal generated by a modulator by modulating a data stream fed from a data source to the modulator is pre-distorted by means of a pre-distortion device arranged upstream of the transmission channel according to a pre-distortion rule. Only the pre-distorted transmit signal is fed to the transmission channel. Alternatively or additionally, the signal transmitted via the transmission channel is post-distorted by means of a post-distortion device arranged downstream of the transmission channel according to a post-distortion rule, and only the post-distorted signal is fed to the demodulator. The pre-distortion rule and / or the post-distortion rule are repeatedly reset by the setting device during the stage rotation.

Description

Technical Field

[0001] The invention is based on a method for operating a computed tomography scanner.

[0002] - wherein the gantry of the computed tomography scanner is rotated relative to a fixed base body of the computed tomography scanner,

[0003] - wherein during the rotation of the gantry, digital data are transmitted between the gantry and the base body from a data source via a modulator, a transmission channel and a demodulator to a data receiver.

[0004] The invention is also based on a computer tomography scanner,

[0005] - wherein the computed tomography scanner has a fixed base body and a gantry which is rotatable relative to the fixed base body,

[0006] - wherein the computed tomography scanner has a data source, a modulator, a transmission channel, a demodulator and a data receiver, so that during the rotation of the gantry, digital data can be transmitted between the gantry and the substrate from the data source via the modulator, the transmission channel and the demodulator to the data receiver. Background Art

[0007] Computer tomography scanners are generally known.

[0008] In a computed tomography scanner, an X-ray source and an X-ray detector are arranged on a gantry, wherein the X-ray source emits X-ray radiation during the rotation of the gantry and the X-ray detector detects the emitted X-ray radiation. A three-dimensional image of the examination object (usually a person, in particular a patient) is reconstructed from the images of the examination object (usually a person, in particular a patient) thus detected.

[0009] Applicants note that regardless of the grammatical gender of certain terms relating to individuals (such as, for example, the term "patient"), persons of both male and female identities are included.

[0010] The reconstruction of the three-dimensional image is carried out with the aid of an evaluation device which is arranged outside the gantry, for example even outside the examination room in which the computed tomography scanner is located. The image data detected by means of the X-ray detector must be transmitted to the evaluation device during the rotation of the gantry. This is usually carried out via a transmission channel, via which the digital data are supplied from a data source (for example a pre-evaluation device which slightly processes the data detected by the X-ray detector) to a modulator which modulates the digital data onto a carrier signal. The modulated carrier signal is supplied to a demodulator via the transmission channel. The demodulator demodulates the modulated carrier signal and supplies the received signal determined in this way to a data receiver. In this case, the data source and the modulator are arranged on the gantry, and the demodulator and the data receiver are arranged on a fixed substrate. The transmission channel thus forms a bridge between the gantry and the fixed substrate.

[0011] As computed tomography scanners continue to develop, the amount of data that must be transmitted from the data source to the data receiver continues to increase. Conventional types of data transmission devices are gradually reaching their limits. Therefore, attempts are being made to increase the data rate at which the data is transmitted.

[0012] In computed tomography scanners, the carrier signal is usually subjected to a relatively simple modulation, namely phase shift keying or amplitude shift keying. These modulation methods are relatively robust with respect to phase changes of the transmitted signal. On the other hand, the transmittable data density is relatively low. This is also called low spectral efficiency.

[0013] A modulation method, in particular quadrature amplitude modulation (QAM), which achieves a significantly higher data density (or has a higher spectral efficiency) is known in the prior art. Purely by way of example, reference can be made to the corresponding excerpt from the German Wikipedia, retrieved on August 21, 2023. With regard to quadrature amplitude modulation, there are different "spreading stages", usually referred to as M-QAM, where M denotes the number of possible values. M is usually a power of 2, often even an even power of 2. That is, the simplest "spreading stage" is 4-QAM. Other "spreading stages" are 16-QAM, 64-QAM and 256-QAM. Higher "spreading stages" are also known.

[0014] Quadrature amplitude modulation allows significantly higher data rates (with unchanged bandwidth of the transmission channel). However, quadrature amplitude modulation is very sensitive to phase changes of the transmitted signal. This is because the phase of the signal generated by the modulator must be known very clearly at the demodulator for correct demodulation. Even small phase shifts can cause the signal transmitted via the transmission channel to no longer be correctly demodulated.

