MRI preview

Abstract

Method for reconstructing a preview from magnetic resonance data, wherein the method comprises the following steps: a) Recording of first magnetic resonance data (51) (110), b) Selection of second magnetic resonance data (52) from the first magnetic resonance data (51) (120) and c) Reconstruction of a preview (53) using the second magnetic resonance data (52) (130), wherein immediately after the reconstruction of the preview (53) using the second magnetic resonance data (52) a reconstruction of at least part of the first magnetic resonance data (51) is started.

Description

[0001] The invention relates to a method for reconstructing a preview of a magnetic resonance examination, a magnetic resonance apparatus and a computer program product.

[0002] Magnetic resonance imaging (MRI) is an imaging examination method that is primarily used in medical diagnostics to depict the structure and function of tissues and / or organs in an object under investigation, such as the body of a human or animal patient.

[0003] For this purpose, rapidly switched gradient fields are typically superimposed on a static basic magnetic field in a magnetic resonance scanner. Furthermore, high-frequency pulses (RF pulses) are radiated into the examination subject from a radio-frequency antenna unit of the magnetic resonance scanner, causing a magnetization of at least part of the subject. As a result of the magnetization, magnetic resonance signals are generated, which can be acquired, for example, using local coils and / or a whole-body coil, and converted into magnetic resonance data. Magnetic resonance images can be reconstructed based on the acquired magnetic resonance data.

[0004] Reconstructing the magnetic resonance images from a magnetic resonance examination can be very time-consuming. This is especially the case when iterative reconstruction techniques are used. These are often applied in conjunction with compressed sensing (CS) techniques, for example, to achieve higher temporal resolution in the magnetic resonance images. Since iterative, i.e., step-by-step, reconstruction often requires significant computational effort, long reconstruction times are usually the result, even on today's powerful hardware. Depending on the application, this can take more than ten minutes per magnetic resonance examination. However, an operator, such as a radiology technician (MTRA) or a physician, must decide whether a measurement, especially a measurement slice, is complete and the patient can be discharged, or whether another magnetic resonance examination can be performed.

[0005] US Pat. No. 5,881,728 A discloses a method for producing a contrast-enhanced magnetic resonance image of a subject from NMR data. WO 2015 / 164 761 A1 discloses a retrospective reconstruction of an image of a moving heart.

[0006] The present invention is based on the object of providing a method for reconstructing a preview, which in particular allows the operator to make a timely decision about further action.

[0007] The problem is solved by the features of the independent claims. Advantageous embodiments are described in the subclaims.

[0008] Accordingly, a possible method for reconstructing a preview of a magnetic resonance examination comprises the following steps: First magnetic resonance data are acquired, from which second magnetic resonance data are selected. A preview is reconstructed based on the second magnetic resonance data.

[0009] The selection of the second magnetic resonance data can be performed, in particular, manually by an operator of the magnetic resonance device and / or automatically. For automatic selection, selection criteria are preferably stored, in particular electronically in a memory.

[0010] Preferably, the second magnetic resonance data are a true subset of the first magnetic resonance data, i.e., the first magnetic resonance data comprise more data than the first magnetic resonance data. The first magnetic resonance data preferably comprise all data of the magnetic resonance examination. A magnetic resonance examination comprises, for example, the measurement of a measurement slice.

[0011] When operating the magnetic resonance imaging system, multiple magnetic resonance examinations can be performed on a patient directly one after the other, for example, by measuring multiple slices one after the other. Advantageously, the method according to the invention is repeated for each magnetic resonance examination.

[0012] The preview may include one or more magnetic resonance images. These are preferably displayed to the operator via an output device, such as a monitor.

[0013] In this case, no additional alternative reconstruction is used, possibly even based on specifically acquired magnetic resonance data, to generate a preview for a magnetic resonance examination. This avoids, in particular, the computing time required for any additional alternative reconstruction, which would delay the reconstruction of the initial magnetic resonance data. The preview can therefore be created without significant additional computational effort, and the operator can quickly decide on the next steps based on the preview.

[0014] A compressed sensing technique and / or an iterative reconstruction technique are preferably used for reconstructing the preview. As already explained, a rapid reconstruction of a preview is particularly helpful here, since reconstructing the entire initial magnetic resonance data usually takes a considerable amount of time.

