Magnetic resonance system

Abstract

Magnetic resonance system for generating magnetic resonance data of a flowing fluid, the magnetic resonance system (1) comprising: - a data acquisition unit (5) for acquiring first magnetic resonance data, wherein the data acquisition unit (5) is adapted to carry out a plurality of magnetic resonance measurements, wherein in each magnetic resonance measurement first magnetic resonance data are measured by a) at different first times in a first region, the fluid is either magnetically marked or not marked to produce a flowing sequence (10) of marking and / or non-marking regions (L, C), and b) at a second time in a second region at which the fluid flows from the first region, the first magnetic resonance data indicative of the generated sequence (10) of marking and / or non-marking regions (L, C) are measured, - an evaluation unit (7) for evaluating the first magnetic resonance data measured in the various magnetic resonance measurements, wherein the evaluation unit (7) is adapted, based on a combination of the first magnetic resonance data measured in the various magnetic resonance measurements, to determine second magnetic resonance data which are each indicative of a combination marking region composed of a plurality of marking regions generated at different first times and flowed to the second region and a time interval between one of the first times and the second time, wherein the evaluation unit (7) is further adapted to determine second magnetic resonance data, each of which is indicative of a marking region generated at a specific first point in time and flowed to the second region, based on a combination of the first magnetic resonance data measured in the various magnetic resonance measurements, wherein the evaluation unit (7) is adapted such that, for determining the second magnetic resonance data, which are each indicative of a combination marking region composed of a plurality of marking regions generated at different first times and flowed to the second region, and a time interval between one of the first times and one of the second times, based on a combination of the first magnetic resonance data measured in the various magnetic resonance measurements, fewer first magnetic resonance data are combined than for determining the second magnetic resonance data, which are each indicative of a marking region generated at a specific first time and flowed to the second region.

Description

[0001] The invention relates to a magnetic resonance system (MR system), an MR method, and a computer program for generating MR data of a flowing fluid. The invention further relates to an evaluation system, an evaluation method, and a computer program for evaluating MR data of a flowing fluid. The fluid is preferably blood.

[0002] US patent US 8260396 B2 (Guenther 2012) discloses an MR system that labels blood boluses in vivo using an arterial MR spin labeling process, generating different combinations of control and labeling regions for different time steps and MR images for each time step and thus for each combination of control and labeling regions. These MR images are then combined to generate combination MR images, each corresponding to a selected blood bolus. Further prior art includes: DE 10 2007 028 901 A1, US 2012 / 0296193 A1, US 6 564 080 B1, and US 2009 / 0149733 A1.

[0003] It is an object of the present invention to provide an MR system, an MR method and an associated computer program that enable the generation of MR data of a flowing fluid to be improved.

[0004] The object is achieved by an MR system for generating MR data of a flowing fluid according to claim 1, wherein the MR system comprises: - a data acquisition unit for acquiring first MR data, wherein the data acquisition unit is adapted to perform a plurality of MR measurements, wherein in each MR measurement first MR data are measured by a) at different first times in a first region, the fluid is either magnetically marked or not marked to produce a flowing sequence of marked and / or non-marked regions, and b) at a second time in a second region at which the fluid flows from the first region, the first MR data indicative of the generated sequence of marking and / or non-marking regions are measured, - an evaluation unit for evaluating the first MR data measured in the various MR measurements, wherein the evaluation unit is adapted, based on a combination of the first MR data measured in the various MR measurements, to determine second MR data which are each indicative of a combination marking region composed of a plurality of marking regions generated at different first times and flowed to the second region and a time interval between one of the first times and the second time.

[0005] By combining the first MR data measured in the various MR measurements in such a way that second MR data are determined, each of which is indicative of a combination marking region composed of several marking regions generated at different first points in time and flowing to the second region, and a time interval between one of the first points in time and the second point in time, it is possible to obtain information about the flow behavior of the fluid before all of the first MR data have been measured. Therefore, for example, it is not necessary to wait for an entire measurement process and only then determine the second MR data. In this sense, in particular, the MR system can improve the generation of MR data of a flowing fluid.

[0006] The flowing fluid is preferably blood. However, the flowing fluid can also be another liquid or gaseous substance, for example, another body fluid. The first MR data are preferably two-dimensional or three-dimensional MR images.

[0007] The evaluation unit is further adapted to determine second MR data, each indicative of a marking region generated at a specific first time and flowed to the second region, based on a combination of the first MR data measured in the various MR measurements. Furthermore, the evaluation unit is adapted such that, to determine the second MR data, each indicative of a combination marking region composed of multiple marking regions generated at different first times and flowed to the second region, and a time interval between one of the first times and one of the second times, fewer first MR data are combined than for determining the second MR data, each indicative of a marking region generated at a specific first time and flowed to the second region.This means that if, for example, some first MR data should be erroneous, for example because a patient has moved, so that second MR data, each indicative of a marking region generated at a specific first time and flowed to the second region, cannot be determined, second MR data could nevertheless be determined, each indicative of a combination marking region composed of several marking regions generated at different first times and flowed to the second region and a time interval between one of the first times and the second time.In addition, in principle, even before all first MR data have been measured that are required to determine the second MR data, each of which is indicative of a marking region generated at a specific first time and flowed to the second region, second MR data could be determined, each of which is indicative of a combination marking region composed of several marking regions generated at different first times and flowed to the second region and a time interval between one of the first times and the second time.It is conceivable, for example, that the second MR data are determined in real time during the measurement, each of which is indicative of a combination marking region composed of several marking regions generated at different first points in time and flowed to the second region, and of a time interval between one of the first points in time and the second point in time.

[0008] The MR system preferably comprises a matrix provision unit for providing a two-valued determination matrix, wherein a row of the determination matrix represents a sequence of marking and / or non-marking regions, and wherein different rows of the determination matrix correspond to different MR measurements. The evaluation unit is adapted to a) form a vector, wherein a vector element is formed by an MR value of the first MR data and different vector elements correspond to different MR measurements, b) invert the determination matrix, and c) determine the second MR data by applying the inverted determination matrix to the vector. The entries of a two-valued determination matrix have only two values, for example +1 and -1, representing marking and non-marking regions.A first MR value, i.e., an MR value of the first MR data that forms a vector element, is preferably an image value, in particular a voxel value or a pixel value, of a first MR image. This means that the second MR data can be determined pixel by pixel or voxel by voxel, with a vector being formed for each pixel or for each voxel of the different first MR images, which in this example represent the first MR data. For example, a vector is formed for the pixel at location (1,1), which vector includes the corresponding image values ​​at locations (1,1) of the first MR images acquired at different times.

