DE102011076053B4 - Method for operating an X-ray image recording device and image recording device - Google Patents

Abstract

Method for operating an X-ray image recording device which comprises at least two recording arrangements comprising an X-ray source (1, 8) and an X-ray receiver (3, 10), wherein the X-ray receivers (3, 10) differ with respect to their gray value dynamics and / or their spatial resolution, wherein a first data record (14) of projection images of an object to be recorded is recorded using different projection directions with a first recording arrangement; and a second data record (16) of projection images of the object to be recorded using projection projections of the first object (14) of projection images using a different projection direction second recording arrangement is recorded, after which a reconstruction of a three-dimensional image data set (20) using a reconstruction data set (18) of projection images e. determined from the projection images of the first and the second data set (14, 16) is recorded and in which a projection image of the first data record (14) and a projection image of the second data record (16) which relate to the same projection directions are fused to form a projection image of the reconstruction data record (18), characterized in that an X-ray receiver having a lower gray value dynamic ( 10) of the second recording arrangement over-radiated areas in the projection images of the second data set (16) are determined, wherein the data lying in the over-radiated areas are replaced by data of the first data set (14), or that two projection direction corresponding projection images of the first and the second Data set (14, 16) are Fourier-transformed to determine the respective spatial frequency spectrum, wherein a target spectrum combined from the two spatial frequency spectra is determined and a projection image of the reconstruction data set (18) is determined by Fourier transformation into the spatial domain; wherein at a lower spatial resolution having X-ray receiver (3) of the first recording arrangement above the Nyquist frequency of the projection image of the first record (14) of the above this Nyquist frequency portion of the spatial frequency spectrum of the projection image of the second data set (16) is added.

Description

The invention relates to a method for operating an X-ray image recording device, which comprises at least two receiving arrangements comprising an X-ray emitter and an X-ray receiver, wherein the X-ray receivers differ with respect to their gray value dynamics and / or their spatial resolution and / or the size of their detection range. In addition, the invention relates to an X-ray image recording device comprising at least two receiving devices comprising an X-ray emitter and an X-ray receiver, wherein the X-ray receivers differ with respect to their gray value dynamics and / or their spatial resolution and / or the size of their detection range.

Computed Tomography (CT) is an imaging technique that allows an accurate three-dimensional representation of a body's internal structures. In this case, an excellent contrast resolution is given, which is due to the high number of images and especially the high gray value dynamics, for example, 16-20 bits, the single detectors of the CT X-ray receiver. In contrast, the spatial resolution of known CT X-ray receiver is very low, for example in the range of 0.4-0.5 mm. Responsible for this is the size of the individual detectors, which form the X-ray receiver. A review of computed tomography (CT) can be found, for example, in the article by Willi A. Kalender, "X-ray computed tomography", Phys. Med. Biol. 51 (2006), pages R29 to R43.

CT-like images can also be performed with so-called flat-plate detectors. This method is known as a flat detector computed tomography or DynaCT ^®. The procedure used for this purpose has been described, for example, in an article by Willi A. Kalender and Yiannis Kyriakou, Flat-detector Computed Tomography FD-CT), Eur Radial (2007) 17, pages 2767 to 2779. Flat-panel detectors were developed for use in radiography and fluoroscopy and have a significantly better spatial resolution than CT X-ray receiver, for example, a spatial resolution down to 0.2 mm. In this case, however, the contrast resolution is limited, so that flat panel detectors have a much lower gray scale dynamics, for example 12-14 bits. Disadvantageously, so-called capping artifacts (often also cupping artifacts) can occur, which have their cause in areas of maximum gray values at which higher values would have occurred, but which can not be mapped due to the low gray value dynamics. In addition, the number of images available for reconstruction is usually limited and flat-panel detectors can not be realized with the same large coverage area as CT X-ray receivers, so that truncation of the object to be recorded can occur.