[0015] A compressed sensing technique, sometimes also referred to as compressive sensing or compressive sampling, is a data processing technique that efficiently acquires and reconstructs data by finding solutions to an underdetermined system of linear equations. The search for such solutions can be carried out step by step, which is why iterative reconstruction techniques are particularly suitable.

[0016] Preferably, the preview is used to evaluate the first magnetic resonance data. In particular, the operator can assess whether the acquisition of the first magnetic resonance data was successful. For example, the operator can use the preview to estimate whether any additional images reconstructable from the first magnetic resonance data are also free of artifacts that could, for example, have been caused by patient movement.

[0017] If the initial magnetic resonance data are assessed negatively based on the preview, new initial magnetic resonance data can be acquired. A negative assessment occurs in particular if the preview indicates that the quality of the initial magnetic resonance data is inadequate.

[0018] The measurement process is advantageously repeated so that new first magnetic resonance data are available. This possible repetition can be performed with adjusted acquisition parameters if necessary. The new magnetic resonance data can be processed in the same way as the original first magnetic resonance data, i.e., new second magnetic resonance data can be selected from it, based on which a new preview is reconstructed, and so on. This process can be repeated until, for example, satisfactory first magnetic resonance data are available.

[0019] The method according to the invention preferably provides that if the first magnetic resonance data is evaluated positively based on the preview, no additional magnetic resonance data is acquired. By omitting the acquisition of additional magnetic resonance data, the magnetic resonance device can be operated efficiently. This distinguishes the present invention, in particular, from possible methods in which a pre-scan is initially performed, which primarily or exclusively serves to acquire preview data, for example, to check acquisition parameters and / or an image region. Only then, if the evaluation is positive, is the actual measurement performed.

[0020] In particular, no additional magnetic resonance data from the same body region of the patient is acquired using the same acquisition parameters. This does not, of course, preclude the possibility of performing other examinations on the patient after a positive assessment, for example, by examining a different body region of the patient and / or the same body region using different acquisition parameters. In this case, different initial magnetic resonance data can, of course, be acquired, meaning that the method according to the invention can be started again.

[0021] One embodiment of the method provides that, if the first magnetic resonance data is evaluated positively based on the preview, further images are reconstructed based on at least a portion of the first magnetic resonance data and / or at least a portion of the first magnetic resonance data is provided for a reconstruction of further images.

[0022] If the preview indicates that the acquisition of the first magnetic resonance data was successful, further images are preferably generated based on at least part of the first magnetic resonance data, which images can be used in particular for diagnosis. The further images are preferably not identical to the preview. It is also conceivable that the reconstruction of the further images is only carried out partially or not at all, but that the first magnetic resonance data are provided for a possible later reconstruction. A reconstruction of the further images can therefore also take place subsequently, for example several minutes, in particular several hours, in particular several days after the reconstruction of the preview.

[0023] In any case, a positive assessment ensures that the initial magnetic resonance data acquired are suitable for generating further images, ideally of sufficient quality, and that no new initial magnetic resonance data need to be acquired. This allows, for example, the patient to be discharged as soon as possible and / or the magnetic resonance imaging system to be available for other measurements.

[0024] Preferably, the magnetic resonance data used to reconstruct the additional images and / or intended for reconstructing additional images do not include the second magnetic resonance data. Thus, the additional images are preferably not reconstructed using the entire first magnetic resonance data, but rather only using the first magnetic resonance data minus the second magnetic resonance data. This avoids a potentially unnecessary double reconstruction of the second magnetic resonance data.

[0025] Immediately after the reconstruction of the preview based on the second magnetic resonance data, a reconstruction of at least a part of the first magnetic resonance data is started.

[0026] Preferably, therefore, it is not necessary to wait until any evaluation of the first magnetic resonance data has been performed based on the preview. Instead, the time is used to begin the reconstruction of at least a portion of the first magnetic resonance data in the background. If any evaluation is negative, the results of the first magnetic resonance data reconstructed up to that point are preferably discarded.

[0027] One embodiment of the method provides that a compressed sensing technique and / or an iterative reconstruction technique is and / or can be applied for the reconstruction of the additional images. The preview can achieve a significant efficiency gain here, since compressed sensing techniques and / or iterative reconstruction techniques, as already explained, are often very computationally intensive.