[0009] It is preferred that there is a complementary sequence for each sequence of marking and / or non-marking regions, wherein a first sequence is complementary to a second sequence if a non-marking region is arranged at each location in the first sequence that corresponds to a location in the second sequence at which a marking region is arranged, and vice versa. It is further preferred that the data acquisition unit is adapted to perform MR measurements having complementary sequences immediately one after the other. This means that in one embodiment, after a first MR measurement with a first sequence, a second MR measurement is performed with a second sequence that is complementary to the first sequence, after which third and fourth MR measurements are performed with third and fourth sequences, the fourth sequence being complementary to the third sequence, and so on.

[0010] In one embodiment, the MR system comprises a matrix providing unit for providing a two-valued first determination matrix, wherein the two-valued first determination matrix has only two values ​​that represent marking and non-marking regions, wherein the rows of the first determination matrix represent a first group of sequences of marking and / or non-marking regions, and wherein different rows of the first determination matrix correspond to different MR measurements, wherein the matrix providing unit is further adapted to provide a two-valued second determination matrix, wherein the two-valued first determination matrix has only two values ​​that represent marking and non-marking regions, wherein the rows of the second determination matrix represent a second group of sequences of marking and / or non-marking regions that are complementary to the sequences of the first group,and wherein different rows of the second determination matrix correspond to different MR measurements, wherein the evaluation unit is adapted to a) form a first vector, wherein a vector element of the first vector is formed by an MR value of the first MR data and different vector elements of the first vector correspond to different MR measurements, which in turn correspond to different sequences of the first group, b) form a second vector, wherein a vector element of the second vector is formed by an MR value of the first MR data and different vector elements of the second vector correspond to different MR measurements, which in turn correspond to different sequences of the second group, c) invert the first determination matrix and the second determination matrix, and d) determine the second MR data,by applying the inverted first determination matrix to the first vector and the inverted second determination matrix to the second vector. The first determination matrix is ​​preferably formed by a Hadamard matrix, and the second determination matrix is ​​preferably formed by a complementary Hadamard matrix.

[0011] Preferably, the data acquisition unit is adapted to perform MR measurements sequentially ordered according to the number of changes between marking and non-marking regions in the corresponding sequence. The MR measurements are preferably ordered sequentially according to a Walsh sort. This means that the determination matrix described above preferably has rows arranged according to the Walsh sort.

[0012] In a preferred embodiment, the evaluation unit is adapted to determine addition and / or subtraction data by adding and / or subtracting first MR data measured in different MR measurements from one another, and to determine the second MR data based on the addition and / or subtraction data. This means, for example, that corresponding pixel values ​​or voxel values ​​from first MR images of different MR measurements are added and / or subtracted to determine the second MR data, which are each indicative of a combination marking region composed of several marking regions generated at different first times and flowed to the second region, and a temporal interval between one of the first times and the second time.

[0013] The above-mentioned object of improving the generation of MR data of a flowing fluid is further achieved by an evaluation system for evaluating MR data of a flowing fluid according to claim 8, wherein the evaluation system comprises: - a data provision unit for providing first MR data, wherein the data provision unit is adapted to provide first MR data of a plurality of MR measurements, wherein in each MR measurement first MR data were measured by a) at different first times in a first region, the fluid was either magnetically marked or unmarked to produce a flowing sequence of marked and / or unmarked regions, and b) at a second time in a second region at which the fluid flows from the first region, the first MR data indicative of the generated sequence of marking and / or non-marking regions were measured, - an evaluation unit for evaluating the first MR data measured in the various MR measurements, wherein the evaluation unit is adapted to determine second MR data which are each indicative of a combination marking region composed of a plurality of marking regions generated at different first times and flowed to the second region and a time interval between one of the first times and the second time, based on a combination of the first MR data measured in the various MR measurements.

[0014] The above object is further achieved by an MR method for generating MR data of a flowing fluid according to claim 9, the MR method comprising: - Acquiring first MR data, wherein several MR measurements are performed and wherein first MR data are measured in each MR measurement by a) at different first times in a first region, the fluid is either magnetically marked or not marked to produce a flowing sequence of marked and / or non-marked regions, and b) at a second time at a second location to which the fluid flows from the first region, the first MR data indicative of the generated sequence of marking and / or non-marking regions are measured, - Evaluating the first MR data measured in the various MR measurements, wherein the evaluation unit is adapted to determine second MR data which are each indicative of a combination marking region composed of a plurality of marking regions generated at different first times and flowed to the second region and a time interval between one of the first times and the second point, based on a combination of the first MR data measured in the various MR measurements.

[0015] The above-mentioned object is further achieved by an evaluation method for evaluating MR data of a flowing fluid according to claim 10, wherein the evaluation method comprises: - Providing first MR data, wherein first MR data of several MR measurements are provided, wherein in each MR measurement first MR data were measured by a) at different first times in a first region, the fluid was either magnetically marked or unmarked to produce a flowing sequence of marked and / or unmarked regions, and b) at a second time in a second region at which the fluid flows from the first region, the first MR data indicative of the generated sequence of marking and / or non-marking regions were measured, - Evaluating the first MR data measured in the various MR measurements, wherein second MR data are determined, each of which is indicative of a combination marking region composed of a plurality of marking regions flown to the second region at different first times and a time interval between one of the first times and the second point, based on a combination of the first MR data measured in the various MR measurements.

[0016] The above-mentioned object is further achieved by a computer program for generating MR data of a flowing fluid, wherein the computer program comprises program code means which result in the MR system according to claim 1 carrying out the MR method according to claim 9 when the computer program is executed on a computer which controls the MR system.

[0017] The above-mentioned object is further achieved by a computer program for evaluating MR data of a flowing fluid, wherein the computer program has program code means which result in the evaluation system according to claim 8 carrying out the evaluation method according to claim 10 when the computer program is executed on a computer which controls the evaluation system.