Meanwhile, hybrid systems have been proposed which include both a flat panel detector and a CT X-ray receiver. That's how it is DE 198 02 405 A1 an X-ray diagnostic device with a computed tomography known in addition to a mounted on a turntable first X-ray tube with an associated radiation receiver (CT X-ray receiver), which consists of a series of single detectors, each of which forms an electrical signal corresponding to the received radiation intensity, also on the Turntack arranged second X-ray tube, which in turn is associated with an X-ray receiver, in this case, a matrix-shaped X-ray detector (flat detector), wherein the two correspondingly formed receiving arrangements are at a right angle to each other. The flat detector used there may be, for example, a solid state image converter made of amorphous silicon. This embodiment should make it possible to create X-ray overview images simultaneously with the acquisition of the measured values for creating the slice images. At the same time, biplane operation and x-ray stereo operation are proposed.

From the publication US 2009/0060121 A1 is a computed tomography with two detectors known. The detectors have different spatial resolutions and sizes. For the image reconstruction their image data are combined.

From the publication DE 103 02 565 A1 is a tomograph with two imaging systems known. The image systems have different sizes or can be set to different sizes.

From the publication US 2003/0076920 A1 is a computer tomograph with two imaging systems known. If errors occur in either image system, image acquisition continues using the other image system.

From the publication US 2009/0207968 A1 is a computer tomograph with two imaging systems known. From the images of each of the two image systems images are reconstructed, as well as a combination of the images of both image systems.

From the publication DE 100 34 846 A1 For example, a method of obtaining an image from a shot and a low-dose pre-shot is known. Usable image areas of the recording and pre-recording are identified and the respective complementary image areas hidden.

From the publication DE 10 2009 014 727 A1 For example, a method for image acquisition with two image systems is known. One of the image data sets as well as a combined image data set are generated with different fan angles. From the different image data sets a final image is reconstructed.

The invention has for its object to provide a contrast improved operating method and a contrast improved image pickup device.

To solve this problem, it is provided according to the invention in a method of the type mentioned that a first record of projection images of a male object is recorded using different projection directions with a first recording arrangement and a second, recorded with the first record of projection images record of projection images of the male Object is recorded using different projection devices with a second recording arrangement, after which a reconstruction of a three-dimensional image data set using a determined on the projection images of the first and second data set reconstruction data set of projection images, and wherein a projection image of the first data set and a projection image of the second data set, the same directions of projection, are fused to a projection image of the reconstruction data set. Areas in the projection images of the second data record which are overexposed to the second recording arrangement are detected, in particular by determining a constant maximum gray scale value, the data lying in the overexposed areas being replaced by data of the first data record, or two corresponding to the same projection direction Projection images of the first and second data sets for determining the respective spatial frequency spectrum are Fourier-transformed, whereby a target spectrum combined from the two spatial frequency spectra is determined and a projection image of the reconstruction data set is determined by Fourier transformation into the spatial domain. In the case of an X-ray receiver of the first recording arrangement having a lower spatial resolution above the Nyquist frequency of the projection image of the first data record, the portion of the spatial frequency spectrum of the projection image of the second data record lying above this Nyquist frequency is added.

Thus, according to the invention, a hybrid system, in particular a through DE 198 02 405 A1 described hybrid system, used as an image recording device, in which two recording arrangements with X-ray and X-ray receiver are mechanically coupled, so that recorded with the recording arrangements image data are already registered intrinsically with each other, which allows a combined evaluation or reconstruction. The basic idea of the present invention is thus to acquire, preferably in parallel or successively with both X-ray receivers in a hybrid system, data sets of projection images for a subsequent three-dimensional reconstruction and to use the raw data, that is to say the data of the projection images, for a joint reconstruction, that is According to the invention, the first and the second data set are fundamentally fused to a reconstruction data set of projection images prior to the final reconstruction. Thus, it is possible in a particularly elegant way to take advantage of different X-ray detectors to provide a common, improved reconstruction data set of projection images, thus allowing the reconstruction of higher-quality and more meaningful three-dimensional image data sets. For this purpose, the different information is already assembled at the level of the projection images, where this is low due to the already given registration due to the mechanical coupling in the image pickup device.