[0028] Preferably, the preview has essentially the same quality, in particular the same spatial and / or temporal resolution and / or the same contrast, as the other images. This advantageously distinguishes this method from other methods that often compromise the quality of the preview in order to accelerate its reconstruction. Preferably, the preview is generated using the same algorithms and / or parameters as the other images.

[0029] Preferably, the preview and the additional images are combined into consolidated images. This preferably creates a common dataset that includes the information from the preview and the additional images. Ideally, the consolidated images include a reconstruction of the entire first magnetic resonance data. The consolidated images are preferably used for diagnosis.

[0030] Especially if the preview and the other images are of essentially the same quality, the preview can easily be displayed together with the other images. Reconstructing the preview is therefore not useless for the subsequent process, as is the case with conventional procedures, where the preview is generally not used further, especially for diagnostic purposes, after evaluation and / or preliminary viewing.

[0031] One embodiment of the method provides for the selection of the second magnetic resonance data to be performed by spatial limitation. In this case, a first measurement volume is preferably acquired using the first magnetic resonance data, and a second measurement volume that is smaller than the first measurement volume is selected from the first measurement volume. In particular, the second measurement volume comprises particularly relevant parts of the first measurement volume, which are preferably particularly suitable for generating a meaningful preview. The limitation can be described, for example, using selection parameters.

[0032] In particular, spatial delimitation involves slice selection. For example, for time-resolved three-dimensional measurements, reconstruction can be decoupled in a third spatial dimension. For this purpose, individual slices can be reconstructed from the center of the measured volume along a time domain and then displayed as a preview with essentially the same image quality as the complete, especially iterative, results.

[0033] Furthermore, it is conceivable that the second magnetic resonance data is selected by a temporal limitation. For example, in a measurement that includes a first period of time during which the first magnetic resonance data were acquired, a second period of time, in particular a point in time, can be selected that is shorter than the first period of time during which the second magnetic resonance data were acquired. The limitation can be described, for example, using selection parameters.

[0034] Furthermore, a magnetic resonance apparatus is proposed that is suitable for carrying out a method according to the invention for reconstructing a preview of a magnetic resonance examination. In particular, the magnetic resonance apparatus is configured to acquire first magnetic resonance data and comprises a selection unit configured to select second magnetic resonance data from the first magnetic resonance data, and a reconstruction unit configured to reconstruct a preview based on the second magnetic resonance data.

[0035] The advantages of the magnetic resonance apparatus according to the invention essentially correspond to the advantages of the method according to the invention for reconstructing a preview based on magnetic resonance data, which are described in detail above. Features, advantages, or alternative embodiments mentioned herein can also be applied to the other claimed subject matter, and vice versa.

[0036] Furthermore, a computer program product is proposed which comprises a program and can be loaded directly into a memory of a programmable processing unit of the magnetic resonance apparatus and has program means, e.g., libraries and auxiliary functions, for executing a method for reconstructing a preview based on magnetic resonance data when the computer program product is executed in the magnetic resonance apparatus. The computer program product can comprise software with source code that still needs to be compiled and linked or that only needs to be interpreted, or executable software code that only needs to be loaded for execution. The computer program product enables the method for reconstructing a preview of a magnetic resonance examination to be executed quickly, identically repeatably, and robustly.The computer program product is configured to perform the method steps according to the invention using the magnetic resonance device. The magnetic resonance device must have the necessary prerequisites, such as a suitable RAM, a suitable graphics card, or a suitable logic unit, so that the respective method steps can be carried out efficiently.

[0037] The computer program product is stored, for example, on a computer-readable medium or on a network or server, from where it can be loaded into the processor. Furthermore, control information of the computer program product can be stored on an electronically readable data carrier. The control information of the electronically readable data carrier can be configured such that, when the data carrier is used, it carries out a method according to the invention. Examples of electronically readable data carriers are a DVD, a magnetic tape, or a USB stick on which electronically readable control information, in particular software, is stored. If this control information is read from the data carrier, all inventive embodiments of the method described above can be carried out. Thus, the invention can also be based on said computer-readable medium and / or said electronically readable data carrier.

[0038] Further advantages, features, and details of the invention will become apparent from the exemplary embodiments described below and from the drawings. Corresponding parts are provided with the same reference numerals in all figures.

