Method for generating an image

A method is disclosed for generating an image. An embodiment of the method includes detecting a first projection data set via a first group of detector units, the first group including a first plurality of first detector units, each having more than a given number of detector elements; detecting a second projection data set via a second group of detector units, the second group including a second plurality of second detector units, each including, at most, the given number of detector elements; reconstructing first image data based on the first projection data set; reconstructing second image data based on the second projection data set; and combining the first image data and the second image data. A non-transitory computer readable medium, a data processing unit, and an imaging device including the data processing unit are also disclosed.

PRIORITY STATEMENT

The present application hereby claims priority under 35 U.S.C. § 119 to German patent application number DE 102015208905.3 filed May 13, 2015, the entire contents of which are hereby incorporated herein by reference.

FIELD

At least one embodiment of the invention generally relates to a method for generating an image of an object from a first projection data set detected with a first group of detector units and a second projection data set detected with a second group of detector units. At least one embodiment of the invention also generally relates to a data processing unit for generating an image of an object from a first projection data set detected with a first group of detector units and a second projection data set detected with a second group of detector units. At least one embodiment of the invention also generally relates to an imaging device, to a computer program product and to a computer-readable medium.

BACKGROUND

In imaging applications, in particular in computerized tomography, a detector can be used to detect a projection data set. When detecting a projection data set radiation quanta, for example X-ray quanta, which issue from a radiation source, for example an X-ray source, and penetrate a region of an object to be imaged, strike the detector. An image of the region of the object to be imaged can be generated based on the projection data set. A quantum-counting detector is designed for spatially resolved detection of radiation quanta. In particular, a quantum-counting detector enables detection of a projection data set as a function of the energy of incident radiation quanta. Since the interaction of radiation quanta with material is dependent on the energy of the radiation quanta, a quantum-counting detector offers many advantages in respect of the depiction and identification of structures of the object.

To detect the location of incidence of a radiation quantum a detector comprises a plurality of detector units. Each of these detector units can be respectively assigned to at least one location at which a radiation quantum can strike the detector. The flux density of the radiation quanta striking a detector unit can be very high, in particular if the radiation is not significantly attenuated by the object. To be able to achieve high accuracy when detecting the projection data set, in particular in a quantum counting detector, the number of radiation quanta registered by the detector unit during a given time segment must not, as a rule, exceed an admissible value. This admissible value can depend, for example, on the electronic device of the detector and on physical properties of the detector. For example, this admissible value can depend, inter alia, on the width of a current and/or voltage pulse which is provided when detecting a radiation quantum.

A detector unit can have one or more detector element(s). A detector unit, which has exactly one detector element, is also called subpixels. A detector unit, which has a plurality of detector elements, is also called macropixels. The projection surface of a detector element of a quantum counting detector is typically very small, for example, approximately square with 250 micrometer edge length. The admissible value can thereby be adhered to even with a high flux density of radiation quanta striking the detector. Furthermore, a very high spatial resolution can be attained thereby. In the example having a 250 micrometer edge length a spatial resolution can be achieved such that 40 pairs of lines per centimeter can be resolved. For example bone structures, in particular of the inner ear, or vessels can therefore be imaged with the spatial resolution of a flat panel detector used in conventional angiography.

Use of this spatial resolution can have an adverse effect on the spectral quality of the scan data. With a small edge length of the detector elements the spectral resolution of the radiation quanta registered in different energy ranges can be impaired by the increasing influence of physical effects. For example, in the case of charge sharing, i.e. the simultaneous detection of a radiation quantum in the two detector elements registered close to the boundary of two detector elements, detection of the energy of the radiation quantum is very inaccurate. Furthermore, smaller detector elements can have a signal stability that is reduced compared to larger detector elements, and/or increased noise owing to inhomogeneities in the detector material.

The choice of detector units, which have a plurality of detector elements, can therefore be advantageous for good spectral quality of the detector and disadvantageous for good spatial resolution of the detector.

A quantum-counting radiation detector is known from DE 10 2011 077 859 B4 in which detector elements are divided into groups of adjacent detector elements in order to form larger detector units.

SUMMARY

At least one embodiment enables generation of an image having improved spatial resolution and improved spectral quality.

At least one embodiment is directed to a method; at least one embodiment is directed to a data processing unit; at least one embodiment is directed to an imaging; at least one embodiment is directed to a computer program product; at least one embodiment is directed to a computer-readable medium. Further claims relate to advantageous embodiments of the invention.