[0018] It should be understood that the MR system according to claim 1, the evaluation system according to claim 8, the MR method according to claim 9, the evaluation method according to claim 10 and the computer programs according to claims 11 and 12 have similar and / or identical preferred embodiments, as particularly defined in the dependent claims.

[0019] It should also be understood that a preferred embodiment of the present invention may be formed by any combination of the dependent claims and / or the embodiments mentioned in the present application with the respective independent claims.

[0020] Embodiments of the invention are described with reference to the following figures, wherein Fig. 1 schematically and exemplarily shows an embodiment of an MR system, Fig. 2 schematically and exemplarily shows different sequences of marking and non-marking areas and second MR data, Fig. 3 schematically and exemplarily shows an embodiment of an evaluation system for evaluating first MR data and Fig. 4 shows a flow chart illustrating an exemplary MR procedure.

[0021] Fig. 1 schematically shows, by way of example, an embodiment of an MR system. The MR system comprises a data acquisition unit 5 for acquiring first MR data of a patient 3 arranged on a patient couch 2. In this embodiment, the data acquisition unit 5 is configured to perform multiple MR measurements in the head region 4 of the patient 3. In each MR measurement, first MR data are measured by a) at various first points in time in a first region, either magnetically marking or not marking the blood of the patient 3 in order to generate a flowing sequence of marking and / or non-marking regions, and b) at a second point in time in a second region to which the blood flows from the first location, the first MR data, which are indicative of the generated sequence of marking and / or non-marking regions, are measured.The MR system 1 further comprises an evaluation unit 7 for evaluating the first MR data measured in the various MR measurements. The evaluation unit 7 is adapted to determine second MR data, each indicative of a combination marking region composed of a plurality of marking regions flown to the second region at different first times and a time interval between one of the first times and the second time, based on a combination of the first MR data measured in the various MR measurements. The evaluation unit 7 is further adapted to determine second MR data, each indicative of a marking region generated at a specific first time and flown to the second region, based on a combination of the first MR data measured in the various MR measurements. In this embodiment, the first and second MR data are MR images.

[0022] The MR system 1 further comprises a matrix provision unit 6 for providing a two-valued determination matrix, wherein a row of the determination matrix is ​​formed by a sequence of marking and / or non-marking regions, and wherein different rows of the determination matrix correspond to different MR measurements. The evaluation unit 7 is adapted to form a vector, wherein a vector element is formed by a first MR value, which in this embodiment corresponds to an image value, and different vector elements correspond to different MR measurements. The evaluation unit 7 is further adapted to invert the determination matrix and determine the second MR data by applying the inverted determination matrix to the vector.

[0023] In this embodiment, 16 MR measurements are performed, with each MR measurement containing a sequence of eight marking and / or non-marking regions. The sequences of MR measurements can be represented, for example, by the following matrix: M=[+1+1+1+1+1+1+1+1−1−1−1−1−1−1−1−1+1+1+1+1−1−1−1−1−1−1−1−1+1+1+1 +1+1+1−1−1−1−1+1+1−1−1+1+1+1+1−1−1+1+1−1−1+1+1−1−1−1−1+1+1−1−1+1+ 1+1−1−1+1+1−1−1+1+1−1−1+1+1−1−1+1+1−1−1+1+1−1−1+1+1−1−1+1+1−1−1+1+1−1−1+1+1−1+1−1+1−1+1−1+1−1+1−1+1−1+1−1+1−1+1]

[0024] Here, "-1" denotes a non-marking region and "+1" denotes a marking region. The matrix M has a complementary sequence for each sequence, i.e., for each row, with complementary sequences arranged directly one after the other. Furthermore, the individual sequences are sorted according to the number of alternations between marking and non-marking regions. This means that the rows of the matrix M are preferably Walsh-sorted. Walsh sorting is disclosed, for example, in Wolfram, S., 2002. A new kind of science 1st ed., Wolfram Media, Inc., and Wang, R., 2013. Sequency Ordered Walsh-Hadamard Matrix, http: / / fourier.eng.hmc.edu / e161 / lectures / wht / node3.html (Wolfram 2002).

[0025] The matrix M can be formed by combining a first determination matrix, which in this example is a Hadamard matrix, with a second determination matrix, which in this example is a complementary Hadamard matrix, wherein the rows of the Hadamard matrix and the complementary Hadamard matrix are used alternately to generate the matrix M. The individual sequences of marking and non-marking regions corresponding to the individual rows of the matrix M are shown schematically and by way of example in the Fig. 2 illustrated. Fig. Figure 2 shows 16 sequences 10 of marking areas L and non-marking areas C, which could also be considered control areas. In Fig. 2, the sequences indexed with odd numbers, which can also be called sequences of a first group, correspond to rows of the Hadamard matrix and the sequences indexed with even numbers, which can also be called sequences of a second group, correspond to rows of the complementary Hadamard matrix.

[0026] The second MR data, each indicative of a marking region generated at a specific first time and streamed to the second region, are preferably determined voxel by voxel. This means that the first MR data are preferably first MR images with different voxels, with a first vector and a second vector being formed for each voxel.A vector element of the first vector is formed by a voxel value of a first MR image, wherein different vector elements of the first vector correspond to different MR measurements, which in turn correspond to different sequences of the first group. A vector element of the second vector is formed by a voxel value of a second MR image, wherein different vector elements of the second vector correspond to different MR measurements, which in turn correspond to different sequences of the second group. For example, a first vector for the voxel (1,1,1) has the voxel values ​​for this voxel in the different first MR images that were generated in the different MR measurements that correspond to the different sequences of the first group. Therefore, second MR data, i.e.Voxel values ​​for the corresponding voxel, each indicative of a marking region generated at a specific first time and streamed to the second region, are determined by multiplying the inverse first determination matrix by the first vector and the inverse second determination matrix by the second vector for each voxel. The two resulting vectors can be averaged, for example, with the resulting averaged vector representing the second MR data, for example, for voxel (1,1,1).