[0039] They show: Fig. 1 a magnetic resonance device according to the invention in a schematic representation, Fig. 2 a block diagram of a method according to the invention, Fig. 3 a schematic diagram of magnetic resonance data and images that can be reconstructed from them.

[0040] In Fig. 1 schematically illustrates a magnetic resonance apparatus 10. The magnetic resonance apparatus 10 comprises a magnet unit 11 having a superconducting main magnet 12 for generating a strong and, in particular, temporally constant main magnetic field 13. Furthermore, the magnetic resonance apparatus 10 comprises a patient receiving area 14 for receiving a patient 15. The patient receiving area 14 in the present exemplary embodiment is cylindrical and is surrounded in a circumferential direction by the magnet unit 11. In principle, however, a different design of the patient receiving area 14 is conceivable at any time. The patient 15 can be pushed into the patient receiving area 14 by means of a patient support device 16 of the magnetic resonance apparatus 10. For this purpose, the patient support device 16 comprises a patient table 17 designed to be movable within the patient receiving area 14.

[0041] The magnet unit 11 further comprises a gradient coil unit 18 for generating magnetic field gradients used for spatial encoding during imaging. The gradient coil unit 18 is controlled by a gradient control unit 19 of the magnetic resonance device 10. The magnet unit 11 further comprises a radio-frequency antenna unit 20, which in the present exemplary embodiment is designed as a body coil permanently integrated into the magnetic resonance device 10. The radio-frequency antenna unit 20 is designed to excite atomic nuclei that arise in the main magnetic field 13 generated by the main magnet 12. The radio-frequency antenna unit 20 is controlled by a radio-frequency antenna control unit 21 of the magnetic resonance device 10 and radiates radio-frequency magnetic resonance sequences into an examination room, which is essentially formed by a patient receiving area 14 of the magnetic resonance device 10.The radio frequency antenna unit 20 is further configured to receive magnetic resonance signals which are converted into magnetic resonance data.

[0042] The magnetic resonance apparatus 10 has a system control unit 22 for controlling the main magnet 12, the gradient control unit 19, and the radio-frequency antenna control unit 21. The system control unit 22 centrally controls the magnetic resonance apparatus 10, such as performing a predetermined imaging gradient echo sequence. The system control unit 22 also includes a reconstruction unit 26 for reconstructing magnetic resonance data acquired during the magnetic resonance examination. Furthermore, the system control unit 22 includes a programmable processing unit (not shown here) with a memory into which a program can be loaded to execute a method for reconstructing a preview based on magnetic resonance data.

[0043] Furthermore, the magnetic resonance apparatus 10 comprises a user interface 23 connected to the system control unit 22. Control information such as imaging parameters and reconstructed images, in particular a preview, can be displayed on a display unit 24, for example on at least one monitor, of the user interface 23 for medical personnel. Furthermore, the user interface 23 has an input unit 25, by means of which information and / or parameters can be entered by the medical personnel during a measurement process. In particular, selection parameters for selecting magnetic resonance data can be entered with the aid of the input unit 25 and transmitted to a selection unit 27, which is included in the system control unit 22.

[0044] In Fig. Figure 2 shows a block diagram illustrating an exemplary method according to the invention. In a step 110, first magnetic resonance data are acquired using the magnetic resonance apparatus 10.

[0045] In step 120, second magnetic resonance data are selected from the first magnetic resonance data by means of the selection unit 27. The selection can be supported, for example, by the input unit 25 of the magnetic resonance device 10 through the input of selection parameters. The selection of the second magnetic resonance data can be carried out, in particular, by a spatial limitation, for example, by a slice selection, and / or by a temporal limitation.

[0046] In step 130, a preview is reconstructed based on the second magnetic resonance data. In particular, a compressed sensing technique and / or an iterative reconstruction technique can be used to reconstruct the preview.

[0047] The further steps 140, 150, and 160 are optional. In step 140, an evaluation of the first magnetic resonance data is performed based on the preview. If the evaluation n is negative, new first magnetic resonance data are acquired by repeating step 110. In contrast, if the evaluation p of the first magnetic resonance data is positive, no additional magnetic resonance data is acquired. Instead, if the evaluation p is positive in step 160, further images are reconstructed based on at least a portion of the first magnetic resonance data, and / or the method is terminated in step 150, wherein at least a portion of the first magnetic resonance data is provided for a reconstruction of further images in a possible later step not shown here.