In the inventive method of at least one embodiment for generating an image a first projection data set is detected via a first group of detector units and a second projection data set detected via a second group of detector units. The first group has a first plurality of first detector units, wherein the first detector units each have more than a given number of detector elements, wherein the first detector units are each designed for spectrally resolved detection of radiation quanta. The second group has a second plurality of second detector units, wherein the second detector units each have, at most, the given number of detector elements, wherein the second detector units are each designed for spectrally resolved detection of radiation quanta. First image data is reconstructed based on the first projection data set. Second image data is reconstructed based on the second projection data set. The first image data and the second image data are combined. In particular, the first image data and the second image data are combined to form the image.

An example embodiment of the inventive imaging device has a radiation source, a detector and an inventive data processing unit.

According to an embodiment of the invention, the detector has the first group of detector units and the second group of detector units. According to an embodiment of the invention the detector has a plurality of detector elements.

One embodiment of the invention provides that the method comprises the following steps:

detecting a first projection data set via a first group of detector units of a detector, wherein the first group has a first plurality of first detector units of the detector, wherein the first detector units of the detector each have more than a given number of detector elements of the detector, wherein the first detector units are each designed for spectrally resolved detection of radiation quanta,

detecting a second projection data set via a second group of detector units of the detector, wherein the second group has a second plurality of second detector units of the detector, wherein the second detector units of the detector each have, at most, the given number of detector elements of the detector, wherein the second detector units are each designed for spectrally resolved detection of radiation quanta,

reconstructing first image data based on the first projection data set,

reconstructing second image data based on the second projection data set, and

combining the first image data and the second image data.

According to an embodiment of the invention the detector is the detector of a single-source computer tomograph. In particular, an embodiment of the inventive imaging device can be a single-source computer tomograph.

According to a further embodiment of the invention the inventive imaging device has a first radiation source, a first detector interacting with the first radiation source, a second radiation source, a second detector interacting with the second radiation source and an embodiment of an inventive data processing unit. In particular, an embodiment of the inventive imaging device can be a dual-source computer tomograph.

According to one embodiment of the invention, a computer program product has a computer program which can be loaded directly into a data processing unit of an imaging device, having program sections in order to carry out all steps of an embodiment of the inventive method when the computer program is run in the data processing unit.

Program sections which can be read and executed by a data processing unit are stored on the inventive computer-readable medium in order to carry out all steps of an embodiment of an inventive method when the program sections are executed by the data processing unit.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

In the inventive method of at least one embodiment for generating an image a first projection data set is detected via a first group of detector units and a second projection data set detected via a second group of detector units. The first group has a first plurality of first detector units, wherein the first detector units each have more than a given number of detector elements. The second group has a second plurality of second detector units, wherein the second detector units each have, at most, the given number of detector elements. First image data is reconstructed based on the first projection data set. Second image data is reconstructed based on the second projection data set. The first image data and the second image data are combined. In particular, the first image data and the second image data are combined to form the image.

The first projection data set and the second projection data set can relate, for example, to radiation quanta of radiation which, starting from a radiation source, is projected onto detector units and in the process penetrates a region of the object that is to be mapped. The first projection data set and the second projection data set can include, for example, information about an interaction of the radiation with the object, in particular an attenuation of the radiation by the object.

A projection data set can comprise one or more projection profile(s). An arrangement of a radiation source and/or detector units in respect of the region of the object to be mapped can be assigned, in particular is assigned, to each of these projection profiles respectively. An arrangement of this kind can be defined for example by an angle of rotation of a rotor, on which the radiation source and/or the detector units are arranged so as to rotate about the region of the object to be mapped.

One embodiment of the invention provides that the first projection data set and the second projection data set are detected simultaneously. One embodiment of the invention provides that the first projection data set is provided directly by the first group of detector units and that the second projection data set is provided directly by the second group of detector units.

Since the first detector units each have more than a given number of detector elements a first projection data set can be implemented with improved spectral quality compared to the second projection data set. Since the second detector units each have, at most, the given number of detector elements, a second projection data set can be implemented with improved spatial resolution compared to the first projection data set.

First or second image data can be reconstructed from the first or second projection data set respectively using the same reconstruction method or different reconstruction methods, for example, on the basis of a filtered back projection. In particular, the second image data can be reconstructed using a different reconstruction method to reconstruction of the first image data. For example, information, which is based on the first image data, can be used for reconstruction of the second image data.