[0027] Furthermore, the evaluation unit 7 is adapted such that, for determining the second MR data, which are each indicative of a combination marking region composed of several marking regions generated at different first points in time and flowed to the second region, and a time interval between one of the first points in time and the second point in time, fewer first MR data are combined than for determining the second MR data, which are each indicative of a marking region generated at a specific first point in time and flowed to the second region, i.e., a single marking region. This will be explained below with reference to Fig. 2 is explained as an example.

[0028] In this exemplary embodiment, the evaluation unit 7 subtracts the first MR image of the first MR measurement from the first MR image of the second MR measurement to generate the second MR image 30, i.e., corresponding second MR data. The second MR image 30 is indicative of a combination marking region, which could also be understood as a combination bolus and which is formed from all eight marking regions, and of the time interval between the second time at which the first MR images were acquired and the time, for example, of the first marking region 48, which could also be referred to as a sub-bolus. The second MR images 31, 32, 33 correspond to a combination marking region formed from four individual marking regions. The second MR image 31 was generated by subtracting the first MR image of the fourth MR measurement from the first MR image of the first MR measurement.The second MR image 32 was generated by subtracting the first MR image of the fifth MR measurement from the first MR image of the first MR measurement, and the second MR image 33 was generated by subtracting the first MR image of the third MR measurement from the first MR image of the first MR measurement. The second MR image 31 corresponds to a time interval between the second time and the time of the marking region 49. The second MR image 32 corresponds to a time interval between the second time and the time of the marking region 50, and the second MR image 33 corresponds to a time interval between the second time and the time of the marking region 48.

[0029] A method for determining the second MR images from the first MR images for matrices of any size, and according to which, for example, images 30-48 were also determined, can be as follows. First, for each second MR image, which is indicative of a marking region generated at a specific first time and streamed to the second region (i.e., a single marking region), it is written down symbolically, i.e., written in symbols, how these second MR images b1, ..., b N from first MR images v1, ... v N put together.

[0030] For example, using the first group of matrix (1) (the same procedure can be used for the second group): b2=18(v1+v2+v3+v4−v5−v5−v7−v8)

[0031] It is important to note that this step can be performed symbolically even before the first MR data is generated, and no second MR images are generated. The symbolic representation of the individual marking regions serves only to derive arithmetic calculation rules for the second MR images, each of which is indicative of a combination marking region generated at a specific first time point and flowed to the second region.

[0032] In a second step, the b i symbolically by adding and / or subtracting all desired second MR data K l The procedure is such that the marking areas for the b i Indicative are the combination marking areas for which the K lare indicative. From this symbolic notation, after deleting all summing elements that cancel out to zero, the arithmetic calculation rule for the desired combination marking range results.

[0033] For example, using the first group of matrix (1) (the same procedure can be used for the second group): b2+b3=18((v1+v2+v3+v4−v5−v6−v7−v8)+(v1+v2−v3−v4−v5−v6+v7+v8))=14(v1+v2−v5−v6) or b5+b6+b7+b8=12(v1−v2)

[0034] If, for example, second MR images are also to be determined that are indicative of the first marking region or combination marking regions that contain the first marking region, the first MR images are combined from the first and second vectors. In the following, the first marking region in this example refers to the marking region that has the greatest time interval between its generation and the second time, and the last marking region in this example refers to the marking region that has the shortest time interval between its generation and the second time. To determine the first marking region, the summands with a negative sign are replaced by the entries of the second vector v in the calculation rule for the second MR images that are indicative of the last marking region. kwith the same indices. Similarly, the calculation rules for determining second MR data indicative of combination areas containing the first marking area can be adapted.

[0035] For example, using the first and second group of matrix (1): b1+b2+b3+b4=12(v1−v2k)

[0036] In this example, the determination of second MR data indicative of the first marking region or combination marking regions containing the first marking region was only made possible by combining the information of the determination matrix and the complementary determination matrix.

[0037] The second MR images, i.e., the second MR data corresponding to combination marking regions, are generated using fewer first MR data than the second MR data corresponding to individual marking regions. In particular, second MR data are determined for each of the eight marking regions, i.e., for the associated eight first points in time, by combining at least eight first MR images, in particular all 16 first MR images corresponding to the 16 sequences 10, using the aforementioned first and second determination matrices. In contrast, only two first MR images, for example, are required to determine the second MR data corresponding to the combination marking regions. The second MR data corresponding to combination marking regions can therefore be generated even if not all 16 first MR images have been acquired.This means that the second MR images corresponding to the combination marking regions can be generated before all 16 first MR images have been measured. For example, second MR images can be generated, particularly in real time, during the measurement of the 16 first MR images. Furthermore, the second MR images can be generated even if, for example, all 16 first MR images could not be measured due to image artifacts or other interference.

[0038] Using the second MR images, for example, an MR signal can be determined at different time points, thus determining the signal profile over time voxel-by-pixel. From these signal-time curves, various parameters relevant for clinical diagnosis can then be determined voxel-by-pixel. Examples of this are described in Buxton, RB et al., 1998. A general kinetic model for quantitative perfusion imaging with arterial spin labeling. Magnetic Resonance in Medicine, 40(3), pp. 383-96.

[0039] The Fig. The MR system 1 shown in Figure 1 further comprises a control unit 8 adapted to control the various units of the MR system 1, and an input unit 9 such as a keyboard, a computer mouse, a touchscreen, etc. Furthermore, the MR system 1 includes an output unit 25 such as a monitor.

[0040] In the following, an MR method for generating MR data of a flowing fluid will be described with reference to a flowchart shown in Fig. 3 is shown.

[0041] In step 101, first MR data are acquired, wherein multiple MR measurements are performed, and wherein first MR data are measured in each MR measurement. In particular, a first MR image is generated in each MR measurement to measure first MR data. During the generation of the first MR data, the fluid is either magnetically marked or unmarked at various first points in time in a first region in order to generate a flowing sequence of marking and / or non-marking regions. Furthermore, at a second point in time in a second region to which the fluid flows from the first region, the first MR data, which are indicative of the generated sequence of marking and / or non-marking regions, are measured. This means that in each MR measurement, a respective sequence of marking and / or non-marking regions is generated, and for each of these sequences, a first MR image is preferably generated as a measurement of the first MR data.