It should be noted at this point that according to the invention as a direction of projection, the direction of a central beam from the X-ray source to the X-ray receiver can be understood, for example, the direction of the beam exit point or center of the beam exit region of the X-ray source to the center of the recording area on the X-ray receiver when taking a projection image. Consequently, the different projection directions relate to different recording geometries, that is to say different positions of X-ray emitter and X-ray receiver relative to the object to be recorded.

The method according to the invention can be used particularly advantageously if the X-ray receiver of the first recording arrangement is a CT X-ray receiver consisting of individual detectors arranged in at least one detector row and X-ray receiver of the second recording arrangement is a flat detector (often matrix detector or solid-state detector) comprising several matrix-like arranged Detector elements, is used. It is, as already shown, usually so that the CT X-ray receiver has a lower resolution, a higher gray value dynamics and a larger detection range than the flat detector. In this case, the method according to the invention therefore aims to achieve the higher spatial resolution of the flat detector, which to utilize higher gray value dynamics of the CT X-ray receiver and the larger coverage area of the CT X-ray receiver by merging the first and second data sets on the projection image plane to obtain an improved reconstructed three-dimensional image data set. Although reference is frequently made in the following to the example presented here with a CT X-ray receiver and a flat detector, it should be noted that it is of course also possible to link other X-ray receivers with different, respectively advantageous properties in the method according to the invention for obtaining higher-quality three-dimensional image data sets.

In the described example with the CT X-ray receiver and the flat detector, therefore, a normal CT raw data set is recorded as the first data set of projection images in the method according to the invention. Parallel (or less preferably successively), a flat-detector CT data set is acquired as a second set of projection images.

In a further advantageous embodiment of the present invention can be provided that is limited at different coverage area of the X-ray receiver in the X-ray receiver with the larger detection range of the receiving area, in particular by collimation that it corresponds to the smaller detection range of the other X-ray receiver. Thus, if the receiving area of one X-ray receiver is so limited (collimated) that it corresponds to the detection area, and thus also to the receiving area, of the other X-ray receiver, the X-ray dose can advantageously be reduced when taking a patient.

A combination of information of the first and the second data set of projection images can be achieved in a particularly expedient manner when viewing projection images which were taken with the same projection direction, ie ultimately with identical viewing angles to the object to be recorded. In order to achieve that projection images exist in the two data sets which correspond in their direction of projection, the method according to the invention proposes two alternative possibilities in order to achieve this goal.

Thus, it can be provided in a first embodiment of the method according to the invention that the recording of the data sets of projection images takes place in such a way that in each case two individual projection images of different data sets are found, which are recorded in the same projection direction. This means that the operating parameters of the image recording device when recording the first and the second data set are adjusted such that a projection image inevitably exists for each recorded projection direction in the first and in the second data record. When recording projection images along a circular path of the X-ray source, this can be achieved, for example, in that the recording arrangements arranged in the plane of the circular path are rotated relative to one another at a fixed angle. This angle can be for example 90 °, as already by the DE 198 02 405 A1 is described. If a complete circular path then travels as a recording trajectory for recording the projection images, ie a 360 ° circulation, then, with a suitable choice of the recording positions in both data sets, X-ray images are available at the same projection directions.