[0015] (See, for example, the already mentioned entry in the German Wikipedia) It is known to post-distort the signal transmitted via the transmission channel according to a post-distortion rule by means of a post-distortion device arranged downstream of the transmission channel and to feed only the post-distorted signal to the demodulator. The post-distortion device is usually designed as a so-called matched filter. The transfer function of the filter is designed for the pulse shape formed by the modulator and allows very good interference suppression.

[0016] By using quadrature amplitude modulation for data transmission between the gantry and the base body, significantly higher data rates can be achieved than before. However, due to the fact that the data transmission is carried out during the rotation of the gantry, the required run time of the transmission signal fed by the modulator into the transmission channel changes during the data transmission until the transmission signal reaches the demodulator. However, the phase relationship between the modulator and the demodulator also changes as a result. Therefore, the prior art method approach of post-distorting the signal transmitted via the transmission channel in a matched filter cannot easily achieve the desired success. Summary of the invention

[0017] The object of the present invention is to provide a possibility by means of which the data rate in data transmission between the stand and the stationary base body can be increased for a specific bandwidth of the transmission channel.

[0018] This object is achieved by an operating method according to the invention for a computed tomography scanner. Advantageous embodiments of the operating method are described below.

[0019] According to the invention, an operating method of the type mentioned at the outset is designed as follows:

[0020] - by means of a predistortion device arranged upstream of the transmission channel, a transmission signal generated by a modulator by modulating a data stream supplied from a data source to the modulator is predistorted according to a predistortion rule, and only the predistorted transmission signal is supplied to the transmission channel, and / or by means of a postdistortion device arranged downstream of the transmission channel, a signal transmitted via the transmission channel is post-distorted according to a postdistortion rule, and only the post-distorted signal is supplied to the demodulator, and - the predistortion rule and / or the postdistortion rule are repeatedly reset by the setting device during the rotation of the gantry.

[0021] Distortions of the transmitted signal caused by the transfer function of the transmission channel can be compensated by predistortion, postdistortion or (particularly preferably) a combination of predistortion and postdistortion. As a result, a signal which is almost undistorted in the result can be supplied to the demodulator, so that a high-quality, almost distortion-free reconstruction of the actual data signal can be performed. That is, matched filtering is performed in a matched filter. In this regard, the method approach initially corresponds to the method approach used in the prior art for orthogonal amplitude modulation. However, in order to compensate for changes in the running time during the rotation of the gantry, the predistortion rules and / or the postdistortion rules are additionally tracked more or less continuously. As a result, the quality of the data transmission can be maintained even during the rotation of the gantry.

[0022] Preferably, the data source supplies the data stream as a complex signal to the modulator, and the modulator determines the transmission signal according to the supplied complex signal by quadrature amplitude modulation of the carrier signal. This makes it possible to maximize the data rate during data transmission. In particular, the present invention shows its full advantages with the aid of quadrature amplitude modulation.

[0023] Preferably, the pre-distortion rule and / or the post-distortion rule is a parameterizable FIR filter (FIR=Finite Impulse Response), which can be parameterized reliably, robustly and simply, and can also be parameterized dynamically.

[0024] Preferably, the setting device determines the pre-distortion rule and / or the post-distortion rule according to the corresponding rotation angle of the stage.

[0025] Preferably, the setting device takes into account at least one time derivative of the rotation angle in addition to the corresponding rotation angle during the determination of the pre-distortion rule and / or the post-distortion rule.

[0026] The time derivative can in particular be a first time derivative (i.e. a rotational speed) and / or a second time derivative (i.e. a rotational acceleration). In particular, the time derivative is taken into account with correct sign. For example, by taking into account the time derivative of the rotation angle, a time delay between detecting or determining the corresponding rotation angle and tracking the pre-distortion rule and / or the post-distortion rule can be compensated.

[0027] It is possible to measure the rotation angle in each case, that is to say to base the tracking of the predistortion rule and / or the postdistortion rule on the measured rotation angle in each case. In this case, it is also possible to additionally also take into account at least one time derivative of the rotation angle in the process of determining the predistortion rule and / or the postdistortion rule.

[0028] Alternatively, it is possible to measure the rotation angle only in predetermined angular positions, for example only every 120°, every 180° or even only once per complete revolution of the gantry. In this case, between the predetermined angular positions, the rotation angle is determined by the setting device based on operating data of the gantry that characterize the rotation of the gantry, in particular the rotation speed and / or the rotational acceleration, by updating the last measured rotation angle.

[0029] Preferably, in the setting device, parameters for parameterizing the predistortion device and / or the postdistortion device are respectively stored in a lookup table for a plurality of input variables, and the setting device determines the parameters using the lookup table.