Combining the first image data and the second image data can, in particular, comprise the pixel-by-pixel execution of a mathematical operation. A mathematical operation can, in particular, comprise one or more basic arithmetic operations, for example, adding and/or multiplying. Combining can in particular include filtering the first image data and/or filtering the second image data. The mathematical operation can relate, for example, to a value of a pixel of the first image data or the filtered first image data and a value of a pixel of the second image data or filtered second image data.

The first image data and the second image data can be combined, for example, with the aid of what is known as a frequency-split method.

According to an example embodiment of the invention, the first image data is filtered via a first filter and the second image data via a second filter, wherein the filtered first image data and the filtered second image data are added pixel-by-pixel.

In this way the first image data and the second image data are combined as a function of the spatial frequencies of the first image data and the spatial frequencies of the second image data. This should, in particular, be taken to mean that for a first spatial frequency range image information from the first image data is weighted more strongly relative to image information from the second image data, and for a second spatial frequency range image information from the second image data is weighted more strongly relative to image information from the first image data.

In this way an image of the object can be generated, wherein the image in the first spatial frequency range has image information which is based substantially on the first projection data set, and in the second spatial frequency range has image information which is based substantially on the second projection data set. An image can be attained thereby in which the improved spectral quality of the first detector units and the improved spatial resolution of the second detector units are combined.

According to an example embodiment of the invention, the first filter has a first transfer function and the second filter has a second transfer function, wherein the total of the first transfer function and the second transfer function is a constant function.

The boundary condition can thereby be met that for the notional case of identical first and second image data, the combined image data is identical to the first and second image data.

According to an example embodiment of the invention, the first filter has a low pass filter and the second filter a high pass filter.

One embodiment of the invention provides that the first filter is a low pass filter is and/or that the second filter is a high pass filter.

In particular, the high pass filter and the low pass filter can be complementary to each other such that the total of the Fourier transformation of the high pass filter and the Fourier transformation of the low pass filter is substantially constant. The boundary condition can also be met in this way.

An image of the object can be generated thereby, wherein, in a region of deeper spatial frequencies, i.e. coarser structures, the image has information having an improved spectral quality, and in a region of higher spatial frequencies, i.e. finer structures, has image information having an improved spatial resolution.

The first image data and back projection data based on the second projection data set can be combined, for example with the aid of what is known as an HYPR method (Highly Constrained Backprojected Reconstruction). The first image data can form what is known as a prior image in this connection. A method of this kind is known, for example, from U.S. Pat. No. 7,545,901 B2, the entire contents of which are incorporated herein by reference.

According to an example embodiment of the invention, the first image data and the second image data are multiplied pixel-by-pixel.

According to an example embodiment of the invention, the second image data is reconstructed in that back projection data based on the second projection data set is generated, wherein a back projection path can be assigned, in particular is assigned, to a pixel of the back projection data. The back projection data is normalized, wherein information based on a pixel group is used for the pixels of the back projection data, wherein the pixel group comprises pixels of the first image data which can be assigned, in particular are assigned, to the back projection path. The normalized back projection data is added pixel-by-pixel.

Back projection data can be generated using a back projection method based on the second projection data set.

The second image data reconstructed in this way and the first image data are preferably combined in that the first image data and the second image data are multiplied pixel-by-pixel.

An image of the object can thereby be generated such that for a region of deeper spatial frequencies, i.e. coarser structures, information from the first projection data set can be weighted more strongly relative to information from the second projection data set and for a region of higher spatial frequencies, i.e. finer structures, information from the second projection data set can be weighted more strongly relative to information from the first projection data set. In a region of deeper spatial frequencies, i.e. coarser structures, the image generated in this way has image information having an improved spectral quality and in a region of higher spatial frequencies, i.e. finer structures, has image information having improved spatial resolution.

As a rule, reduced spatial resolution is less disadvantageous in coarser structures and reduced spectral quality is less disadvantageous in finer structures. The invention therefore enables generation of an image having improved spatial resolution and improved spectral quality overall.

A given pixel of the first image data can, in particular, then be designated as being assignable to the back projection path if it corresponds to a pixel of the back projection data, wherein the value of the pixel of the back projection data is determined at least partially by a back projection along the back projection path. Corresponding pixels should, in particular, be taken to mean pixels relating to the same position in respect of a region of an object to be mapped.