[0042] In addition, in step 101, second MR data are determined, each of which is indicative of a combination marking region composed of several marking regions generated at different first times and flowed to the second region, and a temporal interval between one of the first times and the second time by combining the first MR data measured in the various MR measurements. Since not all of the first MR data are necessary to determine these second MR data, second MR data for the combination marking regions can already be determined during the acquisition of the first MR data—that is, in this exemplary embodiment, the first MR images.

[0043] After the measurement of the first MR data is completed, these can also be used in step 102 to determine second MR data, each of which is indicative of an individual marking region generated at a specific first time point and flowed to the second region.

[0044] Fig. 4 schematically shows, by way of example, an evaluation system for evaluating MR data of a flowing fluid. The evaluation system 20 comprises a data provision unit 21 for providing first MR data, wherein the data provision unit 21 is adapted to provide first MR data from multiple MR measurements, and wherein in each MR measurement, first MR data were measured by a) at various first points in time in a first region, the fluid was either magnetically marked or not marked in order to generate a flowing sequence of marking and / or non-marking regions, and b) at a second point in time in a second region, at which the fluid flows from a first region, the first MR data, which are indicative of the generated sequence of marking and / or non-marking regions, were measured.The evaluation system 20 further comprises an evaluation unit 22, which corresponds to the above-described evaluation unit 7 of the MR system 1, for evaluating the first MR data measured in the various MR measurements. The evaluation unit 22 is adapted to determine second MR data, each of which is indicative of a combination marking region composed of several marking regions generated at different first times and flowed to the second region, and a time interval between one of the first times and the second time, based on a combination of the first MR data measured in the various MR measurements.The evaluation unit 22 is preferably also adapted to determine second MR data, each of which is indicative of a marking region generated at a specific first time and flowed to the second region, based on a combination of the first MR data measured in the various MR measurements. Furthermore, the evaluation system 20 comprises an input unit 23, such as a keyboard, a computer mouse, or a touchscreen, and an output unit 24, such as a monitor.

[0045] Although in the embodiments described above the first MR data were measured only at a second time point, in other embodiments the first MR data may also be measured at a plurality of different second time points.

[0046] For example, first MR data in each MR measurement can also be acquired at several second time points t1 <t2<t3<... gemessen werden. Für jeden Zeitpunkt t iSecond MR data can then be generated. This would allow, for example, the signal intensity to be determined at more time points—namely, the product of the number of second time points and the number of second MR data—than would be possible with a measurement at just one second time point. This would provide more data points for a signal-time curve, which could, for example, improve fitting.

[0047] Some exemplary explanations of individual aspects of the invention follow.

[0048] For example, the data acquisition unit can be adapted to cause a rotation of the blood magnetization by a desired angle in order to mark the blood at a first point in time and in a selected section. In one exemplary embodiment, the magnetization resulting from the spins of the protons in the blood is rotated (inverted) by 180° from the relaxed state (0°). This is referred to here as marking or labeling. In this way, a clearly defined length section of the flowing blood (bolus, marking area) is created. The blood with inverted magnetization locally changes the magnetic properties wherever it flows and thus the contrast of an MR image generated after labeling (label image). Since these changes are very small and not visible to the naked eye, an additional image without prior labeling, the so-called control image, is generated.For example, the difference between the label and control images makes the effects of perfusion and / or flow visible and, if necessary, quantifiable. In another exemplary embodiment, instead of inversion, a saturation (rotation by 90°) of the magnetization is achieved.

[0049] The rotation (also called tilt or flip) of the magnetization can be achieved, for example, using radiofrequency pulses (RF pulses). An example of such RF pulses is described in Payne, GS & Leach, MO, 1997. Implementation and evaluation of frequency offset corrected inversion (FOCI) pulses on a clinical MR system. Magnetic resonance in medicine, 38(5), pp. 828-33 and Dai, W. et al., 2008. Continuous flow-driven inversion for arterial spin labeling using pulsed radio frequency and gradient fields. Magnetic resonance in medicine, 60(6), pp. 1488-97.

[0050] This blood marking technique can, for example, be used to create not just a single marking or non-marking region before measuring an MR image. Rather, sequences of marking and non-marking regions can be created, and multiple MR measurements can be performed consecutively, potentially generating a different sequence of marking and non-marking regions in each measurement. The specific form of these sequences can be specified, for example, in the form of a matrix, where the matrix entries specify the type of marking (e.g., marked or unmarked), and each row of the matrix corresponds to an MR measurement.

[0051] For an example description of the generation of initial MR data, see Gadian, DG, 1996. NMR & Its Applications to Living Systems 2 Sub., Oxf.UP; Bernstein, M., King, K. & Zhou, X., 2004. Handbook of MRI pulse sequences, Academic Press. For further details of the labeling process and the generation of initial MR data, see Williams, DS et al., 1992. Magnetic resonance imaging of perfusion using spin inversion of arterial water. Proceedings of the National Academy of Sciences of the United States of America, 89(1), pp. 212-6; Detre, J., Leigh, J. & Williams, D., 1996. Perfusion imaging. Magnetic Resonance in Medicine, 35(1), pp. 70-9; Günther, M., 2007. Habilitationsschrift. Ruprechts-Karl-Universität Heidelberg (Günther 2007) and Günther, M., Oshio, K. & Feinberg, DA, 2005. Single-shot 3D imaging techniques improve arterial spin labeling perfusion measurements. Magnetic resonance in medicine, 54(2), pp. 491-498.

[0052] For example, to obtain second MR data indicative of a combination marking region (hereinafter also referred to as second MR combination data), only subsets of all first MR data can be used from the first MR data, and these can still be relevant for clinical diagnosis. In other words, in this example, fewer first MR data are required to reconstruct second MR combination data than to reconstruct second MR data based on individual marking regions (hereinafter referred to as second individual MR data). This is based, for example, on the following observation. If the calculation of the second MR combination data from second individual MR data is written down arithmetically in symbols, this observation becomes clear.If, in this calculation, the second individual MR data are written, again in symbols, as a combination of addition and subtraction of the first MR data, it results that some of the first MR data calculate pairwise to zero. From this representation, it follows that the second MR combination data can be described as a combination of addition and subtraction of subsets of first MR data and that fewer first MR data are required to determine second MR combination data than to determine second individual MR data. In the sense of this example, the second MR combination data are generated directly from the first MR data (and not via the detour of generating second individual MR data). This can be advantageous compared to the prior art because, for example, the calculation of second MR combination data performed in the evaluation unit can be accelerated.This is because the detour via calculation of the second individual MR data is no longer necessary, as in (Günther 2007). The second individual MR data therefore only need to be generated when the highest possible temporal resolution is required. Furthermore, the robustness of the measurement can be increased. If, for example, some initial MR data are faulty, e.g., because a patient has moved, or are unavailable, the second individual MR data may not be determined or may only be determined incorrectly. Nevertheless, second combined MR data could still be determined from the intact and available initial MR data.