[0030] For example, for a plurality of grid points of the rotation angle, the lookup table contains the associated parameters for parameterizing the predistortion device and / or the postdistortion device. If the corresponding rotation angle coincides with a grid point, the parameters stored for the grid point are used. If the corresponding rotation angle does not coincide with any of the grid points, the parameters for the corresponding rotation angle can be determined, for example, by linear interpolation of the parameters stored for the nearest grid point. If the lookup table is not one-dimensional (using only the rotation angle), but multi-dimensional (also using the rotation speed, etc.), a similar approach is possible.

[0031] Preferably, the data stream comprises a plurality of data groups, wherein the data groups respectively comprise a reference sequence and a useful sequence. In this case, the signal transmitted via the transmission channel comprises a reference component and an effective component. In this case, the reference component is fed to a setting device, and the setting device determines a post-distortion rule for a useful component following the corresponding reference component according to the corresponding reference component. The background of the method approach is that the reference sequence can be known in advance for the setting device, so that it can be known for the setting device that the reconstructed sequence generated after post-distortion and demodulation may have to be consistent with the reference sequence. Therefore, the setting device can track the post-distortion rule so that the reconstructed sequence is as consistent as possible with the reference sequence, and in order to post-distort the effective component of the corresponding data group, the post-distortion rule that is tracked accordingly is used. The transmitted signal can be a transmitted signal that has been post-distorted or a transmitted signal that has not yet been post-distorted and can also be data derived from the signal.

[0032] The object is also achieved by a computed tomography scanner according to the invention. Advantageous embodiments of the computed tomography scanner are described below.

[0033] According to the invention, a computed tomography scanner of the type mentioned at the outset is designed as follows:

[0034] - a predistortion device is arranged upstream of the transmission channel, by means of which a transmission signal generated by a modulator by modulating a data stream supplied to the modulator from a data source is predistorted according to a predistortion rule, so that only the predistorted transmission signal is supplied to the transmission channel, and / or a postdistortion device is arranged downstream of the transmission channel, by means of which a signal transmitted via the transmission channel is postdistorted according to a postdistortion rule, so that only the postdistorted signal is supplied to the demodulator, and

[0035] The computer tomography scanner has a setting device, by which the pre-distortion rule and / or the post-distortion rule are repeatedly reset during a rotation of the gantry.

[0036] The facts and advantages resulting from this correspond to those of the operating method according to the invention.

[0037] The advantageous embodiments of the computed tomography scanner correspond to the advantageous embodiments of the operating method, and the same applies to the advantages resulting therefrom. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The characteristics, features and advantages of the present invention described above and the manner and method of achieving these characteristics, features and advantages become clearer and easier to understand in conjunction with the following description of an embodiment, which is explained in detail in conjunction with the accompanying drawings. In this case, it is shown in a schematic diagram:

[0039] Figure 1 shows a computed tomography scanner,

[0040] Figure 2 Showing a time diagram,

[0041] Figure 3 Another time diagram is shown,

[0042] Figure 4 shows the data transmission structure,

[0043] Figure 5 shows the communication path,

[0044] Figure 6 Showing the flow chart,

[0045] Figure 7 The setting device is shown.

[0046] Figure 8 shows the data source and modulator,

[0047] Fig. 9 shows the demodulator and data receiver,

[0048] Fig.10 Showing the data flow,

[0049] Fig.11 shows the transmitted signal, and

[0050] Fig.12 A flow chart is shown. DETAILED DESCRIPTION

[0051] according to Figure 1 The computed tomography scanner 1 has a fixed base body 2. The gantry 3 is rotatably supported on the base body 2, so that the gantry 3 can rotate relative to the base body 2 about a rotation axis 4. The rotatability is Figure 15 is indicated in the figure. The gantry 3 carries an X-ray source 6 and an X-ray detector 7, as is usually the case. The X-ray source 6 and the X-ray detector 7 are arranged diagonally opposite one another with respect to the rotation axis 4. In some cases, the gantry 3 also additionally carries a further X-ray source 8 and a further X-ray detector 9. The further X-ray source 8 and the further X-ray detector 9 are also arranged diagonally opposite one another with respect to the rotation axis 4. The further X-ray source 8 and the further X-ray detector 9 (if present) are usually arranged offset by 90° with respect to the first-mentioned X-ray source 6 and the first-mentioned X-ray detector 7, as viewed in the circumferential direction around the rotation axis 4. During the rotation of the gantry 3 about the rotation axis 4, an X-ray image of an examination object 10 arranged in the region of the rotation axis 4 can be detected by means of the X-ray detector 7 or the X-ray detectors 7, 9.