According to an example embodiment of the invention, the value of the pixel of the back projection data is divided by the total of the values of the pixels of the pixel group.

In particular, normalizing of the back projection data can include dividing the value of the pixels of the back projection data by the total of the values of the pixels of the pixel group.

The value Rlmn of the pixel of the normalized back projection data can be calculated, for example, according to
Rlmn=Plm/ΣnAmn(1)

The value Cmnof the generated image can be calculated, for example, according to
Cmn=AmnΣlRlmn(2)

Plmstands for the value which is based on the second projection data set and is back-projected on the back projection path in order to generate back projection data. Amnstands for the values of the pixels of the pixel group. Amnstands, in particular, for the values of the pixels of the first image data which can be assigned to the back projection path. The index1relates to a projection profile of the second projection data set, wherein the pixel can be assigned to the projection profile. The index m relates to the back projection path. The index n relates to the position of pixels of the back projection data or of pixels of the first image data in respect of the back projection path.

A value of a pixel can relate, in particular, to an attenuation of a flux density of radiation quanta. It would, however, also be conceivable for the value of the pixel to alternatively or additionally relate to further interactions of radiation quanta with the object, for example a phase shift.

The first detector units can each have a plurality of detector elements. The second detector units can each have one or more detector elements. The given number can be, for example, one, four, nine or sixteen.

For example, the first group of detector units can have at least one third detector unit, wherein the first plurality of first detector units does not have the at least one third detector unit. For example, the second group of detector units can have at least one fourth detector unit, wherein the second plurality of second detector units does not have the at least one fourth detector unit.

For example, the first group can have one or more detector unit(s) which, at most, has/have the given number of detector elements. For example, the second group can have one or more detector unit(s) which has more than the given number of detector elements.

One embodiment of the invention provides that the first group of detector units comprises the first plurality of first detector units.

One embodiment of the invention provides that the second group of detector units comprises the second plurality of second detector units.

One embodiment of the invention provides that the first projection data set is detected via the first plurality of first detector units and that the second projection data set is detected via the second plurality of second detector units.

One embodiment of the invention provides that the first detector units each have a first number of detector elements and that the second detector units each have a second number of detector elements. The first number can be, for example, nine or sixteen. The second number can be, for example, one or four.

One embodiment of the invention provides that the detector units each have a given number of rows of detector elements, wherein each of the rows has a given number of columns of detector elements. The number of columns is preferably equal to the number of rows. The number of columns and/or the number of rows can be, for example one, two, three or four.

One embodiment of the invention provides that the first detector units each have a plurality of detector elements and that the second detector units each have exactly one detector element. In this way the first detector units can form macropixels and the second detector units subpixels.

The detector elements are, in particular, each designed to provide a first electrical signal, for example a quantity of electricity, as a function of incidence of a radiation quantum on the respective detector element.

A given detector unit has, in particular, then a given detector element if a second electrical signal which can be assigned or is assigned to the given detector unit is provided as a function of incidence of a radiation quantum on the given detector element. This can be achieved, for example, by a processing stage, by way of which a second electrical signal can be provided for each detector unit respectively. A processing stage of this kind is preferably designed such that the second electrical signal is provided as a function of the first electrical signals of the detector elements which the respective detector unit has. The processing stage can have components designed in the form of software. Alternatively or additionally, the processing stage can have components designed in the form of hardware.

If a quantity of electricity can be assigned or is assigned to each of the first electrical signals of the detector elements, which a given detector unit has, for example, the total of these quantities of electricity can be assigned to the second electrical signal of the given detector unit. The wording that a detector element is assigned to a detector unit will be used below synonymously with the wording that the detector unit comprises the detector element.

According to an example embodiment of the invention, a given detector element can optionally be assigned, in particular is assigned, to a first detector unit or a second detector unit or both a first detector unit and a second detector unit. A given detector element can preferably be assigned, in particular is assigned, to a plurality of first detector units, a plurality of second detector units or both a plurality of first detector units and a plurality of second detector units.

For this purpose the processing stage can have a device for dividing and/or a device for duplicating a first electrical signal of a detector element. Furthermore, the processing stage can be designed such that parts and/or copies of the first electrical signal of a given detector element are processed on processing branches, wherein at least one processing branch is assigned to each detector unit which has the given detector element.