A somewhat more complex case arises when a spiral trajectory of the X-ray source is to be used as the recording trajectory. Then, in a particularly advantageous embodiment of the present invention may be provided that when recording a spiral path, a combination of a circular path of the X-ray source and a feed of a patient table the image pickup device is used perpendicular to the circular path by a predetermined distance, wherein in the plane of the circular path arranged and rotated against each other at a fixed angle receiving arrangements of the beam exit point of at least one X-ray along the feed direction during recording by a constant, depending on the angle and the feed distance certain length is moved. According to the invention, in the case of a spiral path, it is therefore proposed to use X-ray sources in which the radiation exit point, specifically, for example, a focal spot on a rotary anode, can be changed, so that it can be changed along the feed direction of the patient table. The beam exit point or focal spot is therefore variable and is the feed distance (ie ultimately the "height" of the spiral, often as a "pitch") adjusted accordingly. Concretely, the length by which to shift so that the same recording trajectory exists for both sets of data is computable as the angle times the feed distance divided by 360 ° and 2π, respectively, so that at 90 °, ie π / 2, against each other twisted recording arrangements results in a quarter of the feed distance as a shift length.

In order to enable the displacement, it can be provided that at least one of the X-ray emitters is designed to be displaceable mechanically in the feed direction. However, it is preferred if the focal spot of an X-ray source is adjusted electronically, in particular by using magnetic fields. This can be done, for example, in a so-called rotary tube, as is often used in computed tomography done. Depending on the specific embodiment of the displaceability, therefore, at least one defined offset or else a continuous, variable adjustment possibility can be provided.

The first embodiment described has a high mechanical requirement on the adjustability and accuracy with respect to the two receiving arrangements, for example with respect to a beam exit point or focal spot in the feed direction result. This problem is avoided if the second, particularly advantageous, alternative embodiment of the method according to the invention is used, wherein, if at least one projection image of a projection direction of a data set no projection image of the same projection direction exists in the other data set, from the first set of projection images, a three-dimensional Vorabrekonstruktionsdatensatz is determined from the at least one intermediate data set of calculated projection images is determined by the forward projection in the occurring in the second set of projection images and not in the first set of projection images projection directions by which the first set of projection images is extended.

To avoid the described disadvantage of the adjustment requirements, it is proposed to first acquire the first and the second data set as usual. However, the recording geometries, specifically the recording trajectories, of the two data sets do not have to be coordinated in detail, that is, in particular the trajectories of the X-ray emitters, in particular the X-ray focal spots, of the two recording arrangements relative to the object to be recorded during recording can describe different paths. The projection images of one of the two recording arrangements of the hybrid system, for example those of the CT X-ray receiver or that of the flat detector, are converted by means of computational methods into the acquisition geometries of the respective other data set. Only with this computational transfer are now at least virtually the recording trajectories congruent so that then the fusion of the projection data can be done. In this case, the transfer of the geometry of a recording arrangement into the geometry of the other recording arrangement advantageously takes place in that initially a three-dimensional reconstruction of the one data set, in this case the first data set, for example, is performed for the preliminary reconstruction data set. In this way, as part of a forward projection, in particular by means of ray tracing methods, virtual projection images are generated in the projection directions that were previously missing in the first data record. Overall, therefore, differences in the recording geometries can be advantageously compensated for by computational methods.

It should also be noted at this point that it is advantageous, in particular in the case of computational conversion of the second alternative of the invention, when the recordings of a data record are carried out in a collimated manner such that in each case the same volume ranges of the object to be photographed are transmitted. In this way it is ensured that at least the majority of the measured data can be fused and thus an image quality advantage can be achieved for the entire recording area.

As already mentioned, it is expediently provided in the method according to the invention that a projection image of the first data record and a projection image of the second data record, which relate to the same projection directions, are fused to form a projection image of the reconstruction data record. Again, several embodiments of the method according to the invention are conceivable in order to carry out the actual fusion. In principle, methods are conceivable in which one of the data records is chosen, as it were, as a master data record, with the other data record ultimately being used to improve the master data record. However, it is also a real, ultimately "equal" fusion of the records possible.

In a concrete embodiment of the method according to the invention, it can be provided that with a lower resolution X-ray receiver of the first recording arrangement from the projection images of the first data set by means of interpolation taking into account the projection images of the second data set higher resolution projection images are determined for the reconstruction data set. In the example that the first data set is recorded with a CT X-ray receiver and the second data set is with a flat detector, it may therefore be provided, for example, that data between individual CT detector lines and / or CT detector pixels with the aid of the projection images of the flat detector be interpolated. This is advantageous in the case of wide individual detectors, but also when the image recording device is operated with high feed rate of the patient table or in spiral mode.