[0053] For example, if the determination matrix is ​​invertible, meaning its inverse matrix can be determined, it is possible to determine second MR individual and combination data using this matrix and the vector consisting of first MR values. However, other exemplary methods for determining second MR individual and combination data from first MR data are also conceivable. One example is the exemplary arithmetic representation of the second MR combination data explained above as a symbolically written combination of addition and / or subtraction of first MR data.

[0054] An example of a conceivable determination matrix is ​​the Hadamard matrix, which is described in (Guenther 2012) or (Wolfram 2002), among others.

[0055] For example, when selecting the determination matrices for an original matrix, the matrix complementary to it (complementary matrix), in which marked and unmarked states are interchanged, can also be considered. This has the following advantage over the prior art, for example: Usually, only N-1 second MR data can be determined from N first MR data; for example, second MR data indicative of the first marking region cannot be generated. However, using the information from the original matrix and the complementary matrix, second individual MR data indicative of all N marking regions can be generated. Furthermore, second MR combination data indicative of combination marking regions that would contain the first marking region can also be generated from the first MR data.This can, for example, also allow the generation of second MR combination data from two MR measurements, that of the first row of the original matrix and that of the first row of the complementary matrix, which are indicative of the combination marking region consisting of all N marking regions. Another conceivable implementation of the determination matrix could be such that only certain rows of an original matrix alternate with the rows of its complementary matrix. The remaining rows of the original matrix would then be non-alternating in the determination matrix and in the order in which they appear in the original matrix. The remaining rows of the complementary matrix would also be located at another location in the determination matrix, non-alternating and in the order in which they appear in the complementary matrix.

[0056] An example of ordering based on the number of transitions between marking and non-marking regions is so-called sequence sorting. Here, the rows are ordered according to their sequence, and the sequence is defined as the number of sign changes (i.e., zero crossings) of the row's entries. In the case of sequence-sorted Hadamard matrices, this can also be referred to as a Walsh sort (see, for example, (Wolfram 2002)). Using a sequence-sorted determination matrix, for example, the sequence of MR measurements can be reordered so that the first MR data required to generate second MR combination data are measured as early as possible.One advantage of this compared to the state of the art is, for example, that second MR combination data could be determined before all of the first MR data required to determine the second individual MR data have been measured, and this second combination data is already relevant for clinical diagnostics. For example, it is conceivable that the second MR combination data could be determined in real time during the measurement. If the first MR data are generated in a suitable sequence, second MR combination data could be generated from them during the measurement. This allows, for example, the medical personnel accompanying the measurement to receive initial information at a very early stage of the examination. If necessary, the ongoing measurement can then be modified and / or further diagnostic steps can be planned. Here, too, the robustness of the measurement can be increased.Patient movements, which can render the images unusable, typically increase with acquisition time. Therefore, if the subsets of the first MR data that already allow the generation of second MR combination data are generated as early as possible, the probability that all second single MR and / or combined MR data cannot be generated or can only be generated incorrectly due to patient movement is reduced.

[0057] In other words, it can be said that, for example, it is possible to select the sequence of MR measurements and / or evaluation steps such that the second MR data are determined first, which can be generated from the smallest possible number of first MR data. This number can even be minimal.

[0058] A general example of a Walsh sort is given below. Walsh sort can be performed in three steps. To do this, a given sequence S is first written as a binary number (also called a dual number): S=(Sn−1Sn−2…S1S0)2=∑i=0n−1Si2i

[0059] This number in binary code is then converted to Gray code: gi=Si⊕Si+1,i∈[0,n−1],Sn≡0

[0060] Where ⊕ stands for the exclusive or.

[0061] By a bit reversal ki=gn−1−i are then made from the g i 's the binary values ​​k i The row number k of the Hadamard matrix corresponding to the sequence can then be determined from the binary representation k=(kn−1kn−2...k1k0)2=∑i=0n−1ki2i be determined. If the rows k of the Hadamard matrix are arranged such that the sequences S belonging to the k are in ascending or descending order, the matrix is ​​called Walsh-sorted.

[0062] In particular for N=8 the steps are: S 0 1 2 3 4 5 6 7 Binär 000 001 010 011 100 101 110 111 Gray code 000 001 011 010 110 111 101 100 Bit-reverse 000 100 110 010 011 111 101 001 k 0 4 6 2 3 7 5 1

[0063] For example, if quantitative perfusion data are also to be determined (see for example (Buxton et al. 1998)), the evaluation unit can also enable further arithmetic operations for further image processing.

[0064] For the sake of completeness, reference is made to the following literature.

[0065] US patent US 8,260,396 B2 discloses an MR system that magnetically labels blood in vivo within predeterminable spatial sections of the vessels. This is done using an arterial MR spin labeling process, also known as arterial spin labeling (ASL). These sections are called subboli (sing. subbolus) and represent spatially defined regions of either labeled or unlabeled blood within a vessel. These can be seen as examples of a possible realization of labeling or non-labeling regions. In the MR system described in (Guenther 2012), different combinations of subboli are generated at an initial time, and for each of these combinations, initial MR images are acquired after a waiting time (often referred to as post-labeling delay (PLD)).These first MR images are then combined to generate second MR element images, each indicative of a marker region generated at a specific first time point and flowed to the second region. These second element images each correspond to a first MR image that would have been determined if only a single selected marker region had been generated at the first time point. The different combination MR images correspond to different PLDs.

[0066] A very similar process is described in US patent US 8,610,433 B2.