A detector unit preferably has a plurality of adjacent detector elements. It would, however, also be conceivable to assign mutually spaced apart detector elements to one detector unit. An assignment of detector elements to first detector units and second detector units can be fixed. It would also be conceivable for the assignment of detector elements in particular to first detector units and second detector units to be set in accordance with the needs of the user and/or the requirements of the examination, for example via an assignment stage.

The assignment stage can have components designed in the form of software. Alternatively or additionally, the assignment stage can have components designed in the form of hardware.

According to an example embodiment of the invention, the first detector units and/or the second detector units are each designed for spectrally resolved detection of radiation quanta. One embodiment of the invention provides that the first detector units and/or the second detector units are designed for quantum-counting detection of radiation quanta. In particular, the detector elements can be designed for quantum-counting detection of radiation quanta.

Spectrally resolved detection, for example quantum-counting detection, of radiation quanta should, in particular, be taken to mean that the first electrical signal or the second electrical signal is provided as a function of the energy of the incident radiation quantum. The incident radiation quantum can thereby be assigned to one of a plurality of given energy range(s) respectively. In this way a first projection data set and a second projection data set respectively can be detected for each of the plurality of given energy ranges.

According to an example embodiment of the invention, the first detector units and/or the second detector units each have a spectral resolution, wherein the spectral resolution can be defined, in particular is defined, by the number of detector elements incorporated by the respective detector unit. The first detector units and/or the second detector units are preferably each designed such that the spectral resolution of a given detector unit improves with an increasing number of detector elements incorporated by the given detector unit.

According to an example embodiment of the invention, the first detector units and/or the second detector units each have a spatial resolution, wherein the spatial resolution can be defined, in particular is defined, by the number of detector elements incorporated by the respective detector unit. The first detector units and/or the second detector units are preferably each designed such that the spatial resolution of a given detector unit improves with a decreasing number of detector elements incorporated by the given detector unit.

An example embodiment of the invention enables, in particular, an image simultaneously having high spatial resolution and good spectral separation to be generated from data from a quantum counting detector which has the first group of detector units and the second group of detector units.

One embodiment of the invention provides that the first detector units each have a projection surface which projection surface is larger than a given surface value, and that the second detector units each have a projection surface, which projection surface is, at most, as large as the given surface value. A projection surface of a detector unit or detector element should, in particular, be taken to mean the surface which is provided and/or designed for the incidence of radiation quanta for the purpose of detecting a projection data set.

One embodiment of the invention provides that the projection surface of a given detector unit is formed by the projection surfaces of the detector elements presented by the given detector unit and/or is equal to the total of the projection surfaces of the detector elements presented by the given detector unit.

An example embodiment of the data processing unit has a first group of detector units, a second group of detector units, a reconstruction unit and a combination unit. The first group of detector units is designed for detecting a first projection data set. The first group has a first plurality of first detector units, wherein the first detector units each have more than a given number of detector elements, wherein the first detector units are each designed for spectrally resolved detection of radiation quanta. The second group of detector units is designed for detecting a second projection data set. The second group has a second plurality of second detector units, wherein the second detector units each have, at most, the given number of detector elements, wherein the second detector units are each designed for spectrally resolved detection of radiation quanta. The reconstruction unit is designed for reconstructing first image data based on the first projection data set and for reconstructing second image data based on the second projection data set. The combination unit is designed for combining the first image data and the second image data.

One embodiment provides that the combination unit has a first filter, a second filter and an adding unit. The first filter is designed for filtering the first image data. The second filter is designed for filtering the second image data. The adding unit is designed for pixel-by-pixel addition of the filtered first image data and filtered second image data.

According to an example embodiment of the invention, the reconstruction unit has a back projection unit, a normalizing unit and an adding unit auf. The reconstruction unit is designed for generating back projection data based on the second projection data set, wherein a back projection path can be assigned, in particular is assigned, to a pixel of the back projection data. The normalizing unit is designed for normalizing the back projection data, wherein information based on a pixel group is used for the pixel of the back projection data, wherein the pixel group comprises pixels of the first image data which can be assigned, in particular are assigned, to the back projection path. The adding unit is designed for pixel-by-pixel addition of the normalized back projection data.

One embodiment provides that the normalizing unit has a dividing unit, wherein the dividing unit is designed for dividing the value of the pixel of the back projection data by the total of the values of the pixels of the pixel group.