It is provided according to the invention that, in the case of an X-ray receiver of the second recording arrangement having a lower gray-scale dynamic response, areas which are overexposed in the projection images of the second data set are determined, in particular by detection of a constant maximum gray scale value, wherein the data lying in the overexposed areas are replaced by data of the first data set, and / or used in a truncated area X-ray receiver of the second recording arrangement in truncated areas of the projection images of the second data set of the projection images of the first data set. So truncated data due to smaller coverage areas can ultimately be easily added from the data set taken with the larger coverage X-ray receiver. Likewise, it is possible to correct the data that is incorrectly present in a dataset due to the "capping" by checking whether the constant maximum possible gray value has been measured over several pixels, and these "plateaus" are then also replaced by data of the other data record can be added. This is particularly advantageous if projection images of the first data set recorded with the CT X-ray receiver are used in the example already explained in order to improve the projection images of the second data set recorded with the flat detector.

Alternatively, it is provided according to the invention that two projection images of the first and second data sets corresponding to the same projection direction are Fourier-transformed to determine the respective spatial frequency spectrum, in particular using an "almost fourier transformation" algorithm (FFT algorithm), wherein a target spectrum combined from the two spatial frequency spectra determined and determined by Fourier transformation of the target spectrum in the spatial space a projection image of the reconstruction data set. It is therefore also conceivable to carry out the fusion of the two data sets in the spatial frequency space, taking into account the frequency information present in both data sets. It can be provided in a concrete embodiment that is at a lower spatial resolution having X-ray receiver of the first recording arrangement above the Nyquist frequency of the projection image of the first data set of this Nyquist frequency lying portion of the spatial frequency spectrum of the projection image of the second data set is added. For example, in the concrete example of using a CT X-ray receiver and a flat detector, it may then be provided that high spatial frequencies in the fusion result originate from the flat-panel projection images, but low frequencies originate from the CT X-ray receiver. The cutoff frequency can be selected, for example, as the Nyquist frequency of the CT data set. It should also be noted at this point that the frequencies in the projection images can first be extracted and analyzed longitudinally and / or transversely to the individual detector rows, and then the two projection images are fused in a subsequent step on the basis of this frequency information.

The fusion of the projection images takes place before the actual reconstruction, but it can be provided that the determination of the projection images of the reconstruction data set from the projection images of the first and second data set according to a provided for the reconstruction of the three-dimensional image data set reconstruction algorithm filtering occurs. This may be advantageous, for example, when using a ramp filter if there is a different offset in the two data sets, which offset is removed by the ramp filter.

In a further embodiment of the present invention, it can be provided that the three-dimensional image data record is determined from the projection images of the reconstruction data record by means of an iterative or analytical reconstruction algorithm. Ultimately, therefore, generally known reconstruction algorithms can be used to determine the three-dimensional image data set from the reconstruction data set, for example a method of filtered back-projection or the like. Finally, a three-dimensional image data set with increased image quality is obtained, in particular in the example of using a CT X-ray receiver and a flat detector with a higher spatial resolution compared to a pure CT reconstruction and a reduced artifact behavior in comparison to a pure flat detector reconstruction.

In addition to the method, the present invention also relates to an image recording device, comprising at least two receiving devices comprising an X-ray emitter and an X-ray receiver, the X-ray receivers differing in terms of their gray value dynamics and / or their spatial resolution and / or the size of their detection range, and a control device for performing of the method according to the invention is formed. This may, for example, already by DE 198 02 405 A1 described hybrid system, which is supplemented by the corresponding functionalities in the control device. All statements relating to the method according to the invention can be analogously transferred to the X-ray image recording device according to the invention, so that the described advantages can be achieved with it.