[0067] In (Günther 2007), it is proposed to combine individual subboli (marking areas) into longer, so-called virtual subboli. This is because the sum of several subboli can be used to generate any desired longer virtual subbolus, and the distance to the image readout, the PLD, can also be varied. In practice, all reconstructed MR images belonging to the individual subboli are first reconstructed from the measured MR images. These are then added in a further reconstruction step to form doubly reconstructed MR images, so that the subboli belonging to the reconstructed MR images form virtual subboli belonging to the doubly reconstructed MR images.

[0068] In an exemplary implementation of (Guenther 2012), N-1 reconstructed MR images can be generated from N measured MR images, and to generate each of these N-1 reconstructed MR images, all N measured MR images are required. Using the N-1 reconstructed MR images, an MR signal can be determined for different PLDs, and thus the signal course over time can be determined voxel-by-pixel. From these signal-time curves, various parameters relevant for clinical diagnosis can then be determined voxel-by-pixel. This and other aspects are explicitly discussed in (Günther 2007), Dai, W., Shankaranarayanan, A. & Alsop, DC, 2013. Volumetric measurement of perfusion and arterial transit delay using hadamard encoded continuous arterial spin labeling. Magnetic resonance in medicine, 69(4), pp.1014-22 and Teeuwisse, WM et al., 2014. Time-encoded pseudocontinuous arterial spin labeling: Basic properties and timing strategies for human applications.Magnetic resonance in medicine described.

[0069] In the claims, the words “comprise” and “comprising” do not exclude other elements or steps, and the indefinite article “a” does not exclude a plurality.

[0070] A single unit or device can perform the functions of multiple elements listed in the claims. The fact that individual functions and elements are listed in different dependent claims does not mean that a combination of these functions or elements could not also be used to advantage.

[0071] The control of the MR system and / or the evaluation system according to the MR method or the evaluation method can be implemented as program code of a computer program and / or as corresponding hardware.

[0072] A computer program may be stored and / or distributed on a suitable medium, such as an optical storage medium or a solid-state storage medium, distributed with or as part of other hardware. The computer program may also be distributed in other forms, for example, via the Internet or other telecommunications systems.

[0073] The reference signs in the claims are not to be understood as limiting the subject matter and scope of protection of the claims by these reference signs.