[0052] Figure 2 The rotation of the gantry 3 is shown as a function of the time point t. Figure 2 , the rotation of the gantry 3 starts at time t1 to detect an X-ray image of the inspection object 10. Specifically, the gantry 3 accelerates from time t1 to time t2, so that the rotation speed ω reaches a maximum value at time t2. Subsequently, the gantry 3 rotates at the maximum rotation speed until time t3, and finally brakes again until the gantry reaches a stationary state at time t4.

[0053] The X-ray image is acquired at least between time t2 and time t3, usually even from time t1 up to time t4. Figure 3 More or less simultaneously with the detection of the X-ray image, the X-ray image is also transmitted from the gantry 3 to the base body 2 . Figure 3 The solid lines show time periods during which at least data transmission takes place, and the dashed lines show time periods during which data transmission is also possible. The transmitted data are digital.

[0054] Figure 4 The structure for transmitting data between the stage 3 and the base body 2 is shown in simplified form.

[0055] according to Figure 4 , there is a data source 11. The data source 11 can be, for example, a unit which receives images from the X-ray detectors 7, 9 and (slightly) processes them. The data source 11 is connected to a plurality of modulators 12. There is at least one modulator 12. There are currently three modulators 12. The modulators 12 convert the transmission signals SS' (see Figure 5 ) is fed into the transmission channel 17 (see also Figure 5) in a section 13 on the gantry side. The sections 13 each extend over a range of (approximately) 360° / n, where n is the number of modulators 12. The section 13 on the gantry side can be configured, for example, as a waveguide or a dielectric conductor. On the fixed substrate 2 side, coupling elements 14 are coupled to the section 13 on the gantry side. The coupling elements 14 are usually evenly distributed on the circumference. The number of coupling elements 14 is usually one greater than the number of modulators 12. The signal is transmitted from the coupling element 14 to the demodulator 15 and from there to the data receiver 16. There is usually a 1:1 relationship between the coupling element 14 and the demodulator 15. The sections from one of the modulators 12 to one of the demodulators 15 each form a transmission channel 17.

[0056] In the above, data transmission is explained in conjunction with the transmission of data from the gantry 3 to the base body 2. In principle, however, data transmission can also take place in the opposite direction. In addition, the section 13 can also be arranged on the side of the base body 2 in the opposite direction, and the coupling element 14 can be arranged on the side of the gantry 3.

[0057] Combined with Figure 5 The communication path from the data source 11 to the data receiver 16 is explained again for a single transmission path.

[0058] according to Figure 5 , data is transmitted in the form of a data stream DS from a data source 11 via a modulator 12, an associated transmission channel 17 and a demodulator in a demodulator 15 to a data receiver 16. Data transmission (see Figure 2 and Figure 3 ) is performed during the rotation of the gantry 3. Specifically, the data source 11 transmits the data stream DS to the corresponding modulator 12. The modulator 12 modulates the carrier signal CS according to the data stream DS. The modulated carrier signal corresponds to the transmission signal SS, and the modulator 12 should start to feed the transmission signal SS into the transmission channel 17. However, the transmission signal SS is first supplied to the predistortion device 18. The predistortion device 18 is parameterized by means of the parameter PV. The predistortion rule is determined by parameterizing the predistortion device 18 by means of the parameter PV, and the predistortion device 18 predistorts the transmission signal SS according to the predistortion rule. The predistorted transmission signal (hereinafter provided with the reference numeral SS' to distinguish it from the original transmission signal SS) is only supplied to the transmission channel 17, and is thus fed into the transmission channel 17. As a result, the predistortion device 18 is therefore arranged upstream of the transmission channel 17.

[0059] The signal SS' fed into the transmission channel 17 is transmitted via the transmission channel 17. This signal is referred to below as the transmitted signal and is provided with the reference numeral TS. After transmission, the transmitted signal TS is supplied to a post-distortion device 19. The post-distortion device 19 is parameterized by the parameter PN. The parameterization of the post-distortion device 19 by the parameter PN determines a prescribed post-distortion rule according to which the post-distortion device 19 post-distorts the transmitted signal TS. The post-distorted transmitted signal (which is subsequently provided with the reference numeral TS' to distinguish it from the transmitted signal TS) is only supplied to the demodulator 15. As a result, the post-distortion device 19 is therefore arranged downstream of the transmission channel 17.