Further advantages and details of the present invention will become apparent from the embodiments described below and with reference to the drawings. Showing:

1 an image recording device according to the invention,

2 a flow chart of the method according to the invention, and

3 a flowchart in a sub-step of the method according to the invention.

1 shows a schematic diagram of an image pickup device according to the invention, as they are similar already in the DE 198 02 405 A1 is described. Here is a first recording arrangement with an X-ray source 1 , which is a fan-shaped first X-ray beam 2 and an X-ray receiver 3 intended. The X-ray receiver 3 Here is a CT X-ray receiver, which consists of a plurality of arranged in at least one row of single detectors, for example, 512 single detectors. A patient to be examined 4 , which includes the object to be recorded, can be placed on a patient table 5 be positioned. To scan the patient 4 becomes the first recording arrangement 1 . 3 around a measuring field 6 in which the patient 4 lies, rotated by 360 °. The change of the projection direction, ie the direction of emission of the X-ray beam 2 , is made by turning a turntable 7 achieved by means of a rotary device not shown in detail. The X-ray source 1 and the CT X-ray receiver 3 are on the turntable 7 attached.

At the turntable 7 is still a second recording arrangement with a second X-ray source 8th appropriate. The second X-ray source 8th is with regard to the first X-ray source 1 arranged offset by 90 °. The second X-ray source 8th sends a second X-ray beam 9 out on one on the opposite side of the turntable 7 attached second X-ray receiver 10 falls, which is designed here as a flat detector. The X-ray receiver 10 Therefore, in a known form, a plurality of detector elements arranged in matrix form and can be formed, for example, as a solid-state image converter of amorphous silicon.

The operation of the X-ray image recording device is controlled by a control device 11 , to which also a control and display device 12 connected. The control device 11 is designed to carry out the method according to the invention, which with reference to 2 will be explained in more detail.

It should be noted at this point that already advantageously an intrinsic registration is given by the mechanical coupling of the first and the second receiving arrangement.

2 shows a flowchart of the method according to the invention. It is in one step 13 a first set of projection images 14 added. In the present embodiment, in parallel, so with a single rotation of the turntable 7 , becomes in one step 15 a second record 16 with the second recording arrangement, so the flat detector, recorded. In the embodiment shown here is a spiral path as a path of the X-ray source when recording 1 . 8th realized by the patient table is advanced by a feed distance, while the turntable 7 the rotation by 360 ° (corresponding to twice π) performs. In this case, however, the same trajectory of the beam exit points or focal spots of the X-ray source 1 and 8th allows by the focal spot of a radiator is shifted by a quarter of the feed distance in the feed direction. In the present case, this happens by the electron beam impinging on a rotary anode being able to be selectively deflected by a magnetic field. Thus, an adjustment for different feed distances is possible. An alternative embodiment provides, one of the X-ray source 1 . 8th entirely in the feed direction of the patient table 5 to make mechanically displaceable.

By means of the same recording trajectories, it is achieved that for each projection picture of the first data record recorded under a certain projection direction 14 a projection image of the data record taken in the same projection direction 16 exist. This allows the following fusion of the first record 14 and the second record 16 in one step 17 to a reconstruction record 18 of projection images. It is provided that always a projection image of the first record 14 and a projection image of the second data set 16 which relate to the same projection directions, to a projection image of the reconstruction data set 18 be merged. In the present case, three different variants are conceivable.

In a first variant, the first record 14 , hence the CT dataset, considered as a kind of master dataset, using the projection images of the second dataset 16 that were recorded with the flat detector should be improved. It should be noted here in general that the CT X-ray receiver 3 Although a higher gray value dynamics and a larger detection range than the trained as a flat detector X-ray receiver 10 but, however, the spatial resolution of the X-ray receiver 10 is better. Thus, data between the individual CT detector lines and / or CT detector pixels are now obtained with the aid of the data obtained from the flat detector in the second data set 16 interpolated information contained.