According to an example embodiment of the invention, the data processing unit is designed for carrying out an example embodiment of the inventive method.

An example embodiment of the invention therefore enables an image having improved spatial resolution and improved spectral quality to be generated on the basis of the first projection data set and the second projection data set.

An example embodiment of the inventive imaging device has a radiation source, a detector and an inventive data processing unit.

According to an embodiment of the invention, the detector has the first group of detector units and the second group of detector units. According to an embodiment of the invention the detector has a plurality of detector elements.

One embodiment of the invention provides that the method comprises the following steps:

detecting a first projection data set via a first group of detector units of a detector, wherein the first group has a first plurality of first detector units of the detector, wherein the first detector units of the detector each have more than a given number of detector elements of the detector,

detecting a second projection data set via a second group of detector units of the detector, wherein the second group has a second plurality of second detector units of the detector, wherein the second detector units of the detector each have, at most, the given number of detector elements of the detector,

reconstructing first image data based on the first projection data set,

reconstructing second image data based on the second projection data set, and

combining the first image data and the second image data.

According to an embodiment of the invention the detector is the detector of a single-source computer tomograph. In particular, the inventive imaging device can be a single-source computer tomograph.

According to a further embodiment of the invention the inventive imaging device has a first radiation source, a first detector interacting with the first radiation source, a second radiation source, a second detector interacting with the second radiation source and an inventive data processing unit. In particular, the inventive imaging device can be a dual-source computer tomograph.

According to one embodiment of the invention, it is provided that the first detector has the first group of detector units and/or that the second detector has the second group of detector units. According to one embodiment of the invention it is provided that the first detector has a plurality of detector elements and/or that the second detector has a plurality of detector elements.

According to one embodiment of the invention, a computer program product has a computer program which can be loaded directly into a data processing unit of an imaging device, having program sections in order to carry out all steps of an embodiment of the inventive method when the computer program is run in the data processing unit.

Program sections which can be read and executed by a data processing unit are stored on the inventive computer-readable medium in order to carry out all steps of an embodiment of an inventive method when the program sections are executed by the data processing unit.

According to an embodiment of the invention, the imaging device is chosen from the group comprising a computer tomograph, a single-photon emission computer tomograph (SPECT device), a positron emission tomography (PET device), a magnetic resonance tomograph and combinations thereof. In particular, the medical imaging device can have an X-ray apparatus, a C-arm X-ray apparatus, an ultrasound apparatus and the like. The imaging device can also be a combination of a plurality of imaging and/or irradiation modalities, for example, a PET-CT device or a SPECT-CT device. An irradiation modality can have, for example, an irradiation apparatus for therapeutic irradiation.

Within the context of the invention features which are described in relation to different embodiments and/or different claim categories (method, unit, etc.) can be combined to form further embodiments. In particular, the features, advantages and embodiments described in relation to the inventive method can also be transferred to the inventive data processing unit, inventive imaging device, inventive computer program product and inventive computer-readable and vice versa. In other words, the concrete claims can also be developed by the features which are described or claimed in connection with a method. The corresponding functional features of the method are formed by appropriate concrete modules, in particular by hardware modules.

FIG. 1shows a flowchart of a method for generating an image according to a first embodiment of the invention.

In step RP1a first projection data set P1is detected via a first group G1of detector units. In step RP2a second projection data set P2is detected via a second group G2of detector units. The first group G1has a first plurality of first detector units DET1, wherein the first detector units DET1each have more than a given number of detector elements DEL. The second group G2has a second plurality of second detector units DET2, wherein the second detector units DET2each have, at most, the given number of detector elements DEL. In step RI1first image data I1is reconstructed based on the first projection data set P1. In step RI2second image data I2is reconstructed based on the second projection data set P2. In step K12the first image data I1and the second image data I2are combined. In particular, the first image data I1and the second image data I2are combined in step K12to form the image IF.

In the embodiments shown below substantially the differences from the embodiments illustrated above in each case are described. Substantially unchanging features, in particular method steps, are basically provides with identical reference numerals.

FIG. 2shows a flowchart of a method for generating an image according to a second embodiment of the invention.