[0060] The demodulator 15 demodulates the post-distorted transmitted signal TS, thereby generating a transmitted data stream DS′. The transmitted data stream DS is supplied to a data receiver 16 .

[0061] As from Figure 4 As can be seen in the figure, the area where the corresponding segment 13 is coupled, at which the respectively adjacent coupling element 14 is coupled to the corresponding segment 13, continuously changes during the rotation of the gantry 3. Therefore, the effective length of the transmission channel 17 continuously changes during the rotation of the gantry 3. Therefore, the transmission characteristics of the transmission channel 17 also change. In order to keep the transmission characteristics of the transmission channel 17, the pre-distortion device 18 and the post-distortion device 19 as a whole constant or at least substantially constant, there is a setting device 20. During the rotation of the gantry 3, the setting device 20 repeatedly resets the pre-distortion rule and / or the post-distortion rule by presetting the corresponding parameters PV, PN. This will be described in conjunction with the following. Figure 6 Elaborate in detail.

[0062] according to Figure 6 , the setting device 20 knows the corresponding rotation angle φ of the gantry 3 in step S1. It is possible to detect the rotation angle φ in terms of measurement, that is, to measure the rotation angle φ, and to supply the corresponding measured value φ to the setting device 20. Alternatively, it is possible to directly or indirectly measure the associated rotation angle φ only in predetermined angular positions of the gantry 3 (for example, when passing through a reference position in each case), and to update the last measured rotation angle φ between the predetermined angular positions. In particular, the updating can be carried out based on operating data ω, α of the gantry (3) that characterize the rotation of the gantry 3, for example, based on the rotation speed ω and / or the rotational acceleration α.

[0063] In step S2, the setting device 20 determines the parameters PV, PN for the pre-distortion device 18 and the post-distortion device 19. The determination is performed according to the corresponding rotation angle φ. Figure 6As indicated in , at least one time derivative of the rotation angle φ, in particular a first time derivative, namely the rotation speed ω, and optionally also a second time derivative, namely the rotation acceleration α, can also be taken into account.

[0064] In step S3, the setting device 20 outputs the parameters PV and PN determined in step S2 to the pre-distortion device 18 and the post-distortion device 19. The corresponding distortion rules are thereby reset.

[0065] The setting device 20 then returns to step S1 , so that it thus continuously and repeatedly implements steps S1 to S3 .

[0066] The above description is simplified to a certain extent. Therefore, it is not necessary to carry out step S1 again immediately after step S3. In many cases, it is sufficient to keep the corresponding determination of the parameters PV, PN carried out in step S3 until a certain time has passed or the gantry 3 has continued to rotate by a certain angle.

[0067] The basic principle for determining the parameters PV, PN is explained below.

[0068] If the transfer functions of the transmission channel 17, the predistortion device 18 and the postdistortion device 19 are represented by H, U and V, then H'=UHV always applies, where H' is the resulting transfer function of the predistortion device 18, the transmission channel 17 and the postdistortion device 19. Ideally, the relationship H'=I should continue to apply, where I is the unity transfer function.

[0069] Due to the rotation of the gantry 3, the transfer function H of the transmission channel 17 is variable in time. That is, the parameters PV, PN, which are used to parameterize the predistortion device 18 and the postdistortion device 19 and thus determine the corresponding distortion rules and thus their transfer functions U, V, should be determined at any time so that the mentioned relationship H'=I applies exactly or at least approximately.

[0070] Depending on the situation, it is sufficient if only the predistortion device 18 or only the postdistortion device 19 is present or if both distortion devices 18, 19 are present but the parameters PV, PN of only one of the two distortion devices 18, 19 are repeatedly reset. However, it is generally preferred that both the predistortion device 18 and the postdistortion device 19 are present and the parameters PV, PN of both distortion devices 18, 19 are also repeatedly reset.

[0071] The design of the pre-distortion device 18 and the post-distortion device 19 can be carried out as required. In many cases, according to Figure 5, the two distortion devices 18, 19 are designed as parameterizable FIR filters, or in the case of only one distortion device 18 or 19, the existing distortion device 18, 19 is designed as a parameterizable FIR filter. The parameterization of the corresponding filter is produced by the corresponding parameters PV, PN. As a result, the pre-distortion rule and / or the post-distortion rule is therefore preferably a parameterizable FIR filter.

[0072] The design of the setting device 20 can also be carried out as required. Thus, for example, it is feasible that the setting device 20 uses the rotation angle φ (optionally additionally using the rotation speed ω and / or the rotation acceleration α) to determine the parameters PV, PN in a calculation manner. However, as described below in conjunction with Figure 7 The described design is significantly simpler.