A second variant ultimately takes the opposite route. In this case, the projection images of the second data record taken with the flat detector become 16 considered as a master record to be improved using the CT data of the first record. For this purpose, on the one hand, the truncated data that is missing due to the smaller detection range, from the projection image of the first record 14 added. At the same time, however, the image taken with the flat detector is also checked for "capping" areas in which the maximum possible gray value of the flat detector is constantly present. Here is an over-radiation. This can be "corrected" by using CT data from the first image data set for these "plateaus" 14 , Of course, from the projection image of the same projection direction to be replaced.

Finally, in a third variant, it is conceivable to fuse two projection images in the spatial frequency space by first determining the spatial frequency spectrum of both projection images by a fast Fourier transformation (FFT). From this, a fused target spectrum is created, each containing parts of the two single spatial frequency spectra. Here are the above a cutoff frequency in the fusion result, ie in the target spectrum, shares from the second record 16 (Flat detector), the low spatial frequency components of the first data set 14 (CT-X-ray receiver). The cutoff frequency is considered the Nyquist frequency of the CT projection image of the first data set 14 selected. It is possible to analyze the frequencies separately along and across the rows of detectors. Another Fourier transformation turns the target spectrum into the projection image of the reconstruction data set 18 generated.

It should be noted that if the reconstruction algorithm used in the following to determine the improved three-dimensional image data set comprises an upstream filter step, in the case of filtered backprojection, for example filtering with a ramp filter, the fusion of the step 17 even after this filtering can be done.

In one step 19 finally become the projection images of the reconstruction data set 18 used to construct a three-dimensional image data set by means of an analytical or iterative reconstruction algorithm 20 to reconstruct which is improved in terms of image quality compared to a pure CT image data set or DynaCT ^® -Bilddatensatz.

In the just discussed embodiment of the method according to the invention, the data acquisition in the steps 13 and 15 performed so that same recording trajectories are given. This does not necessarily have to be the case. Thus, it is possible to use any, different recording trajectories, if in a further embodiment of the method according to the invention the step 17 as in 3 is modified to the first record 14 to supplement virtual, determined by computational methods projection images, so that all projection directions of the second data set 16 also in the first record 14 occurrence.

Although here is an example of an addition to the first record 14 that with the CT X-ray receiver 3 is recorded, it should be noted that this of course also analogous with respect to the second record 16 that was recorded with the flat detector is possible.

In a sub-step 21 of the step 17 becomes from the projection images of the first record 14 a three-dimensional pre-reconstruction dataset 22 determined. At the same time, the projection directions that are in the second record 16 occur in the first record 14 not, certainly. In a sub-step 23 Then, by forward projection with respect to the missing projection directions, in particular ray tracing methods, virtual projection images of an intermediate data record are produced 14 ' determines which of the record 14 is added, so that ultimately in this second embodiment of the method according to the invention in each case a projection image from the first data set 14 and a projection image from the second data set 16 present, which correspond to the same direction of projection, so that as in the first embodiment of the method according to the invention can be continued with the merger.

Claims (11)