Claims

[1] Magnetic resonance system for generating magnetic resonance data of a flowing fluid, the magnetic resonance system (1) comprising: - a data acquisition unit (5) for acquiring first magnetic resonance data, wherein the data acquisition unit (5) is adapted to carry out a plurality of magnetic resonance measurements, wherein in each magnetic resonance measurement first magnetic resonance data are measured by a) at different first times in a first region, the fluid is either magnetically marked or not marked to produce a flowing sequence (10) of marking and / or non-marking regions (L, C), and b) at a second time in a second region at which the fluid flows from the first region, the first magnetic resonance data indicative of the generated sequence (10) of marking and / or non-marking regions (L, C) are measured, - an evaluation unit (7) for evaluating the first magnetic resonance data measured in the various magnetic resonance measurements, wherein the evaluation unit (7) is adapted, based on a combination of the first magnetic resonance data measured in the various magnetic resonance measurements, to determine second magnetic resonance data which are each indicative of a combination marking region composed of a plurality of marking regions generated at different first times and flowed to the second region and a time interval between one of the first times and the second time, wherein the evaluation unit (7) is further adapted to determine second magnetic resonance data, each of which is indicative of a marking region generated at a specific first point in time and flowed to the second region, based on a combination of the first magnetic resonance data measured in the various magnetic resonance measurements, wherein the evaluation unit (7) is adapted such that, for determining the second magnetic resonance data, which are each indicative of a combination marking region composed of a plurality of marking regions generated at different first times and flowed to the second region, and a time interval between one of the first times and one of the second times, based on a combination of the first magnetic resonance data measured in the various magnetic resonance measurements, fewer first magnetic resonance data are combined than for determining the second magnetic resonance data, which are each indicative of a marking region generated at a specific first time and flowed to the second region. [2] Magnetic resonance system according to claim 1, characterized bythat the magnetic resonance system (1) further comprises a matrix provision unit (6) for providing a two-valued determination matrix, wherein the two-valued determination matrix has only two values ​​representing marking and non-marking regions, wherein a row of the determination matrix represents a sequence (10) of marking and / or non-marking regions (L, C) and wherein different rows of the determination matrix correspond to different magnetic resonance measurements, wherein the evaluation unit (7) is adapted, - to form a vector, wherein a vector element is formed by a magnetic resonance value of the first magnetic resonance data and different vector elements correspond to different magnetic resonance measurements, - to invert the determination matrix, and - to determine the second magnetic resonance data by applying the inverted determination matrix to the vector. [3] Magnetic resonance system according to one of the preceding claims, characterized by that for each sequence (10) of marking and / or non-marking areas (L, C) there is a complementary sequence. [4] Magnetic resonance system according to claim 3, characterized by that the data acquisition unit (5) is adapted to carry out magnetic resonance measurements having complementary sequences (10) immediately one after the other. [5] Magnetic resonance system according to claim 4, characterized bythat the magnetic resonance system (1) further comprises a matrix providing unit (6) for providing a two-valued first determination matrix, wherein the two-valued first determination matrix has only two values ​​representing marking and non-marking regions, wherein the rows of the first determination matrix represent a first group of sequences (10) of marking and / or non-marking regions (L, C), and wherein different rows of the first determination matrix correspond to different magnetic resonance measurements, wherein the matrix providing unit (6) is further adapted to provide a two-valued second determination matrix, wherein the two-valued second determination matrix has only two values ​​representing marking and non-marking regions, wherein the rows of the second determination matrix represent a second group of sequences (10) of marking and / or non-marking regions (L, C),which are complementary to the sequences of the first group, and wherein different rows of the second determination matrix correspond to different magnetic resonance measurements, wherein the evaluation unit (7) is adapted, - to form a first vector, wherein a vector element of the first vector is formed by a magnetic resonance value of the first magnetic resonance data and different vector elements of the first vector correspond to different magnetic resonance measurements, which in turn correspond to different sequences of the first group, - to form a second vector, wherein a vector element of the second vector is formed by a magnetic resonance value of the first magnetic resonance data and different vector elements of the second vector correspond to different magnetic resonance measurements, which in turn correspond to different sequences of the second group, - invert the first determination matrix and the second determination matrix, and - to determine the second magnetic resonance data by applying the inverted first determination matrix to the first vector and the inverted second determination matrix to the second vector. [6] Magnetic resonance system according to one of the preceding claims, characterized by that the data acquisition unit (5) is adapted to carry out magnetic resonance measurements sequentially in time according to the number of changes between marking and non-marking areas in the corresponding sequence (10). [7] Magnetic resonance system according to one of the preceding claims, characterized by in that the evaluation unit (7) is adapted to determine addition and / or subtraction data by adding and / or subtracting first magnetic resonance data measured in different magnetic resonance measurements from one another, and to determine the second magnetic resonance data based on the addition and / or subtraction data. [8] Evaluation system for evaluating magnetic resonance data of a flowing fluid, the evaluation system (20) comprising: - a data providing unit (21) for providing first magnetic resonance data, wherein the data providing unit is adapted to provide first magnetic resonance data of a plurality of magnetic resonance measurements, wherein in each magnetic resonance measurement first magnetic resonance data were measured by a) at different first times in a first region, the fluid was either magnetically marked or unmarked to produce a flowing sequence (10) of marking and / or non-marking regions (L, C), and b) at a second time in a second region at which the fluid flows from the first region, the first magnetic resonance data indicative of the generated sequence (10) of marking and / or non-marking regions (L, C) were measured, - an evaluation unit (22) for evaluating the first magnetic resonance data measured in the various magnetic resonance measurements, wherein the evaluation unit (22) is adapted to determine second magnetic resonance data which are each indicative of a combination marking region composed of a plurality of marking regions generated at different first points in time and flowed to the second region and a time interval between one of the first points in time and the second point in time, based on a combination of the first magnetic resonance data measured in the various magnetic resonance measurements wherein the evaluation unit (7) is further adapted to determine second magnetic resonance data, each of which is indicative of a marking region generated at a specific first point in time and flowed to the second region, based on a combination of the first magnetic resonance data measured in the various magnetic resonance measurements, wherein the evaluation unit (7) is adapted such that, in order to determine the second magnetic resonance data, which are each indicative of a combination marking region composed of a plurality of marking regions generated at different first points in time and flowed to the second region, and a time interval between one of the first points in time and one of the second points in time, based on a combination of the first magnetic resonance data measured in the various magnetic resonance measurements, fewer first magnetic resonance data are combined than for determining the second magnetic resonance data, which are each indicative of a marking region generated at a specific first point in time and flowed to the second region. [9] A magnetic resonance method for generating magnetic resonance data of a flowing fluid, the magnetic resonance method comprising: - Acquiring first magnetic resonance data, wherein a plurality of magnetic resonance measurements are carried out and wherein in each magnetic resonance measurement first magnetic resonance data are measured by a) at different first times in a first region, the fluid is either magnetically marked or not marked to produce a flowing sequence (10) of marking and / or non-marking regions (L, C), and b) at a second time at a second location to which the fluid flows from the first region, the first magnetic resonance data indicative of the generated sequence (10) of marking and / or non-marking regions (L, C) are measured, - evaluating the first magnetic resonance data measured in the various magnetic resonance measurements, wherein second magnetic resonance data are determined, each of which is indicative of a combination marking region composed of a plurality of marking regions generated at different first times and flowed to the second region, and a time interval between one of the first times and the second point, based on a combination of the first magnetic resonance data measured in the various magnetic resonance measurements, wherein second magnetic resonance data are determined, each indicative of a marking region generated at a specific first time and flowed to the second region, based on a combination of the first magnetic resonance data measured in the various magnetic resonance measurements, wherein, for determining the second magnetic resonance data, which are each indicative of a combination marking region composed of a plurality of marking regions generated at different first times and flowed to the second region, and a time interval between one of the first times and one of the second times, based on a combination of the first magnetic resonance data measured in the different magnetic resonance measurements, fewer first magnetic resonance data are combined than for determining the second magnetic resonance data, which are each indicative of a marking region generated at a specific first time and flowed to the second region. [10] Evaluation method for evaluating magnetic resonance data of a flowing fluid, the evaluation method comprising: - Providing first magnetic resonance data, wherein first magnetic resonance data of a plurality of magnetic resonance measurements are provided, wherein in each magnetic resonance measurement first magnetic resonance data were measured by a) at different first times in a first region, the fluid was either magnetically marked or unmarked to produce a flowing sequence (10) of marking and / or non-marking regions (L, C), and b) at a second time in a second region at which the fluid flows from the first region, the first magnetic resonance data indicative of the generated sequence (10) of marking and / or non-marking regions (L, C) were measured, - evaluating the first magnetic resonance data measured in the various magnetic resonance measurements, wherein second magnetic resonance data are determined, each of which is indicative of a combination marking region composed of a plurality of marking regions flown to the second region at different first times and a time interval between one of the first times and the second point, based on a combination of the first magnetic resonance data measured in the various magnetic resonance measurements, wherein second magnetic resonance data are determined, each indicative of a marking region generated at a specific first time and flowed to the second region, based on a combination of the first magnetic resonance data measured in the various magnetic resonance measurements, wherein, for determining the second magnetic resonance data, which are each indicative of a combination marking region composed of a plurality of marking regions generated at different first times and flowed to the second region, and a time interval between one of the first times and one of the second times, based on a combination of the first magnetic resonance data measured in the different magnetic resonance measurements, fewer first magnetic resonance data are combined than for determining the second magnetic resonance data, which are each indicative of a marking region generated at a specific first time and flowed to the second region. [11] A computer program for generating magnetic resonance data of a flowing fluid, the computer program comprising program code means which cause the magnetic resonance system according to claim 1 to perform the magnetic resonance method according to claim 9 when the computer program is executed on a computer which controls the magnetic resonance system. [12] Computer program for evaluating magnetic resonance data of a flowing fluid, wherein the computer program comprises program code means which cause the evaluation system according to claim 8 to carry out the evaluation method according to claim 10 when the computer program is executed on a computer which controls the evaluation system.

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