[0073] according to Figure 7 , the setting device 20 has a lookup table 21. In the lookup table 21, parameters for parameterizing the predistortion device 18 and / or the postdistortion device 19 are stored for a plurality of input variables. In the simplest case, the only input variable of the lookup table 21 is the rotation angle φ. In this one-dimensional case, for example, for values ​​from 0° to 360°, the associated parameters PV, PN for the two distortion devices 18, 19 can be stored in a 2° grid. The grid size can of course also be finer or coarser. In the case of a plurality of input variables (for example, the rotation angle φ and the angular velocity ω), the lookup table 21 is multidimensional. In this case, a similar embodiment applies to the angular velocity ω. This also applies when the lookup table 21 is expanded with the angular acceleration α (optionally additional) as a further input variable. In the case of the lookup table 21, the setting device 20 can use the lookup table 21 to determine the parameters PV, PN. The manner and method of using the lookup table 21 are generally known and do not need to be explained in detail.

[0074] according to Figure 8 , the data source 11 preferably supplies the data stream DS as a complex signal to the modulator 12. Therefore, the data stream DS includes two sub-signals DS1 and DS2 representing the real part and the imaginary part of the complex signal, respectively. In this case, the modulator 12 is configured as an orthogonal amplitude modulator. The modulator includes two multipliers 22, to which the cosine and sine of the carrier signal CS are supplied. In addition, one sub-signal of each of the two sub-signals DS1 and DS2 is supplied to the two multipliers 22. The signals generated by the two multipliers 22 are supplied to the adder 23, which adds the two signals to form a transmission signal SS.

[0075] according to Fig. 9, in the case of quadrature amplitude modulation, the demodulator 15 and the data receiver 16 are also constructed accordingly. In particular, in this case, the demodulator 15 includes two multipliers 24, to which the cosine and sine of the post-distorted transmitted signal TS' and another carrier signal CS' having the same frequency as the carrier signal CS are supplied. The two multipliers 24 provide the real part DS1' and the imaginary part DS2' of the demodulated signal DS' as output signals, and the real part DS1' and the imaginary part DS2' are superimposed with the corresponding high-frequency components. The corresponding high-frequency components are filtered out in the corresponding low-pass filter 25, so that the real part DS1' and the imaginary part DS2' of the demodulated signal DS' are provided at the output end of the corresponding low-pass filter 25. The two sub-signals DS1', DS2' are supplied to the data receiver 16.

[0076] For correct demodulation, the phase of the further carrier signal CS' must match the phase of the carrier signal CS. In particular, this phase matching is brought about by the dynamic setting of the two distortion devices 18, 19 and their distortion functions.

[0077] according to Fig.10 , the data stream DS can include a plurality of data groups 26. This also and in particular applies when the data stream DS is a complex data stream. The data groups 26 each include a reference sequence 27 and a useful sequence 28. The reference sequence 27 is fixed in advance. That is, the content of the reference sequence is known not only to the data source 11 but also to the data receiver 16. The useful sequence 28 contains the useful data to be actually transmitted, i.e., data of an X-ray image, for example. The data groups 26 are transmitted sequentially one after another, wherein the corresponding reference sequence 27 is transmitted first and then the corresponding useful sequence 28.

[0078] According to the sequence and structure of the data groups 26 of the data stream DS, according to Fig.11 The signal TS transmitted via the transmission channel 17 comprises sections 29, which each comprise a reference component 30 and a useful component 31. The sections 29 each correspond to a data set 26, the reference component 30 to a respectively associated reference sequence 27, and the useful component 31 to a respectively associated useful sequence 28. The same applies to the post-distorted transmitted signal TS' (which is not shown expressly).

[0079] according to Fig.11 In the diagram in FIG. 1 , the reference component 30 can be fed to the setting device 20. In this case, the parameterization explained above of the post-distortion device 19 (instead of the pre-distortion device 18) can be combined with Fig.12 Modification as described.

[0080] according to Fig.12In step S11, the corresponding rotation angle φ of the stage 3 is known to the setting device 20. In step S12, the setting device 20 determines the parameters PV and PN for the pre-distortion device 18 and the post-distortion device 19. In step S13, the setting device 20 outputs the determined parameters PV and PN to the pre-distortion device 18 and the post-distortion device 19. Steps S11 to S13 are similar to Figure 6 Steps S1 to S3 of the embodiment correspond to each other in a 1:1 manner. Therefore, reference is made to the corresponding embodiment.