[0048] To begin the reconstruction of the additional images in step 160, it is not necessary to wait for the evaluation in step 140; rather, it can be started directly after the reconstruction of the preview based on the second magnetic resonance data. This is indicated by reference symbol V. In particular, a compressed sensing technique and / or an iterative reconstruction technique are used to reconstruct the additional images in step 160.

[0049] In Fig. 3 shows first magnetic resonance data 51 containing second magnetic resonance data 52 selected in step 120. The second magnetic resonance data 52 are a true subset of the first magnetic resonance data 51.

[0050] In step 130, a preview 53 is reconstructed based on the second magnetic resonance data 52. In step 160, further Fig. reconstructed, with the preview 53 and the further Fig. to consolidated Fig. The preview 53 advantageously has essentially the same quality as the other Fig. on.

[0051] Finally, it should be noted that the methods described in detail above, as well as the acquisition pattern generation unit and magnetic resonance device illustrated, are merely exemplary embodiments that can be modified in a variety of ways by those skilled in the art without departing from the scope of the invention. Furthermore, the use of the indefinite articles "a" or "an" does not exclude the possibility that the respective features may be present in multiple instances. Likewise, the term "unit" does not exclude the possibility that the respective components consist of several interacting subcomponents, which may also be spatially distributed.

Claims

[1] A method for reconstructing a preview based on magnetic resonance data, the method comprising the following steps: a) Acquisition of first magnetic resonance data (51) (110), b) selecting second magnetic resonance data (52) from the first magnetic resonance data (51) (120) and c) reconstructing a preview (53) based on the second magnetic resonance data (52) (130), wherein a reconstruction of at least a portion of the first magnetic resonance data (51) is started directly after the reconstruction of the preview (53) based on the second magnetic resonance data (52). [2] Method according to claim 1, wherein a compressed sensing technique and / or an iterative reconstruction technique is used in the reconstruction of the preview (53). [3] Method according to one of claims 1 or 2, wherein an evaluation of the first magnetic resonance data (51) is carried out (140) based on the preview (53). [4] Method according to claim 3, wherein, in the case of a negative evaluation of the first magnetic resonance data (51) based on the preview (53), new first magnetic resonance data are recorded. [5] Method according to one of claims 3 or 4, wherein if the first magnetic resonance data (51) is evaluated positively based on the preview, recording of additional magnetic resonance data is omitted. [6] Method according to one of claims 3 to 5, wherein, in the case of a positive evaluation of the first magnetic resonance data (51) based on the preview (53), further images (54) are reconstructed (160) based on at least a part of the first magnetic resonance data (51) and / or at least a part of the first magnetic resonance data (51) is provided for a reconstruction of further images (54). [7] Method according to claim 6, wherein the magnetic resonance data on the basis of which the further images (54) are reconstructed and / or which are provided for a reconstruction of further images (54) does not comprise the second magnetic resonance data (52). [8] Method according to one of claims 6 to 7, wherein a compressed sensing technique and / or an iterative reconstruction technique is and / or is applicable in the reconstruction of the further images (54). [9] Method according to one of claims 6 to 8, wherein the preview (53) has a substantially equal quality to the further images (54). [10] Method according to one of claims 6 to 9, wherein the preview (53) and the further images (54) are combined to form consolidated images (55). [11] Method according to one of the preceding claims, wherein the selection of the second magnetic resonance data (52) is carried out by spatial limitation. [12] The method of claim 11, wherein the spatial restriction comprises a layer selection. [13] Method according to one of the preceding claims, wherein the selection of the second magnetic resonance data (52) is carried out by a temporal limitation. [14] Magnetic resonance apparatus (10) which is designed to record first magnetic resonance data (51), comprising a selection unit (27) which is designed to select second magnetic resonance data (52) from the first magnetic resonance data (51) and a reconstruction unit (26) which is designed to reconstruct a preview (53) based on the second magnetic resonance data (52), wherein the magnetic resonance apparatus (10) is designed to carry out a method according to one of claims 2 to 13. [15] Computer program product comprising a program and being loadable directly into a memory of a programmable computing unit of a magnetic resonance apparatus (10), with program means for executing a method according to one of claims 1 to 13 when the program is executed in the computing unit of the magnetic resonance apparatus (10).

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