The second embodiment of the invention provides that step K12includes steps F1, F2and A12. In step F1the first image data I1is filtered via a first filter. In step F2the second image data I2is filtered via a second filter. In step A12the filtered first image data FI1and the filtered second image data FI2are added pixel-by-pixel. In this way the filtered first image data FI1and the filtered second image data FI2are combined to form the image IF. In step PIF the image IF is supplied, for example for display and/or further processing.

FIG. 3shows a flowchart of a method for generating an image according to a third embodiment of the invention.

The third embodiment of the invention provides that step RI2includes steps B2, N2and A2. In step B2back projection data BP2based on the second projection data set P2is generated, wherein a back projection path BPP can be assigned to a pixel PIX2of the back projection data BP2. In step N2the back projection data BP2is normalized, wherein for the pixel PIX2of the back projection data BP2information based on a pixel group PG1is used, wherein the pixel group PG1comprises pixels of the first image data I1to which back projection path BPP can be assigned, in particular is assigned. In step A2the normalized back projection data NBP2is added pixel-by-pixel.

FIG. 4shows a flowchart of a method for generating an image according to a fourth embodiment of the invention.

The fourth embodiment of the invention provides that step N2includes step D2and that step K12includes step M12. In step M12the first image data I1and the second image data I2are multiplied pixel-by-pixel. In step D2the value of the pixel PIX2of the back projection data BP2is divided by the total of the values of the pixels of the pixel group PG1.

FIG. 5shows an example for first image data I1and back projection data BP2.

The back projection path BPP can be assigned, in particular is assigned, to the pixel PIX2of the back projection data BP2. One criterion for this assignability or assignment is that the projection value PV2of the projection profile PP2of the projection data set P2is back-projected along the back projection path BPP in order to determine the value of the pixel PIX2.

The pixel group PG1comprises pixels of the first image data I1which can be assigned, in particular are assigned, to the back projection path BPP. The pixel PIX1A of the first image data I1can be assigned, in particular is assigned, to the back projection path BPP. It corresponds to the pixel PIX2A of the back projection data BP2, wherein the value of the pixel PIX2A of the back projection data BP2is determined at least partly by a back projection along the back projection path BPP. The pixel PIX1A and the pixel PIX2A relate to the same position in respect of a region of an object to be mapped.

FIG. 6shows a data processing unit35according to a fifth embodiment of the invention.

The data processing unit35has a first group G1of detector units, a second group G2of detector units, a reconstruction unit51and a combination unit52. The first group G1of detector units is designed for detecting RP1a first projection data set P1. The second group G2of detector units is designed for detecting RP2a second projection data set P2. The first group G1has a first plurality of first detector units DET1, wherein the first detector units DET1each have more than a given number of detector elements DEL. The second group G2has a second plurality of second detector units DET2, wherein the second detector units DET2each have, at most, the given number of detector elements DEL. The reconstruction unit51is designed for reconstructing first image data I1based on the first projection data set P1and for reconstructing second image data I2based on the second projection data set P2. The combination unit52is designed for combining the first image data I1and second image data I2.

FIG. 7shows a data processing unit35according to a sixth embodiment of the invention.

The sixth embodiment of the invention provides that the reconstruction unit51has a back projection unit60, a normalizing unit61and an adding unit62. The back projection unit60is designed for generating back projection data BP2based on the second projection data set P2, wherein a back projection path BPP can be assigned, in particular is assigned, to a pixel PIX2of the back projection data BP2. The normalizing unit61is designed for normalizing N2the back projection data BP2, wherein information based on a pixel group PG1is used for the pixel PIX2of the back projection data BP2, wherein the pixel group PG1comprises pixels of the first image data I1which can be assigned, in particular are assigned, to the back projection path BPP. The adding unit62is designed for pixel-by-pixel addition A2of the normalized back projection data NBP2.

The data processing unit35is optionally designed for carrying out one or more method(s) according to a described embodiment of the invention.

FIG. 8shows an imaging device1according to a seventh embodiment of the invention.

A computer tomograph is shown, by way of example, for the imaging device1, without limiting the general inventive idea.

The imaging device1has a gantry20. The gantry20has a stationary support frame21. The gantry20has a rotor24mounted so it can be rotated by a pivot bearing device. The imaging device1has an image recording region4formed by a tunnel-like opening. A region of an object to be mapped can be arranged in the image recording region4.

A radiation projection device26,28is arranged on the rotor24. The radiation projection device26,28has a radiation source26which is designed to emit radiation quanta, and a detector28which is designed for detection of radiation quanta. The radiation quanta27can pass from the radiation source26to the region to be mapped and, following an interaction with the region to be mapped, strike the detector28. In this way a projection profile of the region to be mapped can be detected.