[0081] In step S14, the setting device 20 receives the corresponding reference component 30. In step S15, the setting device 20 determines the associated reconstructed sequence 32 by demodulating the reference component 30. In step S16, the setting device 20 corrects the parameter PN for the post-distortion device 19. The correction is carried out with the following purpose: to make the reconstructed sequence 32 as close as possible to the reference sequence 27, and in the ideal case completely consistent with it. If necessary, steps S15 and S16 can be iteratively implemented until the parameter PN is completely optimized or at least optimized to a sufficient extent. In step S17, the setting device 20 outputs the corrected parameter PN to the post-distortion device 19. As a result, steps S14 to S17 thus cause the setting device 20 to track the post-distortion rule according to the corresponding reference component 30. According to the post-distortion rule corrected in this way, the associated useful component 31 is demodulated by means of the demodulator 15.

[0082] In step S18, the setting device 20 checks whether it is necessary to redefine the parameter PV for the predistortion device 18. The check can include, for example, the time course or sweep of a certain angle range or the exceeding of a predetermined angle. If the check in step S18 shows that it is not necessary to redefine the parameter PV for the predistortion device 18, the setting device 20 returns to step S14, so that it thus successively implements steps S14 to S17 a plurality of times. If, on the other hand, the check in step S18 shows that it is necessary to redefine the parameter PV for the predistortion device 18, the setting device 20 returns to step S11, so that steps S11 to S13 are implemented again.

[0083] Fig.12 The method approach is explained based on the transmitted signal TS, ie the transmitted signal which has not yet been post-distorted. However, it is also possible to perform the post-distorted transmitted signal TS′ Fig.12 In this case, step S15 can be omitted.

[0084] In summary, the present invention therefore relates to the following facts:

[0085] The gantry 3 of the computed tomography scanner rotates relative to the fixed base body 2 of the computed tomography scanner. During the rotation of the gantry 3, digital data are transmitted from a data source 11 to a data receiver 16 between the gantry 3 and the base body 2 via a modulator 12, a transmission channel 17 and a demodulator 15. The transmission signal SS generated by the modulator 12 by modulating a data stream DS supplied to the modulator 12 from the data source 11 is predistorted according to a predistortion rule by means of a predistortion device 18 arranged upstream of the transmission channel 17. Only the predistorted transmission signal SS' is supplied to the transmission channel 17. Alternatively or additionally, the signal TS transmitted via the transmission channel 17 is postdistorted according to a postdistortion rule by means of a postdistortion device 19 arranged downstream of the transmission channel 17, and only the postdistorted signal TS' is supplied to the demodulator 15. The predistortion rule and / or the postdistortion rule are repeatedly reset by a setting device 20 during the rotation of the gantry 3.

[0086] The invention has numerous advantages. In particular, it enables a relatively simple and nevertheless robust data transmission, by means of which high transmission rates in the multi-gigabit per second range can be achieved.

[0087] Although the details of the present invention have been described in detail through the preferred embodiments, the present invention is not limited to the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of protection of the present invention.

Claims

1. A method for operating a computer tomography scanner, - wherein the gantry (3) of the computed tomography scanner is rotated relative to a fixed base (2) of the computed tomography scanner, - wherein during the rotation of the gantry (3), digital data are transmitted between the gantry (3) and the base (2) from a data source (11) via a modulator (12), a transmission channel (17) and a demodulator (15) to a data receiver (16), - wherein a transmission signal (SS) generated by the modulator (12) by modulating a data stream (DS) supplied from the data source (11) to the modulator (12) is predistorted according to a predistortion rule by means of a predistortion device (18) arranged upstream of the transmission channel (17), and only the predistorted transmission signal (SS') is supplied to the transmission channel (17), and / or a signal (TS) transmitted via the transmission channel (17) is postdistorted according to a postdistortion rule by means of a postdistortion device (19) arranged downstream of the transmission channel (17), and only the postdistorted signal (TS') is supplied to the demodulator (15), and - wherein the pre-distortion rule and / or the post-distortion rule are repeatedly reset by a setting device (20) during the rotation of the gantry (3).

2. The operating method according to claim 1, It is characterized in that The data source (11) supplies the data stream (DS) as a complex signal to the modulator (12), and the modulator (12) determines the transmission signal (SS) by quadrature amplitude modulation of a carrier signal (CS) based on the complex signal supplied to the modulator.

3. The operating method according to claim 1 or 2, It is characterized in that The pre-distortion rule and / or the post-distortion rule is a parameterizable FIR filter.