Method for operating an X-ray image recording device, comprising at least two X-ray emitters ( 1 . 8th ) and an X-ray receiver ( 3 . 10 ) comprises comprehensive receiving arrangements, wherein the x-ray receivers ( 3 . 10 ) with respect to their gray value dynamics and / or their spatial resolution, wherein a first data set ( 14 ) of projection images of an object to be recorded using different projection directions is recorded with a first recording device and a second, with the first data set ( 14 ) record registered by projection images ( 16 ) of projection images of the object to be recorded using different projection directions with a second recording device, after which a reconstruction of a three-dimensional image data set ( 20 ) using one of the Projection images of the first and second data sets ( 14 . 16 ) determined reconstruction data set ( 18 ) of projection images, and wherein a projection image of the first data set ( 14 ) and a projection image of the second data set ( 16 ), which relate to the same projection directions, to a projection image of the reconstruction data set ( 18 ) are fused, characterized in that at a lower gray value dynamic having X-ray receiver ( 10 ) areas of the second recording arrangement in the projection images of the second data set ( 16 ), wherein the data lying in the overexposed areas is determined by data from the first data set ( 14 ), or that two projection images of the first and second data sets (Fig. 14 . 16 ) are Fourier-transformed to determine the respective spatial frequency spectrum, whereby a target spectrum combined from the two spatial frequency spectra is determined, and a projection image of the reconstruction data set is determined by Fourier transformation into the spatial domain (FIG. 18 ) is determined, wherein at a lower spatial resolution having X-ray receiver ( 3 ) of the first recording arrangement above the Nyquist frequency of the projection image of the first data set ( 14 ) the portion of the spatial frequency spectrum of the projection image of the second data set lying above this Nyquist frequency ( 16 ) is added. Method according to claim 1, characterized in that as X-ray receiver ( 3 ) of the first receiving arrangement a CT X-ray receiver ( 3 ), which consists of arranged in at least one detector line single detectors, and as an X-ray receiver ( 10 ) of the second recording device, a flat detector, comprising a plurality of detector elements arranged in the manner of a matrix, is used. A method according to claim 1 or 2, characterized in that at different sized detection range of the X-ray receiver ( 3 . 10 ) at the X-ray receiver ( 3 . 10 ) is limited with the larger detection range of the receiving area so that it corresponds to the smaller detection range of the other X-ray receiver ( 10 . 3 ) corresponds. Method according to one of the preceding claims, characterized in that the recording of the data sets ( 14 . 16 ) of projection images in such a way that in each case two individual projection images of different data sets ( 14 . 16 ), which are recorded in the same projection direction. A method according to claim 4, characterized in that when recording projection images along a circular path of the X-ray source ( 1 . 8th ) arranged in the plane of the circular path receiving arrangements are rotated by a fixed angle to each other. A method according to claim 4, characterized in that when recording a spiral path, a combination of a circular path of the X-ray source ( 1 . 8th ) and a feed of a patient table ( 5 ) of the image recording device is used perpendicular to the circular path by a predetermined distance, wherein arranged in the plane of the circular path and against each other rotated at a fixed angle receiving arrangements of the radiation exit point of at least one X-ray source ( 1 . 8th ) is displaced along the feed direction during the recording by a constant, depending on the angle and the feed distance certain length. Method according to one of claims 1 to 3, characterized in that, if at least one projection image of a projection direction of a data set ( 14 . 16 ) no projection image of the same projection direction in the other data set ( 16 . 14 ) exists, from the first record ( 14 ) of projection images, a three-dimensional pre-reconstruction data set ( 22 ), from which by forward projection in the second record ( 16 ) of projection images and not in the first data set ( 14 ) of projection images occurring at least one intermediate data record ( 14 ' ) of calculated projection images by which the first data set ( 14 ) is extended by projection images. Method according to one of the preceding claims, characterized in that in the case of a x-ray receiver having a lower detection range ( 10 ) of the second recording arrangement in truncated areas of the projection images of the second data set ( 16 ) Data of the projection images of the first data set ( 14 ) be used. Method according to one of the preceding claims, characterized in that the determination of the projection images of the reconstruction data record ( 18 ) from the projection images of the first and second data set ( 14 . 16 ) after reconstructing the three-dimensional image data set ( 20 ) provided for in the reconstruction algorithm. Method according to one of the preceding claims, characterized in that from the projection images of the reconstruction data set ( 18 ) using an iterative or analytical reconstruction algorithm of the three-dimensional image data set ( 20 ) is determined. Image recording device comprising at least two an X-ray source ( 1 . 8th ) and an X-ray receiver ( 3 . 10 ) comprehensive receiving arrangements, wherein the X-ray receiver ( 3 . 10 ) with respect to their gray value dynamics and / or their spatial resolution, as well as a control device ( 11 ), which is designed to carry out a method according to one of the preceding claims.

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