At least one projection profile respectively can be detected for different arrangements of the radiation source26and the detector in respect of the region of the object to be mapped by rotation of the radiation projection device26,28about the image recording region. A plurality of projection profiles can form a projection data set. A tomographic image of the region to be mapped can be reconstructed on the basis of a projection data set.

The imaging device1has a control device36for controlling the imaging device1. The imaging device1also has an input unit38for inputting control information, for example, imaging parameters, and examination parameters and an output unit39for outputting control information and images, in particular an inventively generated image.

The detector28has detector elements DEL. The detector elements DEL form a first group G1of detector units and a second group G2of detector units. The imaging device1has a data processing unit according to one embodiment of the invention, for example the data processing unit35shown inFIG. 6and/orFIG. 7, wherein the data processing unit has the first group G1of detector units and the second group G2of detector units.

FIG. 9shows a first example G11, a second example G12and a third example G13for the first group G1of detector units.FIG. 9shows, in particular, the assignment of the detector elements DEL in respect of the first group G1and first detector units DET1.

FIG. 10shows a first example G21, a second example G22and a third example G23for the second group G2of detector units.FIG. 10shows, in particular, the assignment of the detector elements DEL in respect of the second group G2and second detector units DET2.

The first groups G11, G12, G13each have a first plurality of first detector units DET1, wherein the first detector units DET1each have more than a given number of detector elements DEL. The second groups G2each have a second plurality of second detector units DET2, wherein the second detector units DET2each have, at most, the given number of detector elements DEL. The first detector units DET1and the second detector units DET2are illustrated by hatched areas bordered by closed lines.

The first group G11has a plurality of third detector units DET3which each have, at most, the given number of detector elements DEL. The second group G21has a fourth detector unit DET4which comprises more than the given number of detector elements DEL. The third detector units DET3and the fourth detector unit DET4are illustrated by hatched areas bordered by broken lines. The first group G12comprises the first plurality of first detector units DET1. The second group G22comprises the second plurality of second detector units DET2. In the first group G13the first detector units DET1each have nine detector elements DEL. In the second group G23the second detector units DET2each have one detector element DEL.

The detector elements DEL shown inFIG. 9andFIG. 10can optionally be assigned, in particular are assigned, to both a first detector unit DET1and a second detector unit DET2.

One or more of the detector element(s) DEL shown inFIG. 9andFIG. 10can optionally be assigned, in particular is/are assigned, to a plurality of first detector units DET1and to a plurality of second detector units DET2. For example, the detector element DELX is assigned to a plurality of first detector units DET1and to a plurality of second detector units DET2.

The assignment of detector elements DEL in particular to first detector units DET1and second detector units DET2can optionally be set in accordance with the needs of the user and/or the requirements of the examination, for example via an assignment stage. For example, the assignment in a first operating state of the assignment stage can produce the first group G11and the second group G21, in a second operating state of the assignment stage the first group G12and the second group G12, and in a third operating state of the assignment stage the first group G13and the second group G23.

Reference is made to the fact that the use of the indefinite article “a” or “an” does not prevent the relevant features from also being present multiple times. Similarly, the term “unit” does not prevent this from comprising a plurality of components which may optionally also be spatially distributed.

Reference is made to the fact that the described methods and the described data processing unit as well as the described imaging device are merely preferred example embodiments of the invention and that the invention can be varied by a person skilled in the art, without departing from the scope of the invention provided it is specified by the claims.

The example embodiment or each example embodiment should not be understood as a restriction of the invention. Rather, numerous variations and modifications are possible in the context of the present disclosure, in particular those variants and combinations which can be inferred by the person skilled in the art with regard to achieving the object for example by combination or modification of individual features or elements or method steps that are described in connection with the general or specific part of the description and are contained in the claims and/or the drawings, and, by way of combinable features, lead to a new subject matter or to new method steps or sequences of method steps, including insofar as they concern production, testing and operating methods. Further, elements and/or features of different example embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims.

Further, at least one embodiment of the invention relates to a non-transitory computer-readable storage medium comprising electronically readable control information stored thereon, configured in such that when the storage medium is used in a controller of a magnetic resonance device, at least one embodiment of the method is carried out.