4. The operating method according to claim 1, 2 or 3, It is characterized in that The setting device (20) determines the pre-distortion rule and / or the post-distortion rule according to the corresponding rotation angle (φ) of the stage (3).

5. The operating method according to claim 4, It is characterized in that The setting device (20) takes into account at least one time derivative of the rotation angle (φ) in addition to the corresponding rotation angle (φ) when determining the pre-distortion rule and / or the post-distortion rule.

6. The operating method according to claim 4 or 5, It is characterized in that The rotation angle (φ) is measured separately or only in predetermined angular positions, and the rotation angle (φ) is determined between the predetermined angular positions by updating the last measured rotation angle (φ) based on operating data (ω, α) of the gantry (3) characterizing the rotation of the gantry (3), in particular the rotation speed (ω) and / or the rotational acceleration (α).

7. The operating method according to any one of the preceding claims, It is characterized in that In the setting device (20), parameters for parameterizing the predistortion device (18) and / or the postdistortion device (19) are stored in a lookup table (21) for a plurality of input variables, and the setting device (20) determines the parameters using the lookup table (21).

8. The operating method according to any one of the preceding claims, It is characterized in that The data stream (DS) comprises a plurality of data groups (26), each of which comprises a reference sequence (27) and a useful sequence (28), so that a signal (TS, TS') transmitted via the transmission channel (17) comprises a reference component (30) and a useful component (31), the reference component (30) being supplied to the setting device (20), and the setting device (20) tracking the post-distortion rule for the useful component (31) following the corresponding reference component (30) according to the corresponding reference component (30).

9. A computer tomography scanner, - wherein the computed tomography scanner comprises a fixed base body (2) and a gantry (3) which can rotate relative to the fixed base body (2), - wherein the computed tomography scanner comprises a data source (11), a modulator (12), a transmission channel (17), a demodulator (15) and a data receiver (16), so that during the rotation of the gantry (3), digital data can be transmitted from the data source (11) via the modulator (12), the transmission channel (17) and the demodulator (15) to the data receiver (16) between the gantry (3) and the substrate (2), - wherein a predistortion device (18) is arranged upstream of the transmission channel (17), by means of which a transmission signal (SS) generated by the modulator (12) through modulation of a data stream (DS) supplied from the data source (11) to the modulator (12) is predistorted according to a predistortion rule, so that only the predistorted transmission signal (SS') is supplied to the transmission channel (17), and / or a postdistortion device (19) is arranged downstream of the transmission channel (17), by means of which a signal (TS) transmitted via the transmission channel (17) is postdistorted according to a postdistortion rule, so that only the postdistorted signal (TS') is supplied to the demodulator (15), and - wherein the computed tomography scanner has a setting device (20), and the pre-distortion rule and / or the post-distortion rule are repeatedly reset by the setting device (20) during the rotation of the gantry (3).

10. The computer tomography scanner according to claim 9, It is characterized in that The modulator (12) is designed as a quadrature amplitude modulator which determines the transmission signal (SS) by means of quadrature amplitude modulation as a function of a complex signal supplied to it by the data source (11).

11. The computer tomography scanner according to claim 9 or 10, It is characterized in that The predistortion device (18) and / or the postdistortion device (19) are designed as parameterizable FIR filters.

12. The computer tomography scanner according to claim 9, 10 or 11, It is characterized in that The setting device (20) determines the pre-distortion rule and / or the post-distortion rule according to the corresponding rotation angle (φ) of the stage (3).

13. The computer tomography scanner according to claim 12, It is characterized in that The setting device (20) takes into account at least one time derivative of the rotation angle (φ) in addition to the corresponding rotation angle (φ) when determining the pre-distortion rule and / or the post-distortion rule.

14. The computer tomography scanner according to any one of claims 9 to 13, It is characterized in that The setting device (20) has a lookup table (21), in which parameters for parameterizing the predistortion device (18) and / or the postdistortion device (19) are stored for a plurality of input variables, and the setting device (20) determines the parameters using the lookup table (21).

15. The computer tomography scanner according to any one of claims 9 to 14, It is characterized in that The data stream (DS) comprises a plurality of data groups (26), each of which comprises a reference sequence (27) and a useful sequence (28), so that a signal (TS, TS') transmitted via the transmission channel (17) comprises a reference component (30) and a useful component (31), the reference component (30) being supplied to the setting device (20), and the setting device (20) tracking the post-distortion rule for the useful component (31) following the corresponding reference component (30) according to the corresponding reference component (30).

Images